[Wayne A. Pflughaupt]

System Calibration vs. Program Compensation:
Will a house curve deliver sonic bliss? ​

Perfect sound quality forevermore?
Some people have come away from forum discussions on house curves, or perhaps from reviewing my house curve article, with the impression that dialing in an appropriate curve for their room should result in all program material sounding perfect. The following is from a discussion thread here at The Shack, where people voiced disappointment with the results:

“My experience in equalizing for flat response at the listening position with pink noise was exactly like Wayne’s early experience: searing treble and AWOL bass. However, my bottom line is that the amount of HF cut you need will vary from recording to recording, and some recordings will produce correct sound in your room (and mine) with no treble attenuation. So feel free to experiment with target curves, and recognize that different recordings need different EQ. So many recordings are badly done that a fixation on ‘one right setting’ will only bring suffering upon oneself.”

“I agree with what you say but only up to a point. Consider that the TNT channel and certain shows on the SciFi channel have something major wrong with their bass. I don't think you have much choice but to have a different setting (or memory) in your Sub EQ setup. Coming up with a compromise setting that you can use for everything is most likely to result in settings that don't sound good for anything.”

Certainly, these folks are correct: Dialing in a house curve appropriate for your room will not guarantee that every recording or program will magically sound perfect. That’s an impossible goal, since the movie industry’s X curve is not nearly as rigid as one might think, and the music, TV and video game industries have no standard at all.

System calibration...
But let’s take a step back from equalizing programming and focus on the bigger picture: the system itself. Dialing in a sound reproduction system so that it sounds natural and balanced is what audio professionals call “calibrating” or “setting up” a system. They accomplish this with various response-measuring tools (and fortunately we non-pros have the awesome REW program available to us). Measurements are confirmed afterwards with program material that the technician has found to be a good representation of an accurate recording, making further adjustments at that point as needed, irrespective of what the measurements may indicate. Therefore, it should be noted – and obvious - that global calibration of the system is not the same thing as compensating for deficient program material.

In the world of home theater, rife with untrained and amateur system “calibrators,” a house curve will naturally reflect the owner’s personal tastes and expectations. For instance, we can anticipate that a basshead fresh from the world of car audio, or someone who’s used to the “boom-sizzle” of smiley-face EQ settings (from one of those 10-band equalizers that were popular in the ’80s), will expect that their home theater should sound the same. That’s not really a problem. Once the system is calibrated, even if it’s intentionally “miscalibrated” to accommodate the owner’s tastes and expectations, it becomes their personal point of reference.

...Vs. program compensation: Just say “no” to endless tweaking
At that point any program material offered up from the cable box, satellite receiver, DVD or CD player – for the most part “it is what it is.” The notion of calling up a different house curve for everything that comes down the pike - or as I’d characterize it, deliberately un-calibrating the system - is not the proper way to do things. If certain discs or TV shows have, for example, bloated midbass – fine. I assume that’s the way the director or producer wanted it to sound, right or wrong. I’m not interested in re-tuning my whole system to “unbloat” his idea of “correct.” I have the benefit of a real time analyzer connected to my system that gives a visual display of all audio-program frequency response, so when I hear something that doesn’t sound right – bloated midbass, limited low extension, screaming treble, what have you - the RTA confirms that is indeed what the program is generating. It verifies my system is calibrated correctly and is accurately reproducing what it’s being fed – a rather satisfying feeling, actually.

Certainly, if you find yourself making the same adjustments on a regular basis – e.g. always dialing up the treble a few notches – then tweaking the system a bit further is in order to finalize your settings. With a properly calibrated system, most program material should be “in the ball park” as far as sounding balanced. That’s the goal, since perfection is unobtainable. Indeed, this is the one downside to having quality electronics and good speakers all properly calibrated for the room: you will quickly find out just how bad a lot of programming really is, especially when it comes to bass.

Addressing problems with poorly-equalized program content – as noted, that’s a whole ‘nother cantaloupe separate and apart from system calibration. There’s certainly nothing inherently wrong with tweaking problematic programming, but adjustments should be general, not wholesale, and temporary – such as overall adjustments to the treble or bass if they sound excessive or deficient. If the bass sounds bloated, then bloated is what it is. But bloated bass should at least be at a balanced level in relation to the rest of the signal, not overpowering or weak.

I typically just use the receiver's tone controls or my subwoofer remote control (for level adjustment) for times like this, but it would be easy enough to dial in a pre-set curve of some type for certain problematic TV channels or shows that you frequent, if your system has the capability. But even such pre-sets should be recognized for what they are - temporary settings.

 

[Wayne A. Pflughaupt]

Reserved.

 

[olakunle.odebode]

I only came across this thread recently - and the whole vista of Room/Speaker correction using equalisation, in a lot more detail recently, especially the use of digital and software based methods to achieve this.

I had been using EQ, to "correct" somewhat for acoustic anomalies at events where I was a live audio mixing engineer.

Your post gave me so much comfort, as I absolutely agree, and my shock is that so many whom I had expected to know some of these things - such as esteemed authors of articles in some of the most respected music and audio equipment magazines, have very limited knowledge of this area. It took a lot of online research and practice on my part to come up with your conclusion.

From my experience, whenever you have arrived at a "flat" or reasonably flat frequency or perceptively flat audio reproduction at the listening position, which I now wish to call, the difference between different audio sources, whether this be tracks of music, television, or any other audio sources, becomes so much more apparent, almost like different "flavours", "textures", "preferences" by the producers of this audio.

In my case, rather than attempt to adjust EQ to improve the audio from one source, which will disbenefit another source, I have preferred to accept the truth - some audio is more "coloured" than others, some created with better equipment, and by better producers or may I say "different" producers, cos there are really no flaws in art, only choices.

But this way, now like putting on a pair of glasses, or moving close, I can see the true colors of all audio. It is a spectacular experience, and having found someone like you who was bold enough to express this publicly - at great risk of contradiction, from the many who would have - rather than test for themselves your assertion, simply reject it outright, because it was not popularly accepted wisdom, I was compelled to drop this note.

What's shocking to me is how slowly true knowledge still takes to benefit the world, you posted this about 7 years ago, and no one either saw it or bothered to respond.

I'll be the 2nd person to attest that the opinions you have expressed are so true. Room Equalisation - or whatever name others call it provides a valuable improvement to listening, for those who are willing to accept the truth.

Unfortunately it will expose things so transparently, that a lot of music will sound completely "new" like - wow is there something wrong with my correction, but over extensive listening and trying out different corrections, I have come to trust my current reference correction, as good enough to "tell" me - exactly what is going on in every audio source....

I've been on this search for a number of years, and it is such a relief to hear from someone else the same things that I also have discovered.

 

[AudiocRaver]

Wayne P's articles have been around for quite awhile and a number have benefited from them. You might call him a missionary for accurate information about target curves and best EQ results. Glad you found them. Sometimes the truth gets buried under a lot of muck and you just have to dig for it.

 

[willis7469]

Side note. The modest Wayne M's articles postings and musings have also been eye opening and helpful to many. Just think, if we could get these two Wayne's brains in one melon...


Sent from my iPhone using Tapatalk

 

[olakunle.odebode]

I found out - in a most surprising manner, a few hours after my 1st response to this this post, the following links, which establish that this whole body of knowledge has been brooding in various parts of the world, for quite a while.

http://www.stereophile.com/asweseeit/1092awsi/index.html

which I was lead to by this blog post :

http://archimago.blogspot.co.uk/2015/09/measurements-sound-room-update-digital.html

I have been a serious hobbyist in the music production world, and live audio engineering/mixing, so predominantly the magazines and online resources devoted to these topics were my primary sources. for quite while - 1985 till date. I had thought that as an avid researcher on the "professional" aspects of audio, I should have been aware of this. Yes in recent times - some products to correct audio, have been marketed to the "professional" end users e.g Genelec SAM, and others from Trinnov, JBL, Sonarworks, IK Multimedia ARC, to name a few and are getting more well known.

My big surprise is that these "correction" systems have been in even more predominant use in the non professional - home user/cinema theater arena, which I somehow never really got into, and had very little knowledge of, as I focus on stereo listening only.

In some ways, Stereophile and Wayne P represent similar ethos - making the best effort to present very credible information.

What's really unfortunate is how many of the relative newcomers - all give you this impression, when you visit their web sites, that their "technology" and "research" is unique, only available form them, and in many cases cannot explain how and why their product works, and give absolutely no credit to the pioneering work of those who went before them to pioneer and improve our knowledge/capabilities.

With the predominance of home studios - the "professionals" who are the ones who need this perfect listening the most, in their usually less than adequate smaller rooms, are the most unaware of this.

It's only in recent times that a few at the top of the industry have started to acknowledge what others have known for a very long time, but it clearly has not received anywhere near the import and impact that it should.

http://www.digido.com/articles-and-demos12/15-other-audio-articles/89-digital-room-correction.html

which fortuitously refers to this forum.

http://www.soundonsound.com/reviews/room-correction-software

Time does not permit, to list them all here, but I deduce from my research evidence of simultaneous research over decades especially in the US, Europe and Japan, in applying Digital technology to correct anomalies introduced by the room, and any speaker induced imperfections.

It has literally turned my world upside down, up until a few weeks ago, I thought I knew enough about audio - reproduction/playback, and in just a few weeks, so much of what I thought I knew has been completely overtaken, and I wonder what else is out there in this universe, that I do not know, not just in audio, but other areas of life that I thought I fully understand.

One conclusion though, without the Internet, research and communication with like minded people whom I have never met in person, that has taken me only a few months, to reach this landmark point, would probably never happen in my lifetime.

To all who have made the excellent audio knowledge and tools that I benefit from today, thanks.

My key tools have been :

1. REW - Room Equalisation Wizard - to capture the room measurements
2. Sox - for file format conversion
3. Audacity - to view files and some spectrum analysis
3. Reaper - my DAW
4. DRC - Designer - which simplified some of the generation of correction impulses in DRC.
5. DRC - managed by DRC Designer.
6. Reaper ReaVerb which is my convolution plugin.
7. VB-Audio Virtual Cable, which I use to route audio from all my Windows software -Browser/Youtube and online streaming like Spotify, into Reaper.

My audio Chain is therefore on playback

1. External Source from outside my DAW, but on my Windows PC - Browser/Youtube/Any other Audio player

2. VB Audio Cable setup as my default audio interface (receiving audio from the External Sources above).

3. Reaper receives input from VB Audio Cable

4. Reaper processes it in RealVerb as a VST plugin, RealVerb acting as a convolution plugin to load the correction impulse.

5. Reaper routes the audio to any output that I have selected in its config.

6. Internal audio in Reaper itself is also routed through ReaVerb

And contrary to what many have assumed, all of this happens with zero latency in the convolution plugin, i.e from input to output I have a reported total latency of 20 milliseconds @ 96Khz, including converter latency, (most of the 20 milliseconds is the input and output buffer, as well as any DAW buffer imposed) which means I could run audio from a source, completely outside my PC, e.g video, from a home theater system, and there would be no perceptible delay or sync issues between the video and what I hear.

Of course, at the risk of increasing system stability, I can drop this round-trip latency much further or upgrade to the newer audio interfaces which will give me as low as 8 milliseconds - total round-trip @ 96khz., or bump up to 192Khz to almost halve the time again.

The least I can do is post this in case it could solve someone else's challenges. So much is possible. Time does not permit to write up detailed steps and publish, I tried that once on another blog site and it raised more questions than answers, so until I have the time to do a good job of a step by step, guide, best to leave only the highlights here.

If the author of DRC Designer ever reads this, I would encourage them to add an option to save the configuration - inputs/measurements, target curves, custom settings, if these were used, as well as output impulses - together, so that these can be saved, and called up again. At this time, I copy the text file for the Target curve and take a snap shot when I use custom settings and store this with the input/room measurements and correction impulses - so I can correlate and recall, in case I wish to make changes.

Almost similar to how in the days before digital or automated mixing, engineers would write down all the settings on charts!

My more than 2 cents...

 

[AudiocRaver]

You have come far, Grasshopper.

My last correspondence with the author of DRC Designer was when it broke a few years ago and he kindly integrated java run time into his distribution. My guess is he has not touched it since. Both DRC and DRC Designer, although very capable (I started my RC journey with them in 2010 or so), are pretty much dormant now.

Glad to hear about your successes. And yes, without the Internet, digital audio would still be in the stone age.

Edit: Reaper, wow, you ARE ambitious! I use it extensively for audio experiments, as well as recording and mixing. Keep it up!

SoX is also a killer little program.