Hi Martin-Jan
I would like to answer that with a 'careful yes'. 'Yes', because the difference between the two coatings from the test can be heard, and 'careful' because IMO I have not researched other differences between the coatings that might explain a different sound.
Having said that, I would expect the lower distortion to be a welcome improvement and from an engineering perspective an easy decision to make.
I had a pair of ES300RS some time ago, but it was in poor condition. After they had been standing in a corner for three years I gave them away to someone who wanted to have ago at it.
MJ Dijkstra said:
I would like to answer that with a 'careful yes'. 'Yes', because the difference between the two coatings from the test can be heard, and 'careful' because IMO I have not researched other differences between the coatings that might explain a different sound.
Having said that, I would expect the lower distortion to be a welcome improvement and from an engineering perspective an easy decision to make.
I had a pair of ES300RS some time ago, but it was in poor condition. After they had been standing in a corner for three years I gave them away to someone who wanted to have ago at it.
Hi Arend-Jan,
I agree that the difference in coating should be the only difference in case of a true comparison. The best test would be two identical ESLs with different coatings to directly compare. I never took the effort to do that kind of excercise.
Anyway you inspired me to do some testing myself in the future.
ps, you gave a way a 300RS ?! Call me if you want to do that again!
I agree that the difference in coating should be the only difference in case of a true comparison. The best test would be two identical ESLs with different coatings to directly compare. I never took the effort to do that kind of excercise.
Anyway you inspired me to do some testing myself in the future.
ps, you gave a way a 300RS ?! Call me if you want to do that again!
JonasKarud said:
I just received tracking information on the 1720 polish. Should arrive on Thursday. I have a stash of leak proof 3oz bottles...about 90mL I believe that should work good for mailing. Do you think this would be a useful sample size?
Anybody interesting in experimenting with it and reporting back to the list with your results, send me a message and I'll get some shipped to you. I'd appreciate reimbursment for shipping cost...Paypal would work.
Hi Bolserst,
Thanks very much for such a generous offer. I think your proposed sample bottle size makes sense and would work well. I'm doing a bit too much experimenting already, so I'm hesitant to add another variable to the mix. Nonetheless, if I can get my ESL and OB woofer system far enough along to contribute I might be able to participate in an informal test. I seem to be moving at a glacial pace, though, so I hesitate to make any promises.
Few
Thanks very much for such a generous offer. I think your proposed sample bottle size makes sense and would work well. I'm doing a bit too much experimenting already, so I'm hesitant to add another variable to the mix. Nonetheless, if I can get my ESL and OB woofer system far enough along to contribute I might be able to participate in an informal test. I seem to be moving at a glacial pace, though, so I hesitate to make any promises.
Few
AuroraB said:
For an easy way to get an idea of the average surface resistance (ohms/square) I coat 8" x 8" section of a test diaphragm with two opposite edges terminated with 8" lengths of copper foil tape.
Then get a voltage supply (100 volts or whatever is convenient) and a digital voltmeter with a 10Mohm input impedance.
I hook the (+) of the supply to one of the copper tape edges, the other copper tape edge to the (+) input on the dVoltmeter, and the (-) of the dVoltmeter to the (-) of the supply.
So basically you have the coating connected up as the input resistance to a voltage divider.
Then you just need to convert the reading on the voltmeter to what the unkown surface resistance must be.
Vmeter = Vsupply * (10Mohm) / (10Mohm + unkown resistance)
For Vsupply = 100 volts
Resistance ===> Resulting Meter reading
1.0E+06 =====> 90.909
1.0E+07 =====> 50.000
1.0E+08 =====> 9.091
1.0E+09 =====> 0.990
1.0E+10 =====> 0.100
1.0E+11 =====> 0.010
NOTE: this gives you a good first estimate at what the resistance of the coating is. But it does not tell you if the resistance is uniform over the whole coating. For example, when testing the Licron Spray coating I got a reading of 1.0E+08 for the large 8" x 8" square, but using a smaller probe, I saw variations from 1.0E+07 to 1.0E+09 in different areas of the diaphragm. Not a good think if you are trying for low distortion and want to avoid charge migration during large diaphragm excursions.
Techspray 1720 Polish (preliminary results)
As Jonas recommended, a few tests with the unmodified 1720 polish are being done.
With no dilution, surface resistance is ~ 4E5 ohms/sq.
With 8/1 dilution, surface resistance is ~1E8 ohms/sq.
I have another test panel curing now with 10/1 dilution.
What I am after is a very uniform 1E9 coating.
The solution is quite easy to apply. It has kind of a soapy feel to it and wets the mylar nicely and uniformly. You do need to go slowly when spreading or bubbles develop that dry in to areas of locally lower resistance. I tried spreading with a cloth, cotton balls, foam roller, standard brush, and foam brush. So far, the foam brush seems to be the easiest to use, avoid bubbles, and produce a uniform coating.
As Jonas recommended, a few tests with the unmodified 1720 polish are being done.
With no dilution, surface resistance is ~ 4E5 ohms/sq.
With 8/1 dilution, surface resistance is ~1E8 ohms/sq.
I have another test panel curing now with 10/1 dilution.
What I am after is a very uniform 1E9 coating.
The solution is quite easy to apply. It has kind of a soapy feel to it and wets the mylar nicely and uniformly. You do need to go slowly when spreading or bubbles develop that dry in to areas of locally lower resistance. I tried spreading with a cloth, cotton balls, foam roller, standard brush, and foam brush. So far, the foam brush seems to be the easiest to use, avoid bubbles, and produce a uniform coating.
Attachments
a good diaphragm coating is to use liquid graphite 33, spray it in a cup add 50% thinner and use a airbrush to spray it on in several layers. mostly 4 to 6 layers will be enough to get slight conductivity. Then use plastik 70 to coat the diaphragm with an isolating coating.
200ml graphite 33 is 12 euro
200ml plastik 70 6,29 euro
enough for loads of panels. Very controlled and uniform coating.
200ml graphite 33 is 12 euro
200ml plastik 70 6,29 euro
enough for loads of panels. Very controlled and uniform coating.
I had experimented with thinning down liquid graphite in the past without much success. It required lots of thinning to get the resistance down to about 1E6. Thinning any further and it didn't conduct at all.
The data sheet for graphite 33 shows the resistivity to be 1000-2000 ohm, or 0.001E6. This is way too conductive for low distortion ESLs...especially when large diaphragm excursions are involved.
What surface resistivity have you measured with 50% thinning?
What is the purpose of adding the plastik 70 coating on top of the graphite? You mention it as an isolating coating, but I'm not sure what you are trying to isolate. What purpose does it serve other than adding undesireable mass to the diaphragm?
I've done some experiments with Prostat DPF-401 and ordinary PVA glue,
and found that a mix of 25% glue and 75% Prostat produced a very tough
high resistance coating in the Gigaohm range.
I presume that the Vermason polish also can be used:
http://uk.farnell.com/vermason/c901/floor-polish-dissipative/dp/3026656
It would be nice if anyone on this thread could try this coating mix!
and found that a mix of 25% glue and 75% Prostat produced a very tough
high resistance coating in the Gigaohm range.
I presume that the Vermason polish also can be used:
http://uk.farnell.com/vermason/c901/floor-polish-dissipative/dp/3026656
It would be nice if anyone on this thread could try this coating mix!
Jonas,
Is this a different Prostat coating that is still available?
Or is it the same DFP-410 coating(with some letters transposed
) you mentioned before that is discontinued.
PVA glue...
Since PVA glues are not water proof, had you noticed any change in resistance with humidity?
Since PVA glues are not water proof, had you noticed any change in resistance with humidity?