Corner Dipole Woofer (CDW): info? anyone tried one?

Hi everyone, I just moved into a new place and my listening room is:

11 ft wide by 7.75 ft high by 13.5 ft long (~1150 cubic feet).

Because of furniture restraints, I will be sitting quite close to the front wall with places me at 45 degrees from the corners.

Hmmm … corners … 45 degrees … that reminds me of something … I know, that weird corner baffle posted on the linkwitz site:

Discussed briefly at question #30

Frequently Asked Questions

Picture here:

http://www.linkwitzlab.com/images/graphics/corner-dp.gif


I want to use it from 40Hz to 200Hz. I will have one (or two) Audax PR170MO with super tweeter on an open baffle covering from 200Hz up.


Does anyone have any info on the CDW?

Has anyone tried them? How are they?

Thanks for the help,
Jeff
 

dwk123

Member
2002-02-06 4:51 pm
I'm playing around with similar but not identical ideas. The setup in Linkwitz drawings will have nulls at +` 22.5 degrees from the walls. Unfortunately, my listening position is at about 20-degrees, so it won't work.

I did do some quick experiments with a flat baffle coming straight out of the corners at 45-degrees. This actually sounded really good, but bottomed my woofers (nht 1259's - for testing, not expecting them to 'work' in the final setup) really easily. Not surprising, as the 'd' parameter gets 'foreshortened' by the sin of the angle of tilt, so the effective baffle width is pretty small in this case. I believe the setup Linkwitz illustrates will have the same problem, although keep in mind that you do get a boost of sorts by firing into 1/8 space which partially offsets the shorter baffle.

My next test was to place the flat baffle about 3' up the wall tilted at 45 degrees back away from the listening position. This formed a resonant chamber (since my speakers were on a platform on top of the dipole baffle) behind the driver, and didn't work too well. I'm guessing that if youi can go 3' up the side, a conventional H baffle would be the best idea.

If you have enough displacement - an Avalance 15 or 18 per side (or two!), I think the corner dipole thing can work ok. I'm trying to figure out a good way to use two 15's in my 'flat baffle' approach. Something like the 'ripole' idea (basically a modified W baffle) might work, but might be physically cumbersome to squeeze into a corner.

BTW - I'm crossing at around 80 right now. I dont' know that this type of approach will work up to 200Hz. Woofers that have enough volume displacement to make this work may not work that well to 200Hz, even apart from the dipole resonances etc that may show up.
 
Jeff,

>I want to use it from 40Hz to 200Hz. I will have one (or two) >Audax PR170MO with super tweeter on an open baffle covering >from 200Hz up.

>Does anyone have any info on the CDW?

>Has anyone tried them? How are they?

Yep, and very good they are too!

See:

http://www.kingdom.uk.com/jdfiles/side_open_right_full.jpg

http://www.kingdom.uk.com/jdfiles/in_room_close_full1.jpg

They dipoles are high passed at 160hz, and are pretyy flat to 30hz, rolling off rapidly after that.

I did try the final piece of baffle into the corner as per LS diagram, but to be honest it didn't really add anything.

The only other issue I would say, is that you have a failrly small room, and you may well have problems with a dipole mid, especially if they are used tight into the corners. I much favour the directive mid/high's as provided by the front horn than a dipole mid.

Regards,

Jonathan
 
Reanimating a very old thread (but the only one related to the issue imho).
There is a new contender for the most ingenious dipole concept:

More info and pictures on the Gradient Helsinki website

Some speculations regarding this alien speaker have already started at audioasylum
 

Attachments

  • uutiskuva.php.jpeg
    uutiskuva.php.jpeg
    22.3 KB · Views: 1,446
I don't like the pressurisation caused by a sealed box, I find open baffle speakers more comfortable on my ears. I'm also interested by this from Siegfried Linkwitz:
" A dipole placed in a room corner should provide minimal excitation of room modes or resonances. The corner is a region of maximum sound pressure and it is well known that a typical monopole woofer in this location will couple optimally to all room modes. A monopole woofer would be a high impedance pressure source in the high impedance region of all wave modes (Z = p/v) and be optimally adapted to support them. A corner dipole, being a velocity and low impedance source, would have minimal coupling to room modes."
 
I don't like the pressurisation caused by a sealed box, I find open baffle speakers more comfortable on my ears. I'm also interested by this from Siegfried Linkwitz:
" A dipole placed in a room corner should provide minimal excitation of room modes or resonances. The corner is a region of maximum sound pressure and it is well known that a typical monopole woofer in this location will couple optimally to all room modes. A monopole woofer would be a high impedance pressure source in the high impedance region of all wave modes (Z = p/v) and be optimally adapted to support them. A corner dipole, being a velocity and low impedance source, would have minimal coupling to room modes."

SL once provided a drawing of a corner dipole: a driver on a planar baffle coming out from the room corner at a 45 degree angle. This might be something to try (I have not, personally) with a floor-to-ceiling baffle and a couple of drivers as far back into the corner as possible. There will be a resonance formed and the structure will need some mass and bracing because there won't be any force cancellation of the cone motion.
 
I just can't see any point/benefit in putting a dipole in the corner. Even less the double system. Yes, the walls amplify sound, but it still has dipole loss towards lower frequencies. With smaller wavelengths summation gets messed with reflections and response starts to look like the edge of a saw, with phase variations... Easily the strongest, reflected but amplified impulse is late in time domain and in wrong polarity which causes a deep dips in response. Reversing polarity of wires doesn't help because this frequency does not match with xo nor timing.

Gradient Helsinki or similar along the sidewall out of corner works better perhaps, but is very critical for placement, angle and distance to wall
- Gradient Helsinki 1.5 loudspeaker John Atkinson, November 2010 | Stereophile.com
 
Last edited:

AllenB

Moderator
Paid Member
2008-10-18 11:31 am
I don't like the pressurisation caused by a sealed box,
The pressurisation may produce 2HD, but so would the elevated excursion of an open baffle, not to mention 3HD.
A dipole placed in a room corner should provide minimal excitation of room modes or resonances.
Wouldn't the ideal be medium excitation? If you don't play the modes you can end up with holes.