[yep]

EDIT: If you want to skip the theory and jump to the $100 room treatment recipe, go to part VI, below.

This thread is drifting dangerously off the path of hard science, but here goes (and this is partly summarizing/clarifying stuff that has been posted above):

Small rooms* are inherently difficult to use as recording spaces. The central problem is *caused by* low-frequency standing waves, but the effects are heard throughout the frequency spectrum. This is a really, really important distinction to understand. In very unscientific terms, low-frequency standing waves cause stuff in the room, as recorded, to sound generally boxy, ringy, indistinct, muddy, "peaky," and uneven. Generally cheap and unprofessional-sounding. It is *NOT* merely a condition of "too much bass" nor "bass buildup in corners" nor any of these kinds of well-intentioned misunderstandings that seem to think of bass trapping as a low-shelf filter for the room (although they may be some of the symptoms). It is a spectrum-wide, phase- and frequency-dependent distortion that happens throughout the room, and to different frequencies in different places, but happens throughout the frequency spectrum.

FORTUNATELY, there are ways of dealing with these huge, universal, full-spectrum problems that are CHEAP, SIMPLE, and EXTREMELY NON-TECHNICAL. More later.

What happens when you make a sound in an enclosed space is that sound radiates from the source, hits the nearby surfaces, bounces off them, hits the next surface it encounters, bounces off of that, and so on, gradually diminishing in intensity as resistance from the air and materials dissipates some of the sound energy as heat energy (a phenomenon called "absorption," since it's like the air and materials are absorbing the sound). When the sound waveforms are of a physically short length compared to the size of the enclosed space, the bouncing around randomizes the direction and intensity of the reflected sound at any given point in the room, and the result is a rich, even wash of reflections that we hear as reverberation.

Imagine breaking a rack of billiards balls and you'll get the idea-- everything ends up randomly scattered around, slowing down at different rates and so on, even though they all burst out from the same place with approximately the same force. Now imagine that you hit one billiard ball a LOT harder than the others, like, you shot it out of a pool-ball gun. It bounces furiously around and around the table and settles into a pattern, making the same path around the table repeatedly until it runs out of steam. This billiard ball is not only going to create a path where it clears out the other balls by knocking them out of the way, it's also going to create higher concentrations of billiard balls in the parts of the table that are *not* in its way. So it's going to disrupt the beautifully random pattern of balls and create unnatural areas of density and emptiness.

Now imagine breaking a giant rack of balls on a HUGE billiard table, the size of a swimming pool. This time, even if you launched some balls with the pool-ball gun, the table is so big that they end up scattering and randomizing just like all the other balls. The table is too big for them to settle into the disruptive round-and-round "pattern." If you see where this is going, you're one step ahead of the game already.

To be continued...

*"small room" in this context means any room that is not big enough to diffuse the wavelengths you're working with. A suitable room size for piccolo will be different than a suitable room size for double-bass. The smallest dimension is the most important one, but the overall size and shape matters. As a rough rule of thumb, a room with the shortest dimension being about 15 feet/4.5 meters is probably usable for general recording work, making certain assumptions about isolating bass instruments and not recording a concert grand, etc. A room with any dimension smaller than 12 feet is probably going to be a problem in any realistic scenario, since you are getting into territory where acoustic guitars and lower male vocals are creating problems.