the tv volume should also control the headphone jack volume. So set the speakers to a reasonable level, maybe half volume or something, and use your tv remote to adjust volume from there.
Here's more info. I disable the tv speaker on my vizio TV so it can be transmit to the speakers the problem is that when i click on the volume button on my remote is says TV speakers is off. so the only way to turn up the volume is the speakers i'm wondering if there is any devices that i can control the speakers volume.