Speaker ohm's?????

I agree with Bomarc's comment's above. The nominal impedance rating is not regulated by the Bureaucrats in D.C. and is little more than a marketing tool. It is much more useful to consider the low DCR point to determine the affective load on a solid state amplifier. The swing of the impedance curve is almost completely insignificant when using a solid state amplifier.

When considering a tube amp the swing of the impedance curve becomes more significant. Sean's remarks above are quite accurate. He expressed this issue much better than I could. The nominal impedance was important when speakers were built with something that actually resembled a nominal load. Speaker builders generally don't pay much attention to the tube guys because they represent a very small part of the market. Hence the impededance swings on a typical speaker are huge. This will directly affect the response curve when a tube amp is used. This seems to be more significant with the SET variety and less significant with the Push-Pull variety. I believe it has something to to with the dampening factor.

Dave

I've heard the Concertos driven by a 100w/ch Yamaha integrated, and they sounded fine--in a somewhat larger room than you've got, probably. I imagine you could get away with 60w in a bedroom. Best to try things you can take back if they don't work.

Hello All
Thanks for allyour help one person asked me to update the trend so what I have right is I'm trying to set up a second system I have a pair of sonus faber concerto that I got from my brother real cheap. and on the speakers it says 6 ohm's I don't have a amp yet but I would like it to be ss amp but not spend alot of money because it is for a bedroom set up. any suggestions would be great Thanks

Update the thread with either the type of speakers/amp you are considering (or own) and you will get much more usable information from this group. Don't forget to include your budget constraints as well. Some caution is advised if you already have purchased speakers and an amp without giving consideration to the match. Let us know.

Patrick

There is no such thing as an "8-ohm amp." For that matter, the nominal impedance of a speaker is just that--nominal. This is another example of how meaningless most quoted specs are. What would be more useful to know is what is the minimum resistance (measured in ohms) of your speakers, and how much power can your amp produce into that load. But even this tells you little, since power ratings are continuous and it's unlikely that the music you listen to contains continuous tones at precisely the frequency at which your speakers present the greatest challenge.

So stop reading spec sheets and just buy a good-sized amp that sounds ok with your speakers. If you start to hear distortion as you crank the volume up, you might need a bigger amp. Seriously, that's about the only way to know for sure.

There was a good thread on this not too long ago:
http://forum.audiogon.com/cgi-bin/fr.pl?cspkr&1026181509

All SS amps should show measurable increase as impedance is dropped. Theoretically, they should all "double down" in power output as impedance is halved i.e. 50 wpc @ 8, 100 wpc @ 4 and 200 wpc @ 2, etc.... Even though many "hi-end" amps are rated this way, reality shows that this is not the case in most situations though. One really needs to check the power at the point of clipping into the various impedances to see how "beefy" an amp really is and not just look at published specs. The less that power increases as impedance is dropped, the more that the power supply and output devices have become choked. If a stereo amp of SS design can't deal with one pair of "normal" speakers ( non esoteric design ) and drive them to "reasonable" listening levels in an average sized room, it should be disposed of. This is true whether the speakers are rated for 4, 6 or 8 ohms.

All tube amps with output transformers should remain relatively constant due to the loading mechanism known as the output transformer. While you will see some differences ( possibly in both power output AND frequency response ) when changing taps with various impedances and speaker loads, the main reason for having the output transformer is to help the amp remain consistent in performance regardless of the load that it sees. Some designs come a lot closer than others do in this respect.

Output Transformerless ( OTL ) tube amps will typically produce less power as impedance is reduced. There are probably some exceptions to this generalization though, but for the most part, i would consider it true. This has to do with the output impedance of the amp and the inability of most tubes and their associated power supplies to supply large amounts of current. As such, these designs would normally prefer to see a speaker with a relatively benign load that maintained a somewhat higher nominal impedance. They do have the potential for more pleasant sonics ( in my opinion ) as you have removed a major source of signal degradation from between the output devices and the speaker. Sean
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Its unlikely that "6 ohm nominal speakers" would hurt any amp. Also, you are calling it an "8 ohm amp" probably because the specs rate its power at 8 ohms and don't bother to list its rating for lower impedances, but really, all amps will drive any impedance down to maybe 4 ohms, but possibly at less power. Don't worry about it.

It's always a good idea to match your amp to your speakers. As far as I know the damage will only occur to the amp if you are requiring it to drive a lower impedance load than it is designed for. Nominal means average, which means the speakers can drop lower usually a couple more ohms.

-aj

Chances are that the amp will be okay. A decent 8 ohm amp would be able to drive 6 ohm speakers without getting too mad at you. My amp is rated at 200 Watts per channel into 8 ohms, and 350 Watts per channel into 4 ohms. My speakers are nominal 4 ohms but at some frequencies actually have an impedance of about 2.3 ohms. Great amplifiers are able to double their power as you cut the impedance in half. Now, at worst case, an amplifier could be designed for 8 ohms and really get overheated and mad at you if you run anything with a lower impedance. An amplifier like that would fizzle out and die on you over some unknown period of time. In general, there is no direct answer to your question since it depends on the amplifier, the speakers, and how much demand (i.e., volume and listening duration) you put on the amplifier.