[SunRay95]

The comparisons made are subjective to myself and my ears and may not be the same for you.
You have been warned

 
A couple of years or so back i was on the hunt for some can's and ended up buying a pair of Doc's (Goldring DR150), when i got them i was really happy with them, I however enevitably came across the mod threads on Head-Fi and immediately decided on a recable with good results tighter bass and slightly more forward mids. This sucess caused me to carry on modding (Holes in the back of the driver, deadining the cups, blue tak, etc...), however on the Doc's there is a sort black paper covering most of the driver so i decided to rip it out and the foam infront of it with it,  after all of this came out i plugged them in and shock horror they were terrible reduced bass, the mids had done a runner and the treble was ear splitting.

 
For a couple of months i EQ'd the sound to a listenable level i however was still kicking myself for ruining my can's.
Yesterday however one of the cables split causing intermittent sound, so out came the soldering iron

and as i soldered away i noticed that the material that covers the holes at the back of the driver was the same material that i ripped out the front ruining my headphones.
I then had an epiphany the material had a remarkable resemblence to coffee filters so off to the shop i went and bought a pack of 40.
 
I got home and remade the filter that i had ripped out prior stuck them infront of the driver.
The Results:
Close but no cigar
Bass- is back but boomy
 
Mids- are back
 
Treble-muddy
 
So i started pondering and i remembered reading a post (cant remember the thread) where someone wrote that on a dynamic driver the treble originates from the edges, mids further in and bass from the center so i made a new set of filters with holes in the center around 50% bigger than before, reglued them then plugged them in.
 
The Results:
WOW!!!!!

Bass Tighter and slightly less pronounced
 
Mids More pronounced and detailed
 
Treble is back and now had a great sparkle to it
 
 
It seems the fellow headfier was right the larger the hole in the center of the filter (further out on the driver)  the more treble there is and going smaller results more bass.
 
Theoretically then this mod could be used to tune your drivers to produce the sound you desire. also its cheap and easy to remove if you want, and different shapes and sizes can be used if your feeling curious
 
I would be very interested if this has been done before and other peoples thoughts on this mod.
 
Any additional info or pictures can be added upon request

 

[SunRay95]

I beleive the term is "BUMP"

 

[nick n]

yes if you get around to it i think pics would be great!

 

[obobskivich]

This is identical in concept (but somewhat different in practice) to the Sony Acoustic Bass Lens concept, and the less marketed "filter paper" designs from Kenwood and AKG for their headphones as well. You might also look up the Germania Mod for the Audio-Technica ESW9 for more ideas (I am not responsible if you turn your cans into bass machines and give yourself a headache).

I will say I've never seen or thought to use coffee filters to this end, and my hat is off to you for using something that's so cheaply available. I certainly like the "tune to preference" freedom that allows you (even if you were wasteful and used one coffee filter per cup, you'd have 20 different attempts from the package you got - and I'm thinking about the package of 500 that I have sitting in the kitchen right now...:veryevil.

You may also want to experiment with material of different density and composition - Sony uses something similar to felt (but, knowing Sony, it's probably not "felt" it's probably "ultra fine nanopolymer composite space age aerospace grade acoustic treatment fabric" or something like that), AKG uses foam, but I believe the Kenwood design is pulp product along the same lines as filter paper. An easy place to find a foam disc to try this out with is the little "holder" that comes with CD/DVD cake boxes (I'd get two; I don't want to imagine rough cutting that thing - not responsible if you slash your hand/face off trying it).

 

[SunRay95]

Massive Appologies for the late response i've been very busy lately

Quote:

yes if you get around to it i think pics would be great!

 
Well here is some quick pics that i took tonight

Here are the three different sized filters i tried all cut out of coffee filters just with varying inner diameter size.
Effects on sound as per filter.
Small inner diameter - A very large bass bloat (I Didn't think the docs could chuck out this much bass) large in quantity but low in quality, mids very coloured by the bass and quite recessed, treble very recessed to my ears and hardly any zing.
 
Medium Inner diameter - Reduced bass quantity but much much more quality more detailed but still not quite to my liking, mids brought forward but still recessed good detail though, Treble brought forward but still lacking that zing
 
Large inner diameter - Bass reduced further (only slightly) but a hell of a lot more control and detail, mids againg slightly more forward and detailed, treble brilliant!!! the zing is back, the detail is there and there is less sibilance than they had when stock

 
Heres a shot of the large inner diameter filters on the Doc's

 
I have also experimented with the filters the opposite way round,so a circular button of filter stuck covering the cone of the driver and the rest of the driver exposed this has the effect of reducing the bass and bringing out the highs, however on the goldring doing this pushes them to be vey sibilant but other cans may respond well?????
 
I have only experimented with circular filters so other results could be obtained using different shapes such as ovals and stars! i have however found the perfect filter for me so i dont think i will need to be changing them any time soon

Quote:

I'm thinking about the package of 500 that I have sitting in the kitchen right now...

).
 

Give it a try you only have to take'em out again if you dont like the sound

And with 500 on tap you have plenty of possibilites for experimentation!!

 
Quote:

You may also want to experiment with material of different density and composition - Sony uses something similar to felt (but, knowing Sony, it's probably not "felt" it's probably "ultra fine nanopolymer composite space age aerospace grade acoustic treatment fabric" or something like that), AKG uses foam, but I believe the Kenwood design is pulp product along the same lines as filter paper.

 
I did try some 3mm self adhesive felt and it was damn hard to cut

however the results were not a pleasing as the coffee filters as the bass quantitly dropped dramatically and as i listen mainly to Rock music it was a no go for me. Also note that goldring originally used a pulp filter anyway so it is quite possibly Goldring knows best for their cans and a pulp filter was always going to better for the dr150s
 
Any more info wanted just ask and i will try my best