Rane ME-60 and THX-22 Equalizers.

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

Price: ME-60, $699; THX-22, $499

Source: Manufacturer loan

Reviewer: Howard Ferstler

Background: Equalizers are interesting items, and I have discussed them previously in Issues 68 and 79. Some versions are very basic and cost very little (I have seen one-octave equalizers in discount catalogs selling for under a hundred bucks), while others are elaborate and flexible in the extreme, often costing quite a substantial amount--into the thousands of dollars.

I own both a rather basic, one-octave model (an AudioControl Ten, Series III that is hooked into my smaller system, and which is used to equalize out a boundary-related null) and also a rather more versatile one (the same company's monophonic, C-131, 1/3-octave job, working to equalize the center-channel speaker in my larger system), and my experience has been that the more versatile versions are often very useful, indeed, while the cheaper and more basic models are often more trouble than they are worth.

Well, they are more trouble than they are worth, if the user wants to correct for response anomalies that are narrow enough in bandwidth to make correcting them with a broad-band equalizer a real chore or impossibility. However, under some conditions, as I noted in my comments in Issue 68, a one-octave equalizer can sometimes be used as a sophisticated tone control, although standard bass and treble controls can often do nearly as well.

Still, when most of us think of equalizers, we picture a piece of equipment that works to solve system problems and not recording problems. As system problem-solvers, equalizers can be used to deal with one or more of three common anomalies that we find with our sound-system and listening-room combinations.

First, they can correct for deficiencies within speaker systems themselves. For example, a two-way system with a woofer in the 6-to-8-inch category will usually have a significant power-response notch just below the point where the woofer dovetails with the tweeter. This notching, which shows up in any measurement of the total output of the speaker in all directions (and which will also usually show up in a measurement of a system's total-energy room response), is the result of the woofer losing radiation efficiency as it climbs toward the crossover point. Its response narrows as the wavelengths it is being called upon to deal with get progressively smaller in relation to the driver's diameter. As the frequency continues to climb, the tweeter restores off-axis signal strength as it cuts in above the woofer range, and the result is a dip in the power response, generally centered near the crossover point.

Notches of this kind can even show up in three-way systems, at both the woofer/mid junction and the mid/tweeter junction. How severe they may be will depend upon both the driver diameters and the crossover points chosen by the manufacturer. In any case, a reasonably decent flattening of a speaker system's power response can be done by means of a good equalizer.

Unfortunately, flattening out a power- or room-response notch is not as straightforward as it seems. This is because many systems that have such a notch may be quite flat on axis or at moderate angles off axis. If you flatten out a power-response notch with an equalizer, even if you do a job that looks perfect when you check the results over with your real-time analyzer (RTA), you may end up boosting the narrow, forward-angle response of the system over that short frequency range.

The result might be a speaker with its factory-dialed-in imaging abilities compromised, or with a sound that is now somewhat brittle or wiry when the system is listened to at closer distances. Yep, the fact is that the manufacturer may have intended for that power-response dip to be there.

In any case, it is probably not a good idea to try to equalize away narrow-bandwidth, speaker system frequency-response "defects" that are more than three or four dB out of line in either direction. It is preferable to bite the bullet and obtain better speakers.

The second problem an equalizer can deal with involves speaker/ boundary interactions. When speakers are located in such a way that their woofer centers are within a foot or two of room boundaries (floor or walls), it is likely that quarter-wavelength cancellation artifacts will crop up and produce a dip somewhere in the room-power response.

What's more, it really does not matter how good the woofer driver may be, because this artifact has nothing to do with driver quality. Unless the speaker manufacturer has somehow designed in a bit of frequency-response compensation to deal with this artifact (and doing this usually means that the speaker is either a floor model or a stand model that requires a dedicated stand), or positioned the woofer driver or drivers so close to room boundaries that the artifact does not show up at all within their operating range, the system will probably have this kind of suckout phenomenon showing up somewhere in the 150-to-300-Hz range.

Because this is a fully power-response related artifact, an equalizer can do a lot to correct the problem. Indeed, it is with anomalies of this kind that an equalizer is at its best, because cancellation suckouts impact both the power response and the direct-field response. Flatten the curve as your RTA says to, and the woofer/boundary suckout problem is brought under control.

However, there is no such thing as a free lunch, and if boundary-related artifacts are too extreme, the boost applied to correct them may overdrive smaller woofers or smaller amplifiers. So, take care when using an equalizer to correct for these kinds of artifacts.

The third problem that an equalizer can deal with involves standing-wave artifacts. Unlike speaker-design problems, which may or may not respond well to equalizer manipulations, and woofer/boundary suckout artifacts, which often can be dealt with effectively by an equalizer, standing-wave artifacts, which involve boundary/boundary interactions and listener position, have to be dealt with very carefully.

This is because standing waves involve more than frequency response. They also involve anomalies in the time domain. That is, a standing-wave resonance (which will show up as a peak in an RTA-measured room response) is delayed in time, compared to the first-arrival signal, and it also is reverberated. Your RTA will not be able to detect the delay factor at all.

So, if you use an equalizer to notch out a big standing-wave peak at, say, 100 Hz, your correction will have no impact on the time that resonance lasts, and you will also be putting a notch in the first-arrival signal. You will have partially fixed the problem with the room peak (it will be reduced in amplitude, but the time the resonance exists will not change), but at the same time you will have screwed up the first-arrival signal.

Using an equalizer to correct for standing waves should only be done after all other possible cures are attempted (basically, this mainly involves changes to the room itself, or changing the listening position to get out of a peak or null area), and I would say that trying to fix a peak or dip of more than 4 or 5 dB will probably get you into trouble.

OK, this kind of makes it looks like equalizers are not all that helpful. However, what I have been trying to get across is that for the best in sound, the enthusiast first has to obtain decent primary hardware, which obviously means good speakers. He then has to locate those speakers in a reasonably good room, with them positioned for the best performance possible.

If things go well, the power and room response of this combination will be flat and we will have a happy audio buff. However, chances are that there will be a few minor but still significant peaks and dips with even the best room/speaker arrangement and this is where a good equalizer such as either the Rane ME-60 or THX-22 can come in really handy.

Specifications and Features: The ME-60 is a professional-grade equalizer that employs two channels of 30-band, constant-Q, 1/3-octave equalization. It has a generous 12 dB boost/cut range (slider-movement range is about 3/4 inch), independent level controls for each channel, independently adjustable high and low-cut filters for each channel, an independent bypass feature for each channel, and it will handle XLR, 1/4-inch TRS, and RCA connectors. The dimensions are 19 inches wide, 3.5 inches high, and 8.5 inches deep. The width includes non-removable rack mount flanges.

The ME-60's impressive-looking front panel is fully exposed, but a protective cover is offered as an option. Its use is something that I strongly suggest, because it is all too easy to accidentally bump a slider and throw things out of whack. In any case, this is one versatile unit, that can be used by both audio buffs and professionals.

Note, however, that its power-line connector is a three-prong device, meaning that it will not plug into the back panel of a typical receiver or preamp. Hooking the unit into your system requires that you either plug it directly into the wall and make use of its on/off switch, or that you hook it into a switch-controlled power strip that also turns on the rest of your hardware.

The THX-22 is more consumer-oriented. It has independent, 1/3-octave, constant-Q equalization for each channel between 80 Hz and 800 Hz, and then has two parametric (adjustable-Q, adjustable frequency) equalizers for each channel that are usable at any frequencies between 1 kHz and 10 kHz. The bandwidth of each parametric adjuster is variable from .7 octave to 3.5 octaves. The adjustment range of the graphic and parametric sections of this device is plus or minus 6 dB, which is more than enough to cover the sensible adjustments that I noted above.

Unlike the pro-oriented ME-60, the THZ-22 has only a pair of RCA inputs and a pair of RCA outputs. No exotic hookups are included, nor does it have a volume control (it has unity gain), or high and low-pass filter options like the ME-60. It does have a bypass switch, however.

The THX-22 comes standard with a front-panel cover that must be removed to adjust the unit. (Four small screws hold it in place.) The idea is to fine-tune your system's frequency response, and then re-install the panel to keep your settings from being knocked askew by careless hands. With the panel in place, only the power-on light is visible. The unit has no on-off switch, meaning that you either plug its two-prong power plug into a switched outlet on your preamp or into a switched-controlled power strip that handles your entire system.

While the ME-60 takes up two rack spaces, the THX-22, with its width of 19 inches (reduced to just under 17.5 inches without its removable rack mounts), 8.5 inches of depth, and 1.75 inches of height, occupies just one rack space.

I should note here that according to Rane, the actual primary function of the THX-22 is the equalization of the surround channels in a home-theater system that has pre-out and amp-in connections for those channels. However, they also note that it will work just fine in a standard two-channel installation.

Rane also offers the TXX-44 ($1,099), which combines three channels (left, center, and right) of THX-22 grade equalization in one double-rack-space box, and throws in a two-band parametric equalizer for the subwoofer. The idea is for a full, TXH home-theater system to use the THX-44 on the front channels and subwoofer and the THX-22 on the surround channels.

However, as I noted, the THX-22 can be used to equalize any kind of stereo audio system. Indeed, its overall quality would make it, as well as the ME-60, a good addition to the very best high-end stereo systems that I can imagine.

Each of these equalizers comes with a comprehensive owner's manual that will explain hookup options, features, specifications, and grounding needs in often rather extreme detail. The manuals also contain a listing of other Rane products. All three also come with a standard 2-year warranty, and if the new owner sends in the warranty form that comes with the manual, the warranty is extended to three years.

Listening and Measuring: The main-channel, Allison IC-20 speakers in my primary system have exceptionally flat room response at the listening-couch position, about 15 feet from each speaker. My measurements usually involve an AudioControl SA-3051 RTA, and while the unit is operating in its "20-second-integration" mode, I utilize a moving-microphone technique to minimize standing-wave and reflection artifacts. Typically, I measure +/- 2 dB over most of the operating range of the IC-20s. However, they still each display a mild, narrow-band, 3 or 4 dB dip centered at 1600 Hz (this artifact must be room-related, because it does not show up with close-up measurements), and there is also a standing-wave peak of about the same size centered at 125 Hz along the axis of the listening couch.

I hooked the ME-60 into the system and it took me all of 20 minutes to eradicate the dip and peak and flatten out a few of the other, much smaller peaks and dips. When I got through, the response was +/- 1 dB from 80 Hz to 16 kHz. (I normally let the response rise a few dB below 80 Hz.)

During this time, the ME-60 was a joy to use. However, I will admit that once the corrections were done, there was not much audible difference between the corrected curve and the bypass when listening to music. Even with pink noise the contrast was slight.

I then switched to the THX-22 and it took me somewhat longer to deal with the artifacts. The standing-wave peak was no problem at all. However, the dip at the higher frequencies is only one-third octave wide at the bottom, and so even at its narrow-width setting of .7 octave, the parametric equalizer could not effectively eliminate it. If I flattened out the low point, I got 2 dB peaks at 1 kHz and 2 kHz.

However, again, the corrections were so slight that an A/B comparison with the "bypass" was tricky to make anything out of. You could barely hear the difference with pink noise, and with music the results were just not audible. The upshot here is that if your system is already flat-responding as hell, it is unlikely that an equalizer is going to be of much use to you, even if there are a few minor anomalies in the frequency response here and there.

Fast-forward now to the following week and my smaller system. This installation consists of my modified (sawed-off, with the bottom one of the two woofers removed) Allison AL-125 speakers positioned up on 30-inch high benches, with side walls that are within a couple of feet of each system. The low bass is provided by a Velodyne FSR-12 subwoofer, and during my testing procedures I used the Velodyne's own crossover and the preamp-out/main-amp-in hookups of my processor amp. This allowed the equalizer to work with both the sub and the satellite speakers.

Because of this layout, with either satellite speaker there is a substantial, 6-dB boundary-cancellation suckout centered at about 160 Hz, with the depression still being significant between 100 and 250 Hz, and with additional, probably standing-wave-related small peaks and dips within the bigger dip. There is also a mild peak centered at about 500 Hz. There is no way to correct for these problems with the speakers and listener positioned as they are--other than to apply equalization.

Note that I have also measured these same speakers, as well as a number of other excellent brands, on 17-inch stands in my main room, and the suckout phenomenon showed up there, too. This artifact is the result of speaker positioning, not driver design. Speakers and stands do not get along as well as a lot of people think, and the improvement in clarity that stands appear to deliver is often partially the result of a boundary-related, power-response cancellation in the mid bass.

For some time now, I have used an AudioControl Ten Series III stereo equalizer, working in combination with my subwoofer crossover, to deal with the dip in the small system. However, because the Series III is a one-octave, variable-Q unit with a very broad correction range at moderate settings, doing the job right required considerable diddling with adjacent slider controls to compensate for the broad range of the controls doing the primary correcting. In addition, none of the controls of this one-octave, stereo unit were centered at 160 Hz, although at least there were two centered at 500 Hz, where the systems exhibit that slight peak.

After much work and time (probably a couple of hours of experimentation over several sessions), the Ten Series III managed to get the dip and peak under control, and the result was a response curve that is quite flat: +/- 3.5 dB from 80 Hz to 16 kHz, with no serious problem showing up at all at 160 Hz. Doing the job required some rather extreme slider adjustments and counter-adjustments, however.

Obviously, this installation is a candidate for serious equalizing, and so I was interested in seeing what the ME-60 could do. After hooking it up in place of the AC unit, I measured and adjusted, and after about 20 quick minutes, I had a response curve that was +/- 1 dB from 63 Hz to 16 kHz. The ME-60 did a spectacular job of handling the boundary null. I give it an A+ for sure, when hooked into an installation of this kind.

I then replaced the ME-60 with the THX-22 and it took me about a half hour to get things where I wanted to be. The mid-bass suckout and slight peak at 500 Hz were no problem at all. However, the system does have the usual anomalies above 800 Hz, which typically let it only get to +/- 2 dB resolution. It also has a 3 dB dip centered at about 6.3 kHz that the ME-60 dealt with easily. However, the parametric unit in the THX-22 was less effective. Even so, I got a curve that was +/- 1 dB from 63 Hz to 5 kHz, with only a mild roll-off above that point: 3 dB down at 16 kHz. To do this, I had to combine the outputs of the two parametric controls to keep overlap artifacts from causing problems.

The upshot of all of this is that either unit could deal with some fairly serious artifacts very effectively. The ME-60 was a tad better and a tad easier to use, but the overall subjective impact of each was about the same, and we have to remember that the THX-22 is lower in price than the ME-60 and also takes up less shelf space.

In terms of the musical benefits, there is little doubt that both equalizers helped to improve the sound of the smaller system. The mid-bass reinforcement definitely gave a more realistic feel to instruments like cellos. Without equalization, those instruments lacked body and richness, and seemed to be further back into the orchestra than they should be. However, I should also note that my regular one-octave equalizer also did a passably decent job with this system, although the Rane units did the correcting much, much faster, and the results were subtly better.

While I had the Rane units on hand, I was in the process of reviewing the AR Phantom 8.3 speakers. With this speaker, I measured a flatter-than-average room-response curve between 160 Hz and 11 kHz. However, like many systems with smallish woofers that cannot get into the deep-bass range with real authority, the Phantom 8.3 exhibits a peak in the 80-Hz range that helps it to deliver big-bass impact.

Interestingly, the Phantom was attached to its dedicated stands during this analysis, and yet they exhibited no mid-bass dip. This is because the designer included a switchable feature that allowed the system itself to compensate for certain boundary-related artifacts. (Careful speaker placement is required to make this pay off, of course.) Hence, there was no need to equalize away a suckout notch. The system also has a mild dip centered at about 4 kHz that is probably crossover related.

I hooked the Phantom speakers into my main system in the big room and worked on them with both the ME-60 and the TXX-22. The dip at 4 kHz was a snap for the ME-60 and with a bit of work I got it flattened fairly well with the THX-22.

However, the big change involved taming the 80-Hz peak. Both equalizers did the job, but the upshot was bass that was rather anemic-sounding. Flattening the bass peak of a small satellite speaker without a subwoofer being involved will often result in tinny sound, and if you try to dial in some low bass with the equalizer to offset the loss of that peak (the ME-60 can do this, but the THX-22 cannot), you risk damaging the small satellite woofers. Clearly, the choice by some manufacturers to put a peak at that point has a rational foundation.

With any small-woofer satellites that cannot get into the low bass and that also display a peak in the 80-Hz range, I strongly recommend the installation of a good subwoofer before trying to correct for any bass deficiencies with an equalizer. Indeed, in many cases, a proper subwoofer crossover set up will eliminate the peak, because the satellite will have its bass electrically rolled off before the frequency gets low enough for the peak to manifest itself.

So, I will say here that I very highly recommend both of these equalizers if your audio system has frequency-response problems that are not too extreme. If it has an extreme problem that is related to standing waves or poor speaker design, I suggest that before getting an equalizer, you try to correct the room anomalies that are causing the standing waves and/or replace those poor speakers. Then, and only then, should you try to fine-tune the frequency response to get the performance into the true, high-end-sound category.

I cannot think of any stereo equalizer that could do this kind of job better than the ME-60, and the THX-22 will probably be able to do the required adjustments as well as the more expensive unit 90% of the time. If you have a home-theater system, it strikes me that using the three-channel (plus sub), THX-44 version to get a better matchup between the main and center channels would be almost mandatory if the very best in home-theater sound was required.

Oh yes--do not attempt to equalize any audio system without employing a good measuring device to check your work. The most convenient, ball-park item is a 1/3-octave RTA (intelligently used, of course, since these devices have their limitations) and both Rane and AudioControl have models available that are not outrageously expensive. I do not recommend the use of one-octave RTAs for precision work, by the way. -- HF