That is true I have noticed that they tend to have their own sound when you compare them. I haven't compared the top of the line ones though. but I have heard the Pioneer sc-07, Sony 5400ES, Yamaha 3900. Denon 3808. Marantz 7002
But how can you tell which has higher current if I am saying it right.?
is their a formula? eg. the yamaha 3900 has the same numbers as the Yamaha Z7 but it is reported that the Z7 has higher current output. But no were in the documents ore peoples measurements is this info apparent .
I think what you are getting at is what an amp does as the impedance drops. For most receivers they quote the power into an 8 ohm load. This is normally a resistance not a speaker. If they do not specify the performance into a four ohm load, it is safe to assume that the amps current is maximum into an 8 ohm load.
Now I find some of the current crop of receivers are using integrated circuit output stages, which have a miserable performance.
You are pretty safe in assuming that the current output of the lower priced receiver does not increase as impedance drops and that the power into a four ohm load is half that into an 8 ohm load.
Now the situation gets worse. Loudspeakers are not resistors, they present a reactive load, with current not in phase with voltage, that makes the impedance look even lower to the amp, limiting power further.
There is another factor that makes the situation worse. Whatever the manufacturer says most speakers today perform more like four ohm speakers than 8 ohm ones. In fact if you have a tower with more than one bass mid driver you can pretty much go to the bank that impedance will fall to four ohms or less below 600 Hz.
So what output do we get out of a budget receiver rated at 100 watts per channel driving a speaker above? If it is the common 2.5 way tower, and assume a typical phase angle, then we find that our 100 watt specified receiver actually delivers about 35 watts to that speaker before the onset of clipping. Such amps actually don't sound very good when pushed, only at low level. Distortion measurements into a resistive 8 ohm load tell you little about the real world performance of an amp or how it will sound.
What you really need is an amp that will increase it power output at least 50% into a four ohm load, and preferably increase it 100%
I believe there are some receivers in the top price brackets that can do this, but most can't.
If the receiver manufacturer only specifies power into an 8 ohm load, you have every right to assume it is a current limited receiver.
There has been another issue that has come along in recent years. THX specs demand that a speaker is stable into a four ohm load, in other words will not blow up. However what the manufacturers have done, is add current limiting circuits to prevent damage to the output devices, to prevent failure. The result is sudden onset of hard clipping.
I think the increased processing demands of new receivers, has made the receiver a poor option. We have a thread open about how hot these receivers are getting, and a thread were one caught fire.
I think we are at the point were the lower to mid price point receivers are best just used as pre pros for the front three channels and capable external amplification used for the front three.
If you are considering the top priced receivers, my advice would be to go full pre/pro instead.
