B&G RD-75 dipole - baffle and or waveguide? - Page 8 - diyAudio
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Old 4th June 2012, 07:37 AM   #71
lolo is offline lolo  France
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Quote:
Originally Posted by StigErik View Post
Well there isnt much Haas effect since all early reflections are inaudible with music signal. To call it an "acoustic black hole" might be appropriate I guess ....
why did you treat the other wall with diffusers then?
thought the Haas effect wasn't limited to the early reflections, but, I may be wrong..
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Old 4th June 2012, 08:49 AM   #72
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The Haas Effect is the effect of early reflections only (arriving up to 50 ms after the direct signal), and they make the direct sound become stronger and - depending of direction - make the direct sound "bigger" and more spacious, but without being heard as separate echoes or reverb.

The rear wall diffusor is there to avoid early reflections from the rear wall; no Haas effect.
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Old 4th June 2012, 08:52 AM   #73
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Originally Posted by auplater View Post
Actually, it started out as a 2 way at most (BG-75 plus 2x6.5 peerless woofers)... baffle width 21"... if I recall, the BSC starts around 270 hz or so

I added the additional speakers to improve the sound and power handling, but the original RD75 + 2 woofers sounded pretty good on its own. The high end super-tweeter addresses the beaming and dropoff of the BG's > 12 Khz quite nicely, uses a simple 1st order xover.... no high end xover for the RD75's... the bass bin is xover 2nd order LR.... and the baffle step helps the transition zone at the low end

I may rebuild them using Lucite baffles (see thru).... still debating on that...

cheers

John L.
I've seen your design before over in my own dipole thread. Nice build, but quite different from my own.

I have lifted the top end 12 dB at 20 kHz with EQ. Without EQ a super-tweeter would probably be needed.
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Old 4th June 2012, 11:13 AM   #74
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Here is my solution to a baffle for a RD-75 - magneplanar bass panels either side. They fill in the bottom end nicely, same fast speed as the RD-75 (I could never put a panel with a cone) and make a handy baffle. Crossover is first order at 660Hz, achieved by a passive filter in the input of each amp - speakers are bi-amped so I have a dedicated amp for each driver - so each driver is direct coupled to the amplifier. I have a notch filter according to the BG recommendation. I an very happy but to tell the truth I have heard a better tweeter than the RD75. SOme crazy friends of mine have designed and built 65 inch ribbon tweeter to match their maggie panels. Sounds simply magnificent. That is next on the DIY list.
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Old 4th June 2012, 11:43 AM   #75
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Nice turntable, a SOTA if I'm not mistaking?

If you have not used EQ to lift the top end of the RD-75, a super-tweeter of some kind should improve upon it I would thing. Cool idea to use planar bass panels. How far down i frequency do they go?
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Old 4th June 2012, 12:22 PM   #76
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Originally Posted by StigErik View Post
Nice turntable, a SOTA if I'm not mistaking?

If you have not used EQ to lift the top end of the RD-75, a super-tweeter of some kind should improve upon it I would thing. Cool idea to use planar bass panels. How far down i frequency do they go?
Well spotted, its a SOTA sapphire, with a Souther linear tracking arm. I've had this combo for nearly 20 years and still ahppy with it. I've recently added a Win strain gauge cartridge which is best cartridge that I've ever heard.

Back on topic - yes I know that the RD-75 needs a bit of top-end lift. As much as I love what it can do matched to the Maggie panels, I have heard a true ribbon and it is a big improvement on the RD-75. Rather than build a super tweeter I have decided to build a ribbon tweeter. Pic.s to follow tomorrow night. Oh and I know that I can't even hear 15kHz, so maybe no point to a super tweeter!

Your question about LF extension - never measured the maggie panels. They are reputed to go down to 40Hz, not super low but it is the quality of the bass that counts. I can't stand listening to box speakers after using the planar bass panels. There is absolutely no boom or overhang with maggies, so I have become hyper sensitive to those when I listen to boxes. I have 3 other friends who have replaced the Tympani tweeter with ribbons in a layout the same as mine, we have a small cult on our hands. Amaing how good 40 year old bass panels sound (though one of the boys has replaced the wire on our bass panels - a very clever boy).
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Old 4th June 2012, 12:51 PM   #77
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Yeah, please post pics and some info about the ribbon tweeter. I'm very interested, since to be honest, RD-75 is the best tweeter I've heard.... and if anything potentially better is out there ...?
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Old 4th June 2012, 04:05 PM   #78
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Given the dominance of room modes below ~ 400 hz, I've never experienced the "slow bass" problem implied about cone drivers used with planar drivers, at least when used inside a room of anything less than auditorium dimensions. As long as the "box" Q is near critical damping, "overhang" etc. is all a subjective observation...

My setup has profound deep bass, as well as appropriate "speed" when necessary. It's all in the implementation...

John L
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Old 4th June 2012, 05:08 PM   #79
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I have no problems with bass "speed" either, and I have big heavy 21" woofers running up to 200 Hz. Dipoles of course.
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Old 5th June 2012, 05:35 AM   #80
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I have no problems with bass "speed" either, and I have big heavy 21" woofers running up to 200 Hz. Dipoles of course.
Well I would love to hear this. But I did say i didn't like BOX speakers, never said that I disliked cones - what sort of enclosure are you using? An open baffle?
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