Thanks for all the info!
By the way as I am searching for drivers to buy on taobao and aliexpress including various DD, I found something interesting.
After talking to various sellers, apparently there is a TWFK BA clone made by a chinese manufacturer that can be found on taobao named ..".domestic lou driver"...(lou is usualy the chinese name for knowles).
It goes for around 13$/piece, have the same sound characteristic and electric properties. I am pretty sure they are quite good but QC control and matching might not be on par...
Anyway just so you be aware. As far as I know most of Knowles driver that are sold in China are manufactured in Malaysia. These one are mad in China (I don't know the manufaturer yet).
IMO It might worth checking, I am also sure that many new DIY IEMS sold from China recently uses them.
On another somewhat related subject I have a question regarding wiring.
There is a variant TWFK numbered 31749 that have a cap already solderded to both of the positive pads
Now usually if I want to use both fk and wbfk part i need to solder a positive wire to both positive pads on the twfk and only one negative wire to the negative pads (as the negative are already connected) right?
But now I see that with the cap soldered, only one positive connection is made. Does it mean that the cap is working as an High pass Filter for both drivers of the caped TWFK and only one positive wire is necessary? Because a cap is an AC component in an AC circuit as long as both positive pads are connected only one wire is required to make the HPF work for both drivers?
I am a bit confused...
Edited by ForceMajeure - 7/22/16 at 10:59pm