DSPeaker Anti-Mode 8033 DSP Subwoofer Equalizer (TAS 204)

If you have a speaker with an excellent top end, you will likely hear that excellence in almost any listening room. As long as the speaker is kept reasonably far from hard reflective surfaces and the whole environment is fairly “soft” in acoustic terms, the ear will lock onto the direct arrival sound in the highs, and room effects won’t keep the top from sounding good.

But in the lower frequencies, the room almost inevitably plays havoc, no matter how good the speaker is an anechoic measurement. In the lows, the speaker’s sound is being kicked around by the room, and the direct arrival is audibly lumped in with the room effects. All one has to do to see this is look at some typical in-room responses, which are published around and about, especially with floorstanders where the height of the bass driver off the floor cannot be adjusted. The phenomenon of a boom somewhere below 100Hz and a large dip between 100Hz and 200Hz is all too common. (You can see some typical instances here. But you will find similar things in a preponderance of room response measurements of floorstanders).

These deleterious room effects can be somewhat ameliorated by careful placement. In particular, deep Allison Effect dips can often be largely eliminated. But no matter how one places speakers, there are almost inevitably deviations from smooth response in the bass, arising from the fact that listening rooms of domestic size have room modes—resonances quite widely spaced in frequency in the lower part of the audible range. Concert halls, which are much larger, have resonances, too, but in the audible range they are quite closely spaced and the result is reverberation, as one expects (and hopes, in concert halls), but reverberation that is quite smooth in frequency response. In domestic rooms one gets, instead, ups and downs, often wild ones, depending on how close the frequency is to a resonance frequency of the room itself.

This is something that can be in good part corrected electronically. And devices to do this correction have become increasingly popular in recent years. Indeed, quite a few subwoofers now come with such adjustments built in. And then there is the Rives PARC, which I reviewed in Issue 150, which is very successful but not inexpensive.

Now we have the DSPeaker Anti-Mode 8033. It is intended for subwoofers only. (DSPeaker also makes a speaker with built-in signal processing that automatically adjusts the speaker to the room—something for another time, perhaps). The great things about the Anti-Mode 8033 are that it works very well and costs very little—$350. So little that if you use a subwoofer you could (and should) buy it just to try it out. I am confident that if you do, you will have no regrets and will leave it in your system for good.

To test out the Anti-Mode 8033, I added an MK Sound MX350 subwoofer corrected by the Anti-Mode 8033 to a number of speakers. The MK was crossed over at 80Hz, corrected by the Anti-Mode 8033 to 140Hz. This meant that, in principle, the part of the range that the MK used was well within the correction range of the Anti-Mode 8033.

I tried this arrangement with some speakers that needed more bass as such—PSB Alpha B1s and Image B5s—and with some that really did not need more bass, or not all that much, like my reference Harbeth M40s, which are nearly full-range in my room. The best result was obtained with larger, more bass-extended speakers. Pairing satellites speakers with subwoofers is all very well as an idea, but the integration of subwoofers is best when the main speakers easily reach down to the transition point and beyond.

With all these systems, the subwoofer bass was, as is inevitable without room correction, a little irregular. It “bloomed” at certain frequencies in a way that, while not unattractive, was not really completely truthful. This is not the fault of the MK, which is an excellent subwoofer. The problem was the uncorrected room effects.

Enter the Anti-Mode 8033. Installation is a snap. (Just be sure to set the subwoofer level quite low to start with! The test signal is strong!). The device puts a signal into the subwoofer, letting the supplied microphone “listen” to the result at your intended listening position; the device then determines and remembers what should be done to make the bass better. For best results, start with a placement that avoids large or broad dips—the Anti-Mode 8033 only pulls down peaks. After you’re done, you may need to set your overall subwoofer level slightly higher to get the same subjective effect as before, since the system will have removed the “booms”—the peaks that arise from room resonances.

So how well did it work? The answer is, it worked a treat. The “bloom” frequencies were no longer blooming. The bass sounded smoother and much more precise yet still fully extended. (The smoothness and precision are connected. Bass in rooms is typically “loose” because it has frequency-response peaks. Time domain and frequency domain are connected in this frequency range in particular. The Anti-Mode 8033 does “minimum phase” correction, so the correction of amplitude also corrects phase to the extent that the bass in room is itself minimum phase.) The MK subwoofer as corrected by the Anti-Mode 8033 added to the Harbeths was considerably more precise and defined in the deep bottom end than either the (uncorrected) Harbeths alone or the uncorrected Harbeth/MK combination.

The results with the Harbeth M40s plus subwoofer corrected by the AntiMode 8033 were spectacularly good. The orchestral sound moved remarkably close to the category of suspension of disbelief, of something quite like the real concert experience—with suitable recordings, of course. This combination is one of the most truthful and convincing reproducers of large-scaled music that I have ever had in my listening rooms, and indeed ever encountered anywhere, in the bass in particular, outside of purpose-built rooms. (Systems like the Focus Recordings monitoring system in Copenhagen with a RFZ [reflection free zone] room designed from the ground up by Ole Christensen and Poul Ladegaard exist in a different world from ordinary home audio.) Smaller-scaled music like solo piano also benefitted from the depth and precision of the bass and the excellent pitch definition

I listened both for bass extension and especially for how the Anti-Mode correction improved bass pitch, definition, and precision. And it did a superb job. Fabulous results were obtained with things like the final low pizzicato notes in the Dvorák Nocturne with Fischer and the Budapest Festival Orchestra [Philips] or the pizzicato low strings that accompany the melody from the Borodin Petite Suite (“Night of my Nights”) in the Track 3 Kismet section of Telarc’s spectacular Bolero with Kunzel and the Cincinnati Pops. Transient precision was excellent, as was pitch definition. The system had become transparent all the way down. What was really going on with the bass instruments was surprisingly clarified by the Anti-Mode’s correction. (There is a bypass mode so one can do an A/B easily, though the shift in level mentioned earlier arising from peak removal has to be accounted for to make this fair.)

Then I tried the Dorian recording of Mussorgsky’s Pictures at an Exhibition played on the organ [Dorian]. Without correction the fantastic “Gnomus” had lots of bass—the MK goes way down—but that bass was somewhat undifferentiated compared to the Anti-Mode-corrected version, where the real bass sound was revealed, with the definite starts and stops of a real organ in operation. This version of the music is something of a virtuoso stunt musically, but it does give the bass part of your system a good workout, and here the bass sounded very much as it should on this stunning recording. “Gnomus” corrected by the Anti-Mode fell in the category of “you have to hear it to believe it”— spectacular in the way that pipe organs can be in reality. And of course the bass power and precision will pay off in the rock music world in a big way, too.

Was this the best bass ever in my listening room? I suppose the very top honors for that would still have to go to the corner woofers with time delay and DSP correction by TacT, reviewed in Issue 158 (corner woofers are marketed currently by Lyngdorf Audio). And in principle the multiple subwoofer concept, as realized in the Audio Kinesis Swarm system, should work better than the single sub that I was using—I am hoping to try that system out later on. Still, the results here were spectacularly good, among the best ever. The overall effect was surprisingly close to the sound of real music, of an orchestra or a jazz combo involving a string bass or a solo piano or any other music involving bass, and especially bass where definition, not just rumble, is at a premium.

I should mention that the DSP induces a small time delay—it takes a few of milliseconds for the processing to do its work. So you need to put the subwoofer closer to you by three feet (90 cm) to get the time integration correct. Do that and bingo. Note that the DSP only works on the subwoofer signal. There is no A-to-D-to-A with DSP in between operating on the main speaker signal. The main speaker signal is untouched except, in my case, by the analog crossover to the sub. And, of course, if one wanted to, one could even skip that by just splitting the signal and running the main speakers full-range. But generally main speakers like being relieved of the need to do low bass. This is traditionally true and as it happens actually true as well in most instances!

There is room for discussion of exactly how room EQ ought to be done, and no doubt as these devices become more common, there will be much such discussion going on. The Anti-Mode 8033 does not allow much in the way of user control. Except for adjusting the overall level of the sub, boosts at 25–35Hz or below 25Hz are all there is in the way of adjustment to the automatic setting. But I felt little urge to second-guess what it was doing, no real desire for user control in detail, so gratifying were the results of the Anti-Mode. If you want to go on later to the realm of detailed user control or corner woofers or multiple subwoofers or explicit phase correction (non-minimum phase correction), there are indeed brave new worlds ahead. But the Anti-Mode 8033 does such a fine job as is that you may well be ready to stop right here, and just listen to a bottom end that is a whole lot closer to perfect than any uncorrected bottom end at any price is likely to be.

Most reviews have to balance pluses and minuses. But this one is all pluses. The AntiMode 8033 works so well and costs so little that if you have a sub-woofered system that does not do detailed adjustments to the room on its own, there is really no doubt that you ought to try the AntiMode 8033. The improvement of the bass in such a subwoofered system is going to amaze you. And look at the bargain price. Power to the people!

Specs & Pricing

Device type: DSP subwoofer corrections system, automated setting, microphone included, to be inserted on input signal to subwoofer
Frequency range: 16-144Hz
Features: Three user selectable additional equalization filter (flat, boost 25-35 Hz, boost below 25 Hz), one or multiple measurement point calibration
Dimensions: 5** x 1.1** x 3.2**
Weight: 8.2 oz.
Price: $350

Simplifiaudio (U.S. Distributor)
California Suites Apt. 1001
5415 Clairemont Mesa Blvd.
San Diego, CA 92117
(724) 712-0899
simplifiaudio.com