Okay, there are 6 models on the page you linked to. Which one is it?
And you said you're having trouble with your friend's sub, not yours, so what make and model are your friend's sub? Is it a passive (unpowered) sub like yours, or is it an active (powered) sub?
Wild guess here:
- Your buddy's sub is self-powered.
- Your running a connection from your HTiB's subwoofer output to the powered sub's speaker-level inputs.
- The fixed crossover in your HTiB is relatively high and/or the crossover (or low-pass filter (LPF)) on your buddy's sub is set even higher, which is why you're getting mid-range / vocal audio through the sub.
IMO, replace the HTiB receiver/player with a proper A/V receiver (AVR) and Blu-ray player, and add a decent sub.
You'll need to figure out a budget but, roughly speaking, you can get:
- a refurb Denon AVR-1612 off accessories4less.com for ~$200;
- a new Blu-ray player for $100 or less; and
- a Dayton SUB-1200 subwoofer off parts-express.com for ~$110 on sale.