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Old 4th December 2012, 09:03 AM   #151
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You can still hang the RD-40 below the upper woofer. My idea is:
Make two W-baffles like the Orion-3.4 with two 10" woofers, one baffle for the upper and one for the lower woofers. Use four slim poles between the two woofer baffles. Hang the RD-40 in the upper baffle. Simple!
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Old 4th December 2012, 09:19 AM   #152
lolo is offline lolo  France
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I see! Will have to pass the UN (read my wife..) vote though..

Remember I don't have a dedicated room like yours..
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Old 4th December 2012, 12:20 PM   #153
opc is offline opc  Canada
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Quote:
Originally Posted by lolo View Post
I see! Will have to pass the UN (read my wife..) vote though..

Remember I don't have a dedicated room like yours..
I'm in the same boat as you lolo... my main system is in our main living space, which is why dipoles (and massive 18" H-frames) are just not going to be an option.

Quote:
Originally Posted by StigErik View Post
I did not return the drivers - too costly to ship them back and forth across the Atlantic.

I never really found the real source of the buzzing, but I discovered that applying pressure to the front waveguide stopped it. It seems that the buzzing has little to do with the ribbon itself, but rather a mechanical problem with the waveguide. Anyway - installing a clamp solved the problem...
Thanks!!! I'll give this a try and see if it helps. I was also pondering filling the empty channel behind the waveguide with expanding sprayfoam. Having a hollow metal channel that length somehow seems to be asking for trouble. On the same note, I suppose an intelligent application of this stuff could be the ticket:

Sonic Barrier Lightweight Vinyl Sound Damping Sheet 27" x 40 268-035

I've used it on metal chassis before and it works wonders in terms of deadening resonance.

I also have one more question for StigErik:

If you were talking to someone who is used to equalized sealed boxes that have good output down to 30Hz, how would you describe the output capabilities of the 18"-21" H-frame arrangement?

I was very close to pulling the trigger on a quad of the Goldwood 18" drivers to build some H-frames (MJK style) just to see, but I can't imagine how you can get any SPL from such a system. You've only got a few mm of excursion, and they are painfully inefficient at lower frequencies.

Do you need 12 x 21" drivers like you have to get decent output, or would 4 x 18" work reasonably well?

I don't want to downgrade in terms of output and LF extension, but I would love to hear what everyone is on about with this dipole non-sense

Cheers,
Owen
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Old 4th December 2012, 12:32 PM   #154
lolo is offline lolo  France
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Owen, whilst you are here.. I haven't had the time yet to start the Wire, remember I took 10 boards off you.. I hope to get into it soon!
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Old 4th December 2012, 12:51 PM   #155
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You can calculate max SPL using Linkwitz' excel spreadsheet.

www.linkwitzlab.com/spl_max1.xls

In my opinion, a single 21" in H-frame will give sufficient SPL down to 30 Hz at least, comparable to a 12" in closed box.

To get low distortion however, you need to keep cone excursion low, and that requires massive cone area.
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Old 4th December 2012, 10:18 PM   #156
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Default Grand Orgue

What about RD-50/40 with something like this:

GRAND ORGUE

..substituting the middle row of full rangers with the RD-*..?
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Old 12th December 2012, 01:45 AM   #157
gworrel is offline gworrel  United States
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StigErik,

I want to thank you for your posts here which I discovered within the last year and which prompted me to push ahead with my own RD-75 system. I bought the RD-75s used about 10 years ago but they had been sitting. I had planned a more involved frame to support the RD-75s but when I saw your hanging method, I thought, that looks easy, I can do that.

I used some 15" TC-Sounds Aluminum cone woofers which had been offered at a great discount some years ago to the dipole Yahoo list (if I remember right.) I am using a DBX Driverack PA for crossover and EQ. I am crossing over at 400Hz, LR24dB. I have a velodyne ULD-18 that I cross to at 50Hz. I could not be happier with how it sounds. I have yet to work on the room acoustics and surfaces so things are a bit rough looking in the pictures.

I have a more detailed write-up in a thread I started at http://www.htguide.com/forum/showthr...457#post564457

Greg

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Old 12th June 2013, 05:52 AM   #158
ds23man is offline ds23man  Netherlands
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Quote:
Originally Posted by opc View Post
Hi Guys,

I just received my pair of RD75 planars from PE over the weekend, and I'm excited to start measuring, testing and building!

I have access to a large anechoic chamber and some very good measurement gear, so I plan to run a full gamut of tests on these to see how they measure up. I'm particularly interested in THD performance and characterizing the 5kHz resonance.

Although I'm very intrigued by the idea of a dipole implementation, my listening space really isn't going to work very well for that as I don't have any space between the loudspeakers and rear wall. As a result, I'll be building an enclosure that follows the suggestions in the white paper as closely as possible (10" deep, 6" wide, very well braced and damped).

Has anyone here tried a sealed enclosure? Any success or suggestion?

StigErik:

A while back in this thread or your other one, you mentioned that one of your two ribbons was buzzing, and that you were looking at returning it. After that, you never really mentioned it again.

Can I ask how you resolved the issue? One of my two ribbons is buzzing about 1/3 of the way down form the top at frequencies between 1 and 3 kHz. I was running 1kHz tones to see if I could get a rough frequency response in-room and noticed it right away. It's less noticeable with music, but it's still there.

Did your buzz go away with time, or did you exchange your driver? I checked the driver closely and don't see any signs of damage, but I did notice the foam in the rear outlets was a bit uneven. I carefully straightened it with some plastic tweezers, thinking maybe it was contacting the diaphragm, but it didn't help.

Any suggestions on this would be appreciated

I'll keep everyone posted on the results.

Cheers,
Owen
Did you do some measurements?
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Old 12th June 2013, 06:02 AM   #159
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Hey Owen, really excited to see your measurements. I built a pair of GR Research Super Vs but am very curious about the dual RD-75 + open baffle sub method that StigErik is using. If I'm not mistaken, I thought I read that the foam baffle StigErik added to his RD-75's cut out the buzzing? Can't remember, will let him chime in on that one. Do post your results on this!

@gworrel, that's an awesome looking setup! Looks like you might be getting a little diffraction from the RD75's being placed a little behind the woofer towers? Thoughts?
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Old 13th June 2013, 09:41 AM   #160
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Quote:
Originally Posted by dkmooers View Post
thought I read that the foam baffle StigErik added to his RD-75's cut out the buzzing? Can't remember, will let him chime in on that one.
I added the foam baffle to round off the edges and reduce diffraction. It did not affect the buzzing.

I did add a clamp between the front and rear side of the driver at the point where the buzzing came from. This solved it, and over time the buzzing got away, and I removed the clamp. I have no answer to what was the the exact source of the buzz and why it want away.
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