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Hendon Publishing

Lund PASS Push Bumper & Siren

The problem is that motorists today driving modern, air-tight cars with the windows up, the A/C on and the radio on, all while talking on a cell phone, don’t hear even a full 100 watt siren until the last moment. The siren speaker mounted under the hood, wherever it will fit, makes a muffled, baffled and diffused audible signal. And the available space under the hood, and behind the grille, is getting smaller.

If placed directly behind the grille, the speaker restricts airflow to the radiator. Even if the speaker is mounted on the push bumper, the sound from a traditional speaker emits in all directions. That means upwards towards the sky and downward toward the pavement, neither of which is where the motorists are.

A solution is the Lund “Police Audio-visual Safety System” (PASS), which is far more than a mere push bumper with an integral siren. The Lund PASS uses two siren speakers, one in each upright of the push bumper. The installation into push bumper is patented. The speakers are normally used together but can be used separately. The best performance, of course, of the 200 watt output comes when both speakers are used together. Importantly, one speaker can be used for the traditional wail-yelp, while the other runs a low frequency signal. Also, one can be used for the air horn, while the other maintains the traditional siren signal.

Lund Industries developed a proprietary tall and narrow horn design for the siren speaker. That is the key. When sound waves exit the speaker of this design they turn 90 degrees. This vertical mounting causes the sound to flatten horizontal and radiate outward. The best comparison is to the traffic radar beam, a flat signal that radiates forward. As such, the Lund PASS gives a much stronger off-axis (intersection warning) signal than a conventional siren.

Sound intensity is logarithmic, not linear; it doubles with every 3 decibels (dB). At 97 (dB) from 100 feet in front of the car at the motorist level, Lund PASS is 15 dB (more than 32 times) “louder” than the 82 dB standard siren. Increasing the distance greatly reduces the warning signal from all sirens. However, at 200 feet, the Lund PASS is still 14 dB louder than a standard siren. Importantly, the PASS is 8 dB louder (almost 8 times) at a 45 degree in front of the car for intersection clearing.

We compared the sound output from the same Ford CVPI upfitted with both a behind-grille, FedSig DynaMax and the Lund PASS. The differences between the two, first one, then the other, were stunning. Both the sound level (loudness) and the sound quality (tone richness) were dramatically different. The ability of any siren to effectively warn motorists is so limited, any improvement is a huge improvement. Especially if the gains are made in intersection warning.
The aluminum Lund PASS with steel backing plates and a rubberized leading edge weighs 32 pounds. Pre-punched holes accept both side and front LEDs, and a 13-wire harness is available. The PASS can be easily swapped between different vehicles. The only difference between a PASS for a Ford CVPI and a PASS for a Dodge Charger is the outer plate on both sides and the mounting kit.

The Lund PASS is available for the Ford CVPI, Explorer, Expedition and F-150; the Chevy Impala, Tahoe, Suburban and Silverado; the Dodge Charger, Ram and Jeep Grand Cherokee. The dual speaker PASS for the Charger, for example, has an MSRP of $997. Even if you never push a disabled car, a push bumper offers protection for the front fascia, headlights and grille. And the Lund PASS has twin speakers. You really do have to hear the difference to grasp the significance of the Lund PASS.

Published in Police Fleet Manager, Nov/Dec 2010

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