Room correction, DSP for dummies.

@david_ten - I’m sure someone could speak with more knowledge, but the ones i’ve used have a mic that comes with the unit, you put it into test mode and it sends a sweep frequency through the system, starting at very low frequencies, runs the range, then repeats. You can reposition the mic in some cases to try to even out the response in more places in the room, but my Fred Flintstone version is, the little microprocessor reads these sweeps, sometimes a 1/2 hour worth of them, and creates a number of filter sets. When the thing is done with this process, something signifies that (an LED or simply the beauty of silence) and you are in business. It essentially reads the room and creates a filter or set of filters to compensate for the peaks.
I’m using this at a crossover of 55 hz with a very steep slope, so it doesn’t mess with the midrange phase or introduce as many electronic anomalies as it might for a cheap plastic device. (I use a linear PS for it, not the supplied wall wart). I think what it does, sonically, is remove some peaks so the response is flatter. The bass sounds more contained, less amorphous, tighter. I’m reluctant to have such processing in the higher frequencies but I gather that can be done with better units, setting phase, crossover points, an altogether more elaborate device that goes beyond the simple task of smoothing out the bass response in a given room. I think the device is agnostic in the sense that it doesn’t care what the room or speakers are-- it just reads the sweep frequencies it generates and creates a filter set to compensate for them based on some algorithm or set of machine instructions. That’s probably the limit of my technical understanding.
NB> David, I don’t know if you addressed your follow up to Grannyring (whose real name is apparently "Bill" or both of us, since I’m also a "Bill) but you got my response FWIW.

@erik_squires - agree not a substitute for some treatment, including bass traps.

@whart   Thanks, Bill. Your post is really helpful. I've used room correction software for my home theater system in the past, and it was helpful... like you I applied it to the lower frequencies and for assisting with subwoofer performance.

And yes, I was addressing Bill = grannyring  : )

Interesting conversation and one I have some feelings about. I have this terrible personality defect that tends to make me dive way too far down the rabbit hole on most of my hobbies. I grab something and squeeze the crap out of it until I get a pretty good grasp of its ins and outs. 

Doing this in a number of different areas has been somewhat enlightening in that I have learned that some lessons and traits are applicable to more than one displine. 

So here we go with my guess as to what dsp is likely to be offering me, for what I want. I want economy. I want to know what the state of the art is. I want to be able to know where the mountain top is and then I want to see how close I can get by using my wits, cunning and personal style can get me to that exalted peak. 

If 100% costs eleventy million then maybe 95% is only $100k? Maybe i can snag 92% for $20k? 90% for $5000? 

We all know that most every product we consider is flawed. There are very few products at any price that do not deal with compromise. Even when you can find them the nature of this hobby is such that the product you chose still has to be compatible with every other part. It's a puzzle but the peices need to fit every piece, not just the one it touches directly. 

The fact that DSP offers me a tool to help minimize and correct some of those compromises I'd appealing to me. 

I desire to get as close as possible without it then use it as little as possible to get a result that would simply not be possible without it. 

Suddenly 95% may cost half as much as it did a decade ago. 

Too much contemplating the navel here folks in my humble opinion.  I think my earlier post said it well and I really have nothing to add.  Big fan of removing the room’s impact as much as possible so speakers sound as designed, not perverted by room and speaker placement compromises.  Not all room correction designs are created equal and some do a much better job of doing no harm. Lyngdorf nailed it as proven through use.  

@david_ten The contemplating comment was in regard to your post with many more questions. I just don’t know how to say it any clearer or more simply? No, outside of the builder’s written or verbal comments on sonic design goals I don’t know exactly what they are shooting for. I don’t need to. Remove the room’s impact as much as possible and the speaker is free to be what it was intended to be....a high fidelity instrument.