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Reviews
August 1, 2004 • Vol.2 Issue 8 Page(s) 90 in print issue
Kenwood Excelon KAC-X621 Amplifier

Kenwood Excelon KAC-X621
$500
www.kenwoodusa.com

The Kenwood Excelon KAC-X621 amplifier does more than just take your car's audio system to a whole new level. Its stronger and cleaner sound is only the beginning. This amplifier's controls, flexibility, and compatibility make it an excellent addition to your car's stereo system if you're ready to get serious about car audio.

Amps normally come into the picture during the second stage of an auto sound upgrade project. After swapping out factory head units and speakers (typically a first-stage upgrade), most people look for a subwoofer and, consequently, an amplifier to power it. Kicking up the bass is all right, but don't overlook the benefits of a more powerful mid- and high-frequency audio stream, which a good amp can also provide when connected to your car's speakers. For those of us more concerned with good sound than shaking the rearview mirror, a 2-channel amp feeding high-quality speakers is the optimal next step.

Not that the Excelon KAC-X621 is lacking in power: Rated at 179 rms (root mean square) watts per channel at 4 ohms, it has enough strength for anything your ears can handle inside a vehicle. Kenwood's Power Doubler Circuitry doubles the output of both channels when driven to 2 ohms. If you bridge the channels, you get 612 watts (rms at 4 ohms). And, with a frequency range of 5Hz to 70KHz (both values well outside the human ear's range), Kenwood isn't sacrificing any of the audio spectrum.

Let's get the basics out of the way first. The Excelon KAS-X621 is compact (2.4 inches high x 17.6 inches wide x 10.4 inches deep), so it fits nicely in any well-ventilated and out-of-the-way space, even in small cars. Its connectors and controls are well-organized and accessible. We had our local pros (at AutoSounds in Lincoln, Neb.) install the unit, but the process is straightforward: Run the power cable from your car's power source to the amp, connect the amp to the head unit, and wire up the speakers. One of the Excelon line's bonus features is Kenwood's Amplifier Management System. AMS lets you configure amp settings from the dash when using a compatible head unit and control cable instead of crawling around in the trunk with a flashlight to tweak frequency or gain. The system works great and is much appreciated when you're trying to calibrate the system or adjust to different environments or sources.

If you don't have an AMS-compatible head unit, the menu system on the amp itself is easy to manipulate. Use the Menu button and the directional arrows to scroll through and configure Bass, Treble, Volume, and other options. The instructions provided in the users manual are clear and helpful in this regard, though be sure to install your unit with an eye toward accessibility of its controls and buttons. An aluminum cover protects the amp's Gain, Crossover, and other controls and is held in place by Allen-head screws; you'll need to remove the cover to adjust these settings.

We reviewed the amp with Kenwood's Excelon KDC-X579 head unit, which we covered last month. The Excelon KAC-X621's sound is powerful and clear with all sources and at all volume levels. It produces a rich audio field with a full stage at all frequencies. And, it's dead crisp when you crank up the volume. You probably get the picture. We were very impressed. You can even string several units together with S-Video cables, supplying power to additional speakers and/or subwoofers, and control them all separately from an AMS-compatible head unit. And, if you're dividing high-frequency and low-frequency duties between dedicated amps, the Excelon KAC-X621 has selectable high-pass and low-pass crossovers to set it up.

With a $500 MSRP (less than $400 street), the Excelon KAC-X621 isn't objectively cheap. But it's competitive with other amps in its class and has the extra benefits of integration and ease-of-use with a compatible system. If you spend a lot of time in your car or want to get the most out of your sound system, we recommend the Excelon KAC-X621 (either with the Excelon KDC-X579 or by itself) as a great way to kick up your car's audio a notch or two.

by Gregory Anderson