I measured the power consumption by a m60 speaker.
I’ve done these measurements for two reasons: (a) to satisfy my curiosity, (b) to understand whether I need extra power for quality listening. You know this gnawing feeling - I don’t have enough power, the speakers suck all the power from my receiver, I need a power amp...
My audio: Front – m60(2), Center – VP150, Surrounds – QS8(2), Rear – Klipsch 2.0 (4 Ohms each), Sub – EP500. Receiver – Onkyo 703, rated 100W+100W, 2 channels driven.
My room – 16’x28’x9’, the listening distance 12.5 feet.
What I did: played different tones and tunes and measured the voltage on the m60 with a very accurate Fluke 189 True RMS voltmeter. The power was calculated as Vrms^2/8Ohm. The sound level at the listening position was measured by a RS sound meter, slow response, C-scale.
Ok, now to the measurements.
First, I played 1 kHz sinusoidal wave tone on an audio test CD through the receiver connected to a single m60. I varied the receiver volume and here are the results:
Vrms (V) -- Power (W) --Sound Level (dB)
1.53 //0.29 //72 Pretty quite
2.8 //0.98 //78 Getting louder
6.0 //4.5 //85 Really loud
17.1 //36.7 //93 Piercingly loud
If you plot these results (in log scale) the points pretty much will lie on a straight line, as it’s supposed to be. The sound level corresponding to 1W is 78dB. Now, I’m sitting at 4 meters from the speaker, so to convert this to the standard distance of 1 m I will have to add 12dB. Remember, doubling the distance reduces the sound level by 6dB. So the speaker sensitivity is 78+12=90dB/1W/1m. It’s somewhere between the in-room spec value 92db/1W/1m and the anechoic sensitivity of 89 db/1W/1m. This makes sense since my room is pretty big.
So, from these measurements at about 1/3 of rated power I’m getting the sound level that I can not possibly stand for more than a few minutes!
Now move to some real music. For this I put Floyd’s ‘Time’ in an excellent 5.1 Dolby edition and this time I turned all the speakers and the sub back on as I would listen to a 5.1 material. All the speakers were crossed at 80 kHz.
At the receiver volume of -10dB the sound level was 85dB – this was the maximum I can listen to for some extended time. The average voltage on the speaker was about 2V – this is 0.5W of rms power and the peaks were up but never higher than 10V – this is 12W of power. So even the peak power at this level was only 10% of the receiver rated power! No signs of distortion or receiver strain were observed.
Hope it would help others to make their choice. I’ve made mine
