HAA System Performance "Report Card" for Home Theater

The Home Acoustics Alliance has developed the Acoustic Design Review and System Analysis for Home Theater to be a review of design and performance. Whether you are seeking improvements in an existing system or building a new one, the Report Card provides the framework for doing it right. The various "Elements" that outline this framework are reviewed by the acoustical calibrator and graded based upon how well they conform to industry standards. The calibrator then has the information necessary to proscribe the required changes to bring performance up to its best. The final analysis of performance is then summarized in a concise System Performance Report judging performance based upon our fundamental acoustical goals (see below). These goals are common to to all home sound systems. If your current AV Contractor is not HAA Certified, many consumers will hire an HAA Calibrator to review a proposed design as an outside consultant.

Clarity

Clarity is the prime acoustical goal because its perfection depends on the successful attainment of all other goals. Of paramount importance is dialogue intelligibility in movies, but one must be able to understand musical lyrics, detect quiet background details, and sense realism for acoustical sounds. Elements that affect this goal are varied including equipment quality, room reverberation levels, ambient noise levels, and listener position among others.

Focus

The ability to precisely locate each reproduced sonic cue or image in a three-dimensional space is defined as acoustical focus. Recordings contain many such images superimposed side to side and front to back in every direction for 360 degrees around the listener. A system is said to have pin-point focus if, from the perspective of the listener, each of these images is properly sized, precisely located, and not wandering. Good focus also provides that individual images be easily distinguishable from amongst others within the limits of the recordings quality.

Envelopment

An audio system should reproduce virtual images of each recorded sound presenting the listener with its apparent source location in a three-dimensional space. Each sonic image relates a part of the recorded event and together these sounds compose a wrap- around soundstage that envelopes the listener. Proper envelopment requires that the soundstage be seamless for 360 degrees without interruption by holes or hot spots caused by speaker level imbalance or poor placement. While envelopment requires three-dimensional imaging of all sonic cues, of pivotal importance is the realistic recreation of the ambient sound field of the recorded venue. Focused sounds become more realistic as they move side to side and front to back with the backdrop of the ambient sounds of the intended venue.

Dynamics

Dynamics is simply defined as the difference between the softest and loudest sounds reproducible by a sound system. While much emphasis is placed on the loudness side, it can be shown that the audibility of the softest sounds is an equal measure of system performance. Among the acoustical requirements for proper envelopment, focus and clarity is the necessity of hearing the sonic cues relating these qualities. If they are overwhelmed by excessive ambient noise or reverberation in a room, they are not properly audible. At a minimum, a system must be capable of reproducing loud passages with ease and without excess while soft sounds remain easily audible.

Response

The frequency response of a system is a measurement of the relative levels of all reproduced audio frequencies. The smoothness of response can be observed in a variety of ways; as improper tonal balance including boomy bass, excessive treble, improper musical timbre, or a general lack of realism. Factors of importance include selection of high quality components, and proper system set-up including (in a small room) proper listener position, speaker position, and correct use of equalization. At a minimum, the system must be non-fatiguing all sound levels, articulate and faithful to the original signal.