Just to add, that with 9mm of peak-to-peak travel and 75cm path difference and 200mm height above floor the output would 100db at 20Hz. That might even be useable as the slots are roughly 1/2 SD, which lowers the resonance frequency, effectively making the cone heavier (yes..).
Funny you should mention that. Eventually I ended up with those 4 Beymas and am in fact working on a system. OB bass with 2 per side, with a 6/2,5/0,8 top.
I can confirm, based on both measurements and some listening on an improvised U-baffle, that 12BR70 works very well in OB. The initial measurements are lost (disk gone bad) but I will document the new process. The usual bottleneck is the woodwork, delaying the process already for too long...
Measured T/S agree with 31 Hz Fs and Qt of 0,55.
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egert, I really do recommend that youdo a quick and dirty prototype fist!
Your plans give me questions about sound radiation pattern matching, making it very difficult to get good balance between direct and reflected sound in the room... Also physical dimensions and shape look - well, strange, to me...
Beoplay A9 is nice to my eyes, because it is so simple. It il also monopole which works actually very well in most rooms, unlike dipoles that need more space to breath right.
Your plans give me questions about sound radiation pattern matching, making it very difficult to get good balance between direct and reflected sound in the room... Also physical dimensions and shape look - well, strange, to me...
Beoplay A9 is nice to my eyes, because it is so simple. It il also monopole which works actually very well in most rooms, unlike dipoles that need more space to breath right.
Thank you, Juhazi. I really appreciate your help, which may very well be keeping me out of trouble - spending good money on a faulty design. I have been ruminating about following the same principles as Aino and getting cardioid response, but have not gone that route since the CF10 midranges I have cannot go low enough at louder volumes due to lower SD, no excursion to speak of and smaller path difference. I do not want to spend additional funds on a midrange as at my normal "high" listening levels its distortion in the 150 - ~800Hz band is unmeasurable.
Just for reference, i have added my current sketch of the internals for the A9-esque solution. I would be completely happy to start meddling with it if I can lean on "higher authority" for assurance 🙂
As a general comment about the A9, i would say that the design lends itself well to open baffle solutions. Of course, unless using small drivers, it would be very difficult to achieve the super-slim looks of the A9, but i think that can be addressed with stretching a fabric over the rear, which would just leave the back of the horn sticking out.
Just for reference, i have added my current sketch of the internals for the A9-esque solution. I would be completely happy to start meddling with it if I can lean on "higher authority" for assurance 🙂
As a general comment about the A9, i would say that the design lends itself well to open baffle solutions. Of course, unless using small drivers, it would be very difficult to achieve the super-slim looks of the A9, but i think that can be addressed with stretching a fabric over the rear, which would just leave the back of the horn sticking out.
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I would think it is also a question of vibration as usually the rigidity and weight of the baffle are interlinked.
Extra distortion and random resonances most likely. I don't remember seeing a test with flimsy vs. ridig baffle of OB.
Nude mid/tweeter driver hanging on wires/strings is rather popular but I don't like the idea.
Nude mid/tweeter driver hanging on wires/strings is rather popular but I don't like the idea.
That would certainly lead to rather high distortions. It would not only flex but also move as a whole with unpredictable sound output of the baffle as a result.
Just go to a hardware store and get some thick oak countertop board.
Looks nice, easy to finish, will probably not vibrate at all no matter what, far less work.
Then you can have everything "like regular" on the front, no problem.
Looks nice, easy to finish, will probably not vibrate at all no matter what, far less work.
Then you can have everything "like regular" on the front, no problem.
That is one way to go. I have the CF10s hanging on a rope right now, no baffle at all. That is fine with a 20g cone travelling 1mm one way. At 100hz that can move the 5kg driver 4 microns. So no prob there.
I also had 4x12 inch woofers on ropes, those did move. Very little, but definitely did. That was 50g vs 2.5kg. So 200g vs 10kg of a large driver would do the same.
Adding weight on the back of the driver can help. But... Its easier to do a heavy baffle 🙂