There is no headroom involved though. The test will mathematically determine the maximum peak voltage your amplifier will ever be called upon to output given your maximum volume control.
see, I borrowed my Audio Precision analyzer to a friend and he wouldn't return it...
to get some perspective on the measurement procedure... first I used my CD player as source so that there isn't even the slightest acoustic noise. the sine was modulated so that it's easier to detect, the ear tends to accommodate with steady tones.
second, since the amp was actually functioning as attenuator (amp vol was almost all the way down and so was the volume on the D/A), I had to measure the level at the input and compute output based on amp gain and volume pot division factor (it's a digitally controlled attenuator, it's easy to do that with precision if you know the tap). then, since the DAC output was 1mV for that setting, I couldn't use my cheap DMM to measure and used the mic input on the laptop instead, since it has pretty low distortion/noise and I know the full scale input voltage (100mV). and then I did a FFT on the acquired signal to determine the actual level of the 3kHz component, so that I don't use the peak-to-peak value which includes noise. now how twisted is that? still, if done carefully the method can be pretty accurate.
all this, obviously, until the friend returns the AP analyzer
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One Month Later
Well here we are one month later and winding down. Not yet 100 votes, but close. Thanks to all who have participated. It's nice to see DIY'ers actually doing something and not just talking about it.
The poll results speak for themselves as to how much voltage most of us use on a home system. There is a wide range with most of it fairly low - lower than I expected.
Please remember that this is not a test of amplifier or speaker quality, just a way to find about how much voltage you need to run your speakers. If you did the calculations and found that you are near the edge, you might think about a more powerful amp, or at least one with a hefty power supply. But it seems that most who took the test were not near clipping.
I hope that you all leaned something about your system, or other people's systems and maybe about how digital recordings work. Thanks for taking part.
Well here we are one month later and winding down. Not yet 100 votes, but close. Thanks to all who have participated. It's nice to see DIY'ers actually doing something and not just talking about it.
The poll results speak for themselves as to how much voltage most of us use on a home system. There is a wide range with most of it fairly low - lower than I expected.
Please remember that this is not a test of amplifier or speaker quality, just a way to find about how much voltage you need to run your speakers. If you did the calculations and found that you are near the edge, you might think about a more powerful amp, or at least one with a hefty power supply. But it seems that most who took the test were not near clipping.
I hope that you all leaned something about your system, or other people's systems and maybe about how digital recordings work. Thanks for taking part.
Just for reference
8Ohms : (Vx4)
2v= 0.5w : 8w
5v= 3.125w : 50w
10v=12.5w : 200w
20v=50w : 800w
6Ohms : (Vx4)
2v=0.67w : 10.67w
5v=4.167w : 66.67w
10v=16.67w : 266.67
20v=66.67w : 1066.67w
4Ohms : (Vx4)
2v =1w : 16w
5v=6.25w : 100
10v=25w : 400w
20v=100w : 1600w
So worse case (not counting the under 4Ohm crowd )
36% need less than 16w peak
36% need less than 100w peak
17% need less than 400w peak
4% need less than 1600w peak
and 7% need new gear or more than 1600w
8Ohms : (Vx4)
2v= 0.5w : 8w
5v= 3.125w : 50w
10v=12.5w : 200w
20v=50w : 800w
6Ohms : (Vx4)
2v=0.67w : 10.67w
5v=4.167w : 66.67w
10v=16.67w : 266.67
20v=66.67w : 1066.67w
4Ohms : (Vx4)
2v =1w : 16w
5v=6.25w : 100
10v=25w : 400w
20v=100w : 1600w
So worse case (not counting the under 4Ohm crowd
)36% need less than 16w peak
36% need less than 100w peak
17% need less than 400w peak
4% need less than 1600w peak
and 7% need new gear
or more than 1600w
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How are you getting 1600 watts from 20V @4ohm ....
That's for the peak Vx4= or in that case 20V x 4= 80V @ 4Ohms = 1600w
To quote Pano:
The principal of the test:
With digital playback, there is a maximum value "set in stone", so to speak. That value is 0dB. All other levels are below this. Knowing that, it's easy to figure out what the peak level is; it's 12dB more than your measured voltage. That means peak is 4X the voltage. That's as high as the voltage to your speakers will ever go.
Because you've played back a few CDs and determined the maximum level you use, the loudest level you ever want, you've established your peak voltage.
Playing back and measuring the test tones will tell you what that peak level is. The peak voltage will be 4X higher than your measurement.
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Posts # 482 and 486 clarified the level, in #486 Pano wrote:Just for reference
8Ohms : (Vx4)
2v= 0.5w : 8w
5v= 3.125w : 50w
10v=12.5w : 200w
20v=50w : 800w
6Ohms : (Vx4)
2v=0.67w : 10.67w
5v=4.167w : 66.67w
10v=16.67w : 266.67
20v=66.67w : 1066.67w
4Ohms : (Vx4)
2v =1w : 16w
5v=6.25w : 100
10v=25w : 400w
20v=100w : 1600w
So worse case (not counting the under 4Ohm crowd
36% need less than 16w peak
36% need less than 100w peak
17% need less than 400w peak
4% need less than 1600w peak
and 7% need new gear
"The test tone is 12dB RMS below FULL SCALE. That makes it 9dB below the highest possible sine wave value. A little confusing, I know. But I believe that full scale should always be the reference."
So for the high power users, to make the math easy, use 10 dB above (one dB goes to power compression) the test tone level to full scale, so:
20v in to 4 ohm = 100w : 1000 watts full scale.
As part of the 7%, I used about 4000 watts of power (in to about 1.5 ohms) in my shop tests while testing and selling various subs, with about 50 watt peaks in to the top cabs.
No one complained the subs were too loud on the indoor tests
.Art
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Posts # 482 and 486 clarified the level, in #486 Pano wrote:
"The test tone is 12dB RMS below FULL SCALE. That makes it 9dB below the highest possible sine wave value. A little confusing, I know. But I believe that full scale should always be the reference."
So for the high power users, to make the math easy, use 10 dB above (one dB goes to power compression) the test tone level to full scale, so:
20v in to 4 ohm = 100w : 1000 watts full scale.
As part of the 7%, I used about 4000 watts of power (in to about 1.5 ohms) in my shop tests while testing and selling various subs, with about 50 watt peaks in to the top cabs.
No one complained the subs were too loud on the indoor tests
Art
I had designed multiple subs back in the early 90's for what was becoming, at the time the boom in rap music ..
They were JBL 2245H drivers, Venturi loaded, bass reflex driven by Crest 10001 amplifiers...I remember one particular concert we had 16 prs of them and (4) 10001 , this was outdoors in a bowl , they had us toned it down as people on the other side of the park ( huge out door park )were having issues with the low frequencies, they couldn't hear the music ( distance and down in the bowl ) but they could feel the low frequency ...
Those subs would blow out a cigarette lighter at 8 ft ...
Never mind the difference between 9 and 12 dB
Whatever...
weltersys,
the 'never mind' wasn't for you.
sorry for the confusion.
revb.