House shopping. Concrete basement walls/drop ceiling

Carpet and suspended ceiling tiles absorb well over the vocal frequency range. Your primary issues will be in bass modes. Find a room mode calculator (Harman has a nice one) to find how your room dimensions map into room modes.
http://www.harman.com/EN-US/OurCompany/Innovation/Pages/Calculators.aspx?CategoryID=Calculators

You can't avoid modes, but you can space them evenly and avoid co-incident modes, as occurs if, for example, room length = 2x width. Room dimensions are in your control to the extent that you plan to build internal walls, or perhaps need space for acoustic devices, a false screen wall, room dividers, etc.

You can manage modes with acoustic treatment, but most broadband absorbers have very little bass absorption, consistent with your observations. I recommend reading Chpt 12 here, paying attention to a) characteristics of what you've got (drop ceiliing, carpet) as well as b) treatments effective below 100Hz.
http://andrealbino.wikispaces.com/file/view/Master+Handbook+of+Acoustics+-+5th+Edition+-+F.+Alton+Everest,+Ken+C.+Pohlmann.pdf

Finally, it's very helpful to have acoustic measurements available. High-Q bass traps need a target frequency, and lower Q devices still benefit from being centered in their frequency response. Ears and test disc/frequency generator will do for first-order problems. From there, it's all in how sensitive you are to the residual issues. Here's a link to a freeeware measurement program; mic/mixer/cable is about $100.
http://www.hometheatershack.com/roomeq/

And as always...

HAve fun,
Frank

Dimensions! 14x35(x8?) isnt' bad as long as you don't divide the 35' space at 14' or 28'. I don't see a reason to divide across 14', I just hope the ceiling height isn't 7'... we're trying to avoid dimensions that are integer multiples of one another.

How you build is up to you. Most folks cover the concrete to get a finished look, but concrete has some acoustic advantages. Can't find the reference now, of course...

Got to run,
Have fun,
Frank

Sad to hear; I'd love a shot at 9' ceilings....

But it's still true that "carpet and suspended ceiling tiles absorb well over the vocal frequency range..." No surprise you didn't get an echo.

HAve fun,
Frank

Yelling and listening to music are quite obviously two different things. Music covers a far wider frequency range than yelling!

Carpeting is among the worst sound absorbing materials I can think of. It is a narrow-band absorber, almost completely zero in the bass and not better through the lower midrange.

Face it. Setting up a good sounding media room will take a lot of planning and work. What you see now will be completely overlaid by the time you are done.

What would I do?

(1) Set up an dedicated entertainment space that occupies only part of the basement.

(2) Partition off an outer sanctum with food and drink service, space for standing and talking and sitting and talking. Easy access from the stairs. People walk down the stairs and the hospitality suite is laid out before them.

(3) Partition off an inner sanctum for the media room that is almost completely isolated from everything else as much as possible. The room that is above it must be a space that is not going to be used at the same time.

(4) At this point if I were building a media room I would be OK with a hard floor - even concrete covered with a decorative epoxy finish. I would concentrate on the shape of the room, and the deployment of both absorptive and diffusive elements on the ceiling and the walls.

IME the ideal "hang out room" is what I described. I reached those conclusions because of how I've seen crowd dynamics work out at 100s of social occasions over the decades. Some things never seem to change!

I think the question is one of degree - to what degree do you want dedicated spaces vs. multiuse spaces? There are advantages both ways; Arny's media room would be a heck of an HT, but what if you want to play pool while watching a basketball game, or perhaps at halftime? One can always use a "zone 2" scheme for sound outside a dedicated HT, perhaps with a second video display as well? A doorway at the HT would split the sound field, surround inside, stereo outside.

The simplest metric is usage: build a space you'll want to use often, based on the kinds of things you want to do. Nothing wrong with a bar-style appraoch - multiple video channels displayed, generally good sound but no "front stage" per se - just as a dedicated HT may be perfect for folks who love movies.

It's up to you what sort of space, and you have some time.. let's hope more folks have ideas...

Have fun,
Frank