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Old 25th May 2012, 08:35 AM   #41
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I dont know the Orion, and I have not heard it either. But - in my opinion there are compromizes. The XO frequency between the mid and tweeter is too high for the mid (should be no higher than 1 kHz because distortion rises dramatically above 1 kHz), and too low for the tweeter (distortion again). And with that baffle width, the polar pattern from 1k and up should look nasty... but since there are no published measurements of this we dont know for sure. I also expect that front/rear radiation is not perfectly the same for Orion.

The good thing with RD-75 is that front/rear radiation is very similar, so the dipole pattern is more or less the same front/rear. An other good thing is that it is line-source in the vertical plane, and thus there is almost no sound outside the vertical range of the line. Horizontally, it is not perfect. Without baffle (the way I use it), it behaves like a true dipole up to about 1 kHz, where you get a small dipole peak and wider dispersion. Above some 2 kHz, it behaves more like a dipole again. Above 5 kHz, the dispersion starts to narrow, and from 10 kHz there is obvious beaming.

Sorry, I have no measurements of this that I saved ....
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Old 25th May 2012, 09:28 AM   #42
lolo is offline lolo  France
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thanks for the swift reply, I agree, the compromise with the Orion is the 3 way assignement, a 4 way with the W15 would have been better but SL ruled it out from the start. Gainphile is trying such an arrangment in Oz, looks like it's a clear improvement. One could also imagine something like the Grand Beethoven in a different combo, 2xW22, 2xW15 and the millenium tweeter "a la D'appolito", with a separated tall array of H frame big woofers.

beaming at 10k is not so important I think, no dome tweeter is small enough back to back to give perfect dipole radiation at these frequencies anyway..
If you manage to keep almost true dipole radiation up to 5k, you are into something! Would love to hear your system one day...

cheers

Last edited by lolo; 25th May 2012 at 09:35 AM.
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Old 25th May 2012, 09:55 AM   #43
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I did have a 4-way baffle-less dipole with four W22, two W15 and a Mundorf AMT (which is dipole by nature), and large H-frame woofers. It was quite good, but not anywhere near the RD-75 with the same H-frame woofers.
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Old 29th May 2012, 07:26 AM   #44
oyvine is offline oyvine  Norway
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Quote:
Originally Posted by lolo View Post
thanks for the swift reply, I agree, the compromise with the Orion is the 3 way assignement, a 4 way with the W15 would have been better but SL ruled it out from the start.
Hi,
I actually built such a speaker:
Click the image to open in full size.

I have made some measurements on horisontal dispersion for two different tweeters.

27TDFC:
Click the image to open in full size.

27TBCD/GB-DXT:
Click the image to open in full size.

Top one is on-axis. Below that (Offset -5dB) is 30 degrees. At the bottom (Offset -10dB) is 60 degrees. Measurement window is 2ms. Crossover is 2.5kHz. I do prefer the DXT tweeter and that is the one I have playing at the moment. Please note that the DXT-tweeter is not even flush-mounted (GASP). Still it is quite smooth off-axis. It would be interesting to hear what Stig-Erik (or others) thinks about this DXT lense. Maybe you should create something similar around your RD-75?

regards,
yvin
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Old 29th May 2012, 08:32 AM   #45
lolo is offline lolo  France
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Hi yvin,

looks like Norway is the place to go!
did you try the millenium tweeter too before going 4ways? how do you cross the medium, have you kept SL analog crossover and added a stage?

Cheers

Laurent
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Old 29th May 2012, 09:27 AM   #46
oyvine is offline oyvine  Norway
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Originally Posted by lolo View Post
Hi yvin,

looks like Norway is the place to go!
did you try the millenium tweeter too before going 4ways? how do you cross the medium, have you kept SL analog crossover and added a stage?

Cheers

Laurent
Hi,
I have not tested the millenium tweeter. I have rear-mounted tweeters and thought the price for four milleniums was too high. Besides that I have listened to a few other implementations with the milleniums and I really like them (I have never listened to the original Orions). I am using a pc with an EMU-1820M soundcard and VST-plugins for crossover. This is going to be replaced with the miniDSP 4x10 Hd that I just received. I borrowed a minidsp from a friend last year and it surprised me that it was a lot better than my soundcard in the mid+treble. I also plan to test the Eton ER-4 Air Motion Tweeter that I have had in a drawer for some time. It will be interesting to see the off-axis response with that combo.

sorry for the OT
yvin

PS! Have you considered the Seas Magnum(T29MF001) for your Orions? It has a lot more cone-travel(180% more) and slightly larger piston-area(14% more) than the Milleniums. I guess it should be a better candidate for crossing over that low.
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Old 29th May 2012, 09:58 AM   #47
lolo is offline lolo  France
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Hi,

I will send you a PM, don't want to pollute Stig Erik thread!
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Old 29th May 2012, 12:09 PM   #48
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Originally Posted by pengesluk View Post
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...
Most manufactors are way too optimistic about the sensitivity of their speakers. Some even use the 8 ohms spec even if the speakers are 4 ohm, give an extra 3 dB. Manufactors of dipole speaker often relate their specification to the listening position, the calcutlate "backwards" to one meter. Real life sensitivity above 90 dB for 2.83 V in 8ohm are rare.

Roger
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Old 30th May 2012, 10:19 PM   #49
sumacSK is offline sumacSK  Slovakia
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Quote:
Originally Posted by oyvine View Post
Hi,
I am using a pc with an EMU-1820M soundcard and VST-plugins for crossover. This is going to be replaced with the miniDSP 4x10 Hd that I just received. I borrowed a minidsp from a friend last year and it surprised me that it was a lot better than my soundcard in the mid+treble.
is it the difference in hardware (what source of signal was used with miniDSP? have you tried EMU soundcard as source?) or is it the actual DSP implementation that is better with miniDSP?
do you use linear phase plugins? I am myself using vst plugin based crossover with linear phase filters and was wondering whether mini dsp could be an upgrade..

thanks!
martin
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Old 31st May 2012, 12:36 PM   #50
oyvine is offline oyvine  Norway
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Originally Posted by sumacSK View Post
is it the difference in hardware (what source of signal was used with miniDSP? have you tried EMU soundcard as source?) or is it the actual DSP implementation that is better with miniDSP?
do you use linear phase plugins? I am myself using vst plugin based crossover with linear phase filters and was wondering whether mini dsp could be an upgrade..

thanks!
martin
Hi,
I do not want to stray too much off topic so I sent you a PM about this.

regards,
yvin
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