A Test. How much Voltage (power) do your speakers need? - Page 86 - diyAudio
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View Poll Results: I measured the test tone at:
2 volts or less 155 37.80%
Between 2-5 volts 139 33.90%
Between 5-10 volts 52 12.68%
Between 10-20 volts 25 6.10%
Over 20 volts. 39 9.51%
Voters: 410. You may not vote on this poll

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Old 19th April 2013, 05:20 AM   #851
Pano is offline Pano  United States
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Quote:
Originally Posted by Ron E View Post
What I am saying is that volts and SPL are intimately connected.
OK Ron, all well and good - but I don't see the point in this context. What is your math telling us that my test is not? What am I missing? Serious question.
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Old 19th April 2013, 10:07 AM   #852
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I would say this test is a lot more accurate than SPL as you have precise measurement tool that are already calibrated and you don't have to add headroom as that is already done by setting the volume knob to the loudest you would want to play.

And volt to SPL ratio is not that proportional meaning you have to add a bit for power compression and saturation leaving you with a lot of guesswork if you are to calculate volt from the amplifier by SPL alone.

As a side note, the PA amp for my subs have signal indicators which shows when the level is above 2V RMS. You feel the bass before they light up.
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Old 19th April 2013, 01:51 PM   #853
Ron E is offline Ron E  United States
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Quote:
Originally Posted by Pano View Post
OK Ron, all well and good - but I don't see the point in this context. What is your math telling us that my test is not? What am I missing? Serious question.
SPL tells how loud you are listening and helps make sense of the voltage reading (when sensitivity is known). As the math shows, input voltage depends on SPL and sensitivity so there are two sources of variability in the voltage results.

I think your poll is fine, but knowing either the sensitivity or the ultimate SPL allows you to use the voltage as a comparison number to make sense of the numbers. Mat's electrostats are a clear degenerate case that proves my point.

Oh, and voltmeters are average or RMS responding so the actual peak voltage is 1.414 times the reading on sine waves. This is built in to my calculation example.
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Old 19th April 2013, 02:25 PM   #854
Pano is offline Pano  United States
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Correct - and it is also built into my calculations, as explained in the first posts.
Knowing your SPL is valuable, but it's a different test than this one.

Mat's electrostats are a special case, as they seem to be driven by a special high voltage amp. His results don't relate to users of more typical systems, but are certainly important for him to know. Using a commercial sound 70V or 100V system would be similar. I've run Quad electrostatic panels that did not require special amps and the voltages needed were surprisingly low.
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Old 17th May 2013, 12:52 AM   #855
JohnLL is offline JohnLL  United States
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Yesterday I posted my results with my desktop 87 spl speakers at 1m, 25 watt amp driven by autoformer VCs. I measure 2.14 volts. I am really surprised I am using so little power and only slightly more voltage than my 2v dac.
Pano I hope you will allow me to take this a little OT with this practical issue. The avc's will attenuate a maximum of 41 db and on rare occasions I am at the max. I have my eye on new speakers that are 94 spl so something has to give. I know when I did the test I was attenuating 25db and I wanted to know the amp gain. Since the voltage from the dac and amp are so close the amp gain is about 26bd (calculated 25.8db).
The question is if I were to get a amp with a gain of 20 and 7 db more efficient speakers would I be attenuating at almost the same place? Is this true even though the new amp is only 4 watts max?
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Old 18th May 2013, 06:46 PM   #856
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OK, let me think about that.

Yes, it seems to me that your overall gain (including speakers) would be about the same. The 4 Watt rating doesn't enter into the gain equation, it's just the limit of how loud (or how much voltage) you can get without clipping.
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Old 19th May 2013, 10:02 AM   #857
AndrewT is offline AndrewT  Scotland
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7dB more sensitvity and 7dB less gain in the new arrangement will result in exactly the same volume setting of the vol pot.
But a different frequency response from the new arrangement may result in a slight "adjustment" in overall loudness to get a similar "effect".

7dB less power will be needed by the speakers. 24W less 7dB = 4.79W
Your 4W is a good estimate for equivalence. You would lose only 0.8dB of your overhead for peaks.
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Old 19th May 2013, 03:34 PM   #858
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Quote:
Originally Posted by AndrewT View Post
But a different frequency response from the new arrangement may result in a slight "adjustment" in overall loudness to get a similar "effect"
Yes indeed! The frequency and power response will probably lead you to listen at a different setting, even tho the overall gain is the same.

But you'll be close.
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Old 21st May 2013, 12:01 AM   #859
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Thanks for the help Pano and Andrew! It seems pretty obvious but my confidence in my own audio math is not real high.
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Old 21st May 2013, 01:06 AM   #860
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You got it right.
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