damping material: foam vs fiberglass

[noviygera]

I am refurbishing some Meyer Sound UPA1 speakers and ordered replacement damping pads.

The older Meyer used two yellow 1" fiberglass pads. The replacement pads I received are now egg crate foam.

What is the better material to use? fiberglass or foam? Is there a significant difference in performance?

thanks.

 

[wiseoldtech]

I refuse to use any type of foam simply because over time it dryrots and makes a mess inside a speaker cabinet.

 

[noviygera]

Assuming it will last 10 years, are there performance and sound differences?

 

[TBTL]

Glass wool is one of the best 'wool-like' damping materials, when looking at acoustic damping. It also remains stable for a long time. It does however itch and there are health concerns, so these days it is not commonly used in (ported) hifi speakers.

That said, foam probably is fine as well acoustically for lining a cabinet wall. Wall lining puts different demands on the damping material than volume filling (wool-like) material, so the foam might even work better. How long the foam lasts strongly depends on the exact material composition. Not all foams are equal.

Why do you want to replace the original glass wool?

 

[Think]

As this is a ported cab, Rockwool. (mineral wool, mineral fiber) It is similar to fibreglass wool but a lot less irritating to hands and lungs.


Old pillow or duvet/comforter (?) will also work but cotton can mold.

 

[Damo s]

Or perhaps a bit of both. The more variation in the density of the dampening material the better it will perform.

 

[turk 182]

where are the pads located? i take it that this is inside? can't see why a company of Meyer's reputation would send you material that would potentially compromise the performance of their product even though it's legacy stuff.

 

[Galu]

Are the pads damping the walls of the enclosure or the response of the driver?

Assuming the latter:

Acoustic foam is used to alter the high frequency response of cabinets. It does not work well for low frequencies as the amount of energy absorption which the foam offers is relatively small.

The heavier structure of fibreglass should extend its influence in sound quality to lower frequencies than foam.

 

[tommus]

I built a vented main cabinet with 1/2" Baltic Birch ply and lined the walls with a vinyl damping/foam product called Sonic Barrier. So far so good, but still the midrange was quite edgy from reflected backwave through the cone (the cabinets are somewhat shallow) I got some mesh laundry bags at the dollar store (the kind you use to put delicate stuff into the washer) and stuffed lightly with with the fiberglass. The glass fibers are contained and you can staple the bag in to a partition in the middle of the cabinet, away from the walls, which is the best place to attenuate standing waves. I placed it halfway between the woofer cone and the back of the cabinet. You don't need much and most of the cabinet volume is still "empty." This really made a great difference. I will continue to use this combination of damping and stuffing for PA cabinets.

This article set me in the right direction:

Volume filling a reflex box

 

[Think]

Thank you for the great link.


" Conclusions

While in no way claiming these tests to be definitive, it does appear that a reflex box can be filled by a medium density fibrous material and that it is beneficial to cover the inner surfaces with acoustic foam. The effect upon the box Q is minimal and the re-radiation through the cone and the port is reduced significantly."

To bad that website is hard to navigate. Other pearls I have found there:
- PA Systems - Public Address Systems for Music Applications
- Loudspeaker Power Handling Vs. Efficiency
by Rod Elliott (ESP)

 

[tommus]

I forgot to add that fiberglass is significantly better than wool, cotton, or poly because of it's small fiber size (as shown in that link) and I think it's well worth the effort to use it (safely).

 

[MAAC0]

Wrap the fiberglass in cloth before stamping it to the walls, so You won't breath it.
There is that thin white wrap stuff used in bed clothing. Sometimes it is also used for factory wrapping HI-FI stuff or laptops. I don't mean the plastic one, but the "felted" one.

 

[phase]

I like this stuff:

Armacell Product Selector - AP ArmaFlex, AP ArmaFlex FS - Duct Liner and Wrap Insulation

 

[noviygera]

Meyer UPA1P:
12" woofer + horn, 90hz and up
heavy, rigid small ported box
I believe the 2 small damping pads are being used as cabinet wall liner and NOT volume filler.


TBTL,
I do not want to replace glass wool and that is what is used in the older version of Meyer UPA1. I am now restoring a newer (currentO version) UPA1p. This version does not use glass wool and uses foam, foam that that has dry rotted. And since I am about to replace the dry rotted foam, I guess I have an option to use new OEM foam or consider other damping material. Felt, glass wool, foam, rock wool, etc...


turk 182,
the two damping pads are used on the left and right inside walls.

I wonder if there is a good reason why Meyer switched to foam liner and not 8mm felt liner....

 

[wiseoldtech]

Meyer UPA1P:
12" woofer + horn, 90hz and up
heavy, rigid small ported box
I believe the 2 small damping pads are being used as cabinet wall liner and NOT volume filler.


TBTL,
I do not want to replace glass wool and that is what is used in the older version of Meyer UPA1. I am now restoring a newer (currentO version) UPA1p. This version does not use glass wool and uses foam, foam that that has dry rotted. And since I am about to replace the dry rotted foam, I guess I have an option to use new OEM foam or consider other damping material. Felt, glass wool, foam, rock wool, etc...


turk 182,
the two damping pads are used on the left and right inside walls.

I wonder if there is a good reason why Meyer switched to foam liner and not 8mm felt liner....

Cheapening-cutting costs.
It's now many things are made today.
And its a crime.

 

[mark100]

Cheapening-cutting costs.
It's now many things are made today.
And its a crime.

Ha-ha...I guess you don't know Meyer...
They typically go out of there way to use more expensive components !!!
Great gear....

 

[noviygera]

Exactly. So I think I'd like to know this: Is foam necessarily inferior to felt or fiberglass? Or is it a matter of system design invoicing where foam can be just as effective?

 

[mark100]

Exactly. So I think I'd like to know this: Is foam necessarily inferior to felt or fiberglass? Or is it a matter of system design invoicing where foam can be just as effective?

No clue.... whether inferior or perhaps superior.
But I've also seen the foam in my pair of 1P's.
I guess you're looking to use felt instead, to help gain room for a plate amp??
(If so, I'm the guy who mentioned the ice-powers on other forum )

 

[wiseoldtech]

Ha-ha...I guess you don't know Meyer...
They typically go out of there way to use more expensive components !!!
Great gear....

After decades of doing service on thousands of products related to audio and video, I'm quite aware of what's happening in the industry.
And profit margins are one of the things in the forefront of manufacturing these days.

 

[TBTL]

So I think I'd like to know this: Is foam necessarily inferior to felt or fiberglass?

No. If foam would be an inferior material, the loudspeaker designers would have specified it to be thicker, to obtain the same damping effect.