Guys,

I am considering Accordion doors to replace one side of my HT wall to open up to the rest of the basement to make it multi-purpose.

Any one used it before? any suggestions for brand or general tips?

No such thing.

If you covered the door in something it would be better than a wall opening but don't expect this accordion door to stop any sound transmission.

It has been discussed before. It is a bad idea, and you won't get anything soundproof about it. It depends on what your priorities are good sound or opening this room up, which makes no sense at all, since you really don't want a theat open to a room with light, other sound, and other activities. But if that IS what you want then don't expect to keep sound in or out nor to have great acoustics.

I'm with the OP, pkoduru, in seeking a flexible solution. If one has no choice but to have a movable wall as part of the design, how do you best design for maximum performance, while accepting the compromise?

If I can make my home theater open up when desired to an adjoining sun room, it becomes multi-purpose, and therefore I get to build it.

We actually have a large sound isolation movable wall/door at work. It closes in a garage door sized opening, sliding into place and then embeds (metal clad on both sides, foam core). The resulting 'wall' has an additional sound isolation person-sized door of the same design embedded with very heavy rubber gaskets to air & sound seal the room to some degree, and it works. (TV production studio). The way it is set up wouldn't be very attractive for residential design, but the same concepts should be able to be applied to a residential solution AND make it look acceptable, performing in some degree as a sound barrier (filter?).

Quite a few forum posters have deployed solutions that open up to game rooms or other parts of the basement with varying success. So closed-in totally dedicated 'bat cave' is not the only viable solution, but like others have stated, it depends on priorities.

Movtarget

I am seriously considering the doors.. any one did this kind of design before

how about something like

http://www.custom-accordion-doors.com/index.php/residential-and-commercial-accordion-doors/acoustic-partitions-for-accordion-doors/

Those are often found in classrooms and the like. They are hideously ugly. And they are marginally effective for voices and the like but definitely not that appropriate for more serious sound isolation. It will be a serious downgrade from a well-built wall structure. But obviously it would make the area more multipurpose in terms of opening it up. But bass and the like will go through that like nothing.

Their website you linked seems quite fair, citing the walls as appropriate for "moderate" isolation, which means basically for moderate voices and the like, the STC rating there is 33, which is not too high.

Take a look at these guys:
http://www.modernfold.com/Products/range/Space-Division-Products/index-c-2703-,Acousti-Seal_Operable_Partitions_177,177.html

Their ModernFold Audio Door has a STC of 44 and they have other non-accordion systems with ratings as high as STC 55. This compares with a Safe 'N Sound door with engineered low density composite with a rating of STC 27. I got that rating from this document:
http://www.masonite.com/BUILDER/Spec_pdfs/SafeSoundArchSpecs.pdf

I have worked on many commercial projects where doors like that were installed. The installed cost is around $800-$1,000 per linear foot of opening (this is the number I would quote to someone if they asked me right now), plus you need to install an overhead support that will run you another couple grand. Most of the makers of the doors will not sell to individuals anyway and they are not easy to install (though having seen it done a few timess, I am sure you could do with with help from a few friends if you tried).

They can work surprisingly well though, but will certainly not be soundproof.

The movable walls are definably very pricey, their accordion doors are more reasonable. Below is a pdf describing their accordion doors:

http://products.dorma.com/all/Product-Info/Catalog/ACF303.pdf