damping material inside of a ported sub ???

[dvjorge]

Hi guys,

My JBL PB-12 didn't bring any damping material inside the box. Could benefit the sound adding some damping???
Thanks,
George.

 

[TLS Guy]

Hi guys,

My JBL PB-12 didn't bring any damping material inside the box. Could benefit the sound adding some damping???
Thanks,
George.

If the sub was designed that way adding damping will change the tuning as the box will seem larger. You have to be careful not to kill box resonance (Fb) with damping and never cover more than 50 % of the internal surface.

It might help to put some mineral wool on the panel behind the driver to reduce reflections.

 

[ameuba10]

hmmmm im curious as well

 

[darien87]

If the sub was designed that way adding damping will change the tuning as the box will seem larger. You have to be careful not to kill box resonance (Fb) with damping and never cover more than 50 % of the internal surface.
It might help to put some mineral wool on the panel behind the driver to reduce reflections.

Uh-oh. Can you tell me why this is? With my latest DIY sub, I pretty much covered all of the inside walls with polyfill.

 

[j_garcia]

Uh-oh. Can you tell me why this is? With my latest DIY sub, I pretty much covered all of the inside walls with polyfill.

That sub is a passive radiator design though. I am not sure the same applies? I don't think you need quite that much in a PR design.

 

[TLS Guy]

Uh-oh. Can you tell me why this is? With my latest DIY sub, I pretty much covered all of the inside walls with polyfill.

Was your sub ported or sealed?

In general you use light fill with ported designs, or for subs even no fill except Rockwool to abate driver reflections. The same applies to ABR designs.

A ported speaker is a resonant speaker. There is an interaction between the box resonance Fb and the driver free air resonance Fs. If you kill Fb with too much fill then the design will not work. So for ported enclosures the recommendation is to cover no more than 50% of the internal surface area with adsorbent material.

Sealed enclosures on the other hand require heavy fill as you want to kill Fb.

I hope this helps.

 

[darien87]

Was your sub ported or sealed?

In general you use light fill with ported designs, or for subs even no fill except Rockwool to abate driver reflections. The same applies to ABR designs.

A ported speaker is a resonant speaker. There is an interaction between the box resonance Fb and the driver free air resonance Fs. If you kill Fb with too much fill then the design will not work. So for ported enclosures the recommendation is to cover no more than 50% of the internal surface area with adsorbent material.

Sealed enclosures on the other hand require heavy fill as you want to kill Fb.

I hope this helps.

Mine is sealed with 2 PR's.

 

[TLS Guy]

Mine is sealed with 2 PR's.

A Pr is not a sealed speaker. It is just like a ported speaker with the same physics. The PR just replaces the port. So the same damping rules apply equally to them as ported. You do not want to kill Fb.

 

[lsiberian]

Uh-oh. Can you tell me why this is? With my latest DIY sub, I pretty much covered all of the inside walls with polyfill.

As long as you aren't more than 2" Thick you should be alright. I still suggest just treating the back wall with subs. Even a sealed sub can be stuffed on the back wall and get most of the benefits.

4" of rockwool on the back wall is all I'd put in a sub. For sealed it works out to be plenty due to the volume occupied and for ported it won't dramatically lower the Fb.

P-Rs are ported subs.