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Loudspeaker Configuration (Ohms)

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acvegas View Drop Down
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    Posted: 25 December 2016 at 8:07pm
Designing Speaker System (Advice Needed/Newbie)


If I have a 700 Watt Stereo Power Amplifier (350 Watts Per Channel).  I wish to wire a total of 8 speakers (4 Woofers each at 8 Ohms going to an inductor crossover & 4 Midrange Speakers each at 8 Ohms going through a 400 Volt Film Capacitor crossover) all together within one single speaker cabinet.  How should I wire/configure this without overloading my power amplifier?

1. Woofer: Out of the four woofers (each 8 ohms) – can I safely wire each “pair” of woofers in series going to the amplifier; which will give me 4 ohms?

and in addition to the above within one single speaker cabinet; can I also wire the following:

1. Midrange: Out of the four midranges (each 8 ohms) – can I safely wire each “pair” of midranges in series going to the amplifier; also, which will give me 4 ohms?  NOTE: Please keep in mind that ALL of the midrange speakers are going to 400 Volt Film Capacitor …..does this effect impedance/ohmages?


Now with everything as outlined above give me a total combined ohmage of 4 Ohms or 2 Ohms?

*********************

My second option would be to connect all of the four 8 ohm Woofers in series together and all of the four 8 ohm Midranges together going together into one amplifier terminal which will give me a total speaker ohmage of 16 ohms?

*************************

So what is my best solution for this speaker configuration without overloading my amplifier?

Thanks everyone for your assistance.

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Conanski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 26 December 2016 at 12:40am
Merry Christmas

OK.. First the basics.. four 8ohm speakers in series is a 32ohm load. If you wire pairs in series and then connect those pairs in parallel you get 8ohms which will be safe for you amplifier.

An 8ohm low load plus an 8ohm mid load is still considered an 8ohm load overall because the two driver clusters technically cover different frequency ranges, but there will be a lot of overlap in what they cover with your proposed bare bones crossover so it's hard to say what you will actually get.

Next.. 1 inductor and 1 capacitor does not make a crossover. This will deliver very poor performance by professional speaker system standards. And you will have to spend some good money to get components that will survive these power levels an active crossover and a separate amplifier would do a much better job.

You can put low and mid drivers in the same cabinet but they must be in separate sub chambers otherwise the low drivers will destroy the mid drivers and low frequency performance will suffer. If however the mid drivers are sealed or are horns ignore the above.

Edited by Conanski - 26 December 2016 at 12:47am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TMH Music Quote  Post ReplyReply Direct Link To This Post Posted: 26 December 2016 at 2:33pm
Originally posted by Conanski Conanski wrote:

Merry Christmas

OK.. First the basics.. four 8ohm speakers in series is a 32ohm load. If you wire pairs in series and then connect those pairs in parallel you get 8ohms which will be safe for you amplifier.

An 8ohm low load plus an 8ohm mid load is still considered an 8ohm load overall because the two driver clusters technically cover different frequency ranges, but there will be a lot of overlap in what they cover with your proposed bare bones crossover so it's hard to say what you will actually get.

Next.. 1 inductor and 1 capacitor does not make a crossover. This will deliver very poor performance by professional speaker system standards. And you will have to spend some good money to get components that will survive these power levels an active crossover and a separate amplifier would do a much better job.

You can put low and mid drivers in the same cabinet but they must be in separate sub chambers otherwise the low drivers will destroy the mid drivers and low frequency performance will suffer. If however the mid drivers are sealed or are horns ignore the above.


+1, some good advice here.
@acvegas, some more detailed information on your amp and speakers would be good. Like what make and model is your power amp and speakers? You talk about putting all 8 speakers in one box; would this be the only speaker cabinet, I.e, in effect, a mono stack? That's fine if it is the case, but you have a stereo amp. You could use one side of your amp to drive the bass speakers and the other side to drive the mids, using an active crossover, before the amp. As mentioned above, designing a decent, high powered, passive crossover i.e one that uses inductors and capacitors, can be a very hit and miss and expensive affair, something that is only contemplated by highly experienced speaker designers, with access to some very esoteric electro-acoustic measuring equipment and lots of time available, to build prototypes, test them, then re-design, over and over again!!

FWIW, my 2c, go active.
Nothing is foolproof because fools are so ingenious
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Post Options Post Options   Thanks (0) Thanks(0)   Quote markie Quote  Post ReplyReply Direct Link To This Post Posted: 26 December 2016 at 4:31pm
You haven't mentioned the top end? When you say "mid drivers" are they drivers in the sense of cone speakers or are they compression drivers. If they are the former do they have sealed backs or an open chassis? If they are sealed back then they will be OK in the same cabinet, but if not you will need to build separate chambers as above.

If you really want to stay with a single cabinet,  then you can still  run them as 2 pairs, i.e.  2 bass drivers and 2 "mids" per side but you will need a PROPER passive crossover to separate the frequencies. Powered this way will give a 4 ohm impedence per side. You will need to design the crossovers for 4 ohm load.

The best way to do this is with an active crossover but will your amp cope with a 2 ohm load? If not you will either have to:-

1). Wire in series/parallel as mentioned above, but this will reduce the amp power as the load will be 8 ohms. You'll probably find that your amp is 350 a side into 4 ohms, so will probably only give 200 a side(ish) into 8.

2). Get a second amplifier. Run 2 pairs of bass drivers per side on the main amp, and 2 mids per side on the second amp. The second amp doesn't have to be as big, but that will depend on the crossover point.


Edited by markie - 26 December 2016 at 4:31pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote markie Quote  Post ReplyReply Direct Link To This Post Posted: 26 December 2016 at 4:35pm
Incidentally connecting 4 8 ohm drivers in series will give 32 ohms, not 16.
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