Room correction, DSP for dummies.


I have not paid a lot of attention to audio for some time, almost 15 years and as a result I am trying to catch up on some of the innovation and tech developments that have been popping up in that time. 

One of the more interesting to me is the advent of electronically guided digital signal manipulation to help quell small system issues and room reflections. It seems wildly promising but  the few systems that I have read about that seem to work well look to be  painfully expensive. 

Reports have seemed to indicate that this technology was making its way into other, more affordable formats but I guess I just don't understand or grasp where the field is going well enough to know where the bulk of the technology is and how its manifesting in our hobby. 

Who can help shed some light on where this tech is, how  its being applied and how can I make use of it without selling a kidney? Maybe that last part is not possible yet? 

Thanks in advance! 
128x128dsycks

Eric:
REW allows you to specify any curve you like for frequency and impulse correction and you can make it mostly flat as I have done so with my summer home -- from +/- 3db for 16 to 30k hz.

Check it out -- its free. If you do your own EQ you should give it a looksee if for no other reason than to see its design and capabilities.

BTW, have used DIRAC and know its final result to be incorrect -- after running the software it shows a completely flat line for frequency response and this is never going to happen in the real world. There will always be spikes but you can control them within ranges.

craigl : 

Thanks, I don't need more room measurement/microphones or DSP toys. :) 

I built the correct EQ into my speakers instead. I use DSP modestly. On the sub and on the center channel (depends where the center is). 

Best,

E

the room correction assures your speakers sound as the designer intended in your particular space.

The speaker is now able to sound as it should without room editorializing and degrading.

@grannyring  Bill, thanks for your response, but it still doesn't clarify things for me. I'll try with more specifics. 

What you are saying begs the questions:

- how does room correction know which speakers you have? Yes, some speaker manufacturers provide their specifics, but how complete are these? Is this a perfect system? Is it based on anechoic figures? If so, can one's real life room ever be anechoic?

- how does room correction know what the speakers sound like or are designed to sound like? This isn't a simple question. ["sound as it should"]

- which leads to the far trickier how do you know what the speakers are supposed to sound like? 

- or that your interpretation of the sound is what the designer intended?

- does the designer know what he or she "intended for your particular space"?

- are you trying to re-create the speaker designer's space, as being the ideal? Is it? Do you know it or does room correction know it?
 
There are more, but I'll stop with these. 

I'm sure this is coming across as being difficult, so let me apologize in advance. Looking forward to understanding and learning. Thanks.
@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  : )