To create consistency, each speaker in a Dolby Atmos mixing studio except the LFE subwoofer should be able to reproduce audio from 40 Hz to 18 kHz. However, sometimes it is necessary to use speakers which do not extend this far down into the low frequency region due to space or budget. To compensate for this, a technique called ‘bass management’ is used.

Bass management means that instead of sending a full frequency range signal to a speaker which can only reproduce say 100Hz to 18kHz, the frequencies below 100Hz are filtered out and redirected to a speaker that is designed to reproduce low frequency sound called a subwoofer, or sub for short.

Let’s take the example of 7.1.4 system which uses four relatively small speakers for overheads which can only extend down to 80 Hz. Here we would configure a monitor controller with bass management functionality to filter the signals destined for the overhead speakers such that audio from 80 Hz and below is filtered out and routed to a sub.

In terms of what sub speaker to redirect the bass to, there are options.

One common approach is to use the LFE sub for bass management in addition to replay of the LFE channel. This is a good option when budgets are restricted, and the sub used for the LFE channel has adequate power handling.

Another common approach is to use a single dedicate sub as per the above diagram. This is good practice to help ensure adequate power handling of the combined bass content from all the bass managed speakers.

This principle can be further extended to 2 or more bass management subs. This technique is useful to preserve the perceived direction of bass material in larger rooms where the speakers to be bass managed are spread out, or when you are managing the bass below a higher frequency such as 120Hz.

Another consideration is the channel count of your audio interface or monitor controller.  Adding bass management will add additional outputs, so for a 7.1.4 system you will need 12 for the 7.1.4 and an additional 1 for each bass management sub.

For more information on designing a Dolby Atmos mix studios see our technical guidelines article.