TH-18 Flat to 35hz! (Xoc1's design) - Page 75 - diyAudio
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Old 30th August 2012, 02:18 PM   #741
tb46 is offline tb46  United States
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Hi Crescendo,

Very well done (and a bit of envy)! Thanks for posting the pictures.

Please, head NEO Dan's warning, there is just no excuse for frying these wonderful drivers while testing. Also, keep the low cut (high pass) filter in place to limit the excursion at the bottom end.

How did the cone volume correction test turn out?

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Old 30th August 2012, 03:27 PM   #742
epa is offline epa  Netherlands
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Quote:
Originally Posted by CRESCENDO View Post
I did measure the cab (before the driver was broken in) with and without cone volume correction at several frequencies at clip (amp limit light, rather) to see the benefit of cone volume make-up/correction.
was there any benefit?
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Old 30th August 2012, 07:11 PM   #743
NEO Dan is offline NEO Dan  United States
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Quote:
Originally Posted by CRESCENDO View Post
I can see doing this for max voltage tests - good solution to my multi-meter problem. But for sweep testing, I would set voltage (2.83, 28.3) at the speaker terminals to take the voltage drop over speaker wire out of the equation.
The idea is to dial in the setup, without any noise or speaker related issues. If you are loosing voltage you might want to replace the offending wiring.

Quote:
Originally Posted by CRESCENDO View Post
Of course - I don't see FR sweeps completing within 2 seconds.
Actually if you don't have a huge open area to test in you probably are best off with the 128k sweep, I use the 2 sweep average, it takes less than 6 seconds.

Quote:
Originally Posted by CRESCENDO View Post
Let me know if there's any other equipment or specifics you're interested in.
How about the sound card mic preamp...


I'm also interested in your cone correction testing methodology and results.
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Old 31st August 2012, 10:18 AM   #744
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Quote:
Originally Posted by tb46 View Post
Hi Crescendo,

Very well done (and a bit of envy)! Thanks for posting the pictures.

Please, head NEO Dan's warning, there is just no excuse for frying these wonderful drivers while testing. Also, keep the low cut (high pass) filter in place to limit the excursion at the bottom end.

How did the cone volume correction test turn out?

Regards,
Thanks, Oliver.

I guess I like to sometimes live dangerously. I suppose I can hold off anymore at-clip tests

For shows, I have my HPF set to 27Hz/12dB LR. For 1W/1M & 100W/10M, I will have the HPF disengaged.

I'll post the test results below.


Quote:
Originally Posted by epa View Post
was there any benefit?
Indeed!


Quote:
Originally Posted by NEO Dan View Post
The idea is to dial in the setup, without any noise or speaker related issues. If you are loosing voltage you might want to replace the offending wiring.
I'm not saying I'm losing a significant amount of voltage. ANY wiring before the speaker will introduce some resistance and voltage drop. Some say to measure the resistance of the speaker wire and add that to the equation. My theory is: testing at the terminals will remove any and all of that out of the equation. Less math and as close to what the driver is actually receiving as possible.


Quote:
Originally Posted by NEO Dan View Post
Actually if you don't have a huge open area to test in you probably are best off with the 128k sweep, I use the 2 sweep average, it takes less than 6 seconds.


How about the sound card mic preamp...


I'm also interested in your cone correction testing methodology and results.
Sound card is the Echo AudioFire4


Brand new B&C 18SW100 loaded TH-18 (not broken in):
Without cone volume correction, with cone volume correction and, finally, corrected/calculated values to compensate for the meter's C-weighting, with cone volume correction.

Hz _ w/o _ w/cvc _ corr.
35: 117.1 / 118.1 / 120.6
37: 118.4 / 119.7 / ____
40: 120.8 / 121.7 / 123.5
45: 124.1 / 124.6 / 126.1
50: 125.4 / 125.7 / 127.0
55: 125.8 / 126.0 / 127.0
60: 126.0 / 126.3 / 127.2
65: 126.4 / 126.6 / 127.3
70: 126.7 / 126.8 / 127.4
75: 126.0 / 126.5 / 127.0
80: 125.7 / 126.5 / 127.0
85:
90: 126.98 / 127.3 / 127.6
100: 127.8 / 128.0 / 128.3

These tests were done outdoors, at 1M, over grass. Sine waves were played from my MacbookPro, thru my Serato ScratchLive software and interface, out to my Pioneer DJM-800 (mixer) - XLR outs to my dbx Driverack 260 (filters, delay, limiter and EQ off) and finally to my QSC PLX3402. Output was measured with the American Recorder Technologies SPL-8810.

**These tests were completed with only one side of the enclosure thoroughly screwed together with vinyl foam/tape in place of PL or glue.

Last edited by CRESCENDO; 31st August 2012 at 10:20 AM.
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Old 31st August 2012, 10:49 AM   #745
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Nice response! What happened at 85hz?
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Old 31st August 2012, 10:54 AM   #746
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I don't have that sine wave frequency for some reason. If anyone has it, I'd gladly take it
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Old 31st August 2012, 11:47 AM   #747
NEO Dan is offline NEO Dan  United States
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Quote:
Originally Posted by CRESCENDO View Post
I don't have that sine wave frequency for some reason. If anyone has it, I'd gladly take it
REW has a signal generator...

So what happened to the boxes, they don't have the cone correction built in?
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Old 31st August 2012, 11:52 AM   #748
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CRESCENDO, 1M measurements look fantastic! Voltage or Wattage?
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Old 31st August 2012, 11:53 AM   #749
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True.

I felt response was better with cone volume correction, so I kept it. I'll take a picture of it thru the baffle opening when I remove the drivers for more coats of Duratex.
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Old 31st August 2012, 11:56 AM   #750
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Hi Samuel,

These numbers were recorder just as the (bridged, IIRC) amp limit light illuminated, but my volt meter could not adjust quickly enough to display what voltage was reached, unfortunately. I hope to do 2.83 and 28.3v tests soon.

Last edited by CRESCENDO; 31st August 2012 at 11:58 AM.
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