Getting Started With Graphs

Picking up Where We Left Off

In the previous sections, we walked through the Measurement Import Wizard and the Configuration Wizard to create a project with a single configuration. We saved the project as getting-started-1.msop. We'll customize the wizard-created graph of that project to improve its appearance and usefulness.

If you didn't save this project earlier, you can find a copy by downloading and unzipping the Getting Started files. Before continuing, save this project as getting-started-2.msop. This will preserve the project for later use.

Each project (.msop file) also has a .msow file associated with it. The .msow file contains information about what kind of tabbed windows were displayed when the project was saved (or even closed without saving). If the .msow file is not present in the same directory as the .msop file, no tabbed windows will be displayed. Should this occur, go to the main menu, choose Graph, Show Graphs, check the graphs you want shown and choose OK. This will show the graph, pictured below, that we created earlier.

Modifying the Appearance of Graphs

Right-clicking on the graph shows its context menu.

For this guide, we'll be looking at two commands: Graph Properties allows us to customize the graph itself (axes, legend etc.), while Trace Properties allows us to customize the appearance of each trace (color line thickness, offset and so on). Rather than using the context menu, it's quicker to just use the shortcut keys Ctrl+G for Graph Properties and Ctrl+T for Trace Properties.

Choosing Graph Properties brings up its property sheet illustrated below.

All options on this property page (show the title and show the legend on the bottom) look reasonable, so we'll keep them as-is. Next, choose Axes to display the Axes property page shown below.

Looking at the graph at the top of this page, we can see a few things that should be changed.

• The maximum value of the graph's y axis is a strange value determined by the y-axis auto-scaling. It should be set to a multiple of 5 for a cleaner appearance, since we'll set the dB per division (dB/div) value to 5 in the next step.
• For online forum posting, 5 dB/div is a de facto standard. Although the image does show 5 dB/div, this value is determined by y-axis auto-scaling and varies with the size of the window and the monitor's pixel resolution. We should manually force this to the common 5 dB/div value.
• Some low-frequency data is being cut off. Our data goes down a bit lower than 10 Hz, but the MSO default limits for the frequency axis are 20 Hz to 200 Hz. We'll change the lower frequency limit to 10 Hz.
• The y-axis lower limit should be set to 60 dB, as its current value is not a multiple of 5 dB.

Incorporating these changes to the Axes property page gives us the result below.

The minimum value of the frequency axis has been set to 10. For the left y axis, Autoscale has been unchecked, allowing the minimum and maximum y-axis values to be set to 60 and 115 dB respectively. Unchecking y-axis Autoscale has allowed Auto dB/div to be unchecked, which permits the left y-axis dB/div to be forced to 5.

We don't need to press OK to see the changes. Instead, we can choose Apply, which will apply the changes while keeping the dialog up. If we don't like the appearance or if we forget something, we can make more changes while checking the result with Apply until we get the appearance we want.

Here's what we get with the above changes.

This looks a lot better than our original graph at the top of the page.

Now let's look at a few more options. The All Traces property page is shown below.

This property page is related to the Trace Properties property sheet, which we haven't discussed yet. The Trace Properties property sheet allows setting trace properties on an individual basis. In contrast, this property page allows you to set some properties that apply to all traces. For instance, you can specify whether only response magnitude is displayed, or both magnitude and phase, or only phase. If you select Choose for each trace, then you can specify this behavior on a trace-by-trace basis on the separate Trace Properties property sheet. This gives you more control over trace display, at the expense of requiring more steps to specify the behavior you want.

A similar situation applies to phase unwrapping. When phase is unwrapped, you get a continuous trace of phase vs. frequency. When not unwrapped, the phase vs. frequency has a "sawtooth" appearance, with discontinuities at ±180 degrees. If you pick Choose for each trace, you'll need to go to the Trace Properties property sheet to individually specify how you want each trace's phase vs. frequency plot to appear.

Target curves that you specify (elsewhere in MSO) can be displayed on MSO graphs. The Target Curve Display option relates to how these curves appear on graphs. For instance, if your target curve text file shows +6 dB at 20 Hz and 0 dB at 200 Hz, Normalize to 0 dB will show the curve as-is. The Optimization Options property sheet (not yet discussed) in most cases requires you to specify a reference level, which is the SPL value that MSO tries to force your response to match during optimization. Please note that the reference level in MSO has nothing whatsoever to do with AVR reference levels. When Shift to reference level is specified, and a reference level of, say, 80 dB is specified, the above target curve would show 80 dB at 200 Hz and 86 dB at 20 Hz. This has the advantage of allowing you to see the MLP response being forced to the target curve as an optimization is run.

We won't be doing any optimization in the Getting Started Guide, as this guide is mainly for familiarizing you with MSO. We'll keep the options shown above as-is.

If you haven't done so already, choose OK to close the Graph Properties property sheet. Before continuing, save this project as getting-started-2.msop. You can also get a copy of the project with the modifications we did above in the Getting Started files you downloaded earlier. Look for the getting-started-2.msop project in the zip file.

Modifying the Appearance of Graph Traces

In addition to the options for controlling the appearance of the graph itself, you can control the appearance of individual traces on the graph. To do this, you can either use the graph's context menu or press Ctrl+T to bring up the Trace Properties property sheet shown below.

You can apply offsets to the magnitude or phase portions of the trace.

• Magnitude display offset, dB is usually used when plotting data from multiple configurations on a single graph. That will be discussed later in the User Guide. Briefly, by offsetting all the curves from one configuration by the same value relative to the other, visual comparison of data from multiple configurations is made easier.
• Phase display offset, deg is usually used when displaying unwrapped phase. Most commonly, an offset value that's either a positive or negative integer multiple of 360 degrees is used.

Plot live data when optimizing should be checked in almost all circumstances. Unchecking it allows you to suppress, for the chosen trace, the animated trace display that occurs when running an optimization.

• For some trace types, this checkbox is always unchecked and can't be changed. For instance, if you're plotting measurements or target curves, those quantities aren't affected by the modifications of filter parameters that occur during optimization.

Activating the Trace color combo box brings up a Windows color picker for your color choice. You can also tell the color picker to just use the default.

You can set the Trace thickness, pixels to the desired value via the spin button control. The default is two pixels, which may be too thin if your computer has a 4k display.

There are controls for Show magnitude, Show phase and Unwrap phase that are shown as disabled. These can be enabled in the All Traces property page of the Trace Properties property sheet as discussed above.

As a quick demonstration, we'll change the magnitude offset and trace thickness of the MLP trace. Select the MLP trace on the left, and enter -10 for the value of Magnitude display offset, dB. Set Trace thickness, pixels to a value of 4. Press Apply or OK to see the result shown below.

This change doesn't have any practical usage in this specific situation, so there's no reason to save the project in this state.

What's Next

The purpose of the Getting Started Guide has been to familiarize you with the simplest basics of how to begin using MSO. We haven't covered optimization yet. Understanding MSO's optimization capabilities and what you can do with them requires some in-depth technical explanations. Such matters are the subject of the User Guide.