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#### mrfrankmrfrank

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I work for a school as a computer tech. We are adding a speaker setup to the school's workout facility. I could use some advice on the best way to wire the speakers we have purchased to the amp we have purchased.

I think I have figured it out, but could definitely use some advice of more seasoned audiophiles.

We purchased a total of 10 ceiling speakers.

We purchased an amp that does various watts output depending on what impedance the speakers are wired as.

I want to wire 5 speakers to left channel and 5 speakers to the right channel.

We can just figure out how to wire one channel (we'll say left for this exercise, since the right will be identical)

The speakers are 4 ohm.

If I start with 2 of these speakers and wire them in series, I get 8 ohm.

If I repeat that again with another 2 speakers, I get another 8 ohm.

If I then wire those two pairs of speakers in parallel with the 5th speaker it would be 8 ohm / 8 ohm / 4 ohm. This according to an ohm calculator I found online will be a total of 2 ohms impedance on the system.

The amp at 2 ohms puts out 800 watts / channel.

From what I read about calculating wattage per speaker in a parallel system is it's total wattage divided by number of speakers. (i'm not sure if this stays true in a mixed series / parallel system)

If I've done that math right, and if I've read right, the final calculation is 800 watts divided by how many speakers. 800/5 = 160 watts per speaker.

Each speaker is 125 watts.

thanks guys.

#### Kal Rubinson

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With that arrangement, the single speaker will be handling twice the power of each of the others. Consider putting 3 in series and 2 in series and paralleling these. 12ohms in parallel with 8ohms will give a more reasonable 4.8ohm load and each driver will be getting a more similar drive.

#### mrfrankmrfrank

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I somewhat thought that might be the case with that single speaker taking half of the load and the other 4 working on the other half. (or something along those lines) haha

if I do as you say, and end up with 4.8 ohm, I think the amp would put out roughly 500 watts total, putting 100 watts to each speaker correct?

The amp we have is

http://www.bhphotovideo.com/c/produc...Amplifier.html

#### mrfrankmrfrank

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well, i guess it wouldn't be perfectly distributed would it. the speakers in the 3 speaker series will get less watts per speaker than the 2 speaker series correct

#### Kal Rubinson

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Quote:
 Originally Posted by mrfrankmrfrank well, i guess it wouldn't be perfectly distributed would it. the speakers in the 3 speaker series will get less watts per speaker than the 2 speaker series correct
Right. Consider using 4 or 6 per channel.

This is why distributed systems use a constant voltage output with local, per speaker transformers.

#### mrfrankmrfrank

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not entirely sure what your second sentence was there haha. over my head a bit. I agree that it would be preferable to use an even number of speakers per channel. I could not convince my boss to purchase 2 more speakers (since he had already placed the order and didn't want to spend more money) to make it 6 left and 6 right.

The one thing I considered was that the amp has a speaker a and speakers b outputs. I was at one point trying to do the math on getting the same wattage out of the 5 left and 5 right if I did say 2 left speaker A, 3 left speaker B, and the same for the right channels.

or some combination of speaker numbers using speakers A / B.

4 speakers left A, 1 speaker left B.

any ideas buddy?

#### mrfrankmrfrank

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yea, I can't think of anything that makes sense using the speakers A / B...

If I could convince my boss to purchase just one more pair of speakers, I could do 6 left and 6 right. I could wire the 3 pairs of series in parallel and get 2.67 ohms. The amp can do ohms not at a specific 2 / 4 / 8 increments correct? This way each series pair would get roughly 233 watts which would be 116 watts per speaker correct?

like this

http://www.colomar.com/cgi-bin/h_imp...Z4ZxZxZxZxZxZx

#### Kal Rubinson

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
Quote:
Originally Posted by mrfrankmrfrank /forum/post/19565742

yea, I can't think of anything that makes sense using the speakers A / B...

Agreed. It is the same amp, anyway.

Quote:
If I could convince my boss to purchase just one more pair of speakers, I could do 6 left and 6 right. I could wire the 3 pairs of series in parallel and get 2.67 ohms. The amp can do ohms not at a specific 2 / 4 / 8 increments correct? This way each series pair would get roughly 233 watts which would be 116 watts per speaker correct?

In theory.

#### JerryLove

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Remember that an amp's max power rating is not generally based on prolonged output. You do risk burning out your amp if you attempt to present it with too much sustained load. This is even more true as the ohm load decreases.

Look at the Peavy IDP for example. The designer has stated it will maintain it's listed output at 8ohm or 4ohm for quite some time. At 2 ohm at max output it shuts off in seconds from overheating.

Let's put it another way. We generally look at an amp that can deliver more than the speakers max load. If you've got a 200w speaker, a 250wpc amp is a good thing (though you can get away with less).

Given that: what's the load of all the speakers combined (well, half since that's what's per-channel)?

I don't know what speakers or amp you are using but, if these are all to run simultaneously, I think more amps is a very good choice.

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