bluemonkeyflyer
Headphoneus Supremus
- Joined
- Jan 20, 2011
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This is one of the most interesting posts I've read - thank you!
The topic of variable layering of least dense materials closest to the driver to most dense materials at the internal cup surface for reducing reflections has been discussed on this forum, but not in as much detail as you described in your post. Dynamat and other materials have been tried on the internal cup surface and covered with less dense materials including open cell acoustic foam, cotton, fiberglass, etc., with consequent reduction of cup volume that may affect the sound. Several people, myself included, have tried Dynamat in the cups with a covering of Paxmate or similar acoustic foam. I did not hear any difference compared to Paxmate, alone. I don't remember if anyone else posted their impressions with this configuration. Armaegis pointed out that Dynamat may add mass loading to the cup if placed on the internal cup surface but would not result in reducing reflections because its constrained layer is not against the cup surface and is essentially mounted backwards from its intended design. (Armaegis: correct me if I am mistaken about what you said.) This got me to thinking about how to better (?) make use of Dynamat. On BMF 5 and 6 mod configurations, I removed the dust cover and its adhesive residue from the ear side of the baffle surrounding the driver. Next, I placed Dynamat on the exposed plastic surface surrounding the drivers. To diminish reflections from the metallic-looking Dynamat constrained layer, I covered it with self-adhesive felt.
Armaegis, and I think leeperry (?), commented that I over-damped the backs of the baffles by using too much plasticine and suggested using tungsten putty or lead shot. BTW, to my ears there are advantages to this "super mass loading" about which I've already commented that may be offset by excessive weight. I researched tungsten putty and found it available for $10 to $15 per oz from various venders - mostly for pinewood derby cars and fishing. I found fishing tungsten putty for about the same price and decided to formulate my own. I applied my formula to the back of the baffles in various quantities and placements and posted the results. A week or so later, I wanted to compare my homemade tungsten putty to a commercial product. I ordered Kryston Heavy Metal Extra and quickly concluded that it is too hard, too dense, and too expensive to be feasible for our purposes - see post 4513 for comparative weights of plasticine, my tungsten putty (current formula), Kryston tungsten putty, stock T50RP, "Less Is More" mod, and "Transpore 1.5" mod.
Several weeks ago mrspeakers posted a mod that includes filling the cup outer rings with plasticine to produce a better seal. I don't remember who posted a mod including Paxmate in the cup outer rings (sorry). I have one mod with plasticine and another with Paxmate in the cup outer rings. I don't know if these mods make a sonic difference, or not, but think they can't hurt as long as they don't stress the cups' plastic threads. To this end, I always apply pressure to compress the baffle and cup when removing the 4 baffle screws and avoid over-tightening the screws when putting the cups/baffles back together.
AnotherNoob provided a link a couple of weeks ago for a manufacturer of another open cell acoustic foam product - AcoustiPack Lite - which has similar foam as Paxmate Plus mounted to a constrained layer. I bought some and tried it with similar, but slightly different, results compared to Paxmate. To my ears, Paxmate offers a warmer sound to AcoustiPack's more analytic sound. Further visual and tactile comparisons show that AcoustiPack Lite is heavier than Paxmate Plus but it's open cell foam is only about 50% that of Paxmate; both are 4 mm thick.
After reading your post, I am now going to place AcoustiPack Lite in the cup bottoms (not the sides) to take advantage of its constrained layer (most dense layer the greatest distance from the back of the drivers). Next, on top of the AcoustiPack I am going to add 1 layer of Paxmate (not the sides) to take advantage of its (I presume) less dense and greater quantity of open cell foam in closer proximity to the back of the drivers. Everything else in my "Less Is More" and "Transpore 1.5" mods will remain the same, as described in post 4513 a few pages back, including 1/2 of one medium cotton ball loosely teased and placed between the Paxmate and the back of the driver - the least dense material closest to the back of the driver.
A few months ago I noticed that only 1 of the 4 baffle holes surrounding the back of the drivers is actually open all the way through to the other side of the baffle. I assumed this was designed as a means of equalizing the pressure between the cup chamber and the ear pad-to-head chamber. I referred to this single open hole as the pressure equalization vent - but that's just my layman's wilda*s guess. I remember probing the other 3 holes around the driver using a paperclip and was stopped by what I assumed at the time was the baffle dust cover. I thought that they were purposely designed with the dust cover over them as a means of, as you just described, controlling the resistance or back pressure. Two days ago, I was looking at these 3 holes and thought this is another potential mod to explore. So, I decided to open them by using a needle to make a pilot hole and then push a paperclip all the way through the dust cover to widen the baffle opening to the same size as the driver holes. To my surprise, this was not possible because they are not open at all; I hit the plastic baffle instead of the expected dust cover. So, I got out my drill and used a 1/16" bit that is just large enough to fit the inside diameter of the driver "vent" holes. I drilled them out making them actual open vents so that there are now 4 open baffle vent holes instead of just one. I have been playing around with them fully open, fully closed with tape, and partially open covered with thin felt. I have not yet tested all permutations of # of holes X fully open X fully closed X partially closed with a layer of thin felt over them on the ear side of the baffles. I did, however, notice right off a change in the the SQ and what seemed like more bass when all 4 are fully open.
BTW, would you describe "bass rings?"
Keep the ideas coming.
Quote:
The topic of variable layering of least dense materials closest to the driver to most dense materials at the internal cup surface for reducing reflections has been discussed on this forum, but not in as much detail as you described in your post. Dynamat and other materials have been tried on the internal cup surface and covered with less dense materials including open cell acoustic foam, cotton, fiberglass, etc., with consequent reduction of cup volume that may affect the sound. Several people, myself included, have tried Dynamat in the cups with a covering of Paxmate or similar acoustic foam. I did not hear any difference compared to Paxmate, alone. I don't remember if anyone else posted their impressions with this configuration. Armaegis pointed out that Dynamat may add mass loading to the cup if placed on the internal cup surface but would not result in reducing reflections because its constrained layer is not against the cup surface and is essentially mounted backwards from its intended design. (Armaegis: correct me if I am mistaken about what you said.) This got me to thinking about how to better (?) make use of Dynamat. On BMF 5 and 6 mod configurations, I removed the dust cover and its adhesive residue from the ear side of the baffle surrounding the driver. Next, I placed Dynamat on the exposed plastic surface surrounding the drivers. To diminish reflections from the metallic-looking Dynamat constrained layer, I covered it with self-adhesive felt.
Armaegis, and I think leeperry (?), commented that I over-damped the backs of the baffles by using too much plasticine and suggested using tungsten putty or lead shot. BTW, to my ears there are advantages to this "super mass loading" about which I've already commented that may be offset by excessive weight. I researched tungsten putty and found it available for $10 to $15 per oz from various venders - mostly for pinewood derby cars and fishing. I found fishing tungsten putty for about the same price and decided to formulate my own. I applied my formula to the back of the baffles in various quantities and placements and posted the results. A week or so later, I wanted to compare my homemade tungsten putty to a commercial product. I ordered Kryston Heavy Metal Extra and quickly concluded that it is too hard, too dense, and too expensive to be feasible for our purposes - see post 4513 for comparative weights of plasticine, my tungsten putty (current formula), Kryston tungsten putty, stock T50RP, "Less Is More" mod, and "Transpore 1.5" mod.
Several weeks ago mrspeakers posted a mod that includes filling the cup outer rings with plasticine to produce a better seal. I don't remember who posted a mod including Paxmate in the cup outer rings (sorry). I have one mod with plasticine and another with Paxmate in the cup outer rings. I don't know if these mods make a sonic difference, or not, but think they can't hurt as long as they don't stress the cups' plastic threads. To this end, I always apply pressure to compress the baffle and cup when removing the 4 baffle screws and avoid over-tightening the screws when putting the cups/baffles back together.
AnotherNoob provided a link a couple of weeks ago for a manufacturer of another open cell acoustic foam product - AcoustiPack Lite - which has similar foam as Paxmate Plus mounted to a constrained layer. I bought some and tried it with similar, but slightly different, results compared to Paxmate. To my ears, Paxmate offers a warmer sound to AcoustiPack's more analytic sound. Further visual and tactile comparisons show that AcoustiPack Lite is heavier than Paxmate Plus but it's open cell foam is only about 50% that of Paxmate; both are 4 mm thick.
After reading your post, I am now going to place AcoustiPack Lite in the cup bottoms (not the sides) to take advantage of its constrained layer (most dense layer the greatest distance from the back of the drivers). Next, on top of the AcoustiPack I am going to add 1 layer of Paxmate (not the sides) to take advantage of its (I presume) less dense and greater quantity of open cell foam in closer proximity to the back of the drivers. Everything else in my "Less Is More" and "Transpore 1.5" mods will remain the same, as described in post 4513 a few pages back, including 1/2 of one medium cotton ball loosely teased and placed between the Paxmate and the back of the driver - the least dense material closest to the back of the driver.
A few months ago I noticed that only 1 of the 4 baffle holes surrounding the back of the drivers is actually open all the way through to the other side of the baffle. I assumed this was designed as a means of equalizing the pressure between the cup chamber and the ear pad-to-head chamber. I referred to this single open hole as the pressure equalization vent - but that's just my layman's wilda*s guess. I remember probing the other 3 holes around the driver using a paperclip and was stopped by what I assumed at the time was the baffle dust cover. I thought that they were purposely designed with the dust cover over them as a means of, as you just described, controlling the resistance or back pressure. Two days ago, I was looking at these 3 holes and thought this is another potential mod to explore. So, I decided to open them by using a needle to make a pilot hole and then push a paperclip all the way through the dust cover to widen the baffle opening to the same size as the driver holes. To my surprise, this was not possible because they are not open at all; I hit the plastic baffle instead of the expected dust cover. So, I got out my drill and used a 1/16" bit that is just large enough to fit the inside diameter of the driver "vent" holes. I drilled them out making them actual open vents so that there are now 4 open baffle vent holes instead of just one. I have been playing around with them fully open, fully closed with tape, and partially open covered with thin felt. I have not yet tested all permutations of # of holes X fully open X fully closed X partially closed with a layer of thin felt over them on the ear side of the baffles. I did, however, notice right off a change in the the SQ and what seemed like more bass when all 4 are fully open.
BTW, would you describe "bass rings?"
Keep the ideas coming.
Quote:
