Apogee's
latest is a dedicated active crossover for the Caliper, Duetta and Diva. Is it
the ultimate Apogee upgrade?
by Ken Kessler
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. In addition to offering attenuation of up to 6dB in 1dB steps for the woofer and the mid/tweeter, the 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 Q/-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 - so 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 bi-amplifying these speakers. 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. Ibis 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 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. 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.
The DAX itself is one of the most attractive pieces of high-tech hardware I've ever seen. 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. With this bank of controls and the display confirmation, it's possible to set up the system for sonically asymmetric rooms using test tone generators and spectrum analyzers.
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 the order in which 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 an another way of asking yourself, 'Do I need to cut the upper frequencies?'
2) Adjust the balance between the woofer and the mid/tweeter. This manoeuvre 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.
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. 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 bi-amping. 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. But the reason it bothered me is because I preferred the DAX at '0' on four out of five recordings.
Listen: When I set up the DAX, I was also playing host to somebody who has no reasons for wishing success on this product. I won't embarrass him by revealing his name; all I'll say is that he's from the competition. Anyway, we put on some serious music - Billy Cotton's Wakey Wakey Show and George Melly on C5 Records - and he just looked at me, uttering a British expletive which rhymes with 'buckshee' and grinning from ear to-ear. We fiddled with the knobs, cranked up the volume, dug out some naff mono CDs of ultra-thin-sounding British pop from the 1960s. We rocked. And we heard the Kinks' 'Waterloo Sunset' like it's never been heard before.
The most blatant manifestation of the DAX is the way it allows the Diva to present deep bass notes. I admit that, on occasion, the Diva can sound a bit overwhelming, with bass which thunders and roars. DAX'd, the Diva's extension remains constant but the bottom octaves acquire a sensation of greater control. Equally chilling are the gains in soundstage creation, image placement and specificity. The Diva, sans DAX, is simply one of the best imagemakers I've used; the DAX opens the sound and removes and last vestiges of texture to the silences between instruments and players. What the controls do is allow you to dial in the most realistic stage depth in a manner not unlike that - of the control unit for the Infinity IRS Betas. And the more you learn about the controls and their capabilities, the more they take on the nature of a focusing ring on a camera lens.
But here's where I find myself at cross purposes with the whole concept of active crossovers. Until the DAX arrived, I though of trick crossovers as a way of optimising the speaker, something to set once and leave alone. I found myself using the DAX to compensate for the recordings rather than the hardware or the room. I don't want to give the impression that the DAX works like a dream-world equalizer or even like the rather splendid Cello Palette. The adjustments to the sound are too subtle and too precise to suggest any gross tampering. What it becomes, then, for an Apogee owner is the ultimate surgical instrument.
In the year I've been using the Divas, I've tried them with single amplifiers (in bi-wired mode) running to over £10,000 per pair. The DAX offers such a transformation with even the affordable Aragons that two Aragons plus DAX at a grand total of £8100 is preferable to any other non-DAX combo I can name. As it stands, the DAX is nothing less than the most exciting development yet for Apogee owners, a device so clever that I wish other manufacturers would offer similar units for their bi-ampable speakers. £4.5k for a black box? Yes. And it's worth every single penny.
Reprinted from Hi-Fi News &
Record Review August, 1989