Improve bluetooth signal mac pro

I have a cylinder Mac Pro and I use an app on my iPhone (5S, but soon 6S) that locks my screen when away. But, it seems the phone needs to be really close to the cylinder to be effective, ie. even in my pocket within proximity, I have problems. But, with the same phone, I have a Motorola Bluetooh headset that I use for the gym, and I can walk all the way across the gym, away from the phone, and not lose signal or sound quality.

So I'm wondering what can be done, if anything, to improve bluetooth reception for the cylinder Mac Pro. Has anyone else encountered this issue?

Thanks.