Originally Posted by grigorianvlad
I am probably buying an Emotiva power amp (XPA-200
) . It isnt exactly a powerhouse (my receiver by itself is powerful enough, I just want my speakers to open up with a separate unit).
The idea that an external amplifier will cause speakers to "open up" is an audiophile myth.
The Emotiva descriptions says:
"Equally at home powering a superb stereo system, or the front channels of an audiophile surround sound system, the XPA-200 delivers 150 watts per channel into 8 ohms, or 240 watts per channel into 4 ohms of powerful, clean, audiophile grade audio power."
My amp is a Pioneer Elite VSX-53, speakers are Polk LSi-9s (4ohm, power hungry).
I don't know where you got the idea that Lsi-9s are power hungry, They are fairly typical 88 dB/watt 4 ohm speakers. To be truly power hungry you would need speakers that had sensitivity on the order of 80 dB/w or impedance on the order of 2 ohms.
So, the Emotiva will be providing 240 watts of power into the Polks because they are 4ohms? Or 150W? Why the difference?
In fact the Emotiva won't be providing any more power to your speakers than your AVR unless you play them seriously loud or sit a long distance from your speakers (say 20 feet) etc.
Remember, we are talking the maximum possible power that an amplifier can deliver. Power amplifiers are voltage sources, and are primarily voltage limited.
Using the power calculator at http://www.rapidtables.com/calc/electric/watt-volt-amp-calculator.htm
I find that it takes 24.49 volts to develop 150 watts into a 4 ohm resistor. If I apply the same voltage to an 8 ohm resistor we develop only 74.99 watts. The differnce in power comes about because only half the current flows through a resistor with twice the resistance. Power is the product of amps and volts so half the current (amps) means half the power (watts).
If I had an 8ohm speaker set, would they be less loud because of 150W power?
All other things being equal, yes.
The difference would be 3 dB, which is not all that much. It takes 10 times the power to create the impression of "twice as loud".