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Audio question - running 8 speakers off a 2 channel amp

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Old 01-09-2006, 01:33 AM
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Default Audio question - running 8 speakers off a 2 channel amp

I have a pretty good understanding about ohm load(I think) but I want to make sure I am on the right track.

If I wire 4 speakers to each side of a 2-channel amp, and wire 2 in parallel and two in series on each side, then my load should be 4 ohms, right?

And, will doing it this way put the same amount of power to each speaker? Or will the speakers wired in series have less power going to them than the speakers wired in series?
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Old 01-09-2006, 02:02 AM
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Default Re: Audio question - running 8 speakers off a 2 channel amp

no they do not get the same power, and it depends on the ohm rating of the speakers if you end up at 4 ohms, it is late and I am not going to look up the formula but I think it is (r1 x r2) / (r1 + r2) = ohm, for parallel where r1 and r2 are speaker loads ie. 4 ohms and series is r1+r2+r3 .....=ohm, as far as you want to go .
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Old 01-09-2006, 02:10 AM
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Default Re: Audio question - running 8 speakers off a 2 channel amp

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Originally Posted by noboat
I have a pretty good understanding about ohm load(I think) but I want to make sure I am on the right track.

If I wire 4 speakers to each side of a 2-channel amp, and wire 2 in parallel and two in series on each side, then my load should be 4 ohms, right?

And, will doing it this way put the same amount of power to each speaker? Or will the speakers wired in series have less power going to them than the speakers wired in series?
I have a diagram I can fax you with a 4 ohm load wiring for 4 ea 4 ohm speakers. Send me a PM.
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Old 01-09-2006, 02:11 AM
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Default Re: Audio question - running 8 speakers off a 2 channel amp

what you said for two in parallel and two in series we will call the speakers 1,2,3,4 and assssssume they are 4 ohm. you would take two in parallel and and it would be (4 x 4) / (4 + 4) = (16) / (8) = 2 ohms then take the 3 and 4 speaker in series 4+4 = 8 then consider speakers 1 and 2 as one speaker that is 2 ohms and speakers 3 and 4 as another speaker with 8 ohms and you will be paralleling them (2 x 8) / (2 + 8) = (16) / (10) = 1.6 ohms I dont know If I did that right but it is late.
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Old 01-09-2006, 02:13 AM
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Default Re: Audio question - running 8 speakers off a 2 channel amp

for the speakers to get the same power and not be two low you need to series two speakers, then series the other two speakers and then parallel both sets of them together. and the parallel of 4 4 ohm speakers is 1 ohm which would be to low
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Old 01-09-2006, 02:15 AM
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Default Re: Audio question - running 8 speakers off a 2 channel amp

when you are going to do it you can call me if you have any questions.

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Old 01-09-2006, 09:20 AM
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Default Re: Audio question - running 8 speakers off a 2 channel amp

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Originally Posted by Bigyellowcat
for the speakers to get the same power and not be two low you need to series two speakers, then series the other two speakers and then parallel both sets of them together. and the parallel of 4 4 ohm speakers is 1 ohm which would be to low
That makes sense. Just when I thought I had this stuff figured out! So, series two speakers together to make 2 8 ohm load "speakers" out of the 4. Then parallel those 2 "speakers" to get the 4 ohm load.
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Old 01-09-2006, 09:49 AM
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Default Re: Audio question - running 8 speakers off a 2 channel amp

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Originally Posted by noboat
That makes sense. Just when I thought I had this stuff figured out! So, series two speakers together to make 2 8 ohm load "speakers" out of the 4. Then parallel those 2 "speakers" to get the 4 ohm load.
Then put your ohm meter on the leads that you are going to put into the amp just to make sure you did it correctly. Big Yellow hinted to speakers not having exactly 4 ohms because no speaker will give you a real 4 ohms. Ussually you will see like 3.6 or so (tired myself and can not pull the info out of my puny little brain.) So you can actually ballance the loads out if one or more speakers are a little off.

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Old 01-09-2006, 10:27 AM
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Default Re: Audio question - running 8 speakers off a 2 channel amp

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Originally Posted by Audiofn
Then put your ohm meter on the leads that you are going to put into the amp just to make sure you did it correctly. Big Yellow hinted to speakers not having exactly 4 ohms because no speaker will give you a real 4 ohms. Ussually you will see like 3.6 or so (tired myself and can not pull the info out of my puny little brain.) So you can actually ballance the loads out if one or more speakers are a little off.

Jon
Thanks guys, I think I am figuring it out now. And in doing so, it seems like getting the amp as close to the 2 ohms is basically free power. The only problem I have is the formulas, they make sense until I add more speakers.

If you have 2 4ohm speaker wire in parallel then the load is 2ohms

(4x4)/(4+4) = 16/8 = 2 ohms

Now, if I do what big yellow cat says I basically have made 2 "8 ohm speakers" and when wired in parallel gives me 4 ohms

(8x8)/(8+8) = 64/16 = 4 ohms

Now, let's say hypethetically I add two more speakers to each channel and wired those two in series as well for a total of 3 "8 ohm speakers". Now I wire all three in parallel. My brain is telling me 8 ohm load/3 = 2.67 ohm total load. But, using the formula I get a WAY different answer.

(8x8x8)/(8+8+8) = 512/24 = 21.33 ohms

Which one is right? It has to be 2.67 ohms cause my brain says that's logical! LOL

I know it's Monday and I am slow but I usually get this stuff right away! But I am confused!
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Old 01-09-2006, 10:32 AM
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Default Re: Audio question - running 8 speakers off a 2 channel amp

Quote:
Originally Posted by noboat
.

(8x8x8)/(8+8+8) = 512/24 = 21.33 ohms

!
the formula is for 2 loads not 3. you have to do 2 loads at a time then you can combine them.
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