I'm sure that I've missed a feature or two, but the big news, and the primary reason for this Web exclusive review, is the Z919's MP3 capability. If you're reading this review, you obviously have a computer and Internet access. If your computer also happens to have a CD recorder, you're only a bit of surfing and burning away from creating your own custom CDs that will play on the Z919. Of course, a lot of the computer savvy types have been burning their own CDs for years using .wav and .aif files, but at this point, the number and variety of MP3 files available on the 'Net is staggering. Add that to the fact that an MP3 file takes up about a tenth of the space of the regular audio file formats, and you have the type of at-your-fingertips music shopping that big record companies used to dream about.

Performance
Performance from the Z919's preamp outputs was about middle of the road from a specification standpoint. We'll almost always wish for more output voltage and lower output impedance, but the Z919's outputs will prove adequate in all but the most hostile environments.

The internal amps deserve a little attention on a couple of points. To begin with, Signal-to-Noise measured -93 dB, a few dB better than the average head unit amp. Secondly, Kenwood seems to have taken a shot at a real power rating. The old 45 watts x 4 pops up everywhere, but a little spec sheet digging reveals a full bandwidth power rating of 22 watts x 4 at less than 1 percent THD. Our measurements show about 17 watts x 4 at 1 kHz, so the rating still seems a shade optimistic. However, in the overall picture, I'm inclined to dole out an A for the effort and let the 5-watt difference slide. (Ed- Kenwood reports that the head unit's interal amps were rated at the industry standard one channel at maximum output.)

On the MP3 side, things can be a bit more difficult to quantify. The easiest thing to attach numbers to is the tremendous data reduction that the format offers. My 160+ meg head unit tester CD was reduced to a measly 17.5 megs. A single CD-ROM that can hold more music than the average CD changer can be an awfully appealing idea - as long as the compression scheme leaves your audio intact. Even if you can squeeze 100 gigabytes onto the head of a pin, I'm not buying if the audio quality doesn't match the uncompressed version of the data. The audio CD is way too cool a format as it is to muck around compromising audio quality for data storage. And as you'll see, the Z919 does a damn good job dealing with this compression scheme.

From a specification standpoint, the problem that seems to arise is that different MP3 encoders produce different results on test signals. I ran our head unit tester CD through several encoding programs that are available on the Internet and tried to measure the resulting output from the Z919. The results ranged from poor to meaningless; In some cases the test signal was so mangled that achieving a stable, repeatable measurement was next to impossible.

The big catch here is that MP3's data compression algorithm is based on human perception. Simply put, all the data that gets scrapped is stuff that you wouldn't have heard anyway. I guess this might explain some of the weird test results. If the algorithm is truly based on perception, then the only sensible testing approach dictates listening to the thing. That's right: a heads-up A/B test on our reference loudspeakers between a CD player and the Z919 with an MP3 CD-ROM. For this test, I used my favorite three tracks from the IASCA Competition CD, converted to MP3 through the encoder that did the worst job of the bunch on our head unit tester CD. This test was not double or even single blind, the switch was in my hand so I knew which format was playing at any time. I'll have to admit that despite my better efforts, there was never a comparison in which I even thought that I could tell the difference between the two. I'll also have to admit that if I read that last line in a review of a 10:1 audio compression scheme, I'd probably say that the dude who said it is full of it. However, my defense stands as such: I am perhaps more familiar with this music than my own mother, and the A/B was done on reference studio monitors that I listen to every single day. Furthermore, I spent way too many years doing A/B comparisons for quality control in a cassette and CD manufacturing plant.

To sum it up, what we have here is one mighty fine compression algorithm. It's good to see that Kenwood will be among the first in 12-volt audio to utilize it.

User Evaluation
The Z919's user interface is heavy on both multi-level menus and display flash. Volume is controlled with a large, driver's side rocker switch. A finger-sized joystick that controls most of the deck's functions dominates the other side of the faceplate. The Z919's interface does get two big innovation bonus points. First off, this unit features a Play/Pause button. Practically every professional and home CD player ever built offers this relatively simple function but for some reason, it's a rarity in car audio. It may seem like an inconsequential gripe, but there are times that you just want to pause, not mute or attenuate or some other foolishness. Secondly, that little joystick thingy has potential. There's usually a lot of button pushing involved in setting up a deck with this many menus. The mini-joystick on the Z919 provides standard left/right/up/down menu select functions in a single control. While it could stand to be about twice as big with a little stiffer actuation, this method of control beats the typical overlapping rocker switches hands down. It's a lot like video game controllers. Remember when you bought that first aftermarket controller for your Nintendo/PlayStation/Whatever? Yep, makes you wonder why you did it the hard way for so long.