Chances are that your TV has a "fixed" volume audio output. This means that the audio output level does not change. Look at the owner's guide or look closely to the back of the TV and the word "fixed" may be printed near the output jacks.
If you are lucky, your TV has 2 sets of audio output jacks. One is fixed, the other is variable. In this case, just swap the cables on the TV to the variable output jacks.
If you are not lucky, and your TV only provides a fixed output, then you need something to provide the BL8000s with a variable output. The easiest approach is to use a stand-alone pre-amp. Make sure to get one with a remote control. Alternatively, you could invest in a B&O audio master (BS3000, BS4, BS9000) that has an AUX input (note that the BS5/BM5 does NOT have an AUX input). You will probably need an RCA to DIN cable for this connection. Run the TV into the AUX port of the BS and connect the BLs to the BS.
Stan