How important is (Physical / Digital) Room Correction?

[VincentH]

I recognize much of what the very experienced and well respected gentlemen posted in the discussion Hifi Vs Computer Audiophile DAC’s, about Pro-Audio companies being more agile and more experienced, and offering more value for money. This makes sense both in theory and from my (admittedly limited) experience.

 

In the same discussion various members state that in their opinion not the DAC's but the speakers are the most important factor in achieving great sound, and that it would therefore be good to spend most of your budget on them.

 

That makes sense, but I wonder if a key contributor to the sound reproduction has been forgotten here, and in what place it should come...: the room. Since this is even more OT, I decided not to put this in the "Hifi Vs Computer Audiophile DAC’s" discussion but instead start a new one on room correction. Note that there is no predefined forum category on this, so I'm posting this in the General forum.

 

Let me give a short recount of my quest for musical bliss so far, to explain where I'm coming from...

 

1) Theory. In an original post on this forum I researched which way to go and got some very good advice from forum members: see To get 24-bit/192kHz from Vista Laptop today, go the Studio gear or the Audiophile gear route?

 

2) Auditioning. Based on this I decided to go the Pro Audio route and followed up by auditioning side-by-side, in my listening room, from Vista Foobar + WASAPI (bitperfect):

• Active monitors: Adams P33 A's versus Focal Twin 6 BE's (both tri-amped MDM designs with ribbon tweeter versus Beryllium tweeter)
  
• DAC's: EMU 0404 USB (usb) versus RME FireFace 400 (firewire) versus Weiss Minerva (firewire) (the Miverva was actually demo stand-in for it's pro-audio version DAC2, there was no demo model available for that)
  

 

The Focals were consistently better, and I added the matching Focal Sub 6 later on.

 

Now on to the DAC's: I started with the EMU, it worked OK but after the first few seconds listening to the RME I knew I would never switch back. So in this case the difference between DAC's was very obvious even to a relatively inexperienced listener. The EMU is only Eur 177,- and the RME Eur 800,- so I'd say that between the lo-end and the mid-end DACs there are significant differences.

 

Next I switched to the Weiss. I had a much harder time hearing a difference, on many tracks I was not sure. I invited a friend with excellent hearing, let him listen to both RME and Weiss (he did not know prices / brands / expectations). He said that on more complex music the instrument separation on the Weiss was better. Since he did not know anything about the Weiss and this was consistent with online reviews, I at least was convinced that the Weiss was better, but that the differences depended on the type of music played, and to me were subtle to a degree that I would not actually miss it - yet. Of course all this includes the limitations of my hearing, other components and last... but not least: my listening room.

 

Which brings me to my point:

 

3) Measuring.: I read this article from Jeff Fritz at Ultra Audio about Room Acoustics, which said:

 

In building the Music Vault, I came to regard the room as the overriding determinant of the sound heard from any audio system.

Jeff invited Terry Montlick, someone with impressive credentials as a sound engineer, who said:

It’s hard to give a percentage, but most of what we hear in reproduced sound is the room.

...

To me, it’s quite obvious: The listening room should be treated as the primary component in an audio system

 

This rang true with various statements by pro audio people, which I encountered earlier on in my DAC / Monitor research, that went something like "device X is a huge improvement over device Y, but if your room is not treated, don't bother because you won't be able to hear any difference".

 

Now I was getting worried... didn't I hear the true quality of the Weiss due to a bad room?

 

So to validate this I bought a fairly good measurement microphone (Audix TR 40), connected it to the RME (which has excellent phantom powered microphone preamps and A/D), and measured my room frequency response with various DRC software.

 

The measurement results were absolutely shocking. A frequency response nowhere near flat, or even smooth, with large-scale humps and bumps and small but high up/down spikes all along, and even differences on where some humps & bumps are in the left & right channels.

 

Here is a measurement taken with AudioLense, note this is without the sub (click image to see full version):

 

So now I'm left with the question: how important is the room in the overall system? And should I try to correct the entire measurement or just go with my ears? Options for physical room correction are limited, so I'm also considering digital room correction. At least to try that and see what my ears (are able to) say... although I have a bad feeling about doing DRC modifications to the bits, someone described this as 'pre-mangling the sound to attempt compensation for even more mangling downstream by the room'.

 

So what is the opinion amongst you experienced forum members on the importance of physical and/or digital room correction? And should you correct measurements (frequency response) or just use your ears? What does an acceptable frequency response look like?

 

Thx for any insights,

 

VincentH

 

[Purite Audio]

Vincent interesting piece, the room makes a huge difference absolutely no question , I have listened in over damped rooms and the sound is terrible, flat and lifeless, perhaps try eq just the bass to begin with, bookcases, pictures/ paintings, and just the normal furnishings ( rugs curtains sofa ) can really help a bare room. Will your post the results of your experiments? Keith.

 

[Ashley James]

Most domestic listening environments are usually perfectly satisfactory for listening to hi fi in because, without realising it, most of us unwittingly "treat them" by filling them with furniture, carpets curtains and soft furnishings until they are pleasant to sit in and relax and talk in. If people do have acoustic problems it's usually bass related. They may have a boom or no bass, but otherwise rooms do sound different, but just as we adjust to live with hi fi that isn't always as good as we think it is, we also able to "tune out" our room acoustics unless the problem is a serious one.

 

In my experience, shops and Industrial premises often do have acoustic problems because they are built differently to homes.

 

However no acoustic problem can be resolved by digital or any other form of equalisation, despite devices periodically appearing on the market that claim to do so. This is because we rely on the first arrival from the loudspeakers to make critical judgements of sound quality and to hear detail in our music. If we alter this "first arrival" to make the secondary room reflections tolerable, we'll have spoilt the important bit. Even raising or lowering Bass output can have issues.

 

Some years ago before some sectors of the hi fi Industry took a trip to La La Land there were IEC standards that defined room acoustics in different parts of the world to help reviewers make sure they reviewed somewhere similar and so that designers could make sure their listening rooms complied. Basically all they did was specify a likely number of doors and windows, likely number of solid and partitioned walls and the likely RT time. Usually reckoned to be 0.4 - 0.7 seconds. It needs to be uniform with frequency.

 

Therefore I'd advise caution when comparing bits of equipment in strange acoustics until you've had time to adjust and I'd advise against worrying about your own room unless nothing sounds right in it.

 

Ash

 

[VincentH]

Hi Keith, I updated my post with a screenshot of a frequency response measurement (without the sub). How bad is it?

 

[VincentH]

Thx Ashley for the quick feedback, that is reassuring.

 

During my DRC research I read a bit about about first arrival in the explanation on psychoacoustics in this presentation about Windows Vista's built-in DRC implementation (warning 50+ slides with lots of facts), so the advice not to mess with that rings true to me.

 

I only have a few audible room related issues:

 

1) Some bass notes seem louder than others, e.g. when a ascending/descending series of notes is played on a bass guitar.

 

2) This is a really annoying one: at some bass frequencies some elements of my room start to make irritating vibration noises, e.g. the window or a wardrobe door. I'm not playing excessively loud, so this may be some sort of room resonance frequency?

 

What would be a good strategy to address this? Just make sure nothing can vibrate?

 

Thanks, Vincent

 

[audiozorro]

I agree with Ashley 100%, most domestic listening environments are usually perfectly satisfactory for listening to hi-fi. Exceptions to this would be relatively empty new construction houses that often have plenty of reflective surfaces, hardwood floors, glass windows, mirrors, little furniture and no carpeting.

 

Speaker selection, setup and placement are much more critical. Pretty decent recommendations for speaker setup and placement can be found here - http://frankdoris.com/writing/tas/setup.htm.

 

Passive treatment is generally the superior method for correcting room deficiencies. Here is another post to add to what Ashley has to say - http://www.audioasylum.com/audio/speakers/messages/27/277321.html.

 

Maybe someday someone will sell us a pill we can swallow to adjust our hearing to correct for room nasties.

 

 

 

 

[tfarney]

This may be where Ashley and I disagree. I suspect there are many systems costing tens of thousands of dollars that are rendered horrid by the rooms they're played in. Not that it's difficult to make a room sound ok, just that it's often not done. When I see a scene like this, I cringe:

 

 

 

...granted, I can't see what's behind the camera's lens, something a bit less reflective than what is pictured, I hope, but what I can see is a nightmare: glass everywhere, closed to the right and open to the left, tile floors with the thinnest of rugs where they'll do the least good. It's downright scary. You'd think that if someone had this kind of money to invest in gear, they would be able to put it in a room with decent floor coverings, walls on both sides, and something soft at each point of reflection. Bass traps? Not necessary most of the time, but good lord, something needs to be trapped in this hyperechoic chamber.

 

If you're listening room looks like this you don't have a clue what your system sounds like. You'd be better off listening to a vintage Kenwood and a pair of old JBLs in a decent space. If you don't have room for a decent listening space, go nearfield. Put it on your desktop. It will cost a lot less and it will sound better. Desktop monitors and a sub won't produce the scale of full range floor-standers of course. Close your eyes. Imagine you're in the first row of the balcony in a concert hall instead of front row in a hockey rink.

 

 

Tim

 

 

 

[VincentH]

Thx Tim, actually the shape and dimensions of the room already forced me to go nearfield; the Focals are in an equidistant triangle of 1.5 meter with my main listening position. The Focals are explicitly designed for nearfield use (1-3 meters from listener), and allow for placement close to the wall due to 2 front-mounted bass ports each. I added the sub for low extension.

 

Thx audiozorro for the links, so far I just did: get as close to an equidistant triangle as possible, keep the tweeters at ear height and point them each straight to the nearest ear. I also modified the phase of the sub to blend optimal with the left and right speakers. But these links give some additional pointers.

 

 

[wappinghigh]

I'm not a dealer/owner but have thought about this solution for a long time.

DEQX and legend acoustics. see www.deqx.com and legendspeakers.com.au

Great Australian companies. I think there are dealers in Northern Hemisphere.

 

AB

 

[mpmct]

Lots of in-depth information here under the "Concepts" heading

in left column part-way down the page. Much of it echoes

what Ashley and Tim have already written ...

 

http://www.linkwitzlab.com/

 

( Always consider the source though.

Linkwitz uses Radio Shack RCA cables,

pro audio speaker wire, and a decidedly un-sexy

$1995 12-channel amp. So what does he know? ;-) )

 

 

 

 

 

 

 

 

 

 

[Steelman]

Hi Vincent:

 

I find the room is a very important part of the sound equation. Perhaps you and others from the group might find my experience over the past year of some use. A year ago I purchased a top-end subwoofer and could not get it to integrate into my system properly.

 

While looking for solutions, I bumped into a great forum at www.hometheatershack.com. The (free) REWsoftware and forum helped me to best place both my speakers and subwoofer, and properly set levels without using equalization.

 

Using frequency charts from REW, I tried using a Behringer DEQ2496 equalizer/ DAC for 6 months and found:

 

- In the end, proper placement/gain/cutoff of speakers and subwoofer took care of most subwoofer equalization and integration (REW software and my ears helped there!)

 

- Lots of debate on the merits of equalization, as measurements and adjustments are only valid at the microphone measuring point. Some argue that the large size of low frequencies make equalization effective only below 100hz or so and entirely useless at midrange and higher frequencies. Others argue that room treatments work better than equalization, etc etc etc.

 

- In any case you should consider breaking your measurements into two images (one below 200hz and one full frequency), as it is tough to see what is really happening at critical low frequencies; you can post your images on the REW site and the folks will provide you some interesting feedback

 

- Nearly flat frequency response generally sounds dead, especially at lower volumes (try it!). You will likely need to consider some type of "house curve"/bass boost. Like it or else, all equipment (speakers, preamps, amps, etc) comes with some type of (intentional or unintentional) factory equalization

 

- Unfortunately, from a practical perspective your frequency measurements are valid at one listening volume, thanks in part to The Fletcher-Munson Effect (in a nutshell, due to the design of our hearing system, as you lower volume you will need to progressively boost lower frequencies). Boston Acoustics has filed a patent regarding dynamic EQ that makes interesting reading on this subject (you could program a dynamic EQ into the DEQ2496)

 

- The DEQ has a sophisticated auto EQ feature. At one listening point in the room, EQ made a significant difference across all frequencies with my Monitor Audio RS6 speakers (low dispersion, small sweet spot); music came alive. The DEQ did not do much for my new high dispersion speakers beyond help me figure out integration. I used placement for the sub

 

- The DEQ was fun and helped me set up/integrate my speakers and sub but the DEQ introduced a slightly veiled sound in my system (due either to the DEQ itself or my cheap cables, I am not sure) so I sold it in my "less is more" mode

 

In the end my speakers and sub now sound great together and are well integrated, but I no longer use any equalization beyond placement (and the sub's volume switch and 25hz built in EQ dial)

 

I wonder if others are using the DEQ as a DAC as it costs only about $300 and has a lot of great features, including auto EQ. Is it transparent in your system? Do good cables help? Now that I think about it, this unit is priced very competitively!

 

Best,

 

S

 

 

 

[MontyW]

Tim,

 

I'm with you on this one! In the past I have spent what many would consider an obscene amount of $$'s on hi-fi - cables, amps and sources costing thousands and at no point did I bother with room treatments. I fanatically aligned speakers, dressed cables, even worried about where pieces of equipment should sit on a rack to get the best sound and where to place plotted plants and rugs!!!!

 

I was then introduced to pro kit and at the same time acoustically treating a room. My listening room has bass traps, absorbers and diffusers all discreetly matching the decor! Treating my listening space has been by far the most effective way of getting the best sound - I would recommend everyone look into this fascinating subject - it will be the best upgrade you probably make!

 

Monty

 

[roomandspeaker]

- You may equalize your speakers. Even Best of The Best speakers can still be improved with modern Speaker EQ technologies

- You may improve your room. Fully acoustically treated room is still has issues, solvable by various Room Correction technologies.

- Active Speaker and Room correction may... yeah, save your money

- Technology testing will not cost you a penny - don't trust promoters, create your own opinion

 

 

[audiozorro]

Electronic room correction systems work best where conventional absorption treatments work worst. This link provides some interesting reading of how to improve your room.

 

http://www.stereotimes.com/ambiophonicsch5.shtml

 

 

 

[Fuel]

This is a pretty complex subject. I have spent the last year or so educating myself on room acoustics. As mentioned earlier you definitely need to split the frequency range into two parts:

 

Under 300hz or thereabouts is where room behavior is dominated by resonances. These resonances are normally termed room modes.

Above 300hz is where room behavior is dominated by reflection.

 

Under 300hz you have a limited set of 'controls': move the listener, move the loudspeaker, equalize, add big bass traps.

 

Measuring the room response is only the first step, the next is to learn how to interpret the data. Here you have two options if you want to do a good job. First, teach yourself. Second, employ an expert.

 

As a simple starting point to demonstrate the effect of the 'move the loudspeaker' control do the following:

- measure the response at the listening position

- move the mic 6" back, measure again

- repeat movement 6" back and measure another three times

- move the mic 6" forward from the listening position

- repeat movement 6" forward and measure another three times

- look at the graphs (you should be using 1/3rd octave smoothing). What you should see visually is that some locations have smoother traces than others - et voila - demonstrated!

 

[MontyW]

5 words... Super Chunk Corner Bass Traps :-) best thing ever in my room - cheap to make yourself and the best ever upgrade I've ever made! Great for under 300Hz control.

 

I have got quite obsessive about measuring room acoustics with Fuzz Measure and understanding a room response is only the first step.

 

I ended up approaching a local University that runs degree courses in acoustics etc... and an under grad came along for a few $$/££ and suggested how to deal with my room. As I've mentioned previously - room treatments have been the best investment I've made.

 

MW

 

[WoodsDweller]

Do you have any online links for reading up on room treatments? Or good google-able phrases?

 

[MontyW]

I find this forum very helpful:

 

http://forum.studiotips.com

 

 

 

 

[Mister Wednesday]

VincentH,

 

I'm clearly on the side of the folks who are advocating learning how to acouatically integrate your speakers into the existing environment of your room as the first method of choice. My own personal experience of this has proven to me to be the most cost effective means of obtaining a large scale improvement in the quality of the sound being reproduced by my audio system. Cost effective as in - it's free (apart from your own time and efforts)!

 

Over the years three articles/videos I've used in helping me learn this method can be viewed on the Web at:

 

http://stereophile.com/floorloudspeakers/147/index2.html

 

http://www.audioholics.com/news/trade-show-coverage/videos/building-bass-traps-ready-acoustics

 

http://www.audioholics.com/news/trade-show-coverage/videos/thx-managing-bass-modes

 

The first is a text article which i found when it was first released back in 1995 and the second and third are videos of approximately 20 minutes each which were released in the last year or two. The last two deal specifically with managing the low frequency spectrum.

 

I've used the techniques in all three in combination to learn how to acoustically tune my speakers to my room and the results have been fabulous (I'm currently using a pair of Linn Akurate 242s each of which is powered by its own Linn 5-way Aktivated 5100 amplifier but the system has also worked just as well with previous speaker/amplifier systems I've had).

 

One added benefit you may find is that by cleaning up the low frequency spectrum of your audio system/room is that it also then cleans up the midrange and high frequency spectrum resulting in a improvement over the entire frequency spectrum.

 

Good luck with your own speaker/room tuning efforts.

 

Regards,

 

Mr. Wednesday

 

[RayW]

VincentH,

 

Room correction is what got me interested in computer audio (in addition to hi-res). Before getting into how to do it, I would like to offer my opinion that electronic room correction can make a significant improvement, even with high-end speakers and electronics and some physical room correction (in my case, absorber panels made of fiberglass house insulation to reduce reflections from the side walls).

 

I wanted to experiment with room correction without investing thousands of $ in hardware. I read various papers published by the Audio Engineering Society and in Stereophile and The Absolute Sound and settled on the following approach: Measure the frequency response at the listening position and also at several other random positions. Do this separately for left and right speakers, and don't go higher than about 3 kHz. If there are significant peaks at the listening position, attenuate them. If there are dips at the listening position, only boost them if the dip appears at all the other mic positions.

 

To do this, I used the classic parametric equalizer approach. Each section of a parametric equalizer has 3 parameters: center frequency, Q (i.e., bandwidth), and gain/attenuation. Rather than buy a hardware parametric equalizer, I used Adobe Audition digital audio workstation software that I already used in my amateur recording endeavours. Audition has a parametric equalizer in its effects menu. After several iterations, I found a group of settings that sounded good to me.

 

At first, I would rip a CD to the computer, equalize it and burn it to another CD. This is not a good way to do it because when equalizing, the sample word length increases beyond 16 bits, so one has to round it down to 16 bits again to burn another CD, adding more quantization noise. The preferred approach is to write the equalized audio to hard drive at 24 bits and play that through the DAC.

 

RayW

 

 

[robjob]

Personally, I believe that electronic room treatment is not a viable method of correction. When we strive to have as unfettered a signal path as possible, it seem counterproductive to use anything electronic. I'm all for Tube Traps and Sonex!

 

[The Computer Audiophile]

Thanks for all the details Ray. I listened to a Lyngdorf system at CES and was amazed. We all know the cost of this system was very high unfortunately. But, at RMAF last year I saw a great system where the listener could make all kinds of adjustments on the music server running on Windows XP. There are some good things to come in this area.

 

[The Computer Audiophile]

Hi robjob - I know this may sound contradictory to my previous statement, but most of the time I am in your camp. It just seems "wrong" to me to be changing things with electronics, but at the same time if we are after the absolute sound it really shouldn't matter how we achieve it. This is a tough one.

 

[roomandspeaker]

RayW,

 

Try some kind of automated equalization. It may give you much better results than parametric EQ playing. How many bands your parametric EQ has? Automated FIR-filter based solutions has thousands

 

And for not spending $,

 

- There are open-source (thus free) DRC-FIR software solution for Room Correction

- Try free demo of various technologies before your create your own opinion. Some (most honest of them ) Room Correction and Speaker EQ companies provide software-based demo versions of their solutions for free downloading

 

 

[MontyW]

I have a friend who uses this:

 

http://www.ikmultimedia.com/arc/features/

 

I have no idea how good it is... he raves about it, but I cannot get to listen as I'm in the UK and he's in Oz!

 

It looks rather amazing stuff, but quite expensive.

 

Monty