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Multi-Way Conventional loudspeakers with crossovers

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Old 8th October 2004, 02:01 PM   #11
Sherman is offline Sherman  United States
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Quote:
Originally posted by cytokine


Please do report back when you have your results. I'm currently doing the same thing....

...
OK, I have coated the drivers in my line arrays and have had a chance to sit down and give them a critical listen. Here is what I think.

This is after a single coat of Winsor & Newton Superfine Dammar Varnish to the front of the cones. I coated one speaker and not the other so that I could do an A/B comparison.

After coating with a single coat there is a subtle but audible difference in A/B listening. It wasn't as noticeable if I played a passage of music, stopped the CD, switched to the other side and then resumed listening. I think this is to be expected as "audio memory" (is there such a thing?) seems to be short, at least in my case.

What is the difference? It is so hard to describe sound in words! I guess I would have to say something like "slightly crisper" in the midrange, little or no noticeable change in the high end and a change in the bass.

I can't quite quantify in words what I hear in the bass. I don't think it has been attenuated or boosted. It just seems more distinct than before but the change is very slight and we (me, my wife and my son) all heard it but couldn't say it was necessarily better or worse.

Overall the change in the sound with a six driver "line array" was much less noticable than it was in a very small two-way using the same 4" driver and the same tweeter with the same cross-over cap.

However I did apply a coat to both the front and back of the two-way and only a single coat to the front of the array. I will apply a second coat to the back of the drivers today and maybe I'll have something different to report in a day or two.
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Old 11th October 2004, 03:03 PM   #12
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Thanks for coming back with your impressions.

When I did my initial tests I coated one driver with one coat of varnish (slightly different product than yours but still a very thin Windsor and Newton protective varnish), and another with two. I also did one and two coats of rubber cement.

When they had dried I guessed that a single coat couln't have done anything to the sound so I didn't even bother to listen to them. I did listen to the ones with two coats of either rubber cement or varnish. Furthermore, I only compared the rubber cement to the varnish. Not a good experiment.

I will return to my treated drivers and evaluate the ones with a single coat based on what you have said.

I found two coats of varnish changed what I remembered the sound to be and that two coats of rubber cement really dampened the highs compared to the two coats of varnish.

I'm really in a quandry about what to do because I don't trust my hearing in this case and I don't have any measuring equipment.
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Old 14th October 2004, 04:02 AM   #13
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does anyone have any frequency response graphs of modified drivers? I would be interested in seeing what effect removing the dust cap has on the 7khz spike among other things.
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Old 14th October 2004, 07:08 PM   #14
Sherman is offline Sherman  United States
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Quote:
Originally posted by cytokine
Thanks for coming back with your impressions.

...

I'm really in a quandry about what to do because I don't trust my hearing in this case and I don't have any measuring equipment.

I added a second coat of varnish to the array drivers of the "right" speaker, I kept the left speaker uncoated for comparison to the original sound.

Results? The second coat seemed to have some effect on the high end and virtually none in the midrange and little if any in the bass. The effect on the high end was to damp it somewhat, which is OK with these speakers since they were a bit bright (I actually used an l-pad to drop the tweeters 3 dB or so and this change improved it a bit more. I'm guessing another 1 or 2 dB?).

I am waiting on delivery of a test CD and some other equipment so that in the future I'll be able to make some objective measurements in addition to the subjective listening.

I have another set of two ways I built which are uncoated so they may be good candidates for some objective tests in the next few weeks. Hmmm, I wonder if the wife would shoot me if I made the walk-in closet into an anechoic chamber?
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Old 14th October 2004, 07:12 PM   #15
Sherman is offline Sherman  United States
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Quote:
Originally posted by Chris8sirhC
does anyone have any frequency response graphs of modified drivers? I would be interested in seeing what effect removing the dust cap has on the 7khz spike among other things.

I might be able to put some together when the test stuff arrives but it could take me a couple of weeks to develop some repeatable test procedures.

I would also be very interested in anyone else's actual objective measurements. Listening tests have limits (though in the end it is how they sound to your ears that should matter).
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Old 14th October 2004, 07:47 PM   #16
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Quote:
Originally posted by Sherman



I added a second coat of varnish to the array drivers of the "right" speaker, I kept the left speaker uncoated for comparison to the original sound.

Results? The second coat seemed to have some effect on the high end and virtually none in the midrange and little if any in the bass. The effect on the high end was to damp it somewhat, which is OK with these speakers since they were a bit bright (I actually used an l-pad to drop the tweeters 3 dB or so and this change improved it a bit more. I'm guessing another 1 or 2 dB?).

I am waiting on delivery of a test CD and some other equipment so that in the future I'll be able to make some objective measurements in addition to the subjective listening.

I have another set of two ways I built which are uncoated so they may be good candidates for some objective tests in the next few weeks. Hmmm, I wonder if the wife would shoot me if I made the walk-in closet into an anechoic chamber?

The walk-in closet could be a very close approximation to an anechoic chamber with all the hanging clothes...

I borrowed a friends RatShack SPL meter and did some non-scientific tests last night.

I found that two coats of rubber cement cost me about 4-6 dB over the meat of the range of the NSBs. This was a non-scientific test in my garage hand-holding the meter. It's entirely possible that my left channel is not as strong as my right (although I've never noticed a balance problem). The treated cone was always on the left and the untreated was always on the right.

However, when I switched out the rubber cement treated driver for the one with two coats of varnish applied in quick succession, I noticed a loss of only about 2 dB over the usable frequency range.

In both cases the top end was somewhat attenuated, especially so in the case of the rubber cement.

My current thinking is that a single coat of varnish should be the optimum treatment.

Interesting that you decided to use an L-pad on the tweeters. I too am planning an L-pad and have ordered the parts for 3, 4.5 and 6 dB of attenuation. I'm pretty sure that the one in the middle will be right. I'm building a 16/18 array wired to 8 ohms.

I added the wings to the baffles last night and the Mrs got to see it for the first time. Her comment was simply "that should be interesting". My comment? God's holy trousers! These beasties are seven feet tall with tapered wings angled back at 45 degrees. The wings are two inches wide at the top and ten at the bottom. The center baffle is 12 inches wide (Home Depot 12 x 3/4 x 96 MDF shelving). I can't wait to get these finished so I can wire them up and hear them...
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