ISP Pro Audio


Four-way line array element of the highest performance and fidelity.

Two 12 inch woofers, two 6.5 inch horn loaded lower MF, two 3 inch horn loaded HMF compression drivers, four 1.75 inch horn loaded HF compression drivers with mylar diaphragms.

Precision lenses for seamless HF coverage with “air.” Elements available with vertical coverage of 5 degrees. 6 channels DCAT™ amplification (2000 watts RMS total power) per box. The HDL 4210N will pin under the HDL 4212 cabinets for nearfield application.

The ISP Technologies HDL 4212™ speakers are a 4-way line array box of the highest performance and fidelity. The HDL 4212 is a 5-degree vertical box.

ISP Technologies is the only manufacturer to offer the True 4-Way Line Array Technology design (the Clair I-4 is a proprietary 4-way box, but the 4th ‘way‘ is a built-in subwoofer). All other line array boxes are 2 or 3-way (the Meyer Milo is three 1/2-way, in that both 12-inch woofers operate below a certain frequency).

A 3-way line array box is compromised in terms of its off-axis midrange smoothness, since the cone midrange drivers must cross over to the HF drivers at 1.2 KHz, typically. At this high of a frequency, the off-axis path difference between the two midrange driver lines is easily in excess of 1/2 wavelength, leading to a 6 dB or more dip in response in the middle of the midrange. This is on top of the response dip in this range due to the line curvature and cone breakup. The result is that most line arrays suffer from midrange ’suckout’.

The ISP Technologies boxes cross over at 800 Hz from the lower midrange cones to two special midrange compression drivers. At this lower frequency the wavelengths are longer which reduces the path difference at 45 degrees to less than 1/2 wavelength, resulting in a less audible dip. The result is more consistent midrange over wider angles, with greater clarity on the voice.

In addition, 3-way systems must compromise on the high frequency end since the typical 1.2 KHz crossover frequency requires use of a large-diaphragm (3-inch or 4-inch) driver. These large diaphragm drivers have either extreme high-frequency roll off and loss of efficiency, or extreme dips and peaks in the 10 to 15 KHz region due to diaphragm breakup (very annoying to listen to). The 2.7 KHz upper crossover in our 4-way box allows use of a 1.75-inch diaphragm driver, which features response past 18 KHz. The extremely powerful neodymium magnets in these drivers result in a sensitivity of 108 dB @1W/1M out to 18 KHz, which is simply the best performance of any driver by any manufacturer we are aware of! The use of four of these drivers per box minimizes distortion and maximizes output.

In addition, the boxes are carefully designed with the aid of our proprietary LINESIM™ simulation program to achieve smooth response at all frequencies and listening positions when used to our recommendations. Competing boxes of this output capability are as little as 3 degrees, requiring more boxes.

Made with Baltic Birch

Configuration: 4-way
LF Drivers: 2 x 12 inch, very high sensitivity, neo magnet, reflex loaded
LMF Drivers: 2 x 6.5 inch, very high BL, horn loaded
HMF Drivers: 2 x 3 inch compression, low moving mass, horn loaded
HF Drivers: 4 x 1.75 inch compression, very low moving mass, horn loaded, polyester diaphragms
Coverage: 5 V x 90 H (-5) Splay Angles: 1 to 5 degrees (-5)
Frequency Resp: 68 Hz (4 boxes) to 18 KHz
Construction: Baltic birch plywood
Dimensions: 43.5” W x 15” H x 23” D (without amp)
43.5” W x 15” H x 27.5” D (with amp)
Weight: 150lbs. (without amp) 185lbs. (with amp)
Amplifier: 2000 W RMS, 4 channels, high current DCAT™, fan cooled
Power Required: 10 Amps x 120 VAC
Crossover: Outboard digital processor required which is capable of 5-way crossover.
Rigging: 18 boxes @ 7:1 safety factor, aluminum alloy
System Capabilities
The system was modeled using our proprietary LINESIM™ program to predict the performance. This program performs extensive calculations based on the position and output of each driver to predict the sound level at multiple frequency bands from the first row to the last row. The system exhibits outstanding balance in all frequency bands. Below are the continuous output capabilities of four 6-degree boxes of the system in each frequency band, normalized to 1 meter distance:
LF: 141 dB @ 1m, 100 Hz to 280 Hz
LMF: 140 dB @ 1m, 280 Hz to 750 Hz
HMF: 148 dB @ 1m, 750 Hz to 2.7 KHz
HF: 149 dB @ 1m, 2.7 KHz to 17 KHz
Related Links
No HDL 4212™ Product Manual is currently available
HDL 4212™ Cut Sheet
ISP Pro Audio Products Brochure Rev. 01.12