Hi J-Bird,
I had the same problem when I first got my Jambox. Turns out the Jambox is a Bluetooth device of type "headset" with two "services": a mono headset service and a stereo headphone service.
iOS devices somehow correctly assign each device to its function and music automatically plays via the high quality "headphone" device.
Macs however see each device as equal and will connect to the mono headset service first, which results in poor sound quality.
In your Sound preference pane there should be two entries for the Jambox, one of type Bluetooth Headset, the other Headphones. Select Headphones an you're set.
Sometimes the connection will fail. Initiating the connection from my Mac usually does not work.
Turning the Jambox off and back on should make it try to connect to your Macbook Air. When the message pops up saying do you want to use this MONO device, click disconnect. A second message will appear offering the STEREO device. Connect to that one.
Also, I find that sometimes after a while the sound quality will degrade to a crackle, like the bluetooth signal is getting weaker and weaker. I have to turn the Jambox off and back on to fix this for the next few hours. This does not happen when connected to my iPhone or other iOS devices.
Good luck!