User16494405554694663261 (SoundNode) asked a question.
Sub-woofer calibration for Home Entertainment
In short, for home entertainment should one calibrate the sub to have +10dBs of in band gain, or not?
In long, there is conflicting information between the Dolby Atmos Entertainment Studio Technical Guidelina and the Home Theatre Installation Guidelines.
The technical guidelines it states clearly: "The subwoofer is aligned at +10 dB when compared to the center speaker, as per the SMPTE 202 specification, It should additionally be capable of producing at least 20 dB above reference level, which equates to a total of 30 dB above alignment level." which is perfectly clear.
However, on the Installation Guidelines it states: "Calibrate the subwoofer level to give the same level for redirected bass content from full-range speakers as those speakers produce in their pass bands." and there is no mention in the whole thing about the LFE being calibrated in anyway with the +10dB of in band gain.
So the issue is that if we as studios are mixing with the LFE at +10dBs (in band), with any bass management for the sub flat, and export content with such monitoring levels, when playing it back in a home entertainment system where the LFE and Managed Bass are both coming out of the sub and the sub is calibrated flat with main channels, then the +10dBs of the LFE will be lost.
So that's the pickle, and those +/-10 on the sub can make a big difference to a mix.
In long, there is conflicting information between the Dolby Atmos Entertainment Studio Technical Guidelina and the Home Theatre Installation Guidelines.
The technical guidelines it states clearly: "The subwoofer is aligned at +10 dB when compared to the center speaker, as per the SMPTE 202 specification, It should additionally be capable of producing at least 20 dB above reference level, which equates to a total of 30 dB above alignment level." which is perfectly clear.
However, on the Installation Guidelines it states: "Calibrate the subwoofer level to give the same level for redirected bass content from full-range speakers as those speakers produce in their pass bands." and there is no mention in the whole thing about the LFE being calibrated in anyway with the +10dB of in band gain.
So the issue is that if we as studios are mixing with the LFE at +10dBs (in band), with any bass management for the sub flat, and export content with such monitoring levels, when playing it back in a home entertainment system where the LFE and Managed Bass are both coming out of the sub and the sub is calibrated flat with main channels, then the +10dBs of the LFE will be lost.
So that's the pickle, and those +/-10 on the sub can make a big difference to a mix.
Let's start with your studio environment. I believe I understand the premise of your question.
We strongly encourage all customers to have a skilled engineer perform a room tuning for maximum performance and accuracy.
In a studio environment, we have individual control of the calibration of each speaker including the LFE. By using a real time analyzer, multiple mic setup, and a good quality pink noise, we can really capture by way of the RTA how much to adjust the LFE so that it is uniform with the center channel. We can apply x-curves to help guide us with the processing of each speaker eq.
When dealing with the LFE we can fine tune the correlation between the other speakers by using eq, amp gain, crossovers filters, etc. This maximizes the frequency response within a room and gives confidence to the content creator that their atmos system will perform correctly.
I added a screen shot of where the LFE is located vs another speaker on the x-curve using the SMAART RTA.
The home installation guide can only provide high level guidance due to the limited capabilities of any given AVR. As you know a living room listening environment can vary and AVR manufacturers treat LFE processing differently.
AVRs and Pre-processor already add the +10bd LFE boost by default in their signal flow (again, where this is in signal flow varies by AVR). There is usually an adjustable setting where the user can decide whether to keep it active or bypassed.
So the sub level should be matched to the other speakers at whatever level sounds subjectively good as the +10db for LFE is already taken care of.
If you are in need of a room tuning then we strongly suggest the use of our certified service partners. You can find them on this list. https://professional.dolby.com/content-creation/Dolby-professional-partners/#gref
Thank you for your patience and have a good day.
Jose.