Major fundamental problems exist in previous room-correction systems. Some devices take an acoustic snapshot, compare the input and output, subtract the difference and then add it back into the input in a polarity-inverted fashion. That would work if it were a steady-state matter and didn’t create a huge error in the time domain. The measurement is also totally dependent on the sample window. If we were to take twenty different sample measurements from the same burst source just 1 millisecond apart, we would get twenty different correction solutions as the reflections arrive at the microphone.
Other systems ask you to make measurements at up to six different locations. However, the person close to the sidewall experiences dips and peaks at different frequencies than the person in the sweet spot. Homogenize this data and the time domain information is destroyed. Temporal cues are lost and neither listener position is optimized. Another method is intended to be precise for a single listener position. It uses a cancellation technique fixed to a set path to the listener. It requires the listener to maintain a relatively static head position. The system does not recognize or treat room resonances, and actually increases errors apart from the listener location.
Not surprisingly, each of these methods results in an unevenness or unnaturalness in the sound about the room. The Bohmer method captures the wavefront as it is building in time. It collects a more useful and accurate sample over a longer period and distinguishes between direct sound, reflections, early resonances, and later resonances. Measurements are made closer to the speaker and over an extended time interval to detect how the acoustic waves are actually building in the path toward the listening area.
There are the resonances associated with the room’s physical dimensions that are relatively slow-developing phenomena more loosely connected to speaker output, and there are resonances due to the loudspeaker’s relatively close proximity to the room’s walls, floor, and ceiling that are intimately connected to loudspeaker output and behave completely differently.
Cordesman Assessment of Impact on Sound: I’ve lived with a wide range of other room-correction systems, and used TacT, Meridian, DSPeaker, and Audyssey units in my reference system at different times. I experienced set-up problems in each case, and at least some of the listening problems that Bill Dudleston highlights—which include quite measurable changes in the bass response with surprising small shifts in microphone position, or listening position, or height or width—and even in room correction when the frequency range of the room compensation is limited to lower frequencies and correction of dips in the response is also limited.
All of the better competing room-correction devices I’ve tried could be made to work well in dealing with serious bass-response problems, but their time and phase correction seemed somewhat problematic with really good, natural, acoustic music recordings and systems. In practice, they often work quite well with soundtracks and videos, but the sound is not as clean with most speakers as the sound without correction can be from speakers that are time-aligned and have minimal phase problems.
The Wavelet-Legacy V system did better in all respects than any other DSP system I’ve tried. I’m far from certain that this aspect of audio will not see further major improvement over time, but you can’t buy or hear the future now. And, the firmware upgrade features of the Wavelet mean that such progress may end up being only one download away.
Explain the impact of the Wavelet’s Bohmer Correction eliminating unwanted delayed signals in terms of the music listening experience.
Dudleston: As music is pressure amplitude varying over time, the less time smear, the better the sound will be. Timing distortions weaken the musical message. If the speaker’s ability to stop is improved it will invariably become a better speaker. The Wavelet improves the speaker’s ability to stop.
The corrected speaker sounds clearer, has higher resolution, better transient impact, and more accurate timbre, and generally conveys the emotional message of the music to a higher degree. Which one of these properties you notice first will depend on your personal listening biases, but they are all present and closely connected to the time domain behavior of the speaker.
Furthermore, with the Wavelet’s Bohmer Correction you don’t have artificially added time smear that’s usually present with other room-correction systems. This smearing obscures the musical message. Usually this artificiality manifests itself as a lack of ease. Sometimes you can’t quite put your finger on it until it is removed.
A properly corrected speaker system will produce an even soundfield throughout the entire listening room with improvements to the time domain manifesting themselves as enhanced clarity, resolution, transient response, and timbre across the space. The improvement is easily verified by walking around the room. It is not a subtle effect because errors in the speaker/room interface are not small. Once experienced, your brain becomes critical of uncorrected systems and the lingering transients. The sonic result is smooth and natural-sounding without artificial color.
Cordesman Assessment of Impact on Sound: I would again agree in regard to the room-correction systems I’ve lived with, but here I want to reinforce the qualifications I just made earlier. I’ve scarcely heard every option, and it has been some time since I’ve heard the latest Audyssey and Meridian systems.
Good as the Wavelet and Bohmer corrections are, I’ve also heard speakers like the Wilson Audio Alexia and YG Acoustic Hailey perform competitively in the same room in my home with really good conventional audio components and proper setup and speaker location. I’ve also heard the latest Vandersteens and Magnepans provide further demonstrations that sonic clarity and excellent performance are not room-correction dependent.
Those qualifications made, I was truly impressed with what the Legacy V could do in making subtle improvements in the realism of imaging, the definition of image size and depth, the smoothness and clarity of the bass with a wide range of classical music and acoustic jazz, and not simply with modern recordings.
I found this out listening to a Bernstein recording of Beethoven’s Sixth Symphony when I casually turned the Wavelet’s room correction off just to hear what would happen. To mix a metaphysicism, the result was scarcely the musical difference between night and day, but the improvement in overall clarity was immediately apparent. The same later proved true with Modern Jazz Quartet recordings and many others—including the Eagles, Stones, and Jennifer Warnes.