DSpeaker Anti-Mode 8033 C 

The Absolute Sound says "What this will do for a subwoofed system has to be heard to be believed"..."A must try for anyone who uses a subwoofer..."

The DSpeaker 8033 subwoofer correction system has already earned a TAS 20010 Golden Ear Award, before the review has even been published. For the money, there are few other tweaks that can benefit your system as much as the Anti-Mode 8033.

Comments from Stereophile's "Music in the Round"

Why the Anti-Mode is better than your Sub's EQ
Some products in the market utilize fixed band graphical equalizers when trying to struggle against room distortion. This kind of solution is very inaccurate and is potentially incapable against narrow resonances that can occur at arbitrary frequencies. They usually also involve the user for measurements and fine tuning. Some equipment also only tries to compensate for the amplitude response ignoring phase completely. In such cases the compensation will not lead to improved transition response. Another problem in he existing parametric equualizers is the limitations in their spectral resolution. Missing a center frequency by even as small a deviation as 1 Hz, the modal characteristic can be made even worse than the original. In 8033, the spectral resolution is improved and the computation power of 24 AMFs is enough to make even the worst room compatible with subwoofers.

Your Room Sucks
The average listening room has many low frequency resonance frequencies. Because of this, even the best subwoofer may not sound good enough. Much of a subwoofer's bass output and performance is masked by these resonances, we susually hear this as sluggish bass, and muddy sound that affects frequencies all the way up to the midrange. This problem is exacerbated when your sub is placed near a wall or corner.

Walls, floor and ceilings of the listening room are an audio system's nightmare. The early reflections will inflict both constructive and destructive interference, introducing up to +/- 6dB peaking or attenuation per single reflection. The worst of all are the modal resonances also known as "standing waves", which will impair the bass response with even as high as 30 dB peaking and narrow resonances which decay slowly. Every room has at least one high-Q resonance.

DSpeaker's Anti-Mode technology eliminates resonances introduced by the speaker and the room by equalizing both amplitude and time domain responses using very accurate digital signal processing filter structures and anti-phasing technology. This way, the listener can hear frequencies down to the cut-off frequency of the subwoofer. Transient response is also drastically improved in the process, making bass sound faster and more controlled.

Compensating for Room Modes with the Anti-Mode
Anti-mode technology is designated to eliminate the devastating room resonances, but it in fact also compensates for the response of the whole system.

The basis of the technology relies in measuring the transfer function from the sound source to the listener with microphone. As the counter-model of the room is achieved by sophisticated algorithm, both amplitude and phase characteristics of the system will be improved. The algorithm is capable of making crucial decisions of which phenomena can and should be compensated for. For example the steep gaps in the magnitude response are always extremely local by nature and hence should never be corrected by narrow peaking filters or such. As a result of the robust counter model designing algorithm of Anti-Mode 8033, the result is achieved with fully automatic process where the user is spared from the involvement.

The calibration program self-generates sweep-like measurement signals and picks up the data with included microphone. The process will autonomically define parameters of the room modes, such as center frequency, Q-value, gain, frequency antisymmetry etc. The DSP will further convert this data to complex zero-pole presentations into the Z-domain in order to derive optimal counter-model for the system. This will eventually lead to the designs of custom-fitted Anti-Modal Filters, AMFs. Up to 24 distinct AMFs can be designed, although far less are usually ever needed for one position. The extra AMFs give the algorithm more freedom when extending the effective area of the compensation for more globally improved results.

Furthermore, the DSP computes digital IIR coefficients for the AMFs to be used in real-time operation after the calibration. In computations, accurate 32/40 -bit integer arithmetic is addressed, which will virtually set unlimited space of parameters for the system.

In the operational mode the pass-trough delay of the signal is approximately 3ms. This is mainly due by converters and small enough to be inaudible. It can, however be taken care of with basically every A/V receiver on the market by adding distance of the subwoofer by 1 meter (3 feet).

Ease of Use
The Anti-Mode™ 8033 is very simple to use. The calibration process is completely automatic: it generates frequency sweeps to the desired calibration point (or multiple points) and measures the combined transfer function of the subwoofer-room system.

Compatible With Most Subwoofers
Anti-Mode™ 8033 uses regular RCA interconnects. It is inserted in between your preamp or processors line/sub out and the RCA inputs of your subwoofer.