Bohlender Graebener RD50 transducers advice

Hey, in a small town in Sweden there was an auction house selling assorted knick knacks on regular basis.
For some reason these ended up there and I bought them mostly out of curiosity.

Now I sit with these behemoths and no clue what to do with them.

Does anyone have any advice? I cant seem to find any diy plans using them.

I have managed to find out that I need something for around 500hz and lower.

Is it even possible to build something slim and discrete for the living room with these? :) P_20240526_135310.jpg
 
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Mount them on a panel with no enclosure, cross them at around 1,000Hz (less is better, but they sometimes buzz at lower frequencies) to a pair of 8" woofers in a slim sealed box and enjoy. The BGs sound amazing open baffle. BG also lists a contour circuit to get rid of the cavity resonance but I preferred running my RD48s without it.
 
These panels can be given an open-type acoustic design with variable acoustic load and thus “smear” the main resonance of the panel. You will need two pieces of plywood 4mm thick.
Then you can try 500-600Hz below.
 

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Sound reflected from the back wall won't mess anything up?
Typically dipole speakers are at least 3 feet out into the room to increase the delay between direct and reflected sound.

https://www.linkwitzlab.com/listening_room.htm

If you want to run them in a shallow enclosure up against a wall, that is also possible, but you'll need effective acoustic absorption inside the enclosure to prevent the rear wave from bouncing back and transmitting right through the diaphragm. This is a larger problem on planar speakers since the diaphragm is so light and thin.

A couple enclosed examples:
https://www.diyaudio.com/community/...bener-rd50-planar-magnetic-transducer.364008/
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https://www.diyaudio.com/community/...ilt-around-bohlender-graebener-rd-50s.362424/
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Whatever you decide to do with them, I'd test them before building anything elaborate. If you want to try dipole, test baffles for those can be low mass without a big impact on sound. Fome-Cor, cardboard, whatever is easier for you is OK. You can also hang them from a door frame, etc. for these tests.
 
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Ok, 3ft can be arranged if I have them in my hobby room in the cellar but if I want them upstairs I need to make them discrete and definitely in an enclosure.

I have seen an commercial product using them in an enclosure and one (or two) 6.6" in a box doubling as a foundation for the speaker.

I still havn't figured out what direction they are facing.
 
BG used to sell a speaker based on this driver. Open baffle down to ~400hz, then a small sealed box with a 6(?)" woofer. Called the Radia 520 or something like that. I used to have a pair, sounded great, but needed a sub and a little boost at highest frequencies as they started rolling off around 12kHz.
BG speaker.PNG
 
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You are lucky to have found these drivers, which are getting rarer. I have also listened to the B&G Radia 520i in the past and somewhat agree with what John Atkinson wrote: "This balance correlates with the presence-region dip and the slight excess of energy in the mid-treble in the in-room response, my ear latching on to the latter as brightness rather than on to the former as a lack of presence." "Lack of air" also noted from top-end drop-off.

It is frustrating because the planar drivers are obviously well made and their sound often shows so much potential, but the above issues and the integration issue with bass drivers can become very time-consuming and present many "close but no cigar" results. Look at the Herculean efforts put out by Wisdom Audio M75, which needed a pretty sophisticated active "brain" to try to overcome some of the issues.

Having said that, I would put the planars on open baffle and try to find some fast woofers, not too large maybe in 7-8" range.

WisdomM75.JPG
 
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It sounds like they won't be upstairs then :)

But open baffle makes it easier and if I can't get any good results I can always sell them to someone else.
It was a spur of the moment purchase anyway so I won't shed any tears over it :)
 
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Hey, in a small town in Sweden there was an auction house selling assorted knick knacks on regular basis.
For some reason these ended up there and I bought them mostly out of curiosity.

Now I sit with these behemoths and no clue what to do with them.

Does anyone have any advice? I cant seem to find any diy plans using them.

I have managed to find out that I need something for around 500hz and lower.

Is it even possible to build something slim and discrete for the living room with these? :) View attachment 1314510
My advice is to sell them to me.
 
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I have a pair of these drivers collecting dust. Couldn't I use them?
They are salvaged from subwoofers but they go up to 600hz according to datasheets at least.
https://loudspeakerdatabase.com/TangBand/WT-644F
Those drivers don't have high QTS for open baffle use, so you need to stuff them in a box. Do you still have the old sub cabinets or able to make/get boxes? If so, I don't see why you can't give it a try, provided you have some means to provide crossover, e.g. passive, analogue/digital active, etc.
 
No boxes of crossovers but boxes are easy.
It is the crossovers that will take some time.
I have only copied other peoples designs so I know nothing about them.

But I guss that I need one that filters away anything below 500hz from the transducer and another that does the opposite from the woofer.
 
That easy?
Sound reflected from the back wall won't mess anything up?
As someone else said, they will sound best at least a meter from the back wall. I ran mine open baffle with a 900Hz 4th order DSP crossover and about 1.5 meters from the back wall . My baffle was tapered from top to bottom; about 300mm wide at the top and 500 wide at the bottom. I also tried them with a rear chamber but I did not like the sound as much as OB. It's very easy to try.

Note that Carver ran them open baffle and very close to the edge of the baffle in the Amazing Loudspeaker. Mine were the the RD48s, designed for that exact speaker and yours are similar; just 2" taller.
 
I can't believe I also have some experience with Carver Platinum speakers. Now there was a speaker system with potential to go head-to-head with the heavy hitters at very reasonable price, but their sound quality really depended on the room size and shape, and many users simply could never get them to sound good in their room, especially the planar-to-bass balance, and they needed amps with lots of power and current.
The best results I have heard were when the passive crossovers were bypassed and outboard active analogue crossover was used with 4 channels of amplification. The woofers usually needed replacement after some years, or at least foam surrounds replaced.
THEN, in the right room, they could really sound AMAZING!

Carver.PNG
 
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