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In Reply to: 16 horns measurements posted by Jmmlc on December 7, 2010 at 01:50:12:
Jean-Michel
A heroic undertaking! Some very useful and unique data is presented, in particular the impulse performance, and the harmonic distortion added by each driver and horn combination. A question was raised by another poster here (seemingly now deleted) concerning the possibility of testing all of the drivers on all of the horn combinations (!) which, though it certainly would be interesting, would have drastically increased the already considerable efforts involved on your part. Presumably all of the drivers and horn combinations were chosen because someone was interested in them to begin with, and as an auto mechanic once told me " I have to start somewhere".
The only drivers in the test I have had some experience with are the JBL 175's. I tested a pair on loan several years ago (driving a home made square tractrix horn with a length of 14" and a 11" square mouth), but never listened to them with music because they did'nt physically fit in my system. The 2 drivers measured quite differently from each other, one covering only 630 Hz to 1.6 K, however the other covered 400 Hz to 1.6K within 1 dB, with a small shelf some 6 dB's down from this from 2 to 2.5K, with a 6 dB per octave roll off after this. I was warned not to cross these drivers below 500 Hz because they would "rattle", but there was no problem apparent with the warble test signals used. These 2 drivers performed differently from each other (apparently they need some fine tuning with an oscillator while installing the diaphragms), and they were also quite different from the example in your test with a home made diaphragm. This is not to diminish the importance of your tests, but to provide a perspective of what can frequently be expected with pre-owned drivers.
Your use of (rather high) series resistance to smooth out frequency response peaks is interesting. I have approached this problem with a secondary air chamber between the compression driver and the horn throat to tune out primary resonant peaks. I actually thought I had invented this, until I read H.F. Olson's Dynamic Analogies.
Thanks for bringing some Big Science to our forum!
Paul
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Follow Ups
- RE: 16 horns measurements - Paul Eizik 20:55:40 12/07/10 (0)
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