Review of the DBX DriveRack 260 speaker processor

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former MLO owner/operator
Dec 27, 2004
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Rancho Mirage, California
Review of the DBX DriveRack 260 speaker processor

Replacing a speaker’s passive crossover with an active unit is generally considered to be a positive step. So I won’t go into why. If you like active’s, then the question becomes: which one?

In my case, I have a pair of Martin Logan Monolith IIIs with passive external crossovers that we’re just not giving me the best results with respect to panel and bass driver integration. Turns out there were two problems. One was my ten year old woofers were beginning to go. But even after replacing those, I felt more could be had from this speaker. Secondly, I started playing around with active crossovers. Using a pro-gear analog crossover, an Ashly XR2002, I got to see just what I had been missing. The sound was vastly improved. The critical low midrange and upper bass now merged better and the overall ‘tightness’ of the bass was improved. The highs were a whole new dimension of clean. For the money (around $300), it was a huge bargain in my book.
However, I’m never satisfied with the status quo, therefore I kept an eye peeled for better units. Then I read up on the DBX DriveRack 260 speaker processor ( Man, the description light up my eyes and spun my propeller fast!

The premise behind the DriveRack 260 is to meet the demands sound professionals have for setting up and configuring ‘high-end’ speaker and amp rigs in different venues. Therefore it is chock-full of features designed to accommodate almost any combination of drive unit (low/mid/high) pairings and positioning in challenging acoustical environments.

So what does a pro-gear unit have to do with an audiophile’s system? Well anything you care to do with it. These units are built like tanks (have to survive roadies) and have really good specs (amplify a noisy x-over and the audience won’t like it). So other than the weird connectors, they tend to work fine in a home A/V setting. Heck, since many ‘high-end’ units already have balanced interconnects, even that’s not the issue it might be.

For my application, several features of the DriveRack caught my attention:
- Crossover configuration flexibility:
o Pick from stereo 2 way or 3 way ( & many other, but not applicable here).
o Pick from any slope from 6/db octave to 48/db
o Pick from types of filters: Butterworth, Bessel or Linkwitz-Riley
o Mix-and-match, the LP can one filter type, while the HP can another
- Delays on any output channel, can delay the highs relative to lows
- Output adjustments for polarity and phase (in 1 degree increments!)
- Compressor or limiters (if needed) to keep from overdriving a specific output
- Parametric EQ on inputs and per output (each band has its own PEQ)
- SubHarmonic synthesis (OK, a gimmick, but great on old recordings)
- Full control of settings and stored program via a PC application

So, how do I use this beast in my system?
First, I wanted to have a three-way crossover for my Monoliths. Which sounds weird for a two-way speaker, but besides panel to woofer crossover, I also wanted to further split out the low (< 60Hz) bass and send it to my subwoofers. That’s three ways.
So I configured the DriveRack as a 2x6 (pro-sound terminology ;-), that’s two inputs and six outputs, split across two stereo channels.
The main point here is to configure a crossover, so I set the first channel (high) to have a High pass setting of 171hz, using a Butterworth 18 db/octave crossover. The second (mid) channel is set to 171Hz Low pass using a Butterworth 12db/octave crossover, and its high pass to 60hz (LR 24). Finally, the third channel (low) is set to Low pass 60hz using a Linkwitz-Riley 24 db/Octave filter.

Because my Monolith electrostatic panels sit about three inches ahead of the voice coil of the woofer, I added a small delay to the channel 1 (high) outputs, using the settings in fractions of a foot. This will acoustically align the panel to the Woofer.

With this baseline configuration, I wired the 260 up to the rest of the system (link to system goes here). Only needing RCA -> XLR adapters on the inputs, since my Sunfire Amps have balanced inputs.

Fired up the system and hey, it works like a champ. A little volume balance tweaking and then listened to a song. Much improved over the Ashly already.

Then pull out the weapons, my 30 band AudioControl RTA and the various test CD’s and DVD’s. Used these to figure the phase and polarity settings that best matched my speakers and their positioning in the room. Then, using same stuff, determine EQ needs and adjust to taste.
I do have to say that with an 8 band parametric on input and a four band parametric on each output channel (that’s six of those), I didn’t even touch half of the bands available to me. This thing offers an obscene amount of control available to the user.

The coolest thing has to be being able to sit at the listening position, RTA display at one’s side and a laptop on lap controlling the DriveRack via a serial cable and tweaking all those controls in real time and hearing (and seeing via RTA) the results.
I mean, have you ever wondered what a Bessel 12 db/octave filter sounds like compared to a Butterworth 18? What would it sound like if I flip the polarity of the woofer? Or shift it’s output phase 22 degrees? Or add a 0.28 ms delay?
Well, with this baby, you can answer those burning questions and more, all in real-time.

If it’s not clear by now that this a tweakers delight, then I’m not writing well enough. Believe me, this will keep you up way after your bedtime.

But it’s always about the sound, isn’t it? So here’s my summary of that:
It has made these great speakers into even better ones. The soundstage blend between all five speakers in the surround sound field is coherent and sooo smooth I can hardly believe I’ve done without this for so long.
The bass integration between subs, woofers and panels is about as good as it gets without a true room corrector device like a TacT RCS (which at >$5K is more than the DriveRack ;-)

Bottom line: If you have any speaker in which you can bypass the internal passive crossovers, and have enough amplification to bi or tri-amp, then this is the unit to get.


PS- I tried the passives again for the heck of it, and almost gagged. Yuck, they were all wrong. Hard to believe the factory sends them out into the world this way.
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