ESSENTIAL CEDIA

SHIFTING SANDS IN CINEMA

There has been a paradigm shift in attitudes towards engineered entertainment space design. Peter Aylett, partner at HTE Acoustic Interior Design and CEDIA volunteer, explains.

The design of high-performance entertainment spaces is - regardless of the use mode of the room, an engineering exercise. Almost every aspect of performance is predictable at the design stage and verifiable at commissioning. Unfortunately, the approach currently taken by many dealers is to bypass design and engineering, going straight from sales to specification. Though many engineering standards currently exist for the design of entertainment spaces, they are a combination of fragmented, dated, format specific, product specific and bias towards commercial cinema.

CEDIA’s current CEB22 ‘Home Theatre Audio Design’ Recommended Practice was published in 2009 and whilst still relevant, does not include multiple advances since then. The new RP22 ‘Multichannel Audio Room Design’ Recommended Practice not only updates CEB22 but adds many new sections to make it a far more complete and holistic design guide.

New and completely updated sections include –• A recommendation for speaker layout rules that embrace all the current format providers, and provides guidance for high channel count systems • New acoustic design recommendations • New recommendations for loudspeaker specification • New recommendations for the use of acoustically transparent materials (including different screen materials)

• New recommendations for the use of electronic electro-acoustic optimisation (EQ) • Updated recommendations for multiple subwoofers to mitigate room modes • New performance objectives section • New visual T.O.C. and design process section • New recommendations around seat-to-seat consistency • Updated recommendations for background noise and acoustic isolation The biggest change in RP22 from the old document is the introduction of new performance levels. Whilst the old document only described ‘Reference Level’ and even then, this was just a description of maximum SPL capacity, RP22 will define four different levels of performance. Level one is the new baseline definition for a system to convey a minimum level of artistic intent from the content creators. The new level four is a no compromise definition of ultimate performance that sits above ‘reference’ which is now level three.

RP22 is a design document, so all the performance parameters are predictable at the design stage and will be verifiable after commissioning. Examples of these parameters include separate screen speaker and non-screen speaker SPL capability, in-room bass extension and subwoofer(s) SPL capability across their usable range, decoder/renderer capability and discrete speaker array, level of early reflections relative to direct sound, room RdT(RT60) time from 62Hz to 8KHz, and speaker location deviation from the recommended positions.

Performance levels will for the first time allow the industry to have conversations around objective performance rather than product and brand rhetoric. For installers, it will bring a level playing field to cost proposals that are engineered to performance levels. This will help bring an end to the practice of ‘I can do that system for half the price’ because integrators can justify the performance of their proposed system using objective metrics. RP22 has also removed all references to room use modes such as ‘Home Theatre,’ ‘Cinema,’ or ‘Media Room’, as the performance of the system should be considered independent from a room’s use mode. This will allow integrators to have far more flexible conversations with clients rather than the binary ‘cinema or media room’ question.

RP22 is being created under ANSI rules by a global workgroup made up of some of the most experienced audio video practitioners in the world. The document will not be ‘opinion’ but will be the result of over two years’ worth of deep discussion and detailed peer review.

Being created right now, RP22 is designed to take entertainment engineering to a new level ‘Standards enable consistency of experience’ Poppy Crum, Chief Scientist at Dolby Labs.