Some FR Measurements of 4" Pioneers - Page 2 - diyAudio
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Old 20th October 2004, 01:33 PM   #11
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I suppose I could just mount them at the top but that would make the high-end a point source while the lower end is an array.
Bad idea. The reason why is contained in your statement.
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Old 20th October 2004, 01:46 PM   #12
Sherman is offline Sherman  United States
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Originally posted by BillFitzmaurice


Bad idea. The reason why is contained in your statement.

Yeah, sometimes I state the obvious but it doesn't quite register until my mind has a chance to sleep on it!

If I do that array I'll have to either run the Pioneers full-range and without tweeters or come up with a mounting scheme to run a line of tweeters down the side. Maybe sort of a "wing" attached to the side. Hmmm...
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Old 20th October 2004, 01:57 PM   #13
Sherman is offline Sherman  United States
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Originally posted by rcavictim



I would suggest also getting a sweep..., you don't actually need to test both speakers. ...have the mic two or three meters/yards in front of it and then same distance off axis... the sweep will be most meaningful if it is measured at the distance you find the line array phases into focus. ... this distance can easily be four meters.

I'll try this with one speaker. I have noticed that the larger arrays sound better when I am sitting at least 3 meters away. The sound becomes "crisper" for lack of a better word. Is this the effect of the array "phasing into focus"?

The smaller arrays don't really exhibit that effect but I think they aren't operating as true arrays since the drivers aren't mounted as close together.

When I do the tests outdoors to eliminate room effects I'll do one set at 2 meters as I did inside and another at 3 or 4 meters and compare them.
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Old 20th October 2004, 04:36 PM   #14
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maby you could do some tests on some of the mods people have been doing to these drivers?
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Old 21st October 2004, 03:16 AM   #15
Sherman is offline Sherman  United States
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Originally posted by Chris8sirhC
maby you could do some tests on some of the mods people have been doing to these drivers?

Part of my "master plan" is to do some tests before and after Damar application. I have applied Damar to a couple of speakers and believe I hear a difference. It would be nice to know if the difference is measurable!
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Old 21st October 2004, 03:25 AM   #16
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I used polyurethane varnish to treat some 5 1/4" paper drivers I bought from Mc Gee Radio quite a few years ago. The mid range was a bit nasty before treatment, and smoothed out quite a bit after the varnish. One thing I have also thought of trying is using a silicone compound like Dow Corning Sylgard 184. As mixed, it is a viscous liquid, which sets into a clear elastomer. I'm thinking it would provide damping for a paper cone.
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Old 21st October 2004, 03:43 AM   #17
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I am almost done coating all 32 of my NSB's using "Hasbro Liquid Puzzle Saver" that can be found at any Wal-Mart. Its clear, water soluble, oderless, and can be found in matte and gloss finish. I havnt ever heard anyone mention this brand of puzzle coating on the forums before, so there ya go.
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Old 21st October 2004, 04:17 AM   #18
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Originally posted by wrenchone
.....One thing I have also thought of trying is using a silicone compound like Dow Corning Sylgard 184. As mixed, it is a viscous liquid, which sets into a clear elastomer. I'm thinking it would provide damping for a paper cone.
I fear that the silicone rubber may act like rubber cement tried by another here. It reportedly sucked all the highs and thus the life out of the driver. This might be good for a woofer to reduce the level of unwanted HF or the level of unwanted harmonic distortions in the speaker of the wanted fundamentals while lowering Fs a bit, at the expense of some efficiency though.

You live in the silicon valley. Why not try coating some cones with silicon!
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Old 21st October 2004, 04:48 AM   #19
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Maybe so, maybe not. I intend to listen to my Pioneers a while before I even think of messing with the cones. It'll be some time before I get them into baffles, as I have a preamp or two and several amps that need boxing and auditioning.
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Old 21st October 2004, 05:58 AM   #20
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Originally posted by Sherman


I'll try this with one speaker. I have noticed that the larger arrays sound better when I am sitting at least 3 meters away. The sound becomes "crisper" for lack of a better word. Is this the effect of the array "phasing into focus"?

The smaller arrays don't really exhibit that effect but I think they aren't operating as true arrays since the drivers aren't mounted as close together.

When I do the tests outdoors to eliminate room effects I'll do one set at 2 meters as I did inside and another at 3 or 4 meters and compare them.
You're hearing phase cancellation in the highs, I'll bet, when you're sitting close to your array. The path length from the end drivers is longer than from the centre drivers, which means the end drivers lag the centre ones because of the speed of sound, and ergo you get a frequency dependent phase shift between them.

Say you have a 1 metre long array from which you sit 2 metres away. The centre will be 2 metres away, of course, but the end will be (assuming the array is symmetric wrt your ears) sqrt(2^2 + 0.5^2) away from you (right angle triangle, root of the squares of sides, you know the rest), or about 2.06 metres away. The difference is (2.06 - 2.00) = 0.06 metres, which is a half wavelength at about 2860 Hz, so that's where I'd expect the response to start rolling off.

The effect isn't as drastic as I've shown since:
1) the other drivers in the array tend to be closer to the centre and thus fill in the highs, and
2) off axis response on 4" drivers isn't really wide at the frequencies of interest.


Cheers,
Francois.
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