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david henman said:
...over the weekend i acquired a power amp for my stage monitors. problem is, it puts out 4 ohms, and my speakers are rated at eight ohms.

will i encounter problems?

thanks,

-dh
David, is it a solid state power amp?

Solid state amplifiers are much more forgiving than tube amps. They don't really have a specific impedance like 4 or 8 ohms. Rather, the lower the load the more power they put out. If the load is too low the amp can burn itself up. So the designer sets a lowest limit load impedance for the power the amp can handle. It could be rated 100 watts at 4 ohms and as long as the load is never lower then the amp will run just fine. If you plug in an 8 ohm cab the amp will just put out a little less power. There should be no differences in tone, just power.

Tube amps as you know are a bit more fussy but even then a 2:1 mismatch shouldn't bother the tubes all that much, although the tone will change and you'll have to decide for yourself if you like it or even notice it.

Just FYI.

Wild Bill
 

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"Just the same only different..."

davetcan said:
David, sorry for the small hijack but I'm always confused by this stuff too.

Bill, if you think back to my concern with my Allen amp with the extension jack wired in series. Are you saying that if I add an 8 ohm cab to the combo, resulting in a total of 16 ohm load, I should still be OK with the ohm switch on the combo set @ 8 ohms? I only have a 4 or 8 ohm option on the combo.
Yeah, nothing's likely to blow up or anything. If you were to play the amp consistently at 8 or 9 the output tubes might lose a couple of months of life but that's about it.

I've forgotten our thread about your Allen amp. Is it like old Fenders, where you have a speaker and an extension speaker jack and just one speaker won't work if you plug it into the extension one? This arrangement works by putting any extension speaker in series with the regular speaker. That would make the speaker loads add up. If the jack is just an extra parallel connection and you can plug into either one this would put the loads in parallel and you divide the 8 ohms by the number of 8 ohm loads involved.

My memory worked fine before the kids came...
 

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david henman said:
the only concern i have now is power: will the 300 hundred watt alesis amp (solid state) have sufficient power for three large vocal monitors, each rated at 250-500 watts program?

-dh

David, your question implies some basic assumptions that might be hurting you rather than helping.

The speakers are rated at the maximum power rating that will not blow them up. This has nothing to do with how much power is needed to drive them. A half watt of power should still drive them!

Now, we have to assume that the monitors are reasonably efficient. If they are, a few watts will sound loud. You feed them more if you need them louder to be heard over the damn drummer! Different speakers and cabinets have different efficiencies. We can only guess about yours. If they do indeed need hundreds of watts I'd suspect they're actually blown! You should be able to turn the volume control up just enough to put a few 10's of watts into them and that should be enough.

Since power is shared among all the monitors no matter how it is split up with different speaker loads or whatever one would think that 3 x 250-300watts is more than safe enough. You've got a total of 300 watts available and you're gonna split it 3 ways. Even dialed to 10 there's no way each monitor will see more than it can handle.
 
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