Rane THX 44 3.1-channel equalizer.

Manufacturer: Rane Corporation, 10802 47th Ave. W., Mukilteo, WA 98275-5098; 425-355-6000; www.rane.com

Price: $1,099

Source: Manufacturer loan

Reviewer: Howard Ferstler

Back in issue 83, I reviewed two very interesting and fine performing equalizers: the Rane ME-60 and the same company's THX 22. I found the ME 60, which employs 1/3-octave filtration from 25 Hz to 20 kHz, to be slightly superior to the lower priced THX 22. This was mainly because the latter unit only had 1/3-octave filtration up to 800 Hz, with the range above that covered by two parametric filters that were a bit more fussy to adjust than the graphic sliders at lower frequencies. Still, the THX 22 was probably the better buy of the pair (it cost $499, whereas the ME 60 cost $699), not only because it was nearly as good, but also because its lower shelf profile and ability to remove its rack-mounting ears made it a more agreeable consumer item. In that review article, I also made a brief mention of the more upscale THX 44 model, and it is that item that I am more formally reviewing here.

As I noted in that earlier review, equalizers are indeed interesting items. I had discussed them previously in issues 68 and 79, and pointed out that some versions are very basic and cost very little, while others are elaborate and flexible in the extreme and often cost quite a bit. The THX 44 is one of those "quite a bit" items and obviously we would want to know just what it offers that makes it so special.

First off, unlike the two-channel THX 22 and ME 60, the THX 44 can equalize all three front channels in a surround-sound speaker package. (Rane promotes the THX 22 as more of a surround-channel equalizer than what one would want to use up front, even though I reviewed the device for use as a high-end stereo equalizer.) In addition, the THX 44 has the ability to effectively equalize the subwoofer channel. Don't sell this additional function short.

Before getting into that and other performance details, here is what the unit offers in the way of features. Between 80 and 800 Hz you get 1/3-octave, ISO spacing constant-Q filtration, and these 11 adjustments are controlled by vertical slider controls with a +/-6 dB adjustment range. Between 1 kHz and 10 kHz you get two parametric equalizers, each with a +/-4 dB range. (The THX 22 had a +/-6 dB parametric range, probably because surround speakers will possibly have wider response deviations to correct than more formidable main speakers.). You can set either parametric filter at any frequency point between the noted limits and each has the ability to adjust a range spanning 0.7 to 3.5 octaves.

The subwoofer section is a two-band parametric job, with each section able to center up at any frequency from 20 to 80 Hz. The adjustment range is +/-6 dB, and the coverage with each can be from 0.5 to 2.5 octaves in width.

Other important performance parameters include a S/N ratio that varies from 120 dB on down to 87.5 dB (depending upon how extreme the controls are set), an input impedance of 10 k ohms, an output impedance of 50 ohms, and a THD level of no more than 0.001 percent. This is pretty top-tier performance, which is what one would expect for a "THX Ultra Certified" component like this. While some might debate certain aspects of the THX program (most notably those dealing with speaker and surround processor parameters), there is a lot to be said for it what it can offer when it comes to straightforward electronics, including equalizers.

Hookups on the back are simple: four RCA jack inputs and four RCA outputs for conventional Installations, along with one each DB-25 jack (input and output) for hooking up to processors or receivers that can make use of such connections. The only front-panel control is a bypass/on button that lights up a red indicator when the bypass mode is selected. There is also a small blue-tinted power LED.

The unit is 3_inches high, 19 inches wide (just under 17_inches wide with the rack-mount ears removed), and 8_inches deep. It comes with a removable protective panel that can be installed over the entire control area once the initial set up is complete, thereby eliminating any chance that a bumped slider will require doing the alignments all over again. With the panel installed, the THX 44 is an archetypal black box.

Speaking of alignments, that is the name of the game with a device like this, and to do it right both Rane and I recommend the use of a good 1/ 3-octave real-time analyzer. Rane makes one of those itself, their RA 30, and it should be able to do the work just fine. AudioControl also offers its R 130 model (reviewed by James Frane in issue 76), and it should also be able to work just fine.

AudioControl also has its more utilitarian SA-3051 model, which is what I use. I like it, because it offers a 20-second integration feature that allows for a slow, moving-microphone technique at the listening position to minimize standing wave and reflective hot spots. This is a great equalizer if you want to measure a meaningful room curve.

You probably could use an SPL meter with an equalizer like the THX 44 if you had a test disc with discrete frequency signals at the indicated 1/3-octave intervals. However, it would require great care, considerable patience, and quite a bit of time to get things right. Even with a good RTA the job can eat up a full afternoon, at least if you really, really want to fine tune things to the ultimate degree. Yes, I realize that in my earlier review I said that the THX 22 could do the job in fairly short time. However, the THX 44 equalizes one more satellite channel, plus a subwoofer. With that many options, one feels tempted to go to the limit and get a perfected result.

I set up the THX 44 up in my middle system, which up until that time had been equalized by a THX 22, with the center rather roughly equalized by a 5-band equalizer built into the system's Yamaha DSP-A1 processor/amp. (I reviewed the DSP-A1 in issue 72.) Needless to say, even with a fine NHT VS1.2 center-channel speaker in operation, the center performance could never be refined to the same degree of flat-response near perfection that I could squeeze out of the left and right mains with the help of the THX 22.

Those mains are at this time a pair of modified Allison AL-125 models (with the bottom woofer section of its two-woofer array removed), and with them placed on top of 30-inch-high benches. (The crossovers have also been modified.) Because of the room layout, each speaker is also roughly two feet from each side wall. Yep, a room like this is going to cause some serious boundary suckout problems in the middle bass, and the unequalized result is a broad dip with each channel that is centered at about 160 Hz. Just about any recording that includes cellos is at a disadvantage with this package, because the instruments will sound thin and distant.

Happily, it took me only a few minutes to flatten out the dip with each channel, and it took only another half hour to eliminate mild bump ups at 500 Hz and mild dips at 6.3 kHz. I also diddled a bit to flatten out some very small anomalies at a few other frequencies. The result was the same as what I got previously with the THX 22.

The next target was the subwoofer. Up until now the SVS 16-46PC in that room (reviewed by me in issue 88) has been assisted by a Hsu "Optimizer" equalizer (reviewed by me in issue 90), because of a room-related dip down really low and the slight rolloff the SVS exhibits below 35 Hz. With the Optimizer in place, the sub is powerful right down to below 20 Hz, and at the levels my wife and I listen at in that room the balance is borderline perfect.

Still, the room also generates a mild listening-position peak at about 50 Hz, and so the bass was not as linear as I would like. The THX 44 took care of the situation nicely. One of the parametric adjustments eliminated the peak, and configuring the second circuit to dial in a full 6 dB boost at 20 Hz eliminated the need for the Optimizer.

The result of this fiddling was a response curve that was +/-1 dB from 100 Hz on up to 16 kHz, with a mild bass rise as the frequency dropped down to 25 Hz. If you want to know what this curve looks like, go look at Figure 9 of the series I ran in issue 95, because the two are nearly identical. That earlier curve, run in my main room, combined the talents of a pair of Allison IC-20 mains, a THX 22, and a Velodyne F1800RII, and the only flaw was a mild peak at 50 Hz. The results I got with the THX 44 and a group of cheaper speakers set up in my smaller room was just as flat from 100 Hz on up and had no 50-Hz bass peak further down. The result was the best and most listener friendly response curve I have ever measured--anywhere.

Once I accomplished the left, right, and subwoofer channel work I moved on to the center and in about a half an hour I had the VS1.2 measuring just about as good as the Allison units. There was a tweeter rolloff above 12.5 kHz, but that really is not going to be a big deal with typical program material.

Before equalization, a pink-noise comparison between all three speakers showed them to be anything but identical sounding. Even the left and right mains sounded different, due to boundary-distance differences. After equalization, the three systems sounded almost the same and switching between the bypass and equalized modes with a pink noise source easily dramatized that substantial changes had been made to the overall response.

Incidentally, one nice thing about this current speaker arrangement is that although the center speaker is sitting fairly high up on a big TV monitor, the bench-mounted, flanking AL-125 models are tall enough to put their localization clues at a similar height. This allows the soundstage to be decently flat from left to right, which is not often the case with some three-front-speaker arrangements. At this time, all three of my audio-video systems have center and main-speaker heights that are similar enough to allow for good three-speaker soundstaging.

Once I had the response curves looking satisfactory, I did some serious musical listening, comparing the equalized and bypassed sound while listening to a number of fine recordings.

One that showed the value of having three equalized channels up front was David Diamond's Kaddish for Cello and Orchestra (Naxos 8.559155). In this case, the cello is at hard center and if I played this CD back using my DSP-A1's Classical/Opera mode (which steers all L+R information to the center channel) the overall effect was terrific. Indeed, if I switched to the phantom-center mode the cello pretty much sounded the same in terms of tonality as it did with the steered version, but with better stability and focus with the steering engaged. Incidentally, this disc also includes Diamond's Psalm and Symphony Number 3, and the performances by the Seattle Symphony are exemplary.

Another disc that showed off the advantages of three-channel equalization was Brothers III, featuring Ken and Harry Watters (Summit CD-369). The featured instruments are a trumpet and trombone, and with a steered center channel the result was sensational. With the equalizer set to bypass, the focus and detail with the center speaker in operation were OK but not great. With the equalization engaged the difference was significant. There is no doubt in my mind that employing an equalizer that can smooth out all three channels up front will highlight the advantages of any good three-front-channel sound reproduction, because it will allow the center speaker to better integrate with the left and right mains.

However, there is an important thing to remember when using an equalizer of this caliber. The adjustment ranges possible vary from +/-4 to +/-6 dB. This is not a huge amount in the world of equalizers, and it shows us that the THX 44 is not designed to work with junk speakers and turn them into decent-quality items, let alone into champions. The speaker/room combination needs to be pretty good to start with. If that combination is not good, the equalizer is not going to be able to do the trick.

Sure, you could use a good equalizer with a greater adjustment range (Rane makes those, too), with models having up to +/-12 or even +/-15 dB not unheard of. However, speakers with power-response and radiation-pattern problems requiring that kind of compensation are probably going to sound a bit odd when adjusted for flat response.

Even when not equalized they will have problems with the mismatch between the first-arrival and often much stronger room-response signals. Equalizing the latter for flat response at the listening couch will probably make things even worse--even if there are no driver or amplifier overload problems from pushing things hard to compensate for middle-bass suckout artifacts. With equalizers, a light touch is needed, and the THX 44 makes it impossible to overdo a response-flattening job.

The Rane THX 44 is a rather expensive equalizer (although there others that cost even more), but it is definitely worth the selling price--if you have (or your dealer or a friend will loan you) a good 1/3-octave RTA to allow for proper set-up work. To my way of thinking it is just about impossible to have world-class sound without making use of a device of this kind, because even the best speakers will have a frequency response anomaly or two that can stand to be fixed.

--HF