wool vs Dacron/BAF in TL - diyAudio
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Old 10th September 2006, 10:23 AM   #1
Henkjan is offline Henkjan  Netherlands
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Default wool vs Dacron/BAF in TL

I am about to complete the construction of a pair of Needles and wanted to try long hair wool as stuffing.

the question that came up was how much wool compared to the BAF (I assume Dacron is a brand name for BAF type stuffing). my guess would be some 10% more in weight than BAF? (I base this guess on MLK's articles in which he states: "Based on this second set of plots, it appeared that the wool might provide a little less viscous damping for the same packing density.")
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Old 11th September 2006, 11:16 AM   #2
Henkjan is offline Henkjan  Netherlands
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being impatient as I am, I conclude from 48 views and no replies that my assumption is correct

so unless someone within the next 6 hours can convince me otherwise, I will stuff the Needles with 80 grams of sheep and close them...
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Old 11th September 2006, 12:13 PM   #3
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There really isn't a great deal of difference between different damping materials. None exhibit any genuine sonic superiority over the others, so whatever is cheapest should do the job, and help preserve the contents of your wallet into the bargin. A 10% alteration in damping, when we're looking at relatively light quantities (less than 0.5lbs ft^3) is unlikely to be in the least audible. MathCad appears to err on the pessimistic side WRT necessary damping quantities BTW so you don't always need quite as much as the figures show to achieve the desired response.
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Old 11th September 2006, 03:40 PM   #4
Henkjan is offline Henkjan  Netherlands
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thanks.

I'll run a couple of simulations to assess the sensitivity of the design WRT amount of stuffing and move on from there.
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Old 11th September 2006, 07:31 PM   #5
Henkjan is offline Henkjan  Netherlands
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with most of the stuffing in the closed end of the line, the response of the needle is rather unsensitive to changes in the stuffing density. I tried half the amount and 20% more and the differences were subtle.

so on with the show! lets put some sheep in them and test how they sound (better dig up that "animals" CD for a proper soundtrack )
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Old 11th September 2006, 07:49 PM   #6
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Right. You want to preserve the fundamental resonance in an MLTL, and damp the harmonics. The point of maximum LF velocity occurs at the terminus of the line, and with increasing frequency it moves further up. Stuffing being most effective where air velocity is highest is best in the upper 2/3 or half of the line, leaving the rest empty, or near so.
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Old 12th September 2006, 05:15 AM   #7
gpapag is offline gpapag  Greece
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Ref. Scottmoose (post#3)
Quote:
There really isn't a great deal of difference between different damping materials. None exhibit any genuine sonic superiority over the others, so whatever is cheapest should do the job
Last winter, I was experimenting with stuffing on a quarter wave enclosure for the full range Jordan JX92S.
The three stuffing alternatives were: Fiberglass roll, Dacron roll, pillow staffing bulk.
To my surprise, Pillow stuffing bulk just killed the life out of the mids. Dry and lean.
With Dacron roll, the subject was able to move arms and legs.
With fiberglass roll, mids were restored.
Varying stuffing density, didn't change the relative picture .
I don't have any graphs, sorry.
I don't mean to generalize. I am referring to this particular enclosure/speaker combination. I trust Scottmoose has a broader experience than my limited one.
The problem is that I am left with 1cubic meter of pillow stuffing material. I won't use it even for stuffing my pillows ( a lot of mid frequencies in my full range dreams).
Regards
George
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