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
 
andyjevans said:
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
 
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 :rolleyes:

And please - don´t blame me if you get hooked :D
 
andyjevans said:
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 don´t work near a wall (keep them at least 1 m from the backwall)
- they don´t 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.
 
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
 
Hi sorry to dig up an old post, but was wondering if anyone had any success with building one of the subs or similar using a pair of b139's?

I was thinking of giving the above link a go, as it seems to be a fairly easy and cheap construct and might be suitable for my small room.
Any recommendation on measurements and wiring? If not I might just guesstimate.
 
I thought about doing one of those, but there a little too BIG for my allotted space......

Hi,
Here is an idea if you have measured similar T/S for two of your KeB139b drivers in an isobaric configuration:

b:)
 

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Hi sorry to dig up an old post, but was wondering if anyone had any success with building one of the subs or similar using a pair of b139's?

I was thinking of giving the above link a go, as it seems to be a fairly easy and cheap construct and might be suitable for my small room.
Any recommendation on measurements and wiring? If not I might just guesstimate.

Hi,

You might as well guestimate the dimensions, they are not critical.
Wiring and c/o depends how you intend to drive them, 4 ohm plate amp ?

rgds, sreten.
 
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

Sorry ol' chap but this unit cannot be used as a sub. (only > 28Hz)
 
Hi,

You might as well guestimate the dimensions, they are not critical.
Wiring and c/o depends how you intend to drive them, 4 ohm plate amp ?

rgds, sreten.

I only have odds and sods. An old Amber 17 preamp drives two intergrated amps, a Rocksan Caspian intergrated which drive a couple of old 8" Richard Allan full range in a DIY TQWT cabinet and a old TEAC AS-100 I was going to use for the KEF woofers......and I might add a couple of tweeters in as well.
I'm not technically savy so it will be pretty basic and may not be optimum, but will give me something to muck around with......and one day when I know more I'll do something a bit better.

What distance apart should they be? by the looks of the photos its around 4"
 
Well I went and built one (Dipol-Subwoofer mit KEF B139) out of 45mm ply, weighs a ton. Got it stuck in the only space I can find for now and have it hooked up to my Teac set on mono and the bass up and treb down until I can work out how to wire it up better.

Sorry for the lousy photo will post up a better one if anyone's interested.

Any advise on how to wire it would be appreciated, sorry I'm not tech savvy so you'll have to dumb it down for me .
 

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