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Gwho 20th January 2013 02:34 PM

Help with BG RD75 Monopole Speaker
Would like some help with building a monopole speaker with a BG RD75. I'm not much of a diy speaker builder so any info would be helpful. The monopole will be a center channel that will be sitting in front of and crossed over with a planar sub-woofer. I will likely use a minidsp to crossover between the monopole and sub-woofer. I'd like to crossover as low as possible (200hz?). The sub-woofer goes up to 350Hz.

I've tried to read through the thread on the dipole RD75 which seems to address a lot of the issues with reflection, cancellation, baffle size, and baffle edges. My guess is that a lot of these issues do not impact a monopole. What are the primary issues and secondary issues? I know I will need a notch filter to smooth out the response from reading the BG RD75 spec (I will implement this with the minidsp).

I'd like to build something looks similar to the Wisdom speaker that has a small horizontal footprint. Does anyone know the dimensions of this speaker at the top and base. Should the edges be rounded near the edge of the RD75? What interior volume do I need to get down to 200hz? How important is bracing and fill on the interior. Any suggestions on the construction and design would be much appreciated. Let me know if I need to provide further information.

I just want to thank you ahead of time for any help provided.


ds23man 21st January 2013 04:36 AM

2 Attachment(s)
My project:

StigErik 21st January 2013 06:57 AM

I'll be watching this thread, even if I'm a dipole guy ...

Gwho 21st January 2013 01:07 PM

Thanks for the pictures. Is there a minimum volume required. What kind of damping material did you use. What crossover frequency did you use? How does it sound?


ds23man 21st January 2013 01:33 PM


Originally Posted by Gwho (
Thanks for the pictures. Is there a minimum volume required. What kind of damping material did you use. What crossover frequency did you use? How does it sound?


There is a minimum volume mentioned in the spec sheet and the freq. plot is done with this enclosure. I am using a little bit less volume because I discovered this nice aluminium profiel ( used for advertising boards). Can not tell something about the sound, I am still in the building proces. It will be combined with JBL 2235 15" low drivers and will be powered with 4 Hypex Ncore's and DLCP

ds23man 21st January 2013 01:39 PM

3 Attachment(s)
More pictures:

Gwho 21st January 2013 03:26 PM

Thanks for the additional pictures. That is interesting. I will look into aluminium extrusions and see what is available out here.

StigErik - My main speakers are Dipole but the center channel will be sitting directly in front of a planar dipole speaker. My thought is if I made it a dipole there would be issues with the back wave.


AVWERK 21st January 2013 11:03 PM

You said this aluminum enclosure is used for advertising boards?
I have seen similiar shapes also for horizontal lighting fixtures.

Looks good and the internal shape benefits from non parallel surfaces.


Gwho 21st January 2013 11:28 PM

Any idea where they might sell something like this?


ds23man 22nd January 2013 04:37 AM


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