[BrunoB]

I have been looking for quite a while for alternative stuffing materials to adsorb the sound in the ribbon panel enclosure. My latest finding is Miraflex.

Miraflex is a relatively new type of fiberglass. It is itch free and cotton like . Unlike normal fiberglass, it has no added binder and the fibers have a random arrangement. The fibers are much thinner than wool or some other artificial fibers (Dacron, PolyFil, AcoustaSuff, ...). The thinness and the random arrangement of the fibers help sound adsorption. At least, that's my theory.


http://www.owenscorning.com/around/insulation/products/miraflex.asp

http://ldsg.snippets.org/appdx-b.php3#STUFFING


I bought mine at Lowe's for about $20 for one R25 roll. I used 113 g (1/4 LB) per neopanel for one of my 626R, packed at the bottom, loose at the top (close to the panel). I have put 76 gr in the other speaker for comparison. I can't comment much on the sound yet. But I like it so far.

Bruno

[audiochef]

Bruno,

please post findings in comparion to wool . I'm willing to bet it won't be asgood in the long run.
 
Thanks,Stan

[BrunoB]

Bruno,

please post findings in comparion to wool . I'm willing to bet it won't be asgood in the long run.
 
Thanks,Stan

Preliminary results:
1) comparing the my speaker with 76g of miraflex to 106g  wool:  miraflex has less brightness than wool.
2) comparing the my speaker with 76g of miraflex to 113 g  of miraflex: 113 g has less brightness.

I have the impression to hear new details with miraflex. But this effect might be due a slightly  different tonal balance.

Bruno

[jonbee]

Thanks for the info, Bruno. Any thoughts about Miraflex vs. dacron? Also- about how large is a 113 g. piece of Miraflex?Tnaks, John

[BrunoB]

Thanks for the info, Bruno. Any thoughts about Miraflex vs. dacron? Also- about how large is a 113 g. piece of Miraflex?Tnaks, John

John,

I have never seen and touch Dacron. I think it is a polyester fiber like Polyfil or Fiberfill. But I don't think it has the random arrangement of the fibers that I think it is important.

113 gr of Miraflex is quite larger than the volume of the 626 enclosure. You have to pack it quite well to fit in the enclosure because it is an expansive resilient fiber. The same amount of wool (or Fiberfill) requires a lot of packing as well.
Note that 113 gr of fiber glass takes less air volume from the enclosure than the same amount (mass) of wool or other organic material. Glass (pure solid glass) has a density of 2.6. Wool about 1.1 (estimated from Nylon).  113 gr of glass needs about 43 cm3 of volume whereas 113 gr of wool takes about 103 cm3 of volume. The volume of the 626 enclosure is about 2300 cm3 (2.3 l).

I believe that the amount of stuffing material is as important as the nature of the material used. And it is not easy to find the right combination.

Bruno

[BrunoB]

Here are two plots coming from the web page Bradbury's Fiber Equations . The first one is about change of sound speed .

Unfortuantely, these plots are related to transmission lines and not to sealed enclosures like the VMPS mid panels.  I don't have any expertise in this field but I found them interesting because they show how two fibers made of the same material (both Miraflex and Fiberglass are made of glass) can affect sound differently.

[BrunoB]

I believe that the amount of stuffing material is as important as the nature of the material used. And it is not easy to find the right combination.

Beside stuffing material and amount, I have found a third factor that influences the sound coming out of the midpanel: the way the fibrous material is packed.

I tried two different packing directions:
1) perpendicular to the driver , this is the usual way, the stuffing material is packed at the bottom of the box (assuming that the speaker is laying on the floor with the driver on top).
2) parallel to the driver, the stuffing is packed against the lateral side of the enclosure.

(1) and (2) sound different. (2) has more brightness than (1).

These results apply to Miraflex. My guess is  that this is also true for other stuffing materials.

The only explanation I could find is that that in the first case, the fibers are packed in the same direction as the sound wave coming out of the back of the mid panel.