Axiom Home Page Forums General Discussion Home Theater Has anyone listened to sub without mains ?

My brother-in-law's home theater room is at the "drywalled, waiting for taping and mudding" stage. Before everything was covered over, I figured we should do a quick check for rattles and buzzes while we could still rip off drywall panels without too much effort.

Rob picked up a VTF-3 at a good price a couple of days ago, so we went down to the basement today with my HK630, his $49 DVD player and the VTF3. Played a variety of DVDs (WOTW, Blade, Finding Nemo etc..) but couldn't get into the Avia disk because we couldn't navigate the disk properly. WIth a house full of kids we were unable to pry loose a TV to see the menus, and his DVD player didn't have any kind of display. Oh well, at least we could press "Enter" to play the movie then step through the scenes, although I never did find Darla Tap.

Bottom line was that I was not impressed with the bass output, although I expect subwoofer placement was part of the problem. Without all the other speakers (this was a time limited test because family didn't go out for the day as planned ) it was hard to tell whether the sub was starting to complain at lower SPLs than it should, or whether this was just an artifact of listening to the sub without the rest of the speakers. In fairness, even with my SVS 20-39PC+ I have been surprised how quickly you can suck up 525 watts and either start clipping the sub amp or hitting the limits of the driver.

WOTW was obviously the most abusive (have you seen the waterfall plots on AVS ? Solid red down to about 5 Hz !!) but we started getting flapping noises on pretty much all of the bass-heavy tracks. The woofer was definitely moving at least an inch peak-to-peak and I could feel the air from the port from 4-5 feet away so there was lots of work happening; I just didn't get a strong sense of bass at all.

I suspect a lot of the energy in "the bass noises" is actually coming from the mains but never really paid attention before. Has anyone done this kind of testing before, and if so could you offer comments ?

The room is a 13x30 area within a roughly 30x30 basement, but without a wall to define the 13' dimension. There are other walls in the basement dividing the remaining area into a number of small rooms, but roughly 1/2 the basement (HT area plus pool table plus bar area) is one open space of perhaps 4000 cubic feet. I know a single sub is marginal for fully pressurizing that space but I did expect better from a single VTF-3.

Thanks,
JB

Was your brother-in-law's sub new or used?

I use my Hsu VTF 3 in a 2400 (roughly) cubic foot space and it pressurizes the room just fine for me. The gain knob is not even past the first little hash mark, about 2/3 of the way there. I put the sub in the corner farthest from all other openings (kitchen and hallway).

I haven't tried testing the limits on the sub, so I don't know what it takes to get it to bottom out or chuff. "War of the Worlds" is definately the movie to test the limits with.

Is the HT area closed off from the rest of the basement, or is the sub trying to pressurize all 7200-8000 cubic feet? That's a lot of space.

I don't have much experience with large spaces and HT, all my travails have been with cramming everything into really small rooms.

I think craigsub can probably give you the best estimate of the Hsu's ability in a large room.

John, I did this a few years ago for the purpose of investigating if a sub could provide "tight" bass or could be "musical". All settings were left the same(i.e. the sub was rolled off above 80Hz), but all speakers(set "small") except the sub were disconnected. The result was neither tight nor musical, except in the sense that the material being played was music; relatively low level, dull, loose thuds was a fair description. Tightness of impact and musical qualities of, say, an instrument playing a 50Hz fundamental depend primarily on the overtones which aren't reproduced by the sub.