16 December 2009|
|CERWIN VEGA MOBILE Stealth 440.4|
The “dedicated to 12 volt” group of folks at Cerwin-Vega Mobile recently dropped off a new toy for me to have a look at. When the name Cerwin-Vega comes up, most of us think huge monster woofers, and multi kilowatt amplifiers, so what they brought me came as a surprise. The amplifier that company president and certified car nut Mike Morris handed me was, in a word, small. Not exactly what I expected from a company that has a reputation for being loud, proud and in your face.
Mr. Morris informed me that this was a new amplifier from their soon to be released Stealth Series of amplifiers, and would be joined in the lineup by a 220 watt, two channel model and a 500 watt monoblock. He went on to explain that while the company’s philosophy hasn’t changed, the expectations and requirements of the average customer have, and the Stealth Series of products are meant to fit the needs of the modern enthusiast by reducing size without compromising the performance. To accomplish this, the Stealth amplifiers utilize the very latest in full range Class D technology. But, before the amps could be released, they had to undergo extensive and time consuming tweaking and listening tests before they were considered good enough to earn the Cerwin-Vega Mobile badge.
The amplifier I got for evaluation is the new four channel Stealth 440.4, and it’s rated at 65 x 4 at 4 ohms, or 110 x 4 at 2 ohms. It has fully independent front and rear crossovers, and bridgeable stereo channels, so it could readily be used to drive a subwoofer system and a pair of components. Bridged power is rated at 220 watts at 4 ohms.
In a departure from their other products, this amplifier does indeed use full range Class D as its topology. Because of the high power efficiency of the Class D design, the amplifier can have a much smaller heatsink for a given amount of power. And this amp is indeed small, measuring 10.5” long (including terminals) by 7” wide and only 1.75” tall. On one end of the amplifier you’ll find the power and speaker connections. These are fully insulated set screw type designs, with 3.0 and 2.5mm hex head set screws. The power connectors will accommodate 4 gauge cables, and you can run up to 8 gauge speaker cables. A pair of 20A ATC style fuses plug into chassis mounted sockets. The other end of the amplifier is all about signal connection and control. The RCA connectors are rugged looking nickel plated panel mounts, and they’re color coded for quick Left/Right identification. Gain is adjusted using a single pot for each pair of channels. The crossover section is identical for front and rear channels, and includes separate pots for high pass and low pass, each with an adjustment range from 50 to 250Hz. Bass equalization is included for all four channels, with the “Vega Bass” control adjustable from 0 to +12dB of boost at 45Hz. A small blue power LED rounds out the features on this end of the amp. When he brought the amplifier to me, Mr. Morris mentioned that part of the “tweaking” process was ensuring that the gain pots tracked evenly left to right at all positions, and that the crossover filters were indeed true 12dB Butterworth alignments.
Read on for Results
I connected the diminutive Stealth amp into my reference system, and drove my subwoofer with the rear channels and my reference speakers with the fronts. I like to use this test configuration on four channel amps because it will usually show any weaknesses in the amplifiers power supply. When an amp with a single power supply for all four channels is tested like this and asked to deliver high current to the woofer load, if its internal power supply isn’t stout enough it can cause audible distortion in the front channels when the bass hits. After getting the crossovers set to 50Hz high pass on the front channels, and 80Hz low pass on the bridged rears,
I sat down to do some listening.
Given the small footprint and relatively light weight (it only weighs about 4.5 pounds) my expectations were only, shall we say, moderate. Beginning with an audiophile recording of some of Manhattan Transfers biggest hits, I was pleased with the musicality and natural sound produced by the Stealth 440.4. Some full range Class D amplifiers I have auditioned have tended to add a bit of “bite” or harshness to horn sections, and occasionally they tend to be a bit sibilant especially with female vocals, and cymbals. None of that was found in the Cerwin-Vega Mobile amp, which added some credence to Mr. Morris’ comments about the tweaking they’d done. Moving on to some rock tunes from Rush, Deep Purple, Pink Floyd and Supertramp, I noted the amps ability to produce tight, controlled bass while still providing a nice articulate top end from the front channels. Pushing the volume higher, I eventually reached the amplifiers limits, but at volume levels much greater than I had expected when I began testing. The general sonic performance of the amp was good, with a level of transparency generally uncommon to the topology. I drove the amp pretty hard on all kinds of music for a couple of hours and the heatsink was barely warm to the touch, indicating the amp did indeed have exceptional efficiency. My only minor niggle was the incredibly bright blue power LED. It’s so bright, it’s almost distracting, but that will be of no consequence when the amp is in your trunk!
After the listening was concluded, the amp was moved into the electronics lab and its performance data carefully measured. The amplifier either met or exceeded all of the specifications provided in the owner’s manual. As it turned out, I was right about the amp being very efficient. Where a conventional 4 channel Class AB amplifier will struggle to be even 25% efficient at 10 watts of power per channel, the Stealth 440.4 was a very impressive 62%! And full power efficiency was good too, at 78% when driven into 4 ohms. The amp is quiet too, with a signal to noise ratio of over -78dBA at 2 volts of output, or over 97dBA referenced to full power.
Frequency response was flat as well, within 1.0dB from 20Hz to over 20kHz. And just for giggles I checked on the left to right gain tracking as well as the crossover slopes Mr. Morris had mentioned… they had indeed paid attention to it. The difference between left and right channels was within an inaudible 0.5dB at any gain setting, and the crossovers were indeed true -12dB/Oct filters.
CONCLUSIONThere was a time when I regarded the Cerwin-Vega Mobile products as sort of “brute-force” type of gear, which definitely has a place with a lot of enthusiasts. But with the advent of this new Stealth series, the company has proven they are capable of turning out some really high tech, good sounding products as well. If you’ve been thinking about a small footprint amplifier that can be hidden away easily, draws very little current, and sounds good, find a Cerwin-Vega Mobile dealer, and check out these new Stealth amplifiers. www.cerwinvegamobile.com