EQUAL POWER!!!!!

Posted by Ergin Guney [IP: 165.117.55.57] on June 01, 1999 at 12:34:20
Using Mozilla/4.05 [en] (WinNT; I):

In Reply to: EQUAL POWER!!!!! posted by Bob Walters on May 29, 1999 at 21:27:49:

Keep in mind that the power ratings of amplifiers are "maximum" ratings (subject to measurement conditions) and that, most of the time, amps typically drive speakers with power levels like 2 or 3 watts.

Let's say we have a hypothetical setup with a source component (say, a CD player), a preamplifier, and a power amplifier. Let's say there is a choice of two power amplifiers, one rated for 80W, the other for 40W. Say you have the 80W power amp connected and you set the volume control on the preamp to a certain level where the speakers are being fed with 3 watts of power. If you shut the system down and switch the power amps without touching the volume setting, the speakers would still be fed with the same 3 watts with the 40W amp when you turn the system back on and you will hear exactly the same sound.

Try the same thing with speakers being fed with 35W, and switching the amps will similarly cause no change since 35W is still within the capability of the 40W amp. You will only hear a difference if you set the volume with the 80W amp to feed the speakers with anything more than 40W. Then when you switch to the 40W amp, the most it can feed the speakers with will be 40W and you may hear the shortcoming.

The biggest difference you will experience in this hypothetical experiment is when you set the preamp volume to feed the speakers with the full 80W of the 80W amp. Then when you switch to the 40W amp you will get only 40W. Even then, the difference will be a mere 3dB. (Keep in mind that this will probably be a ridiculously loud continuous volume level anyway. Assuming you have speakers with something like 90dB/W/m sensitivity, 80W would translate into 109 dB at 1 meter!)

Actually it is not even that clear cut because most amps can exceed their rated powers, albeit with higher distortion than that used for the regular power rating...

Bottom line: Don't even bother. Even though you need equal power to all channels to have an ideal Dolby Digital setup, in practice you would only notice a difference (if at all) at very loud peaks, and even then the difference will be a mere 3dB (i.e., barely noticeable).

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