DL1 drivers construction tolerances... Wualta, I'm not sure if you had a close look at them. You will lough loud at the standard. Cheap as it can get, all lousy and bendable plastic. There is nothing precise there. ... Simply the design is right and simple in first place. Best example of great engineering.
I don't think you've read my earlier paens to the ID1 ( = "DL1"?), not that I blame you. The ID1 is sui generis, off by itself, a rare boid, a kind of hybrid ortho-ribbon. All bets (and generalizations) are off. But you're right, I've only had the chance to hear one ID1, one that had been restored and slightly modded by Smeggy, and though I didn't disassemble his ID1, I'm pretty certain, as I've said before, the only precision part in the ID1 is the diaphragm.
The question becomes: why didn't anyone, including Wharfedale, ever follow in the ID1's design footsteps? The low sensitivity, maybe. Smeggy's headphone also had a strong narrowband resonance in the midbass, but again, it was in the process of being modified. Your guess is as good as mine.
Now... why LCD2 are so expensive and heavy then?!
Because they, and everyone else, have decided not to go with the ortho-ribbon design. High sensitivity needs powerful magnets and powerful magnets need a strong, rigid magnetic structure to keep the driver from flying apart. Big diaphragms with a chance at some air damping (like a 'stat) mean big structures, so even more weight. Then the woodiphiles want their wood on top of that. The result is a big serious heavy 'phone. The idea was to get enough sensitivity to allow use with today's headphone outputs. Remember too that the Audeze 'phone is sold in tiny numbers, which drives up unit cost. All the hours they spent tinkering and tuning the thing is reflected in the price as well.
For a pair of SFIphones I really would prefer a closed schema as I want to use it at the office. But I tried Ludo's search engine. The references to sfi are too many and only few are related to specific construction and results. It is close to impossible, for example, to build a full list of fosterphones used with opinion about their impact.
Don't forget, many of those efforts were experimental and thus unfinished. Rather than trying to compile the early information, start in Ludo's search engine with <smeggy> and <sfi> and you can go on from there. We've learned so much about the rest of the headphone and how it works as a system since the days when we discovered the SFI driver that it's probably best that you start fresh. Just don't have a tiny driver trying to drive a huge empty earcup all by itself and you'll do okay.
About the polyfill stuff, it is not available over here but I ordered some cashemire long fiber wool.
Wool is used for everything in England, it seems. It has unique acoustic properties. Try to find a source of inexpensive thin wool felts of differing densities.
Sulvaat, since I don't have any of the portable gear you mention and you don't specify what your receiver is, it could be anything from the rattling of a loose component to clipping in your amps. Perhaps there's a short in your cabling. I hope someone here will recognize your problem and intuit an answer.
