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Old 6th January 2010, 03:16 AM   #31
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G'day thadman,

Hopefully BudP will jump in here.

The added mass in the acrylic paint used to apply the EnABL pattern is not significant enough to drastically alter the loudspeaker parameters.

The EnABL pattern rings are scaled according to the diameter of the cone at the identified location.
There is a 'tap' test that is very effective in determining where the pattern rings need to be applied. The number of rings applied and the location will vary from driver to driver based on the 'tap' test.
Granted, this is an organic process, but it effectively identifies and addresses break-up modes in the cone.

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Old 6th January 2010, 03:34 AM   #32
gedlee is offline gedlee  United States
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Originally Posted by Alex from Oz View Post
Hopefully BudP will jump in here.
Hopefully he won't and we can keep this thread free of EnABL **. I read about it once and that was once too many. Please keep to the threads where people are actually interested.
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Old 6th January 2010, 03:57 AM   #33
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The trick is to have a gradual transition from the stiff cone to the flexible surround, because a sharp discontinuity, like that found in the large half role suspensions for high excursion, creates a very pronounced "rim resonance". A multiple role impregnated cloth surround appears to work best based on data that I have seen. The flatter multiple rolls have a much more gradual transition than a single large roll. And the impregnated cloth can be well damped.

One more thing - NOW we are talking about something in a driver that really does make a difference. All this Qts and Fs stuff is meaningless, linear BL, yada, yada, yada (shorting ring assumed, of course). It's how a driver handles the rim resonance that really makes a difference because this is always the first one. After that - in frequency - the cone just goes basically chaoitic and the radiation pattern is unusable. But a GOOD driver can get you right up to the rim resonance and still be useful.
Looking at the data I have on my HD, I have no choice but to completely agree with you if what you're saying is that ribbed surround drivers roll off smoother. Seems like that's what you are saying, but rim resonance is a new term for me. Of course the driver I have with a ribbed surround also has a ribbed cone. The drivers I have with a half roll rubber have either a doped paper or metallic cone--their out of piston band behavior is erratic, more so that the other, but all are less than my ideal. The only one that looks like it would work well enough is the ribbed paper/ribbed surround. I think I'll try doping it and measure again. Anyone have a recommended compound. This driver is otherwise useless to me so if I ruin it's performance it's no sweat, but I'd like to try something that someone has measured the effects of and doesn't require rocket science-like know how to implement.

Dan
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Old 6th January 2010, 04:32 AM   #34
gedlee is offline gedlee  United States
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Originally Posted by dantheman View Post
Looking at the data I have on my HD, I have no choice but to completely agree with you if what you're saying is that ribbed surround drivers roll off smoother. Seems like that's what you are saying, but rim resonance is a new term for me. Of course the driver I have with a ribbed surround also has a ribbed cone. The drivers I have with a half roll rubber have either a doped paper or metallic cone--their out of piston band behavior is erratic, more so that the other, but all are less than my ideal. The only one that looks like it would work well enough is the ribbed paper/ribbed surround. I think I'll try doping it and measure again. Anyone have a recommended compound. This driver is otherwise useless to me so if I ruin it's performance it's no sweat, but I'd like to try something that someone has measured the effects of and doesn't require rocket science-like know how to implement.

Dan
Try Buytl Rubber, thin it with something, but be careful as strong solvents can melt some surrounds. Problem with most materials is how they change in time and you don't know that going in so your "great fix" today could be a disaster tomorrow. "Rim resonance" is very well know and it is basically all I ever look at. Beyond that everything is so resonant that its not useable. But as I said, a good driver can get right up to the rim resonance and work well - then everything goes to sh_t.

There is no "ideal" - certainly NOT a piston driver. A waveguide can approach the ideal, but only over a limited bandwidth and they get very big if you try and go lower in frequency.

Last edited by gedlee; 6th January 2010 at 04:35 AM.
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Old 6th January 2010, 05:49 AM   #35
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Yea, I'd love to have a WG get me down to 300Hz--well 500 anyway, but then I'd have less living room to listen to it in and I'd be back to mono! So we have to compromise, but I'm trying to do so wisely on the super cheap. When I can afford a real house, I'll just buy Summas--or whatever has the bast pattern control and dynamic capability at the price I can afford when that day comes. After hearing junk WGs matched horizontally with a direct radiator, I know that's my route to happiness. Better drivers and waveguides would be nirvana.

BTW, I was hoping to find something off the shelf for dampening like the old wet look or puzzle coat. I practice KISS--because I'm just not that bright. Knowing one's limits is wise. No expensive violin varnish either! Buytl Rubber sounds interesting, but I don't trust my rather limited understanding of chemistry to pull it off. My gut tells me I'll definitely destroy the driver. NO great loss at this point, but not one I want to make. I enjoy experimenting too much and I've always envisioned this thing cranking out tunes in the garage while I with a few friends enjoy some chilled adult beverages.

Tomorrow I'm actually going to match this 15 to the 12"WG I have and see what they sound like matched up horizontally. Should be interesting. I don't know why I haven't tried this earlier. Too bad it's really pushing the limits of this cheap cd I have.

Thanks again,

Dan
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Last edited by dantheman; 6th January 2010 at 05:52 AM. Reason: inc
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Old 6th January 2010, 01:09 PM   #36
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Originally Posted by gedlee View Post
Hopefully he won't and we can keep this thread free of EnABL **. I read about it once and that was once too many. Please keep to the threads where people are actually interested.
Like I said 'highly contentious'.

EnABL is highly relevant to the thread topic, so I raised it here as something worth exploring.


Quote:
Originally Posted by gedlee View Post
Try Buytl Rubber, thin it with something, but be careful as strong solvents can melt some surrounds. Problem with most materials is how they change in time and you don't know that going in so your "great fix" today could be a disaster tomorrow. "Rim resonance" is very well know and it is basically all I ever look at. Beyond that everything is so resonant that its not useable. But as I said, a good driver can get right up to the rim resonance and work well - then everything goes to sh_t.
For mitigation of rim resonance I apply Zig 2 way glue on the back of the cone near the edge using an appropriately sized paint brush. No solvent and no problems long term.
It's blue when applied, dries clear and remains flexible and 'tacky' indefinitely - a bit like the reusable glue on post-it notes.
Quote:
Originally Posted by dantheman View Post
I was hoping to find something off the shelf for dampening like the old wet look or puzzle coat.
Puzzle coat or Modge Podge works well. It does need to be apply it sparingly otherwise it will make the driver somewhat dull and lifeless.

Cheers,

Alex
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Old 6th January 2010, 07:10 PM   #37
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Thanks Alex! Any ideas for the surround? Or maybe I shouldn't touch it, but it seems that might be the best area to treat.

Dan
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Old 6th January 2010, 09:31 PM   #38
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Here's polars on the PE 12"WG combined with a 15" woofer:
on axis:
Click the image to open in full size.
11.25 off axis:
Click the image to open in full size.
22.5 off axis:
Click the image to open in full size.
33.75 off axis:
Click the image to open in full size.
45 off axis:
Click the image to open in full size.

Still not perfect, but the cd isn't supposed to play that low and the WG is just placed on top of the baffle. It's a much better match than I've made in the past. The math seems to work fairly well. Time for music.

Dan
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Last edited by dantheman; 6th January 2010 at 09:33 PM. Reason: inc
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Old 7th January 2010, 01:41 AM   #39
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Originally Posted by dantheman View Post
Thanks Alex! Any ideas for the surround?
Yes, but I won't raise them here.
PM me the details of your surrounds - type, material etc.

These are my cone treatment goals in order of importance:
1. Maximise cone to air energy transfer
2. Minimise the reflected energy within the cone
3. Maximise surround to air energy transfer

Cheers,

Alex
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Old 7th January 2010, 01:50 AM   #40
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Originally Posted by gedlee View Post
It is the surround itself that is the problem. It needs to be soft for a low resonance but the cone needs to be stiff for good piston range. The two things are at odds with each other and only various compomises exist. There is no ideal.
I think there might be. A surroundless driver, using 2 spiders; one above the top plate and one several inches below the back plate.
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