Apogee DAX Crossover Reviewed

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Apogee DAX Crossover Reviewed

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Two types of add-ons are immune to the antipathy caused by such 'evils' as graphic equalizers or click suppressors. Most diehards will forgive/approve of dedicated extras of any type because they can be regarded as extensions of the basic components rather than as sonic intruders. The other 'okay' black box is the more sophisticated, usually external crossover system which allows the user to bi-amplify his or her speakers. As the latter most often tends to be the former, you can assume that most hi-fi casualties approve of dedicated crossover systems with even greater vigour than they'd show for 'universal' crossovers.

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After a flurry of activity a decade ago, when 'active' and 'bi-amping' were hot buzzwords, the hi-fi community reverted to the simpler, less costly path of conventional or single-amplifier
operation, partly because of a growth in popularity for bi-wiring. Virtually a halfway house between the amp-per-driver luxury of bi-amplification and the mundane operation of conventional wiring, bi-wiring swept the industry in the best trickle-down manner; it's now found on quite inexpensive two-way box speakers. Among the champions of bi-wiring was Apogee, whose complex full-range ribbon systems benefitted immeasurably from the technique. It also served as a respectable compromise for Apogee owners who couldn't afford a second high-current amplifier and outboard crossover for true bi-amplification.

Although a number of companies, like Audio Research and Krell, produce active outboard crossovers of a universal nature, the design team at Apogee accepted the premise that the best crossover is dedicated to the speaker with which it will be used. Even the easy-to-access specifications of crossover points and slopes will not guarantee a perfect match, and simply setting a universal active crossover network to suit a speaker with, for example, a 6dB per octave slope at 2kHz won't necessarily result in the ideal pairing. Apogee felt that good as some of the currently available crossovers may be, they cannot optimize a system unless they've been designed specifically for that system.

In addition to offering attenuation of up to 6dB in 1dB steps for the woofer and the mid/tweeter, the company's DAX (Dedicated Active Crossover) allows the user to adjust the balance between woofer and mid/tweeter in 0.2dB steps and to adjust the 'rake angle', a sort of 'hinge' in the tonal balance which tips the midrange above 1kHz in +/-0.5dB steps at around 5kHz. The DAX also provides facilities to match the crossover to the amplifiers for input impedance loading, gain characteristics (for using different amplifiers top and bottom) and for using single-ended or balanced operation. Because of the way the various DAX controls interact, the unit can vary the group delay, important when sculpturing the gain vs. phase relationship -- and one aspect of DAX-equipped Apogees is near-perfect phase response.

By addressing both the requirements of only three specific loudspeakers (you order your DAX preset for Caliper Signature, Duetta Signature or Diva) and allowing for matching to any amplifier, the DAX provides what amounts to total control for biamplifying their speakers. This in turn enables the listener to tailor the sound for both the electronics and the listening environment, beyond the obvious tweaking one can perform by speaker positioning, cable selection and wholesale changes of hardware. In the case of the Diva, the DAX takes over from the passive box with its four toggles for boost or attenuation at four frequencies, but the switch for the tweeter on the passive box remains operable. This is because the DAX is a two-way crossover while the Diva is a three-way system. The DAX sees the tweeter and midrange as one section; the toggle on the passive box allows the user to cut or boost the tweeter by 2dB in addition to shaping the operation via the DAX.

The Diva's passive box therefore takes on a different role and no less than three-and-a-half pages of the owner's manual deal with converting it for use between the DAX and the Diva. You don't have to worry about this because your dealer will undertake the conversion, which involves replacement parts supplied with the DAX and the bypassing of much of the passive enclosure's innards; remember, the bulk of its functions are now controlled by the DAX. Still, if you enjoy spending a couple of hours inside a nest of wires, be my guest. With the Duetta, instructions are also supplied for user conversion, but the Caliper must be modified by
the dealer.

Speaker conversion aside, the actual installation is a doddle if you've ordered your DAX correctly. I asked for a version set up for using single-ended amplifiers, the same top and bottom (two Aragon 4004s), but even if I decide to change, the manual covers the range of adjustments which are accessed via dip switches inside the DAX. If you want to mix amplifiers, you'll have to know the gain characteristics, while choosing between balanced and single-ended operation merely involves flicking the toggles to the left or the right. As for input impedance matching, the DAX arrives in standard form with 80k ohms preset for single-ended operation or 10k ohms for balanced. Four other values are available for either mode. (See specifications below.)

The DAX slips into the system just where you'd expect it to, between the preamplifier and the power amps. I ran the Audio Research SP-9 into the DAX and the DAX into the Aragons via
Master Link cables, with Lieder speaker leads connecting the amplifiers to the modified passive boxes. The gold RCA sockets on the back of the DAX are clearly marked, the rear split into left and right halves, so feeding the four signals from the DAX is no more confusing than wiring up a conventional stereo set-up.

The DAX itself is one of the most attractive pieces of high-tech hardware I've ever seen. Apogee has come up with a satin black finish which screams of luxury, visual confirmation that this is one high-priced goodie. The fascia is split into three sections, the left and right thirds containing four rotary controls each while the centre consists of what might be the most useful
display yet to grace a hi-fi component. Left-to-right, the groups of knobs include woofer attenuation, woofer-mid/tweeter balance, mid/tweeter attenuation and rake, with separate knobs for each channel. The Hewlett-Packard display, glowing a fetching green (which must be this year's colour as the Aragons, the SP-9 and the CAL Tempest II power supply also glow green), gives you digital read-outs of every setting, again separated into left and right. With this bank of controls and the digital confirmation, it's possible to set up the system for sonically asymmetric rooms using test tone generators and spectrum analyzers, or you can (as you'll see) use it to compensate for recordings with any previous settings being easy to note. Power to the DAX is via an outboard unit a third the size of the DAX. This houses the on/off switch
and a front-panel LED; it connects to the DAX with a locking cannon plug.

Apogee presupposes that its customers know what they want to hear, so instructions for setting the controls amount to little more than doing it by ear. I did manage to find out how Apogee's Jason Bloom approaches the problem each time he sets up a DAX and his advice means less to-ing and fro-ing. Future DAX owners, take note:

1) Adjust the mid/tweeter attenuator, which is another way of asking yourself, 'Do I need to cut the upper frequencies?' (In the unlikely event that you need to boost those frequencies, there's still the toggle on the passive box.)

2) Adjust the balance between the woofer and the mid/tweeter. This maneuver attenuates either portion in 0.2dB steps. You won't believe it until you hear it, but this operation is audible
enough to change the character of the system from forward-sounding to muted, despite the seemingly limited operating range. And only a deaf person or a reactionary/liar would deny the audibility of a change of even one step.

3) Adjust rake angle. By tipping the response up or down in 0.5dB steps, it's possible to compensate for brightness or dullness without any loss of information or frequency extension. I've a feeling that owners of Quad electronics will find this not a little familiar.

4) Adjust woofer attenuation. This is especially useful for those who would have Apogees in small rooms. (No, there's no woofer boost because it's unlikely that anyone would ever need it. And if they do, they can always go back to steps 2 and 3.)

But here's where it gets bizarre. Word had reached me that the DAX, even with everything at '0', improved the performance of the Divas beyond the gains that you'd expect from mere biamping. That struck me as odd until I accepted that the DAX -- two amplifiers instead of one notwithstanding -- is a vastly more sophisticated crossover than the passive box supplied as standard. And not only does it do a better job of signal splitting, the DAX also optimizes the interface between amplifier and speaker, allowing the amplifiers to see a trouble-free resistive load instead of the complex impedance of passive-crossover'd Divas. But the reason it bothered me is because I preferred the DAX at '0' on four out of five recordings. Like most of you, I refuse to believe my good fortune when I find that my system and/or room needs no help.

And so it came time to play...

Read about the DAX's performance on Page 2.

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