Is the HE-1 2.4um? Odd thickness that, as I believe DCA also use it for their sets. I just hate working with anything less than 2um and I have so much of the stuff, so that is what I use. As for the bias, any change in that will make a difference but higher bias is always better but comes with its own challenges. There is no benefit from using 230V and the SR-Lambda has its own reasons to sound the way it does, nothing to do with the bias. Blaming the diaphragm thickness for how something sounds is also very misguided, I adore the HE60 (which uses the same diaphragm material) and I also really like the Lambda Signature, again 1um. It's all about the driver tuning and what sound you are after. My issue with the HE90 was always the utter lack of meaningful bass output at certain spots and that's down to how they were tuned. Btw. the "clones" are now in a fully redesigned version of the housing (well I've sent out for a newer one still to be made) and fitted onto a NOS headband. First prototypes of the metal backs are also ready and look great. Just have to be fitted to the new housings when they arrive. Parts for the DIY headband are also en route and we'll see if that design actually works. Also probably the final prototypes of the "axles" so I should get them properly made soon. Those who know the HE90, know those are bloody expensive tiny pieces of plastic. Also new spacers, dust cover pieces and a redesigned stator too... Now fitted with real HE90 earpads and they have no reason to sound this good. Far from perfect but I'd take these anyday over the original. Still a tiny bit on the bright side and with a bit of a midbass hump Now I just need to make of these "clones" and cram a Stax Lambda driver in it. That upset so many people I kinda have to do it again...