Can someone please double check their own TSPs they measured with the factory specs on the 8NDL51 midbass? Using Clio and DATS V3, measured Qts is close to 0.5.
Those above results are rather high, plus a few other B&C drivers I have on the shelf also check higher in Fs, Qms, Qes and Qts. Do they perhaps measure at higher voltages or are they just that much off.
I understand there's break in required but even after playing a low frequency warble sine through it at just under xmax didn't change it much either.
I want to model some enclosure designs for the driver in ported and sealed boxes. I plan a 3 way with Scanspeak D7608-9200 and Bliesma T34B.
Those above results are rather high, plus a few other B&C drivers I have on the shelf also check higher in Fs, Qms, Qes and Qts. Do they perhaps measure at higher voltages or are they just that much off.
I understand there's break in required but even after playing a low frequency warble sine through it at just under xmax didn't change it much either.
I want to model some enclosure designs for the driver in ported and sealed boxes. I plan a 3 way with Scanspeak D7608-9200 and Bliesma T34B.
I've noticed the same thing with a few different prosound drivers.
High-power "preheating" has helped get the numbers closer to what's published. Thermal expansion of the voicecoil probably closes the gap a bit.
Other models (from Eminence, BMS) have been right on the money at cold temps.
High-power "preheating" has helped get the numbers closer to what's published. Thermal expansion of the voicecoil probably closes the gap a bit.
Other models (from Eminence, BMS) have been right on the money at cold temps.
I think "break in" requires excursion higher than X-max on the tough B&C cones.
Measured the Fs of a brand new B&C 8NDL64-8 at 87 Hz, 7 Hz higher than the spec sheet rating of 80 Hz.
I then “broke in” the speaker by pushing the cone in and out by hand to around Xlim (as far as the suspension would allow) several times, then repeated the test, the Fs dropped to 78 Hz.
I had used around 4V for the two initial tests, after a few minutes decided to try 1V (”small signal”) and read around 82 Hz, 4 Hz higher.
Bringing the voltage back up to 4V, the Fs dropped to 80Hz.
Anyway, B&C have good quality control, you can rely on their published TS parameters being close to the production drivers for your models.
Art
@ErnieM That's what I've been seeing as well with Eminence from the models I've used. They're usually very close, but more importantly close to each other of same model. I usually run the driver to get the VC warm and it gets closer to published Fs, Qts and Vas. It just takes several minutes of 150 hz @ 8V to see some temp in something with a 50mm VC.
@weltersys Art, I can't get myself to be that extreme with a fresh driver. When you hear that faint crunching sound of the glue joints around the spider and surround, it makes me cringe. You're probably right regarding the need to grab the driver by the scruff of its neck to see the oem data published by them, but I tend to be more cautious with smaller drivers. They likely won't see anything below 150 hz, but its nice to know they can reach down to 60 hz.
@Pallas I have Clio and DATS V3, which both almost agree to within 2 percent of each other. Clio uses a hotter test signal so it tends to measure Qts on the lower side. I also have an older Smith & Larson WT3, which falls in between the other 2 setups.
@weltersys Art, I can't get myself to be that extreme with a fresh driver. When you hear that faint crunching sound of the glue joints around the spider and surround, it makes me cringe. You're probably right regarding the need to grab the driver by the scruff of its neck to see the oem data published by them, but I tend to be more cautious with smaller drivers. They likely won't see anything below 150 hz, but its nice to know they can reach down to 60 hz.
@Pallas I have Clio and DATS V3, which both almost agree to within 2 percent of each other. Clio uses a hotter test signal so it tends to measure Qts on the lower side. I also have an older Smith & Larson WT3, which falls in between the other 2 setups.
The main thing is at what efficiency (n0) do they measure? The closer to this spec the more we know the critical T/S specs sum up Vs published specs. T/S Equations and how each one affects the others