Diffraction Control for Polk SDA Tweeters
dbnh
Posts: 194
I have been using Jim Goulding's "diffrationbegone" wool felt surrounds on my SDA 1C tweeters for a while with excellent results. I came across the following review in Stereo Mojo of Jim's anti-diffraction surrounds (albeit the review is not Polk-centric). However, the review eruditely states what the surrounds do to speaker systems, and shows some photos including those of some measurements. Thus, this is my lazy way of getting around writing my own review of what the surrounds similarly do for my SDA 1Cs.
I add that the custom work Jim did for me (so that I could use the felts and still use my speaker grills) was excellent; I simply needed to provide Jim with the exact measurements. I would not recommend trying to cut the surrounds yourself, since the material is somewhat thick and I feel you'd need probably a machine, and certainly more than regular scissors, to match the exactitude of Jim's professional cuts. Furthermore, I note I needed two sets of surrounds for each 1C, since each speaker has one pair of tweeters.
Happy listening!
I add that the custom work Jim did for me (so that I could use the felts and still use my speaker grills) was excellent; I simply needed to provide Jim with the exact measurements. I would not recommend trying to cut the surrounds yourself, since the material is somewhat thick and I feel you'd need probably a machine, and certainly more than regular scissors, to match the exactitude of Jim's professional cuts. Furthermore, I note I needed two sets of surrounds for each 1C, since each speaker has one pair of tweeters.
Happy listening!
Post edited by dbnh on
Comments
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Looks like $5 worth of materials from a craft store. I'm not saying they don't work, but you could make something yourself easily.
Tannoy does something similar on their Dimension line. They use velvet instead of felt though."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Got a pic of the 1C's with em'?JC approves....he told me so. (F-1 nut)
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I don't know if you could make it yourself, and I have no agenda to discourage anyone so inclined. I do know the wool felts are fairly thick (3/8" - 1/2"), and I don't have the means to make them.Looks like $5 worth of materials from a craft store. I'm not saying they don't work, but you could make something yourself easily.
My point is that they do work extremely well, in my application. -
I don't have a digital camera. However, my daughter is coming in from college for a visit today, and if she's got her camera, I'll see if she can snap a couple pics. If that doesn't work, my GF is coming over to watch the SuperBowl (GO PATS!!!!) this Sunday, and I could ask her to bring her camera over. Good question / request, George. I'll see if I can get some photos up in the next week or so.george daniel wrote: »Got a pic of the 1C's with em'? -
Great,, I had the opportunity to speak with Jim about a year ago,on an unrelated subject,,but he seems to be a honest and well experienced audio guy.JC approves....he told me so. (F-1 nut)
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I don't know if you could make it yourself, and I have no agenda to discourage anyone so inclined. I do know the wool felts are fairly thick (3/8" - 1/2"), and I don't have the means to make them.
My point is that they do work extremely well, in my application.
Why not? I have felted a few pairs of speakers, the felt is usually <$2 and glue is <$2. These look much nicer but at 10x the price... -
MadMax and I played around with similar devices some years ago with questionable results. I threw mine away, not sure what Chuck did with his.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
I have access to dies of all sizes at work, both round and rectangular. It would be a snap to make these in less than a minute.
I would prefer to make my own, just so I can have black. Is this one piece with a hole for both tweeters? Pics on the SDA's would be great. -
Have finally got the hardware / software to take a couple pics, per earlier requests. Please see the attached files.
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Would that localize the sound? Raising the area around the dome, give more of a tunnel like effect, with a more narrow sweet spot?Monitor 7b's front
Monitor 4's surround
Frankinpolk Center (2 mw6503's with peerless tweeter)
M10's back surround
Hafler-200 driving patio Daytons
Tempest-X 15" DIY sub w/ Rythmik 350A plate amp
Dayton 12" DVC w/ Rythmik 350a plate amp
Harman/Kardon AVR-635
Oppo 981hd
Denon upconvert DVD player
Jennings Research (vintage and rare)
Mit RPTV WS-55513
Tosh HD-XA1
B&K AV5000
Dont BAN me Bro!!!!:eek: -
I haven't found that to be true. I have found that my speakers seem to disappear.Would that localize the sound? Raising the area around the dome, give more of a tunnel like effect, with a more narrow sweet spot? -
Thanks for the pics. How large are the holes for the tweeters?
If I do try this I will probably do it as a single piece. -
I haven't measured the hole; however, there's a tape ruler in each of the photos that should give you a pretty good idea of the dimensions.Thanks for the pics. How large are the holes for the tweeters?
If I do try this I will probably do it as a single piece. -
I don't know if you could make it yourself, and I have no agenda to discourage anyone so inclined. I do know the wool felts are fairly thick (3/8" - 1/2"), and I don't have the means to make them.
My point is that they do work extremely well, in my application.
Great post! Sounds like a winner. I don't know why the 'acoustic blanket' rarely appears anymore, if it all. AR was successful with it, so was Infinity. From big floor standing full range speakers, to little British monitors - it just seems to WORK.Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service. -
I would like to see if this will work around my Peerless on my 7's. I might use some .5" acoustic foam, I used from Parts Express.Monitor 7b's front
Monitor 4's surround
Frankinpolk Center (2 mw6503's with peerless tweeter)
M10's back surround
Hafler-200 driving patio Daytons
Tempest-X 15" DIY sub w/ Rythmik 350A plate amp
Dayton 12" DVC w/ Rythmik 350a plate amp
Harman/Kardon AVR-635
Oppo 981hd
Denon upconvert DVD player
Jennings Research (vintage and rare)
Mit RPTV WS-55513
Tosh HD-XA1
B&K AV5000
Dont BAN me Bro!!!!:eek: -
William, looks like 2.5"Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Shop Spkrs: Elac Debut 2.0 B5.2
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Jake, I don't believe that was made for around a tweeter. It appears to be made for mid and low range frequencies. You can pick up felt at your typical fabric store, or you can get fancy and use velvet like Tannoy uses.I would like to see if this will work around my Peerless on my 7's. I might use some .5" acoustic foam, I used from Parts Express."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Jake, I don't believe that was made for around a tweeter. It appears to be made for mid and low range frequencies.
Your probably right.You can pick up felt at your typical fabric store, or you can get fancy and use velvet like Tannoy uses.
Red velvet cake....mmmmmmmm
The fabrick I have seen is only about 1/8" thick, do you layer it?Monitor 7b's front
Monitor 4's surround
Frankinpolk Center (2 mw6503's with peerless tweeter)
M10's back surround
Hafler-200 driving patio Daytons
Tempest-X 15" DIY sub w/ Rythmik 350A plate amp
Dayton 12" DVC w/ Rythmik 350a plate amp
Harman/Kardon AVR-635
Oppo 981hd
Denon upconvert DVD player
Jennings Research (vintage and rare)
Mit RPTV WS-55513
Tosh HD-XA1
B&K AV5000
Dont BAN me Bro!!!!:eek: -
No, no need to for HF.The fabrick I have seen is only about 1/8" thick, do you layer it?
Taken from our own gallery."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
I want to clarify that my use of the term "felt" in my original post may be unintentionally misleading. Jim Goulding of diffractionbegone uses a thick, compressed high grade wool - the surrounds I have contain absolutely no synthetic (i.e., hard, refractive) materials.
I don't want to do a disservice to Jim or anyone else following this thread; thus, I hope this clarification helps. Happy listening!
