First let's examine the BL (Force Factor) curve in the upper left. This represents the "motor strength" of the speaker, and is essentially the "force" that drives your speaker. The X axis represents the distance your speaker cone or voice coil has travelled in mm. The Y axis represents your motor strength.

This is perhaps the most important curve, since it's responsible for a majority of the distortion produced by a speaker. Ideally, we would want the speaker to produce an equal force in the positive and negative direction. The overall motor strength is not important, but it's linearity... basically how flat the curve is and how symmetrical it is about x = 0. If the curve is non-symmetrical or uneven, distortion will be produced.

Now, we can see that if the BL curve were highly uneven, that would cause quite a bit of distortion since the "force" pushing your speakers would be uneven. Another thing to note is that when BL drops, your motor strength drops, and pretty much it takes MORE power to push your speaker. And when your BL changes, your t/s parameters change as well. So this is a very important curve here.

Now looking at this speaker, we can see that it has pretty good symmetry. The left half of the graph looks like the right half. Also it has a very long and flat plateau around x = 0. However, we can see that the further you move the speaker out or in, the motor strength begins to drop. The point where the motor strength is 71% of the strength at x = 0 (the rest position of the speaker), is what we define as XMag. Beyond XMag, the speaker in theory will generate significant audible distortion.

Also, look at the CMS (mechanical compliance, aka how loose the suspension is) and the LE (inductance) curves. CMS is the inverse of the suspension stiffness, and LE is the self inductance of the driver. KMS is the actual suspension stiffness.

These curves are important as well, and follow the same principles as the BL curve. CMS linearity is generally speaking the second most important factor determining distortion performance, and after that LE. With LE, you must also take into account both frequency and absolute inductance in determining distortion performance, in addition to variance.

We define the limit for the suspension (how far the speaker can move mechanically without producing significant distortion) as XSUS. It is 75% of the CMS value of X = 0.

For this example, we can see that the CMS curve is not exactly centered at x = 0, or the rest position. It's forward biased, meaning that it will allow a little more throw in the forward direction than in the rearward direction.

Now look at the second chart with all the numbers. Find the value of BL and CMS at x = 0. We know that:

Xmag = 71% of rest value

Xsus = 75% of rest value

In this case 71% of rest BL = 2.8897

75% of rest CMS = 1.6575

Take those values and follow them across the graph until you hit the measurement curve, and look directly down to the X axis to find the actual displacement value.

For Xmag we have a range of -5.5mm to +5.5mm.

For Xsus we have a range of -2mm to +3mm.

To calculate Xmax, (the limit of the speaker taking into consideration both suspension and motor linearity)... we take the smallest of both values. In this case the Xmax would be 2mm.

Another useful tip is to look at the dashed line. It's basically a mirror of the original curve about the y axis. For a speaker with good symmetry (like this one), you should not be able to see the dashed line.