The AMC B1-19 is a bass reflex 100 watt amplified subwoofer that uses a single 8 inch front firing driver with a tuned port opening the body. I decided to connect the woofer to the A500 integrated amp via the pre-amp outs rather than the stereo speaker connects to hopefully keep the signal and pure as possible. The K1000 remains connected to the speaker outs on the A500. Its also possible to bi-wire the woofer and the K1000 to the A500 but haven't tried this yet and i think i'll get cleaner sound with the current set up.
The K1000 with subwoofer combo is working out very well now that the sub is filling in the lower end down to 30 Hz. The upper freq cut off can be adjusted from 40 to 180 Hz. Currently i have it set at 180 Hz to improve not just the lowest freqs but also drum beat thumps and such which is also working out very well. The woofer has a volume control so you have complete control of the amount of bass enhancement you desire. It takes a while to get the volume set well being that the amount of bass in various songs varies widely. At first i had the woofer behind my listening chair because that's the only place it won't get in the way of things but it became clear it had to be moved because it produced too powerful pulses that actually made my heart feel like it was palpating during bass heavy passages. It was placed to the side of the chair next and this seems to be working out well...due to extreme space limitations i really don''t have many placement options but i'll try to squeeze it in elsewhere later...
As far as the amount of noise and thumping produced by the sub it doesn't seems to be a problem for me even for late night listening since you only need a little bass enhancement to do the job and anyway you can just turn down the woofer volume if need be and i notice i can listen to music at lower volumes now and still get satisfying, full sound...Actually the K1000 makes more "noise" than the sub being that the low freqs of the sub are less obvious but of course the sub adds thumping which might be felt in nearby rooms.
So with judicious use the subwoofer adds considerable improvement to the music and gives the K1000 an even more speaker-like sound that no other headphone can match much less beat.