Thanks for the quick response!   I tried using both the foam pads and the rubber rings, and although the foam pads did improve the sound quality, they still didn't fit comfortably. So, I've ordered the MX580's; hopefully they'll fit better than the 581's! It's a shame that the 581's didn't...

Thanks for the review, ClieOS!   I had been looking for relatively inexpensive earbuds to replace my stock Apple earbuds, and after reading such positive reviews for the MX581, I decided to purchase them.   Unfortunately, I'm just not getting a very nice sound from them. I believe it has...