This article will explain what Bass Management is and how it works with Symphony Studio. We'll also explain what LFE is and what its role is. Finally we'll talk about Room Correction and how this all ties together.
Take me to the bass management tutorial for Symphony Studio.
What is Bass Management?
Bass management is the process of redirecting low-frequency content (typically below 80 Hz) from satellite channels to one or more subwoofers. The idea is that some (ceiling speakers for example) or all of the speakers in an Immersive setup might not be able to reproduce frequencies below 80Hz accurately. The redirection happens by way of a crossover that essentially splits the audio into two signals - one signal that goes to the (satellite) speaker and one signal that goes to the subwoofer. The crossover is comprised of a High Pass Filter that passes audio to the speaker and a Low Pass Filter that passes audio to the subwoofer.
The Crossover takes the LowPass signal from each channel and passes it along to a summing circuit (∑) that adjusts for volume and sends it along to the Subwoofer.
This illustrates Bass Management, using a spectral display of audio going to a speaker and audio going to a subwoofer. This really explains it visually and is best viewed in fullscreen - that little square in the lower right hand corner.
When or where is Bass Management used?
The concept of Bass Management for home theater was introduced in the early 90's. The concept, as described above, was to enhance the home theater listening experience, first for Laser Disks and then DVD's and beyond. The Bass Management itself was done by the A/V receiver. Read more about A/V receivers here: Audio Video Receivers
Technically, in professional environments, Base Management is optional, either completely On or OFF or selectively ON for some speakers and OFF for others. For example, you may have big full range speakers for your Front Left, Front Right and Center channels and don't want any filtering done on them, while still Bass Managing your surround or immersive speakers. The important take away is that it is assumed that when an end user is listening to an immersive mix on speakers, the system will be Bass Managed. Either by an A/V receiver or sound bar system.
What is LFE?
There is often confusion with regard to “Subwoofer” and “LFE”. To put it simply, a Subwoofer is a speaker and LFE is a band limited channel. LFE, short for Low Frequency Effects, originates from Audio Post Production for Cinema starting in the 1970's and was invented to “add oomph” to explosions and other sound effects without taxing the main speakers. So, while Bass Management is a method of redirecting very low frequency information from your speakers to the Subwoofer, “sending” content to the LFE (which is routed directly to the subwoofer) is a conscious aesthetic decision. Using LFE in the mixing of music is a topic that has been discussed for many years and is considered optional.
Note that in most Surround or Immersive speaker systems, the subwoofer handles both Bass Management and LFE duties. It isn't until you get to large dub stages where films are mixed, and state of the art Movie Theaters, that you encounter multiple, separate subwoofers that are designated for either bass management or LFE.
If you want to know more, this paper from Dolby written back in 2005 about 5.1 music production, contains information about Subwoofer and LFE that is still relevant today. Dolby 5.1-Channel Music Production Guidelines
How do I set up Bass Management?
If you have an Apogee Symphony Studio you already have a bass management system available to you. If you have an Apogee Symphony I/O MkII Thunderbolt there is a tutorial on how to use Ginger Audio's Sphere v2 with a Symphony I/O MkII Thunderbolt HERE.
Using Bass Management with your Symphony Studio
Open Apogee Control 2 and from the System Settings sidebar, select Monitor Workflows.
The Monitor Workflows window opens up. From here, select your immersive speaker layout on the left and click on the Bass Management tab.
Here you will see all of the speakers in your system except for the Subwoofer. You don't see the Subwoofer because this is the page that determines what is being redirected TO the Subwoofer. By Default Bass Management is OFF (white).
With Bass Management turned ON (purple) lets take a closer look.
These are the default Bass Management settings. The Purple squares indicate that the speaker is being Bass Managed, you can have them ON (bass managed) or OFF (no bass management). Here you can also set the crossover frequency, the filter slope of the Crossover and you can trim the amount of signal going to the Subwoofer.
These can all be adjusted to taste, but the best practice is to measure and correct your room. There are several ways of doing this. The first option is using the built in Room Simulator Function in the Room Correction page of the Monitor Workflows module.
What is Room Correction?
Room correction refers to the process of adjusting the sound of a speaker system to compensate for the acoustic characteristics of the room it's in. Even the best speakers can sound bad in a poorly treated room and even properly treated rooms can have some issues.
The Room Correction page has a 16 band parametric EQ for EACH SPEAKER in your setup.
The Room Simulator:
This is a basic algorithm that derives estimated EQ settings based on your room’s measurements and materials. You enter your room's dimensions and materials and it creates EQ curves for the speakers based on that information.
Delay: Along the bottom of the Room Correction page are delay settings for each speaker. In a perfect world every speaker in your immersive setup would be the exact same distance from your head, and sound from all of those speakers would arrive at your head at the exact same time, but this is rarely the case. So you can introduce small delays to the speakers that are closer to you to match the arrival time of speakers that are further away.
3rd Party Room analysis programs
For highly accurate measurements of your room there are several options including Sonarworks Sound ID, Room EQ Wizard, and Smaart to name a few. You can use the readings from these applications to dial in the settings for each speaker in your setup.