Some home theater enthusiasts see automatic equalization as a sonic savior. They believe it guarantees great sound. But it doesn’t.
Auto EQ technology automatically optimizes your sound system by measuring, then compensating for, the acoustics of your room and the performance of your speakers. It runs test tones through your system, measures the levels of the tones through a microphone, then analyzes the results and creates EQ settings that in theory make your sound perfect. If the auto EQ works well, you can optimize your system’s sound in a minute or two with the push of one button. There are all sorts of auto EQ systems out there. Some are powerful, allowing the creation of multiple filters to correct almost any conceivable room acoustics problem. Some are simple, with a small number of filters and a limited range of correction. Some let you average the results from multiple seating positions in your room. Some let you measure from just one position. Some are created by engineers with decades of experience and hard-won wisdom. Some appear to have been created by DSP code-slingers who don’t know much about audio. Some make the sound a lot better. Some make it worse.
Thus, when I heard the news that Velodyne was incorporating auto EQ into a new line of affordable subwoofers, I was excited but wary. Would the new EQ-Max line be like getting one of Velodyne’s beyond-awesome Digital Drive Plus subwoofers at a bargain price? Or would it be yet another auto EQ system that accomplishes little?As Velodyne’s Chris Hagen explained to me, the EQ-Max line is in essence a stripped-down version of the auto EQ function in Digital Drive Plus. It employs 1/3-octave-spaced infinite impulse response (IIR) filters at 40, 50, 63, 80, and 100 Hz. There are no filters below 40 Hz because the box resonance of the EQ-Max subs runs between 32 and 38 Hz, depending on the model, and attempting to apply correction at frequencies so close to the box tuning could cause distortion or damage the driver. According to Hagen, the correction range of the filters is limited to ±3 dB because more extreme correction could cause excessive phase shift.
I was eager to snag a sample of the biggest sub in the line, the $879 EQ-Max 15, but the Sound+Vision editors decided maybe we’d hold off on that one and put it in some sort of subwoofer mega-review at some future date. But when I suggested getting in the the $459 EQ-Max 8, just to see how good Velodyne’s auto EQ implementation was, they let me off my leash. With an 8-inch driver and a 180-watt RMS amplifier, the EQ-Max 8 ain’t a powerhouse, but it is the first sub-$500 sub I’ve seen with auto EQ. It’s also probably the snazziest sub-$500 sub I’ve seen, period. Besides auto EQ and a tiny calibration mic, it comes with a remote control, four EQ presets, a front-panel numeric LED display, and line- and speaker-level inputs and outputs.
I connected the EQ-Max 8’s line-level LFE input to the subwoofer output of my Denon A/V receiver. I used it with a set of Sunfire Cinema Ribbon speakers: three CRM-2s in the front, plus two CRM-2BIP speakers in the back for surround. I chose a crossover point of 100 Hz, which works well with the Cinema Ribbons. As with all the subwoofers I test, I placed the EQ-Max 8 in my room’s “subwoofer sweet spot,” a place along the wall under the screen, about a third of the way from the right side wall. This is where a single subwoofer usually sounds best in my room from my usual seating position. However, I also tried it in a couple of other locations: in the left front corner, tested from my usual listening seat; and in the sweet spot but with my listening chair moved to a spot where I’d measured a huge response hump at 47 Hz.
I chose the other positions because they’d present a greater challenge for the auto EQ. Running auto EQ is really simple. Plug the included mike into the jack on the front of the sub. Hold the mic near your head. Now hold down the EQ button on the remote down for 3 seconds. The sub automatically plays a series of test tones and adjusts itself. The whole process takes about 30 seconds.
Before I tried auto EQ, I played the EQ-Max 8 on its own just to find out what I was starting with. And what I was starting with is a real good little 8-inch subwoofer. When I played a swordfighting scene from The Last Bladesman, included on the latest Dolby TrueHD demo Blu-ray Disc, the EQ-Max 8’s impressive punch led me to believe I was hearing a much larger subwoofer. In the fight, the impacts of the swords against masonry walls produces a powerful (although absurdly unrealistic) boom, each of which filled my room with slamming bass.
Another scene from the Dolby disc, the train crash from Super 8, pummeled me with similar impact, although the deepest bass tones from the crash were absent. In my favorite deep bass test scene, the spaceship flyover and explosion in Chapter 3 of Star Wars, Episode II: Attack of the Clones, the EQ-Max 8 gave a strong sense of the ship’s powerful vibrations, even if it didn’t shake the floor as a good 12- or 15-incher would.
With music tracks, I got very smooth, grooving, tuneful, and surprisingly powerful response. Tony Levin’s Chapman Stick and electric bass lines on the 40th anniversary of King Crimson’s Discipline came through with the precision, punch, and subtlety for which Levin is famed. In a few cases, I felt almost as if I were Levin himself, feeling each tap of my finger on the Stick as it came through the bass amp.
I listened mostly in the Jazz/Classical EQ mode, but also found the Movies mode useful to amp up the bass for action flicks. To my ears, the Games mode sounded crazy-boomy (although I don’t play games to my opinion shouldn’t count for much here), and the Rock mode just seemed to add a little excess punch. So we’ve got a nice little 8-inch sub here. But what does the auto EQ do for it? Not a whole lot, at least in my room. My notes were filled with phrases like “about the same,” “maybe slightly tighter,” and “maybe a bit more impact.” (Bear in mind here that I couldn’t do an A/B comparison; I had to listen to a few tracks in factory reset mode, run the EQ, then listen to the tracks again, so there was a delay of a few minutes between the pre-EQ and post-EQ runs.) Overall, the auto EQ never hurt and sometimes seemed to tighten and smooth the sound subtly, but its effects were never readily apparent.
Frequency response 33 to 105 Hz ±3 dB (Jazz/Classical mode)
Bass output (CEA-2010 standard)
• Ultra-low bass (20-31.5 Hz) average: NA
20 Hz NA
25 Hz NA
31.5 Hz 95.3 dB
• Low bass (40-63 Hz) average: 113.1 dB
40 Hz 112.3 dB
50 Hz 113.6 dB L
63 Hz 113.2 dB L
I measured the frequency response of the EQ-Max 8 by close-miking its woofer and port, then scaling and summing the results, all using my Clio FW in log chirp mode. Measurements were done at factory default before auto EQ was activated. All four EQ modes are shown here. Jazz/Classical delivered the flattest, most even measured response. Relative to the Jazz/Classical mode, the Movie mode boosts a max of +6.2 dB at 40 Hz in a broad, low-Q band. The R&B/Rock mode boosts a max of +5.5 dB at 53 Hz, again in a broad, low-Q band. The Games mode boosts by a max of +5.6 dB in a high-Q, narrow band centered at 61 Hz, but has a steeper high-pass roll-off function below 44 Hz. With the crossover point set to 80 Hz, the low-pass crossover function measures -10 dB/octave to 120 Hz, then -21 dB/octave at higher frequencies.
I performed the CEA-2010 output measurement before activating the auto EQ function, using the jazz/classical mode. Measurements were made at 2 meters; I added +6 dB to scale the measurements to the 1-meter reporting standard mandated by CEA-2010. An L appears next to measurements in which the results were dictated by the unit’s internal limiter. The CEA is adjusting the CEA-2010 standard slightly; the revision wasn’t available at the time I did these measurements, but I did learn from the CEA that the revision mandates averaging by converting the dB values in the measurements to pascals for averaging, then back to dB. Averaging in pascals gave me the 113.1 dB low bass (40-63 Hz) average shown here. Averaging in dB, the previous method, gave me a result of 113.0 dB. Regardless, that’s good output for an 8-inch sub. Output at 31.5 Hz was 95.3 dB, but the EQ-Max 8 doesn’t produce measurable output below that frequency.
I also measured the effects of the auto EQ technology, using a calibrated Dayton Audio EMM-6 microphone, an M-Audio Mobile Pre USB interface, and a laptop running TrueRTA software. (Read more about this DIY measurement rig.) I used pink noise as the stimulus, with TrueRTA set for 12 averages to minimize measurement-to-measurement variation. I measured in four different combinations of subwoofer and microphone positions, in each case attaching the EQ-Max’s included mike directly atop the EMM-6. For each measurement, I reset the subwoofer to factory conditions, measured the response, ran the auto EQ process, then remeasured. Only two of the four graphs are shown here; results were similar with the other two. The measured effects of the auto EQ technology are visible, but subtle. It was usually able to find and attenuate the biggest response peak, but in my room the maximum correction was on the order of -2 dB.
If pure power for a paltry sum is your desire, you can easily find a more potent sub for the same price or less, such as the Cadence CSX-12 Mark II. But I’m guessing if you’ve read this far, you’re more into finesse, features, or compact size, in which case the EQ-Max 8 is a nice choice. In small media rooms, bedrooms, and budget audiophile stereo systems, this little sub will be right at home.