Got tired of trying to make the Grundig 211-A setup work out, so off they go to live in the project bin, I think I need to line the rears with adhesive felt rather than the creatology thin foam, not going to bother. It could be because they are shaped like a radar dish inside. Too difficult to tame those cups. Simply made me too irritated so this is what I whipped up tonight while listening to the recently modded Superlux 662F ( wow ).
Headset and wiring from an AT-701 , Alder cups cut out the other night, the old SFI drivers from the Grundig. I love working with this wood it's so light, strong, easy to work, holds a finish well just overall great.
I somehow managed to make them work absolutely stunningly with the damping scheme right off the bat, somehow. Had it in my mind about the Wikiphonia T-10 damping posted, so I sort of borrowed an idea from that, the stuff directly against the back of the driver, in this case it is Arctic Cotton ( essentially a fuzzier felt ) not Arctic Bamboo which is a little thinner. Secured by a ring of double sided tape to keep it in place during the driver seating.
Rears of the cups have a disc of soft adhesive backed felt~ 5/16 thick, a few spacers on the ridge inside to seat the driver on, doesn't need to be perfect ( as seen in pics ), and in the middle 0.2 grams per side of some fibreglassy-type acoustic filler[ Twaron Angel Hair ]. ( great depth to the sound due to that )
The gaping holes in the sides of the cups where the wiring enters and the SFI tabs seat into is all sealed off and filled up with Newplast plasticine so they aren't a problem now either.
Used the stock cable shortened by half and the stock grommets also at the top of the cup wire entry points. Strain relief is recessed and siliconed around at the main cable entry hole.
Bass ports are 5/32 . Any larger would be too much they rumble nicely now without being too overbearing.
These things are just soaking up the Watco natural oil so I am in the middle of waiting for them to absorb a few more coats, then i will secure the side cup mount points with some wood glue and done.
Don't know
something must be wrong I never get it right off the bat.
I can deceive myself about that sure but when you know it's right you KNOW. Maybe my lucky night? Yep wiring worked nothing crossed, cups swivel, sounds amazing. Hmmm.
How many times must I find something better than before and rework another pair I previously modded ( this case older Alder ones I have kicking around that are of a similar small cup interior ). Once again.
That reminds me some of my earlier posts in here make me cringe thinking back but it's all a learning process.
Looks like a hack job but once everything is done inside the cups its nice and tidy
Not a fan of bending down tabs on these drivers at all so that's whY I make the spaces at the top there ( filled in after )
I'm gonna give these a walk up to the coffee shop tomorrow morning, they do stick out slightly but are pretty much the same heights as the original AT-701.
Yep I did screw up, needed to move the cup attachments back a 1/4 inch. Could have been worse
EDIT MARCH 2014 should mention also this method is easy, keeps a smaller cavity in there, and doesn't require me to make extra baffles since the pads can be directly attached to the cups win win win especially when using SFI drivers
