I frequent a few other forums, but I wanted to pose this question here because I know a lot of you are very intelligent and knowledge about sound; and I trust your judgment.

I currently have a 250w KLH sub. It’s not a very good sub, but it has served its purpose for the time being. About a month ago, I ordered a sub from SVS. The sub came and I put it through the normal, rigorous tests. But, for some reason, the sub just didn’t sound very good.

When I had the KLH hooked up, I could feel explosions, the hum of a lightsaber and the thump of bass-heavy music from across the room. When I had the SVS running, all I could feel was a light vibration and I could hear the wall behind it shaking. I kept moving the sub into different positions around the room, but I still got this flat sound.

Finally I went over to the sub and placed my ear against it and I could swear I heard rattling.

OK, now this is the part well I need to be told if I’m crazy or not.

I wanted to figure out if 1) the sub was rattling (denoting that something was lose or broken) and 2) where the bass was going from this 600w sub. I accomplished this by doing the following:

1. I turned off all of the other speakers, thus isolating the sub.

2. I then hooked up the KLH in its normal listening position and played a particularly LFE-demanding scene.

3. I then repeated with the SVS.

This allowed me to hear that the sub was, in fact, rattling and that the bass was not reaching the seating area like the KLH was.

I’m being told that my “isolation” test is invalid and doesn’t really tell me anything about the sub. This makes no sense to me, so I leave it to you fine Axiomites. Am I nuts?

No you aren't nuts and I'm sure you are feeling somewhat frustrated. One thing about SVS subs is that they provide high output. Which one did you order? I suspect something has malfunctioned or jarred loose during transit. To double check, place the sub at one of your main speaker postions then raise the sub volume halfway and set the crossover to disable. Play a loud bass heavy passage. What do you hear?

Actually, the sub has already been returned. I got their new model of PB12-NSD. I was just asking about the test I ran. It made sense to me and I just wanted to make sure that I hadn’t lost my mind.

Thanks

As long as both subs were in the same place when you were playing them, and you were sitting in the same listening position each time, your test seems valid.

I think we would all be happier if your SVS turned out to be defective -- we were having a heck of a time coming up with another good explanation after a while.