Insulation question

[bldozier]

http://www.audioheritage.org/vbulletin/showthread.php?36631-My-JBL-4355-build
My project is nearing completion I saw this thread my eyes popped out of my head.
Has anyone else tride the ikea pillow or suitable replacement idea. How did the
Pillow keep from toppling over.

70765

[Ed Zeppeli]

I am hoping that you mean, "How do you fasten the pillows (as insulation) when installed inside the cabinet?"


Yes?

[Mr. Widget]

Are you seriously considering this?

I would assume the pillows are filled with polyester batting, upholstery foam or a combination of the two. Wrap-on fiberglass or Ultra-touch denim are both superior from a performance standpoint. I would use one of these products after spending so much effort on your project.


Widget

[Challenger604]

I can't believe this question!! Flabbergasted!!!

[Horn Fanatic]

http://www.audioheritage.org/vbulletin/showthread.php?36631-My-JBL-4355-build
My project is nearing completion I saw this thread my eyes popped out of my head.
Has anyone else tride the ikea pillow or suitable replacement idea. How did the
Pillow keep from toppling over.

70765

Ikea pillows are stuffed with either, feathers, memory foam, or polyester. Neither of which are suitable as damping material in a speaker enclosure. All the feathers and memory
foam will do is decrease the internal volume of the cabinet, whereas fiberglass insulation changes the air density of the cavity as to acoustically increase the volume. I would
be hard pressed if you could find any worthwhile acoustical measurements on pillows. As I have never used polyester in my enclosures, what I have read about polyester batting, is that
it is so acoustically transparent it provides very little damping. This was also confirmed back in the late 70's by an old associate of mine who built cabinets for Tychobrahe.
The typical damping material used in loudspeaker cabinets introduce an acoustical impedance which is also another element in the acoustical circuit of a loud speaker system.

I agree with Mr. widget. Fiberglass or the cotton material should be the material of choice. Using the cotton material however will take a bit of experimenting, as using too
much can suck the life out of your woofers. I would recommend using no more than 1" thick material.

H.F.

[speakerdave]

There is wrap on 1" thick Fiberglas insulation which is much less onerous to handle than wall stuffing. It can be purchased from a jobber in Chicago called Atlas.

[Challenger604]

Forget about pillow joke! Get a roll of fiber glass at Home Depot for $20 and you're done!! Enough!!

[bldozier]

I am hoping that you mean, "How do you fasten the pillows (as insulation) when installed inside the cabinet?"


Yes?

Yes.

Im not sure what ultra touch denim is. With the close quarter confines, of the cabinets and my bed, I though an alternative maybe in order. When I hadd the sole 4333 it stunk. I hade to take that stuff to the trash, until the project was over.

[Horn Fanatic]

Yes.

Im not sure what ultra touch denim is. With the close quarter confines, of the cabinets and my bed, I though an alternative maybe in order. When I hadd the sole 4333 it stunk. I hade to take that stuff to the trash, until the project was over.

The denim material sold at Home depot is I believe 4 inches thick. Don't go there. Here is a link to the outfit I purchase damping material from. They have a wide selection of one inch thick material. I have been using their material for ten years.

http://www.bondedlogic.com/

http://www.bondedlogic.com/acoustical-products/

Good luck,

H.F.

[bldozier]

Gottcha. The stuff I saw is 2" 16x48 in 5 packs. I was thinking id need to halve it. But I will do your website referral.
Thanks.

[Horn Fanatic]

Gottcha. The stuff I saw is 2" 16x48 in 5 packs. I was thinking id need to halve it. But I will do your website referral.
Thanks.

I am not one to use liberal quantities of damping material, as sometimes it can do more harm than good. There is one product I manufacture where I use 1 inch thick duct board.
It's a cabinet loaded with the GPA 604 8H III. I found that even using the 1 inch Bonded Logic material makes that particular speaker sound muffled in the mid-range. I would suspect
it may have a similar effect on your monitor components to one degree or another if used too generously. I typically shy away from using fiberglass insulation in vented enclosures for
no other reason that it is made of glass. Over time, glass particulates find their way out of the vent. As I stated before, experimentation would be in order rather than just stuffing and enclosure with 'stuff'.

Please keep us posted on your project.

H.F.

[David Ketley]

I din't know the availability in the US but wool is by far the best damping material.

I have found the amount and density of the fill is critical there is a huge difference in performance and I believe that fill is treated far too casually.

Fibreglass is no where near as good.

B&W did extensive research into various fibres years ago and concluded that long haired teezed pure wool was best for bass damping.

[bldozier]

What about carpet felt padding

75226

[David Ketley]

Possibly too dense and whats it made of? May help as a panel damping material?

Some home insulation products in the UK have a high amount of wool in them but you will need to knock the dust out of them before using them.

Compared to fiberglass they are a vast improvement.

See: http://www.qtasystems.co.uk/articles/how-to-damping.htm

[Ruediger]

What about carpet felt padding

75226

Molecules in motion can be slowed down by the damping material. Motion means "sound particle velocity", not to be confused with the speed of sound. The german word is Schallschnelle or just Schnelle.

For standing waves - and these are the only ones you care about - the particle velocity at a wall is zero, and the pressure is at its maximum. A quarter wave away from the wall the pressure is at its minimum and the particle velocity is at its maximum.

If you were building absorbers for your listening room from sheets of rockwool you could make them more efficient by mounting them at some distance away from the wall.

This kind of "damping" does not significantly change the "Q" of your system, and that is what we want.

A completely different scenario is when you have a boom box where you want to damp resonating bass modes (the mass / spring system which makes up your box). Such speakers are not discussed in this forum :)

Ruediger

[bldozier]

Im looking 4 cleanliness, and ease of use, so wipe felt padding from the list?

[Ruediger]

Im looking 4 cleanliness, and ease of use, so wipe felt padding from the list?

For damping to work the soundwave must penetrate the damping material, and this requires the damping material to have "similar" acoustical properties as air. If the properties are very dissimilar, the sound wave will just get reflected (w/o absorbtion) at the boundary of air in the box and damping material.

You sure have seen pictures of anechoic chambers with lots of tetraeders on the walls made from foam. A soundwave approaching such a wall will see slowly varying acoustical properties and thus will not get reflected but propagate into the "foam wall" and will get absorbed.

Felt is much too dense.

As a rule of thumb the absorbing layer should have a thickness of 1/4 the wavelength of the sound waves to be damped, or more, if feasible.


Ruediger