User17599786518076431468 (Customer) asked a question.
LFE response
I dont know if it can relate to Dolby but can someone explain clearly what do they mean with this part in the document ST2096 2017:
"If the response within the pass-band varies more than ±3 dB from a nominal flat response, and listening tests indicate that equalization is required, apply additional filters to correct for any major deviations in response so the result is within ±3 dB response tolerance in the pass-band 25 Hz – 120 Hz.
In some cases, the measured LFE response might have a definite peak rather than flat response across the pass-band. In this case, it is best to apply attenuation EQ to flatten the response, and adjust the overall channel gain to be within the target area tolerance, rather than applying boost to what appears to be a response deficiency. Boost-EQ on LFE/subwoofer systems is rarely effective, and can compromise headroom. To prevent over equalization of the subwoofer channel, some processors limit the available bands of equalization to as few as one parametric filter."
"If the response within the pass-band varies more than ±3 dB from a nominal flat response, and listening tests indicate that equalization is required, apply additional filters to correct for any major deviations in response so the result is within ±3 dB response tolerance in the pass-band 25 Hz – 120 Hz.
In some cases, the measured LFE response might have a definite peak rather than flat response across the pass-band. In this case, it is best to apply attenuation EQ to flatten the response, and adjust the overall channel gain to be within the target area tolerance, rather than applying boost to what appears to be a response deficiency. Boost-EQ on LFE/subwoofer systems is rarely effective, and can compromise headroom. To prevent over equalization of the subwoofer channel, some processors limit the available bands of equalization to as few as one parametric filter."
If the measured LFE response varies by more than ±3 dB between 25 Hz and 120 Hz, and listening tests confirm that EQ is required, filters can be applied to correct major deviations in the response.
If the measured LFE response has a definite peak rather than a flat response between 25 Hz and 120 Hz, the preferred approach is to attenuate the obvious peaks rather than boosting everything else. Boosting often fails to solve for acoustic cancellations and can result in reduced headroom, distortion, etc.
The standard also advises against excessive equalization. Pursuing a perfectly flat measurement through the use of multiple filters can introduce additional response issues that outweigh any potential benefit. Consequently, some cinema processors intentionally limit LFE EQ adjustments, encouraging users to correct only the most significant issues.
I also wanted to flag that our Discord community is an excellent resource for room calibration support. We have experts and other users who have firsthand experience with the process, making it easy to get advice, compare approaches, and troubleshoot issues: https://professionalsupport.dolby.com/s/dolby-creators-community
I’m taking notes right now
But the other thing I want to know, what is the most common either EQ filters or band pass filters (Hz, dB/oct) used on the LFE in most Dolby Cinemas ?
(even if I need to reach some sound engineers who worked on the Dolby Cinemas in AMC)