EVERYONE interested in Home Theater should have a few Calibration Discs in their collection. This is true even if you intend to hire a professional to come in and set up your system for you. Professionals will bring tools and computer programs which are both expensive to buy and daunting to learn. But even though you can't fully match their professional results, you should STILL have calibration discs handy to confirm there are no silly setup errors in your system, and to check whether any problems you spot while playing real content are due to oddities in that content, as opposed to something you've overlooked in your system setup. Calibration Discs provide you with content of known "correctness" which you can use for this.
There are LOTS of different calibration discs out there at this point, and more likely to come out over the next year or so as UHD (4K) video becomes more mainstream. Some of them are pretty specialized. Some require you also have those professional tools mentioned above. Some are hard to find, or even out of print. The most sensitive test I know of to confirm that Speaker Distance Correction is happening properly, for example, is found in the Avia Pro SD-DVD multi-disc set, which is long out of print. And even in that case, this particular test was included in an add-on disc to that set, which only appeared several years after the set first shipped! Try getting your hands on THAT one!
In this post I'm going to discuss two, generally useful, Calibration Blu-ray Discs. And also, one specialized disc -- in this case an SACD disc -- to give you a flavor of what's out there if you go looking for such specialized, test content.
But first I should take a moment to explain WHY Audio and Video Calibration is such a big deal, and why you SHOULD spend the time to learn how to use tools like these, even if you'd really rather just be relaxing, watching movies or listening to music!
Let's start with Video, since that's where the most common problems are found.
The sad truth is, the Factory Default settings in just about every TV ever sold -- even the newest -- are almost always Godawful for best quality viewing! Why? Because the defaults are chosen by Marketing people with two thoughts in mind: First, we need to make our nifty new TV stand out when hung on a wall with OTHER TVs, under garish store lighting conditions. And Second, most people buying our TV are going to start out playing crappy, picture quality content on it. So we want to set defaults which will make watching such content less immediately annoying. You know -- so we don't get so many of those dreaded, Early Returns!
And so you get what have been generally dubbed the "Torch Mode" settings. These crank up Contrast (White Levels) and drop Gamma (the shape of the Black to White response curve) to boost the overall light output -- called "False Pop". Color Temperature (the tint of "white" between red and blue) is then set way too Bluish, as this also tricks the eye into seeing the image as brighter and more detailed on a casual look. Sharpness (haloing of vertical edges) is also cranked way up to add "False Detail". BUT THEN, they ALSO have to push Reds! Why? Because without that, all these other settings will make people look way too corpse-like! Forget about near-Black details as these other settings will crush the bejabbers out of them. But no matter, as people in a store can't see those anyway. Finally, turn on *ALL* the image "Enhancement" options in the TV. These rejoice in Marketing names like "Noise Reduction", "Flesh Tone Correction", "Motion Smoothing", and "Dyamic" anything. These are the tools which attempt to blur (NOT correct, because that's not possible) problems in crappy content, so they don't stand out quite so much. Then there are the settings which screw up the "geometry" of the image -- for example, cropping portions of the image on all 4 sides so you can't actually SEE what's out there!
It's actually rather sad to contemplate how many people pay good money for a new TV -- and then never ever correct all those Factory Installed Gotchas!
The situation with Audio is not nearly so dire. The default settings in most Audio/Video Receivers (AVRs) generally ARE set to produce good result. But even there, it is common to find silly setup errors which leave people listening to lower quality audio than they think they are getting.
So let's talk about the sort of tests that are available on the three Calibration discs I'm featuring in this post. Note that I am NOT going to get into details about how to USE these tests. That will likely be the subject of future posts. In addition, each disc comes with some explanatory material that can get you started.
"Spears & Munsil HD Benchmark 2nd Edition", Blu-ray, is the second edition of a very popular test disc authored by Stacey Spears and Don Munsil some years back, in collaboration with OPPO Digital -- maker of popular Blu-ray players. There's quite a lot of new stuff on this version, so you should definitely get this one instead of the original.
There are 3 types of content on this disc: Calibration charts and tests, Validation charts and tests, and Demo material.
The Demos are clips you can use to check your results with real world content. The Validation material is primarily intended for folks checking player and TV designs. Some of these tests are intended to be used in conjunction with test equipment like a signal scope or a light sensor.
But YOUR real focus will be on the Calibration tests. There's lots of good stuff in here. For example, you can use this disc to:
Confirm your geometry settings are correct so that you are seeing the entire image, and in the correct Aspect Ratio.
Adjust the Basic Levels settings on your TV: Brightness (Black levels), Contrast (White levels), Color and Tint (Color levels), and Sharpness. In addition, with a bit of learning you can also get better results for your Color Temperature and Gamma settings.
Check to make sure your settings allow you to see the maximum Dynamic Range of gray scale and colors that your TV can reproduce (within the scope of what's called "Standard Dynamic Range"). I.e., that you are not "clipping" bright Blues for example, while Greens and Reds can still get brighter (thus screwing up the color balance for the brightest objects).
Adjust the Motion settings in your TV to taste, while also seeing what sort or "artifacts" start cropping up if you crank this up too high.
Adjust for correct Audio/Video Sync (also called Lip Sync).
If you have a player and TV capable of 3D video, this disc can also be configured to play 3D content -- both specialized charts for adjusting your 3D setup, and ALSO 3D output versions of all the basic charts so you can make sure things like the Basic Levels are also adjusted correctly when viewing 3D. (Keeping in mind that your 3D-capable TV likely has a separate settings memory for the settings to use during 3D playback.)
The A/V Sync case is a perfect example of why you really want to have a calibration disc. It is NORMAL for real world movies and TV shows to have inherent sync error. There are lots of reasons for this, often dating back to the original Theatrical Release. And most of the time these inherent errors vary scene by scene.
Fortunately, these errors are usually small enough that the brain can easily "not see" them. But if you DO see a problem -- and try to adjust for it in your A/V Sync settings -- you'll find you are fighting a losing battle. It's not just that the inherent error varies scene by scene, it's also that on different movies the error may be in the opposite direction.
So if you watch movie A which has a small error in one direction -- and you attempt to correct for that error in your settings -- then playing movie B which has a small error in the OTHER direction will compound the problem! The small error in movie B plus your mistaken adjustment for movie A will likely make the combined error large enough that the brain can't "not see" it!
So the goal here is to adjust A/V Sync using content of known sync correctness. Basically what you are doing is delaying audio to compensate for the time taken to process video in your system. (Audio processing is "instantaneous" in comparison.) And then STOP. Once you've got Sync set correctly for the video processing in YOUR gear with YOUR video processing settings, you do not want to keep fiddling with it on a movie by movie basis.
For typical movies, where the inherent error is small, your brain really will "not see" those small, residual errors, as mentioned above. And in the rarer case where you find a movie with a large sync error -- such as with poorly executed audio dubbing -- you are best off just living with it. And perhaps making a note not to buy poorly authored movies in the future!
And this is where the Calibration Disc comes into play. Because, of course, the A/V Sync test on the disc is your source of "correctly" synced content.
The "AIX Records Audio Calibration Disc and HD Music Sampler", Blu-ray, was produced by AIX Records -- a studio known for its high quality music releases -- again in collaboration with OPPO Digital. The music samples on this disc come from several of the normal, AIX Records releases.
The audio calibration tracks on this disc can be used for a variety of purposes:
Adjust Volume Trim for your speakers and subwoofer (up to a 7.1 speaker configuration).
Check for properly matched wiring polarity for all of your speakers.
Confirm that Crossover processing is happening correctly and is well matched to the actual "Bass Response" or your room.
Locate objects that produce buzzes or rattles at various Bass frequencies.
Verify that both LPCM and Bitstream audio tracks are being correctly handled by your player and AVR.
Verify that your settings for both Multi-chanel and Stereo music playback are doing what you want.
The Subwoofer Crossover test on this disc is a particularly tough challenge for your setup to pass. This test sends a tone to the Front speakers (only) that sweeps up and down across the range of bass frequencies usually involved in Crossover. At the higher frequency end of that, all of the audio will be coming from your Front main speakers. At the lower frequency end of that, all of the audio will be coming from your Subwoofer. And in between you will be hearing a MIX of audio coming from both the Fronts and the Subwoofer due to the "Bass Steering" implemented by your Crossover settings.
If everything is RIGHT in your setup (Volume trims, Crossover selection, Bass Response of your room, correct Phase and distance relationship between the Subwoofers and the main speakers), that sweep tone should sound like it has CONSTANT volume across that entire range of frequencies. (Except for the very lowest bass frequencies which are more felt than heard.)
The Music Sampler tracks are also quite useful. (Even more so if you happen like the type of music included!) They cover male and female vocals, string instruments, piano, percussion and brass at a variety of volume levels. You can select whether the tracks play as Stereo or as Multi-channel.
The third disc I'll talk about in this post is "Stay In Tune with PentaTone", SACD. An SACD music disc produced by a studio which releases a lot of SACD discs. This is an example of a specialty Calibration Disc, in that the test tracks on it are specifically focussed on validating your setup for playing Multi-channel SACD music.
Like many SACD releases, this disc contains both Stereo content and Multi-channel content. Your SACD-capable player will let you select which you want to listen to. The calibration tracks I'm referring to are at the very end of the 48 tracks of Multi-channel content.
The music, and ambient sound tracks on this disc are also a treat -- again a sampling of the content this studio has released.
One of the major problems with SACD Multi-channel playback is getting the Volume trim correct for the Subwoofer. It goes back to the original specifications for SACD. To understand what's going on here, I need to get technical for a moment.
Multi-channel tracks include individual content channels for the main speakers and also a special content channel called the LFE (Low Frequency Effects) channel. In a 5.1 or 7.1 channel track, the 5 or 7 refer to the number of main speakers and the ".1" refers to the LFE channel.
Now those 5 or 7 main speaker channels are NOT limited in bass frequency. Each of them can go as low as you'd like in frequency. So why bother with the extra LFE channel? The answer is, the LFE channel is intended as a place to hold LOUD bass! If you put really LOUD bass in the main speaker channels you'd have to limit the overall volume of the channels to avoid clipping (which dramatically distorts the sound you hear).
How does LFE fix this? Well the content in the LFE channel is record -10dB down from the level of the main speaker channels. That is, there's 10dB of "headroom" built into the LFE channel so it can hold Loud bass -- and in a way that doesn't affect what's going on in the main speaker channels, which may very well have low frequency bass of their own.
During playback the LFE channel has to be "boosted" +10dB to match its level with the level coming out on the main speaker channels. In the simplest setup, this is done by cranking up the Volume knob on the Subwoofer itself -- but there are other schemes for accomplishing this required "Sub Boost".
Then along came SACD. The cunning plan for multi-channel SACD was that the "LFE" channel would NOT be relegated to the role of carrying LOUD bass. Tracks could be mixed so that any and all bass was put in there. It was no longer an LFE channel, you see. It was a SUBWOOFER channel. So the idea was the ".1" channel of 5.1 SACD tracks would be recorded at the SAME level as the main speaker channels.
Do you see where this is going? If you play an SACD disc in the same setup you use to play movies -- or any OTHER style of multi-channel music -- the Sub Boost you've configured for your LFE channel will no longer be CORRECT for the ".1" channel coming off the SACD. It will make that channel too loud!
This has caused no end of consternation since SACD discs first shipped. So much so that some studios started producing SACD discs which did not follow the rules! Those discs were authored so that the ".1" channel DID require the standardized +10dB of Sub Boost!
And other studios just threw their hands up in despair and decided to put NO content in the ".1" channel of their 5.1 channel SACD tracks! In essence they mixed 5.0 channel tracks -- with ALL the bass in the main speaker channels and only silence in the ".1" channel.
(Indeed, that's exactly what PentaTone has done with ITS SACD music collection! The music samples on this disc are offered in Stereo and in Multi-channel. But the 5.1 Multi-channel version is actually authored as 5.0. The ".1" channel is silent. However, the test tracks I describe below do indeed use the ".1" output channel.)
Meanwhile, makers of players which played a mix of disc types attempted to simplify things for their customers by automatically adjusting the ".1" channel of multi-channel SACD tracks. That is, the player would attenuate that track -10dB, so that the +10dB of Sub Boost you had built in to your setup for all your OTHER content playback would still work.
As you can imagine, then, one of the true hassles of setting up a system for SACD playback is verifying that you have Sub Boost adjusted correctly for what's going in YOUR gear and its settings.
And that's where this disc comes into play! Because tracks 43 to 48 of the multi-channel content on this SACD disc include single speaker test tones -- including a Subwoofer tone -- that you can use for validating your speaker Volume Trims and Sub Boost!
And to my knowledge, this is the ONLY SACD disc out there which has this!
So like I said, a "Specialized" Calibration Disc!
NOTE: When checking levels with this disc, be sure to use only the tones on those tracks 43 to 48 I just mentioned. There is a set of confusingly identical sounding "Channel ID" tracks earlier in the test track collection, but the Subwoofer track in THOSE is *NOT* authored according to the SACD Subwoofer level spec.
As I said up top, there are plenty of other Calibration Discs out there -- some of them highly regarded. Disney, for example has their "WOW World of Wonder", Blu-ray, which is quite popular.
The thing about ALL of these however is that they do not yet touch on the brave new world of UHD (4K) video, HDR (High Dynamic Range), and WCG (Wide Color Gamut). There ARE some discs starting to appear for this purpose, but at present they are mainly targeted at technical folks who have the sorts of professional calibration rigs I mentioned at the start of this post.
This will change as time goes on. But for now, regular Calibration Discs like the ones I've described here should DEFINITELY be a part of your collection. And it is well worth spending some quality time with them getting a handle on how to use them.
--Bob