Build Your Own Subwoofer

Gerard J. Pinzone writes "Here's a page that details the construction of a homebrew subwoofer." Another in a long line of "You can, but should you?" projects.

Comments

Case only.

[Anonymous Coward]

He only built the enclosure ... I was expecting a 50Mb AVI of the guy winding the coil and magnetising the magnets.

Re:Case only.

[DetrimentalFiend]

I too was dissapointed. I thought he would at LEAST mangle some existing sub to make it 40" or something crazy like that.

Re:Case only.

[Syre]

He didn't even build a good case, as far as can be told by that article. Maybe a good looking case, but if he didn't design the cabinet using simulation software, it's very unlikely that it's a good sounding case.

In case you're thinking of a similar project, a good page with all kinds of information and links for designing and building your own subwoofers that actually sound good is here.

Here is a page of freeware loudspeaker design software and links to more. And another such page of speaker design software is here.

Re:Case only.

[Grab]

Yeah, I mean big &£$%ing deal. "Wow, this man can use a saw and wood glue, he must be some kind of god." Yeah right...

I made my own speakers at uni - total cost around £80 for a set of kick-ass 50W/side speakers (10" woofer). I used a freeware program to work out the speaker size and the port length to get them working. I've never been able to push them up to the limit, even outdoors! :-) At the same time, my friend built a sub-woofer, including making his own power amp for it with the roll-off frequency settable. At no point did either of us think we'd done anything special, worth publicising to the world as a major achievement.

Grab.

Amazing!

[dotgod]

I used a router to cut all of the circles

I just want to see how he hacked a router to do that.

Kidding...I'm not that much of a geek.

Re:Amazing!

[superpeach]

Why, in England, is router said as root-er (the networky kind) and a router (the cutting kind) is said as, um, row-ter (where 'row' is the kind of thing you may have with your girlfriend/wife, not like the boat, which you row) - the way Americans say router (the networky kind). Who was it that came up with the idea to make written english so bloody (read: 'damn') confusing?

Re:Amazing!

[gmhowell]

You need to turn of the SG-1 and turn on New Yankee Workshop. This is a trivial task.

Remove baseplate on router. Get plank a little longer than the radius of the hole you want to cut. Bolt to bottom of router using baseplate holes. Measure from center of router bit along plank. Drill hole through plank. Place this hole over center of hole you want to cut. Cut another hole, using plank as guide. Place bolt through plank and piece to be cut. Turn on router, swivel around bolt.

Voila! You have cut a hole with a router.

FWIW, I prefer the guy who uses the antique and archaic handtools over norm's "I have a $20,000 tool for just one job" manner. But Norm does have some neat tricks.

Re:Amazing!

[Flerg]

I hear that Norm is using electric stain nowadays . . .

Re:Amazing!

[perlyking]

I wasnt aware of that, I prounounce both as root-er and I thought most people in the country did, perhaps it varies by region or something.

Re:Amazing!

[Ed Avis]

I think one of them routes and the other one routs. But when you stick -er on the end the written difference disappears.

There's a similar question with -ing, which has led some British publications to distinguish between 'routeing' and 'routing', but most people just write routing for both.

Re:Amazing!

[Golias]

Both the networky thing and the cutting thing are called "routers" because the make "routes". If people where you come from pronouce route as "root", then they should both be pronounced "rooter". If your dialect says route as "rowt" (as mine does), then they are both pronounced "rowter".

BTW: Do you say "pronounce" like "pronoonce", too? :P

Re:Amazing!

[Golias]

I know what you mean. Watching that damned show makes me think I need to run out and buy one of those big belt sanders that can do a whole door at once. Eventually, I come around to remember that it would be cheaper to hire somebody to sand my door by hand at $50/hour. Still, his show is fun to watch, and half of the pleasure comes from doing interesting woodwork vicariously through Norm.

home made.

[DarkHelmet]

Ooooh, for a moment when they said "Build your own subwoofer," I thought they meant out of spare parts at home.

I would have loved to see him try to build one out of parts of a microwave, stove, dishwasher, and drying machine while using a fridge to house it.

See what happens when you have old episodes of MacGyver on tape?

Re:home made.

[mrmag00]

bah, MacGyver would have done it with 2 rubber bands in a pencil. I pity your lack of cunningness.

They really are good

[YahoKa]

They are pretty simple to build and for $80 you can have a subwoofer that will make your whole body shake. I've seen it done.

Re:They really are good

[tux-sucks]

For $80 I can buy a subwoofer.

how is this news?

[dcstimm]

How is this news? I like the article on how to do it, but I people have been building subs for a long long time. You can go to radioshack and buy everything you need to build a good sub. Optimus is not the greatest but Im sure you can get the encloserment and then go to a good speaker shop to buy a 12" sub speaker. Plus the 4 gage wire and blah blah blah.

Oh well. Cool article!

Re:how is this news?

[EastCoastSurfer]

I agree about the how is this news part. Building enclosures is nothing new and by itself isn't terribly interesting. Now an article on how someone fit some obscene amount of subs into a tiny foreign car would have been much more interesting. I still remember running the numbers to see if we could fit 4 12inch subs in my friends nissan 240sx back when I was into that kind of stuff :)

Re:how is this news?

[Gordonjcp]

I used to have a 15" foldback wedge (those triangular speakers along the front of the stage) in the back of a Volvo 340. Lots of bass, without that subwoofer "whuff" that you always get. I hate that sound, where you get decent bass down to about 200Hz, then nothing, then a big peak about 40Hz. Instead of nice clean bass you get this "wumf wumf wumf" noise. It's shit, don't do it.

Re:how is this news?

[Darby]

I still remember running the numbers to see if we could fit 4 12inch subs in my friends nissan 240sx

Could, or should?

I saw a picture in car audio magazine one time of a honda accord (old style) that had somewhere around 30 18" woofers in the back.
He just had 4 or 5 big sheets of plywood with as many woofers as he could fit screwed in to it. no boxes, and the back of the car wasn't even sealed.
It must have sounded like complete crap, but it was possible to fit them.

Re:how is this news?

[EastCoastSurfer]

Could, or should?

Could as in properly sealed with dividers between each speaker space (speaker boxes with no dividers is a big no-no), and that each 12 had the proper amount of air space. IIRC we went with 4 JL 12w5s because they would work well with 1.5 cubic feet of sealed enclosure air space. To help make sure the air space was sealed screws were placed every 2 inches to hold the box together with a bead of silicon between the joints and then another bead along the inside of the box at the seams. We managed to fit all of this monster into the back of the 240sx without losing the back seat.

Overall an enclosure of this type is not hard to build, but building it inside the hatchback of a car is a PITA. Lets not even get started on what it took to get amplified sound to each speaker... ;-)

On a side note, it surprises me that more geeks aren't into screwing around with car stereo. There is math, electronics, wiring, music, etc... all in one place. Sounds like something that would be right up many geeks alleys.

Not a Subwoofer

[iamjim]

This is some guys expierence making an ENCLOSURE. I got excited, wrapping a cone w/ wire, finding a good permenant magnet. NOPE - This is something that MANY MANY people have done. It is making a subwoofer that would be the challenge. Then again, making a proper enclosure isn't easy...

Next time get the title of the article right!

Re:Not a Subwoofer

[Mononoke]

I got excited, wrapping a cone w/ wire, finding a good permenant magnet.

That's the driver. I believe he is talking about making a subwoofer, which would imply the use of the device at lower frequency ranges of human hearing.

A driver, no matter what size it is, is not a subwoofer. Subwoofers can be made with a single 12" driver, with four 18" drivers, or even a 30" driver.

No, he doesn't tell you how to make a driver.

Re:Not a Subwoofer

[Mononoke]

There are a ton of free space drivers that are "subwoofers" and do not require any sort of enclosure.

Bullshit. There is not a "free space" driver anywhere that audibly reproduces any frequency below 300Hz.

Prove me wrong. Try linking to an actually product.

Re:Not a Subwoofer

[Angry Black Man]

Oh man, you're a complete idiot. A subwoofer _is_ the driver.

No, the WOOFER is the driver. The entire unit, driver+enclosure, is referred to as a subwoofer.

Re:Not a Subwoofer

[Sound Thinker]

There are quite a number of claims being made here by people who are good at reading spec sheets but not so good at interpereting them.

When you see a driver that is rated for a certain frequency range, the rating assumes that the driver is properly mounted in a cabinet (enclosure) of an appropriate size (if it isn't big enough, the pressure of the enclosed air will act to limit the ability of the driver cone to move back and forth)

When a driver is suspended in free space, the sound waves coming off the back of the driver can cancel the sound waves coming off the from of the driver surface. This is not such a problem at high frequencies, because the sound waves are not long enough to cause any significant cancellation.

I agree with the poster who said that no free-air driver will produce any significant responce below around 300Hz- this corresponds to a wavelength of just over three feet. Even an 18" driver hanging in free air will have its front and back waves concel at lower frequencies. You will get some response, but it will have dropped off dramatically by that point.

Re:Not a Subwoofer

[DavittJPotter]

Actually, no. You're right - it is a driver - but a subwoofer is generally accepted to be a driver 10" or more in diameter, playing frequencies from 80Hz down. The enclosure design denotes the type of bass you'll attain: bandpass, sealed, vented, etc.

Re:Not a Subwoofer

[adolf]

A driver (typically a coil, cone, suspension, and magnet) is not a subwoofer. An enclosure (typically a pile of lumber, some screws or expensive clamps, a bunch of glue) is also not a subwoofer.

Putting both of them together may make a "subwoofer", if things end up wired appropriately, but neither a box nor a driver is very useful by itself. It's like having a CPU without a motherboard or any other requisite component, and calling it a "computer".

Next time, try to posess even a modest understanding of the topic before flaming the submitter/editor/whoever.

Your mention that making a proper enclosure isn't easy is quite possibly the understatement of the century. The moving parts (drivers) of a completed loudspeaker assembly generally only account for ~10% of the final retail cost - and you're lucky if they spend even that much on it. The rest goes toward crossover parts (if needed), hardware like fancy gold-plated terminals, paying someone to solder it all together, and, mostly, a quality cabinet to put it all in.

The cabinet is primarily responsible for making the speakers at your local high-end shop sound better than those sold by your friendly neighborhood appliance whore. It is big, expensive to build, and expensive to ship.

The selection of design and materials is a very non-trivial exercise. Not surprisingly, the more difficult, time-consuming, and heavy designs tend to work better. More expensive materials (think Corian, granite, or good MDF, versus OSB) tend to sound better. Good engineering early on in the project can yield a shift toward zero for all of these variables, but everyone here knows that good engineering is similarly non-free.

And speaking of engineering, it takes a lot of it to build a good driver from scratch. Common practise is geared more toward modifying an existing sample to do more of what you want, instead of building new. The variables are numerous, the parts non-obvious, and the mathematical predictions for what-does-what lacking. But if you really want to know about it, a good place to start might be back-issues of Voice Coil Magazine.

Re:Not a Subwoofer

[LordKronos]

Sorry, but you are wrong. They are 2 separate types of driver, and neither has anything to do with an enclosure. Woofers are tuned to better handle midbass and lower midrange frequencies at the expense of very low frequencies. Subwoofers are tuned to handle very low frequencies much better but are less adept at higher frequencies. Its normal to see woofers with optimal response ranges of 50 or 80Hz up to 1 or 2 KHz. Subwoofers on the other hand typically have optimal ranges from 20Hz up to 120 to 300Hz.

Re:Not a Subwoofer

[LordKronos]

That's not really what the poster was talking about. "Free air" is a term that is used (more commonly in the car audio market) to refer to infinite baffle installations. In this case, there is a wall or other divider between the front and back of the speaker, so you don't get sound wave cancellation at low frequencies. However, there is no traditional box supporting the speaker. For all practical purposes, the mechanical contribution of the "enclosure" is nonexistant. There is no air pressure difference to act as a spring or anything like that.

Re:Not a Subwoofer

[Mononoke]

But anyway, I'll indulge you quickly; I'll only post a couple links since apparently all I have to prove is that there is one driver that will work (there are many, many free-space drivers that go well below 300 Hz by the way):

Every link you posted discusses drivers mounted in enclosures, where the driver/enclosure combination response measurements are stated. There are no response measurements of any drivers only, because they'd be meaningless. Drivers without enclosures (or at least a baffle of some kind) cannot reproduce wavelengths longer than the diameter of the driver.

Re:Not a Subwoofer

[Mononoke]

Why are we bothering to argue with a bunch of kids who have absolutely no knowledge of the physics of acoustics?

Let these folks waste their money on the "experts" at the local auto sound shop.

Re:Not a Subwoofer

[Mononoke]

Wrong. No matter the size of the driver, it will still produce pressure waves all the way down to zero frequency. The diameter of the driver simply defines the "cutoff" frequency (which is a bit of a misnomer because it incorrectly implies that there is no response below a certain frequency). In reality, with a conventional cone driver there is a first-order dropoff in output response below the cutoff, that is the rolloff is about 10dB/decade, and the cutoff itself is usually defined by the half-power (-3dB) point.

Let's look at the physical motion of the driver cone: On the positive slope of a sine wave the cone is pushed out away from the magnet by the voice coil. That motion creates a high-pressure area in front of the cone. Simultaneously, a low-pressure area is created behind the cone. At wavelengths longer than the cone diameter an audible (or measurable) sound wave cannot be created due to the pressure equalizing between the front and rear of the cone.

So, if the cutoff for a given driver is 300Hz, that means that at 300Hz the driver's output is 3dB down from its plateau, at 30Hz, it's 13dB down, and at 3Hz it's 23dB down. In almost any subwoofer you make/buy, the driver is operating entirely in its cutoff region.

First time I've ever heard it described in "decades." In the business of professional audio 'octaves' are the units typically used.

Trust me, the dropoff is much more rapid than you've described. More like 12dB/octave or more.

I was gonna quote more, but as read back over it I realized that it's more marketingspeak than actual scientific theory. You don't sell directional audio cables, do you?

Now, it is possible to create a usable subwoofer without an enclosure. You still have to compensate for the rolloff response of the driver operating below its cutoff, but instead of tuning pressure waves, you perform the tuning electronically so that the frequency response of the driver's input signal is the opposite of the driver's response. The reason why you hardly ever see this approach used is because the power requirements are much greater.

No, it is not possible to creat a useable subwoofer without at least the presence of a baffle.

The reason you never see your approach (trying to alter physics with electronics) is that:

1. The driver needs some kind of back-loading to keep the voice coil from being pushed out of the gap.
2. Any energy you force into the driver that it can't turn into acoustical energy gets turned into heat.

One thing everyone seems to be missing in this discussion is that driver specifications are based on a driver mounted in a large baffle and measured in an anechoic chamber.

Lacking a bit..

[nukey56]

I was hoping this would talk a little more about the mechanical aspects of building the actual driver, instead of being mostly a guide to fitting a sub into a box. Or am I just missing something?

Re:Lacking a bit..

[Mononoke]

I was hoping this would talk a little more about the mechanical aspects of building the actual driver, instead of being mostly a guide to fitting a sub into a box. Or am I just missing something?

Yes, you are missing something. A driver is not a subwoofer. I have 12" drivers in subwoofers. I have 15" drivers that are not in subwoofers.

A subwoofer is a combination of driver and enclosure designed for greatest efficiency and flattest frequency response at frequencies from 80Hz on down.

Another article

[sagi]

Here's another guide for building your own subwoofer.

Re:Another article

[sagi]

Sorry - the correct URL.

Check out Hometheaterforum.com

[sdo1]

The DIY section on HTF is filled with people doing DIY subs.

The DIY section on avsforum also has some info.

DIY subwoofers is another place to start.

In fact a google search yields about 16,000 results with the words "DIY" and "subwoofer".

Which brings me to...

Is this really news?

-S

Re:Check out Hometheaterforum.com

[TeknoDragon]

nope, not news... how about something at least 5 years old? like making a tactile-transducer to strap to your lay-z-boy, make those quake/ut2k3 rockets really hit
http://www.hometheaterhifi.com/volume_4_2/tac tile. html

or my current fav design (for no particular reason, other than it looks cool), the passive reflex enclosure
http://www.diysubwoofers.org/prd/

Subwoofers are a cool DIY project

[Snarfangel]

Subwoofers are one of the few things that home audio do-it-yourselfers can build that is at least somewhat cost-effective in terms of material, effort, and result (well, maybe planar ribbon loudspeakers, though the lines of magnets might be a bit of a pain). Put a nice, massive driver and bandpass filter into a well-dampened box of appropriate volume and spousal approval and you'll have something that not only adds to the depth of music, but will also give you a martini "shaken, not stirred" during your James Bond movie marathon. :)

you know

[Squarewav]

its not that uncommon to build your own stereo equipment, people have been doing it for as long as there was stereos. In fact most car stereo junkies I know of build their own speaker boxes as it is much cheaper then paying someone else to do it and chances are will look better as it matches the look of your car. Had the guy made his own speaker I would be impressed

this is news?

[io333]

It must be a rediculously slow day for geek news.

For More Homebrew Goodness...

[DonnarsHmr]

There is a strong and thriving community of DIY audio enthusiasts. I myself built my own tube preamp, interconnects, and power amp. Try http://www.speakerbuilding.com/ for information about building speakers. For broader information, go to http://www.stereophile.com and click on "Links 2 Die 4" (the l337-ness is theirs, not mine) and then on the DIY link.

YES, you should

[MissMyNewton]

Every 16 year old with a ride builds his own for his car. You know... boooommm boom boom boom boooommmm

If they can, you can too. (And if you *can't*, please turn in your geek badge right now ;-))

Besides, your (legal, of course) MP3s and Quake III Arena will sound much better with one!

Re:YES, you should

[Sleepy]

>Besides, your (legal, of course) MP3s and Quake III Arena will sound much better with one!

How well does it work with il-legal MP3's? Has anyone tested this??

Not too detailed...

[cei]

Sure, it's great that the guy documented his project so others could replicate it, but it might be more useful if he mentioned how he calculated the optimal port length. Specs on resonance frequency, Vas, power handling, and other things might be nice as well. Or why he chose a ported sub rather than an isobaric or sealed design or something else. Not that there's a correct choice, but knowing a little bit about how and why he made his decisions might help others down the line.

Re:Not too detailed...

[miffo.swe]

What about real hornes?

Sure they are a pain in the ass to calculate and not many is up to the task but built right it hurts to listen to them. The punch you get out of a quarts wave pipes (simplest horns) is pretty amazing.

I think the reason hornes arent that popular is that they are hard to calculate and very difficult to build. Take the time and you have a speaker that blows most others away.

Score -1, clueless

[Anonymous Coward]

People have been doing this for a long time (Building ENCLOSURES, not subwoofers). All those little bassheads that you see going down the street with civics shaking the windows out of your house do it themselves. It's simple and easy, and most companies that sell subwoofers provide very detailed and specific guides (more than that page) about port length for ported boxes, volume calculations, building materials, construction methods, and countless other things. And boy, MDF is a bitch to work with.. you need a carbide blade for the saws, and screws strip SO easily. Not to mention MDF dust is very carcinogenic (search around google) and smells bad. Expect this thing to stink up wherever you put it for a while. Most of the guides are in PDF format (For car audio) from the major sub manufacturers' sites: www.kicker.com www.rockfordfosgate.com etc Forque (Chester Bochan)

Re:Score -1, clueless

[helmutjd]

I think you're confusing MDF with something else... I've been building MDF enclosures for years.

MDF (medium density fibreboard) is very easy to work with - you can cut it with a standard jigsaw or table saw. I don't know what kind of screws you've been using, but normal wood screws are more than adequate... MDF won't strip your screws any more than plywood would.

And as for the smell... I've never noticed any, other than a slighly woody odor. Most of the boxes I build get carpeted and installed on the same day, and I've never had any complaints.

Building a simple enclosure is as easy as cutting the MDF, fitting it, gluing it, screwing it together, and carpeting it. Adding things like plexiglass windows, etc., is where it gets interesting. :)

Yes!! You should!!!

[Bobartig]

Building a sub is a great project. As a single driver speaker, it requires no crossover, and therefore is relatively easy to design/build. Plus, with some careful planning, you can get amazing results.

I've built a couple Subs based around the Shiva Mk II driver this guy used, along with a 250W plate amplifier from partsexpress, and it is amazing. Easily produces useable bass down to 20 hz in a sealed enclosure (F3 of something like 17.3 hz in a 1.7 cu ft. box, if I remember correctly...). An adire sub kit easily rivals subs in the $1000-$1200 range.

Listening to one of these explains why audiophiles don't like those Sat/sub computer multimedia sets, and tend to call them a "bunch of crap". None of them produce any useable bass below 50-60 hz, and a lot of HT systems are designed such that the sub only STARTS playing from those frequencies down.

Having said that, I don't see why this is front page news on /.

Re:Yes!! You should!!!

[GigsVT]

it requires no crossover

How is that? Do you really want your sub trying to produce 10khz tones?

Re:Yes!! You should!!!

[EastCoastSurfer]

I was thinking the same thing. Maybe the original poster meant no crossover internal in the enclosure?

Re:Yes!! You should!!!

[MakeTheBadManStop!!!]

My take on that was that there is no *internal* crossover. A real subwoofer should have an active crossover before the (dedicated) amp. This pretty much goes for any situation - The one exception may be (but usually isn't) the LFE channel on surround recordings, where the channel only contains low frequency sounds. Most surround preamp/receivers do low-pass filter this channel anyway before sending the signal out, and many active subs have a built in adjustable active crossover (before the included amp, so one could argue that it isn't part of the subwoofer).

Anyway, a proper system design would ensure that your sub would never receive 10KHz tones, and therefore you would be safe from the cone breakup effects, etc..

Re:Yes!! You should!!!

[dohcvtec]

It looks like this enclosure is sort of a "slot-loaded" design. I built one like this about 10 years ago, and this is the way Velodyne and others have been doing it for a long time. Since the woofer is firing towards the floor, with a fixed (calculated) gap between it and the floor, the need for a crossover is reduced. Not eliminated, but reduced. You'd need a higher-order crossover if the woofer was mounted on the front of the enclosure, staring you in the face and beaming those higher frequencies.

Re:Yes!! You should!!!

[suwain_2]

You really should use some capitalization for "partsexpress," I was wondering what a "sex press" might be, and how you could only have part of one. It took me a while to realize that it was PartsExpress. :)

He built a bass tube not a subwoofer!

[Mustang Matt]

That's nothing special is it?
You can buy your own plans for tubes or boxes all over the place.

A subwoofer is the actual speaker which he just popped into place right?

You can even download software to help you download dimensions:
subwoofer enclosure software

Re:He built a bass tube not a subwoofer!

[Mononoke]

A subwoofer is the actual speaker which he just popped into place right?

Wrong. That's the driver. The 'Subwoofer' is the combination of driver and enclosure.

A driver is nothing until you put it in an enclosure.

Good=Loud?

[shoemakc]

There's more to building quality speakers then just mounting drivers in a box: particularly with ported designs. Building a sub with controlled, tight bass is the challenge; anyone can build a deafening "rumble box".

-Chris

Re:Good=Loud?

[rob-fu]

In high school I messed around with this stuff. My metric on how good the bass was depended upon how much I itched my nose -- the vibration made my nose itch uncontrollably. The more itching, the better the bass.

Buy an iSub and sound stix.

[crovira]

given the low price for a system these days and the crap sound you'll get if you do it wrong, buy an iSub and a couple of sound stix at the Apple store and save yourself a couple of years of apologising for the crappy looking cabinets.

Re:Buy an iSub and sound stix.

[foo12]

You're a bit confused: the SoundStix are the two satellites plus the sub. The iSub itself it made to work in conjunction with the built-in speakers on the old, CRT iMacs, the built-in speakers on the eMac, and Apple's add-on, amplified speakers. The industrial design of the subs are the same, but the specs aren't.

What is missing

[divide overflow]

This isn't even a good explanation for how to create a subwoofer enclosure. It is completely missing any information on the critical variables that describe the attributes of the low frequency driver as well as the procedure for designing the enclosure and crossover network to work with the driver to produce an optimized system. You can't just throw any old speaker into a given enclosure and expect a decent result. If you don't design the enclosure around the Thiele-Small parameters for the driver you put in it you are basically throwing the driver into a pretty box and ignoring the most important factors...how the completed system will perform.

And I wouldn't be a good slashdotter if I didn't mention are several computer programs that help with the design of speaker systems. They are really helpful for designing a subwoofer. I used such a program to design the subwoofer in my car.

Re:What is missing

[Chuqmystr]

EXACTLY what I wanted to say. At least he did mention about messing up the port length. Myself being an old school autosound installer in my previous life I've designed MANY of these, somewhere on the order of losing count of just how many. Thiele-Smalls, the construction materials, to port or not to port based on the TS params of the driver, enclosure volume you have to work with and the volume of the vehicles cabin drasticaly affect how it will sound. You also have a lot of room to shape he overall sound, everything from those stupid-assed anoying boom-box systems we all so love *cough* down to a nice tight 'n clean system with the sub just fitting in with the rest of the musical range to cover. Sorry, getting kinda off topic here, just had to toss in my own $.02. Anyway, point is, you realy need to know what you're doing before before just tossing any old speaker in any old box. You may get lucky but most likely you'll be vey dissapointed if you do just try and toss it together without proper design.

Re:What is missing

[Lumpy]

that's because the subwoofer described in the site absolutely sucks... I ran the box plot on it... it is HORRIBLE with a capital H... sure it will sound OK if you jam 20 bajillion watts into it... but any nut can do that (note: 90% of the car stereos you hear are really crappy subwoofers with overpriced drivers and too much power.)

The title of the article needs to be, how to build a homebrew low end subwoofer that will be the same as the $49.95 KLH units at best buy.

Ick..

Commerical cylindrical subs

[rudib]

Well, if you ain't that much of a DIY guy, you can buy such (not actually sonosub, but much sturdier) cylindrical subwoofers from SV subwoofers. The latest PC+ series is already given praise over Home Theater across the web. And the CS Ultra series is... Well... Check for yourself! :)

Oh, and they are an Internet sale only company - you buy subwoofers directly from them, there are no other dealers between you and them.

And I don't own a SVS ... yet ^_^ (and neither do I work for them)

Re:Commerical cylindrical subs

[tang]

I own the 20-39 pci (its 39 inches tall and is tuned to 20hz). The best sub I've owned hands down, it uses little space, since its so tall, and is awesome for home theater, and it's very musical too, altho I tend to keep it turned down pretty low due to my taste in music.
I can recommend one 200%.

nuttin special

[Skal Tura]

There isn't anything special on making a woofer by yourself, first i thought that the dude made the element by himself but naawh... You really don't need much skill to make a subwoofer, just some maths and a little skills to make the casing. If you have proper tools it shouldn't even take long for an experienced woofer builder. With experienced i mean knowing the little tips & tricks to avoid hazzle and problems. tho, that woofer probably sounds nice but there isn't anything special... i wonder where ./ is going with news like this, do they wanna do a news report when i assemble my next woofer? lol Or perhaps some of my other projects like liquid cooling to make cpu run at -15 to -10 celsius degrees, or perhaps mobo box sized server... NOTE TO MODDERS: I didn't want to troll but there simply isn't any idea to report stuff like this, there isn't anything special on making a subwoofer by yourself.

Mislead and then let down by /. yet again!

[Nemith]

When i first read the title to this story, I said to myself, "Wow, some guy actually hacked together some magnets and other supplies and built his own subwoofer!" But it's just an enclosure!

Wow, so what he built his own enclosure. This is common practice in both home and car audio and hardly worth the post on /.

I build an enclosure for 2 subwoofers for my car when I was 16 years old. It's not hard, and there are many MANY pages just like this one out on the web.

Another in a long line of "You can, but should you?" projects.
Well if you can handle power tools, and a couple of simple caculations to get the right enclosure and port size for your subwoofer, then HELL YES! I still have mine in my car that are custom fit, and sounds better than the cheap enclosure i had before. I even used pvc pipe as the ports :P

wow, staggers the mind!

[Meowharishi]

Imagine a beowulf cluster of these!! hooo-yeah baby!! uh uh uh love that pussy!!

Ha! That's nothing!

[Noose For A Neck]

Just take a gander at the king of all subwoofers they made out of an old hard drive motor at MIT!

Wait, but ...

[daTimster]

... where are the Lego guys?

Loudspeaker Design Cookbook by Vance Dickason

[mhesseltine]

I own the 4th and 5th editions of this book, and it has everything you would ever want on enclosure design. You can pick it up from Crutchfield, or I'm sure Amazon, Barnes and Noble, etc. should carry it.

Re:Ha! That's nothing!

[HeyZuess]

Now that is building a subwoofer!!

Might as well build a waveguide

[flyneye]

might as well get 15' of 10" PVC put a 10" woof appr.2/3 the way down(go get specs yourself) and get bass to stir your guts.

Re:Might as well build a waveguide

[GigsVT]

At a couple frequencies.

That tube is only going to resonate at a few frequencies that are harmonics of each other. Yeah, you will hit one certain spot really really hard, but other frequencies will be attenuated.

Re:Might as well build a waveguide

[flyneye]

well yeah,figure up the specs for something around 32hz and throw on bachs toccatta and fugue.bumpin the eq around the freq. you tuned the waveguide to kinda helps.(course most folk would be happy with somethin around 50hz,but hey make it go mooooo)
i got another tuned woof plan that puts a 15" in the top of an openhead drum and tunes by filling drum with water till its where you want it.of course you could split hairs all day but this really is projects for experementation. if you want audiophile go spend the money.

What about free-air subwoofers?

[Mustang Matt]

They have no enclosure!

Regardless, why is this a big deal? I used to build boxes back in high school. They usually sounded awful but not always. Just had to get them sealed up and calculate the dimensions properly.

I had two JL 10W1's that sounded pretty good for a relatively cheap speaker.

Re:What about free-air subwoofers?

[EastCoastSurfer]

They have no enclosure!

Not exactly. Free air subs just don't have to be boxed, but they still need an enclosure. Most of the time these are used in cars and the trunk actually becomes the enclosure.

Re:What about free-air subwoofers?

[dohcvtec]

That would be the infinite baffle configuration. The baffle/mounting plate for the woofer is sized such that the waves from the back of the cone don't reach around to the front of the baffle in time to cancel out the front wave.

moljnir!

[StandardDeviant]

One 26 inch home-brew subwoofer, coming right up!. They built it with the driver from an ancient hard drive. For those not up on Norse mythology, moljnir (several spellings seen) was the unstoppable hammer of the gods, carried by Thor himself. I'd say a building-shaking sub comes pretty close to that description. ;-)

Re:moljnir!

[xtord]

In swedish it's Mjölnir.

Hmmm

[zeno_2]

This is an article on how to build a sub box, not the speaker itself. Many people build their own sub boxes, this is a pretty nice one from what I can see, but its not much different then whats in the trunks of many people across the world today..

You Have Got To Be Kidding Me

[thelizman]

You call this news? Is SlashDot that hard up (or worse, flaccid) that this page worthy of being posted?

There are many fine sites out there with information on building subwoofer enclosures. While the construction of this one was fairly robust and adequate, the design will likely have a very poor response. There are too many no-no's here to cover for a SlashDot comment. Y'all should try some real sites for a start:

1. teamROCS Technical
   
2. The World Famous Eddie Runner and Installer.com's Tech Pages

this is*BOOOOOMMMMM* sweet!

[drik00]

This is *BOOOOOMMMMM*cool cool, I think *BOOOOOMMMMM* i'm gonna try it *BOOOOOMMMMM* for my home *BOOOOOMMMMM* theatre!! The low end *BOOOOOMMMMM* would add a *BOOOOOMMMMM* lot to the experience *BOOOOOMMMMM* .

J *BOOOOOMMMMM*

*BOOOOOMMMMM*

Wouldn't this design inherently suck?

[sakusha]

I'm no acoustic engineer, but it seems you'd have to do some calculations to make sure the resonant cavity matches up to the speaker. I don't see any evidence that he's done any calculations whatsoever. How would you go about determining the optimal size and shape of the cabinet? Or does it not matter on such low freqs?

There is one trick to doing this right

[Dr. Spork]

This guy is obviously a pretty weak hardware hacker. I say "obviously" because if he knew what he were doing, his construction page would be covered with formulas about material desity, air volume, port circumferance, port length, and many other tuning-related issues. It look to me like this guy thought of a design that seemed right a priori, bought a driver, and started cutting. Pathetic!

This has to be the worst Slashdot how-to ever. There is absolutely nothing geeky about doing it blind like this, especially considering how much information is available about doing it the right way. So kids, don't do this at home; do better!

Wouldn't this design inherently suck?

[Anonymous Coward]

What? Do you think this is for listening to MUSIC or something?

Re:Hebrew Subwoofer?

[sinserve]

Arabic is just ONE language, but the arabic writing is used by Farsi and most of the Paki/Afghan languages.

Re: MacGyver

[Metallic Matty]

Ooooh, for a moment when they said "Build your own subwoofer," I thought they meant out of spare parts at home.

Actually, he meant, out of parts taken from another subwoofer...

See what happens when you have old episodes of MacGyver on tape?

MacGyver could break out of a turkish prison with a straw and a toothpick...

I think I'll keep my JBL SB-5

[Openadvocate]

I think I'll keep my JBL SB-5. I can deliver all those sounds that you can't hear but feel. :) A cool device with 4 speakers inside where they are facing eachother 2 by 2 in 3 chambers. PDF tech doc.

I have built subs for my car, but the only problems is that even when you get the sizes calculations right, it just doesn't always sound right. So this time I have settled with a pre-built one, the advantage here was the I tried a few in my car to find the one that sounded right in my car.

Re:I think I'll keep my JBL SB-5

[Levine]

According to that spec sheet of yours, that subwoofer is terrible! I hope you didn't spend a whole lot of money on it, because about all it's good for is impressing people by telling them it has four drivers in it.

Lowest frequency at 45Hz? Are you kidding? Any shoddy, thrown together homebuilt sub can handle at least 35, and ones like this guy has built can hit low 20's and high teens without a lot of effort.

Regards,
levine

Too bad more highschoolers dont read /.

[NeoSkandranon]

about 300 people out of my 1400 member highschool could have gotten alot out of this article..or rather the comments. they all seem to be of the mind that you can throw a pair of 15" subs in a plywood box and throw it in the back of your car, and then they wonder why it sounds like an amplified fart when the bass hits.

Re:Too bad more highschoolers dont read /.

[packeteer]

Well i am in high school and im glad i read this. I am personally not one who wants nothign but earth shattering base so i guess ill look elsware for my DIY sub project. Since i have been looking around for a set of new speakers when i saw the article my heart skipped a beat. Beleive me wheni say i was dissapointed to see nothing about building your own subwoofer at all. There are plenty of classmates of mine who show me their "new car sub" which either sits int he trunk or under the back seat and sounds like muffled cars crashing. Well this is too bad because i am willing to spend t he time to do it right. Are there any better links you know of to teach me?

Acoustic suspension

[Alien Being]

In the 20 or so years that i've been listening to them, subs which use relatively small, high-excursion drivers in a sealed enclosure have been the best, especially for percussion. They need more power, but it's worth it.

Ported subs just don't seem to have the *punch*, and it's tiring to listen to music which has a lot of info near the resonant freq of the port.

I read at +3

[gmhowell]

I read at +3, so I might not have seen a link to this project. Have no idea if it is any good, but it's certainly cheaper than many other options.

(For those not wishing to slashdot OSDN, it's for gspeaker, a gpl software for determining speaker enclosure sizes)

No Frequency Response readout

[TOOSuave]

The whole project is pointless without knowing what kind of frequency response this enclosure will supply. It will most likely be very loose bass looking at the basic setup (Not good for sound quality and not good for accuratly reproducing the sounds created by musical instruments). I would be supprised if the whole thing is really cost effective once you add up the price of the parts+time+block amp. Audio equipment is heavily marked up (Around 250%) But this is probably a hard area to beat the price/performance available in the store.

hmm..

[bo0push3r]

nice looking enclosure. too bad that article has nothing to do with 'building a subwoofer'.

Somethings missing...

[Shirloki]

Blue LEDs! Add some of those and you have a geek worthy article.

Want to build your own sub?..

[matguy]

You're much better off scrapping the whole cone idea and go for a vane/cylinder design. They're much easier to build and often give much better results in a homebrew situation. Try here for some explaination: http://www.mindspring.com/~sdinc/pages/td_new_fam. html

club audio project

[TheSHAD0W]

I may be opening a social club in the not-so-near future. Among the various plans in getting the place up and running, one of the things I'm concerned about is the audio.

I could go the conventional route and just hang a bunch of Peaveys around the place, but I'm also considering using a big subwoofer under the stage and mid/high speakers on the walls and hung from the ceiling instead. I think this might give better audio quality as well as being easier to do -- not to mention safer, wouldn't want those big speakers falling down.

Does anyone have recommendations on such a setup? Are there any subwoofer speakers available that can handle a large space?

Re:Hebrew Subwoofer?

[sinserve]

A subwoofer does not WRITE in Arabic, it _might_ SPEAK in Arabic though. The fact that it speaks
Arabic doesn't it automatically speaks Farsi, Urdu, Pashtu, Punjabi or Sindhy.

You can, but should you?

[Winterblink]

If this is another in a line of "You can, but you should you?" projects, can we get a topic for all of these to go under so I can filter them off the homepage? I'm getting tired of seeing crap like this subwoofer thing, and others like "Here's how I made my kid's jungle gym into a water cooling setup for my Athlon".

Re:Hebrew Subwoofer?

[langed]

I hate to sound like a troll, but I read "Build your own [homebrew] subwoofer."

This is clearly not the case, as it appears some guy just built a tube for it and took pictures.
Big deal; what highschooler hasn't built a sub box or eight?

I was honestly expecting talk of how to wrap the coils for the electromagnet, calculating impedence, how to determine signal sensitivity, locating a sufficiently strong permanent magnet, and preferred choices of cones. Finally, I expected charts of how this sub stacked up against aftermarket subs, in terms of frequency response.

But what is there?

I got the terminal cup and driver from AdireAudio. I used the Shiva II driver and the terminal cup is the 4 post kind that comes with straps for summing the leads if you aren't using an old DPL receiver to power it like I am.

Low and behold, the guy bought the speaker! Build Your Own Subwoofer? I think not.

Who said this was insightful? (Re:What is missing)

[snookerdoodle]

I hate to poo poo someone, but you poo poo'ed the guy's web site. If you use the Shiva driver he did, and build it like he did, YOU DON'T NEED NO STINKING VARIABLES OR CALCULATIONS!

Personally, I preferred the NHT, but "whatever floats yer boat", or, in my case, "whatever shakes yer gutters off the house". And yes, it really did. ;-(

I agree that this is hardly news, but it's not a bad little diy thing, either.

Mark

and acoustic-visions.com

[renehollan]

Kyle Richardson at Acoustic Visions makes custom subwoofers. He made one for me with which I am very satisfied: see here.

Note: I have no affiliation with Acoustic Visions other than a very satisfied customer.

BTW, I am now a nerd for hire. See here if you're looking -- would accept H1B transfer or TN1, preferably in the Dallas area or relo back to Canada.

People in glass houses...

[fmaxwell]

Yes, and a lot (notice how it is two words) of people (including yourself) at your highschool appear to not know correct English.

If you are going to criticize written English, you better be a whole lot more careful. I took the liberty of using boldface to highlight your errors. "It" refers to a single thing and, thus, cannot be "two words." You should have said "notice how 'a lot' is two words". Note that the word "yourself" is boldfaced. The proper word to use there is "you." Would you say "yourself appear to not know correct English"?

While perhaps syntactically correct, "to not know correct English" is clumsy -- to say the least. You should have ended the sentence with something like "to be incapable of writing English correctly."

Ignoring your poor sentence construction and grammatical mistakes, you reasoning is flawed. You claim that "a lot" of people from his high school write poorly, yet you have only read his writing. You have no way to know how the other students write.

Still feeling cocky?

Re:People in glass houses...

[Galvatron]

"appear to not know correct English" isn't just clumsy, it contains a split infinitive. Granted, ever since Star Trek ("to boldly go"), split infinitives aren't as frowned upon as they once were, but it's still wrong. "Appear not to know correct English" would be better, though as you say, still a tad clumsy.

Re:People in glass houses...

[smithmc]

While perhaps syntactically correct, "to not know correct English" is clumsy...

It's not syntactically correct. "To not know" is a split infinitive. (Remember those?)

Re:Hebrew Subwoofer?

[MaxVlast]

You've clearly never used a sophisticated subwoofer with an LCD display.

Gee ...

[Erris]

... thanks for all the destructive criticism. If you knew anything about "material desity, air volume, port circumferance, port length, and many other tuning-related issues." you should say so or point to a page you have that says so, right? If you read the article, you might have noticed how the author points to one of the many useful pages on how to do things "right".

Your post has to be the worst Slashdot troll ever. Wait, I just did the same thing to you! The difference between you and me and the author of the article and slashdot is that the author and Slashdot have put up.

Me, one day I'll spend $60 for a cheap boomer that comes with it's own amp. I applaud the author for doing better.

Re:Gee ...

[Dr. Spork]

I have no problem with people putting loudpeakers into anything. I mean, if you don't want to read up on the math and you have the cash to blow on trial and error, go nuts!

My objection this: Of all the thousands of how-to pages available on the internet, why did this one make it to the front page of Slashdot? A subpoint was that if the guy had discussed his work from a "nerd" angle, it would have made a good /. piece. As it was, I thought it failed as slashdot material, and I still stand by this.

I did indeed notice that the author points to a page where a more careful procedure is explained, and that just makes things worse. Why wasn't that page the subject of the /. article? Still better stuff is available, and I'm sure Google would help you find some of it, but that's not what I would do. When I was designing my speakers I actually (gasp) WENT TO THE LIBRARY! Do people still know how to use these? Anyway, I'd be shocked if there were stuff on the internet that comes close to the quality of what's published in peer-reviewed journals.

In any case, I made my speakers the nerdy way, and that should be the /. way. I don't want this place to degenerate into "news for short-attention-span nerds." For example, if there are speaker how-to's posted, they shouldn't gloss over the very stuff that distinguishes a crappy speaker enclosure from an outstanding one.

This Slashdot Article is rated

[buswolley]

Interesting -1 Informative -1 Insightful-1 Troll -1 Flamebait -1 Funny +1 ---- Still totals: -4 eek Slashdot is becoming the equiv of a dumbed down sesame st or what? I built a hack job box like that when i was in H.S. There are thousands of people designing better amatuer boxes. There are tons of info on the net about acoustics,design theory etc. This article is like what you see in fron of AMPM every graveyard. this article.

Hey .. .

[OverlordQ]

build your own woofer, then put it in your Thunder Table

Dammit . .

[OverlordQ]

should of read the story first.

Argh!

[GrumpyYoYoHead]

Great, just what the world needs, another annoying contraption to piss off the neighbors. Here's an idea, get these new subwoofer earbuds that I've invented and go blow out your own eardrums.

Re:Who said this was insightful? (Re:What is missi

[divide overflow]

I don't consider pointing such things out as "poo-pooing" his site. And you can't even "build the unit like he did" (your words) using the information on his page because he didn't even say *anything* about the *tube* he used to create his unit--the single largest component. Nothing about the diameter, thickness, density, length, or even who makes it. This is rather odd given that he went into PLENTY of detail about certain construction details.

Again, the page didn't provide adequate information to build it the unit, much less determine if it was properly designed.

Building is fun.

[miffo.swe]

My first speaker was a smack horn. The effiency of a horn is much higher than a closed or ported speaker. I got 104 Db at 1 Watt at 1 meter when a normal speaker only makes about 90 Db. Since Decibel is not linear thats a very big difference. Need i to say that it was well worth the hassle? My old Marantz tuner could play the pants of off any mates systems even if it only had 100 Watt output because of the high efficiency of the speakers.

To build a complicated case is more expensive for a speaker manufacturer than to put in a speaker element that handles higher power. For your amplifier its better to have a nicer load.

Go high range!

[Decimal Dave]

Now that you've built your own subwoofer, you can cover the higher audio range with a custom made plasma speaker!

To Boldly Split Infinitives...

[fmaxwell]

It's not syntactically correct. "To not know" is a split infinitive. (Remember those?)

Actually, it is correct. In 1998, the influential New Oxford Dictionary of English admitted that "in standard English the principle of allowing split infinitives is broadly accepted as both normal and useful."

Re:To Boldly Split Infinitives...

[smithmc]

Actually, it is correct. In 1998, the influential New Oxford Dictionary of English admitted that "in standard English the principle of allowing split infinitives is broadly accepted as both normal and useful."

Yet another example of the English language devolving into a pidgin lingua franca. "Normal"? Probably, at least in the US. "Useful"? Why? In what way is splitting an infinitive more "useful" than putting the words in the correct order?

Re:To Boldly Split Infinitives...

[fmaxwell]

Yet another example of the English language devolving into a pidgin lingua franca.

The split infinitive "rule" was invented in the 19th century by classically obsessed scholars who wanted English to be like Latin and Greek (whose one-word infinitives cannot be split). Here's what the Merriam-Webster Dictionary of English Usage says: "The objection to the split infinitive has never had a rational basis."

In what way is splitting an infinitive more "useful" than putting the words in the correct order?

First, either construction is "correct." Second, splitting infinitives often allows one to construct sentences that flow much better. For example, let's take the famous Star Trek opening:

"...to boldly go where no man has gone before."

The linguist David Crystal correctly noted that the original Star Trek television series would have lost something if the mission of the Enterprise had been "boldly to go where no man has gone before." Crystal observed that to boldly go has an iambic, and therefore more natural, rhythm.

Following arbitrary rules concocted by 19th century scholars is not something for which you should take great pride.

BTTF

[Nate Fox]

Anyone else get a mental picture of Michael J Fox turning up knob after knob, and standing in front of a giant speaker?

*sigh* Maybe some DIY stuff should be left alone :)

enclosure, not subwoofer

[austad]

He didn't build the speaker, he built the enclosure for it.

In any case, he used the Shiva II woofer, which I believe is only available without an enclosure, although there are some places making enclosures and selling them with Shiva's already in them. This woofer is around $100 if I remember right, and outperforms many premade commercial products by a longshot. If you know how to use a saw and some basic tools, this woofer is definitely the way to go. I think audioreview.com has some user comments on it, almost all of them positive.

Re:enclosure, not subwoofer

[adolf]

Your statement makes as much sense as the following:

"He didn't build the computer, he built the case for it."

A loudspeaker includes a number of components. A driver, such as the Shiva contraption, is one of them. A box is another.

He assembled these components together. He built a speaker.

Your next statement is similarly non-sensical. I'll convert it to an analog which you might understand:

"...he used the BP-6 motherboard, which I believe is only available seperately, although there are some places building and selling computers with BP-6 motherboards already in them."

Does this statement not disprove itself? Or is there some magic additive which must be included in a loudspeaker/white-box computer before it may be considered as a whole instead the sum of its parts?

Is it a pre-requisite that such finished products carry an endorsement from Apple or Sony before they are recognizably complete systems? Or perhaps some other subtle nuance I've managed to miss in my many years of building complete systems myself?

Please explain further. I fear that if you're correct, my speakers and my computers may suddenly disintegrate themselves into seperate parts.

Re:Ha! That's nothing!

[adolf]

Feh.

An interesting a do-it-yourself project, but can you talk with elephants using it, let alone load it into an Isuzu Trooper?

That seems to have been the going standard for servo-driven loudspeakers for a decade or two.

I had the unique experience of sitting rather directly beside a (somewhat lesser, but similar) dual-cone 15" unit for an evening as I played DJ. I'll spare the details, but do allow me to say that visiting The Throne after returning home that night after having everything homogenized (shaken, not stirred) by the subwoofers was uniquely euphoric experience.

[I'd include more prominent links to Intersonics/Servo-Drive, who still sells these monsters. But their web page is "currently down for reconstruction." Dumb shits. Their old page was at least informative, not to mention existant. groups.google.com for more information, I guess...]

Re:Hebrew Subwoofer?

[smeg168]

I agree completely i was dissapointed, there are tons of 'build your own box' sites out there, damnit i want to build a sub just for the hell of it,
hmm.. well there was that whole useing hard drives as speakers article... maybe a couple of those 5.25 scsi fullheigh platters would make some decent base....

How is this news?

[SCHecklerX]

You can go to any neighborhood radio shack and get a book on doing all of your stereo building. A quick search through online book catalogues will reveal many books on the subject.

Insert foot in mouth

[chemmathguy]

I was always taught that highschool is actually two words, high and school.

How did this get posted?

[mduckworth]

He built the speaker enclosure, big deal. And it's not even finished. Any idiot can build a speaker box, but he didn't even build it a specification for appropriate bass tuning. I thought he was building the driver - much more interesting ;-)

Re: MacGyver

[kasperd]

Actually, he meant, out of parts taken from another subwoofer...

I see the point. But somehow I get the feeling that if you want a subwoofer, there has to be an easier way....

I Am

[LPetrazickis]

What the fuck's a router in mundane-speak?;)

Re:I Am

[nelsonal]

In woodworking a router is a device that is used to cut a channel or groove out of a solid block of wood. You can see some from Craftsman here, they are generally held with the cutting blade down, the cutting blade is in the center of the bottom of the device, and dragged around along your desired line or edge. Its use very similar to the triming of a large whole with a dremel, but designed to leave a better line than I can do with a dremel, there are hundreds of bits to leave various edges.

No spikes?

[divesnob]

The guy didn't even put spikes on for feet. I would love to see this perform on a wood floor. It would be all over the place w/ that flat board as the bass.

Surely not slashdot material!!!

next...

Re:Check out Hometheaterforum.com (slightly OT)

[kilonad]

A google search yields about 105,000 results with the words "DIY" and "linux," so why should this be considered any less newsworthy?

Sure, building your own subwoofer might not be news, and it might not be a new idea, but until Slashdot gets a "really cool stuff that doesn't quite qualify as news but it's still for nerds" section, the front page will have to do.

YES

[Chris Johnson]

Yes, you should build speakers. Building speakers is a terrific geek pastime.

No, this guy's speakers aren't that great.

There are some good points, however. He's doing nothing of note constructionwise, but the larger choice of the sonotube has significant advantages and disadvantages. Big plus: tube shape means walls CANNOT flex from pressure. That allows for potentially thunderous reproduction of the sound coming out, without overhang or weakening of the fundamental. Big minus: the sound coming out is strongly colored by the inside of the enclosure being the second worst possible shape in the universe- worst is a sphere. Testing has shown that these shapes are the best possible for the outside of an enclosure, but the worst for the inside.

What I've found works best for really serious bass is multiple drivers of gradiated sizes. My mains are running 6.5/8/10/12 drivers series-parallel like a Marshall cab- wattage is comparable to four of the weakest speaker (6.5) series-parallel, because that's the one that'd blow first. I have a narrow but absurdly deep cabinet, internal walls, bottom two sections ported and the top two open-backed. I had acoustic foam in there but found that it sounded better in the mids to leave it totally open, since all the resonance and reverberation goes straight out the back. The bottom, with the 10 and 12, has two good-sized ports, but since the box is so big (and it's running acoustic suspension drivers, too) the port only extends the lows further- it is not tuned high enough to make 'one note bass', it's reinforcing the really extreme lows.

If you want a REAL geek audio project, make some supertweeters like I did. Small piezo drivers (I'm using some fairly rigid and tough-to-solder-to ones I got in bulk), mount them on something solid while leaving the middle free to flex (rigid mounting like superglue, not a soft gasket), and then take some envelopes with that clear cellophane stuff that crackles easily if you rumple it. Cut out rectangular pieces big enough that you can make an 'M'- you're going to be making a degradation of the Lineaum cylindrical driver. That requires a piece to translate piezo flex into true linear motion- as shown in the *spit* patent- this skips the bridge piece and applies flexing-disc vibration directly to the leaves of the driver. In doing so it fails to be a proper line source- but the weight of the moving mass is that much less!

Take two 'leaves' and superglue them together at the base. You can trim them a bit so there's a slight ) shape to the part that'll be glued to the piezo. Take a bit of acoustic foam, superglue the outside of the sandwich of cellophane on one side to it, attach it to the speaker to the side of the piezo (which you should have wired up already). Then do the same to the other side- you want a 'm', seen from the top, with the middle bit resting directly on the piezo. The 'm' shouldn't be too tall, but it does have to form full half-cylinders- it shouldn't be flat. Finally, if it's all good, put a dot of superglue on the middle of the piezo, and allow the center of the 'm' to be attached permanently.

How it works: pressure from the piezo displaces the cellophane. Since it's two loose semicylinders, it flexes, choosing to compress together at first rather than shift the whole structure outwards. Surprise! The semicylinders form an exponential horn- and you've just compressed the throat, forcing air out! In addition, the wave will travel outward from the center, until it dissipates by air resistance and eventually the acoustic foam mounting at the far end. This tweeter goes up forever, way beyond CD capabilities, very cleanly, and it also has phenomenal dispersion characteristics- very wide soundfield, virtually no beaming. The difference is not subtle.

In a perfect world, lots of people could work with this technique and develop it as free software is developed. I've seen the patents on the _refined_ version of this- involving a bridge piece between the (not truly linear) driver and the base of the cylinders- and until the patents expire, this is officially proprietary.

I am sure that will dissuade MANY slashdotters from getting cellophane, piezos and superglue, and building their own supertweeters. Don't you people know developing on ideas someone else had is wrong? Remember, whoever-it-was who said, "If I have failed to see farther, it is because I wasn't allowed to stand on anybody's shoulders, so there" ;)

Why have I taken so much effort to communicate this technique? Because I'm a speaker designer myself. I have numerous ideas that are in fact mine, and hybrids of those with things like the Linaeum cylindrical driver, some of which are just terrific. And I'm very annoyed by a reality in which I cannot function as a simple artisan and idea-haver, without patent-wrestling with corporations- and in which I can't even go ahead with my own stuff, as corporations will take anything that's really good, and patent it since I won't, possibly even stopping me from using something I've invented. It makes you want to hide and never build anything.

There's nothing to do but go ahead anyway, but understand that my 'outing' of a homebrew way to do a degraded form of the Lineaum piezo driver patent is a combination of 'power to the people' and simple bitterness. What would have happened if the person to make the first cone driver had locked it up with patents, filed extensions, retained control of it to the present day? There'd be virtually no speakers, is what.

I feel the ideas that MOST deserve patent protection are the ones that most harm the scientific environment through their being guarded by lawyers. 'swinging sideways on a swing' patents are harmless. The ones that are REALLY GOOD are the ones that NEED to disseminate out into society.

....which only goes to show that I need to be using more of my paid-for web space to publicize the work that _I_ do, with no hope of recompense, ever, just to remain true to the principles I've set out. Other people do that- it's not unique to do so. It's merely taking sides, knowingly or unknowingly.

Re:YES

[inode_buddha]

Excellent commentary, I saved it permanently. I'm not so much interested in doing a sub myself, but I have owned horn enclosures powered by tube amps (aka "valves") in the past... and I wouldn't mind building another set of them. I can seriously recommend such a setup, perhaps with an "active" sub for truly crisp and clean audio. I've got to go find some links for that stuff... Klipsch or Altec come to mind, but I don't have that kind of spare cash anymore, bummer. I do have enough time and know-how to design and build though...

sub

[Fiddler]

sonosubs are very popular in DIY home-theater circles. I built one myself and it's not that difficult at all. Sounds awesome and easily rivals subs that are over $2k +

Re:Check out Hometheaterforum.com (slightly OT)

[spoco2]

But it's not even a particularly new/clever/well presented/information rich example of a sub woofer either... the same type of sub design has been shown many, many times before... so why was this one posted on Slashdot?

Homemade Shiva-based subwoofer

[beb]

I spent WAY to many hours reading up on homemade subwoofer construction for my home A/V system, and settled on one somewhat like the one in the article. It took me and my Dad about 8-10 hours to build and cost around $250 US. With a cheap 150 watt Parasound it blows the doors off the house when cranked up (which I don't do often since I already have tinitus from my punk-rawk days) but can blend nicely for really smooth bass when listening to music.

See it here:
http://wisdomtools.com/~brbothwe/shivasub/

If you have the excellent BassBox Pro 6, here is the BB6 data file:
shivasub.bb6

This design (like most sonotube subs) is ported. Even smoother subs (for high-end audio) can be made sealed.

The following site has probably already been posted, but if not check it out:
http://www.diysubwoofers.org

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