HPV Technologies Inc.
Wednesday, January 26, 2022

FAQ: Surface Arrays

Frequently Asked Questions..
MAD's Surface Arrays

     What is so special about MAD Planar Magnetic Surface Array?

          The MAD Array uses Planar Magnetic Transducers which are the best sounding devices currently available for sound reproduction.  Planar Magnetic technology has been around for nearly 90 years.  Until recently, this technology was associated with the high-end home loudspeaker market.  Although the sound quality was extraordinary, there were some big limitations which kept it out of the professional market...namely that the transducer's price was too high and the efficiency was too low. 
          In 1999, HPV Technologies was the first company in the world to overcome these limitations when they introduced their first planar driver to the high-end, professional sound marketplace.  The MAD technology pioneered by HPV removed many of the inherent design problems in today's conventional speakers.   For example, the MAD Planar Magnetic Surface Arrays are one-way (full-range) loudspeaker system that can operate from 60 Hz to 18KHz.  This means the entire signal processing and amplifier system can be simplified resulting in lower costs compared to conventional three or four-way systems.

          The MAD Array is full-range and only requires high pass filters. There are no crossover and phase issues in the critical voice region. Many singers who have used the system said that this is the first time they can hear their "true" voice as it is supposed to sound.

          The MAD Array has a huge radiating surface.  This enables excellent air coupling to the transducer diaphragms and high efficiency.  The transducers use very lightweight stretched diaphragms and very strong neodymium magnets which drives the entire diaphragm surface with incredibly strong and uniform forces.  That's why the MAD Array can plays at such loud volumes with so little distortion.  Now for the first time, people can listen to very loud volumes for long periods without the usual fatigue and ringing of the ears.  For example, in the Arco Arena in Sacramento, California it is possible to achieve 115-117 dB Sound Pressure Level with clear, undistorted sound even in the most distant seats with peaks of 127 dB.  Transient response is extraordinary and the intelligibility is so good that the audience can hear and understand every single word even in rooms with poor acoustics. 
     What is the size and weight of the Array?

          Each HPV transducer is only 3/4" thick and weighs 4lbs. An entire A9 Array (8 rows) ready to fly weighs only 520 lbs. Rigging of the array is extremely easy and does not require special or very expensive construction work to be hung. Because of the very small size and weight, transportation is extremely cost-effective. For example, the whole Arco Arena array system can fit in a standard cargo van.
     Is the MAD Array a "line" Array?

          Yes, but it's performance goes way beyond the traditional line arrays...so it's more accurate to say that the MAD Array is a
Planar Magnetic Surface Array.  The Surface Array characteristics produce substantially better control in vertical and horizontal directivity when compared with conventional line arrays.  However the most significant improvement that the Surface Array provides is it throw capabilities.  Sound attenuates from Planar Surface Arrays at only 1½ dB per doubling of distance compared with 3 dB with conventional line arrays.  This allows MAD Arrays to project sound hundreds of feet farther away without losing sonic details.

     How can severe weather conditions affect MAD Arrays?

          The MAD Array is very resilient to most weather conditions and can be used in virtually any environment.  MAD systems are in regular use in extreme conditions  ranging from hot and sandy deserts to humid, salt water marine environments.  These Arrays are not susceptible to humidity, although it is not recommended to have it directly exposed to rain during operation.  However the arrays can be used in the rain if covered with a loosely attached plastic sheeting. 
     What about Power Compression?

          Power compression doesn't exist because the transducer's coil temperature is always below 100°C and the coil's resistance changes very little.
     What is the Frequency Response of your Array?

          The frequency response for an array with 12 rows or more is from 60 Hz to 18,000 Hz.  A high-pass filter above 60 Hz, 24 dB/octave or higher will be needed if the array is used without subwoofs.  If a very high SPL of low frequencies is required below 60 Hz we suggest coupling subwoofs with the A8/A9 array.  Recommended crossover points would be 80Hz to 120Hz using a high-pass filter with the slope of 24 dB/octave or higher.
     What is the Power Handling capacity of your arrays?

          Power handling for one A8 is 640 watts RMS.  Power handling for one A9 is 720 watts RMS.  An 8 row, A9 array is 7200 Watts RMS.
          By using bigger drivers we have created a very simple, full-range system that is extremely reliable and, when properly match to amplifier power and setup with the correct DSP, almost indestructible.  Distortion levels will always remain very low, well within the operating range of the amps.
     What is the horizontal and vertical sound dispersion?

          The horizontal dispersion in the A9 array is 90° at 10KHz and 120° below 5KHz.  Vertical dispersion is adjustable and it can be set from 0° to 80°(in an 8 rib array).  Splaying angles between adjacent rows can be made from 0° to 10° in four fixed increments of 2½°.  Custom array designs can achieve any dispersion angle in both horizontal and vertical plane, from 0° to 360°.
     What about "Phasing"?  What am I hearing when I walk around your array?

          MAD Planar Magnetic Surface Arrays configured with proper EQ have almost linear phase within the working frequency range.  When the phase vs. frequency is plotted on a linear frequency range scale you will see a flat line which indicates that there are absolutely no issues with phase.  The sound response is very coherent.

          The MAD arrays are built with 6" x 9" full-range, planar magnetic transducers. Due to diaphragm size these transducers are very directional and above 4-5KHz dispersion pattern starts to narrow down.  For example, at 10KHz, the horizontal dispersion angle is only 15° (i.e. +/- 7.5°) while vertical angle is only 10°(i.e. +/-5°).  As you go higher and higher in frequency, transducers have narrower dispersion angles.  In the A9 array, the horizontal splay angle is ~11.25°.  At frequencies above 8 KHz, the dispersion patterns from adjacent drivers don't overlap completely and you can hear small variations in SPL (perceived as slight notches) as you move horizontally across the array.  This is especially noticeable if you're listening in near field within a couple of meters from the array.  However once you are listening in the far field, the perception of these "notches" go away.   Notches are frequency dependant and they become more apparent at higher frequencies above 10 KHz.  So what we are hearing is not a "phasing" issue, but rather the directional properties of individual drivers coupling together.

If you move far away, this problem is minimized and barely noticeable. This phenomenon happens well above voice range and with the program material it is quite acceptable.

          •   For more technical information on Planar Magnetics operates, click here.