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Bl curve basically shows the force of the motor relative to excursion, both forward and rearward.

As you can see in the below picture, Bl (motor force) is on the Y axis and excursion is on the X axis. The curve shows the change in motor force as the coil moves through the range of excursion.

We can use the graph to define Xmag, which is the maximum linear operating range of the motor. This is defined by Klippel (the measuring system used to generate this graph) as the point at which the motor force (Bl) has fallen to 70.7% of it's rest value. Xmag is important because it is one of the determinants of Xmax, which defines the maximum linear excursion the driver is capable of achieving, which can be used to define the maximum usable output a driver is capable of achieving. Xmax is the lesser of Xmag and Xsus (Xsus being the linear maximum linear operating range of the suspension).

The graph also shows us the linearity of the motor. There are a few schools of thought on the "ideal" curve, but generally we would like to see the motor force stay relatively constant throughout the operating range of the driver. This means the curve wouldn't be as much of a "curve" as it would be a plateau, like the one pictured below, that stays flat for a period of time then begins to roll-off at the edges. The Bl curves for some drivers look more like an upside-down "U", those are said to be "parabolic" curves (there's some of that high school geometry you swore you'd never use in real life!).

The reason we would like to see the "curve" stay flat is that if the curve is moving upward or downward, this is indicating a change in motor force at those excursion levels. This is generally bad for driver performance for a few reasons, but primarily because a change in motor force will cause a change in Thiele-Small parameters which will affect the response of the driver, and because a change in motor force will create non-linearities that will manifest as distortion.

So yes, generally a Bl curve will give us an idea of the performance we can expect to see from a driver and can give us a glimpse into the quality of the design of the motor. But it takes more than a Bl curve to give us a good idea as to the "SQ" of a given driver. A Bl curve alone won't do it. But a good driver starts with a good foundation......and a nice Bl curve indicates a well thought out and well executed motor design, which is a great start to having a great driver :)

peerbl.JPG

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Bl curve basically shows the force of the motor relative to excursion, both forward and rearward.

As you can see in the below picture, Bl (motor force) is on the Y axis and excursion is on the X axis. The curve shows the change in motor force as the coil moves through the range of excursion.

We can use the graph to define Xmag, which is the maximum linear operating range of the motor. This is defined by Klippel (the measuring system used to generate this graph) as the point at which the motor force (Bl) has fallen to 70.7% of it's rest value. Xmag is important because it is one of the determinants of Xmax, which defines the maximum linear excursion the driver is capable of achieving, which can be used to define the maximum usable output a driver is capable of achieving. Xmax is the lesser of Xmag and Xsus (Xsus being the linear maximum linear operating range of the suspension).

The graph also shows us the linearity of the motor. There are a few schools of thought on the "ideal" curve, but generally we would like to see the motor force stay relatively constant throughout the operating range of the driver. This means the curve wouldn't be as much of a "curve" as it would be a plateau, like the one pictured below, that stays flat for a period of time then begins to roll-off at the edges. The Bl curves for some drivers look more like an upside-down "U", those are said to be "parabolic" curves (there's some of that high school geometry you swore you'd never use in real life!).

The reason we would like to see the "curve" stay flat is that if the curve is moving upward or downward, this is indicating a change in motor force at those excursion levels. This is generally bad for driver performance for a few reasons, but primarily because a change in motor force will cause a change in Thiele-Small parameters which will affect the response of the driver, and because a change in motor force will create non-linearities that will manifest as distortion.

So yes, generally a Bl curve will give us an idea of the performance we can expect to see from a driver and can give us a glimpse into the quality of the design of the motor. But it takes more than a Bl curve to give us a good idea as to the "SQ" of a given driver. A Bl curve alone won't do it. But a good driver starts with a good foundation......and a nice Bl curve indicates a well thought out and well executed motor design, which is a great start to having a great driver :)

peerbl.JPG

Woah! That cleared up alot of stuff...thanks brah.

I still have one question though. What does the Bl rating of a driver represent?

For example the SoundSplinter RL-i 8, Single 4 ohm version, has a Bl of 15.51T*m

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The BL is the motor strength in tesla-meters. It is the magnetic flux of the motor (B) times the length of wire in the magnetic gap (L)

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As noted, the graph was generated with the Klippel measurement system.

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