This post is cross posted on several forums. This is not were I normally post.
I have run T/S tests on a pair of 1772's using a Smith & Larson Speaker Tester. The drivers were broken in for one hour a Xmax. Average of three runs each for the two drivers are:
Re ohms 7.28996
Fs Hz 42.59512
Zmax ohms 28.85236
Qes 0.44508
Qms 1.31602
Qts 0.33256
Le mH 0.04414
Diam mm 165.5
Sd mm^2 21512.25
Vas L 72.76948
BL N/A 7.4432
Mms g 12.6453
Cms uM/N 1106.912
Kms N/M 905.7046
Rms R 2.57074
Efficiency % 1.1911
Sensitivity dB(1 watt) 92.76138
Sensitivity dB(2.83 volt) 93.166
The S&L tester does a constant current test, so the numbers will differ somewhat from testers that do constant voltage. The results are not surprising. the Vas lower than published is what I normally see, although I would have expected Qts to be somewhat higher than published rather than lower.
Nothing untoward here. I won't try to explain the glitch at 150Hz for now. I am impressed that there is no reflection off of the surround at ~1000Hz. That big old aluminum phase plug plus (I presume) a shorting ring very effectively kills any impedance rise.
One thing of note: The 1772's suspension is either not progressive or only weakly so. Unlike most Fostex drivers that can't be over-driven to Xsus, it is very easy to bounce the TB off of the back plate. Some care will be required is high SLP low frequency applications.
I will mount these drivers in my FT-2000 cabinet (MLTL). I won't be testing on an EIC baffle, so my FR plots may well have some box defraction artifacts in them, but so be it. It may be a few days before I report back.
Bob
