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Dual driver subs impedance

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TomD View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TomD Quote  Post ReplyReply Direct Link To This Post Topic: Dual driver subs impedance
    Posted: 22 July 2006 at 2:03pm
Hi
If I want to build some 2x15" subs, and want the completed cabinet to end up at 8 ohms, what's the best way of going about this?

I could either use 2 4ohm drivers in series, or 2 16ohm paralleled. If, as an example, each driver was 1000w, what would the total rated power of the cabinet be in each case?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JD01 Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2006 at 3:56pm
In any case the rating will be 2000W.
 
The better way is to use two 16 ohms drivers in parallel. This is more reliable.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevinmcdonough Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2006 at 7:18am

I understand that by using parallel wiring the speakers will be more reliable, as one will still continue to play even if the other stops, but could this also be a downfall?

If one speaker suddenly stops working and the other is playing, then the playing one will suddenly find itself plaing with double the cabinate volume behind it which, i would guess, would mean it may blow as well?

At least in series, although you'd loose the volume from both drivers, you'd save the other driver from blowing?


kev


Edited by kevinmcdonough - 23 July 2006 at 7:18am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ben_Lawrance Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2006 at 10:40am

If one of your drivers blows whilst connected in parellel, the  the amplifer would then see 16ohms as opposed to 8ohms. Therefore reducing the power into the cab.

An amp that drives 2000w into 8ohms (is not just a big f**king amp) will drive 1000w into 16ohms.

How many amps out there will drive 2KW into 8ohms anyway?

Surely you'll be bridging the amp?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2006 at 12:00pm
When I built some twin 15" subs recently, I used seperate chambers for each driver so that if one blows the other will continue working normally.  The dividing piece also braces the cabinet in the middle.
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TomD View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TomD Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2006 at 12:45pm
They were hypothetical values, I'd probably be using something like 2x500/800w 16ohm parallel to make a total cabinet power handling of 1000/1500 watts.

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JD01 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JD01 Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2006 at 1:41pm
Originally posted by Ben_Lawrance Ben_Lawrance wrote:

How many amps out there will drive 2KW into 8ohms anyway?
I got one here....
 
 
Sometimes the coil of the speaker doesn't break the circuit when burnt, but short it. That means if you put two 4 ohm speakers in serial, and one fries, the other one would still run... at 4 ohms! So the ONE remaining speaker will get double the power the two speakers would get together, which would be around 3000W (for ONE speaker!). So it will blow easily.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote super-hero Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2006 at 4:18pm
I seem to recall reading somewhere that parallel is better, because of the affect it has on the amplifiers damping factor.
 
Someone else will know the specifics of this.
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JD01 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JD01 Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2006 at 9:48pm
This is just a rumor without any scientific background. It has no effect on the damping factor. I can't belive there are actually engineers believing that nonsense.
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TomD View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TomD Quote  Post ReplyReply Direct Link To This Post Posted: 24 July 2006 at 10:06am
Originally posted by JD01 JD01 wrote:

Sometimes the coil of the speaker doesn't break the circuit when burnt, but short it. That means if you put two 4 ohm speakers in serial, and one fries, the other one would still run... at 4 ohms!

But if this happened while in parallel, the amp will short.
I'm not really intending to be pushing drivers to breaking point, I was just confirming that two 1000w drivers in parallel would in fact result in a 2000w configuration.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote norty303 Quote  Post ReplyReply Direct Link To This Post Posted: 17 August 2006 at 1:10pm
I think its more relevant that the change in cab volume for the one remaining driver will have an effect.
 
When i blew my BP6 drivers and looked at the VC's, both had evidence of burnout, however only 1 had any marks to indicate hitting back plate. I presumed that once one went the other also burnt but spent some time over excursing beforehand
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom Umney Quote  Post ReplyReply Direct Link To This Post Posted: 17 August 2006 at 1:57pm
Two seperate chambers in the same box would be the key to using a dual driver sub.
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