Odd headphone issue

[MoonBassAlpha]

I've an inexpensive pair of Sennheiser earbud type phones that I have previously a-b'd against my 2 other pairs and found largely similar, ie no noticeably nasty artefacts.
I just converted (wav-mp3) a tune we recorded and checked it on my buds and it sounded terrible, overly bass heavy and a little distorted. Went to get my good headphones (over ears)to rule out pc soundcard or conversion issues and, thankfully, all sounded fine.
Is it that the buds have somehow deteriorated (but both channels the same?) or the fact these go in my earoles not on them?
If I had to guess from the sound, it's like they've got fluff in them pressing on he diaphragm, but they look clean enough and the fine mesh should keep anything out that could make that sort of impact, shouldn't it?

[vbance]

I'd try listening to any other recording and see if the buds give you the same result. If so it points to the buds if not the recording. Usually using buds, bass can increase or decrease depending how far you push then into your ear.

[MoonBassAlpha]

Well, mystery solved.

I took them in to work and inspected them under the microscope. The mesh pieces protecting the diaphragms were completely clogged with wax. The mesh is so fine it isn't at all easy to see if the gaps are clogged, and the fine mesh isn't all that easy to clean.
Fortunately they pop out quite easily and scrubbing with a cotton bud and iso-propyl alcohol has mostly done the job. Some bits needed poking through with a very fine strand of wire.
I hope this helps someone, as I was certainly very near chucking them out. Good as new now!