Day of Defeat:Source frustrations

By far my favorite shooter is Day of Defeat:Source. Well, I technically liked the old one a little better, but that's irrelevant. I hadn't played it in a while, so the other day I reinstalled it, and after fooling around a bit got my config back to the way I like it. I'm not a graphics junkie for most games, as long as they're fun and entertaining, so I like to turn a lot of the extras off when I can for better performance.

But here's the thing. Back when I played the game a lot, I could play it on my (mostly) current hardware setup with maxed out graphics and 60-100 fps with no problem whatsoever. Now however, I get about 50 fps when I first load the game and log into a server, and over a period of about 5 minutes my framerate gets worse until it locks in at 9 fps, maybe jumping up to 15 if I'm inside a small room or something. If you've played any shooters, or hell, any game at all, you should know that anything less than about 25 fps is almost unplayable.

It's definitely not server lag, because my loss and choke numbers are fine. It's a hardware issue on my end, that much I know. Now, the only difference in the hardware on this rig between when I played a lot and now is with audio. I have an Audigy 2 card in the machine, which isn't a high-end card, I know, but it's what I played with in the past. The thing is, I'm not using it right now. A year ago or so my headphones gave up the ghost, and in order to have any sound at all on my machine (a necessity) I went out and bought a cheap Microsoft Lifechat set of USB headphones.

I'm wondering, and if anybody actually reads this maybe they can confirm, but is it possible that the audio is what's causing my fps to drop? I notice my fps starts to go down whenever I get near a machine gun, stays at that level, then drops a little more when the mg fires again. Is it possible that the audio from the game is taking up too much cpu? If I had 2 monitors on this machine I could probably watch for that, but I don't have 2 monitors, so it's a guessing game.

It's not a huge deal, because I've got a much better set of headphones on the way already. I've been planning to get a new set for a while, and they're not USB headphones this time so maybe I'll end up answering my own question. The only other thing I can think of is that my video card is getting too hot as I play, but if I shut down the game and restart it my fps is back up to normal again. I wouldn't think 30 seconds would be enough to cool the gpu off enough to make that noticeable of a difference. I suppose I can test that, too, by sticking a huge honking fan in front of my machine, but I'm still leaning towards the audio issue.

Anyway, if anybody's heard of this issue or something similar, I'd love to hear what you found out and how you resolved the problem. I spent all evening cracking my skull on my desk, and I'm not sure what else to consider at this point.