Fostex T50RP Incremental Mods and Measurements

[hans030390]

Just received my T50rp's yesterday, they sound pretty good and I've begun collecting materials for modding.  The one thing I have been unable to find is the paxmate or acoustipack damping material without having to order it from the internet.  I was happy to find the Silverstone Acoustic Foam listed on Fry's website for only $12.95 and don't have to worry about shipping with having a Fry's local to where I live.  So if you have a Fry's and a Michaels in your area you're good to go.

Fry's might also have Dynamat (though marked up a lot), which you could potentially use under the silverstone foam.

 

[tool462]

I have enough Silverstone and acoustipak (2 different densities) and plasticine left over for probably 3 more pairs.  I have some Dynamat Xtreme too, but not a ton of it.
 
If there is anything someone can't find or doesn't want to buy a whole sheet drop me a PM and I can send it out for a few bucks.

 

[ruinevil]

Paper under felt sounds like ass.

 

[tubes]

Well I just finished off my DBV #3 build.  I used fiberglass and cotton instead of rockwool, I wasn't sure if the rockwool is supposed to be kept in a sliced portion sort like a slice of cheese or if it should be pulled apart.  The problem I had with the rockwool was trying to slice 2 pieces equal to one another. I pretty much followed BMF's build instructions to a T,  using the round treble reflector and the recommended amount of FG and Cotton.  When reassembling I had a problem trying to get the baffle screwed back into the ear cup, I think the cotton may have been getting between the shock absorber and the baffle preventing the baffle from lying flat in the ear cup, I'm not sure it's still correct but I was able to screw it together and install the 840 pads.
 
The sound, instead of trying to list all the improvements I think it would be easier to just say everything is better over the stock T50's, a major improvement.  My ears no longer hurt trying to listen for extended periods, which was due to the sound not the comfort.  The one thing I was afraid of was hearing an imbalance from the left to the right side but I couldn't detect any problem. The only thing I may like to change would be the highs, just a tad steely sometimes and this may be due to the Yamaha receiver I'm using for an amp so I'm not going to make any changes until I get a proper amp.
 
I'd like to thank BMF for all his help listing the mods step by step with pictures to put it all together.  I feel a little guilty being able to assemble my build in a matter of hours because of the hard work by BMF and the time he spent testing and making it available for anyone to use.  I tip my hat.  Thanks.
 
Phill

 

[tubes]

A little follow up to my post when I finished my DVB #3 build.  After more listening I grew a little tired of the somewhat steely highs and attenuated bass so I decided to go back in for some exploratory surgery.  I decided to remove the fiberglass probably because it's the nastiest stuff that goes into the build and leave the cotton in.  I also added self adhesive felt around the uncovered vertical areas of the cup that the cotton did not cover, I put the felt flush with or up to the edge of the shelf where the baffle lays into the cup.
 
One change that is noticeable is the quality of the highs, no longer steely and music now sounds whole instead of the steely highs riding on the mids.  Midrange is fuller and more upfront, guitars now have better tone especially higher notes, better/cleaner vocals and bass is also fuller adding a slight bloom to the music.  The only problem now is I detect a slight imbalance between left and right or maybe it's the leakage around the cable jack that I haven't closed up with silicon yet.  Hopefully I'll leave these alone for a while.  I'm not sure how these will measure now but I guess it doesn't matter if the sound is more enjoyable.
 
Phill

 

[bluemonkeyflyer]

Quote:

A little follow up to my post when I finished my DVB #3 build.  After more listening I grew a little tired of the somewhat steely highs and attenuated bass so I decided to go back in for some exploratory surgery.  I decided to remove the fiberglass probably because it's the nastiest stuff that goes into the build and leave the cotton in.  I also added self adhesive felt around the uncovered vertical areas of the cup that the cotton did not cover, I put the felt flush with or up to the edge of the shelf where the baffle lays into the cup.
 
One change that is noticeable is the quality of the highs, no longer steely and music now sounds whole instead of the steely highs riding on the mids.  Midrange is fuller and more upfront, guitars now have better tone especially higher notes, better/cleaner vocals and bass is also fuller adding a slight bloom to the music.  The only problem now is I detect a slight imbalance between left and right or maybe it's the leakage around the cable jack that I haven't closed up with silicon yet.  Hopefully I'll leave these alone for a while.  I'm not sure how these will measure now but I guess it doesn't matter if the sound is more enjoyable.
 
Phill

 
Phill,
 
You're doing what I always suggest: "Take anyone's mod and make it your own" by tweaking and tuning to suit your preferences and audio chain.  Good stuff!

 

[tubes]

I may have under estimated the improvements listed in my last post.  The sound is now electrostatic like, transparent and very refined, they now allow you to hear the beauty of the music which has eluded me from my two channel system which is not shabby and consists of of a tube pre and tube mono amps.  I am pretty much awe struck by what a cheap headphone can be transformed in to, vocals now just hang in the air and massed vocals are thrilling.  Keith, thanks for the leadership you have provided, without it I would have passed over this gem.  
 
Phill

 

[nick n]

Quote:

I may have under estimated the improvements listed in my last post.  The sound is now electrostatic like, transparent and very refined, they now allow you to hear the beauty of the music which has eluded me from my two channel system which is not shabby and consists of of a tube pre and tube mono amps.  I am pretty much awe struck by what a cheap headphone can be transformed in to, vocals now just hang in the air and massed vocals are thrilling.  Keith, thanks for the leadership you have provided, without it I would have passed over this gem.  
 
Phill

do you have closeup pics of the adhseive felt  for approximate density and thickness? How thick is it?
 
Thanks,.

 

[tubes]

The felt is standard adhesive felt from Michaels, it is actually pretty thin.  I hate to open the cans again because of stretching the 840 pads every time they are removed but let me see if I can take some pictures.  If I had it to do all over again I would have added the felt when I installed the acoustipack in the cups before installing the cotton.
 
Phill

 

[tubes]

Sorry I misunderstood about pictures, I'l take some pics of the felt and post them tomorrow.  Maybe BMF can shed some light on the exact thickness.
 
Phill

 

[bluemonkeyflyer]

^ Michael's self-adhesive felt is ~ 1.5 mm thick and stiffened craft felt is closer to 2 mm thick measured with Kobalt digital calipers.

 

[nick n]

ok I have some from there also. They actually sell two thin types pretty similar thicknesses though. Just wondered I have a bunch of brands. Thanks.

 

[hans030390]

BMF, have you tried working with any open-cell acoustic foam like this? It comes is various thicknesses and looks fairly similar to some damping material purrin tried out in one of my modded Monoprice headphones, which he said was just medium density packing foam. Either way, it did a great job! Really smoothed out the treble. Might be worth looking into for the T50RP!

Edit: I forgot to mention that it has an adhesive back. Might be something you'd need to shave off or something...

 

[tubes]

A couple of photos to show where I added self adhesive felt just above the cotton.
 
 

 
 
 

 
 

 

[bluemonkeyflyer]

Quote:

BMF, have you tried working with any open-cell acoustic foam like this? It comes is various thicknesses and looks fairly similar to some damping material purrin tried out in one of my modded Monoprice headphones, which he said was just medium density packing foam. Either way, it did a great job! Really smoothed out the treble. Might be worth looking into for the T50RP!
Edit: I forgot to mention that it has an adhesive back. Might be something you'd need to shave off or something...

 
Yes, I've tried open cell foam just like the one in the link. I could never find a configuration with it by itself and in combination with other materials that works as well as DBV #3.
 
DBV #3 is so easy to build. It requires no modified bass port (leave the internal black cup vent felt in place), no Dynamat (optional), no extra drilled out baffle ports, and delivers amazing SQ, IMO, when properly implemented. I think Rite Aid Natural Absorbent Cotton is the easiest brand to use for consistently superior sound because it has uniformly fine layers. That said, other brands can work, as I've previously posted.
 
Unlike tubes' build, I prefer a 1x6x7 cm rectangle (Compressed, then measured and weighing ~ 1.3 grams) of J&M fiberglass overlaying the cotton (Uncompressed, then measured = ~2x6x7 cm and weighing ~ 2 grams). J&M fiberglass stays together with minimal to no stray fibers, IME, and I believe it brings out more treble details than cotton, alone. This just goes to show that each person must tweak the build to suit their audio chain and personal preferences, which is exactly what 'tubes' did to achieve "electrostatic like, transparent, and very refined" SQ he described after tuning his DBV #3  mod.