My ULD-12 Velodyne sub has been going great since 1994. It's a fine sub, but I use it
for music only. I wish I could of afforded an ULD-18 back in those days, but the ULD-12
at $1000.00 was it. I think the ULD series is great for music, but lacks for home theater.
It just doesn't have the slam or fast responce time of present day subs like SVS, HSU...
eD, etc and so on....maybe because it is sealed, don't know.
But I've never had a ULD-18 so I could be wrong. My reference point is the ULD-12,
which I use in a seperate/stereo music room only, along with a pair of Mirage M5si's.
The cabinet construction on the ULD-12 is very nice IMO, and is probably as good or
better on the ULD-18.
It's an older sub and I probably wouldn't pay over $600 for it.
I have a HSU-VTF 3 MK3/w turbo in my main home theater and it cost me $799. I didn't
have to pay for shipping ($100) or sales tax. I picked it up at their headquarters
because I live relatively close by, and paid cash. It's a great sub for music and movies,
will fill a room up with deep base (down to18 hz) and has a very large output due to the twin
ports and the turbo. Good for rooms up to 6,000 cu ft.....link:http://hsuresearch.com/products/vtf-3-mk3-turbo.html
Regardless, the ULD-18 is a classic, great sub....but because of it's age, I would be a little
leary about purchasing one.
But regardless, whatever you deside, best of luck...vardo