Audio Systems: 6 ohms?, input power level, ohm speaker

Question
Hello if the qsc gx3 puts out 425 at 4 ohms per channel  and 300 at 8 ohms per channel how much does it put out at 6 ohms per channel rms?I ask because I have a 6 ohm speaker.THANKS  

Answer
Well, it would be somewhere in between those two values.  Since 6 ohms is right in the middle it is a safe assumption to assume the power would be right in the middle between 425 and 300.

But, it really doesn't imply much in terms of the listening experience and the actual application.  Here's why.

ONE:  The power output is measured into a pure resistance.  But, in actual practice you have speakers connected to the amp.  And, the speaker impedance is NOT a pure resistance, in fact, it is not even a constant resistance.  A typical loudspeaker impedance will vary from a little below its rating (like in your case the 6 ohm speaker may drop down to 5 ohms at frequencies near its low frequency resonance point) and rise to as high as 10 times that value as the frequency increases.  So, the power delivered into the speaker changes with the frequency of the music signal being fed into it.

TWO:  The human ear is very non-linear.  We talk about audio power in DB or decibels.  The hearing level of most listeners cannot differentiate between only 1DB difference in sound level.  Most people can hear a difference of 2DB and just about everyone can hear a difference of 3DB difference.  What this means it that if the sound level is turned up 3DB it would be a small, but detectable increase in sound.  And, if the sound level was turned up about 9DB the listener would think it to be about twice loudness on a subjective scale.  Here is the rub:  A 3DB increase in sound level is twice the input power.  In other words, going from a 300w input power level to a 600w power will give a small increase in audible level.  To double the level of the sound you must increase the input power by almost 10 times. So, to double the 100w sound level it requires nearly 1,000 watts!

So, the difference in sound level from the amplifier when going from 4 ohms to 6 ohms or so is not going to make any significant audio difference in output level.

Hope that is understandable.  Let me know if you have further questions.