The playback level a reference is critical if the mix is to translate from one production house to another and audiences are to hear the director’s intent in terms of the balance in the soundtrack.
These are including dialog, effects, and ambiance. Reference level for all channels is excepting low-frequency effects and it is calibrated by adjusting the audio chain such that a pink noise signal recorded at -20dB relative to full scale (0dB) creates an 85dB sound pressure level as measured with a C weighted SPL meter at the seating locations.
Volume levels are adjusted for each channel individually until and they are reading 85dB. Explanation of reference level means two things for home theater design.
Capable of 105dB peaks
If the playback reference level dB chain is calibrated to produce 85dB for a -20dB signal at the listening position, then the speakers and amplifiers could be asked to produce 105dB for a 0dB signal.
It is a challenging proposition for an audio system to reproduce this level cleanly, without dynamic compression and to be able to do so reliably.
Most standard consumer technologies such as soft dome tweeters are not up to scratch in any reasonably sized room.
Speakers should have high sensitivity and high power handling, such as the Porcello Audio speakers we recommend and use.
Subwoofers must be capable of 115dB peaks
The low-frequency effects channel is handled slightly differently and has a 10dB boost relative to the other channels.
The maximum SPL that subwoofers could be asked to reproduce from the low-frequency effects track is therefore 115dB at the listening position.
These challenges are typically needed to be able to properly reproduce the soundtrack as the director intended.
Other speaker channels have been diverted to the subwoofer. In-home audio-video receivers (AVRs) and pre-processors, this is done by setting the speakers to small in the bass management menu and specifying a crossover frequency.
An 80Hz crossover is typically used. This is meaning any content in the surround channels under 80Hz is essentially diverted to the subwoofer.
For 5 bass managed speakers an additional 6dB and for 7 basses managed sneakers basses an additional 8dB of output may be required from the subwoofer channel.