B&G RD-75 dipole - baffle and or waveguide? - Page 3 - diyAudio
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Old 8th October 2011, 07:46 PM   #21
dacen is offline dacen  Norway
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Good luck with your system. Just take this into account if you are connecting the RD50 directly to the output of your amp. A passive crossover is effectively blocking any DC offset at the output of the amp. An active crossover put on the input of the amp does not. As the Hypex amps are digital (Pulse Width Modulation)amps they might-be free of any DC bumps even at turn on and off.
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Old 9th October 2011, 07:06 AM   #22
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Quote:
Originally Posted by dacen View Post
Even the smallest DC offset on the output when turning on or off the amplifier could destroy the ribbon totally, so be aware. Just curious.
No it wont. The RD-75's thermal power handling is 100W. With an impedance of 6 ohm that takes a DC offset of 24.5V. In addition, the power-on "click" of even bad amplifiers is usuallly very short.
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Old 9th October 2011, 11:50 AM   #23
dacen is offline dacen  Norway
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All I can say is, be aware! I have tried this. Here are some statements:

"All amps put out DC, including OP amps, unless they have offset defeating circuitry at their outputs. You are not going to get away from it by sticking to conventional amps. "

This would not be true, as several amplifier manufacturers have taken the care to avoid the problem, to good effect. Digital or transistor - both types have "with" or "without" brands. For some speakers this is not a problem. But for anybody building an active system around amps that has dc they are headed for problems unless they have factored in a solution. As mentioned - for ICE I have a solution.


Vince - amps like Krell and a few others were made to not have dc from the start. You should see my Rotel 991 run-in workshop amps. When I was evaluating DEFINITIVE I was foolish enough to connect these to the MR ribbon - the result a whopping 17mm + excursion!!!! Even after turning off the ribbons held in place for a few seconds as the capacitors drained. Foul.

Digital, transistor - all could be suspect.
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Old 9th October 2011, 11:59 AM   #24
dacen is offline dacen  Norway
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See the specs for active amping. Synergy 1.5 specifications This is what I am talking about.

Last edited by dacen; 9th October 2011 at 12:01 PM.
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Old 9th October 2011, 04:46 PM   #25
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I see they write DC offset less than 1 mV. But WHY? 1 mV will not make the ribbon move all that much.

With transformer-coupled ribbons DC offset will be a problem, since the DC resistance of the transformer is usually very low. Only slight DC offset will lead to saturation of the transformer core.
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Old 9th October 2011, 07:22 PM   #26
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There is a big difference. The APOGEE is a ribbon. The BG is a planar. planar is fixed at the sides. A ribbon is corrugated and free hanging.
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Old 9th October 2011, 08:29 PM   #27
dacen is offline dacen  Norway
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Well, that makes a whole lot of difference.This information is new to me. Do you have a link to where I can find info about these particular physical properties of the BG ribbons. If this is how the BG ribbons are built they are probably ment for PA usage and not so much for Hi-Fi use.
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Old 9th October 2011, 09:33 PM   #28
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Why would they not be intended for hifi? With its fairly low sensitivity (88 dB), they are certainly not intended for PA...
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Old 9th October 2011, 10:38 PM   #29
dacen is offline dacen  Norway
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I am not saying that they can't be used in Hi FI. I am not in the position to judge. It could be they are made for PA equipment as well as Hi FI. My experience is only with free hanging ribbons for MRTW. This type of MRTW fixed at the sides will not be an option for me. Eventually this is up to the diy builder himself to decide. If good results are obtained with this driver, what could be better?
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Old 10th October 2011, 02:05 AM   #30
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Originally Posted by dacen View Post
Well, that makes a whole lot of difference.This information is new to me. Do you have a link to where I can find info about these particular physical properties of the BG ribbons. If this is how the BG ribbons are built they are probably ment for PA usage and not so much for Hi-Fi use.
This type of statement is exactly how so much misinformation travels around the web. You admit that you are new to the specifics of these drivers and yet immediately make a judgement as to their intended purpose and usability. BG planars are indeed "hifi". In fact, their Neo10 mid-range is one of the finest mids available at the time.

See Zaph for his measurements:

Zaph|Audio

you will have to scroll a ways down the page to get to it.

See my project here:

HTGuide Forum - Raal, Neo 10 open baffle

Greg
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