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Old 22nd May 2005, 09:31 AM   #1
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Default KEF B139 as subwoofer

I have a couple of these, which I could either sell if anyone is interested, or otherwise build subs with. I don't have space for a TL, so the sub would have to be IB or ported. Can anybody point me to a functional design that's as small as possible? I don't mind flat to 40hZ - don't listen to organ music and low E on the double bass is the lowest note I'm interested in. Thanks for all suggestions. Andy
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Old 22nd May 2005, 12:29 PM   #2
Rudolf is offline Rudolf  Germany
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Default Re: KEF B139 as subwoofer

Quote:
Originally posted by andyjevans
Can anybody point me to a functional design that's as small as possible?
You will not get smaller than this:
http://mitglied.lycos.de/MundU/audio/dipolsubwoofer.htm
Scroll down to "Dipol-Subwoofer mit KEF B139". The pictures speak for themselves. The SPL measurement is for the plain speaker @20cm distance without any filter or compensation. So two of these "boxes" with some gentle equalisation will give you very much of the bass you are looking for.

Rudolf
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Old 22nd May 2005, 12:58 PM   #3
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I've never seen a design like this. How does this dipole work - there's very little back resistance. Are the speakers in phase or in opposite phase? How do you get the bass extension - looks good on paper.
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Old 22nd May 2005, 01:52 PM   #4
Rudolf is offline Rudolf  Germany
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Andy,
welcome to the world of dipoles!

For the theory behind it look at
http://www.linkwitzlab.com/models.htm

Regarding the design of these W dipoles:
http://www.linkwitzlab.com/woofer.htm

There is a lot of information in this forum if you search for "dipole", "W baffle" or even "ripole".
All your questions will be answered - and many more asked

And please - donīt blame me if you get hooked
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Old 22nd May 2005, 02:03 PM   #5
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This looks good - not too big, flat response. If it's so good why don't more commercial designs use it?
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Old 22nd May 2005, 03:43 PM   #6
Rudolf is offline Rudolf  Germany
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Quote:
Originally posted by andyjevans
This looks good - not too big, flat response. If it's so good why don't more commercial designs use it?
Some things to consider: Because dipoles are velocity transducers and not pressure transducers like CB, BR, TMLs and Horns,
- they donīt work near a wall (keep them at least 1 m from the backwall)
- they donīt give that pressure punch in the stomach many people associate with "good" bass response and
- their acoustical efficiency is somewhat about a quarter of that of a BR, so you need drivers that can move much air.
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Old 2nd November 2005, 10:00 AM   #7
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Default KEF B139 as subwoofer

I have looked at the pictures and the dipole sub is very compact indeed. I am considering crossing this over (active) at 300Hz to a set of B-G 28 ribbons, but I don't have the exact dimensions of the sub shown in the pictures.

I understand the principle of the folded baffle dipole sub, but not sure of the effect of changing the dimensions will have on the frequency response. I like the response curves shown and if anybody out there has the exact dimensions, please send them to me.

Regards

Nigelnog
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Old 6th November 2005, 10:15 PM   #8
BAM is offline BAM
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Old 6th November 2005, 11:14 PM   #9
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Quote:
Originally posted by BAM
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Google.de ist Ihr Freund:

http://www.tech-diy.com/Dipol-Subwoofer.pdf
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Old 6th November 2005, 11:22 PM   #10
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Can I second the request for dimensions please. The pics are very pretty, but not really that informative.
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