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.
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.
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.
"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.
See the specs for active amping. Synergy 1.5 specifications This is what I am talking about.
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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.
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.
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.
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.
Why would they not be intended for hifi? With its fairly low sensitivity (88 dB), they are certainly not intended for PA...
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?
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
Why not? Even if it measures good and sounds incredible?
Honestly - the big RD-75 is the very best loudspeaker driver I have ever heard. My references also include Apogee and Magnepan planars, as well as various electrostatics and regular dynamic speakers. In my opinion, all dynamic loudspeaker drivers fail to match the RD-75, especially in the low-midrange.
Problem is I have been misinformed myself regarding RD75 and RD50, the taller ribbons. I was on the brink of purchasing a pair of RD75 based on this misinformation. I was told that it was exactly the same principle as the Apogees. That is true, but apparently not the whole truth. This information was probably given to promote sales. As they say in the computer world: Rubbish information in equals rubbish out. I hope this info from ABJensen has enlightened more people in here than just me.
Well, it should be pretty clear that all BG drivers are planars.... everywhere you find info on them they are called "Bohlender Graebener RD75 Planar Transducer". So they are different from the tweeter ribbon of Apogee, which is not fixed on the sides. The bass section of Apogee's is fixed on the sides by the way.
I did have a pair of Apogee Caliper in my room many years ago. It was fun watching the tweeter ribbon move several cm by the air pressure from the woofer panel. 🙂
I did have a pair of Apogee Caliper in my room many years ago. It was fun watching the tweeter ribbon move several cm by the air pressure from the woofer panel. 🙂
StigErik
The idea of a waveguide i front of the RD 75 could be a good idea. The RD75 is pretty directive at high frequencies because of the with of the diaphragm and has wider dispersion as the frequency decreases.
At a point it narrows again because of the dipole cancellation.
Perhaps one could construct a waveguide that compensates for this.
A Le Cleac'h is more like a exponentail horn than just a waveguide.
What kind of software x-over did you use?
Dace:
It makes no sense to disqualify a driver just by its working princip!
I have heard extremely good drivers that were horns, palnars, electrostatics, conventional cones and bending waves.
What matters is how they sound.
Apart from that it would be very difficult to make a true ribbon work down to 150 Hz because of the dipole cancellation round the ribbon itself.
The idea of a waveguide i front of the RD 75 could be a good idea. The RD75 is pretty directive at high frequencies because of the with of the diaphragm and has wider dispersion as the frequency decreases.
At a point it narrows again because of the dipole cancellation.
Perhaps one could construct a waveguide that compensates for this.
A Le Cleac'h is more like a exponentail horn than just a waveguide.
What kind of software x-over did you use?
Dace:
It makes no sense to disqualify a driver just by its working princip!
I have heard extremely good drivers that were horns, palnars, electrostatics, conventional cones and bending waves.
What matters is how they sound.
Apart from that it would be very difficult to make a true ribbon work down to 150 Hz because of the dipole cancellation round the ribbon itself.
StigErik
Where the @¤/(()--:# did you get your RD75 from?
Can't seem to find them in Europe besides BG-Speaker.de who says it will be extremely expensive to have the sent here and the retail without freight is $995,-!!!
PE sells them for $753,50...
Maybe double RD40 will be a solution as they are far more easy to send?
Or Neo - types?
Where the @¤/(()--:# did you get your RD75 from?
Can't seem to find them in Europe besides BG-Speaker.de who says it will be extremely expensive to have the sent here and the retail without freight is $995,-!!!
PE sells them for $753,50...
Maybe double RD40 will be a solution as they are far more easy to send?
Or Neo - types?
RD-75's vertical dispersion at high frequencies is not worse that a typical 1" dome tweeter.
I agree that making a waveguide could improve directivity, but that should rather be a dipole horn/waveguide to obtain the same directivity front and rear when its used as dipole.
I got my RD-75's from Parts Express.
I agree that making a waveguide could improve directivity, but that should rather be a dipole horn/waveguide to obtain the same directivity front and rear when its used as dipole.
I got my RD-75's from Parts Express.
What's the story on the rather low sensitivity specs. for all these B & G models?? They are listed at 88 dB, not a lot really...
The main reason is - I think - the use of ceramic magnets instead of Neodymium. An other thing is that the magnet gap is fairly wide to allow a good amount of excursion.
I have own the Orions for over a year now and although I find the sound to be superb and in a total another league compared with commercial products, regardless of price, I have time to time issues on some classical recordings, especially on mass violins and loud horns passages, not completely sold on the high mids transition. I have ordered a new pair of millenium tweeters and a soundcard to check what's going on. Hopefully I will find something and the design itself is not at fault.
This is one of the reasons I have followed your progress very closely StigErik and I definitely see some benefits in your last speaker iteration. But, I have also learned about the utmost importance of smooth polar dipole patern, hence my question the other day. What about the horizontal dispersion? Have you done any mesurements? This is not to be critical, quite the opposite, I am very interested and curious!
Regarding the efficiency, I guess we can safely add 4-6db because of dipole radiation so we should be more into the 92-94db range depending on the walls reflection/absorbtion.
This is one of the reasons I have followed your progress very closely StigErik and I definitely see some benefits in your last speaker iteration. But, I have also learned about the utmost importance of smooth polar dipole patern, hence my question the other day. What about the horizontal dispersion? Have you done any mesurements? This is not to be critical, quite the opposite, I am very interested and curious!
Regarding the efficiency, I guess we can safely add 4-6db because of dipole radiation so we should be more into the 92-94db range depending on the walls reflection/absorbtion.
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