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! 
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I used to be a "purist" but....
I got religion with a modest home theatre system that was in my front parlor-- nothing especially WOW, an older Meridian pre-pro that was a cast-off from the bigger projection system, a McI multichannel amp and a small array of Mirage speakers. Like I said, nothing special, perhaps a little better than a ’box store’ system.
I finally discarded the Meridian b/c it was long past its sell-by date, and bought a mid-range Marantz AV pre-pro. It came with a very basic form of Audyssey. The degree to which that tightened up a fairly small powered woofer in this modest HT system was surprising, at least to me. Most evident playing the music from a soundtrack on a Blu-Ray disc.
I now use a very modest DSP (DSpeaker 8033II or whatever the latest model is) to control a pair of 15" sealed subs in my main two channel audio system.

They are powered from a separate line out on my line stage so the main speaker system, with its integrated woofers, runs full range and the DSP unit is not in their signal path; it only affects the subwoofers, which are, after the test signals were run, set to roll off at 55hz on a steep (-24db/octave) slope. It’s a fairly big room, and I’ve managed to get these subs to cohere nicely with the main speakers, which are Avant-garde Duos, a hybrid horn-dynamic woofer design.

I’ve very sensitive to discontinuity-- having lived with electrostats for decades and never satisfactorily blended dynamic woofers with those, this works. Not a huge investment in wooferdom, or in the DSP unit. I gather than these units work by lopping off peaks, not adjusting for dips in frequency response.

The result is not an audible deadening of the music- perhaps because I’m rolling off pretty low and keeping the DSP unit out of the main channel signal path.
Certainly cheap enough to experiment with----
I love DSP, but it is no panacea, and no magic computer that gives us the right answers.

I agree with most of what @grannyring said, but I feel this needs more discussion:


Room Perfect room correction takes the room out the equation and
deals with these room sound degrading realities. The speaker is now able to sound as it should without room editorializing and degrading.

The problem here is that we are honestly dealing with a number of personal choices that make it into software. There is NO room correction software that uses a purely objectively neutral curve. None. They all pick among possible good target curves and make choices about the detail level of the correction. This is a reason why I prefer to do my own EQ, and really like JL audio. They use the same curves I do, but cost about $15k more per sub than I pay. :)  

Further, there is no room correction software that works as well as it would with bass traps. So, yes, in a bad room EQ is better than nothing at all, but not nearly as good as EQ + bass traps and proper sub placement.

Also, let's face it, a lot of highly touted "high end" speakers are not objectively neutral nor are they smooth to begin with. If you buy a speaker for the sound, and you DSP it, your speaker selection and room correction can really be at cross purposes.  The point is, not all room correction software is the same, or moving to the same goals you are. You should absolutely listen to a variety and see which suits your needs, or which can bet tweaked best for you. 


Best,

E

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.