A new polycone 3 way from Troels Gravesen. - diyAudio
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Old 25th September 2015, 02:38 AM   #1
system7 is offline system7  United Kingdom
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Default A new polycone 3 way from Troels Gravesen.

This is fun. Troels has designed a new time-aligned 3 way classic with polycones: AudioTechnology-3WC

The idea is plastic polycones with high Qms, 8" bass, 5" mid and 1" ring radiator:
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The ambition here is to present a statement in modest sized 3-way classics, no less. I've had the opportunity to work with both 4 and 10 Ohms version of the 23I52 bass driver from AudioTechnology, and I've been impressed every time; in particular when the voice coil is made from aluminum reinforced kapton, improving transient response (high Qm). Forget about old time sloppy polyprop bass drivers. They were dull and lifeless due to the aluminum voice coil formers and sometimes also high-loss rubber surrounds, not due to cone material.
Polycones might work well. Because of favourable lack of harsh breakup modes:
Quote:
The thing about mineral filled PP is - besides its low cost - the ear-friendly break-up nodes. With all the things that have been added since then, the mineral filled PP can deliver an astonishing level of transparency and not least a dynamic headroom that beats most. This is not trivial, because we may experience cone materials that deliver a tad more transparency, but may display problems when pressed really hard - and in many cases require steep crossovers. The 18H52 used in my ATS-4 is to my ears the best 6" driver I've ever had with regard to dynamic headroom. You have to misuse it before it starts sounding bad.
Because I'm a cheapish sort of person, I'm interested enough to look for a cheaper solution and drivers. This one is way above my price bracket. Nothing much new in the crossover or frequency response or driver layout, which is relatively standard Steen Duelund +-+ LR2 stuff.
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Old 25th September 2015, 03:57 AM   #2
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Peerless drivers are probably the cheapest best bet, but I find that here in Aus, drivers of a similar quality tend to cluster in price, i.e. it'll only cost a few $$ extra to get a driver which is better match to a given project. Although with the AUD going through the floor at the moment it's getting a bit more spendy.
I have a couple of 3 ways in my near future, one will use a similar combo of drivers, Old Peerless Nomex 5" mid, 8" SB for woofs, & SEAS tweeters.
The other will use an old 4" Foster Polycone 'wideranger', Piezo super tweeter (a good combo in their test cabs) & 6" Wavecor woofer
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Old 25th September 2015, 05:15 AM   #3
ScottG is offline ScottG  United States
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..I've not heard a "poly" implementation like AT's.

AT is far more like a poly-doped aluminum driver.

Tap on a regular "mineral filled" poly driver and it's "dull" sounding.

Tap on an AT "poly" and the sound is sort of a "plumy ring" to it. Quite different.
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Old 25th September 2015, 05:22 AM   #4
ScottG is offline ScottG  United States
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..as far as poly drivers.

Scan-Speak (old Vifa) 8" Poly

https://www.madisoundspeakerstore.co...fer-poly-cone/

SB Acoustics 5.25" Poly

https://www.madisoundspeakerstore.co...y-cone-woofer/



..wouldn't sound the same, but would probably sound pretty good, and measure better.
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Old 25th September 2015, 05:23 AM   #5
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And what "tap" means, if it has any meaning ?
Is it an " empirical step response with inverse relation " ?
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Old 25th September 2015, 05:29 AM   #6
ScottG is offline ScottG  United States
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..taping on the surface of the driver's cone, and listening to the resulting sound (and also the tactile feel).

All membranes exhibit a certain coloration that contributes to their result.
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Old 25th September 2015, 05:39 AM   #7
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Yes, but the membrane is just a part of the complex.
You should fell also glue tightness or compliance, as well as inside and external suspensions, the basket, the former, the air in the gap etc.
Just to say, it's not that way: the membrane works by moving in both directions freely but constrained by the double springs and actioned by the moving coil which impress the motus in the exact center, not an abrupt tap on the surface !
And...how the tapping is done ? Are the nails aligned with the finger ?
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Old 25th September 2015, 06:31 AM   #8
ScottG is offline ScottG  United States
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Quote:
Originally Posted by picowallspeaker View Post
Yes, but the membrane is just a part of the complex.
Yes, and it all happens to be physically interconnected when taping on the diaphragm.

Honestly, all this does is give some insight into the character of the cone driver, not unlike measurements. It's also an empirical process that requires several references and a decent memory of those references. Which are very easily obtained on a casual basis (..though requiring no current to the driver).

Maybe system7 has built-up some of these "references", and has a decent memory of them? He was after-all the person I was posting a reply to.

I'm betting that's the case from his prior posts and his use of certain driver's commercially. In fact I think he'll have a very good idea of what I'm describing.
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Last edited by ScottG; 25th September 2015 at 06:35 AM.
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Old 25th September 2015, 06:48 AM   #9
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So you say that a sudden force applied on a membrane to taste its ability to dampen and distribute the force along the material would tell...the ability to reproduce well a signal in a system formed by EMF generator and some components ( passive crossover ) in an environment ?
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Old 25th September 2015, 09:23 AM   #10
Scott L is offline Scott L  United States
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Default AudioTechnology 3-Way Classic

Hey, that's a sharp looking monitor !!

Man, oh man, look at that nice big port at the bottom.

I love it !

(mostly because it's likely to get someone's nickers all bunched up)
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