seems to be posting time - so i post some information about what i did last year to make custom bowls.
after buying my first grado (SR225i) last year or the year before i tried to improve bass and comfort by making my own bowls to improve the sound without modding the sr225i itself.
after reading a lot of articles here i thought
- that socks are a must
- the tape mod is nice as basis but should be thought to an end
- i was also inspired by tyll hertsens post on innerfidelity about standard grado and modded grado bowls
so i had the idea
- to put something around standard bowls
- to build something to put around the bowls to extend them in size
- to use socks to cover whatever i put around
after a lot of testing and listening here are the results - my custom grado bowl extension set:
it consists of different rings for the extension of the bowls, the sound tuning rings, the i call them "sound tuning chips" (that were inspired by tyll hertsens article on innerfidelity and his measurement and implication of bass response and size, i,e. diameter and circumference of the bowls):
i also tested different socks (very thin, normal, thick), in general the thicker the socks, the more bass, but this is achieved by absorbing the highs and loosing detail, precision and overall sound quality, so as result i only used very thin socks (thin socks size 39-42).
to explain the different parts, here are some samples:
as replacement for the tape mod the sound tuning rings can be used by just putting them around a standard bowl:
left - the first ring is made out of felt 2mm thick - very homogenous sounding, adds some warmth to the sound, so for example slightly more bass, less harsh highs
right - the second ring is made out of two layers of strong tape - improves the bass but as there is no glue between bowl and ring slightly less effective than tape directly glued to the bowl.
This is a bowl i made especially for the SR225i:
the bowl is extended by a bowl extension ring made out of felt 6mm thick, linear shape and 4 sound tuning ships between bowl and extension ring, a sock wrapped around the extension ring:
Extension Ring:
here the extension ring is made out of felt 6mm thick. the thicker the felt here, the more the bass is improved. to make the ring i cutted a piece of fitting length, 5mm higher than the bowl. i then cut a piece of felt starting at the height of the bowl on the inner side of the felt ring so that as result there is a linear shape, the inner side of the extension ring so gets wider with the height.
Shape of the Extension RIng::
- if you just use the felt ring as it is (no shape), the higher the extension ring, the more the bass, bass gets boomy and you start to get bass resonances
- a linear shape, as you see (sorry for my limited english to exactly descibe what i want to say) prevents the bass from getting boomy and resonant, the resulting extended bowl also sounds very grado-like
- i also tried a parabolic shape, this shape of the inner side of the extension ring gives you the best soundstage but more sounding like a standard headphone, not a grado. also the extension ring gets very thin with a parabolic shape, so the socks applied will result in a deformation of the extension ring
Sound tuning chips:
inspired by the article on innerfidelity were tyll hertsens had the idea, that resonance frequencies were related to the diameter and so the circumference of the bowl, i had the idea
- to put small plastic pieces at constant distances, symetrically
- or different distances, not symetrically
- to have areas of different reflection in the grado bowl
- and so different ares of acustic behaviour and absorbtion
- and so killing resonances circulating inside the bowls
and this really works
- the hole sound gets cleaner, the chips especially kill resonances of the higher frequencies, the highs get cleaner, more resonant free and not that harsh but without getting a warmer sound
- due the sound tuning chips also the bass gets cleaner but also the chips very slightly limit the lowest possible bass resonance frequency the bowl can transmit, but together with an bowl extension ring this is absolutely no problem as the effect is very small compared to the bass improvement due to the bowl extension ring.
This is a bowl i made especially for the SR325is:
it consists of a grado bowl, a felt sound tuning ring, 4 sound tuning chips (symetrically), a bowl extension ring 1cm higher than the bowl 8mm thick with parabolic shape, and an i call it "soundstage ring".
in the case of the sr325 the sound tuning ring made out of felt 2mm thick acustically couples the bowl with the extension ring, the felt sound tuning ring here also tunes the sound to the warmer, homogenous side as the sr325is highs are more pronounced than the sr225i (this ring was not nessesary for the sr225i bowl posted before).
i already explained the function of the sound tuning chips, here they are used because of the same reason.
the bwol extension ring here is 8mm thick so that the bass is more improved than with 6mm and also the parabolic shape is more effective.
the "sound stage ring" prevents the extension ring from beeing deformed when you put the socks around, so the ring takes care that the soundstage benefit because of the parabolic shape will not be eliminated by the socks deforming the extension ring.
also the soundstage ring works like an additional "tape mod" ring so further improving bass depth.
in this case i put socks separately around the bowl extension ring and the soundstage ring.
something about wrapping socks around the rings:
i tried a lot of different ways to put the socks around the rings or the hole extended bowl, aslo i tried the original grado bowl with socks (not worth to mention or to listen to), but after all the tests there are only two ways i used the socks:
different kinds of using the socks:
putting the socks around the bowl extension ring and/or the soundstage ring:
- the resulting extended bowls are grado-like sounding, preferable for smaller heights of the bowl extension ring, much better sound stage width and slightly better soundstage depth, much more comfortable
putting the socks around the complete extended bowl so that the socks partly close the bowl on the ears side:
- the resulting extended bowls are more like a non-grado headphone sounding, but with good soundstage wide and depth, nice imaging and extended bass response. my idea here was that applying the socks this way the socks form a chamber for the ear and also a defined volume and room for reflections and this really works.
btw i was amazed that the new AKG K812 has the same style of "bowls".
How to test and build:
In general i put all parts together for initial listening
- when i tought a specific extended bowl would be worth listening i put the parts together using small needles
- when i had decided to finally build a specific extended bowl i used superglue to glue grado bowl, sound tuning chips and sound tuning ring together (only superglue on both sides of the sound tuning ships)
- to glue sound tuning ring, bowl extension ring and soundstage ring together, i used a special glue based on rubber and made to repair clothes, keeps flexible, is heat resistant up to 120 degree celsius, the hole bowl can be washed.
for my next post i will prepare some drawings how to build this closed grado version i mentioned before.
