Originally Posted by bluemonkeyflyer
BMF 6 v2:
I received my shipment of AcoustiPack Lite (thanks AnotherNoob for the link) and wanted to compare it with Paxmate Plus.
EDIT: The photos, below, are of BMF #5. BMF #6 is described in post 3952 at the following link: http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3945 BMF #6 has 1 layer of Dynamat Xtreme on the ear side of the baffles but it is the same as BMF #5, internally.
CAUTION: Be very careful when removing reflex dots from the white driver felt (or paper). Furniture bumpers from the same package vary in their adhesive strength. I made a small tear in the white driver felt when removing one of the bumpers despite being careful and using my X-acto knife to slowly lift the edges and prise it off. Luckily, it was no bigger than the end of a ball point pen and located over one of the grid lines instead of one of the openings. I was able to use a bit of glue to make the repair.
Procedures for BMF 6 v2:
1. Place Dynamat Xtreme on both sides of the central section inside the cups. Make sure the Dynamat is pressed down firmly and fully attached to the plastic cups.
2. Apply AcoustiPack Lite over cup Dynamat, cup walls, and the 1" square at the top, opposite the bass ports. Make sure it's pressed down firmly and fully attached to the Dynamat and plastic cups. Leave the central screw compartment uncovered. If you have too much treble, you can later tune it down by covering the central screw compartment with AcoustiPack Lite;. You may be able to "dial in" the treble by covering some or all the central screw compartment.
3. Leave the white driver felt in place.
4. Leave the black bass port felt in place and otherwise uncovered for your first test. You can later tune the bass by covering some or all of the bass port vents to suit your preferences. I like them uncovered except for the stock black felt over the bass vents, inside the cups.
5. Leave the dust cover over the drivers in place. I previously chiseled off the dust cover surrounding the ear side of the drivers. Some have found removing the dust cover from the ear side of the drivers increases treble and detail. I did not.
6. Leave the baffle equalization vents open.
7. Super mass load the back side of the baffles with plasticine. Do not fill the main baffle equalization vent and the other three semi-open baffle vents with plasticine.
8. Apply 2 layers of Dynamat Xtreme surrounding the drivers on the ear side of the baffles.
9. Apply two layers of aluminum duct tape over the second layer of Dynamat. Note: Here's a handy method for applying this tape - cut to length, position across adjoining sections of Dynamat, and slice away the tape with an X-acto knife by following the curvature of the Dynamat.
10. With ear pad removed, make a stencil of the baffle by positioning a clear sheet of overhead projector acetate over the ear side of the baffle. Looking through the acetate, outline the inner oval and the driver square using a magic marker pen. Cut it out and use the acetate stencil to make a stencil of stiff cardboard stock. Use the cardboard stencil to mark the back and cut out the adhesive-backed black felt, then apply over the Dynamat. Notch an opening for the baffle equalization vents.
11. Make cotton gauze "ropes" and place one under the back half of each ear pad. It's a good idea to first tape the back half of each ear pad to the cup to prevent the ear pad from coming off. This is a temporary measure while testing. A semi-permanent solution is to use double-sided tape under the ear pads. SQ can be tuned by varying the length and diameter of the gauze ropes.
EDIT: As others have reported, simply lifting the back half of the ear pads may improve SQ and soundstage. You may be able to reap benefits by tuning the ear pads with gauze, cotton balls, or fiberfill; changing the amount and size of "rope lifters", going only half way around, or differentially lift all the way around the ear pads.
12. Test and tune to suit yourself.
Comparison Phones - Identical to BMF 6 v2 except for the following:
1. One layer of Dynamat surrounding the drivers.
2. Paxmate Plus instead of AcoustiPack Lite.
Careful A/B comparisons were made with SPL matching, lossless files, MacBook Pro, and glass toslink to Dacmini DAC and amp. I really like BMF 6 v1 but BMF 6 v2 has a bit more detail, better vocal clarity, more treble sparkle with air and without harshness, and cleaner bass. These comparisons are not as specific as my previous comparisons because there are at least 2 variables involved instead of 1. The noticeable SQ differences of BMF 6 v2 may be due to AcoustiPack Lite, a second layer of Dynamat surrounding the drivers on the ear side of the baffles, an unknown/uncontrolled "Factor X", or the synergy of 2 or all 3. I suspect that the main factor, however, is the different acoustic foams used --> Paxmate Plus vs AcoustiPack Lite.
Edit: After more extended listening comparisons, I would not say #6 v2 is necessarily better than #6 v1. Instead, v1 and v2 offer different "flavors." #6 v2 sounds crisper while #6 v1 sounds warmer. These differences are slight but noticeable. v2 is heavier than v1. "Pad lifting" is the easiest reversible mod to make. Changing the amount and the placement of padding under the ear pads makes a remarkable difference in bass quantity/quality and treble sparkle.
Note: AcoustiPack Lite and Paxmate Plus are each 4 mm thick and about the same in terms of ease of application. The difference is that AcoustiPack is heavier due to the constrained layer and purportedly has better sound absorption. Perhaps it soaks up more reflections, reduces standing waves, and further limits the amount of dirty waves sent back through the drivers to your ears?
I have some different materials on the way for more experiments. I'll post the results whether favorable or not.