Just listened to some Fostex T50RPs today... WOW! - Page 636

Keith is the man with the plan.  What ever version I have - I love.  Simple as that..

Quote:

Originally Posted by micmacmo 

I don't think the GM status of the plant determines the quality or consistency of the fiber. I think it has more to do with the processing of the bolls. 

what i was trying to express is that 'natural' as used in the original nomenclature would might give rise to legal issues if gm material were used instead.  i am surmising that since they cannot guarantee gm-free source at a viable cost, they have dropped that particular product.  as for differences in the products, i am in agreement (likely to be different oems).

while it appears that every manufactured cotton product in our stores comes from china these days, u.s.a. remains the #1 exporter of raw cotton & india the #1 producer of gm cotton (by area).

This is my current configuration:

Earside felt removed, fatmat + paxmate baffle, shure 840 pad + cotton, baffle port sealed, bass vent sealed except 3mm

Mass load baffle, stock white felt under some type of felt that i can find

This is the clay i use, dont' know if it's good enough, that's the simple clay that the kid using around

Paxmate cup floor with some cardboard

Cotton stuff inside the cup.

This config have quite good mid, treble and soundstage for a closed can but it doesn't go very low in bass section, using test tone, 30hz is quite weak, 20hz is nearly unaudible and bass impact is weak too. I need some suggestion!

Quote:

Originally Posted by geetarman49 

what i was trying to express is that 'natural' as used in the original nomenclature would might give rise to legal issues if gm material were used instead.  i am surmising that since they cannot guarantee gm-free source at a viable cost, they have dropped that particular product.  as for differences in the products, i am in agreement (likely to be different oems).

 

while it appears that every manufactured cotton product in our stores comes from china these days, u.s.a. remains the #1 exporter of raw cotton & india the #1 producer of gm cotton (by area).

Ah, gotchya. I see what you meant. 

proid, you might try three things:

1. Leave the vent at the back of the cups completely open. (If the bass bloats or overwhelms, you can then tune it to your preference by incrementally closing the vents.)  
2. Remove some of the cotton.
3. Check the felt you're using. It might be causing an over-emphasis in the treble at the expense of the bass. (My current theory is that the porosity of the material is important. The less porous the covering, the more treble that's reflected back towards the ear and the perception of weaker bass. You can test the relative porosity of materials by blowing through them.)

My guess is that the felt isn't the problem, though, unless it's the self adhesive kind. 

Also one can punch several holes through the felt, that will allow bass to leak through.

I agree about the bass vents first.

Basically a process of elimination then adjusting the culprit from there, just as Mo says. SO I really didn't need to say anything then did i

Quote:

Originally Posted by proid 
 

Good advice already from micmacmo, Nevod, and nick n.

Also check to make sure your baffles are sealed at the cup rims. If not, tighten the four screws. If stripped, use the super glue method I posted previously. Temporarily, use masking tape around the rims.

Make sure your pad flaps seal on the cups all the way around. If loose, try to repair, tape around the pad flaps/cups, use something similar to Alene's double-sided tape (see source list at the bottom of Post #1 in this thread for pictures/description), or get new pads.

Remove the cotton from under the pads. Stuffing cotton and other filler materials under the pads may increase sound stage but kills bass, IME.

Good luck

I put quite a lot cotton and make just a tiny bass vent too make bass as tight as possible. If i open more bass vent, i got more bass but all is mid bass, it won't go lower.

Quote:

Originally Posted by proid 

I put quite a lot cotton and make just a tiny bass vent too make bass as tight as possible. If i open more bass vent, i got more bass but all is mid bass, it won't go lower.

Could be too much cotton so maybe try a little less and re-test.  

Self-adhesive felt will not work in this application, as suggested by micmacmo. The felt I use is from Michael's Craft Store. It is "Creatology Stiffened Craft Felt" and it is ~1.5 mm in thickness. If your felt is thicker and/or more dense, you will lose bass. As pointed out by Nevod, I've found that punching holes in the felt of various sizes and number, overlaying the driver grids on the back of the drivers, produces more bass. Start with 2-3 mm diameter holes over the 4 corner grid spaces. Incrementally add more holes over other grid spaces and/or try larger holes in 1 mm increments.

Good luck.

Quote:

Originally Posted by micmacmo 

 

1.  
2.  
3. Check the felt you're using. It might be causing an over-emphasis in the treble at the expense of the bass. (My current theory is that the porosity of the material is important. The less porous the covering, the more treble that's reflected back towards the ear and the perception of weaker bass. You can test the relative porosity of materials by blowing through them.)

Well that's just basic acoustics really. The more porous something is, the more acoustic energy that transmits through (rather than reflected). The energy that passes through is also partially absorbed by the material. The reflective and absorptive coefficients are usually inversely related, but not linearly so.

Quote:

Originally Posted by Armaegis 

 

Well that's just basic acoustics really. 

See. I am learning something from this crazy hobby. : )

I had the pleasure of listening to pwnm30rdi3s T50RPs today which had been in sat in customs for the past week.

The sound is stunning, I was not under the impression a close headphone could have this much soundstage, I might have a peak under the skirt and see if I can re-create it.

Just got my t50rp in. The cable had problems, no surprise there. Some deoxit fixed it (and I have a vmoda cable en route)

The more troubling issue is the rattle of the right side with bass... Should I get a replacement pair? *sigh*

It sounds defective, I'd have it replaced just for peace of mind.