mike@asgb.UUCP (10/26/84)
A few weeks ago I posted a request for info and advice about building speakers. The responses I got through the mail were helpful and generally positive as to homebrew being a viable alternative to the local seller of sound. Regarding Cabinet construction: Somewhat to my surprise, plywood was the chosen material for most of those who got into that area. Advantages, as opposed to particle board were: Weight, particle board weighs a ton. Particle board has a tendency to crumble when handled. Plywood comes in nice finishes, no veniers (sp?). The glue in particle board is like a rock and tends to break saw blades. Take note that this is not knotty fir plywood from K-mart. One person recommended marine grade plywood for its knott free construction and very high quality glues. Another mentioned using 3/4" five-ply lumber-core plywood with good results. Plywood does have the nice feature that the different plys and their characteristics offten tend to damp out vibrations very effectively. The one cabinet design I received was for an Infinite Baffle system. The true infinite baffle is an infinetly wide and high wall in which the drivers are mounted. This is, by some theories at least, the "ideal" speaker mounting. Commercial infinite baffle speakers approximate that wall with a very large box and lots of fiberglass damping material. The smaller the box gets, the more the woofer loading becomes an accoustic suspension system, and the design becomes more difficult. By large box, I mean 10 cubic feet, but 3 cubic feet is common, and about the smallest that really counts. Regarding Drivers: I got one vote each for JBL and Bozak drivers. Both of these companies are aparently very helpful to home builders. There are two outfits in my area, Denver, which sell kits and drivers. They are A&S and Gold Sound. A&S does mail order and I believe Gold does also. Both are advertized under "loudspeakers" in the October Audio - the big equipment directory, and are listed in the manufacturers' addresses in the back. Sorry, I don't have the address right here. Regarding Publications: Many people mentioned "Speaker Builder" magazine. It's $10 for one year, 4 issues. Their address is P.O. Box 494; Peterborough, NH; 03458-0494. Check into books by David Weems (sp?) published by either TABS or SAMS, "How to Build Loudspeaker Enclosures" (approx title) by Alexis Badmaieff and Don Davis, Howard Sams pub. Also mentioned were recent papers by Neville Theile. I haven't seen any of these yet, but those are the titles I got. I didn't get anything more than passing references to crossovers. I suspect that this is the most difficult area of design. Not having test equipment available, I would be in the position of using a pretty generic crossover as far as design, but I would use the best quality components I could find (afford?). My Comments: I'm still undecided whether to build or buy. I would never buy a pair of speakers without hearing them first, but that's exactly what you're doing when you build them (unless you can audition assembled kits). However, I suspect that with careful attention to detail, high quality components, and a lot of hard work it is possible to build something very nice sounding for less than an equivalent commercial product. I'm in a position where I can spend the time and effort to build a good product. But I'm not in the position where I can tune crossovers etc. using any kind of test equipment. Does anybody out there have any info about some of the commercial manufacturers using generic Butterworth crossovers as opposed to specially matched units. I know that some very expensive speakers (B&W KEF two name two) put a lot of research into crossovers. But how about some of the more middle of the road companies that also build a very nice sounding speaker (examples: ADS, Boston Accoustics, many others). Thanks to -- DHS, Tektronix(?) Steve Falco Phil Rastocny Bill Bailey Dewayne E. Perry Brent Laminack Dick Dunn Bob R. (at mgnetp) Mike Rosenlof ...hplabs!sdcrdcf!bmcg!asgb!mike Burroughs Advanced Systems Group Boulder, Colorado
herbie@watdcsu.UUCP (Herb Chong, Computing Services) (10/28/84)
You may also try the Speakerlab people for books on how to design and
build loudspeakers and the parts to do so. I think they make their own
drivers, but I am not sure. They are firmly in the kit business, or they
will sell you plans and the raw drivers to make them. I have heard good
things about them, although I have not heard any myself. I don't have
an address handy for them, but they advertise in the classified sections
of Audio, Stereo Review, and High Fidelity. It's worth a letter to them
to get their free brochure (at least it used to be free). Happy building!
Herb...
I'm user-friendly -- I don't byte, I nybble....
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BITNET: herbie at watdcs,herbie at watdcsumikey@trsvax.UUCP (10/31/84)
All the books I ever read advised against plywood and recommended particle board. There is nothing wrong with plywood as such, but with age it can internally delaminate and cause buzzes and rattles. Particle board may be harder to work with, but it will stay dead. Also, Altec Lansing used to sell a speaker design manual that was excellent. It told how to check resonance, how to match the impedance humps in tuned-port systems, and how to design crossovers with steps and various slopes. I THINK it was about $15.00 and I got mine around 1971. I lent it to a friend and that's the last I saw it. It WAS excellent. You might want to look into Norelco components. B&O, as well as a lot of other manufacturers use the Phillips/Norelco line parts under their own name. They used to be available from McGee Radio in Kansas City, MO. They don't carry as much Norelco as they used to, but they carry enough. I bought some Norelco ad10010/w8 drivers from them a few years ago for about $30.00 apiece, when other sources were selling them for close to $60.00 and as far as I could tell, they were the same woofers in the B&O M70s. The McGee catalog is fairly thick, free, and very interesting. Their prices on complete equipment is above the discounters average, but their prices on raw components is very low. They also carry Oaktron, CTS, and Altec, as well as other brands. mikey at trsvax
peters@cubsvax.UUCP (Peter S. Shenkin) (11/06/84)
There's also a good book published by Radio Shack, and available in
Radio Shack outlets, that's also inexpensive. It covers a number
of designs of cabinets -- including acoustic suspension, bass
reflex and passive radiator -- and how to tailor these to the Thiel-Small
parameters of the speakers (available from the manufacturer). Although
the specific examples given use Radio Shack speakers, the principles are
general.
Also separate sections on PA asnd musical instrument speakers.
It also has a good discussion of how the compromises the builder must
make interact with his or her personal notion of how a speaker should
sound.
{philabs,cmcl2!rocky2}!cubsvax!peters Dr. Peter S. Shenkin
Dept of Biol. Sci.; Columbia Univ.; New York, N. Y. 10027; 212-280-5517