Stereo and Home Theater System Setup and Calibration

Overview

System calibration refers to the process of maximizing system sound quality through setup of:

• Speaker positions
• Subwoofer positions
• Subwoofer polarity, phase, crossover frequency and slope
• Seating positions
• Room correction / parametric EQ
• Individual speaker levels and delays (home theaters and DEQX based systems)

Acoustic Frontiers has developed rigorous calibration processes for stereo and home theater systems based on our HAA certification, our experience performing calibrations for other integrators and our ground breaking white paper.

"The sound in the room has changed considerably; not only is the center image much stronger but also the soundstage is much wider and more encompassing. The subs are integrated perfectly and have illuminated the pace and rhythmic quality of the music...I was missing much more than I had ever imagined." Cesar Rubio, San Francisco, CA.

When we calibrate we are aiming to get a system's acoustic measurements and settings within quantifiable targets. Of course the items calibrated will depend on the system specifics. Calibration for a straightforward stereo system may only involve speaker placement whilst speaker, sub and listener positions may already be fixed in a home theater leaving only subwoofer controls, speaker levels / delays and EQ. Thorough documentation in the form of a Calibration Report will be created at the end of the process containing all settings, speaker / listener / sub placement and before / after acoustical measurements.

Process

Our calibration process is generally divided into two parts, corresponding to how the room behaves acoustically:

1. Bass Calibration (<250Hz)

Getting a flat bass response with even decay is critical to sound quality. It is very difficult and time consuming to optimize bass response using music, hi-fi test discs or Blu-Ray demos. We rely on high resolution frequency response and energy decay measurements to find the best location for speakers, subwoofers and listeners within the room, to properly integrate subwoofers and set EQ. Measurements cannot tell us everything, however, and the ears are a useful tool to fine tune system setup particularly when it comes to sub level and channel balance in a home theater.

Below: waterfall chart showing before / after results from application of room correction at 25Hz and 50Hz by Acoustic Frontiers. Notice that both the peaks in the frequency response and ringing in the time domain have been eliminated. These measurements were from a 9 seat dedicated home theater that we calibrated - see the full case study.

2. Soundstage Calibration (>250Hz)

Setting up the system to optimize soundstage focus and envelopment is done after bass calibration. Whilst the movements of speaker and listener to optimize bass response are large, getting the best soundstaging often requires movements of under 1". We rely on critical listening during this step, as we have found that the ears are the best judge of an optimized soundstage and a perfect balance between imaging / envelopment.

"I am thoroughly enjoying the new perspective on my system and music. The bass no longer seems heavy or dull; rather it fits into the picture more naturally. I enjoy the balance you’ve achieved between the focus on individual soloists and ensemble and the improved clarity and definition that I hear." Tim, Daly City, CA.

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