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Old 31st July 2009, 08:00 PM   #1
jaekfre is offline jaekfre  United States
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Default Ok to wire line array in series? Why?

I can't find anything info dealing with this on diyaudio or any place else.

I've been told and read in many places that one should not wire two drivers in series because of the back EMF that it produces.

However, why is that one of the accepted ways of wiring line arrays?

Makes no sense to me. But of course, I'm new to speaker building.

Thanks in advance.
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Old 31st July 2009, 08:11 PM   #2
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Most people go for series/parallel groups that end up at 4-8ohm. This means the load on the amplifier is what it's designed for. If you had 9 8ohm speakers in series, you would end up at 72ohm, which the amp will drive, just very quietly.

So, to take the 9x 8ohm speakers, if you made 3 groups of parallels with 3 drivers each, you'd get an 8ohm load exactly (neat, huh?) and your amp would be fine with that.

If, however, you wired all the 9 speakers in parallel, you'd get a 0.9ohm load, which the amp wouldn't go well with. It would **try** to give 3x it's rated power (into 8ohm) into the speaker, which would lead to damage and nasty smells.

Basic rules (dunno if you know this, handy to have) calculating overall impedance:

two speakers in series: add the impedances together.
two speakers in parallel: (gets more complicated) you do 1/(1/R+1/R+1/R.....) where R is the impedance, and the number of 1/R s is how many speakers there is.

Hope this helps

Chris

PS - you shouldn't wire two *different* drivers in series, as bad things can happen (according to Dad, the electrical engineer, off whom I got the info for the impedance calculations).
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Old 31st July 2009, 08:28 PM   #3
slam is offline slam  United States
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I once opened up a McInstosh XRT-22 line array to fix a loose connection and found that the 23 tweeters were in a mixed parallel / series configuration to get to around 8 ohms.

BTW those speakers sound very good. So don't worry.
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Old 31st July 2009, 08:47 PM   #4
jaekfre is offline jaekfre  United States
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That makes sense.

But from what I've read is that no two drivers are identical - even though they be the 'same' driver from the same manufacture.

Supposedly, the slight variations will cause distortion because of back EMF.

Is this something that is theoretically true but not going to be a huge deal with just two of the 'same' drivers wired in series?
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Old 31st July 2009, 08:55 PM   #5
jaekfre is offline jaekfre  United States
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ok, i'm still in 'moderation mode' until i make some more posts so the lag in my posts showing up is pretty annoying!

anyway, thanks a lot guys for the replies.

guess i'll try some experimenting
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Old 31st July 2009, 08:57 PM   #6
jaekfre is offline jaekfre  United States
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Quote:
Originally posted by jaekfre
That makes sense.

But from what I've read is that no two drivers are identical - even though they be the 'same' driver from the same manufacture.

Supposedly, the slight variations will cause distortion because of back EMF.

Is this something that is theoretically true but not going to be a huge deal with just two of the 'same' drivers wired in series?

Slam - I posted the above before you replied to the thread.

You pretty much answered the question. Thanks again.
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Old 31st July 2009, 09:15 PM   #7
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Old 31st July 2009, 10:30 PM   #8
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yep series parallel works listening to 9 drivers sereis paralel right now:
+ 3 > 3 > 3 - It's just not sane to try and drive loads of less than an ohm!
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Old 3rd August 2009, 02:23 PM   #9
jaekfre is offline jaekfre  United States
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awesome! thanks kipman.
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Old 26th June 2013, 04:51 PM   #10
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thank,s for all
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