We achieve linearity of the high frequency drivers by a method that I developed in Switzerland, for which we hold a patent (Horn Speaker and Method for Producing Low Distortion Sound, U.S. Patent 4,152,552). The method uses a very light, aluminum alloy, tempered dome mounted on a high-compliance suspension, allowing the air load of the horn to control the movement of the dome in the compression driver. This technique drops the distortion caused by the non-linearity of air, however, it causes ripple in the frequency (magnitude) response. The standard low-compliance method used on compression drivers damps out the ripple at the cost of higher distortion. This means that we have to correct the amplitude response for our drivers using complimentary filters.
The protection of a high-compliant driver is also more complex – one of the main reasons we decided to make the loudspeakers self-powered. The low frequency drivers use different methods of achieving linearity depending on the application. For lower powered systems such as the HD-1 studio monitor, we use a traditional hi-fi technique – a long coil in a short magnetic gap with a high-compliant suspension on the drivers. The electronics of the HD-1 have a fiftieth-order correction in order to achieve a good magnitude and phase response from the system (Correction Circuit and Method for Improving the Transient Behavior of a Two-Way Loudspeaker System, U.S. Patent 5,185,801). The method used for the X-10 loudspeaker is a high gain servo system using a short coil in a long magnetic field. This makes for a very heavy magnetic assembly and very complex electronics.
For PA products we use a quite different method than that of the professional audio industry. Loudspeakers used for sound reinforcement have to produce high sound output, therefore the loudspeakers have to be efficient and high powered. Starting in the 1970’s, PA companies began using high power, music-type loudspeakers for PA, and though they produced a great deal of distortion, they were loud. From 1972 to 1978, I worked on improving the linearity of these highly efficient loudspeakers, and in 1978 I discovered that we could balance out the non-linearity of this kind of loudspeaker. The proprietary processes we currently use in the manufacturing of our own transducers are based on the research I did in the 70’s. Everything has to be strictly controlled with very tight tolerances in the fabrication and assembly path.
The linear excursion of these transducers is low, so we need more cone area to produce the sound levels we need. For example, the 15-inch driver in the X-10 can move P-P a full inch and produces as much sound power as two of our low excursion 18” drivers. That’s why we developed the dual 18-inch sub – to use a larger area rather than long excursion.
TruPower limiting from Meyer Sound protects loudspeaker components without compromising system performance. The TruPower system is the first limiting technology that accurately measures power dissipation inside a loudspeaker, limiting power only when absolutely necessary. This allows the loudspeaker to deliver maximum dynamic volume, safely and consistently.
The technology works by sampling the voltage and current at the output of the amplifier and by using an analog multiplier to calculate the true power being sent to the speaker to control the limiting.
All of Meyer Sound’s self-powered loudspeakers can reproduce “pink noise,” which has a peak to average of 12 dB. Most of the self-powered loudspeakers have a 15 dB peak-to-average level. In our MAPP Online (Multipurpose Acoustical Prediction Program) software, the peak is based on the ability of the loudspeaker to reproduce pink noise, where on the datasheet it is the measured peak of the loudspeaker using music, without engaging the peak or power limiters.
We use analog phase networks to control the cardioid behavior of the M3D and the M3D-Sub.
We have received a patent for the REM manifold. You can read more about it here. In short, REM takes the output of the compression driver and channels it into an iso-phase line array. It does this with a lower distortion method compared to other line array techniques.
The electronics in MILO solve several problems. First, there are the crossovers that separate the highs from the lows. We do this by using low-order filters ranging from elliptical to Bessel.
Low-order filters, of course, have lower phase shift than high-order filters. For example, using a 48 dB per octave Linkwitz-Reilly filter for the crossover, the frequency amplitude response will be flat, but the phase response through the crossover area will produce several milliseconds of delay for over two octaves around the crossover frequency. This kind of high-order filter makes it more difficult to phase-correct the overall system response.
Since we use high-compliance drivers, over-excursion has to be handled by special circuits for this purpose. TruPower limiting circuits protect the drivers from burning up without introducing any power compression. There are also filters to remove the amplitude ripple, and filters to correct the system phase response to less than +/– 20 deg from 800 Hz to 14 kHz. This is far better than any other line array system we have measured.