I was recently looking at some Axiom speakers (since there are a lot of folks in here that use them) and noticed that their bigger loudspeakers run at 6ohms. The 7100 amp is good down to 4ohms per the specs. I have read in some other posts that you can't bridge this amplifier. How do you get the amp to 6ohms or 4ohms, if you needed to?

Just hook it up. The amp will work with whatever load is imposed by the speaker, be that 8 ohm, 6 ohm, 4 ohm, or whatever.

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gonk -- 950 Review | LFM-1 Review | Pre/Pro Comparison Chart | Saloon Links

There is no change needed, whether your loudspeakers are rated 16, 10, 8, 6 or 4 ohms. The rating of the amplifier down to 4 ohms means that the electronics, as delivered, can accommodate the load that 4-ohm loudspeakers present, which may actually be lower than 4 ohms at some frequencies. Since 6-ohm speakers generally present less of a load than 4-ohm speakers, you are OK with 6-ohm speakers.

No matter what the ohms rating is, loudspeakers are not generally linear loads, that is they will present, depending on frequency, a load that varies. Ascend Acoustics presents some measurements of their loudspeakers online. The 'impedance and phase' graph on this webpage show that at some frequencies well below the rating of 50Hz-20Khz, the model CMT-340 exhibits a 4-ohm load, while at approximately 1500Hz it presents a 16-ohm load. Ascend Acoustics reports on the specification page that the average impedance rating of this speaker is 8 ohms. On a logarithmic scale, 8 ohms is halfway between 4 and 16 ohms.

Amplifier designers and manufacturers know that they must accommodate varying loads well, both in delivering an accurate signal and in not sustaining any damage to the equipment. This would be true even if all the speakers in the world had 8-ohm impedance ratings.


[This message has been edited by bestbang4thebuck (edited July 21, 2004).]

That was probably a dumb question, but the reason I asked was because my only (though very short) dealings with impedence changes in an amplifier are with car audio (and bridging). That seemed to be the only way to get from 8ohms to 4ohms and so forth. You hooked the speakers up in parallel or series (I'm too far out of my circuits class to remember if it's the addition of inverses or not).

Thanks for the information guys. BTW, have either of you, or anyone else, tried out the Axiom Main speakers (M80ti's)?

Thanks again!

Matthew Hill has a set of Axioms, including the M80ti's (the Epic 80 system, to be exact); he talks about it at some length in this thread . I think Willscary also has the M80's. I have not heard the M80ti's, but I do have a set of M3ti's that I use as surrounds and have been very satisfied with.

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gonk -- 950 Review | LFM-1 Review | Pre/Pro Comparison Chart | Saloon Links

Better safe than sorry.

I have a set of M80's (axiom) and love them. They are tricky to set up. Once dialed though you will be very happy.

I use the M80's also, and i love them as well, they are efficient speakers, but also can handle an enormous amount of power, and sound better as the power increases. However, i am curious why Tom L. said that they are tricky to set up, i didn't find that they were, but maybe i'm missing a tweak here and there, would you mind enlightening me of what you found when setting them up. thanks alot

Readster,

I had to tweak my M80's by positioning them a couple of feet from the back wall and about 10 feet apart with a slight toe in.
In my "environment" I had to play around with positioning until it created the imaging I wanted. It's not really "tricky" just a time consuming (and fun) experience. I found the M80's the most difficult to adjust compared to other brands I've owned. It's the price to pay for great sound...
I'm very happy with the end result.