A pair of Magnums used to be a complete build done by the Canadian site you reference. They were a stock pair of SR325is, with the original Grado drivers and plastic inner sleeves removed and replaced with aluminium inner sleeves and specially made drivers...Magnum drivers. There were five versions of the Magnum driver (with a few versions between whole numbers in between apparently). The fifth is the driver you see being sold on the Turbulent site. The aluminium gimbals and sleeves are no longer available. Neither is the build service previously offered by the Canadian site.
Note the "M" logo on the sleeve.
Note the aluminium gimbals replacing the stock plastic Grado ones as well.
The information found here is old, but pretty much covers the basic Grado mods:
The real fun with Grado modding comes when you get to replacing the stock plastic cups. Depending on creativity and resources, you can make yourself a pair of headphones for life. People make endless variations on the theme: wooden outer cups with aluminium inner sleeves, wooden inner sleeves with aluminium outer cups, one-piece full-woody cups (a-la RS1 style), outer cups made with one type of wood and paired with inner sleeves made of another...and the possible shapes are endless (do a Google image search, its fascinating)...
People generally use their Grado drivers, or upgrade to Magnum drivers (the Magnum are generally better than stock Grado drivers, but sometimes implementation and materials changes that). They also upgrade the stock plastic headband cushion with a nice leather one (the Turbulent headbands are the best aftermarket ones I have seen, but I never managed to get my hands on one of the much-lauded, now unavailable JMoney ones).
They also change the pads around, trying the G-Cush, L-Cush and the TTVJ flats to tweak sound as well...
Edited by fleasbaby - 4/23/14 at 6:06am