Best damping stuff for fullrange

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naca5

naca5

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Joined 2013
#1
Hi,

I own two pairs of fullrange driver:
Alpair 10.3 in Pencil
Betsy K in Baronet

I'm wondering which damping stuff will be better and if there better one for BLH and Pencil desgn.

Thanks in advance Guys ..

Naca
 
#9
Naca,

For the Pensil 10.3 loose Dacron hollow-fibre polyfill is recommended. The poly-fill needs to be teased out and distributed throughout the cabinet.

If you want to, you can also put a thin layer of felt on the inside side walls close to the driver and inside the top the cabinet. But this is in addition to the poly-fill.

The amount of poyfill you need will depend on you room, amp etc. Start with less and add more as required.
 
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#10
poly-fill needs to be teased out
Click to expand...

Graphic example of not-teased/teased (40g)

40g-acousta-stuff.jpg


dave
 
#12
Aquarium woolfilter. Cheap and efficient. The advantage is its low density. Used successfully in bibs and bass reflex. The second advantage is that it tears easily but it is still strong enough for a loudspeaker. It's very easy to adjust stuff quantity with it.
 
#13
Depends on what is meant by 'too much.' I spec. Dacron as a catch-all generic for hollow-fill polyester fibre which is generally the easiest type of material for people to obtain throughout the world. The quantities are a nominal only. The point of the pensil alignment (or at least one of them) is that it is relatively easy to adjust to requirements based on room acoustics, amplifier output impedance and personal taste. Hence the removable back. Not all Dacron is created equal -there are many different types, just as there are many types of damping materials, and they all possess somewhat different properties, so this is something for you to experiment with. Using the nominal quantities, you will have a quasi-TL impedance; it's more or less a flat-line unreactive load. But leaving aside variations in material, most people don't like having that much damping in the cabinet. Keep it a little way from the driver or you may mass-load the cone / suspension, preventing them from oscillating / resonating as designed.
 
#14
Scottmoose said:
Depends on what is meant by 'too much.' I spec. Dacron as a catch-all generic for hollow-fill polyester fibre which is generally the easiest type of material for people to obtain throughout the world. The quantities are a nominal only. The point of the pensil alignment (or at least one of them) is that it is relatively easy to adjust to requirements based on room acoustics, amplifier output impedance and personal taste. Hence the removable back. Not all Dacron is created equal -there are many different types, just as there are many types of damping materials, and they all possess somewhat different properties, so this is something for you to experiment with. Using the nominal quantities, you will have a quasi-TL impedance; it's more or less a flat-line unreactive load. But leaving aside variations in material, most people don't like having that much damping in the cabinet. Keep it a little way from the driver or you may mass-load the cone / suspension, preventing them from oscillating / resonating as designed.
Click to expand...


Thanks for that, hopefully my backs are removable.
Will experiment polyester fiber.
 
#18
Alpair 10.3 in Pencil
Betsy K in Baronet

I'm wondering which damping stuff will be better and if there better one for BLH and Pencil desgn.
Click to expand...

Well, strongly depends on type of enclosure, i.e. closed, BR, BLH, TML, which frequencies to damp or if you intend to enhance the virtual volume of an enclosure etc.

Measurement of relative damping at different wavelength can be found here (check the thread for measurement setup and details).

Damping material consisting of non-rigid fibers will transform movement of gas-molecules into heat and tend to act on all wavelength, more rigid dampening material (like Basotect, porous foam) will preferably act on higher frequencies (shorter wavelength).

Thus, for closed enclosures, choice of damping material is not that critical and I'd use e.g. something like polyester fibers, Dacron, and so on.

For BR-enclosures I'd go with Basotect (actually a mixture of Basotect and Fibsorb turned out to best from my experience / measurements), as you selectively want to dampen standing waves in the enclosure, but not bass frequencies (see figure given in the link above).

Please note, that the amount and packing density of fibre material can have a huge impact on damping characteristics: As soon as packing density of fibre material increases (i.e. less degree of freedom to move for the fibers) the more selectively damping can be achieved. Again see linked figure, compare 'Twaron locker' = Twaron lightly stuffed and 'Twaron extra' = compressed Twaron. Same happened with Fibsorb or Polyester fibers. See as well post by planet10 on teased/non-teased poly-fill.

Now, damping of a TML or BLH (back-loaded horn I suppose?) is special and tricky. You want to dampen the standing wave, which is relatively close to the bass frequencies you want to amplify without dampening bass response. That's why dampening instruction of TMLs and BLHs are usually very specific with respect to type, amount and placement of damping material...

In general, placement of damping material plays a crucial role as well, if you do not stuff the entire enclosure (e.g. midrange enclosure), as damping i most effective at the place where you have fastest movement of gas molecules (i.e. away from the wall, just between the two walls producing the standing wave).

Hope that helps.
 
#20
Where tone is critical I go for 50/50 wool / dacron,pollyfill pillows @ $16 au average each @ Dymocks our Aussie haberdashery . I'm sure you would have a similar equivalent in your vicinity. Would prefer 100% wool as I think it sounds the best but the above can usually had for 1/3 the price. An acceptable compromise. I know it sounds better but I wish someone could tell me why? Just remembered Visaton that German DIY loudspeaker manufacturer sells long fibre wool damping.
 
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