Bohlender Graebner RD75 with Acoustic Elegance Dipole15 Open baffle Project - Page 2 - diyAudio
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Old 4th October 2013, 11:46 AM   #11
adason is offline adason  United States
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...and more normal...so in the end...nothing new
Stig, I know your thread well, I followed it. Are you absolutely sure that your speakers would not benefit from one supertweeter in the middle? Just a thought, maybe be worth the try.
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Old 4th October 2013, 02:40 PM   #12
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I was told I needed the tweeter.
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Old 4th October 2013, 02:59 PM   #13
Octavia is offline Octavia  United States
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Having heard the Enigma supertweeter demo at the Dagogo Audio show I think it is safe to say that there is something to the fact that ultra high audio frequencies do somehow add clarity and dimension to what we hear in normal recordings. Once you get cued into it the effect is subtle but definitely in the direction of being more real to life. There is also some research on our "perception" of frequencies out to 100kHz or so, that is not in the spectrum of normal "hearing". I wonder if this explains some of what people like in those Raal ribbons and others that extend way way up.
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Old 4th October 2013, 07:23 PM   #14
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There has been constant debate on whether tweeters are necessary. People will spwear up and down you don't need a tweeter with a 15 inch full range which goes up to 15khz!
I think I'll add a tweeter to whatever I'll build just to save myself that moment of regret, that it is missing something. Something I could have added easily but chose not to.
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Old 6th October 2013, 09:44 AM   #15
ds23man is offline ds23man  Netherlands
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My system was showed yesterday on a diy audio day and nobody missed a tweeter!
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Old 6th October 2013, 08:33 PM   #16
adason is offline adason  United States
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is the planar open baffle? does not look like it is...
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Old 6th October 2013, 08:36 PM   #17
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Yeah? I've heard from some saying you can remove the back, others say you can't?
Maybe it depends on the model?
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Old 7th October 2013, 06:27 AM   #18
ds23man is offline ds23man  Netherlands
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The RD driver is a dipole, you can use as a dipole or as monopole. Mine are used in a monopole configuration.
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Old 7th October 2013, 07:51 AM   #19
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Quote:
Originally Posted by adason View Post
...and more normal...so in the end...nothing new
Stig, I know your thread well, I followed it. Are you absolutely sure that your speakers would not benefit from one supertweeter in the middle? Just a thought, maybe be worth the try.
There are two sides to this.

Yes, in theory the RD-75 could benefit from a supertweeter, since the dispersion starts to narrow above 5 kHz or so, and the frequency response drops like a cliff above 18 kHz.

The high-end roll-off of the RD75 is easy to fix with EQ.

The other side is how to integrate an omni supertweeter with a line-source driver. We will have two drivers with very different polar patterns, and one with 3 dB loss per doubling of distance, and the other with 6 dB. The tweeter will also have to be placed on the side of the RD-75. This combined with a high XO point will result in severe lobing in the horizontal plane.

Ideally a supertweeter should be a long very narrow ribbon to make it line-source, and to get good horizontal dispersion. And it should be placed almost inside the RD-75 to reduce the horizontal lobing.

As you see is it not easy to integrate a supertweeter with the RD-75.
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Old 15th October 2013, 05:45 PM   #20
Octavia is offline Octavia  United States
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When it comes right down to it the whole supertweeter thing is in the realm of the 1% icing on the cake. I've no doubt one could live without it, and as Stik mentions the integration of a supertweeter with a line source dipole isn't exactly easy. On the other hand for some that 1% becomes a major goal. The Enigma supertweets were special but then again they cost more than a full stereo pair of RD75 with Acoustic Elegance Subs would run combined.
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