Originally Posted by preproman
I'm not touching mine. I like them just the way they are. I'm not sure how you could shelve the treble and increase the sound stage at the same time.
However, I really trust BMF - he's been at this a long time.
There is a physics explanation I won't go into but the short story is that Fostex's materials have some variations that cause peakiness in treble output on some but not all phones, and it can vary by lot. The peaks are narrow, they are not on every headphone, they are within spec, and they are at a frequency that some people are sensitive to, and others are perhaps not.
But we're OCD about continuous improvement and I know many of you share our passion for this, so we thought the best thing to do was just put it on the table in a way that is fun, reversible, and customizable.
The BMD reduces two specific peaks by 2-3 dB with only about a 0.5dB decrease in the overall treble. Unlike the BMD the felt discs act like a broad band filter, trimming about 1dB off the highs for each disc to create a darker sound, if that's your preference. They work with or without a BMD installed.
Ears and taste differ widely, and in fact ear shape and geometry have an effect on whether you perceive a peak or not. If you are happy leave it alone!