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

An Essential Subwoofer Upgrade

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.