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! 
Well I have one way that worked for me as well as other picky Aphiles. 

- sell your dac
- sell your preamp
- sell your amp
- sell the power cords and ICs related to these products 

Take this sum of money and buy a Lyngdorf 2170 one piece audio system with SOTA room correction.  Great unit that replaced $18,000 worth of stuff for me with no regrets.  Lyngdorf also makes the  model 3400.  

Read up on it and decide if this is a viable option for you. Sound quality is first rate and the room correction assures your speakers sound as the designer intended in your particular space. Depending on what you already have for separates you may save money in the end. 
I moved to a patio home where my listening room is now my living room so room treatments are not much of an option other than , carpet on the floor, bookcases full of books , upholstered furniture, drapes usual living room stuff. I got a micromega M100 with MARS  room correction and it has worked well for me. Took a couple of times placing the speakers and running it. If you have a dedicated room I couldn't say this approach is better than room treatments but it works well in my case. I can tell a big difference between the correction on and off as it gives you  the ability compare. 
Investigate the impulse/frequency convolution file created by the free app REW that can be imported into lots of music editors such as JRiver (very inexpensive). Will tune your room to a very high degree depending on how much time you spend correcting the frequency curve in REW.
Very interesting.

So it seems there are some decent options AND competition that are already under $1000!

I can just build my system then when I’m ready grab which of these best suits my needs and plug it in between source and DAC/Pre and go to town!

I look forward to chasing down information and deep reading on the products listed!

Thanks crew! Super helpful!

Has anyone compared the Lyngdorf 2170 to some of the other similar products? like the new Anthem 2 channel products with ARC room correction (there's a pre-amp and integrated amp). I'm sure there is others out there.

Grannyring you mentioned you used the Lyngdorf on your Living Voice speakers I also have Living Voice's just wondering how you liked it on them, I've only had SET tube amps on them.

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

@grannyring Bill, I’m scratching my head regarding the sentence above. It’s confusing to me, if I interpret it at face value. Can you explain further? Thanks.
Builders voice their speakers to sound as they desire. Many work hard and carefully for a certain set of sonic attributes, wether it be neutrality, touch of warmth, vivid resolution etc....

Problem is we bring the speakers home and place them in a myriad of rooms greatly impacting the resulting sound. Some have to place the speakers closer to a front and/or side wall than ideal. Some have rooms that cause bass boom. Others have rooms that do not allow for symmetric placement of the speakers within the space throwing off the imaging and balance. Many other sonic compromises occur because of our listening spaces/rooms. Many of us share the listening space with the living room and cannot place all manner of room treatments.

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.
Audyssey room correction is now available in many midlevel surround receivers. There’s really no high price barrier to obtain dsp room correction.
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. 



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). 



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  : )
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.
The only advice I have left is this:

Listen to the system in store with room correction. Make sure you like the room correction’s choices before you commit.

Be aware that when you commit to this you are usually committing to an entire chain of devices. A/D, DSP, DSP Software, and DACs. Very few use digital only DSP units, though they do exist.

The issue here is if you are a DAC and speaker snob (and who isn’t? :) ) you are probably going to give up your choices in sound quality to the room correction.

Personally, I use room acoustic treatments along with DSP (not room correction) based EQ in the sub and center channels only. I leave the Surround, L and R alone. I have no problem getting seamless great sounding movies and music this way.  I do sometimes think about toying with time/impulse correction, but meh. 


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.
That doesn't quite make sense, because audiophile speakers aren't designed to be used in an anechoic chamber. You don't want to eliminate all reflections.
I guess I walked into a debate between David and Bill (the ’other Bill) unwittingly. My concerns with whole system DSP (and I’ve never heard the Lyngdorf ) if that’s what’s being discussed are:

settings and adjustments- is this done entirely through electronic measurement by the device itself or do you, as the user/listener, tweak the settings to taste?
to what extent does digitizing the signal (including of an otherwise all analog source) compromise the sound?
are you limited by being unable to substitute key components if you adopt a solution that integrates processing and amplifier(s)?

Does an "add on" DSP device that allows you to integrate DSP into an otherwise conventional system fall short of the best that DSP can do, so that you cannot retain an ’unprocessed’ system if you choose to?

I was curious about the MiniDSP products a few years ago, but they seemed to involve more than I needed for simple bass management and I was reluctant to introduce anything between my line stage and main amps that could affect the sound in a negative way. I guess I’m not entirely out of the "purist" camp, though I recognize that at some level, all of this is "processed" to a degree, even in the analog domain....

A discussion of modern DSP would not be complete, IMO, without mention of DEQX. In addition (depending on model) to being able to serve as a preamp, provide remarkably transparent A/D and D/A converter functionality, extremely versatile and flexible room correction capability and equalization capability, and the ability to support subwoofers, biamping, and triamping, as far as I am aware DEQX products are unique in that they can bring any speaker that is not time coherent much closer to being so. And the great majority of speakers are not time coherent, including all speakers which have a crossover that is not first order (i.e., 6 db/octave). (Vandersteen, Thiel (at least formerly), and Green Mountain Audio are among a small handful of manufacturers of speakers which use first order crossovers).

That said, using a DEQX entails a very substantial learning curve. Also, taking full advantage of its "speaker calibration" (i.e., time coherence) function requires making close-up measurements (e.g., from a distance of 2 or 3 feet or so, depending on the size of the speaker) of the speaker’s response to test tones generated by the unit, with room reflections reduced to a bare minimum. Reducing room reflections sufficiently can mean moving the speakers to the center of the room for purposes of that measurement, or even better to outdoors. Room correction is performed subsequently, as a separate step, with the speakers in their normal positions.

I use DEQX’s top of the line HDP-5 model, and it took me several months to fully optimize its settings to my satisfaction. And that was with a relatively simple setup involving a single pair of speakers running full-range. Although I chose to do it all myself, at my own methodical pace, rather than utilizing the services of a "DEQXpert" via the Internet, who I understand can greatly speed up that process and presumably accomplish it better than many users would be able to.

For further info, and considerable additional detail on the experiences of a goodly number of members with DEQX products including me, see the following long-running thread:


-- Al
Bill, the questions and queries were not contemplative...they are direct. 

The 'more' portion was somewhat addressed by erik_squires, one of which is all the other 'pieces' in the sound reproduction chain...does room correction also know what was "intended" by those designers (power supplies, sources, recordings, cables, etc.)?...did the speaker designer know which components, etc. the customer was going to choose to build his or her system? Etc.

In other words, (what all) is room correction divining?

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.

the speaker is free to be what it was intended to be

I'm not against room correction or DSP, or other software based 'corrections.'  @erik_squires  position lines up more with where I'm at, on the topic.

My issue is with "sound as intended" and "sound as it should" which are remarkable statements, to say the least, and to this mind border on the incredible.
Remarkable statements for a remarkable product 🙂 All I can say is listen to a 2170 or a 3400 properly set up and you will get it. Simple stuff here IMHO. Plenty of rigs don’t sound that good, or as good as the designers intended because of poor speaker placement and room issues. Think of it like this. A talented chef prepares a wonderful tasting ingredient....perhaps a sauce. It tastes wonderful when used in well executed recipes, but even this spectacular tasting ingredient can be part of an awefull tasting dish when the total recipe just doesn’t work. The ingredient, while awesome, in the end did not produce its intended result....a great tasting dish. We listen to systems, not just speakers or amplifiers. The room is an ingredient. How speakers are placed is also an ingredient. Our gear ingredients. Many other ingredients. SOTA room correction helps assure several of the ingredients work well together so you are more likely to to have a successful total recipe.....a great sounding system. Room correction is your personal chef. Oh my, this last line is now coming back at me in the form of a question 🙂

Speaker builders have no doubt heard their creations in systems that did not sound as they intended. I am sure they have been mortified with the resulting sound...not as they intended. Builders intend their speakers to sound good in your home, not harsh, not dull, not poor.  That is what intend means.  Surely no designer intends a speaker to sound poor in your home? 

Ok, my brain is now tired as I tried to extract too much out of what in the end is a simple truth. I am most likely not smart enough to understand the deeper meaning of the questions. Most likely the case here. The OPs post is about DSP for dummies! I will go back to developing bacon flavors real expertise!
OP: My recommendation is to buy a calibrated microphone, a miniDSP mic goes for $100 on Amazon, and down load the free Room Eq Wizard (REW) software and measure your own room. Based on that data, you could have a more meaningful discussion about what DSP can do to improve your room/ speaker acoustics.

I’ve done the measurements and it’s a lot of fun.  You can get a miniDSP equalizer for $200 and program it with the same tools you used to measure the room.  It works as advertised. My room/ speaker set up has some SBIR issues but DSP cannot fix a null.  In the end, I didn’t use DSP.  I did some room treatment (a more general solution) and was satisfied.

I know people who design things for a living. I have not talked to many who said they were not often forced to make tradeoffs between what they desire vs what is possible given their reality. 

I am also 100% positive that while some favored systems are really very good, there are many ways to end up at a destination. One that is right for some may not be right for another no matter how much a person may want everyone to follow their lead. 
I use the MathAudioRoomEQ plugin for my music player, Foobar2000.

The good: it's free.  It works way better than not using it.

The bad: I don't know; haven't tried any of other solutions.

REW plus minidsp looks interesting, since I could use a turntable, and it would work on ALL my computer audio, not just Foobar2000.

Winter is when I typically play with audio - summer is for cycling and cameras.  Maybe this year.
I use a DSPeaker Antimode 8033 on each sub and I love the results enough to consider getting their Antimode 2.0 for full range correction.
A little late to the party here, let me add a few experiences and observations. I’ve had Dirac Live on my PC for several years across multiple amps and speakers. Every setup sounded better corrected, and every amp and speaker retained their unique sound. Otherwise I’d save a boat load of cash and run an AV receiver with Audessy as a prepro to a cheap amp and speakers.

Speakers have their own characteristic sounding drivers and cabinet harmonics around the fundamental tones being swept for calibration. Quality of crossovers or lack there of matter as well,

Whether the dsp’d sound was as intended by the manufacturer was lost on the fact that my system sounded better with correction. To Eric’s point, a well treated room is always a better starting place.

What I like about PC corrected audio is that it’s all done digitally in the PC and sent out USB. The only D/A process now occurs in the wide selection of DACs or Pre amps available to you now. No need for bundled, expensive DAC/Pre/Room Correction units. Want an R2R dac or that tube pre everyone is raving about WITH correction? - now you can. You may find yourself in this hobby upgrading sooner than expected and I never want to throw out a digitally corrected room. Stays in the computer and yes, a minimal level of computer skills is required. It’s not the easiest option and could be why I don’t see many folks with PCs operating as music servers with room correction.

I just wish there was an ethernet streaming box with quality room correction minus the compromised bundled DAC or Pre. Digital input/digital output. An excuse to move up to an Ultra Rendu.

My USB is sounding toe tapping good with the Sotm usb card, reclocking, LPS and galvanic isolation. I’m sure giving up USB room correction for ethernet streaming would be a significant step back. Same goes for MQA DACs.

If I’m missing a solution out there please respond.
Just like the title of this thread. A good one and should be a sticky :-)

Is there a product out there yet that is idiot proof or doesn't require a separate highly variable computer interphase or doesn't require downloading software?

IOW, something you can set up after a few spikesd eggnogs. Thanks for your input.

Merry Christmas 
@recluse -- if you want to experiment on a relatively low cost basis, here's an option for you.

Buy a Raspberry Pi 3B+ or 4 ($30 or $40) along with a HiFiBerry DAC+DSP Hat (under $100 and fits on the RPI). A case for the boards, a power supply and an SD card might be another $25.  The needed HiFiBerry OS system is a free download.  Finally, you'll need a measurement microphone with a USB connection; there are a number of options for $100, give or take. 

Set up the RPi/DAC card and use it as a player into a line-level input on your stereo. The HiFiBerry OS has an option where, using the measurement microphone, it will measure the frequency response of your speakers in your room.  Once done that'll show you a graph of the response and give you options to make corrections -- bass only or several broader choices. 

The OS also has the option to do custom equalizations if you have others ideas in mind. 

Obviously this is something that requires a LOT of experimentation, but it gives an effective way to investigate your DSP options without throwing down big bucks. 
dsyckx, check out my system page and you will see an advanced DSP system at work.
Erik, the best room correction systems merely create a mirror image filter to the speakers frequency response in a given room and give you the arrival time of each individual speaker. Some will also calculate the delays required to make the sound of each speaker get to the microphone at the exact same time. After that all the choices are yours. Unfortunately a large proportion of clients had no idea what to do with those choices and made a f---ing mess out of it. So manufacturers started making those decisions for people such as with DEQX and Anthem units but even with these units if you care to dog deeper you can wrestle control away from them. Most are not so inclined.
You can not just ignore the room. You still have to block early reflections and set up subwoofers correctly. The filters can only do so much. 
IMHO you can not get to the seventh level without correction but you have to do everything else with it or it is just a waste. 
Room control does not "release the speaker from the room." Nothing does that. It helps to blend them together to get to the right result along with sensible acoustic measures such as sound deadening in the right locations. It's most important function is to make the frequency response of both channels exactly identical. This is the way you get the best imaging. Next is to tailor the system frequency response to specific situations. There is not one setting that suits all. I have 14 different settings in memory which I use regularly. Some of them I have shown on my system page which you should visit if you have an interest in this.
The best room control system available today is by Trinnov. Lyngdorf's room perfect is a simplified bastardized version of the system Radomir Bozevic developed for TACT 25 years ago. It is room control for dummies. But, Lyngdorf survived and Radomir did not. The dummies far out number the digital electronics engineers. If only Radomir had come up with better instruction manuals.