dep@allegra.UUCP (Dewayne E. Perry) (07/10/84)
but the unfinished part of the symphony is supposed to be at the end. Bozak used to provide plans for making your own speakers and sold the same speakers that they used in their own line. The advantage that this gave a person on a limited budget waas that you could build a big box for the speakers (say similar to Bozak's concert grands) and build up the speaker components over a period of time (just as you may do with you audio components). I have made three separate sets of speakers using Bozak components. The first two were constrained by decorating considerations as to size and shape - they were relatively small units (the woofer and two tweeters). However, my last effort went straight to the top of the line. I built their concert grand speakers for about half the list price of the commercial ones. The engineers at Bozak here very helpful in the design and construction of the boxes and had standard wiring diagrams for the components. Further, I was able to buy grill-cloth and acoustic material for inside the speakers. All in all a happy, but time consuming, experience. What Bozak is willing to do now, I dont know. They have gone through several hands since Bozak died, been in and out of business, and now are run (I think) by Bozak's nephew. They may be relatively old technology, but they provide a great sound for classical music (better if you bi-amp them). Its what you hear that counts - dep
pathy@omssw1.UUCP (Mohan Venkatachalapathy) (09/10/86)
In article <3300014@datacube> john@datacube.UUCP writes: > >>Anybody want to buy a pair of obsolete tri-amped techno monsters? > >That does bring up a good point I have been wondering about for some >time. > Does anyone have HOMEMADE electrostatics?
bill@videovax.UUCP (William K. McFadden) (09/11/86)
In article <161@omssw1.UUCP> pathy@omssw1.UUCP (Mohan Venkatachalapathy) writes: >In article <3300014@datacube> john@datacube.UUCP writes: >> >>>Anybody want to buy a pair of obsolete tri-amped techno monsters? >> >>That does bring up a good point I have been wondering about for some >>time. >> > > > Does anyone have HOMEMADE electrostatics? Yes. A friend and I made our own electrostatic speakers several years ago as an experiment (just to see if we could do it). The first one was made from a large piece of 1/8" thick sheet metal and a window screen. Between the sheet metal (a large road sign-- don't ask me where we got it) and the window screen we placed a sheet of aluminum foil inside a pillow case. Then we connected it as follows: TRANSFORMER 1 2 3 >-------- -------------| | | 1= SHEET METAL ) || ( | | | 2= ALUM FOIL ) || ( | | | 3= WINDOW SCREEN ) || ( | | | AUDIO ) || ( | | | AMP ) || ------+ | | | 8 OHMS ) || ( | | |-+ |-----+ ) || ( | | | ) || ( | | | ) || ( | | | >-------- ------+--------------+---------+ | | | | | | +--- + HV - ---+ HIGH VOLTAGE DC POWER SUPPLY We used about 475 volts for the supply. (Current drain was very small- less than 1 mA.) The transformer was a push-pull audio output transformer taken from an old vacuum tube amplifier. The speaker worked, but was very inefficient, even for an electrostatic. The main reason for this was the large spacing between the elements. Since the speaker was a big capacitor, its response was essentially that of a high-pass filter, making it a very good tweeter. We improved on our initial design by using three sheets of aluminum foil for the elements and layers of waxed paper as insulating material. This was sandwiched together and ironed (the heat melted the wax) so the whole thing would hold together. (We got a lot of funny looks from our friends as they saw us ironing this thing.) The result was a flat sheet one foot wide and five feet long, which we hanged from the ceiling. The effeciency was much better than before, but still not as good we were hoping for. Nevertheless, we had a very good sounding tweeter. Experimentation led to a final configuration of three layers of waxed paper between the aluminum foil sheets. Fewer layers caused arcing; more layers reduced efficiency. On the outside we put layers of waxed paper to insulate it. Here's how the layers were arranged: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | P F P P P F P P P F P P = WAXED PAPER F = ALUMINUM FOIL The best feature of this speaker is that it is very inexpensive. It isn't a really practical speaker, but it was a lot of fun. -- Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-594 Beaverton, OR 97077 UUCP: ...{ucbvax,ihnp4,uw-beaver,decvax}!tektronix!videovax!bill GTE: (503) 627-6920 "How can I prove I am not crazy to people who are?"
keithe@tekgvs.UUCP (Keith Ericson) (09/26/86)
Regarding bass reflex speaker designs: the advantage offered by the bass reflex cabinet, aka a Helmholtz resonator (or is is Hemholtz?), is that it provides another degree of freedom to the speaker-system designer. The speaker (driver) itself has its resonance, due to the weight oops - mass) of the cone, the springiness of the suspension, and there are losses in the suspension, et cetera, et cetera, et cetera. The first order approximation is a parallel LCR circuit. The enclosure has a similar resonance, losses, and so on. Again the first-order approximation is an LCR circuit. (Now don't jump on my case, already, Dick: I said FIRST ORDER APPROXIMATION, OK?) By properly designing three parameters the system designer can take advantage of these resonances to improve the frequency response - at the loweer frequencies - of the overall system. The parameters are the driver resonant frequency, the enclosure resonant frequency, and the degree of coupling between the driver and the cabinet. Those of you familiar with designing double-tuned filter circuits (aha, I see we do have some amateur-radio enthusiasts in the audience) have seen this before. By properly designing the system the two circuits will interact so as to reduce the effect of the separate resonant peaks and thereby smooth the overall response. But you don't just look at the front panel and say "Well, this looks like a good size for the reflex port" and attack it with your saber- saw. Check out some reference material - Olson's (isn't that the name?) book from the 50's (40's?) is a good place to start. From there - you're a big boy - go look it up. keith PS - #define "you're a big boy" "you're a mature person"