Just listened to some Fostex T50RPs today... WOW!
Jun 14, 2012 at 1:14 PM Post #8,596 of 11,346
Wanna kill backwaves?
 
I've been reading the master handbook of acoustics, and trying all kinds of things, and the most effective way to diffuse irritating bass and midband distortion might be to make circular or half circular diffusors of plasticine. Just simply add the plasticine sausages in the bottom of the cup, and add mineralwool on top. You'd be surprised of the effect. I'm not yet sure If the highs are absorbed by such small amount of mineralwool, but the plasticine sausages had an HUGE effect on the irritating midband shout. If this positive effect is due to decreased cup volume (possible change in reverberations?) or by diffusion, reamins to be proved. I'm going to test this with my bigger cups containing a ****load of helmholz resonators and one inch of mineral wool.
 
Cheers. Pictures later.
 
 
Jun 14, 2012 at 1:31 PM Post #8,597 of 11,346
Quote:
 
After reading through the basic modification again, I've realized how close mine is to the latest document from BMF.  Essentially, the only difference is,
 
  1. - I have craft foam in place instead of the acoustic foam.  I do have acoustic foam and I've used it before, though.
  2. - I have plastix on my baffles and not newplast.  I just received some newplast in the mail last week, though. Yippee!
  3. - I'm using fiberglass insulation instead of cotton balls at the moment.
 
I'm assuming that the documented use of Rite-Aid cotton was the use of the cotton pads instead of the cotton balls?  From the instruction, it appears to indicated they are pressed against the insides of the cup - which would almost indicate that they are the cotton pads.

 
Just letting you know, I tried Rockwool (not fiberglass) as a sub-layer, and cotton on top.  Then I tried cotton only.  The cotton only made a big difference.  Sometimes minute changes make huge differences.  Its something to think about.  That's why I would be a tad bit skeptical if you compared that particular mod to the BMF V8 and they were nearly identical.
 
Whats your current set up now?  Did you follow V8 to the letter?
 
Jun 14, 2012 at 1:55 PM Post #8,598 of 11,346
Quote:
 
Also, keep in mind, there are some variables that can have an effect on the leakage, to include:
 
- Using the Shure 840, or Brainwavz HM5 ear pads will result in a tighter seal on your ears.
 
- Opening the bass vents too far on the ear cups of the T50RP, could also allow more sound leakage.  I personally have mine sealed and I still have an enormous amount of bass with mine.

 


Thanks. I haven't decided which mods I will try to accomplish, but those are also good to note.
 
Jun 14, 2012 at 2:15 PM Post #8,599 of 11,346
after trying grodan for the past two weeks, i finally removed it ... i could not achieve the appropriate balance with the types of lenscleaning microfiber at my disposal (ymmv) - way too bright for my tastes.  three days later i am still cleaning out the miniscule detritus that is left behind. if you decide to go this route, know this ... it is a bitch to clean up afterwards as continued use generates more & more micro-particles which proliferate the interior of the cups.  using xx (cheesecloth, etc) to help contain the fibers is certainly a good idea.
 
 
Jun 14, 2012 at 4:56 PM Post #8,600 of 11,346
Quote:
Just letting you know, I tried Rockwool (not fiberglass) as a sub-layer, and cotton on top.  Then I tried cotton only.  The cotton only made a big difference.  Sometimes minute changes make huge differences.  Its something to think about.  That's why I would be a tad bit skeptical if you compared that particular mod to the BMF V8 and they were nearly identical.
 
Whats your current set up now?  Did you follow V8 to the letter?

 
Thanks for sharing your experiences with the wool.  It seems like it might be a futile effort to move ahead with an hour of time or so to try it on my end, only to come to the same conclusion as you have.  Plus, the mess as described in one of the other recent posts, has me thinking a bit about that avenue.
 
I didn't follow the V8 with all of the points.  I did some variation with placement of my Dynamat (on the ear side of the baffles) and then covered it with craft felt with an adhesive back and the driver area cut-out. 
 
I do need to open my cups, though, so I can get out the multi-meter to determine my "L" and "R" ground wires for the Mogami cable that I installed.  I'm going to convert it over to a balanced cable with a 4-pin XLR connector.  This will allow me to drive the Fostex 'phone using some speaker taps as opposed to the headphone stage of the amplifier to see if the speaker outputs yield any additional sound improvements.
 
Jun 14, 2012 at 5:15 PM Post #8,601 of 11,346
Quote:
Wanna kill backwaves?
 
I've been reading the master handbook of acoustics, and trying all kinds of things, and the most effective way to diffuse irritating bass and midband distortion might be to make circular or half circular diffusors of plasticine. Just simply add the plasticine sausages in the bottom of the cup, and add mineralwool on top. You'd be surprised of the effect. I'm not yet sure If the highs are absorbed by such small amount of mineralwool, but the plasticine sausages had an HUGE effect on the irritating midband shout. If this positive effect is due to decreased cup volume (possible change in reverberations?) or by diffusion, reamins to be proved. I'm going to test this with my bigger cups containing a ****load of helmholz resonators and one inch of mineral wool.
 
Cheers. Pictures later.
 


Half circular diffusors need lots of space around them to work properly, search for Volkmann on Policyndrical Diffusers, its all explained there. They may scatter the wave somewhat but I guess simple wool or material damping would yield more effects in a headphone enclosure.
 
Helmholtz resonators will be useless, headphones work slightly different than speakers, or maybe in other words, they work on differet air cavities. I can't see how you are going to stuff such a resonator into a headphone (bass absorbing resonator needs many liters of volume to work), not mentioning how do you know which frequencies you should cut.
 
Have fun :wink:
 
Jun 14, 2012 at 7:05 PM Post #8,602 of 11,346
Quote:
 
Thanks for sharing your experiences with the wool.  It seems like it might be a futile effort to move ahead with an hour of time or so to try it on my end, only to come to the same conclusion as you have.  Plus, the mess as described in one of the other recent posts, has me thinking a bit about that avenue.

 
Yeah maybe, but I'll leave that up to you.  I've tried a few different cup fillings, and I always come crawling back to cotton!
 
Sorry if my last post was offensive.  Going back and reading it, it sounds a big aggressive.  I didn't mean to type it that way.
 
Jun 14, 2012 at 8:00 PM Post #8,603 of 11,346
Quote:
after trying grodan for the past two weeks, i finally removed it ... i could not achieve the appropriate balance with the types of lenscleaning microfiber at my disposal (ymmv) - way too bright for my tastes.  three days later i am still cleaning out the miniscule detritus that is left behind. if you decide to go this route, know this ... it is a bitch to clean up afterwards as continued use generates more & more micro-particles which proliferate the interior of the cups.  using xx (cheesecloth, etc) to help contain the fibers is certainly a good idea.
 

Maybe try a vacuum cleaner?  Masking tape as a "rock wool lint" remover??
 
Jun 14, 2012 at 8:03 PM Post #8,604 of 11,346
Quote:
Half circular diffusors need lots of space around them to work properly, search for Volkmann on Policyndrical Diffusers, its all explained there. They may scatter the wave somewhat but I guess simple wool or material damping would yield more effects in a headphone enclosure.
 
Helmholtz resonators will be useless, headphones work slightly different than speakers, or maybe in other words, they work on differet air cavities. I can't see how you are going to stuff such a resonator into a headphone (bass absorbing resonator needs many liters of volume to work), not mentioning how do you know which frequencies you should cut.
 
Have fun :wink:


How come I hear such an huge difference between original and modded? The original rings like a bell when compared. The larger cups with 1 inch of mineral wool have irritating 600 hz. Might be the reduction of cup volume though.... and perhaps shorter reverberation time? I dont understand this...
 
Jun 14, 2012 at 8:50 PM Post #8,605 of 11,346
Hi guys, I'm sorry I haven't read the whole thread but I got a simple question regarding pads.
 
Is it worth using Stax O2 Pads for the T50RP? How do they sound with it based on your (you guys) experience?
Are the SRH 840/HM5 pads comfortable? I live in a warm place so leather/pleather pads tend to get hot quickly.
 
I think Steelseries Siberia V2 pads fit as well. and they got small holes. I used it on my HE5LE before and the treble got tamed down and bass response became a bit meatier ( HE5LE is too bright for me)
 
Thanks for any answers!
 
Jun 14, 2012 at 8:58 PM Post #8,606 of 11,346
I haven't been mod'ing much lately, but it looks like I need to get back at it.
 
On rock wool and the ODAC
I've been using rock wool to fill my cups for about a month and have been enjoying my T50s immensely. That is until I got my ODAC about a week ago. Now my setup sounds decidedly bright and even etched and sibilant at times. I've removed the microfiber from behind the white paper on the driver and replaced it with Creatology stiff felt a la BMF 8.1. Better, but still no joy. So I'll likely be moving away from rock wool and try cotton again.
 
I did check behind the rock wool and didn't find many stray fibers on the Paxmate or AcoustiPack (see photo) but what fibers were there were easily mopped up with masking tape, as BMF suggested. So if you do experiment with rock wool, I'd caution against "overstuffing" like we commonly do with cotton. Cut-to-fit and I don't think you'll have much cause for concern. 
 

 
On channel fade
Has anyone who's recabled there T50s had this problem? My left channel fades out and dies periodically. No crackle, static or pops. Letting them "rest" unplugged has helped, but the problem is getting worse. The soldered joints look good, but I'll rework them, unless someone has other suggestions on the source of the problem.
 
On sealing 840 pads
Awhile back, someone posted on getting a good seal with the 840 pads. I hadn't really managed to get a great seal until I got the 003 pads. And then I could finally appreciate the bass I'd been missing. But I've gone back and revisited the 840 pads. I find that by stuffing some shim under the pads (in the gap between the pad and the baffle), just at the point where my jaw meets my neck, I get a good seal and better bass. 
 
Jun 14, 2012 at 9:14 PM Post #8,607 of 11,346
After a half-dozen or twenty mod cycles, the pad flaps (insert your particular pads HERE) stretch and begin to lose seal around the cups. Similarly, multiple openings and closings of the baffles to cups stress the 4 cup threads preventing a tight seal, there. I have been applying masking tape around the cup-to-baffle rims with each mod cycle to insure a consistent seal. This serves a dual purpose --> the masking tape also takes up a bit of space, like micmacmo's shims, and provides friction to hold the stretched pad flaps in place.
 
Quote:
I haven't been mod'ing much lately, but it looks like I need to get back at it.
 
On rock wool and the ODAC
I've been using rock wool to fill my cups for about a month and have been enjoying my T50s immensely. That is until I got my ODAC about a week ago. Now my setup sounds decidedly bright and even etched and sibilant at times. I've removed the microfiber from behind the white paper on the driver and replaced it with Creatology stiff felt a la BMF 8.1. Better, but still no joy. So I'll likely be moving away from rock wool and try cotton again.
 
I did check behind the rock wool and didn't find many stray fibers on the Paxmate or AcoustiPack (see photo) but what fibers were there were easily mopped up with masking tape, as BMF suggested. So if you do experiment with rock wool, I'd caution against "overstuffing" like we commonly do with cotton. Cut-to-fit and I don't think you'll have much cause for concern. 
 

 
On channel fade
Has anyone who's recabled there T50s had this problem? My left channel fades out and dies periodically. No crackle, static or pops. Letting them "rest" unplugged has helped, but the problem is getting worse. The soldered joints look good, but I'll rework them, unless someone has other suggestions on the source of the problem.
 
On sealing 840 pads
Awhile back, someone posted on getting a good seal with the 840 pads. I hadn't really managed to get a great seal until I got the 003 pads. And then I could finally appreciate the bass I'd been missing. But I've gone back and revisited the 840 pads. I find that by stuffing some shim under the pads (in the gap between the pad and the baffle), just at the point where my jaw meets my neck, I get a good seal and better bass. 

 
Jun 14, 2012 at 10:09 PM Post #8,608 of 11,346
Quote:
 
 
On channel fade
Has anyone who's recabled there T50s had this problem? My left channel fades out and dies periodically. No crackle, static or pops. Letting them "rest" unplugged has helped, but the problem is getting worse. The soldered joints look good, but I'll rework them, unless someone has other suggestions on the source of the problem.
 
 

 
I recabled mine, but I fed new cable ends into each cup and removed the wire that crossed through the headband.  I did keep about 1.5" of the standard wire attached to the driver and soldered my new wires to those leads.  Hopefully, you didn't de-solder the leads off of the soldering pads and install new wires that those connection points.  If so, it can be tricky to get resolved as apparently, Fostex used aluminum solder to hold the wires to the pads.  If you did end up doing that approach, use a bit of the brown paint to fix rear window defoggers by buying a kit for $10.00 or so at the auto parts store.  It is made by Permatex and will make a solid connection.
 
If you didn't desolder the original wires, it seems odd that you're experiencing the issues you are.   If that's the case, you might want to make an appropriate "Y" cable and remove the single cable that enters only one cup all together.
 
Jun 14, 2012 at 11:38 PM Post #8,609 of 11,346
Well I opened up my T50RP's again and the white wire attached to the driver came off and I don't own a solder.
I was going to ask if anyone knew how to remove sound deadener and that really sticky blue tack stuff but that doesn't seem to matter at the moment any more..
 
Jun 15, 2012 at 1:00 AM Post #8,610 of 11,346
Quote:
Well I opened up my T50RP's again and the white wire attached to the driver came off and I don't own a solder.
I was going to ask if anyone knew how to remove sound deadener and that really sticky blue tack stuff but that doesn't seem to matter at the moment any more..


Read wje's post right above you. Couldn't be harder to find your fix!
 

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