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Outdated BG Radia thread over AC for Satie

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Posted on December 26, 2016 at 18:14:22
TitaniumTroy
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Location: Mishawaka, Indiana
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Thought the BG Radia fans might like this somewhat outdated thread, over at the AC Open Baffle Forum. Last post says Danny Ritchie is ready to start the production
of his new planer magnetic tweeter.

 

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RE: Outdated BG Radia thread over AC for Satie, posted on December 26, 2016 at 18:22:48
TitaniumTroy
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Location: Mishawaka, Indiana
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Another outdated BG Radia link at bottom of page.

Room 817: In this room a quartet of audio manufacturers (Triode Wire Labs, Charles Rollo Audio, Sound Insight, and Kanso Audio Furniture) teamed up to make big, fast, impressive sound. This was the global Debut of the BG Radia FS 680s hybrid planar-magnetics with 900W amps and Beringer Ultracurve Pro bass management ($20,000/pair). They used the beautiful Esoteric K-01 SACD/CD player as their digital source for the Gary Dodd 6H30 tube preamp and the Arion HS-500SE tube/class-D hybrid monoblocks (500W into 8 ohms and 1000W into 4 ohms). All cabling was by the aforementioned Triode Wire Labs. This room was one of the few to feature a CD player instead of just a music server. Therefore it was also one of the few rooms where a visitor could hand a CD to the man in charge and he would (cheerfully and graciously) play the request. These guys left no doubts —they were happy to be there and they made sure every guest felt the same way.


 

RE: Outdated BG Radia thread over AC for Satie, posted on December 27, 2016 at 01:03:31
Satie
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That was an interesting read.

Apparently Richie is looking to produce his newly prototyped tweeter. Probably a higher reaching follow up to the Neo3pdr. I asked, we shall see what he answers.



 

RE: Outdated BG Radia thread over AC for Satie, posted on December 27, 2016 at 16:45:10
josh358
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Details on his new tweeter here -- basically a modified Neo 3 with a kapton rather than kaladex diaphragm and gold-plated copper terminals:

http://www.audiocircle.com/index.php?topic=140490.140

 

RE: Outdated BG Radia thread over AC for Satie, posted on December 27, 2016 at 16:47:04
josh358
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Interesting thread. Did you notice the wings next to the Neo 10's?

 

RE: Outdated BG Radia thread over AC for Satie, posted on December 27, 2016 at 19:44:33
Satie
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I am not sure but I think Richie runs the tweeters with the back cup on his tall line sources.with the Neo10 in keeping with Nudel's design rules: monopole bass, dipole mid and bipole (or monopole) tweeters.

 

RE: Outdated BG Radia thread over AC for Satie, posted on December 28, 2016 at 07:04:25
josh358
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OK, that would explain why the thread mentions the back cups. But why? that seems to me a recipe for issues at the M-T crossover point. Is he dong this to minimize cavity resonance and diffraction in the baffle?

The IRS appears to have a cardioid rather than figure 8 characteristic in the highs (24 front-facing tweeters, 12 rear facing = cardioid pattern). I remember a discussion of the IRS in which Nudell said that they'd experimented with various radiation patterns and found that a cardioid pattern provided the best imaging. I'd still say that the IRS produced the most holographic imaging of any speaker I have ever heard -- it was as if the instruments were hanging in space and you could thread your way between them.

It seems to me that monopole bass is a compromise. Dipole woofers run into trouble in the midbass because of cancellation from the rear wall reflection, but they confer partial immunity to the effects of room modes, which I think significantly improves bass realism. There are also issues at the crossover between the monopole bass driver and the dipole midrange -- the rear waves will cancel -- as well as the fact that one falls off linearly with distance and the other as the square of it. However, Nudell seems to have worked out the continuity issues in the IRS -- I don't remember the system sounding discontinuous like the Beta (actually, the Beta wasn't so much discontinuous as it sounded like the frequency bands were coming from different places!).

 

RE: Outdated BG Radia thread over AC for Satie, posted on December 28, 2016 at 22:46:59
Satie
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I have not gone through the discussion about his designs with the Neo3 on his and the DIY forums. But in that context I did have a bit of a disagreement with Davey over using the Neo3 with the back cup (which he liked) or as dipoles (which I liked) The difference being the early onset of distortion on the tweeter without the back cup. The cavity resonance with the back cup is suppressed so much that the driver can - from a FR and THD perspective - be used two octaves lower. Thus could be mated with Neo10s or dynamic drivers at 2-3khz on single driver or down to 1khz in a tall line array - which makes for an even easier mating with the Neo10, as its dispersion falls off rapidly at just below 2khz. Which is where I came from into the discussion - as I was wanting to be rid of the air spring and its transient smear even if it meant that the tweeter would lose an effective 2 octaves of its output and get lots of hair on its apparent FR in near field measurements.

Richies' older designs - think the LS9 - are either monopole air spring or monopole bass and dipole Neo8PDR. The new ones are more thought out, less brute force and have him adopting dipoles for mids and bass (his H frame dipole subs with EQ) . I have not ferreted out what he does with the tweeters exactly as the drivers were unobtanium for a long time during his design of the current flagship speakers. Maybe something to look at in the near future. Just need to look it up.

I didn't go into the specifics of the IRS radiation pattern just noted that it was bipolar facing front and back but not dipole - didn't actually check if it was cardioid or something else - just noted that it was not wired to be a dipole.Which Nudel continues to do with his boxes today. always at least one tweeter facing back and the mids always dipoles with sealed box woofers.


Interesting experiments with rooze type and other orientations of dipoles by B&O on the way to designing the Beolab 90. see pic

 

RE: Outdated BG Radia thread over AC for Satie, posted on December 29, 2016 at 06:07:15
josh358
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This suggests an experiment -- you could reduce the rear output of a Maggie tweeter by 50% with thin strips of felt and then you'd have a cardioid tweeter -- wonder what it would do to the imaging?

Of course you wouldn't have the curved baffle of the IRS, and as we were discussing the other day diffraction seems to impair imaging. You'd either have to build a curved baffle (ouch) or go Richie's route and build a minimalistic one, maybe with a wing. But according to the thread, it has to be metal (for strength).

 

RE: Outdated BG Radia thread over AC for Satie, posted on December 29, 2016 at 12:13:07
Satie
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I don't run the tweeter as low so i can't really do that readily. I only use the ribbons as supertweeters in the top octave.

I did do something sort of similar with a fuzzy throw when I was getting too much in the way of early reflections from the rack - I draped it (them since I cut it in two) behind the speakers and it improved image specificity solidity and saturation and moved the center image forwards. It also removed too much of the reverberant field. It also covered the mids IIRC.

 

RE: Outdated BG Radia thread over AC for Satie, posted on December 29, 2016 at 13:14:57
Satie
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Actually, wouldn't the cardioid pattern require the back wave to be in phase with the front wave?

 

RE: Outdated BG Radia thread over AC for Satie, posted on December 29, 2016 at 18:17:46
josh358
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it will just reduce the level of the tweeter's back wave by half. At the sides, you'll get a partial rather than complete null. If the back wave is in phase with the front wave, the front and rear waves will add at the sides, and you'll get something like a lopsided omni. If you block the backwave entirely, you'll get another cardioid pattern -- nothing to the rear, full output to the front and sides. This is the radiation pattern of a conventional monopole speaker with a point or line source driver above the baffle step.

 

Maggie Rear Wave Attenuators, posted on December 31, 2016 at 14:42:47
DrChaos
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There was once (don't know if it is still available) a product called the Maggie Rear Wave Attenuators.

I used them on the tweet of my former 1.6, and now on the midrange of the 3.6 (tried on tweet, but it had little effect). It helps clean up upper midrange imaging and clarity a bit.

 

RE: Maggie Rear Wave Attenuators, posted on December 31, 2016 at 15:56:46
josh358
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That's right, I remember that you'd mentioned those.

 

Danny uses no back cup on any of the open baffle speakers, posted on January 10, 2017 at 16:00:56
Ric Schultz
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He uses the back cup in his sealed/ported designs.

 

RE: Danny uses no back cup on any of the open baffle speakers, posted on January 10, 2017 at 16:48:11
josh358
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Thanks -- that makes much more sense.

 

RE: Danny uses no back cup on any of the open baffle speakers, posted on January 11, 2017 at 11:13:58
Satie
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So the Neo10 based dipole design uses the Neo3 tweeters or his new tweeters in dipole? with a 2khz crossover?

 

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