Links

For audiophools who want to share designs and projects

Links

Postby fusordoug » Wed Jul 14, 2010 9:46 pm

Here are a few I sometimes find handy. Please add to this list and at some point we'll roll it all into one post for everyone.

Pro Audio Schematics
Pro speaker design. If anyone has links to any of the good PJ Snyder speaker stuff, I'd love to put it up here - he was about (or maybe still is!) the best.
Auto subwoofer design
Why guess when you can know? Measure!
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Re: Links

Postby johnf » Tue Aug 31, 2010 9:56 pm

Doug
I just read lynn Olsens notes
I little slanted but still more than worth a read
I used to be an audiopile (yep I spelt that correctly) (definition audiopile = a person who collects very expensive audio equipment then bores others to tears talking about it ie pain in the ass).
I did build my own electrostatics in the late 70's based on the Sanders design each using 8' x 4' perforated metal sheets they sounded great except for poor lower base. But the diaphrams were tricky to make (rubbing graphite into 0.00025" mylar on a sheet of glass) and any sort of breakdown totalled the diaphram.
And yes I had an assortment of supex, Shure, fidelity research, and ortophon cartidges including moving coil.
speakers consisted of various KEF units with me selling the bailey transmissionline versions in favour of cerwin Vega studio monitors 211R's.
These puppies came in at 103dB /watt one meter on axis the only protection a 8A cutout in series with the tweeter.

I still say today that anyone wanting a good stereo / home theatre system should spend 90% of the money on the speakers.

PS I have repaired the ionic tweeters these in this case were the ionofane units 30 watts RF @ 27MHz cathode modulated Beautiful units but they had a bad habit of attracting moths that would fly up the horn causing the output tube many fits destroying it and taking out a few passives around it as well.
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Re: Links

Postby Doug Coulter » Wed Sep 01, 2010 12:00 pm

You made me think of the "other" Olson, Harry F, who was quite a maverick in his time. I'm lucky to have his book, Elements of Acoustical Engineering, but for a lot of things I like Beranek's Acoustics better -- but the knowledge in either has made me a little money from time to time ;) What drives me nuts about either is the electrical circuit modeling they use -- they switch what my mind uses so that what I think of as L, they use C for and vice versa (they make it work with the right math, but it still bugs me). At least R is R.

I agree, it's all the speakers (or any other transducers, as us guys who did phono cartridges know), though I've spent some serious time on making the "perfect" amplifiers and in some cases, you can tell even with those flaws elsewhere in the chain. Hard to beat Dan Meyer's Tiger .01 in either numbers or perceived sound -- but I managed, barely, building off that same design, but using FET outputs (with a special trick to reduce transconductance on the N one so they matched), matched, higher quality parts, and various other brute force techniques. Sold a bunch of those for various reasons, as mine also went all the way to DC and up to about 4 mhz -- I had to put a LP filter on the board for audio uses so as not to have customers making transmitters by accident. I got that one all the way down to .0026% IMD and could only measure even that with 30,31khz 1::1 to get far enough away from the 1khz beat to get a filter that good. I couldn't measure any THD with any gear I could assemble. Could be worse. But mostly pointless. At least it really taught me linear amplifier design over the time I did that -- which has come in handy for other uses, though rarely do I need that level of quality for anything I'm doing -- maybe one of the good specs, never all at once.

A couple of things kind of cured me of audiophoolishness. One was being a musician - and having indisputably pure, perfect sound at my fingertips to compare with the recorded junk. Making my own recordings of non music things also helped -- even a system I wasn't satisfied with for the output of the RIAA did really well -- well enough to fool normal people if I recorded a quarter being dropped -- they all looked at the right spot where it really was dropped when I did the recording, and even now, a system that goes below 30hz (and I have two that get down between there at 17 hz -- that latter one is a TL subwoofer with a 16' pipe) does funny things if you play a recording made of thunder -- soft. Makes people run out and roll up their car windows even on a cloudless day :D In a way, that's a pain as much recorded music has various subsonics they left in as they didn't hear them on the studio monitors -- busses going by the studio or concert hall, and so on, and including weather. Of course, the microphones are another transducer you want to get right. I've been using EV PL-20's as workhorse, and Neuman TL 103's for some things -- they both shine on human speech and singing.

We made those electrostats too, in various sizes here. It was fun to be sure, and they were really good. I never did really like the KLH-9's though. I'm trying to remember the brand of the long-line source ones in a cabinet I heard up in Boston once -- they were really good. They used bags of sulfur hexafluoride in the cabinets to make them acoustically larger, and were about $20k each in 1970's dollars. I gave away a pair of Magnepans recently to a guy who helped me on an acoustics job where we got paid "in kind". Though I have some really good step-up iron to drive things like that, and we even did direct drive off some tube amps, I was always fascinated with (but never did) the idea of using a class-D amp so that once you charged up the capacity, you got the energy back minus the tiny amount that became sound --in the case of a really conductive diaphragm anyway.

After becoming a studio owner, the experience of what it takes to make that "popular sound" and how much munging goes on doing it -- I kind of gave up on the whole game. No recorded drums sound like the real thing, and even as a musician, I went to sampled/electronic sets that "sound good on the PA system". The subtlety of most cymbal sounds seems lost on most audiences anyway, and the dynamic range prevents getting the rest of the music "loud enough" on most target systems. There are similar issues with piano, and even acoustic guitar, mostly solved now by CD's (no wow or flutter) but still dyn range issues if you really want to get it right. Until quite recently, the only audio amp I could tolerate for acoustic guitar, that would actually make one decently louder without clipping on the picking transients, was a monster Klipschorn driven with a few hundred watts. However, that one's gotten better, and I now have a Fishman I like that does as well, and is a lot more portable (but not cheaper). It's purpose built for that, and bi-amped to handle the dyn range better.

What I find hilarious about this is that we all complained to the record companies way back about all their munging, we wanted really good sound, and they of course either ignored or refused.
Now it's biting them back -- since no one can tell the degradation created by mp3 compression (other than us old guys who got used to better things) they lost control over distribution -- bad plus bad isn't any big amount worse! So they are reaping what they sowed in my opinion, and are failing now because they don't sell much in the way of good music anymore. The days when they could get everyone to buy the Beatles, again, on every new format are pretty much over -- and that's been the bulk of sales for a long time. Not much new in my thousands of CDs collection.

Further, we did some tests back when I was in college (early 70's), at large parties (the multi room, multi stereo sort, with lots of both sexes and beer present). We had both great and not so great sound systems, a continuum available. The really good ones only got a few people near them, and they weren't partying, just listening, and mostly male. The crummiest ones, easy to talk over -- those got the "action". Very convincing demo, so the word was "depends on what you want" as it is in lots of other areas. Here, I used boom boxes for background classical music for many years -- it's not as distracting from work as a good system would be. I now have a powered studio monitor in this room, hooked direct to a good receiver (just a pot for level), and I may switch back! Even though it's not great by audiophile standards, it reaches the "distraction" threshold.

As a result of being paid in kind for a job designing woofer testers, I have a super good audiophile system (Joshua monitors, with PJ Snyder's leaf tweeters added and a big sub that makes 28hz cutoff) in my old office, now used as storage. It amazes people to be sure, but I'm no longer so enamored of that. So when I built this lab, and it had to have something, I didn't go so far. I got the TL woofer easy as it's just a pipe between two joists for the second floor....but for regular speakers, crummy old Radio Shack kinds of things with that plastic "linaus" tweeter, 4 placed around the room, also in the ceiling, and a cheapo Onkyo amp for the mains, a dedicated one for the sub (250w). It can go louder than the machines, isn't so fantastic as to be distracting, impresses non-audio-freaks fine....and it just works, no diddling. Even the imaging isn't terrible, but again, not so good as to distract one from other sounds (like where did that thing I just dropped roll off to?).

But you never know, there might be some still-audiophiles around, hence the links. I find it funny and very interesting that every time I mention something I used to do that's utterly off topic to pure science or fusion -- nevertheless, someone else here did that too -- what an interesting resonance!

Since I have all the stuff (including UTC linear standard iron), I still do audio amp designs for the tube crowd. Very profitable but high BS quotient. Nothing like some exotic old tube to get them going. Latest was a 3c33 twin triode amp, DC coupled from input to output xfrmr, with internal feedback (inside the transformer). Found out doing that that I had to make a thermal block for the 7586 nuvistor input diff pair, as otherwise the DC drift was too bad -- just putting a finger on one, but not the other moved it all over. What's interesting about that design is I can fix most of what's wrong with most transformers feedforward -- so you can't really tell how good the transformer was in most cases. Esoteric fun, that.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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