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Bohlender Graebener RD40 Planar Transducer
What kind of crossover does BG recommend a passive or active ?
The lowest recommended crossover for this is 150 Hz second order, it will work with active or passive networks.
Date published: 2014-05-22
Notch filter design
BG recommends a notch filter for the RD line. Others say a notch flter is mandatory. Without resorting to an electronic filter (like the Behringer), does anyone have a design for an appropriate passive notch filter?
BG has the recommended notch filters in their install guide below.http://www.parts-express.com/pdf/rdpdf.pdf
Date published: 2014-02-15
B&G RD40 Vertical Dispersion question.
I'm thinking of using the RD40's (along with woofers) for the front three speakers in my home theater. Two questions come to mind:1) How important is it (if at all) to have the center of the RD40 at ear level?If the answer to the first question is that it is important, then I will need to do something special for my center speaker. I have an acoustically transparent screen and the center RD40 would sit on a stand (vertically) behind the screen . The bottom of the screen is about 35" off the floor, so the center of the RD40 would be about 55" high. This would leave about the bottom couple of inches of the RD40 at ear level, but most of it would be above ear level. So,question 2:2) Would it work well to angle the RD40 down slightly (about 10 degrees) so that it is aimed at ear level on the couch where we sit?Any suggestions would be greatly appreciated.Best wishes,Dave
Creating a project with such an expensive driver demands good planning. It's not just the driver, it's the cabinet, crossover and amplifiers. The BG drivers gained notoriety with Arnie Nudel from Infinity and are still used in Genesis loudspeakers - which cost well over $10,000 a pair. If you are building a music and film system, you need to consider MANY things. Your viewing distance should be 1.5 to 2 times the distance from the screen width optimum. Read THX articles on this. Film sound is mixed at 1.5 in the studios. Now since you have an acoustically transparent screen - you can actually place the speakers correctly so the the left and right are not too far apart. If you are doing dipolar, the speakers should be 6 - 8 feet apart and 3 feet from side and rear walls... In a cabinet, forget about the rear clearance. In your situation, if you are sitting far enough away from the screen - say 12', I'd have all three speakers oriented identically for correct imaging and voicing. If the base of the RD40's are all at 35" - you will be fine. If you do not cross over the RD40 at 5000 hz to a tweeter, you will need an eq network to flatten the response above that. It get's a little dicey. The BG specs outline that. Also - the driver has a sweet spot operating area - 500 - 5000hz. Below you want a fast mid-woofer(s) and then to your sub, above - you should consider a quality tweeter - like the Aurum Cantus ribbons. Besides linear response - each driver is then optimized for horizontal dispersion. The RD40 begins to "beam" at higher frequencies. This is why drivers get smaller as the frequencies are higher - aperature size contributes to dispersion characteristics. (Save electrostats which are very different.) The neo3PDR's in line array are also a perfect and stunning match taking you up to 28,000 - plenty of headroom. have fun. Oh - Don't tilt down.
Date published: 2013-06-04