BBC Thin Wall Enclosure - Ported?

[bbggg]

It seems to me that it is the combination of thin walls and heroic damping that is the "BBC way". Plain thin walling is the way to make guitars and violins.

 

[sreten]

Hi,

Some confusion but its relatively simple. Thin walls lower resonant frequency
and increase the damping effect (lowering q) of a fixed damping layer, as Q
is related to the mass ratio of the two layers. bracing in a large thin wall
damped cabinet should be used to distribute disparate frequencies mainly.

I accept what I( said earlier is not correct, but the principle is the same,
accepting bass cabinet flexure, and relatively low midrange cabinet flexure.

rgds, sreten.

 

[dabbler]

Hi,

Some confusion but its relatively simple. Thin walls lower resonant frequency
and increase the damping effect (lowering q) of a fixed damping layer, as Q
is related to the mass ratio of the two layers. rgds, sreten.

Does that mean the type of damping material is irrelevant as long as it high in mass? Would ceremic tiles be just as effective as bitumen or rubber, considering they dont "flex" as much as the latter?

There are many products like this available locally:

http://www.ebay.com.au/itm/180742717359?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

It is recycled rubber rather than bitumen.

Density is 350kg/m3
6mm thick per sheet (will need to be layered)

Will it do the trick?

 

[speaker dave]

Does that mean the type of damping material is irrelevant as long as it high in mass? Would ceremic tiles be just as effective as bitumen or rubber, considering they dont "flex" as much as the latter?

There are many products like this available locally:

http://www.ebay.com.au/itm/180742717359?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

It is recycled rubber rather than bitumen.

Density is 350kg/m3
6mm thick per sheet (will need to be layered)

Will it do the trick?

That is a fairly dense foam but not nearly the density of the tar like materials that provide better damping. It will help but would need several layers to achieve significant damping. I'm sure it is very good for its intended application (floor impact noise reduction).

Again, I'd suggest that constrained layer damping is a very high performance approach. That is where a lossy layer goes between two stiff mass layers. It absorbs the shear vibration of the two outer layers and becomes more efficient at energy absorption due to its placement. This material would be very good at that.

Ditto with ceramic tiles. They are a great way to hang mass on the walls but they don't provide damping, their inherent Q is very high. Glue them on with hard epoxy and all you've done is upped the wall mass. Glue them on with a lossy compliant layer and you've provided considerable damping.

David S.

 

[neddy999]

What Glue

Ditto with ceramic tiles. They are a great way to hang mass on the walls but they don't provide damping, their inherent Q is very high. Glue them on with hard epoxy and all you've done is upped the wall mass. Glue them on with a lossy compliant layer and you've provided considerable damping.

David S.

Can anyone tell me what glue would constitute a lossy compliant layer for ceramic tile
thanks Neddy

 

[Don Hills]

Silicone sealer? Caulking compund? Rubberised tile mastic? Anything that remains flexible when cured.

 

[RAART]

It seems to me that it is the combination of thin walls and heroic damping that is the "BBC way". Plain thin walling is the way to make guitars and violins.

Not true - see here: Onkyo D-TK10 - 2-Way Bass Reflex Speakers | Model Information | Onkyo USA Home Theater Products

I like to build/replicate this one...