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Old 2nd September 2012, 04:22 PM   #1
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Default bohlender graebener rd50 dipole eq ?

Can the bohlender graebener rd50/rd75 top end roll off be compensated for with simple eq from a dcx2496 active crossover?

How severe is its roll off?

Anyone do an actual measurement that they can post?
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Old 2nd September 2012, 05:18 PM   #2
Octavia is offline Octavia  United States
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B&G has excellent graphs and white papers on their site. You can also look at the pdf attachments from B&G on the Parts-Express site.
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Old 2nd September 2012, 08:35 PM   #3
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I have measured approx 10 dB loss at 20 kHz on my own RD-75's, and more or less flat response to 15 kHz. Its really not necessary from a listening point of view to compensate for the roll-off, but its possible and simple to do it with EQ.
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Old 2nd September 2012, 09:51 PM   #4
Octavia is offline Octavia  United States
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Not to go off topic too much but you might find it really insightful to listen to test tones going up to 20kHz and find for yourself how much (or rather how little) is really up in that range above 15kHz.
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Old 3rd September 2012, 07:40 AM   #5
Remlab is offline Remlab  United States
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RD-50 At 50", measured by John Atkinson(With MLSSA), in BG Radia's own 520i design.
Bohlender-Graebener Radia 520i loudspeaker Measurements | Stereophile.com
It's interesting to note that the reviewer and Atkinson loved the sound of this speaker. The frequency response evens out at the actual listening position, but the highs are still subdued.(The further away you get from a line source, the less subdued the highs will be.)
http://www.stereophile.com/content/b...n-january-2005
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Last edited by Remlab; 3rd September 2012 at 08:09 AM.
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Old 3rd September 2012, 08:06 AM   #6
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Most listeners prefer a downward-sloping frequency response at the actual listening position, much like this: (the top red curve)

Click the image to open in full size.
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Old 3rd September 2012, 08:09 AM   #7
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Quote:
Originally Posted by Octavia View Post
Not to go off topic too much but you might find it really insightful to listen to test tones going up to 20kHz and find for yourself how much (or rather how little) is really up in that range above 15kHz.
Then why would we need hi-rez?

I have EQ'ed my RD-75's flat to 20k with an EQ point at 20 kHz, +10 dB, Q=2.5, but I really cant say I hear a big difference if I turn that EQ off.
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Old 3rd September 2012, 03:36 PM   #8
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Thanks for all the great responses. Is there any benefit to the 75 over the 50 other than low end extension, power handling?

How do you set up an active notch filter for the 4k or so peak with a DCX?

Would a 400hz 4th order cross be ok for the RD50 to 2 RS180's?
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Old 3rd September 2012, 04:08 PM   #9
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I was just at Bob Katz mastering studio (Digido.com) the other day helping him tune his subs and he has a slight downward tilt measured at the listening position. It sounds natural for sure. Any more boost in the treble and it starts to sound bright and edgy.

Greg
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Old 3rd September 2012, 04:12 PM   #10
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Originally Posted by SpinMonster View Post
Thanks for all the great responses. Is there any benefit to the 75 over the 50 other than low end extension, power handling?

How do you set up an active notch filter for the 4k or so peak with a DCX?

Would a 400hz 4th order cross be ok for the RD50 to 2 RS180's?
Set the freq to 4Khz and narrow down the width or Q setting until it only affects the range necessary. You will need to measure to do this properly. It is easier to make a large boost or cut first to see what area is affected and then slowly dial back until you get the result you want. This is done with a parametric section, not the graphic EQ.

Greg
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