B&G RD-75 dipole - baffle and or waveguide?

[maestrok1]

Awesome I really appreciate your help StigErik. I have a lot of ideas that I want to try in the next couple of months. I am going to try a Gilmore audio raptor which is ice power, because I have heard a few people that owned Atma-Sphere otl thought the ice power amp was on par with the otl's, but with none of the tube draw backs. Right now I have Transcendent Sound Otl which I intended to run with the Beyma tpl-150h and a 12 inch driver all actively crossed over with a marchand xm-44. I haven't heard them yet because I haven't built boxes for them. I followed your past posts on the Beyma tpl-150 so when I saw that you switched to the Rd75 Drivers that really piqued my interest because I have always wanted to try them, but haven't because I haven't found any solid state amplifiers I like yet. I'm always willing to give new things a try. I am going to order in the gilmore amplifier and try it on a 30 day trial. In the end I will probably only keep one set up, either the beyma or the bohlender.

[Vadim]

Hopefully I am not steeling this informative thread, but I also did benefit from the work done by Rudi Blondia and John Whittaker. And much like Carl Huff, I also built an airfoil baffle for RD-75. Here are the pictures.



and



I then shamelessly borrowed ideas from Linkwitz and utilized his Phoenix W-woofers with Peerless XLS 830500 12-inch drivers wired in parallel. The midrange array consisting of 4 Scan Speak 10-inch drivers, the 25W/8565 in copy of Phoenix baffles.

Over the years I used a several crossover ideas, ranging from an analog circuit, to what is currently a DCX2496 digital implementation. Right now I am looking at Minidsp 4x10 or even 10x10 stand alone box. It seems like a way to go; particularly that it has an integral volume control. I do not like the DCX, as is, too flaky and I have no desire to mod it. Minidsp looks better to me.

Anyway, I would love to hear and learn what others have done in the cross-over area.

Best regards,
Vadim

[SpinMonster]

Vadim, a most beautiful system. I dont think I can fit it though. My room is 21x21 but I have a 16 foot diag screen that would leave them tucked into a corner without much room to breath. Unless I use 9 - 8"woofers on the same panel.

What is your screen size and room dimensions?

[Vadim]

SpinMonster,

Thank you for the kind words. My room is not great these days, - it is about the same as yours, a bit longer but also a bit narrower. My screen is 'only' 104 inches wide. I have been using Front Projectors for the past 20 years and next year will be the last. Went from 9-inch CRT to DLA RS-2 over the years. I am going to to go with a 80-inch wide LED screen and concentrate more on audio.

Right now I am setting out to start build new amps soon and am re-thinking the crossover for my front dipoles, -hence I am looking at the MiniDSP.

It seems that the 10x10 box is a good deal here, but I have yet to hear from anyone who has used it. I need to integrate my right and left 3-way dipoles with a single stand alone subwoofer. It is a DIY sealed sonosub with two 15-inch Avalanch drivers. I also have centre and rear channels, but at least I do not need a crossover for them. My only active speakers are the 3-way dipoles in the pictures I posted.

All in all, I have 10 channels to worry about. So, - the question is can this MiniDsp 10x10box do it all? Volume control is really attractive there. It seems like it can, but I am not sure. I have this crazy idea of simply using my DVD player with a built in decoder and avoid a need for a separate processor. I am doing it now, but its a cludge and am trying to improve the set-up.

Sorry for taking this thread off topic.

[Carl_Huff]

Vadim,

Your loudspeakers are a beautiful piece of art. They are much nicer than mine. Mine are black enamel paint! Great job and kudos to you.

As to crossover I originally used the custom active crossover designed sold by Rudi Blondia specifically for the RD75. However most recently I swapped that out for the active crossovers and EQ that are in the Datasat RS20i. Both solutions worked very well form me.

[Vadim]

Carl,
Thank you...yes, I heard of rs20i. It cost as much as one of my cars! Naturally MiniDsp is a lot more economical. I had build an analog crossover for my dipoles years ago. It was a rather big circuit. The problem is, it is a pain to tweak. Well, - currently I am thinking of a part DIY and part commertial implementation.

Ideally I would like to have a digital in-digital out crossover, so that I can do my own DACs. It seems that the MiniDsp just has the DSP engine and will serve me well in interim until I figure out how to get to the output digital signals inside it. I was going to do the same with my dcx2496 unit, but it was way to flaky for me.

Both the 10x10 and 4x10 units from minidsp look very promising to me and overall look better then the dcx.
Question, does Rudi publish schematics for his crossover? I'll be interested to see his implementation and possibly follow his circuit digitally.

My analog crossover had a requsite 5-6 db notch at 5k and a high frequency boost of about 12 dB at near 20 kHz. I used gurator configurations. Crossover was around 450 Hz to midrange, L-R 4th order. Now I want to change those parameters to see what happence , so DSP approach is a must.

[StigErik]

With a short listening distance I found that a baffle is really not necessary, and I XO at 180 Hz. With greater distance, the level below 1 kHz will roll off, and to compensate a baffle will be necessary.

I run an all-digital computer-based XO and EQ solution, and the digital output is fed to a multi-channel DAC.

I also have a dip around 5 kHz and 12 dB boost at 20 k.

[Carl_Huff]

"Question, does Rudi publish schematics for his crossover? I'll be interested to see his implementation and possibly follow his circuit digitally."

To the best of my knowledge Rudi never made public a schematic of his Clearview CXR crossovers.

However I can tell you that they were well done and a very dense circuit with many OP275 opamps in it.

I only abandoned my Clearview xover after I had access to a more flexible digital technology.

[Vadim]

Originally Posted by StigErik

With a short listening distance I found that a baffle is really not necessary, and I XO at 180 Hz. With greater distance, the level below 1 kHz will roll off, and to compensate a baffle will be necessary.

I run an all-digital computer-based XO and EQ solution, and the digital output is fed to a multi-channel DAC.

I also have a dip around 5 kHz and 12 dB boost at 20 k.

Yes, I understand and I agree that you can do without a baffle, as long as you are willing to live with rather high roll off. I wanted to use 10-inch drivers for my mid-range, so at most I needed to place the crossover around 500 Hz and my baffle can support that. You probably are using 8-inch drivers.

Erik, I wonder if you could describe your PC-based crossover in some detail. I would like to know what software you are using and what are the computer requarements? Also, - how many channels are possible? Am I to understand that you are running multiple SPDI/F outputs out of your PC? Can you do AC-3 5.1 format? I just might go the same route. Thank you.

[Vadim]

Originally Posted by Carl_Huff

"Question, does Rudi publish schematics for his crossover? I'll be interested to see his implementation and possibly follow his circuit digitally."

To the best of my knowledge Rudi never made public a schematic of his Clearview CXR crossovers.

However I can tell you that they were well done and a very dense circuit with many OP275 opamps in it.

I only abandoned my Clearview xover after I had access to a more flexible digital technology.

Carl,

I can imagine what Rudi did. Actually it was not all that bad. I had a similar circuit, I am sure of it. But, yes, it was rather large and all digital solution is preferable. I am now thinking PC-based approach, - will see...