Ohms - how should they affect my decision

[urkid]

I am deciding between 2 H/K receivers. one plays 120 watts per channel, the other 80. the room for this receiver is about 13 x 20. what does this statement mean and how should it affect my decision

"80 Watts per channel, 20Hz – 20kHz @ both Channels driven into 8 Ohms OR 100 Watts per channel, 20Hz – 20kHz @ both channels driven into 4 ohms "

[RGA]

First watts are rather meaningless an dhave been blown WAAAAY out of proportion over the last 2 decades -- see it's easier to advertise watts -- more = better for the average Joe who really doesn't understand what it is their purchasing. Lucky for web-site to hopefully turn the advertising gimmickery around a little bit.

What makes volume in your room is speaker sensitivity, impedence of the speaker and watts. Volume is typically measured in decibal level.

Where watts get tricky for consumers is that they often don;t pay attention to the speaker's senstivity. If you have speakers rated at 85db sensitive and I have speakers (which I do) at 95db sensitivity then I will get the exact same volume with a 10 watt amp that you will get with a 100watt amp - if my speakers have less impedence swing then I will get more headroom as well and basically the amp won't have to stress in certain frequencies -- and I also perceive that such speakers are faster as a result because it doesn't force the amp to swing. (though this is what I hear not what I can show).

Now for your purpose to put it simply a DOUBLING of watts = a 3db (decibal) increase in volume -- so if you went from 2 to 4 watts you would get a 3db increase and if you go from 50watts to 100 watts you get a 3db increase. A 3db increase is barely audible --- thus going from 80 to 100 is less than barely audible.

I'm a bt tired to go further into this right now but if the receivers are from the same maker and your sepakers are 87db or higher rated to 8 ohms chances are that 10 watts will play it loud ---- 80 and 100 will make no difference worth spending.

[kexodusc]

RGA summed it up very nicely. Put another way, that extra 40 watts of power in the larger amp won't even produce a 2 dB difference in volume which is barely noticeable.
The headroom it has might be nice if you have a habbit of driving your speakers incredibly hard (many do), but in a 13 X 20 room, unless you listen to your music from the street I think the 80 watt H/K is plenty of power.
Perhaps there's other features on the other receiver worth buying?
Do you know the sensitivity or efficiency of your speakers?

[Pat D]

I am deciding between 2 H/K receivers. one plays 120 watts per channel, the other 80. the room for this receiver is about 13 x 20. what does this statement mean and how should it affect my decision

"80 Watts per channel, 20Hz – 20kHz @ both Channels driven into 8 Ohms OR 100 Watts per channel, 20Hz – 20kHz @ both channels driven into 4 ohms "
I presume you are talking about the HK 3380 and 3480? The first is spec'd at 100 watts into 4 ohms, both channels driven, whereas the latter is spec'd at 150 watts. I give the 4 ohm spec because I generally care more about how much power the amp can deliver into 4 ohms than into 8 ohms because for many speakers the impedance gets down close to or below 4 ohms in some frequency ranges. In volume terms, the difference in power ratings only amounts to slightly less than 2 dB.

http://www.harmankardon.com/category.aspx?Language=ENG&Region=USA&Country=US&cat=REC

Of the two, I would pick the 3480 because the amplifier is considerably more powerful. But, if the difference in price is important, the smaller one is probably more than adequate with reasonably sensitive speakers (90 dB or so).