I've recently had my eyes re-opened to how the mainstream consumer market has been watered down to the least common denominator as far as audio quality is concerned for consumer music. Home theater, by contrast, has managed to do a decent job, comparatively, and examining the differences between the two markets is a good way to illustrate the problem.
When the movie industry sets out to produce a movie (take James Cameron's "Avatar", for which he pioneered a completely new stereo-HD camera and projector system and then proceeded to convince movie theaters to adopt the format-- a similar journey that George Lucas took to get THX into movie theaters), they ensure that they shoot in a format that meets or exceeds what people have in their living rooms. For example, most movies in the 80s and 90s were recorded on analog large format film, which is why it can be digitally encoded to Blu-Ray as 1080p because there is enough fidelity in the film to convert it into 1080 lines of digital video. Similarly, they pay attention to encode the audio during and post- production into multi-channel high fidelity (bitrate), often lossless formats.
By contrast, the music industry takes the masters from the original recordings and puts them into a simple stereo format, like 16-bit, 48Khz PCM (pulse code modulation) encoding as the basis for Compact Disc Digital Audio, and calls it a day. Lossy formats like MP3 and AAC (which comprise the overwhelming majority of online music) are often sourced from the CD media and thus can only maintain or degrade the audio quality from there.
When you consider that many consumers are content to listen to their music on tinny computer speakers, tinny TV speakers, pathetic earbuds that ship with their MP3 players, or base-level OEM head units which use simple connection technologies (like the MP3-cassette tape interface, the analog "AUX in" stereo mini plug, or private-band FM-radio transmitters), I suppose it's reasonable to suggest that anything better is a wasted investment for most of the market.
But there are exceptions, and these exceptions really highlight where the biggest gaps really are. Take for example the multi-channel audio offered as an upgrade for certain luxury car brands. Our 2009 Mercedes Benz R-Class came with a Harmon Kardon "Logic 7" 7.1 channel surround system, which consists of a head unit that can decode DTS and Dolby Digital audio (thanks to it being the source component to drive the rear-seat entertainment system, which is DVD based and thus needs to read AC3 and DTS audio tracks for popular Disney and Dreamworks titles for the tykes). Similar systems are available from other car makers, including the Bose SurroundStage product line.
The problem is that most of the source media isn't high quality enough. Content from the iTunes store, to my knowledge, does not contain any more channels than joint-stereo (that's 5.1 channel short of the 7.1 channels Harmon Kardon provides, and 3.1 channels short of the DTS-encoded AIFF format the receiver supports), nor do any of the CDs that most people own to rip their own MP3s from. Do you think that the sound engineers who captured your favorite recording just used a single stereo microphone? (Solo a capella tracks being a notable, if rare, exception for a reasonable choice to use 2 channel stereo)
So-called "HD" and satellite radio doesn't do the trick either. HD Radio is better called Digital Radio because the audio quality often falls short of high definition. Like TV stations before them supposedly broadcasting "HD", free, advertiser-supported over-the-air broadcasters would rather partition their bandwidth into several low quality channels with the hopes of gaining listener/viewer stickiness with quantity of programming rather than quality of content.
So the only avenues to get the most from your 5.1 or 7.1 channel system is to obtain your source media from vendors and formats that support high quality, preferably lossless, multi-channel audio.
With iTunes, online MP3 vendors, Audio CD, and broadcast & satellite radio out, what's a consumer to do? The industry's answer has been "DVD Audio". Essentially, this is DVD quality audio (encoded as DTS or Dolby Digital AC3) with no accompanying video. But good luck finding it in stores, or even to listen to samples of titles recorded in this format on online stores like Amazon. (The files are encoded as DTS, and unless your computer can decode DTS, all you'll hear is static)
The good news is that there is at least one online source where the content is recorded with high fidelity audio in mind, it's marketed with high fidelity in mind, and it's sold with high fidelity in mind. That source is itrax.com
. The content is recorded at a 96Khz sampling rate (the input signal is sampled 96K/sec, but physics suggests that this is higher than is necessary, and that 2x the human hearing range, or roughly 44Khz is all people can hear). The content is encoded using 24-bit quantization (at each of those 96K samples in a second, there are 16 million discrete values the waveform can take, versus 16 bit audio with 65K values for audio CDs), a factor of 256 times better audio resolution. And while audio CDs store data in two channels, itrax uses up to 6 discrete (5 standard, plus one low-frequency response) channels (standard CDs just use two) to encode DTS tracks.
In fact, itrax tends to scale down their audio quality of their DTS tracks to lower bitrates so their albums can fit onto a standard 700MB CD-R as uncompressed AIFF/WAV formats.
After downloading some DTS tracks, I used iTunes to burn a couple DTS audio CDs for the Mercedes and they worked like a charm. The downside to itrax is that since the broad consumer market isn't requesting such content, itrax lacks mainstream audio content.
Stores like Amazon, iTunes, Borders, Barnes & Noble, and FYE would likely carry more hi fi content if consumers were buying it. Consumers would buy it if they knew the difference, and this blog entry is here to plug the gap. If you don't know if you're making the most of the equipment you've got (whether that's an iPod, a home theater receiver, or your car's head unit) hopefully this blog post will inspire you to find out, and to begin searching for media that makes the most of it.
Finally, in case someone from Sirius or any local "HD" radio channels stops on by, I'd be much more inclined to be a loyal listener if you offered content that was more compelling quality wise. I've heard many folks comment that "I watch lots more TV in HD because it's so pretty to look at". Like them, I just spent $50 on content from itrax from artists I've never even heard of (my standard monthly expenditure is substantially less, spent on artists I know well) just because "it sounds good".
P.S. A part of me wonders if the reason why the home theater experience is so good is because of who's at the top of the food chain in the respective industries. The producers, directors and executives like Spielberg, Cameron, Scorsese, and Lucas, live and breathe their craft. They're as much artists as they are technicians. I get the feeling that the guys calling the shots in the music industry are MBAs and garden variety marketing hacks, not audiophiles, audio engineers, recording artists and technical practitioners like you see in the movie industry, but I'd love to stand corrected.