Should I replace the sound absorbing material inside my speakers?

[Mika75]

I've read alot about Rockwool and its absorbing/attentuating properties, so I'm wondering would I there be any difference changing the 30mm foam out and replacing it ?

This is a shot from inside the speaker looking up, there's also lead lining underneath the foam throughout.

 

[lsiberian]

I've read alot about Rockwool and its absorbing/attentuating properties, so I'm wondering would I there be any difference changing the 30mm foam out and replacing it ?

This is a shot from inside the speaker looking up, there's also lead lining underneath the foam throughout.

Yes rockwool would improve your speakers. When doing that I suggest also adding a few rib braces on every axis. by bracing the speaker you will raise the panel resonances.

Make sure to cover the wool with cloth.

 

[Mika75]

Yes rockwool would improve your speakers. When doing that I suggest also adding a few rib braces on every axis. by bracing the speaker you will raise the panel resonances.

Make sure to cover the wool with cloth.

Improve in what way though ?

The rib braces would alter the cabinet volume thus change the bass response slightly i would think.

ps. I don't think it's necessary to quote the pic twice, it's big enough the 1st time

 

[lsiberian]

Improve in what way though ?

The rib braces would alter the cabinet volume thus change the bass response slightly i would think.

ps. I don't think it's necessary to quote the pic twice, it's big enough the 1st time

Not enough to be significant in most cases.

It takes a huge change in volume to make an audible difference in the bass. To observed this I suggest you model a midrange driver and alter the volumes in winisd just to get an idea.

Sound aborpstion reduces the energy inside the box. And the distortion introduced by it. Giving a cleaner sound. To understand you should try it and see what you like. To have a reference speaker requires lots of bracing and heavy dampening. This is why they are so expensive. See Matt34's Infinity Primuses for a demo of ultimate bracing and damping.

 

[WmAx]

While lisberian is correct about the ratio of internal volume needing to reduced substantially to make much of a response difference, he forgot to mention the effect caused by a 'super' absorber like 4-8# rockwool board. The material has such a high co-efficient, that if you use too much, it will critically dampen the LF response. That is, it will actually cause the LF to roll off radically, and very smoothly, replicating the sort of response one would expect from an infinite volume of air behind the driver. So, use just enough of the material to provide maximum mid-range absorption, but no so much that is actually removes much LF response, unless you have an electronic means of correction (such as a parametric equalizer) available to compensate the response loss.

-Chris

 

[Mika75]

ok, so it can be done... now is it worth the trouble in changing it out, or the change will be negligible?

 

[WmAx]

ok, so it can be done... now is it worth the trouble in changing it out, or the change will be negligible?

I can't answer that for certain; it's dependent on your particular speaker. It makes a considerable difference in MOST speakers.

-Chris

 

[annunaki]

It takes a huge change in volume to make an audible difference in the bass. To observed this I suggest you model a midrange driver and alter the volumes in winisd just to get an idea.

If the enclosure is vented relatively small changes in a smallish enclosure can have a big impact on the Fb or tuning of said enclosure. Depending upon the driver, one could cause an unwanted hump in response.

 

[Mika75]

Yes annunaki ur correct it's a ported design, the speakers are in my avatar atm.

 

[annunaki]

I would pick up some mineral wool sheets (rock wool), pull out the old, put in the wool and note any differences. The wool is not extremely expensive so you would not be out much for the "experiment".

If you really wanted to improve the speakers, perhaps you could calculate the internal volume, note the vent length, and construct new, non-resonant enclosures using a constrained layer damping system with rigid internal bracing. This would dramatically increase the quality of sound ridding the system of nearly any audible resonances. One could also implement a low velocity vent as opposed to the current port tube to help with high output dynamics and lower port compression. However, in doing so one would have to consult with the manufacturer to ensure the crossover does not implement a notch filter to offset the current vent resonance. If no such filter is currently present, this would be the route to pursue. They would probably sound like a different (better) set of speakers.

Other than that, you can simply do as stated above. If you added bracing, one could calculate the pre-alteration volume & vent length (tuning frequency), then could calculate the volume displacement of your added bracing and simply increase the vent length to ensure the proper tuning. The small volume loss associated here should have minimal overall effect.

 

[lsiberian]

I would pick up some mineral wool sheets (rock wool), pull out the old, put in the wool and note any differences. The wool is not extremely expensive so you would not be out much for the "experiment".

If you really wanted to improve the speakers, perhaps you could calculate the internal volume, note the vent length, and construct new, non-resonant enclosures using a constrained layer damping system with rigid internal bracing. This would dramatically increase the quality of sound ridding the system of nearly any audible resonances. One could also implement a low velocity vent as opposed to the current port tube to help with high output dynamics and lower port compression. However, in doing so one would have to consult with the manufacturer to ensure the crossover does not implement a notch filter to offset the current vent resonance. If no such filter is currently present, this would be the route to pursue. They would probably sound like a different (better) set of speakers.

Other than that, you can simply do as stated above. If you added bracing, one could calculate the pre-alteration volume & vent length (tuning frequency), then could calculate the volume displacement of your added bracing and simply increase the vent length to ensure the proper tuning. The small volume loss associated here should have minimal overall effect.

I like the ideas here, but as with anything it comes down to how much effort one really wants to put in this. I find it hard to finish projects so I would never do something like this to existing speakers. But if your the kind of person that moves quickly then modding speaker may be your thing. For me I'm better off starting from scratch since I take my sweet time to get things done.