duhhh...can i use a 4 ohm receiver with 8 ohm speakers or, visa versa?????

thanks in advance,

A 4 ohm receiver will work fine with 8 ohm speakers. A receiver ONLY rated for 8 ohm speakers will probably self destruct.

thanks, ronk....but not sure what you mean "self destruct"...the speakers or the reciever??

Most likely the receiver, but possibly speaker damage also.

Maybe I shouldn't sound so dramatic. Most decent receivers have overload protection that would probably shut them down before too much damage. That said, if a receiver is ONLY rated at 8 ohms, you probably couldn't call it "decent".

thanks, ronk.....

Thats what I was thinking :)

Actually, very few are rated at 4ohms in any of the mfgr literature. Most have ratings for 8 and 6 ohms, but they aren't necessarily decent. Or not decent. It really depends on what the ratings actually say.

For those who don't really grasp this (and you know who you are! :-)), a n amplifier/speaker impedance mismatch doesn't mean that any damage automatically happens, just that the possibility increases.

If a speaker's impedance is higher than the 'nominal', it merely means that, at a given volume-control setting (which determines output voltage), the current will be lower, and thus the power.

This means that one will be inclined to increase the volume, which means that the amplifier may 'clip' (reach the output transistors' maximum conductance point) while trying to deliver more power.

However, the amplifier will run cool, since the transistors will be carrying less than their design current, and the power supply's rail voltage shouldn't sag with load peaks since the current demand is low.

Now, if the speaker's impedance is a great deal lower than the amplifier is designed to drive, then, at higher power levels, the transistors and power supply can be stressed beyond their capacities.

An amp rated at 100 w/ch will supply this much power into any load impedance. What matters is the output voltage at this power level, which varies with impedance, as simple Ohm's Law describes.

As long as the power level is kept within limits, the amplifier will drive any speaker impedance just fine. Monitor the heat output; that's where overloading an amplifier shows up first.

Most manufacturers don't want to rate their amplifiers for speakers at 4 ohms, because some 4 ohm speakers exhibit such a large variation in impedance.

This variation in impedance makes the problem of guaranteeing the amplifier is stable (not oscillating) very complex. At 8 or 6 ohms with typical amplifier output capacitor sizes, the designer of the amplifer can make choices that guarantee the amplifier is stable for all speakers that call themselves 8 or 6 ohms. At 4 ohms, the designer doesn't have this luxury. If he designs the amplifier for some combinations of inductive and capacitive reactance at the speaker, he'll be unstable for other choices. The only solution is to really overspecify the output capacitors in the amplifier, and use a more expensive feedback circuit which alters the feedback network based on the impedance of the speaker it is driving.

So... the companies that design the amps really aren't just trying to fleece the customers. The amps that can guarantee 4 ohm performance really do cost more to manufacture.

You all are forgetting or never heard of why amps are rated at 8 ohms in the first place.

When I started in HiFi, a few reputable brands rated the RMS sine-wave output power that their amps would do, with both channels driven (= running at the same time), listing the impedance that they were tested with and the % of harmonic distortion at that power level. Most such companies actually underrated their amps. Such companies, in the early 70s, were Marantz, Sony, even Kenwood, Citation (A Harman/Kardon brand). I built a Citation 12 amp, rated at 60 watts per channel both channels driven...etc that put out 88 watts.

Well, at the same time, there were companies like Pacific Stereo's house brand, and Nikko (at that time), and some others, that would hide the RMS rating but promote IPP (Instantaneous Peak Power), or Peak Power. A 25 watt amp with a horrible powr supply could have an IPP of 100 watts!

This was a bit unfair to those who rated their amps honestly.

The FTC got involved in the early 70s and MANDATED that specs be given as to what the amp would do into 8 ohms. Those specs do not reflect any lack of performance at 4 ohms, but rather conform to federal standards.

Unfortunately, we do not know what modern amps will do at 4 ohms. If their power supplies and heat sinks were really beefy, they would put out exactly twice the power at 4 ohms as at 8 ohms. Some of the early RMS-rated amps did exactly that. But some would put out, say, 50 watts at 8 ohms and 75 watts at 4 ohms, indicating that there was some lack in their power supplies or that the heat generated in the amp with a 4 ohm load would not sustain more than 75 watts. Today, who knows? It is a pretty safe bet that they will put out a bit LESS at 4 ohms than at 8 ohms, and I am being conservative; they will probably put out more. But since they are not measured that way, we cannot know.

A 4 ohm speaker will not be damaged by running it on an amp rated at 8 ohms unless the amp is driven to clipping. This sounds like a buzzing sound on top of the audio, and usually kills the tweeters way before it hurts mids or woofers.

A lot of this has to do with how loud you turn it. I fixed a system for a Hollywood choreographer, a 12 year old system, where someone from a sound stage who "knew what he was doing" put six pairs of eight ohm speakers, plus volume controls, all in parallel on the output of an SAE amp. The only reason the amp lasted that long was that the homeowner NEVER played it very loud and the "expert" wired the house with 22 gauge wire...its resistance lowered the cleanness of the sound, especially the bass, but made the amp last a lot longer than it might have.

Do US reviewers not test them on various loads?

Check out this site for some comprehensive test data.

Chicken and egg, Ernie. They now create amps in cheesy receivers to just make it at 8 ohms, probably because of those rules.

I love your story about the guy who "knew what he was doing", but "didn't give a damn about the sound." How sad.

Had a very similar thing here locally. Gentleman, that did the sound system for the local movie theater, wired a home for a local "nabob" back in the late sixties used 18ga zip cord for wire with no volume controls. System lasted for years! Sounded like crud, but it did work.

Local "nabob" thought the guy who did the work was the audio genuis of the ages. All I heard while replacing this mess was how great this genuis was....lol

Argh - sorry I missed this thread.

I have a 6 ohm amp (Yamaha DVR-S100) and I tried to hook it up to a 8 ohm speaker (Infinity CC-3). I blew the center channel (outside chance I screwed up polarity) - should this have happened? Is it a power issue?

thanks,
-Rob