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Old 12th January 2006, 01:56 AM   #1
bzdang is offline bzdang  Canada
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Default Stuffing and Lining Enclosures

I'm starting another thread to relieve another --

New version of Martin King's MathCad Worksheets is coming soon!

which was branching off a bit into the interesting subtopic of stuffing and lining of enclosures, TLs in this case.

My contribution will be to inform of two materials which may be of use.

The first is fiberglass ceiling tiles, a cheap source of compressed fiberglass panels for use as enclosure linings. They are typically around 0.5 inch thick and covered on one side with white textured vinyl. Readily cut with a utility knife. Most often seen in suspended ceilings of offices and commercial buildings and available at Home Depot.

The second is 3m's 5200 adhesive sealant, which is very strong and remains flexible when cured. Likely suitable for constrained layer construction methods. Available from marine supply stores as it is typically used on boats. It's a bit expensive and it has a reputation for being stronger than you wanted it to be.
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Old 12th January 2006, 02:58 PM   #2
westend is offline westend  United States
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Thanks bzdang for starting this thread as I assume others are interested, have information to share, or need help in this area of enclosure construction. Here is another sealant that purports to be a resonance killer: http://audioalloy.com/b10-00_products.html
Does anyone know of a list or graphs of materials and their properties? That is wool fiber, fiberglass, Acoustistuff, etc.?
I guess evryone knows that adding mass to a TL, horn, or other enclosure has an effect on FR. Here is an article on that: http://www.t-linespeakers.org/design/classic.html. .
I have used Dacron and fiberglass for lining but now, steer clear of fiberglass as I believe the small glass particles that are pushed into my environment can't be all that good.
I read a thread on a German forum extolling the use of wool over the manmade materials but seem to have lost the URL. Any input on the virtues of either?
One pertinent question for my next project: Is there benefit to laminating an enclosure with another material, i.e. enclosure built of 3/4" MDF and the exterior laminated with 1/2" baltic birch? I have the materials on hand but don't need to be wasteful.
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Old 12th January 2006, 03:35 PM   #3
bzdang is offline bzdang  Canada
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Welcome, and thanks for your link to the green stuff

I want to share an observation on the topic of fiber movement. While not a car audio enthusiast, I've sat in several cars over the years, generally belonging to neighbour's kids, in which the subs were going low and loud enough to make all of my hair and some parts of my clothing move on certain notes. Interesting sensation, might impress girlfriends. Don't know if it matters to TL design and stuffing strategies, someone may have insight?
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Old 12th January 2006, 05:14 PM   #4
westend is offline westend  United States
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About the car audio subs: what you're experiencing there is subwoofers with large power handling capabilities (think 500+w.) and large excursion with a ported box = large amount of air moved. I have a mobile audio system built for SQ and haven't seen many guys that have any stuffing in the sub box. They are concerned with SPL, mainly. No need to dampen any frequencies. I have two 10" subwoofers in a sealed box with about a lb. of Dacron to simulate a larger enclosure. It does the job.
I would be interested if others have a viewpoint on what material, placement, and how much to use in a BLH designed for the Fostex 126e. Is this prettymuch box dependent or is there any rule-of-thumb regarding this type of design.
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Old 12th January 2006, 08:34 PM   #5
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Another damping material that I have been hearing about is cotton insulation made from recycled cotton items. Looks like thick soft felt made from shredded blue jeans. Rumor has it that the recording studios are using large quanities for sound controll. It's suposed to have the highest sound absorbing capabilities of all the insualtion materials.

Here in Portland OR. it is available at a building supply store called "Enviromental building center"

I purchased a package last Friday but have not had time to play with it yet. Down side is as it is sold as a construction material the single package quanities are large. The smallest package is R13 3.5" thick bats for 16" on center framing. You get ten 96" by 15" by 3.5" batts for just under $75.00

Gary
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Old 12th January 2006, 08:41 PM   #6
Bob2 is offline Bob2  Canada
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This is a quote from Lynn Olsen's site for the Ariel speaker.

To minimize acoustic standing-waves inside the cabinet, use 1/2" or 3/8" thickness of F13-density 85% wool felt to line the areas around the drivers (as shown on the construction diagrams). This is an industrial felt, light grey in color, and is used for noise damping in truck headliners and under heavy machinery in factories. It can be found at gasket-supply houses in the industrial part of a major city. The panel directly behind the driver is most critical, since it will reflect energy right back at the driver if not lined with a heavily absorbent material, such as industrial felt or Deflex damping pads.
My experience with foam damping pads (2" thick #2 gray polyethylene foam) has not been very successful. Using the foam at various locations within the enclosure all resulted in a substantial loss of impact and realism and the addition of a toneless "gray" coloration to the overall sound (by contrast, the measurements showed a tiny improvement). My partner, Karna, immediately objected. (Her exact words were "They sound constipated! Take it out!") She made me remove all the foam blocks from the speakers, and sure enough, they sounded much better and more alive. So watch out when you use foam damping material.

Bob
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Old 12th January 2006, 10:15 PM   #7
Volenti is offline Volenti  Australia
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Quote:
Originally posted by bzdang
Welcome, and thanks for your link to the green stuff

I want to share an observation on the topic of fiber movement. While not a car audio enthusiast, I've sat in several cars over the years, generally belonging to neighbour's kids, in which the subs were going low and loud enough to make all of my hair and some parts of my clothing move on certain notes. Interesting sensation, might impress girlfriends. Don't know if it matters to TL design and stuffing strategies, someone may have insight?
You can also get your nose to vibrate and have your vision blurr (always a crowd pleaser)

On that note, I once had a friend help me cart a large amount of roof insulation in his wagon (think big SUV) He had a reasonable system in there (subs ect) but by the time we had the car crammed full of insulation from the B pillars back the bass almost dissapered, like 20-30db reduction. Interesting phenomena.

I've built both folded and straight TL's, I've found the folded ones all needed some degree of fill, but the straight ones didn't (when x-over before the first peak) and were much louder with better impact.
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Old 4th July 2007, 02:23 PM   #8
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any opinions on F26 versus F13 felt? what makes the F13 felt desirable in speaker enclosures? Here is a comparison for the 1" thickness:

Density, lbs./sq. yd. @ 1" thick

F13 -> 8.48

F26 -> 7.2

Wool Fiber Content %

F13 -> 75

F26 -> 45

Durometer Hardness (Shore A) 5

F13 -> 20

F26 -> 10

Tensile Strength, psi

F13 -> 75

F26 -> Not rated

Firmness (10% Deflection), psi

F13 -> 3

F13 -> 1
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Old 4th July 2007, 02:40 PM   #9
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Gary,

please,what is the commercial name of this recycled cotton ?


Is it maybe "Acousticotton" ?

Thanks
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