Find out how many watts you use

organ · April 2006

OK, I got this formula from a different forum. I think it's correct, I'll have to go through my text book to confirm this but I'm too lazy at the moment.

Use your multimeter. Set it to measure AC Voltage. Play your music at reference level and measure the voltage on one of the outputs of your amp (with speakers playing). The voltage reading will fluctuate because music is complex. Then, you take your highest reading, square that, and divide by the impedance of your speakers. There, you'll have your answer in Watts.

I tried this out earlier today. I pushed my rig to ear bleeding levels that I wouldn't listen at and took the measurement and did the calculations.

Well, at the highest peaks, my speakers were only using 5.29W/ch! Effin encredible! And I used 4 Ohms in the formula just to be safe even though my speakers are 8 nominal.

Dennis Gardner · April 2006

Sorry to hear about your ears...............I hear that Klipsch makes alot of peoples ears bleed.:D

organ · April 2006

I like to let them get physical on me but would never let them make my ears bleed:). They know they have to play nice with me or else I'll feed them SS power.

Polkersince85 · April 2006

Are you sure your calculations are correct?

TroyD · April 2006

We've had this discussion a few times, people are generally shocked at how little power they actually consume.

BDT

michael_w · April 2006

Polkersince85 wrote:

Are you sure your calculations are correct?

He's running 98db/w speakers. I'm pretty sure he's doing just fine with 5 watts :cool:

I need to get myself a multimeter so I can do fancy things like this...

PolkThug · April 2006

You could also get an estimate by putting an SPL meter, one meter away from the speaker, then do your calculations based on the efficiency of the speaker and amplitude shown on the meter.

So, with 90db efficient speaker.
90db on spl at one meter = 1 watt.
93db = 2 watts
96db = 4 watts
99db = 8watts
102db = 16 watts
105db = 32 watts
108db = 64 watts
111db = 128watts
114db = 256 watts
117db = 512 watts

RuSsMaN · April 2006

Yeah, life would be perfect in an anehoic chamber.

Frank Z · April 2006

PT,
Double check your numbers. You doubled up on the 8's

Zen Dragon · April 2006

Organ. Your formula is correct. By the calculations you performed you would only have seen 4.6 volts looking at your multimeter and using the 4 ohms impedance. This does seem a little low voltage wise if you were really pushing it.
A digital multimeter may not be fast enough to capture the fluctuations between highs and lows in the audio signal. I suspect you were pushing a little more voltage and power than that.
A peak RMS voltmeter or perhaps a storage oscilloscope would give you a faster capture time on your signal.

audiobliss · April 2006

Well, considering his speakers are 98db efficient, at 5.29 watts, he should be putting out almost 105db, ignoring the effects his room would have. 105db isn't too bad for rocking out, I wouldn't think.

heiney9 · April 2006

What about the changing impedence of the speaker as the frequency changes. This is a good rule of thumb measurement, but probably not all that accurate. As Zendragon stated the volt meter is probabaly a bit slow to capture the info needed. Neat concept though. And I completely agree the amount of power needed for normal listening is pretty low.

H9

I-SIG · April 2006

Zen Dragon wrote:

A digital multimeter may not be fast enough to capture the fluctuations between highs and lows in the audio signal. I suspect you were pushing a little more voltage and power than that.
A peak RMS voltmeter or perhaps a storage oscilloscope would give you a faster capture time on your signal.

I was wondering about the speed. I figured a standard multi-meter or voltage meter would not have the response needed to even estimate the peaks, much less get close. Then again, 98dB is awfully efficient.

Wes

puunda · April 2006

I use a McIntosh wiht the famous meters on them. And for music, I've never got it above 5W. Anything above 5W is bearable (not too loud), but too inpleasent. I don't think it's the speakers (SDA 1.2TL's), but the bright room. If I had a better room, I believe I can get them much louder. Having said that, most people would only listen to it at 1W. I know cause I listen to them much louder than other poeple I know.

Modvlar · April 2006

Yup Yup,

I've got meters running on all my amps, one even has peak hold. Find background fill music under 1 watt, normal listening around 1-2 watts, loud listening 5~10, and then the wall-shaking ear-bleeding levels which I've never been able to go past about 60w (the point where the police are pounding down your front door, since you couldn't hear them knocking over the music).

If you are able, try using a test tone CD, and carefully listen to the point where the shape of the sound begins to noticably distort (400Hz and less). You'll be surprised how low wattage that is. Only a few speaker companies will list the power to distortion ratios. Sensitivity may be 92db/w, but 1% distortion may kick in at 86~89db.

Tour2ma · April 2006

Power is all about reproducing transients.

W WALDECKER · April 2006

Tour2ma wrote:

Power is all about reproducing transients.

in my system it seems that the more power and by that i mean not just watts per channel but also high current the more effortless the music sounds. having lots of power in reserve is a good thing regardless of how much power the loudspeakers actually see at loud volume levels.thanks....WCW III

Zen Dragon · April 2006

Modvlar wrote:

(the point where the police are pounding down your front door, since you couldn't hear them knocking over the music).
QUOTE]

If you can hear the police pounding then there is still room to move the volume up. I never hear the pounding till it's in between songs.

organ · April 2006

After reading about the delay multimeters have, I decided to try again. This time, I used the loudest passages for measurement.

The test song I used was "Excuse Me While I Kill Myself" by Sentenced. The chorus is the loudest part of the song, had the most consistent dynamics and also the longest, so the meter should have time to catch up. Again, no more than 5.29W/ch. This was loud as hell. The whole house was shaking and I couldn't even stand in front of the speakers because it was painful. Again, I used 4 Ohms for the speaker impedance but I doubt my RF-35's dip that low.

So if I was indeed pulling off 5.29w/ch, that would be around 108db total from both speakers at 1m. This is going by the speakers specs measured in an anechoic room, so it was probably a lot higher than that when room effects are taken into account. It still amazes me how efficient these speakers are.

When I have more time to play around, I'm gonna give it a shot against my LSi9. That should be interesting.

organ · April 2006

Zen Dragon wrote:

If you can hear the police pounding then there is still room to move the volume up. I never hear the pounding till it's in between songs.

LOL:D

Zen Dragon · April 2006

With your efficiency it is possible that is all the power you are pushing. What make/model multimeter were you measuring the signal with and what was the reading?
Another method of power measurement is to put the multimeter in series with the positive lead and measure the peak current flowing. Of course you need to be sure the multimeter can handle the anticipated current, and most handhelds are no good over 10A. You just blow the multimeter fuse.
The formula then becomes current squared x resistance (impedance) to determine power.

unc2701 · April 2006

A slightly better way to do this would be to establish the level, then swap in a CD with a 60hz sine wave test tone recorded at full volume. That way you could look up the exact impedence (assuming you've got impedence charts) and the multimeter speed wouldn't matter. This would represent the biggest transient that could come through off a CD... just be careful not to melt your speakers.

Zen Dragon · April 2006

unc2701 wrote:

A slightly better way to do this would be to establish the level, then swap in a CD with a 60hz sine wave test tone recorded at full volume. That way you could look up the exact impedence (assuming you've got impedence charts) and the multimeter speed wouldn't matter. This would represent the biggest transient that could come through off a CD... just be careful not to melt your speakers.

Excellent idea. A constant test tone would take out all the fluctuations of a musical mixed signal. 60Hz at high power would be a mighty hum. You could go up towards 400Hz as well.

michael_w · April 2006

But who rocks out to sine waves? I like the idea of having a constant instead of keeping so many variables but you'd probably use a lot less average power listening to music despite any big peaks.

This idea might work alright if you measure your normal listeing level with an spl meter and then replicate it with a sine wave but I think if you do it that way you'll be drawing more power and get a higher number.

Find out how many watts you use

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