GPA 416-8B (s/n 0229) after 60-minute break-in.
Added mass method, 52 grams.
Fs = 21.45 Hz
Re = 6.60 ohms[dc]
Le = 1302.62 uH
L2 = 1224.79 uH
R2 = 19.79 ohms
Qt = 0.27
Qes = 0.28
Qms = 8.32
Mms = 67.20 grams
Rms = 1.088135 kg/s
Cms = 0.000819 m/N
Vas = 782.20 liters
Sd= 824.48 cm^2
Bl = 14.649466 Tm
ETA = 2.66 %
Lp(2.83V/1m) = 97.20 dB
I wish I could be more sure of my resistance reading -- stupid cheap multimeter.
Gary Dahl
i dont know if this sounds rude
, i actually just asking if you are going to post the complete measurements i apologize if it was
I agree that would be better, but I don't have enough space to use long gating without getting contaminated results, unfortunately. And my copy of ARTA (version 1.4.2 ) doesn't have 1/48 smoothing. Is it present in the newer release?
Gary Dahl
My post above was written before I saw your second post (with the self-quote). All is well.
If my resistance reading isn't accurate, then the inductance figure could be off somewhat as well. I would normally use the manufacturer's spec for DCR, but the GPA data is (cough) inconsistent.
I'd like to find a better multimeter and double-check that reading. This is why I have held off on posting t/s parameters -- they're no help if they aren't correct.
Gary Dahl
If my resistance reading isn't accurate, then the inductance figure could be off somewhat as well. I would normally use the manufacturer's spec for DCR, but the GPA data is (cough) inconsistent.
I'd like to find a better multimeter and double-check that reading. This is why I have held off on posting t/s parameters -- they're no help if they aren't correct.
Gary Dahl
FWIW, all the 515, 416 OEM or factory kitted re-cone measurements I've done/seen over the decades have had ~1.2-1.3 mH/1 kHz inductance. Your DCR OTOH is a bit high for the few 8 ohm OEM 416s I've measured [~6.4-6.5 ohms], though GPA 515-8Gs are around 6.8 ohms, so with GPA's consolidation of parts apparently making weak motor 515s compared to the OEM units judging by its more extended frequency response, higher DCRs may be the norm now.
GM
GM
Having worked at B&C I can tell you that they are the rare trustworthy company.
I was concerned about the large dip at about 700 Hz in the data for the GPA driver as well. Nearfield it was quite pronounced. The impulse response also showed some serious ringing.
Did you measure the resistance of the meter's leads and probes by taking a reading with the probes touching together and substracting that reading from the one you got from the driver? That can make a difference of .4ohms or more.
What is the protocol for doing this properly? I'd like to see these results as well.
Here's one 515-16C (s/n: 0201)
Fs = 19.67 Hz
Re = 10.10 ohms[dc]
Le = 2014.44 uH
L2 = 1700.26 uH
R2 = 26.35 ohms
Qt = 0.23
Qes = 0.24
Qms = 6.65
Mms = 66.31 grams
Rms = 1.231868 kg/s
Cms = 0.000987 m/N
Vas = 942.50 liters
Sd= 824.48 cm^2
Bl = 18.641369 Tm
ETA = 2.90 %
Lp(2.83V/1m) = 95.71 dB
Added mass = 52.00 grams
And the other (s/n: 0202)
Fs = 17.76 Hz
Re = 10.10 ohms[dc]
Le = 1560.53 uH
L2 = 1554.85 uH
R2 = 26.22 ohms
Qt = 0.20
Qes = 0.20
Qms = 7.33
Mms = 71.83 grams
Rms = 1.093800 kg/s
Cms = 0.001118 m/N
Vas = 1067.21 liters
Sd= 824.48 cm^2
Bl = 20.039295 Tm
ETA = 2.85 %
Lp(2.83V/1m) = 95.64 dB
Added mass = 52.00 grams
I made multiple measurements of both the 416 and 515 woofers, before and after break-in, and with varying amounts of added mass. I also made some closed-box measurements. Results were quite consistent, despite my closed box being outside the optimum range for this type of measurement. The difference between the two 515s was also consistent. My 416s are more closely matched.
Gary Dahl
Because of the back EMF of a high efficiency driver a multimeter will always have trouble with this measurement. The cone only has to move a small amount to generate some voltage and this messes with the multimeters imposed voltage. Better is to use a full impedance measurement and get the DCR from that.
A near-field measurement is just done without any gating at all. The exact mic position is not critical, but not right on center is probably better.
A near-field measurement is just done without any gating at all. The exact mic position is not critical, but not right on center is probably better.
Well, there still has to be a gating somewhere since what is measured is the FIR of the driver
Thanks guys! My multimeter is an Extech TrueRMS 22-816, which I thought was decent when I bought it a few years ago to replace my old Micronta. I became frustrated with it, though, because the voice coil resistance readings were dancing all over the place.
Earl, you're absolutely right. When I read your post I had just discovered this for myself! I was taking another reading and noticed that it jumped in response to a noise in the room. For fun, I tapped on the cone and of course the reading went crazy.
When I touch the test leads together, the resistance reading wanders around the neighborhood of 0.1 - 0.4 ohms, occasionally reaching 0.0 or 0.5 ohms. Is that normal?
Dumptruck, thanks for that. I thought it had to be somewhere in ARTA but hadn't found it.
Gary Dahl
Earl, you're absolutely right. When I read your post I had just discovered this for myself! I was taking another reading and noticed that it jumped in response to a noise in the room. For fun, I tapped on the cone and of course the reading went crazy.
When I touch the test leads together, the resistance reading wanders around the neighborhood of 0.1 - 0.4 ohms, occasionally reaching 0.0 or 0.5 ohms. Is that normal?
Dumptruck, thanks for that. I thought it had to be somewhere in ARTA but hadn't found it.
Gary Dahl