i'm working on the headcups right now.
i went to walmart and picked up Viking "genuine leather Chamois", in the auto department. it's a lot smoother than velour and here's what i have done:
1] took a 3" glass.
2] wetted a 7" square piece of the above chamois and put over the 3" glass and pushed in about 1" into the glass, then set a 3" candle glass bottom into that area, filled the candle glass with water, to provide weight as the chamois dries) also am trying an "Olivari" 17 oz. Olive Oil flask, and a Japanese tea ceremony teacup), put a few rubber bands about 2" from the lip of the glass, and SMOOTHED it so that there are no creases from 2" to the topof the glass. i should then be able to cut about 1.20" from the the top of the glass to match the 1" thickness of the sr80's headpads.
if everything goes right, i'll have a pre-formed leather mold. i then intend to spray the bottom of this mold with contact cement and the top of the Grado sr80 headcup, wait a minute an mate them. after drying i will then use a #2 exacto knife to cut the 1.5" hole at the correct 45 degree angle. i should end up with an sr80 headcup except in super smooth leather
if you have seen a few of the Grado modifications here, one entails replacing the sr80 body with one that is about the sr325's demensions. it basically moves the transducer back about .25" and the distance from the transducer to the outer shell about .25". The same can be done with a .25" spacer in front of the headcup and a .25" spacer beyond the transducer shell. without the spacer the sr80 transducer touches your ear. a 2.25" x .25" rubber spacer from Homedepot should do the same thing without all that fuss and bother. and a 2.25" x .25" "extension" should replicate the tube length of the 325's.
as to the outside of the transducer, think "magnaphone". in speaker terms it'd be a laberynth port. if you could take a 12" speaker and extend the cone so that it was 12 FEET away, the sound coming out of that 12' circular hole would be IMMENSE. as this is a 1 and 21/32" hole (with a .675" transducer), to produce a 20 Hz wave, it would have to be x? .... About 1.78" in total length. the sr80 has about a 31/32" body, therefore doubling that to 62/32" or 1 and 30/32 (15/16"), or just under 2" (1.78") should extend the midbass to midrange. [put a toilet paper tube on the outside of the sr80's. cut so that it it 1" thick and overlap]. the sound is completely different. but a pure tube (like the toilet tube) turns the bass into a 'ported' speaker sound. the way to get around this is to increase the surface area as it goes out further from the centre of the transducer. this is known as a radial tube in speaker terms. (think of a flower opening with the headphone/speaker transducer as the centre of the flower).
the "speaker" therefore has no "hump", it has "many" "humps" but all smooth, it extends the bass. this is because the speaker "port" is FLARED.
the same can be done from the oposite end. if the distance from your eardrum to the headphone surface is "x", then the distance from the transducer to the outer part of the headphone should be the same (DOUBLE) |>|<| . think magnaphone. your eardrum is about a "Q-TiP" width, now the length of the Q-Tip to your outer ear, should be the same, or double to the transducer end. the outer area should be a hysterisis loop width.
to really understand what i am saying, listen to "ported" speakers, "acoustic" suspension speakers and "laberynth" speakers. a laberynth speaker is a speaker which has the "magnaphone" twisted/bent so that the length will be able to produce a low frequency which you can feel but not hear. think organ pipe. the differenent pipe lengths are 'tuned' to a certain frequency'. now think of a ram horn or a sea-shell. the different amount of air will produce a different note. this is a flared horn. a trumpet is FLARED. a trombone is FLARED. a Clarinet is FLARED. an oboe is FLARED. the flare end area decides the cut off frequency. what if you want the cut off frequency to be 20 Hz? what will the area have to be? transpose that to your headphones!
i am already thinking of taking hard foam (like the type you stuff flowers into), making the outer end like a sea shell, shellacking it, and cementing it to the sr80's circular hole (the outer is 2 and 1/8" with the inner being 1 and 21/32"), making it the same DEPTH as the body (31/32") but 1/2 greater in width at the end. in other words, a FLARE.
this should increase midrange prescense, give a smooth high end roll off, and a greater bass low end.
yeah, it's gonna look geeky...
just like your ears