As I got my "missing" package, I got 4 generic raw paper, foam surround 3 1/2 inch speakers. I went all out, they were $1.69 each.
The following plots are: Raw as supplied, Ductcap cut out and a phase plug added, a few dots in a pattern made of craft glue, and a wiped on, wiped off coat of jesso.
Measurements were one inch above the plane, gated 2 ms.
The following plots are: Raw as supplied, Ductcap cut out and a phase plug added, a few dots in a pattern made of craft glue, and a wiped on, wiped off coat of jesso.
Measurements were one inch above the plane, gated 2 ms.
Attachments
a tale of four speakers 
The dots look good.
Plug: Used foam plugs many a time here, cut tiny plugs with typical hole saw. Use scrap wood with hole, then move back the 1/4" drill bit. Can make 10 in about a min. Trim with scissors.
E.g. have a 1" VC, order a 15/16" hole saw:
Amazon.com: MK Morse AV15 Hole Saw, 15/16-Inch Bi-Metal Boxed: Home Improvement
The dots look good.
Plug: Used foam plugs many a time here, cut tiny plugs with typical hole saw. Use scrap wood with hole, then move back the 1/4" drill bit. Can make 10 in about a min. Trim with scissors.
E.g. have a 1" VC, order a 15/16" hole saw:
Amazon.com: MK Morse AV15 Hole Saw, 15/16-Inch Bi-Metal Boxed: Home Improvement
OK, some analysis.
Phase plug reduced the depth of the dips in the 5 to 10K range by about 4 dB. It added a big spike at 18K.
One coat shifted everything down just a bit, and smoothed things by a dB or so. It has considerably more top end, but I suspect that is breakup.
Dots were considerably smoother in the 1500 to 5K range but a few dips were deeper.
No magic formula yet. Each change was, well different. Time to combine changes. I will do a thin wipe in the dotted driver and add a backside coat to the one-coat along with a bit of a thick bead around the surround.
Phase plug reduced the depth of the dips in the 5 to 10K range by about 4 dB. It added a big spike at 18K.
One coat shifted everything down just a bit, and smoothed things by a dB or so. It has considerably more top end, but I suspect that is breakup.
Dots were considerably smoother in the 1500 to 5K range but a few dips were deeper.
No magic formula yet. Each change was, well different. Time to combine changes. I will do a thin wipe in the dotted driver and add a backside coat to the one-coat along with a bit of a thick bead around the surround.
As a top coat, water base poly may be good. It would dry fast and last forever:
Amazon.com: Exterior 450 Finish, Satin - Quart: Home Improvement
Amazon.com: Exterior 450 Finish, Satin - Quart: Home Improvement
Plugs, now why did I not think of that.
I ran impedance tests. The thin coat and the dots only shifted Fs about 3 Hz. The two sided heavy coated, which happens to also be the phase plug, shifted 24 Hz. Significant mass. I think the manufacturing tolerance is so wide I can't correlate the shift in Q.
Quick playing them just sitting on the bench. Dots sound better.
I ran impedance tests. The thin coat and the dots only shifted Fs about 3 Hz. The two sided heavy coated, which happens to also be the phase plug, shifted 24 Hz. Significant mass. I think the manufacturing tolerance is so wide I can't correlate the shift in Q.
Quick playing them just sitting on the bench. Dots sound better.
I figure my $7 was well spent. Time to move on. I was quite surprised how well the dots work over even very heavy damping. Sure wish we could see some inferometry pictures. Where are the college kids when you need them? I am really looking forward to hearing Dave's Fostex compared with stock and the hack job I did.
Conclusion:
Yes, the pattern treatment works quite well. No BS about it.
Conclusion:
Yes, the pattern treatment works quite well. No BS about it.
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