Any tricks to keep cats away from speaker grills?

Remove the grills.

tear gas

All you need is a spray bottle of water when they get near the speakers douse them a few times, works like a charm. As far as the repellents go I have tried several and found them to be uneffective.

Damon

http://www.sharperimage.com/us/en/catalog/productview.jhtml?sku=SI478GRY

Pet Peeve Ultrasonic Trainer
#SI478GRY
$39.95

Keep pets off furniture — even when you're not at home!

Record a command to your pet ("Off the chair, Rover!") up to 10 seconds long.
If your pet jumps on furniture, a motion/vibration sensor is triggered.
Sensor causes playback of your command and a safe ultrasonic alert.
Features adjustable sensor sensitivity and ultrasonic alert-only option.

Of course, this is assuming that your cats actually LISTEN to you :-)

The water bottle works wonders. You just have to be consistent and get them each time they go near it.

Best of luck,
Angela

Some people cryogenically treat their cables. Try it with the cat, and I guarantee you won't have the problem again.