Looks like they got it right early on. 32 looks a bit overdamped eg loss of low end output probable.
Read the whole minage, did not like the test setups and lack of driver isolation. Can be done much better. Could not get past the no diffraction occurs below 2k, then lowering that to 1k. Garbage in = Garbage out
I figured someone would have posted about it so this is what I found. Seemed interesting to me to use in my car doors as a back wave killer. Not much survives in there with the moisture.
I think this test was to see what material behaves best to remove higher frequencies escaping the port in a BR enclosure.
Fiberglass still seems to be best wide band material. Although I have seen tests of fiberglass in combination with the exotic Twaron Angel Hair that seemed to perform well.
I might test that combination myself as I have both available. My goal is full range damping in sealed chamber of coarse.
I think this test was to see what material behaves best to remove higher frequencies escaping the port in a BR enclosure.
Fiberglass still seems to be best wide band material. Although I have seen tests of fiberglass in combination with the exotic Twaron Angel Hair that seemed to perform well.
I might test that combination myself as I have both available. My goal is full range damping in sealed chamber of coarse.
I don't have a lot and no testing abilities beyond my ears.. (Pat. Pending)
I played around with a vinyl ball inside a sealed enclosure. (BIG Bubble Wrap) Wrapped the outside of the ball with cotton batting and changed the air pressure to various levels inside the ball. It works..
I played around with a vinyl ball inside a sealed enclosure. (BIG Bubble Wrap) Wrapped the outside of the ball with cotton batting and changed the air pressure to various levels inside the ball. It works..
Back in the 80's I put a mylar bag inside a small sealed 2way and filled it with argon. It worked. Not practical, but was curious. Stopped messing with after a few months due to leakage. Never sounded the same day to day and always questioning how much argon had leaked grated at your nerves. Is it the music or the speaker? Uggg enough of this.
I can see something like sulfur hexafloride gas bubbles working. You can add that to my list of Ununobtanium. 😉
I can see something like sulfur hexafloride gas bubbles working. You can add that to my list of Ununobtanium. 😉
Well.
Thank you all for your responses and insights !
I never did state exactly what I was doing with my project, but my biggest
concern at the moment is stuffing for sealed subwoofer boxes. X-over
frequency will be around 125~~150 Hz tops. The boxes will be only about
1.25 cubic feet. This is then the frequency range that needs damping.
It would appear that what I can take away from this discussion is that the
lowest frequencies need dense fill material, thick in layer, to be dampened.
The boxes that I'm building will be three layers thick, the center layer being
a lead shot and sand fill. I expect that the empty box will weigh over 100
pounds, so I suspect that the box itself will be quite dead acoustically.
The last design problem then is how to dampen the internal backwaves.
Thank you again !
Thank you all for your responses and insights !
I never did state exactly what I was doing with my project, but my biggest
concern at the moment is stuffing for sealed subwoofer boxes. X-over
frequency will be around 125~~150 Hz tops. The boxes will be only about
1.25 cubic feet. This is then the frequency range that needs damping.
It would appear that what I can take away from this discussion is that the
lowest frequencies need dense fill material, thick in layer, to be dampened.
The boxes that I'm building will be three layers thick, the center layer being
a lead shot and sand fill. I expect that the empty box will weigh over 100
pounds, so I suspect that the box itself will be quite dead acoustically.
The last design problem then is how to dampen the internal backwaves.
Thank you again !
limited
As the frequency descends downward, the acoustic absorbent material has a lesser and lesser effect. However, if you are crossing as high as 125Hz, there will still be considerable output from that woofer (x-over slope dependent, of course) an octave or two above. It's still a great idea to completely fill the enclosure with fiberglass (no backing).
As the frequency descends downward, the acoustic absorbent material has a lesser and lesser effect. However, if you are crossing as high as 125Hz, there will still be considerable output from that woofer (x-over slope dependent, of course) an octave or two above. It's still a great idea to completely fill the enclosure with fiberglass (no backing).
If using unfaced R-13 FG, I recommend stuff at a rate of 1 lb/cu. ft. It will fill the box nicely. Not overstuffed and not understuffed.
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