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Power amp and speaker compatability


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#1 Rik (ESA)

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Posted 18 May 2016 - 01:08 PM

First up, I'm sorry if this is the wrong section of the forum - mods, do please move as necessary.

I usually consider myself quite knowledgable on the ohms front, but not today for some reason...

Problem - what tech specs amp do I need for our PA to power 2 X 4ohm subs, and 2 X 8ohm tops?

By my reckoning, each side needs an output of 2ohms from the amp, thus a 2 X 2ohm amp to power the whole lot - is this correct? If it is, not sure on the feasibility on running it from one amp...

Suggestions and guidance most welcome!

Thanks
Rick

#2 dood

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Posted 18 May 2016 - 01:18 PM

Run two separate power amplifiers. One for the subs (a channel each from a stereo power amplifier run in parallel mono) then do the same for the tops. You can then drive the subs correctly if you choose power amplifiers with built in DSP. This also means you don't have to search specifically for amps that go down to 2 Ohms. Those that can handle four ohms minimum are more readily available and probably cheaper.

#3 Rik (ESA)

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Posted 18 May 2016 - 01:24 PM

Cheers Dood - sorry this is where I get a bit lost in terms of crossovers etc. - we actually have two amps already but very amateurly put the subs through the right hand channel of the desk and tops through the left. We then pan bass heavy instruments to the right and vice versa. Not ideal. The subs we have do contain built in crossovers hence I thought it may be best to run one amp and utilise the crossovers?

Thanks again.

#4 bassman7755

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Posted 18 May 2016 - 03:33 PM

View PostRik (ESA), on 18 May 2016 - 01:24 PM, said:

The subs we have do contain built in crossovers hence I thought it may be best to run one amp and utilise the crossovers?

Do the subs have just a low pass filter or do they have a daisy chain output for a top as well ?.

#5 Rik (ESA)

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Posted 18 May 2016 - 03:42 PM

That's a good question - they have a daisy chain output which id assumed sends the higher range stuff to the tops... That said its more likely a filter just for the sub. The subs are peavey messenger 15's if that helps!

Thanks
Rick

#6 Phil Starr

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Posted 18 May 2016 - 07:32 PM

Looks like you are in luck. According to the manual the crossover in the subs give a high pass signal to the tops and Peaveys own matching tops are 8ohms.

just feed the amp output to your subs and use the high pass output from them to your tops and all should be well.

The crossover means you should treat the whole system as 4 ohms each side which should be fine.

Manual http://assets.peavey...17940_12464.pdf

Edited by Phil Starr, 18 May 2016 - 07:32 PM.


#7 Rik (ESA)

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Posted 18 May 2016 - 09:01 PM

Many thanks Phil, just the answer I was hoping for! So a power amp with 2 X 4 ohm putput would power the whole rig?

Cheers

#8 Phil Starr

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Posted 19 May 2016 - 08:02 AM

Yes I think you should have no problems, obviously I don't have the stuff in front of me but it looks good. You'd probably get a better sound with a second amp with an active crossover. A lot of PA amps now have a built in crossover for subs but what you have will work fine and you can upgrade easily enough later if you want to add an active crossover and a bit more power.

#9 Rik (ESA)

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Posted 19 May 2016 - 08:31 AM

Brilliant, many thanks again everyone





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