cabinet dampening materials? (Off Topic)

by fu_man @, Sunday, June 08, 2008, 07:34 (3510 days ago)

I am building a trial pair of bass reflex cabinets (100 litres) using a pair of BD15's. Any recommendations of generic materials for cabinet damping? I'm thinking of using a foam carpet underlay (it's like the foam used in chairs/mattresses, which has been granulated, then bound back into a medium density sheet)
This should help damp the cabinets. I also have a Dacron type sheet too which I am thinking of lining the cabinet to help reduce standing waves.

cabinet dampening materials?

by madprofessor ⌂, 27777 Ganderkesee, Germany, Sunday, June 08, 2008, 09:47 (3510 days ago) @ fu_man

Why don´t You use the damping material, Bert supplies for the BD-15 cabinet?
I used that material in my cabinets and I´m completely satisfied!
Depending on the material, You use for the cabinet it could also be helpfull, to use bitumen-based plates underneath the mats, Bert supplies.
I use normal stuff, basical intended for roofs, heat it up with a gas-burner and stick it to the walls of the cabinet.

cabinet dampening materials?

by fu_man @, Monday, June 09, 2008, 03:40 (3509 days ago) @ madprofessor

Why don´t You use the damping material, Bert supplies for the BD-15 cabinet?

I may yet, but at the moment I am knocking up temporary boxes basically to trial. if i were making the BD refs then no question I would make to the exact recipe including the exact ingredients!

I'm thinking I may just leave this all out for now until i get the box about the right size/shape.

I use normal stuff, basically intended for roofs, heat it up with a gas-burner and stick it to the walls of the cabinet.

I wonder if this is similar to the "Malthoid" ma trial i use outside for a damp proof course between concrete and timber?

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cabinet dampening materials?

by Bert @, Monday, June 09, 2008, 10:30 (3509 days ago) @ fu_man

Hi Fu_man,

I may yet, but at the moment I am knocking up temporary boxes basically to trial.

100 liters is a bit small for the BD15's...120 liters (internal volume) would be minimal for a reflex system.

In principle you do not need damping material except for the walls to reduced standing waves. This should be relative thick for some success though...better would be a nice ratio as box dimensions to prevent doubling resonance effects.

Either way, experiments will be needed anyhow (port tuning and the amount of filling material you need for your room and taste). Some like the bass boomy, others extremely dry....your choice.

Bert

--
BD-Design - Only the Best!

cabinet dampening materials?

by GC, Monday, June 09, 2008, 12:35 (3509 days ago) @ Bert

Don't forget to address the freq. range the cabs are to cover. 200Hz and 1000 Hz is not the same.

I always use uneven sized celluar structures inside my bass cabs. Just as the Swings. That cancels standing waves.
Hardly any dampning should be applied then for freq < 500 Hz.

:grin: GC

anyone tried a BD15 in transmission line

by fu_man @, Thursday, June 12, 2008, 12:34 (3506 days ago) @ Bert

yes, thanks for the advice.
A guy i know did some computer modelling using a 130lt and 100 litre enclosure and thought I could probably get away with 100 litres for what he thinks i need... but still he said i need to test it. it's a starting point and I don't have much time these days to play - so I'm taking my time and have knocked together cheap box first. It's walls are thin but i might try damping them externally for testing. (eg sand bags)The ratio of the box should be pretty good... I worked out a size using some reference 'golden ratio.'


I like the idea of trialing a transmission line too but it might be a bit beyond me really. Seems that to tune to 35hz would start with a 8m wave length... then for a 1/4 wave would need a 2m long enclosure... according to Jon Risch's notes wool stuffing slows the sound to about half speed making the length look twice as long... so therefore would need only a 1m long 'tube'... somehow that just doesn't seem right. Mind you a 1m long tube with the internal sectional area equivalent to the area of a 15inch driver is still quite a lot of bulk!

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anyone tried a BD15 in transmission line

by Bert @, Thursday, June 12, 2008, 14:52 (3505 days ago) @ fu_man

Hi Fu_man,

...so therefore would need only a 1m long 'tube'... somehow that just doesn't seem right. Mind you a 1m long tube with the internal sectional area equivalent to the area of a 15inch driver is still quite a lot of bulk!

No, this is not right. Damping material does delay but not more than 10-15% and on top of that the length seems longer (about 15cm) due to the speed of the air at the exit of the line. This is all you'll gain and if you do make a TL then have the exit minimal 450cm^2...

Still "bulk" though but it can work well with the BD15's... :wink:

Bert

--
BD-Design - Only the Best!

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