A Test. How much Voltage (power) do your speakers need?

[Mooly]

Have just made Acronis disc image

Cool Edit Pro downloaded and running... by the cringe, talk about user unfriendly... I know I know... RTFM first

I'll be back !

[AndrewT]

pic1 shows avg@-27.98
pic5 shows average @ -8.80

Setting the volume attenuator for these two quite different tracks will result in a 19.18dB difference in the predicted maximum voltage needed to be supplied to the speakers.

for example: if one attenuator setting shows 1.2Vac of 120Hz test tone, the other will show 12Vac of 120Hz test tone.

That's a 100:1 difference in required power prediction for just these two examples.

Don't let Pano and others delude you in to thinking that average levels do not matter.
The argument that this 0dBfs is a fixed hard ceiling voltage level allows power predictions is flawed, even restricting it to digital only signals.

I wonder what the average to peak ratios look like in well recorded 192kb/s & 24bit resolution?

[back]

Originally Posted by wintermute

Hi Back, I've read that Rod Elliot article before it is an interesting and informative one. But I don't think you are getting the concept of the 120Hz sine signal. 120Hz is a nominal value chosen because the average DMM is most accurate around that frequency, and the 12db is chosen for calculation simplicity.... it is not a test about music power, it is a test about what voltage level clipping will occur at.

We are talking about digital reproduction here. The whole concept is based around the fact that you can't have a level higher than 0db from the digital source. You are not going to be able to put a 2V 120Hz sine wave and a 2V 1Khz sine wave superimposed onto your digital medium and get 4V out The limit is still 2V, so regardless of the make up of the waveform it is still going to be max 2V out of the digital source. It is a hard limit

Tony.

i thought the purpose of all this was for as to know how big amp we need.

the result for me was 150watts/3ohm or 50 watts/8ohm.

this kind of of power is only a joke for my speakers.

according to elliot and his 4x i would need an 600watt amp

which is what is the one pair of amps i own and i hear a little distortion

at full power which logical.

a little bigger amps and there is no distortion all the way to the limit.

[kvholio]

I prefer to play it loud too
Maybe it's the increased ambient noise in a car that makes
compressed music sound better.
In my experience listening to dynamic music can be troublesome when there's
a lot of ambient noise.

Depending on your loudspeakers it also matters at what frequencies the loudest passages have the most energy.
My loudspeakers are small bassreflex 2-ways with 6.5" woofer,
so below the port-resonance the unloading can be a problem when playing loud.
The "Echoes" track from David Gilmour's album 'Live at the Royal Albert Hall"
for example has a passage where there's a huge amount of lf-energy
-it sounds to me the p.a. was clipping-
that literally startled me when i first heard it, an unsuspecting listener
could easily send his/her woofercones airborne when playing it loud.

[jacco vermeulen]

Originally Posted by Pano

My room is about 300 cubic feet

Hear Yea, Hear Yea, our grand moderator locked himself in the closet again.
Probably meant 300sqft.

(me 18' x <12.5' x <8.5' high, is ~225sqft, largest bedroom on the 2nd floor, cause i have esl2905 and tiny willy amp)

[wintermute]

Originally Posted by AndrewT

pic1 shows avg@-27.98
pic5 shows average @ -8.80

Setting the volume attenuator for these two quite different tracks will result in a 19.18dB difference in the predicted maximum voltage needed to be supplied to the speakers.

for example: if one attenuator setting shows 1.2Vac of 120Hz test tone, the other will show 12Vac of 120Hz test tone.

That's a 100:1 difference in required power prediction for just these two examples.

Don't let Pano and others delude you in to thinking that average levels do not matter.
The argument that this 0dBfs is a fixed hard ceiling voltage level allows power predictions is flawed, even restricting it to digital only signals.

I wonder what the average to peak ratios look like in well recorded 192kb/s & 24bit resolution?

Hi Andrew, yes if you set the volume level based on the first track and then play the 5th pic track you are in for a nasty surprise. If you wanted to play that track at the same volume setting (as opposed to level) you are going to require many times the power to do so, however are your ears (and speakers) going to be able to withstand it? This test is about how loud you will drive your speakers comfortably. If your amp cannot deliver the volume level you want with the first track then you either need more power, OR more gain in the preamp.

I believe anyone would realise once they started playing it, that the 5th track sounded much louder at a particular volume setting and adjust accordingly

But the reason I mentioned that first track was to highlight that the loudest you push a particular track may not be a good indication of the total power you actually need (it may indicate with this test you need MORE power than you really do), IF that track has an overall low level. Maybe that's what you were saying as well

Tony.

[Mooly]

Originally Posted by Tom Danley

Transfer the file to a computer and open it with some thing like Cool edit that can analyze the data in the digital form or try the orban VU meter and see what it says.

Not sure about white noise, the kind used for testing in RF had more like a 10dB peak to average ratio. If any of your circuitry were limiting, you may see a different peak to average ratio when the average level is lowered.

Here is the Denon 0db test track in Cool Edit Pro. It shows as exactly 0db on the screen.

Two shots of some dynamic music. Hard to capture to the exact microsecond to show the peaks. It's Beethoven and the Eroica symphony. First is a ripped WAV lossless file, the second a 64K WMA file. That one actually shows as clipping in Cool Edit. The lossless does not. Double checked a couple of times and the lossless never clipped.

I also tried various tones on the test disc at different levels and all showed as spot on.

Give me a scope anyday

[Mooly]

Originally Posted by AndrewT

I wonder what the average to peak ratios look like in well recorded 192kb/s & 24bit resolution?

Maybe not as different as you might think. This is WAV lossless and 64Kb WMA file compared. I have copy and pasted the left channel 64K image into where the right channel WAV Lossless was so it's easy to compare.

Both tracks play for 15 minutes.
WAV = 157mB
WMA = 7.23mB (look at red highlighted parts)

[Coconuts 500]

Here's some confusion om my part...

I got 1,8V on the maximum loudness that I play at. When playing a bit louder still, which I am uncomfortable with, I got 2,4V.

The speaker efficiency is 89dB.

I calculate the power consumption by taking 1,8V / 8 ohms = 0,225A

0,225A x 1,8V = 0,4W

Could that really be it? Seems kinda small. The power meters on my amp say 1,5-3 W into 4 ohms (again, my speakers are rated at 8 ohms) when I play that loud. I've never known if I could trust those because they haven't been calibrated or anything - that I know of - but I guess could be quite accurate after all.

Another test. My casual listening level.

0,3V. That would make 11 milliwatts.

I just cannot wrap my head around that. Is it really that little? The speakers are big and produce a considerable amount of bass, even at that volume. With such little power? Surprising!

I do realize that this might not be how you calculate the power consumption, and I do know that speaker impedance varies, and that I might have done everything wrong altogether. I measured at the speaker terminals. They are three way speakers, 10" woofer, and stuff.

[5th element]

Originally Posted by Mooly

That's easy to test at some point

How do you get less than 1 db ?

I apologise, in my haste I used 10log rather then 20log. Yes it would give ~ 1.7dB difference.