Paper would be a more linear material than most rubbers correct? Seems any rubber may be the worst surround material with that criteria. So a coated paper surround with a coated paper cone might be a better option for a smooth break-up? Would a combination like that dissipate the most energy?
Thanks again!
Dan
Thanks again!
Dan
If your getting to the point of break up you are driving your speakers to hard and to destruction !
Huh? I'm talking about the behavior of a driver when operating above it's pistonic range.
Dan
I'm not sure how linear paper would be, especially if it was doped. I believe it can be classified as a composite, and as such, it will possess multiple interfaces which may contribute non-linear effects.
Foam is an interesting material. However, there were early issues with wear over the course of their lifetime.
Steve Mowry wrote two articles for Voice Coil magazine with regards to materials.
http://www.audioxpress.com/magsdirx/voxcoil/addenda/media/mowry1208.pdf
http://www.audioxpress.com/magsdirx/voxcoil/addenda/media/mowry109.pdf
With a cone of the sort I described the surround as such has a variable width because above the piston range the outer parts decouple and become the surround.
There is a discontinuity between the actual surround and the decoupled part of the cone but materials such as damped bextrene and polypropylene, (and correctly formulated and damped cellulose composites, usually called papers), represent the minimum acoustic impedance anomaly to such materials as butyl and neoprene rubbers used in long excursion roll type surrounds.
The major discontinuity is then the surround to frame join.
The surround to cone interface is much more of an issue with materials such as Aluminium.
rcw.
There is a discontinuity between the actual surround and the decoupled part of the cone but materials such as damped bextrene and polypropylene, (and correctly formulated and damped cellulose composites, usually called papers), represent the minimum acoustic impedance anomaly to such materials as butyl and neoprene rubbers used in long excursion roll type surrounds.
The major discontinuity is then the surround to frame join.
The surround to cone interface is much more of an issue with materials such as Aluminium.
rcw.
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.
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This is highly contentious way of addressing cone break-up issues but worth exploring.
http://www.diyaudio.com/forums/multi-way/119676-enabl-listening-impressions-techniques.html
Cheers,
Alex
http://www.diyaudio.com/forums/multi-way/119676-enabl-listening-impressions-techniques.html
Cheers,
Alex
A minor mass redistribution has been observed to have a significant effect on the natural frequencies of turbine blades. I would assume enabl hopes to achieve something similar. However, the mass distribution applied to turbine blades was optimized through SIGNIFICANT numerical optimization with the aid of MASSIVE funding by the government. As far as I understand, a generic pattern is applied for enabl. How can one expect to achieve an optimum response if few (if any) of the parameters of the loudspeaker are considered when applying an enabl pattern?
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.
If anyone wants to grant me a massive sum of government dollars I'll quite my job immediately and get on it!
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.
If anyone wants to grant me a massive sum of government dollars I'll quite my job immediately and get on it!
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.
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.
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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
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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Like I said 'highly contentious'.
EnABL is highly relevant to the thread topic, so I raised it here as something worth exploring.
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.
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
Here's polars on the PE 12"WG combined with a 15" woofer:
on axis:
11.25 off axis:
22.5 off axis:
33.75 off axis:
45 off axis:
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
on axis:
An externally hosted image should be here but it was not working when we last tested it.
11.25 off axis:
An externally hosted image should be here but it was not working when we last tested it.
22.5 off axis:
An externally hosted image should be here but it was not working when we last tested it.
33.75 off axis:
An externally hosted image should be here but it was not working when we last tested it.
45 off axis:
An externally hosted image should be here but it was not working when we last tested it.
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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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
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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