Multi-Sub Optimizer Tutorial (page 4)

Running the Configuration Wizard

So far, we've imported twelve measurement data files, consisting of four subs (SUB1, SUB2, SUB3 and SUB4) measured at three listening positons (POS1, POS2 and POS3). But MSO doesn't automatically "know" what the data represents. We must provide MSO some information about the meaning of the data. This information consists of:

The purpose of the Configuration Wizard is to make this an easy, step-by-step process, while minimizing the possibility of error.

You'll see the page below when the Configuration Wizard is first launched.

Choose the Number of Subwoofers You've Measured
Choose the Number of Subwoofers You've Measured

We've measured four subs, so pick that number and click Next. This will bring up the next wizard page, asking for the number of listening positions measured.

Choose the Number of Listening Positions You've Measured
Choose the Number of Listening Positions You've Measured

MSO will guess the number of listening positions as the total number of subwoofer measurements imported, divided by the number of subs you just specified. You can change this number if you need to. MSO calculated three listening positons, which is correct. Pressing Next leads us to the next wizard page.

Choose the Subwoofer Names
Choose the Subwoofer Names

After having been told how many subs were used in the measurements, MSO automatically generates names for them. You can change those names here, either by clicking twice on a name to activate an in-place edit control, or by selecting the name and pressing F2. There's nothing special about these names, other than that they should be recognizabe as being similar to what's used in the measurement file names. For example, the part of the file name used to identify the sub looked like "SUB1", "SUB2" and so on in the measurement file names. These are simliar enough to the automatically generated names above to recognize them, so we can leave them as-is. We'll accept these names and click Next. This brings us to a similar wizard page for identifying the names of listening positions.

Choose the Listening Position Names
Choose the Listening Position Names

This page is similar to the one for identifying sub names. It's common for users to pick a name like "MLP" for the main listening position, specifying that name in the measurement files exported from REW. In such a case, renaming one of the positions to "MLP" would make sense. But here we have used "POS1", "POS2" and "POS3" for the positions in the measurement file names. These are similar enough to MSO's automatically-generated listening position names to keep them as-is. Click Next to go to the next wizard page.

Associate Measurements With Subs and Listening Positions
Associate Measurements With Subs and Listening Positions

Here we have what is arguably the core of the Configuration Wizard, in which the relationships between listening positions, subwoofer names and measurement file names are established. This page uses a properties grid to specify the relationships. Clicking on the right column causes a drop-down combo box to appear in the column, indicated by a downward caret. Clicking on this caret causes a list containing the base names of the imported measurement files to appear in alphabetical order.

Earlier in the tutorial, we talked about putting the position name first in the edit controls of REW's measurement tabs on the left side of the REW window, and that doing so made usage of the Configuration Wizard easier. Now we can see why this is so. We saw that the file names REW automatically generated matched the content of these edit controls, with ".txt" appended. Alphabetical sorting of these file names therefore groups them by listening position, which is the same as the grouping MSO uses in the properties grid of this wizard page. This makes it much easier to match everything up. In fact, the order of the file names in the drop-down list exactly matches the order of the items presented in the properties grid.

Choosing the file name for each row of the properties grid results in the following display.

Associate Measurements With Subs and Listening Positions
After Measurement Associations

If you were to accidentally choose the same measurement for more than one combination of listening position and subwoofer, MSO would detect this, giving you an error message and allowing you to correct the problem. You'll also get an error message if any position/subwoofer combination is left unassigned to a measurement. MSO cannot detect if measurements are swapped though, so care is needed.

The choices above are all correct, so we'll click Next to get to the next wizard page.

Choose to Create a Configuration or Just a Template
Choose to Create a Configuration or Just a Template

This wizard page might seem a bit strange. A configuration template is a sort of "cookie cutter" used to "stamp out" configurations. Its main usage is that if an incorrect association of imported measurement file to position/subwoofer combination were made that MSO cannot detect, (such as the swapping mentioned above), after running the wizard you can edit the created template to fix it, then create a new configuration from the repaired template without having to start the Configuration Wizard from scratch. It's also a component that may be used as part of a future MSO feature.

The recommended default choice of creating both a configuration and a template is the correct one. The template name is not important, and at any rate can be changed later if desired. Pick the recommended choice and click Next. This takes you to the final page of the Configuration Wizard proper.

Specify the Properties of the New Configuration
Specify the Properties of the New Configuration

Specifying the Properties of the New Configuration

An MSO configuration uses zero or more parametric EQ filters (PEQs) in each subwoofer DSP channel, along with zero or one gain blocks and zero or one delay blocks per subwoofer channel. This wizard page allows you to specify how many PEQs you wish to use per subwoofer channel in the newly-created configuration. The purpose of each PEQ is to counteract the effect of a room mode on the seat-to-seat variation of frequency response. You can think of it as one individual PEQ per sub channel per room mode, so that N PEQs per channel can counteract N room modes. Thus the number of PEQs per subwoofer channel that you choose roughly corresponds to the number of room modes that have a non-trivial effect on the sub responses over the frequency range of optimization (which defaults to the range 20 Hz to 150 Hz).

Gain blocks are used both to control the level of the subs relative to one another in order to minimize seat-to-seat response variation, and to establish a target SPL level that you'll specify later.

Delay blocks are used to control the interaction of the subs with one another, and provide a way to ameliorate or eliminate response "suckouts" without using a boost at the frequency of the suckout.

Specifying the Number of PEQs Per Sub

If you haven't done so yet, I highly recommend getting the third edition of Floyd Toole's Sound Reproduction book. Chapter 8 alone is worth the price of the book. His Figure 8.8 (d) and (e), which I can't reproduce here, nicely show the relationships between room mode frequencies and response peaks and dips at a given listening position. This insight, along with a room mode calculator, can help guide you in your choice of the number of PEQs per sub to use.

The spin button control illustrated allows you to pick the number of PEQs per sub to use. Here we'll choose the default of four.

Specifying Whether to Use RBJ or Legacy Q Definition for PEQs

Users of miniDSP hardware that will be exporting biquad text files from MSO to set up their filters need not be concerned about this option, as these differences in definition of Q all "come out in the wash" of the biquad coefficient calculations. Users of hardware requiring manual entry of PEQ Q values, such as Behringer DSP amps, need to take care with this option. The Behringer DSP amps use the RBJ Q convention, while the Behringer DCX2496 active crossover DSP device uses the legacy Q convention. More information can be found in the filter compatibility section. Here, we'll choose the default of the RBJ Q convention.

Specifying Whether to Add Gain and Delay Blocks

Gain blocks are necessary for establishing the response reference level that you specify in the Optimization Options dialog, while delay blocks are very useful to minimize response "suckouts" as mentioned earlier. Choose the default checked option for both of these.

Specifying Whether to Launch the Graph Properties and Optimization Options Dialogs

Although this is the last page of the Configuration Wizard proper, you can get additional wizard-like behavior by choosing the Launch Graph Properties dialog when done and Launch Optimization Options dialog when done options. By selecting these options, you'll be able to set up your graphs and optimization options right away, speeding up the process. Choose the default checked option for both of these, then press the Finish button.