Just listened to some Fostex T50RPs today... WOW!

Kneadable eraser that I'm familiar with isn't sticky. You want something that doesn't require gluing.

Oh, it sticks in the crevasses just fine, wont fall out or anything.

Received T50RPs today from B&H and just finished the modification. I did not have the Blu-Tack but found the Scotch Adhesive Putty. It seems Scotch also works. Now I am enjoying music with T50RPs.
 
@joelpearce and leeperry
Thanks for your pictures and suggestions. Really helped me a lot.
 
 

Thanks for the link sp. The way the Aussie $ is climbing against the US peso this are looking like a better buy as each day passes. I am going to get a pair as they seem like a real bargain in the often over the top world of hi fi. I can't resist such value should be interesting to compare them to my stax lambda pro.

Took me a few hours but I finally finished modding them!
 
Running now from a Pioneer CLD-98 to a Parasound DAC 1000 via coax and to a Marantz 1250 bookshelf amp to the T50RPs . I'm actually not sure if I should use the DAC at all or just run strait analog from the CLD to the amp... but anyways, the way it sounds right now is pretty nice, a bit lacking on the lower end, but still pretty a decent jump in SQ from my AD700s and my XB700s

Forgot to mention this but I'm currently using my AD700 earpads with them, although this make SQ worse by quite a bit, it truly does increase comfort by a hundred thousand fold!

Yeah, open and closed headphones have VERY different pads.  With that much soft material, you are going to lose too much bass to really make them listenable.  If there are holes on the bottom of the pads, you might be able to improve sound quality by putting electrical tape over the holes.

 

sopp said:

 

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you'd prolly want to use a screwdriver or so to make the blutack non -flat, like this: http://assets.head-fi.org/a/ac/ac549593_baffleinside.jpg
 
BTW, the blutack I used is 100% synthetical rubber and seems to get harder with time.

I have been thinking around this baffle mod, and can't really understand the underlying asumption. I have a hard time believing micro resonances in the baffle could affect the performance of the driver, especially since Fostex do claim they use a specific and innovative plastic material to reduce those resonances. The "nerves" you can see on the baffle and cups should be enough to prevent inner vibrations.
 
Actually, I have the feeling that the major part of the resonances in the T50RP cups are rather due to bass frequencies backwaves, emitted by the back of the dipole drivers and sent back forward in mutliple directions after hitting the bottom of the cups. That seem to create cancelation or blurring of the original soundstage mostly. That is at least my impression.
 
I have not modded the baffle, and really can't complain at all by the end result. Soundstage is much more convincing, and imaging has improved dramatically. I do not play with stock vents and felts, because I feel the original frequency response is just spot on for my taste and ears. YMMV.
 
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leeperry said:

you'd prolly want to use a screwdriver or so to make the blutack non -flat, like this: http://assets.head-fi.org/a/ac/ac549593_baffleinside.jpg

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I am speechless with the T50s.  I have performed the mods and the results are astounding...they now play with the big boys, especially considering the T1s which cost way more than the 1K mark.  Comparisons to the T1s is inevitable as both these cans are not true open back designs.  My T50s sound better to me with a more natural bass balance with greater impact that goes lower.  The T50s extend further up the treble whereas the T1 has a rollof and is somewhat dark in the treble, the T50 does not have a treble heavy reponse.  The headstage of the T50 is greater in width and separation is superior, detail retrieval is on par.  I definitely prefer the modded T50.
 
After taking off the baffles nearly a dozen times I have ended up with the following:
 
The baffles were first filled in.  This first mod reduced resonance significantly.  I used a roll of cheap jaycar sound absorption material that is backed with foil...I thought it was just heaps of blutack, but when I got it home...the blutack did not peel away from the foil...so I had to painstakingly remove bits of blutack...the roll was cheap at 13 bucks and there is enough blutack within for a lifetimes supply.
 
I still heard cup resonance, so I opened them up again and cut up strips of this blutack lined with foil and layered the cups...the theory was to increase the mass and rigidity of the cups to prevent vibration...I could not peel the aluminium foil off so it remained as a potential reflection point for the sound waves.  The results were excellent and cup resonance and vibration was no longer an issue.  However the sound was bright...it reminded me exactly of the HD800 upper mid and treble response albeit with more bass and midrange body...I could not leave it at that as I knew the trreble would eventually fatigue me...many will like this tonal balalnce. 
 
With cup resonance no longer inhibiting the T50s, the detail retrieval and separation moved up two notches.  Before opening up the baffles again, I blocked the cup vents with masking tape from the exterior.  This resulted in in a reduction of bass...the sound reminded me of the HD800 in tonal balance...albeit without the the superior HD800 soundstage and imaging.  This gave me the idea to remove the vent lining from inside the cups, as I now suspected that the vent was actually a bass port.
 
I opened them up again, removed the felt lining on the bass vents and proceeded to stuff the cups with pillow fluff...I theorised that the foil backing on the bluetack within the cups  were acting as a reflection surface for treble energy and filling the cup would further dissipate any bouncing soundwaves and further reduce resonance.  I stuffed the cups with the bass vent uncovered...I theorised that the stuffing would serve a similar purpose to the vent felt but with less blockage.  This should be necessary as all the bluetack combined and the pillow fluff would be reducing the overall volume of the cup...freeing the vent a little would let the drivers experience a similar level of back pressure as with the unmodded cup volume.
 
The results were good...bass came up some more...but this time the treble was too muffled and the net result was an improve bass reponse and headstage due to freeing of the bass vent...but too much pillow fluff killed the treble response.
 
The next few times I opened up the cups was to fine tune the treble solely via how much pillow fluff I stuffed in the cups.  No fluff had maximum treble reponse...the more fluff I introduced the more treble reponse was dampened...the fluff was the treble EQ and I imagine blocking off the bass vent to certain degrees acted like a bass EQ...I left them open with only a very moderate amount of fluff in the cups and therefore the bass vent would have been close to maximum bass potential.
 
I have since been just enjoying music with my modded T50s and feeling good about myself for being able to tune these cans to a state where I preferred my T50s over both HD800 and T1.  The resultant tonal balance when compared to stock was improved bass reponse and articulation with greater impact and subbass extension.  The treble is probably boosted over stock by between 1 to 3 db... with improved presence and extension due to greater clarity without cup resonance.  Overall they still sound like the stock T50 but better in everyway conceivable.  I could have tuned them to sound almost excatly like the HD800 or SE530 IEM in terms of sound signature...the possibilities are nearly endless.
 
I want to purchase a second pair of T50s and cut open the cups to create a true open back T50...as well I want to drill holes in the baffle so "crossfeed" can be implemented to challenge true open back and open baffle designs like HD800, HD650, K701, K1000 etc.  I have learnt a crapload about headphone acoustics from this experience...my gratitude for the efforts of of the entire "Ortho Ninja" team.  Joelpearce deserves a mention as his findings did guide my theories and experimentation...sound advice in more ways than one.
 

SP Wild, thanks for posting your results. I haven't dug into my T50RPs yet. I was thinking that instead of pillow fluff, maybe putting som felt over the damping material (in my case Dynamat) that I was going to put in the back of the cups. 

 

shamu144 said:

I have been thinking around this baffle mod, and can't really understand the underlying asumption.

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Put simply, you're missing out on not spending 10 mins to fill every hole of the two baffles w/ blutack. It's not about resonances per se, it's abous mass dampening and vibrations. The sound will be far more focused. You can always undo it if you don't like it. No harm done! I've sometimes spent a lot of time doing/undoing mods on this phone... 
 

Originally Posted by SP Wild /img/forum/go_quote.gif
 
Joelpearce deserves a mention as his findings did guide my theories and experimentation

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He's got me curious about making the driver's back naked, but being an irreversible mod I think I'll leave it at that. A while ago, someone advised me to remove the front grill off my DT770/600 drivers to get more focused trebles...but then the diaphragms would have only been protected by the thin foam disc that's before the drivers. One hair and they'd be compromised. Anyway, yes...they sound amazing as is

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roscoeiii said:

SP Wild, thanks for posting your results. I haven't dug into my T50RPs yet. I was thinking that instead of pillow fluff, maybe putting som felt over the damping material (in my case Dynamat) that I was going to put in the back of the cups. 

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I only used pillow fluff because my pillow was looking straight at me when I wondered about a fibrous damping compound...if I had dynamat I would have used that also.
 
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leeperry said:

 
 

He's got me curious about making the driver's back naked, but being an irreversible mod I think I'll live it at that. A while ago, someone advised me to remove the front grill off my DT770/600 drivers to get more focused trebles...but then the diaphragms would have only been protected by the thin foam disc that's before the drivers. One hair and they'd be compromised. Anyway, yes...they sound amazing as is

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Do you mean the mod removing the black cloth covering the front of the drivers?  I didn't do this one because I have no intentions of making this phone look modded...I want it to look stock...also I quite like how it sounds...this mod would probably increase treble response and slightly improve transient response as I'd imagine the material would blunt it a touch.  However with superfast drivers it is possible for transient to be quicker than reality...because in real life soundwaves have much further distances to travel and the atmosphere serves to blunt some of the transients naturally.  I had this phenomena with the LCD2...at low volumes transients are sharper than reality...at higher volumes as the drivers are asked to move further and inertia is increased...transients slow a touch...and matches to reality very closely at real sound pressure levels.
 
Of course I will not go any further with this T50 and I await your pioneering results with your most ambitious attempts to modify the T50s in new directions...at the moment I do suspect the stock headband is bottlenecking the vibration damping potential...I feel the headband is an integral part of chassis torsional rigidity.  My T50s feel so much solid and heftier than stock...the weight is the only telltale to the modifications...and when you look at the vents you can see white fluff against the cup...but it look factory engineered...this was a prerequisite with the mods for this particular T50.  The hype is real and true!
 

hehe, yeah...the R10 cups are full of cushion stuffing too, I'll have to give it a shot someday.
 
no I meant the piece of white "paper" that's stuck at the back of the driver...I wonder what happens when it's gone
 
I did remove the felt before the drivers, it was sounding ugly...I'm using a thicker felt that sounds better to my ears, and that also improves the isolation...very happy w/ that
 
I've changed my xfeed settings, I'll play around w/ the lambskin headband again...but I don't see it working.

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sp wild said:

I have learnt a crapload about headphone acoustics from this experience...my gratitude for the efforts of of the entire "Ortho Ninja" team.  Joelpearce deserves a mention as his findings did guide my theories and experimentation...sound advice in more ways than one.
 
 

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I'm glad it helped.
 
I've really been operating kind of blind, myself.  I've read some stuff in the ortho thread (those guys really know what they're talking about), but since I'm planning to put mine into a Thunderpants enclosure, I figured I've really got nothing to lose--I've been into my T50RP at least a dozen times, playing around with different materials to see what would happen with different materials loaded up in different ways.  I know virtually nothing about sound science.
 
I still have a lot to learn, but it's definitely been educational so far.  This is the great benefit of orthos.  It's possible to use different materials and damping to essentially tune and equalize a pair of headphones to personal taste.