So my friend as a Stax SR-X MKIII Pro and an SRD-7SB. He's experiencing an odd problem with the system soundwise. There's a brickwall effect on the bass; he literally has no content whatsoever below a certain point. The headphones otherwise sound as they should: extremely clear and clean, no distortion, very lifelike, etc.
The SRD-7SB has been modified by the previous owner to bypass the loudspeaker/earspeaker toggle switch. It is otherwise stock (ie has not been recapped) but he's taken a multimeter and capacitance meter to the PCB and everything seems to measure at proper spec. He's using an AudioSource AMP-100 with it.
I suspect something electrically faulty in the SRD-7 that's causing it to act as a sort of analog highpass filter. Any idea what the issue could be? I mean, I heard it before I sent it to him, and it sounded like something was seriously off with something in the audio chain. The previous owner thought it sounded strange too, and he was used to the 'stat sound. The SR-X does have completely decayed pads, we're working on getting replacements, but having heard it myself I highly doubt that the pads are the entirety of the issue.