I’m sorry to invoke a Christmas Carol, but I’m following up on the posting of the Laurence Juber track “Mosaic” that I mentioned yesterday. There is now a folder on the FTP site that contains the award-winning (this track won the “Best High-Resolution” demonstration track from the CEA back in 2002…it was called the Demmy Award) file track in three different formats.
So here’s an opportunity to get a real high-resolution file in three different formats and compare them. It’s not easy to switch instantly between the MP3, CD and HD versions but it should give you an opportunity to use a real file to evaluate the formats.
First, download the files and put them on a USB stick or solid-state drive. If you have to use a hard drive that’s okay but it does introduce another factor…the motion of a hard drive and pick ups. Then play them back through the same signal path. My suggestion would be to use Amarra because it changes sample rates automatically and therefore switching will be faster.
Use a good quality DAC into a first rate pair of headphones or amplifier and speakers. The better the playback equipment, the more likely you are to be able to perceive a difference.
Here are some suggested things to listen for:
1. MP3 – 128 kbps is the standard bitrate for most MP3 downloads including the vast majority of tracks from iTunes (although they use a different format…AAC). There is less high-end extension and therefore you should hear a graininess and lack of high frequency clarity in the MP3 version. We’re talking about very high harmonics so focus your listening on the highest sounds. They are the shiny edge to the metal sounds. When the percussion plays the wind chimes or cymbals, play close attention. The second aspect of an MP3 file is the lack of full timbral balance because “pyscho acoustic” processing removes some low level frequency throughout the spectrum. You should notice a lack “warmth” or natural character in the MP3 version.
2. CD-Audio – This one sounds very good. It was sample rate converted from the high resolution 96 kHz/24-bit track. I have no problems with this file but you might be aware of a certain lack of detail in the highest register when the metal percussion is dominant. It’s hard to put words to it without sounding like one of the irritating reviewers that we read online and in the audiophile magazines. You have to listen carefully AND for a long time to feel the difference between this format and the high-resolution version.
3. HD-Audio – This is the original mixed file without any mastering or processing. The production of this track was straight from the original stereo microphones…no eq, no artificial reverb and no dynamic processing. When LJ hits the string hard, the dynamics are there to respond. The ultrasonics contribute to the smoothness and transparency of the very high end. This is what high-resolution audio is all about.
Here’s the spectrogram of the three formats on a single graph. Take a look and take a listen. Let me know what you think. If you can include your equipment and observations this could get interesting.
Figure 1 – The spectra of “Mosaic” in MP3, CD and HD. [Click to enlarge]