Anyway, I was bored the other night, which is bad when I have my headphones near and modding materials next to my desk. So, I looked over my cans and thought it over, and decided on the HD518s. I bought these for my wife but instead of using them she stole my 598s, so they've pretty much been sitting here. Honestly, I wasn't impressed with them, their bass was too boomy and flabby, the mids were muffled, and IMO they had some funky resonance issues. People may talk about what a value they are, but to me they really weren't much to write home about. I would have sent them back but I procrastinated until the 30 day return window expired.
So I took them apart and poked around looking to see what could be done and I noticed that there's some empty space in there, and I thought, "I wonder what some mass loading would do?". So I got out the Plasticine (modeling clay) and set to work. For a couple hours I played around with varying amounts until I struck pay dirt. Add it just around the outer rim inside the cup, they're very sensitive to the amount used, don't over do it. And be careful not to get it on the back mesh, it's a devil to get out. Here:
The bass tightened up dramatically, the muffled mids were better, and the resonance issue disappeared. Wow, were these the same headphones? I was impressed. So I called a friend who is a Sennheiser/Beyer nut and told him and he asked me to stop by. So, I got there we hooked them up and he was quite surprised and claimed they sound more like the HD650 now, we got his and compared and he was right. They didn't have the breadth of soundstage but the tone was similar, as was the attack and detail. It's a nice upgrade and worth the clay and time, IMO.
Any other ideas?
Edited by Magick Man - 2/10/12 at 8:40am