The term “bass management” generally applies to it being a crossover point and/or network, that re-directs bass information from the main monitors into your subwoofer. The actual crossover frequency varies with each system, but typically runs from around 80 to 120Hz. Optimally, it should be set at the lowest point at which your smallest speakers can comfortably handle bass information. For the sake of our article, we can break out this discussion into two distinct but overlapping areas — the production process in the studio and the reproduction process in home theaters.
Setting up surround in the studio for 5.1 involves, well — five speakers and a subwoofer. Preferably all full range, these studio monitors, along with the companion subwoofer, need to be properly calibrated. For that, I highly recommend checking out the article “Calibrating the 5.1 System” by Bobby Owsinksi, available online at surroundassociates.com. Once you’ve done that, it’s important to understand how bass management applies in the mixing/production process.
Most of today’s surround mixes done in the studio are reproduced by home theater systems. Many of these have small satellite speakers that can’t handle bass information below 120Hz or so. Any of the frequencies below that will be routed/filtered (within the receiver) from all five speakers into the subwoofer — with the LFE information from your mix. The basic point I’m making here is that LFE and sub are not the same thing. Sub is the summed information that bass management redirects from those small speakers into the actual physical subwoofer. LFE is any information you’ve sent from your mix, using the LFE send on panner for example (SCREENSHOT 1). Just know that the subwoofer itself plays back both the SUB and LFE information.
But if you’re mixing in the studio, how can you simulate the sound of a home theater receiver “bass managing” your mix? The first method would be with hardware, which “sits” between the playback system (DAW, tape, and so on) and the speakers. Systems are available such as the Martinsound ManagerMAX, M & K (Miller & Kreisel) LFE-4 and LFE-5 series bass management controllers, the Blue Sky International BMC, and TASCAM’s DS-M7.1 (say that five times fast!). What these typically offer is the ability to not only manage bass reproduction, but provide volume control, solos and mutes, pink noise generation, and delay compensation, etc. While the specific features vary from unit to unit, they allow you to do a decent job of simulating the home theater environment — even if you’re mixing on $10,000 speakers. Yikes.
The next method of bass managing in the studio is via software, such as Bass Manager VST by Kelly Industries, the Surround Bundle for Steinberg’s Nuendo or the Waves —360 Surround Tools. This lets you control bass management functions within the DAW environment.
Since I use the Waves Toolkit, I’ll briefly describe the M360, which is the Surround Managing part of the software. It provides bass management and studio monitoring calibration based upon the ITU standard (which basically suggests common surround setups in control rooms). M360 features two plug-in components, the Manager and Mixdown. The Manager is inserted on a master surround output and handles the all-important monitor calibration and setup. It also allows for software adjustments of speaker angles, as well as per-channel gain and delay for level and phase alignments. Mixdown can be inserted directly after the Manager, allowing for preview of mono, stereo, LCR (left center right), and LCRS (surround) imaging.
One of the major benefits of software bass management is the lack of extra cables and gear, as well as the total recall of all parameters within each session. I happen to configure my room differently almost each day (from stereo to 5.1), and using software lets me quickly prepare myself for whatever is needed. Whether you use software or hardware for bass management, the point is to check how your pro surround monitors translate like a consumer might hear at home.
Many of the home theaters sold today come packaged as HTIB (home theater in a box), with the aforementioned receiver, small satellite speakers, and powered sub. The limitations of these systems should be taken into consideration when mixing surround in the studio. I have found it useful when mixing music DVDs to add a small amount of LFE information to the mix (typically on kick and bass), so that even with bass management bypassed, there will still be something in the subwoofer. If you add too much LFE however, and a consumer hears a bass-managed mix (which most of them will), the summation of both create a muddy low end. Experimentation is key.
The typical consumer receiver handles bass management in any one of several ways. The first, or “fixed” option usually lets you select either large or small speakers. Large speakers reproduce full range around 20–20kHz, and can handle all necessary bass information. Small speakers cannot reproduce full range and need a subwoofer to properly handle bass information. With a “fixed” setting, the receiver sets a non-adjustable crossover frequency of 80–90Hz (note that the THX standard is 80Hz).
The more common “variable crossover” setting lets you again choose large or small speakers, but then will allow the user to adjust the crossover frequency. This preferred setting lets you create a better bass response for the sat/sub (satellite/subwoofer) setup, providing a smoother low-end response. Some higher-end receivers also offer “multiple variable crossover,” which lets you select different crossover frequencies for different speaker combinations.
Another developing method of 5.1 playback at home is on the PC, especially for video games. There are two basic methods to do this, using hardware-, or software-based reproduction. For hardware playback, you would need a soundcard with a S/PDIF digital output, connected to a full home theater system. With a software-based system, it would be with a multichannel soundcard that has six analog channel outputs. Then you would need a software decoder (like WinDVD) to feed those outputs. That would then run to either powered computer speakers or to six channels of input on a receiver. For example, the Sound Blaster Audigy 2 ZS system delivers up to 7.1 channels of surround, supports 24-bit/96kHz 5.1, and can handle THX-Certification and Windows Media 9 multi-channel formats.
As you can gather from all this information, thinking like a consumer when mixing surround is essential. By understanding the basics of bass management, and how it relates to your speakers, your mixes will translate better in the home theater environment.