What do in store listening tests prove?

Please don't take this as the next swipe at retail HT stores. No hidden agendas to boost my ego or salve my conscience. Just a question that I know you all must have more experience with.

When you demo a piece in a theater or studio at a store, what is it really telling you? My instincts suggest to me that all you are really able to validate is how you like the products' sound or performance relative to the the other components it is attached to and the acoustical qualities (or lack thereof) of that particular room setup.

Is there any way to make some educated interpolation of how a product will sound in your own personal listening environment based upon how it sounds in the showroom, short of taking it home and demoing it?

With the exception of speakers, in store demos are now of little use to me as I already have a good home stereo system. Any new equipment I consider, I insist on an in-home audition.

But if you're just starting out in high-end audio, you probably will need in-store demos, and hopefully you can find a good sales rep to work with. They can be an invaluable help in putting together a good sounding system-- especially if they have several brands and types of gear available. Cheers. Craig
Well if you dislike the sound it will eliminate it from your list, if the dealer can not make the gear they sell sound good in their show room then it is safe to say that it either sounds poor or they are morons, either way you shouldn't buy what ever you are listening to there. If you do in fact like the sound, its time to talk about an in home demo. So you are right you can't make an accurate decision in the store, but you can make an eduacated in home demo decision. That being said I have never bought a piece with out some serious listening time in my room- its a lot cheaper that way- trust me.
Two things:how badly you really want to buy anything and how good this store is.The rest is questionable unless you already know how most components in a particular system sound.
I buy stuff without hearing it anywhere. No problems. In-store - unless, as Tim says, the dealer can make it sound good, there's no reason to consider it. Listen nearfield. If not speakers, listen through speakers you know. In-store demos of speakers are usually enough to discern the character of a speaker, because speakers are very different from each other and their quality shows through even in an unfamiliar room. But, with big speakers with lots of bass, although it's difficult to arrange, an in-home demo is best.
If you bring with you some music you are familiar with and have heard on a number of different systems, you can tell something about transparency, sound staging, extension, and so on. If you are listening to something unfamiliar, it's much more difficult. The easiest way to impress is to play a well engineered recording.
Kinda like taking a new car for a test drive. You won't really know how it will perform once totally broken in, or if it will suit all of your particular driving needs or all driving/road/weather situations. But it will eliminate those vehicles that aren't suitable, leaving you with a short list. And you will get a fairer shake with more knowledgeable salesmen at a good audio/video store!
In-store listening is the first step, sort of an introduction to the product that narrows your selection. The second step, and IMO the most important, is to take it home for evaluation to see how you like it in your environment. A repetitive and time consuming process, yes, but considering the price tag, a necessary one. What's the alternative? Buying without trying? Not for that kind of money.
I don't frequent high end salons often, but I was just at one on Saturday. What I learned was the most important thing is the recording. I stopped in to listen to their 'top room'. It had a pair of Dynaudio Confidence C4's being driven by $12,000 Krell monoblocks (I don't know the model number) through Transparent cables. I listened for a few minutes and was extremely unimpressed. The sound was sterile, and uninvolving. There was a guy in there drooling over the Krell monoblocks, I remember thinking 'Why? My system smokes this junk.'. Anyhow, I spent another 45 minutes going through other rooms, as I was getting ready to go, I stopped back into the Krell/Dynaudio room. The sound was phenomenal. I sat down and couldn't believe how rich, warm, BIG the sound was. It was a different cd playing. I always knew to bring my own software when making a serious audition, or it's best to try in your own system, but I had never heard a system change so much just by changing a disc. I left wondering why they would even play that first disc, it couldn't be good for sales. Although the guy drooling over the Krells didn't seem to notice.

Some very good responses so far. I do believe once you get experienced, you can get good guesstimate of what it will sound like in your room with your gear. Certainly narrows down the field to a usable size. The thought of trying every interesting piece in ones home is daunting. When would one forget about the gear and get on with what this is supposed to be all about; the music.
The two biggest variables you will encounter relate to software and room effects. These are even more significant if you are purchasing full range speakers. You can minimize the software variable by taking your own CDs/LPs, but you probably can not duplicate your room. Some dealers have very good rooms and others have horrible setups. Once you have shortened your list via in-store auditioning you will need an in home audition. Taking the piece(s) home over the weekend while the store is closed is best for the dealer as he/she can not sell if the demo unit is not in store. I do not think trying to do comparisons between similar prospective components at home the first weekend is wise. You may not have enough time to carefully absorb the differences. Be sure and get the unit(s) warmed up too. Take one piece home one weekend and the other the next. Take notes. Maybe do a "shoot out" on the third weekend?
In-store listening is to narrow your list to what you want to listen to at home at best.
If the set up is right, and associated gear matches well, you can at least get an idea of what you're dealing with at a store. Still ultimately, trying in your own home/system is ideal.
A savvy dealer can put together some pretty nice sounding equipment combinations. Recently heard a pair of Quad 989s paired with a Plinius SA 102. Wouldn't have missed this for the world. Killer combination. Bought it for VERY fair money.

I visited a very accomodating dealer last year who swapped an entire line of CJ tube preamps (4) into a system that included a pair of speakers I own. Couldn't believe the difference between the 17LS and the 16LS (although I should have realized that the doubled sticker price has to buy you something). I count this among the most valuable listening sessions I have ever had. The salesman earned my loyalty, and his store my strongest endorsement. My only regret is that this shop is not closer to where I live.

However, I note TWLs post in another thread: "I would rather go to the dentist than walk into a high end audio dealership". I have had this experience as well.