Talkin2Phil

If my receiver (2 Channel) specs are:

Continuous Average Power (FTC) Per Channel :
120 Watts per channel, 20Hz – 20kHz @ <0.07% THD, both channels driven into 8 ohms
150 Watts per channel, 20Hz – 20kHz @ <0.2% THD, both channels driven into 4 ohms

the two models of speakers that I am interested in have wattage max of:

model 1: 200 watts per channel max
model 2: 250 watts per channel max

Will there be a different in the performance of these speakers driven by this receiver?

In general, is there a rule of thumb of matching of receiver watts per channel to speaker max watts?

Mordred

I am not an expert so maybe someone else can fill in the spots I'm not clear on.

If the speakers were exactly identical and one handled 200W max and the other handled 250W max I seriously doubt you would notice any difference. Now, I *think* there can be some danger in underdriving a speaker, but if you're putting out 120W you have nothing to worry about. At 40W/channel I might look for a speaker with a lower max, but again I may be off base. Of course there's almost no way those speakers are identical at all, so yes you will notice a difference in performance. What you need to look for is the efficiency of the speaker. This is measured in dB/W/m, or decibals with one watt of power at a distance of 1 meter. An averagely efficient speaker will be around 90dB. Below 84dB and you might have to crank the volume to get the sound where you want it... above 96dB and your speakers are loud.

Now all receivers offer a 4ohm and 8ohm rating. This is a requirement for CE certification I believe. Most receivers work the way yours does, generating more power at less resistence, most Sony receivers do the inverse and provide less power. The reason is that less resistence means the receiver is going to run hotter. In Sonys case they felt that at 4 ohms the receiver is running TOO hot and so they drop the wattage to compensate.

At 4 ohms you're getting more power but more THD too. Whether you'd notice it is a question you'll have to answer. I think with most speakers, if they are relatively efficient, you're going to perfectly fine running them at 8ohms even if they're rated for 4. I do this with my Klipsch surrounds. I know a lot more about Sony products than others and I can say that at least with regards to Sony there is no reason to ever run at 4. If they weren't required to, they wouldn't even include the option. There should be almost no danger too your speakers when running at 8ohms instead of 4. I can't say for certainty that the reverse is true though (running at 4ohms with 8ohm rated speakers).

rdclark

Yes. The rule is to have enough power to drive the speakers to the levels you desire, without causing the amplifier to clip. Clipping distortion occurs when an amp "runs out" of power, and it can destroy a speaker in an instant.

Power-handling capacity is a useless specification by itself. You need to know a speaker's sensitivity -- how loud it gets for a given power input -- before you can know if some maximum value is relevant. A more sensitive speaker with a low power-handling spec may be just as robust as a less sensitive speaker with a higher capacity.

And in any case "power handling" is usually measured differently by different manufacturers, and not directly comparable.

The best way to choose is to listen to the speakers in person, driving them with an amp comparable to yours. If the speakers easily reach levels as loud as you'd ever desire, with no sense of strain, loss of clarity, distortion, or other anomolies, then they pass the test. Buying speakers made by a company that specializes in speakers is usually a good idea.

RichC

Spiky

Couple more comments.

I would stay away from 4 ohm speakers with that amp. A real solid amp would have a 4 ohm wattage rating of about double the 8 ohm rating, and very little increase in distortion. Since that one triples the distortion and only increases the wattage by 25%, I'd say it really isn't designed to run at 4 ohms.

mordred refers to "underdriving" and Rich refers to "clipping...when an amp runs out of power". These are the same thing.

That's a fairly useful amp rating. It ought to say "RMS" to be more accurate. I agree with Rich about mfgrs having different rating systems, but it is only an issue for speakers. For amps, once you learn how to read the specs, they are fairly accurate and can be compared with your knowledge and adjustments. Assuming it isn't an out and out lie, but they mostly don't do that anymore since somebody cracked down on it a while back. (UL, most likely...fuzzy memory) Speakers are still at the "lying through their teeth" stage.

Sdallnct

In my experience the quality of the amp makes a huge difference. A crappy 50 watt receiver can damage a speaker where as a quality 150 amp, might not.

I once had a speaker that stated it could handle 150 watts. Yet I drove them with a high end 150 watt amp. Never had a problem and the set up sounded great.

blued888

I am currently looking to buy a set of BIC speakers with 6.5" drivers.

Yamaha HTR-5540

Will my 75W per channel amp handle the recommended power ratings of the speakers (10-175W)? Or will the speakers get toasted? If there is no problem, are there any side effects such as distortion at high volumes?