MSO allows for a number of optimization approaches. You can choose to optimize the integration of subwoofers with one another only, or you can include the main speakers in the optimization as well, to optimize integration of subs and satellites. Usage of MSO requires that you have some sort of DSP device with IIR filters available so that EQ, gain and delay can be applied to each subwoofer individually. The alternatives can be categorized as follows.
- For optimization of only subs, use an AVR with crossover frequency (or LPF of LFE) temporarily set to the highest allowable frequency prior to performing measurements.
- For optimization of subs, main speakers and their integration with one another, decide on the crossover frequency to use, set the crossover to that frequency, then perform the necessary measurements with the main speakers set to small.
In certain rare cases, you may be able to use MSO to help determine an optimum crossover frequency. This would require that you have a signal processing device that can be configured to provide a mono signal to the subs without the usual low-pass filter found in bass-managed systems, while providing individual signals to the main speakers without the usual high-pass filter. Such devices are rare.
- Using MSO to optimize the crossover frequency won't be covered here. It has been moved to a separate topic due to its complexity and strong dependence on the specific hardware used.
Use an AVR or pre-pro without a conventional crossover using the configuration recommended by Earl Geddes.
- This method should not be used if you have any ported main speakers that aren't protected by high-pass filters, as the Geddes approach uses no crossover, therefore no high-pass filters on the main speakers.
- Such high-pass filters are needed for ported main speakers to prevent excessive excursion at frequencies below their box tuning frequency. An exception to the rule above might involve the usage of certain active pro audio monitor speakers that already include such a high-pass filter for protection, such as the JBL Pro 708p.
- This method is now deprecated. Discussion of it has been moved to a separate topic.
- Use an HTPC configured to apply DSP to each subwoofer individually and optionally the main speakers.
The Reason for the Different Configuration Types
The two configuration types (sub-only and subs+mains configurations) exist because there are two different sets of rules regarding the allowable quantity and position of delay blocks for the two types. For instance, when adding delay and gain blocks, the MSO user interface imposes constraints that ensure these rules are followed. These rules exist to prevent convergence problems from occurring during an optimization.
There are other rules that differ between configuration types as well. For example, you must choose a fixed reference level in the optimization options for a sub-only configuration, but it's allowable to use either a fixed or an automatic reference level for subs+mains configurations.
Optimizing Subs Only
When preparing to perform the measurements needed for optimizing only the subs with MSO, you should set the crossover frequency of the AVR or pre-pro (or its "LPF of LFE") to the highest allowable frequency. Whether you choose the crossover frequency or LPF of LFE depends on how you apply an input signal to the AVR. If you use one of the main speaker channels via either analog or HDMI excitation, temporarily set the crossover frequency to its highest allowable value. If you apply an HDMI signal via HDMI channel 4, temporarily set the LPF of LFE to the highest allowable frequency. Be sure to read the measurement guidelines before performing your measurements.
Using the Wizards to Optimize Subs Only
To use MSO to optimize only the subs and not their integration with the main speakers, you must create and use a "sub-only configuration" for your project. Since all known sub-only configurations are also standard configurations, you should use the Measurement Import Wizard to import the measurements and the Configuration Wizard to create the configuration.
When you run the Measurement Import Wizard, you'll be presented with the following wizard page.
Choose Only sub data as shown in the image above. After choosing the files to import, you'll be presented with the wizard page below.
Choose the option to run the Configuration Wizard. Follow the steps of the Configuration Wizard to create your configuration. The usage of the Measurement Import Wizard and the Configuration Wizard is discussed in detail in the tutorial and later in the reference.
Optimizing Subs and Mains
Before performing the meaasurements you need for MSO, set your AVR's crossover frequency to the desired value. Measurements should be performed with the crossover in place, according to the instructions in the measuements section.
Using the Wizards to Optimize Subs and Mains
Most configurations with subs and mains that you'll want to optimize are standard configurations, for which you can use the Measurement Import Wizard and the Configuration Wizard. The wizards should be used whenever possible to avoid unnecessary work. When you run the Measurement Import Wizard, the first wizard page gives you a choice of importing only sub data or data of both subs and mains. This is shown below. Choose the option to import sub and main speaker data.
After choosing the files to import, you'll be presented with a wizard page asking if you want to launch the Configuration Wizard. Select the choice to run the Configuration Wizard per the image above. When the Configuration Wizard runs, it will ask you whether you want to create a sub-only configuration or one with subs and mains. Select Configuration with both subs and mains per the image below.
Then just follow the various wizard prompts to create the configuration. For step-by-step instructions to complete the Configuration Wizard, see the tutorial.
Creating a Subs+Mains Configuration Manually
When using a non-standard configuration, the Configuration Wizard can't be used. In such cases, you must use the manual procedure for creating configurations.
When using the manual procedure to create subs+mains configurations, adding filters to subwoofer channels is part of the task. Do not add crossover low-pass or high-pass filters, as their effect will already be present in the measured data. Any filters added within MSO represent changes from the as-measured condition. When using a fixed crossover frequency, choose Tools, Project Options from the MSO main menu and ensure that Correct sub measurements to remove sub LPF response is unchecked.
Using an HTPC With Filters Implemented in Software
Modern pro audio multi-channel audio interfaces, along with software having DSP capability such as Equalizer APO and JRiver Media Center, provide interesting opportunities for multiple-subwoofer systems without using an AVR or preamp-processor. Because they are so flexible, it's hard to make specific recommendations with regard to their operation with MSO. However, there are a couple of suggestions that are generally applicable.
- Prior to measuring, configure signal routing software for mains, subs and others so the desired signals are getting to the correct loudspeakers, including the routing of summed main channel signals to the sub channels.
- When measuring, run both main loudspeakers and subwoofers "wide open", with no high-pass for the mains, and no low-pass for the subs.
- From the main menu of MSO, choose Tools, Project Options, and ensure that Correct sub measurements to remove sub LPF response is unchecked.
MSO has bulit-in support for exporting Equalizer APO configuration files. The usage of Equalizer APO for two-channel multi-sub setups is discussed in the topic Two-Channel Multi-Sub Setups Using MSO and Equalizer APO.