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Ambisonic loudspeakers provide front to back coverage for Hollywood theatre

The El Portal Theatre in North Hollywood has recently undergone an audio renovation with a complete STX loudspeaker system from Ambisonic Sound Technologies.

The 360-seat auditorium was built in 1926 and has hosted a long list of musical acts, but theatre manager Jay Irwin admitted that the room “Had always been a very challenging one for audio.” With its parallel concrete walls and lack of significant absorption, Irwin seemed to think he couldn’t tame the hall’s reverberant nature without compromising the classic art deco architecture.

Ambisonic CTO Tom Harrison commented: “Our line array products are uniquely suited for these types of highly reverberant spaces. The fixed-curve single-cabinet arrays produce high-output levels with audiophile sound quality and tightly controlled vertical directivity for more direct versus reflected sound and superior speech intelligibility.”

To provide the clarity and coverage needed for a theatre of this shape and size, the system design started with one array on either side of the stage consisting of an STX6620 and STX4625 line array loudspeaker in each array. The 6620 Articulated Column employs six of the company’s advanced Planar Magnetic Ribbon Driver (PMRD) tweeters that are coaxially-aligned with a neodymium magnet-driven 6.25in mid-woofer. The 4625 is a smaller array with four of these coaxial driver pairs in a greater articulation.

Utilising Ambisonic’s Array Optimization System (AOS) software to model the system and seating area indicated that the system needed an additional STX4625 array cabinet to cover the front audience area. The AOS allows the system designer to see exactly how the loudspeaker output and coverage pattern will reach the audience. In the case of the El Portal’s steep stadium-style seating, this additional line array cabinet was needed at the bottom of the array to increase the vertical coverage required for even SPL from the first row to the last row.

Both the 6620 and the 4625 speakers have proprietary Waveguides for the tweeter and mid-woofers that increases the horizontal coverage pattern to 110°. Combining this wide dispersion with the Line Array’s ability to provide even coverage from front to back to within +/- 2dB.

A DRM212 woofer cabinet was flown with each array to increase low frequency output and overall system dynamics. The two 12in woofers in each cabinet improve the integration between the flown arrays and the two DRM215 subwoofers that are installed under the stage. The DRM215 subwoofers add a total of four 15in, high-output subwoofer drivers to contribute deep low frequencies at high volumes.

Manager Jay Irwin adds: “The sound is amazingly even throughout the house, so that every audience member hears the same exact thing, from the front row to the back row it sounds exactly the same. The speakers have punch and excitement, but never seem harsh or brittle. They have a wonderfully organic and natural sound.”

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