does a subwoofer kill stereo sound?


I was wondering whether adding a subwoofer to a pure stereo system would cause any harm to the soundstage and other features of the system. What are your experiences? Should one buy a subwoofer to complement a great bookshelf pair (that may be lacking some bass) or necessarily one would have to buy a new par of speakers with deeper bass?
tvfreak
Regarding soundstage... In my own experience adding a subwoofer seems to perceptually expand the soundstage, particularly the depth. Larry Greenhill has mentioned the same effect in his subwoofer reviews for Stereophile.

This is exactly my experience.

Further, some of the assertions made in this thread seem to be based on a "perfect world" basis where we have unlimited funds, and unlimited flexibility in our listening environment. I think when you allow for the fact that this is rarely true for most of us, a subwoofer will provide a more optimal imaging than the alternative full range floor standers that may have limited low end due to budget, or sub optimal placement due to room limitations.
Re: expanding soundstage.

I've heard the same effect, but not consistently. Most recently it's become quite apparent on Allen Toussaint's "The Bright Mississippi" which I believe - and I am speculating here - features a very large bass drum. With the subs on-line, the recorded acoutic sounds much larger when that drum is struck.

However, I rarely hear this type of dramatic evidence of this effect on most other recordings.

Marty
OhJoy,
Isn't bass mixed to mono below.....say 80hz?
Also:
Given that bass wavelengths are longer than the longest dimension of MOST rooms, I'd say a sub was not locatable, eyes closed.

In large rooms, this may change.
I suspect that alot of information regarding a venue's acoustic space is very low frequency info that you can't quite hear on an obviouos manner, but is notable by its absence. If I had to use a subwoofer, I would only do so with close to full-range, or full-range speakers over a very narrow span with a very x-ver in the 30-40hz range. The less you ask of a sub the better it will interate and add without subtraction.
Martykl...Actually, I hear it quite differently. If you have a system that can accurately reproduce the lowest frequencies accurately (I am not commenting on your system) you will clearly hear low end pitch differentiation on those very powerful low notes. This is clearly the work of the bass player. Yes the drummer's kick drum adds some concussion when appropriate, but those lows are clearly the work of the bassist. I further speculate, that it is an old Kay plywood bass that's been electrified, and plugged directly into the recording board. In the song "Day Dream", the bass starts the tune, and the drummer comes in a couple of measures later.