Just listened to some Fostex T50RPs today... WOW! - Page 630

Full Compass just increased the price for T20/40/50RP parts. Connector B is now Double the price from less than one week ago at $9.69 Each! The super glue fix I posted a few days looks a lot more attractive, now.

Current setup:

 

Baffle flush filled with plasticine

Acoustic foam and felt in cups (no pyramids yet)

J$ Beyerdynamic pads

Stiff felt transpore taped to back of driver with large holes (normal hole punch)

Baffle ports are temporarily sealed with hot glue

Roughly half an inch of Rite Aid rolled cotton

 

I was silly and did two mods at once so I cannot tell which one changed my sound.  I switched from unrolled cotton balls to the Rite Aid cotton and sealed the baffle ports with hot glue.  I didn't notice too much of a difference in treble (maybe slightly smoother), but my bass volume dropped noticeably.  I think the cotton I used was roughly equivalent to what I had in there, and sealing the ports was supposed to increase bass.  Regardless, I want to understand how bass works a little better.  I have been trying mods because others have said the do X or Y and to a point, that has been fine.  But does anyone have resources about enclosure acoustics that I could read up on?  Later down the road, custom cups are something I'd like to attempt, but I need to understand more.  Maybe just a better summary of why each mod does what it does (not just increase or decrease treble, but why it does that, ie what do the pyramids do?)

 

Anyone have any favorite resources that can share?  Thanks guys, this is really fun.

FraGGleR, I've been experimenting with a mod that's very similar to yours. The biggest difference is that I don't have any stuffing (no cotton, rock wool, fiberglass, etc.) in the cups and I've replaced the transpore-and-felt driver cover with a couple of layers of microfiber cloth. The bass is very good while the mids remain lush and lovely.  It would be great if you could try something similar and see if you get similar results. (Getting adequate bass has been a challenge for me.)

 

I've tried a couple of different types of microfiber in a few different configurations, all with some degree of success. My current configuration: I used a piece of smooth lens cleaning cloth laid directly on top of the white driver paper and held in place with two-sided tape around the periphery of the driver grid. On top of this, I placed a swatch of plush dusting cloth. This is elevated a bit above the smooth lens cleaner by some thick two-sided tape (it resembles foam weather stripping with adhesive on both sides) around the periphery of the driver grid and over the lattice around the center square of the grid, such that none of the driver opening is obscured by tape. I'm not sure if this elevation is important. I did it because I had the thick tape handy.

 

I don't think there's anything magical about microfiber, aside from the fact that it has a dense weave that impedes airflow and reflects some treble back towards the ear. I haven't tried, but perhaps a complete layer of transpore (not a 2x2 cm^2 square) on top of felt would produce similar results?

As for why I've eliminated the cup stuffing, have a look at the first post in Bluemonkeyflyer's incremental mods and measurements thread. In particular, look at the waterfall curves and/or spectrographs and you'll notice that regardless of whether there's stuffing in the cups or not, the sound has dissipated by 200 ms. There isn't any evident ringing produced by the cup. So I've been experimenting to see if I could get away without any stuffing, since I've always assumed that the role of the stuffing was to absorb any reflected sounds. 

Edited by micmacmo - 10/25/12 at 2:15pm

I don't have a layer of acoustic foam nor felt in my cups, not any stuffing/fillers either and the sounds are dissipated by 200ms also.
In fact I redirected some reflections towards the ear. I do have a double layer of soft stuff over the drivers.
They're just nowhere near flat response lol.

kalbee did you try gradually sealing off each bass vent slot to see how close to neutral you could get it by slowly dropping the bass slightly? Not that it matters just an easy thing to toy with from the outside, all that matters is your enjoyment of them!

I did on my previous mod segment, I even posted the effects of # of slots sealed vs FR response.
Not on the current mod segment though.
Currently the 120Hz~1120Hz segment is +5dB above all else. If I can flatten that then the rest is somewhat between a bumpy 3dB variance until 4.5kHz.


I'll try it out.
On the other hand, the vents seem to play most of their role on 400Hz and below (decreasing w/ seal) and 400Hz~600Hz (increasing w/ seal), with increasing effect as you leave the 350Hz~400Hz point. Might not come with very big success for my situation :P
Edited by kalbee - 10/25/12 at 6:14pm

Hey, Kalbee, your results sound similar to mine. But I can't say I'm dissatisfied with them. In fact, I quite enjoy them. 

Config:

• AcoustiPack Lite and adhesive felt on the cup floors.
• Stock cup ports
• A layer each of flat and plush microfiber on the driver (as described in my previous post)
• Tungsten putty flush-loaded in the baffle
• Plugged baffle ports
• 840 pads

 

Blue is the left channel. Red is the right channel.

 

I don't dislike them, in fact I enjoy them very much!
I only mentioned that they're nowhere near flat response because that seems to be all that the new modders are interested in.

The graphs are not with me right now but this is essentially my setup right now:

Except the hockey tape is now replaced with two layers of arctic cotton (courtesy you know who!).
This is still part of my dirt-cheap mod series.

I pat myself on the back for having some of the weirdest or unconventional mods lol. Remember the wood diffuser attempt? I prepared enough for a take 2 but never got to do it.

Kalbee, that's incredible! What all do you have in there? It reminds me of Bits & Bites!

Plasticine in the baffle.
In the cups are:
-wood trimming (red oak? there's quite a selection. glue backed, so you can use a iron to stick them to furniture sides) - like $1.50 for a roll big enough for maybe 30 pairs.
-cotton (behind the wood trimming, acts as whatever trap)
-Two small piece of plasticine to somewhat hold the wood trimming at an angle.
-3 quarters of earplugs
-4 full earplugs.

The earplugs were the cheapest ones on ebay... like $2 for 30 pairs or something.
The wood trimming is actually positioned to reflect sound towards the ear, so the left cup has to have it facing the other side.
Positioning with things like that or partial damping (i.e. damping layer with a hole on a designated side) actually has some nice effects if not just a bit of a pain to figure out what side gives the best results, where to cut it, etc.

In another headphone I have a setup like this

(random picture of ear from google) the crescent-like shape being the cutout section of the damping layer.

Have fun trying things out


**EDIT**
Just to clarify, while I did mention the cotton behind the wood trimming was to serve as whatever trap, note that the cotton was essentially used as alternative to surface mount foam (or ear plugs in this case), and the main use of that section is still the wood trimming as reflector. You can ignore the mention of cotton if you wish.
Edited by kalbee - 10/25/12 at 10:13pm

I love the ingenuity and kitchen-sink approach. But do you find it's hard to balance the left and right cups, given all the variables you have going on? (In part, my minimalist approach is driven by my laziness and general inability to refine and match the sound in both cups.)

 

And keep us posted! 

Yeah, it's difficult since the left cup has that 3.5mm jack but I generally only mod to the right ear (with these kinds of mod you can't wear the 'phones backwards with proper success). If I hear something notable differences on the left in mono then I make changes otherwise my L/R balance is fueled by the same as your minimalism

I removed the cotton entirely from my mod and the sound is much more in line with what I like.  Bass is back, mids are strong, and I still have better treble than stock due to the felt and transpore (added a small reflector of transpore).  

Did you notice any echo, ringing or hollowness to the sound? 

I don't think so.  To be honest, I don't know if I have ears trained well enough to identify that.  I still have acoustic foam and felt in the cup.