Bipole or Dipole and the design

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ttan98

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Bipole or Dipole and the design
« on: 13 Jan 2011, 06:04 am »
I like to design a dipole with 2 full range drivers(each is 4ohm) mounted back to back and wired them in series and out of phase. Both of the drivers are mounted on a sealed enclosure. I think that would make the setup a dipole instead of a bipole.

If I have only a single driver on a sealed enclosure the capacity is about 4litre to give me a -3dB of about 90Hz. If I increase to 2 drivers do I double the capacity or still remain at 4litre to give me the same bass roll off. 

I would appreciate a response.

Duke

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Re: Bipole or Dipole and the design
« Reply #1 on: 13 Jan 2011, 06:56 am »
A dipole will roll off a lot higher than a monopole in general, and two woofers wired in a dipole configuration sharing the same internal airspace is something that I have no experience with.  So unfortunately I cannot advise you on an internal volume that will give you the same bass rolloff as a single driver in monopole configuration. 

JLM

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Re: Bipole or Dipole and the design
« Reply #2 on: 18 Jan 2011, 08:45 pm »
Why not provide separate enclosures for each driver?

And why not use separate binding posts so you can play with both dipole  and bipole configurations?

Duke

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Re: Bipole or Dipole and the design
« Reply #3 on: 18 Jan 2011, 09:01 pm »
Why not provide separate enclosures for each driver?

And why not use separate binding posts so you can play with both dipole  and bipole configurations?

Maybe that's what ttan98 meant, and I misunderstood.   In that case, he'd probably want each woofer to have roughly the same internal volume as a single monopole woofer, but he'd still have dipole cancellation in the bass region working against him.  However in the bipole configuration, he'll have a net increase of bass energy relative to the rest of the spectrum because the output of the rear-facing driver will add in semi-random phase in the midrange and treble regions, but will add in-phase in the bass region.  You don't want to start out with a woofer/box combination that has an upper bass bump and then bipole it, because you'll probably end up with too much upper bass energy. 
« Last Edit: 18 Jan 2011, 11:15 pm by Duke »