Speakers on the cheap!

January 16, 2006 5:54 PM

Calling all DIY speaker enthusiasts! I'm packing off to college next year and my anticipated roomate and I are both interested in building a sound system of sorts. We are both somewhat experienced with audio systems (theatre sound techs) but have never tackled any sort of speaker construction project. More inside...

As these will be used primarily, if not exclusively, in a dorm room, mind boggling volume is not really a design parameter, though I suppose if it can be done it can't hurt. More important is nice sounding speakers with clear reproduction across the entire spectrum. And a pony.

We both listen to a wide variety of music, if an artist listing would be helpful, it can be included here. I'm particularly interested in real sub-woofer sounds, way down around 30hz. I'v heard building a woofer isn't a bad starting point for this sort of thing... (some non-ported designs being the easiests to do properly as far as speakers go)

I've know my way around a woodworking shop, but have no real prodigious skill in crafting wood. I'm fairly experienced with electronics and should have access to plenty of nice equipment (I'll be pre-EE major at a large university).

The rooms we're likely to end up in have cinderblock walls, which is a bit of an acoustic nightmare. What is reccomended as far as sound damping wall coverings? (Bonus if it doesn't blatantly violate fire code!)

So what would the real speaker connisseurs reccomend in terms of building a system from mere wood and purchased drivers? I'm assuming building your own speakers is considerably cheaper than buying them, is this true? How much money does one practically have to have to really make such an effort worthwhile? I'm guessing I'll have around $1000 personally to spend on this.

Once we have these speakers built the plan is to hang up a bunch of sound dampening material and play pink noise through them, tweaking an EQ to get a flat response. Any other things we should consider?

As far as amplifiers go we have a fairly nice (if not a bit dated) 400 watt one on hand at the moment. I also have a source of free high quality wood of various types (an uncle with a bit of an obsession).

posted by phrontist to technology (21 comments total)

Just to clarify: We'll have lots of time, but not a ton of money.
posted by phrontist at 5:58 PM on January 16, 2006

Make friends with Madisound
posted by hortense at 6:27 PM on January 16, 2006

I can't help with the how-to-build question, but...I built an entire stereo system with Polk speakers in every corner of the room for zero dollars this year. Just mention what you're looking for to a few people and see what happens, it's amazing how many people are converting to all digital and getting rid of some prime analog equipment. Thanks caitlinb!
posted by cali at 6:50 PM on January 16, 2006

cali: That's not a bad suggestion. It prompted me to check freecycle, and lo and behold someone just posted a listing for some speakers they were getting rid of. Might be interesting if it pans out...

That said, I'm still really keen on building my own.
posted by phrontist at 7:04 PM on January 16, 2006

I used to be really into building my own audio gear and put together two preamps and an amplifier while I was in college and graduate school. Given that you have electronic experience and (likely) access to an EE lab, that might be the way to go. I've always shied away from building speakers because they seem to be much more difficult to design and require much higher tolerances in machining.
I came to this view partly from reading this article, which has a good summary of speaker design. It's written by Lynn Olson, who as a number of good articles and links on his website (though I don't completely agree with his focus on vacuum tubes).
If you're interested in building amps and preamps I can post some references for those as well.
posted by pombe at 7:22 PM on January 16, 2006

pombe: Yes! While my friend has a nice amp, I'm certainly interested in bulding my own, as speaker design isn't very electronics heavy at all. (I'm sure crossover design is rather complicated from the aspect of figuring out which frequencies you want to send where, and for what reason, the actual filtering circuitry doesn't seem too complicated).
posted by phrontist at 7:26 PM on January 16, 2006

I would save some money and forget the "high quality wood". The best vibrational characteristics come from a uniformly dense manufactured wood such as mdf(medium density fiberboard).

A few years ago I picked up a relatively inexpensive book at Radio shack on constructing speakers. I loaned it out and never got it back, but it was very good.
posted by sciencejock at 7:30 PM on January 16, 2006

I had a DJ in the dorm room next door, and I almost slew him on a number of occasions, as he liked to practice his mixing at full club volume. Please invest in a good set of headphones instead of floor-shaking amps. No dorm that I've seen is built with any sort of sound-proofing. Your neighbors will like you much more if you consider their dorm experience as well as your own.
posted by jellicle at 7:34 PM on January 16, 2006

Two words: BASS TRAPS.

Cubic cinderblock rooms will sound awful without bass traps. The DIY Jon Risch design is very popular. For your purposes, cylinders may be easier to place in the room if there are restrictions on holes in walls.

MDF sucks to work with. Dust-o-rama, and toxic in large doses. The weight is a logistical nightmare if you need to move the suckers. Try to use zero-void plywood instead. It's usually called Baltic Birch or Apple Ply.

Speaker-wise: Don't knock an open-baffle until you've listened to one. Same for single drivers. Same for TQWTs. As you may know, there is some subtlety to cabinet design and driver parameters; don't wing it the first time. The books by Dickason or Weems are the usual starting references.

One last thought, if you are serious about bass: Dude - You want to build yourself some Karlsons!
posted by Triode at 8:00 PM on January 16, 2006

For jellicle's benefit, what you need is a really big subwoofer - you can call it "The Lease Breaker!"...

Building your own speakers is a carpentry project, if you have access to the right equipment it might be worthwhile, but I'm electrical, and I wouldn't go near it. On the other hand you can pick up pretty good deals in used speakers. Watch ebay for a pair of Sound Dynamics 300tis for around $300 and you can't go wrong (no doubt there are other bargain models, check audio forums for up to date recommendations).

The Do-it-Yourself projects that look the most interesting to me are the sonotube sub, and cat-5 speaker cables. Of course building your own amplifier, eq, home theatre PC with room adaptive equalization are all interesting. I have also played with the idea of building my own DAC, which is surprisingly easy for a hobbyist.

I haven't done any of that though, I don't have the spare money, and since I stopped working in the field my audiophile aspirations have slipped a little. I pick up stuff from the garbage, or sometimes used on ebay, and make it fit my requirements.
posted by Chuckles at 8:07 PM on January 16, 2006

More help here.
posted by hortense at 8:17 PM on January 16, 2006

I had actually seen the sonotube before, and it certainly looks cool, but how does it work? Can anyone link to or explain it's theory of operation? What purpose does a giant rigid tube serve? Wouldn't it resonate at a particular frequency, providing everying but a flat response?

I'm confused...
posted by phrontist at 8:22 PM on January 16, 2006

Ok, so much for last thoughts from Triode... More thinkings:

Build a pair of 12" Karlson cabs, and stuff 'em with a nice set of coaxial drivers designed for use in stage monitors. Some thing like the Radian 5212B, or something from P-Audio. Buy 'em used on eBay if you need to, pro-gear drivers are tough and rebuildable.

In my opinion, there's no music down at 20 Hz. Get down to 60 or so and you're good. Additionally, the cabinet volume delta between 60 and 20 Hz boxes may be the difference between merely 'big' and 'doesn't go through doorways or fit in a vehicle'. Yeah, I know it's fun to brag about being 1 dB down at 16 Hz or whatever, but IMO the day-to-day livability and musicality of such a beast will be lacking. Engineering is the art of compromises; don't build yourself a 20 Hz hair shirt.
posted by Triode at 8:30 PM on January 16, 2006

Well the theory is that a tube is much stronger and much more rigid than any other shape (other than a sphere, of course), think of a submarine. Sonotube is also dirt cheap, so you have an interesting starting place for a project... I don't really know how effective it actually is though. I'll see if I can find a better link, I'm sure I have seen a more thorough site, that was just the first relevant google result.
posted by Chuckles at 8:33 PM on January 16, 2006

Chuckles: So what exactly does the tube do?
posted by phrontist at 8:39 PM on January 16, 2006

PendanticHazingFilter: "sound dampening material"

Very little can make soundwaves wet or even moist. What you want is sound damping material.

Everyone gets razzed for this sooner or later. I sure did. No malice intended, ok? And to make up for being a jerk, here's a bit of an answer about tube response
posted by Triode at 8:57 PM on January 16, 2006

The sonotube is just one way to build a large volume enclosure with minimal effort. Confusingly, I think the one I linked uses another much smaller piece of sonotube as a port.
posted by Chuckles at 9:55 PM on January 16, 2006

$1000 will get you some good DIY speakers for sure. I wouldn't call a grand "on the cheap" myself.

Since it's your first go at it, you might want to use existing plans or even a kit. Madisound has them too. I second them as a resource.

The last set I built was a kit. The first speakers I built (in college) were complete custom jobs--my own design based on my analysis of the original Thiele-Small articles. Here's one:

Thiele, A. N., "Loudspeakers in Vented Boxes: Parts I and II," J. Audio Engineering Soc., Vol 19, No. 5, May 1971, pp 382-392

Here's a good summary of their work.

I had fun doing all of the analysis and then heading into the wood shop to create. The U of Michigan had a great student woodshop where I spent many hours building different designs.

So you may want to go that route too. Find some drivers at Madisound or Parts Express, look at the T-S parameters, make some calculations, dream up some cool shapes that fit the params, and go to town.

Good luck!
posted by nonmyopicdave at 10:36 PM on January 16, 2006

Be careful. Theft in college dorms is epidemic.
posted by ori at 11:57 PM on January 16, 2006

Some quick comments on (pre)amplifier design. First, unless you plan on playing records, preamp design nowadays is incredibly simple, because CD and DVD players produce 0-2V outputs, so with an amplifier with reasonable gain your preamp doesn't need to amplify anything. A preamp just serves to do volume adjustments and source selection, (and Eq if you want it). You can make a very good preamp using AD797 op-amps as followers with some good audio potentiometers for volume control. For low noise design, Analog Devices is your friend.
Amplifier designs are considerably more involved, and range from the very simple to the very complicated [pdf]. There are a lot of designs floating around the web, and in various publications. One thing to beware of is the vast number of unscientific claims pushed in the audiophile world, so take what you read with a grain of salt. Being an EE will help you here.
posted by pombe at 8:08 AM on January 17, 2006

I'm a real fan of Danny Richie speaker designs and have built a few speakers from his site GR Research. If you search the web there are many sites with info and even free designs that can be astonishing for the quality of sound for the money spent. Definitely go with MDF because of its acoustic characteristics instead of plywood. You can always add plywood veneer if you want that look. For the bass junkie nothing beats a good subwoofer and in a small dorm room where space is a premium that's the way to go. Spend your money on good drivers and crossover components. You can build speakers for around $1k that will equal or better $5K+ commercial speakers. Not that cheap, but you can build other models under $200 that sound good with closeouts from PartsExpress. They also sell the LoudSpeaker Design Cookbook, which will be a good resource. And some decently priced subwoofer kits that provide great low range with good musicality at a bargain price. I'm gearing up to build my dream speakers the PHL Revelator that are by far the best speakers I have heard for any price. They could be the last pair of speakers I ever build (or at least that's what I'm telling my Wife! ;-))
posted by white_devil at 7:06 PM on January 17, 2006