Testat i Autohifi Mars 2010.
A MINI-REBELLION
The world has never seen so much amplification in such a diminutive package. The new XD Series by JL Audio demonstrates that really small can also be very powerful.
By Heiko Doebber (autohifi magazine March, 2010, Germany)
JL Audio is known as a very innovative manufacturer – likely because no JL product seems to be a lightly modified standard commodity. The brainpower that the legendary US-company invests in product design is obvious in every detail. From the ultra-shallow, problem-solving TW5 woofer, to the extreme bass monster 13W7 and to the digital amplifiers of the HD series (tested in autohifi January, 2009) – JL Audio components consistently offer high tech along with smart new technologies and features. The HD amps have already shown that JL Audio is following the trend towards more and more compact amplifiers, and these have targeted the market for very sophisticated products. The brand new XD amplifiers are priced below the patrician HD amps and are currently available as 4- and 6-channel models, and as a monoblock. The 4-channel and the monoblock are dimensioned at 180 x 52 x 217 mm, while the 6-channel is somewhat wider at 260mm.
OUTSTANDING QUALITY
All XD models come in elegant cast aluminum heat sinks with removable top panels. Below these panels you will find all controls and switches for set-up. The workmanship of the heat sink is of the highest quality and the ratio of weight and size make you feel that these mini-sized amps are really massive and of higher value. Per JL Audio, the 4-channel model XD400/4 ought to generate 4 x 75 watts @ 4 and 4 x 100 watts @ 2 ohms. Our measurements resulted in 4 x 70 watts @ 4 ohms - so far so good - but then we measured a juicy 4 x 132 watts @ 2 ohms. What a mighty understatement by the Americans.
Super: the mini amp draws only 47 amperes out of the laboratory's power supply with a 2 ohm load on each channel; on the 4 ohm test it only drew 24 amperes. This restrained electrical power consumption is a result of this amplifier's advanced digital technology. For a digital full-range amp, the measured S/N ratio of 99 dB is a crowning achievement - this is an area where most other digital amps fall behind. The diminutive JL Audio includes all the most relevant features: for each of the channel pairs (1&2 and 3&4) an active crossover is available, continuously variable from 50 to 500 Hz. A small slide switch sets the operation from flat to high-pass or low-pass mode. With another two switches you can configure the signal inputs (2- or 4-channel) and the preamp output for connecting an additional amplifier (signal from CH 1&2 or summed). The next switch determines if the remote level controller works only on CH 3&4 or on all four channels. All models have the same smart connecting sockets: the cables are installed from the front of the amplifiers into the terminals and screwed from above, and then concealed by the top aluminum panel.
IN THE BATTLE OF MAXIMUM PERFORMANCE VERSUS SMALL SIZE, THE XD-AMPS ARE A COLOSSAL ACHIEVEMENT
SANE FEATURES
The features of XD600/6 six-channel are essentially identical to the XD400/4 feature set, with the exception that it lacks preamp outputs and the addition of a third channel pair. In our laboratory TESTfactory, the XD600/6 reached 6 x 67 and 6 x 123 watts, which is equal to a total output of over 730 watts – for an amplifier of this small size, this is a real achievement. With a S/N ratio of 97 dB, this amp was a little below the XD400/4's optimum value, but with a power consumption of less than 33 amperes in the 4 ohm mode, this amp is also very battery-friendly and efficient. The laboratory measurements clearly show that the XD amplifiers offer more power at 2 ohms than 4 ohms. Compared to the previously tested HD amps (autohifi January, 2009), the power drops at 12 V versus our standard 13.8 V test. Reason: the HD amps have regulated power supplies, while the XD models do not. But, considering the small size of these amps (a volume of just 2031 cubic centimeters), the XD's will serve as the new benchmark for all coming compact amplifiers.
FINE SOUND IN THE LISTENING ROOM
In the listening test the XD models wiped away all prejudices that digital full-range amps cannot sound as good as their analog counterparts. In our A/B comparison with analog amps of the same price category, the JL's convinced us with their tight and accurate sound. The bass as well as the mid-range of both XD amps sounded precise and exact. The 4-channel delivered a bit more energy during dynamic passages at high levels and was tighter in the low bass, but the difference between models was small. In the higher frequency ranges the XD siblings were equal. Both exhibited very nice and round harmonics, without compromising the dimensionality or brilliant details of the highs.
SUMMARY: The JL Audio XD400/4 and XD600/6 digital amps are 'enormously small' and finding an installation spot for them is easy. Both offer more power and sound than expected. Top-Notch!
XD400/4TOP & FLOP
+ high quality construction
+ very efficient
+ extremely compact
+ fine sound characteristics
– No Flop
Sound (37of 50 points)
Power (16 of 30 points)
Features (4 of 10 points)
Quality (8 of 10 points)
TOTAL 65 of 100 points
Category: TOP CLASS
Price/Performance: 5 of 6 stars
XD600/6 TOP & FLOP
+ very flexible
+ very efficient
+ extremely compact
+ fine sound characteristics
– No Flop
Sound (37of 50 points)
Power (18 of 30 points)
Features (3 of 10 points)
Quality (8 of 10 points)
TOTAL 66 of 100 points
Category: TOP CLASS
Price/Performance: 5 of 6 stars