B&G RD-75 dipole - baffle and or waveguide? - Page 11 - diyAudio
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Old 8th June 2012, 07:16 PM   #101
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I did read the John Whittaker study (was it done around 1997 ?), and the drivers they had there measured very different from my own, which are about 2 years old now. I suspect B&G has made design changes.

They sure did change the Neo3, because early examples were several dB down at 20 kHz, and the new ones are not.
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Old 8th June 2012, 07:32 PM   #102
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I would bet that your thoughts are correct. I should give them a call.
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Old 8th June 2012, 09:40 PM   #103
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The "beaming" above ~8 khz is why I added the extra drivers... and shows in my off-axis plots... the power response in the room improved as well

I read all the alsr postings from Blondia & Whittaker as well... very helpful in the design. not sure the airfoil has all that great effect on the actual response (but it's sure pretty!) as mine are easily equalized flat to +-2 dB or so from maybe 500 to 15K... but I like the current downward tilt better...

part of why I'm thinking of redoing mine in clear Lucite... time for some cosmetic changes I guess...

John L.
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Old 8th June 2012, 10:02 PM   #104
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As I remember it the airfoil shape allegedly flattens out the frequency response because the phase cancellation (front to back of the dipole) is not concentrated at one frequency. However that totally looks by the affects of the 'missing baffle' that is on the inside edge of the cabinets, so I dunno ...

In any case, you are right they do look cool! I wonder why RD-75s aren't more popular? They never seemed to catch on in the DIY community. Is it their size that discourages people?
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Old 8th June 2012, 10:06 PM   #105
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I believe the offset position from center vertical and the slant sides help eliminate some of the dipole ripple as the front/rear cancellation is spread over many frequencies. I swept back the baffle to lower the knee and slanted the baffle some (but I wanted to keep the width at ~20" or so...

Size does seem to matter ... spousal acceptance is a BIG deal for some (mine doesn't really care... hence living room more of a man cave)

plus last ten years, I think ipods, etc. have ruined most people's hearing anyway

John L.
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Old 9th June 2012, 08:08 AM   #106
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I run the RD-75 without baffle, and I don't see any pronounced dipole peaks or dips.
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Old 9th June 2012, 08:13 AM   #107
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Quote:
Originally Posted by auplater View Post
Size does seem to matter ... spousal acceptance is a BIG deal for some (mine doesn't really care... hence living room more of a man cave)
My wife almost started to cry when I explained her the size of what eventuelly did not become our new livingroom speakers.....

Luckily, I have my own dedicated batcave where no females are allowed entry.
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Old 20th September 2012, 08:01 AM   #108
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Default How much power

I was just wondering what is the minimum power you guys would recommend for the rd75 planars.
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Old 20th September 2012, 11:30 AM   #109
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Around 50 watts should be plenty for most people. I rarely exceed 10W peak.
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Old 20th September 2012, 12:09 PM   #110
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Default A few more questions.

I have a few more questions if you don't mind answering me. By the way thanks for the reply Stig. I've been looking at the RD75 for a few years now but have been resistant to order because I like tube amps. I have a 15 watt transcendent sound otl amplifier that I really enjoy and was hoping maybe it would be enough to run the RD75's. Would 15 watts per channel be enough power. My room is 14 feet wide by 16 feet long. I have a active crossover with 48db slopes that I would use at 175hz to crossover with the woofers. I don't listen ridiculously loud. Usually around 95-98db peak and average of 90db. Also what is the lowest impedance the driver gets down to. Is it pretty much a flat 6 ohms across the frequency range?. Thanks for the help :-)
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