Hi RichieRich, were you ever able to figure this out on yours? I have the same problem and have completely exhausted myself troubleshooting and moving things around to try and fix it.

I was not able to get the sub to pair with the soundbar. Called Crutchfield (where I purchased), they were no help, did not have a manual. Called JBL and they did not have a manual either. Their tech had a unit in his location and he played with his to come up with a solution. If your sub is flashing at a different rate than your sound bar they will not sync. Turn the power off to both units. Reconnect the Power.  Push the sync button on the soundbar then push the button on the subwoofer, it they are flashing at a different rate push the button on the soundbar a second time possibly a third until they are flashing at the same rate. Once they are flashing at the same rate they will connect and you are in business. 

If your TV has a digital optical audio output: Connect the supplied optical cable between the TV and the SB250. You will then have to set your TV to send the audio signal to the optical output, and you will have to select the optical input on the SB250. If your TV has left and right (white & red) analog audio outputs: Connect the supplied cable between the TV and the aux input on the SB250. This output on the TV may be effected by the volume control on your TV. Some TV's will give you the opportunity to set this output to FIXED or VARIABLE. If your TV provides this option, set the TV speakers to OFF and set the output to FIXED. Then set the SB250 to the aux input and you'll be set. If your TV has a mini-stereo headphone/line output: You will need to purchase a mini-stereo to mini-stereo audio cable, and connect it between the headphone/line output on the TV and the aux input on the SB250. This output on the TV may be effected by the volume control on your TV. Some TV's will give you the opportunity to set this output to FIXED or VARIABLE. If your TV provides this option, set the TV speakers to OFF and set the output to FIXED. Then set the SB250 to the aux input and you'll be set.

When a speaker begins to pop, it means that it is receiving a signal that is clipped or distorted. This is telling you to turn down your volume control.It could also be due to an interference caused by a wireless router another wireless device like phones, tablets or computers for example which may be active around the unit. please try to turn off or move away any wireless devices and check whether the noise is gone. You can also try to move the subwoofer to a different location for a test.

What you are experiencing with the SB250's subwoofer is not normal. Try to adjust the bass level lower and see if the thumping noise will still be present. If it is, please submit a case at jbl.com/contactus and our Customer Service Team will be glad to assist you.

Two speakers work when in stereo. The CINEMA SB250 includes two-way, dual driver left and right speaker modules which both works that provides proper staging of the Left and Right channels when in stereo mode.

This seems very odd. Please try a different Bluetooth device with the SB250, to determine if it is a compatibility problem or something else. Also, be sure the Bluetooth device is not more than 30 feet away, with a clear line of sight. And last, try it with a different app. I've noticed that some apps are a bit quirky when transmitting BT.

The SB250’s dimensions are available on the Spec Sheet available for download on this page. The SB250’s dimensions are 32.7" x 2.5" x 3.1" (831 x 65 x 78mm)