I need Bl/Bl Curve Explained

[NcHalfrican]

As the title says, I need someone to describe what the Bl/Bl curve is.

[arnold1992]

motor strength, that's what I know

[NcHalfrican]

motor strength, that's what I know

How does motor strength affect sound quality, cause from what I've heard a high Bl curve=better SQ. But thats the extant of my "knowledge"

[NcHalfrican]

Bump for knowledge

[NcHalfrican]

Bump, So does a higher BL rating make for a better sounding woofer?

[BJD3]

Bump, So does a higher BL rating make for a better sounding woofer?

Post it in Neo's noob thread?

[HHR Ed]

Flat BL curve can be better SQ, but depends on so many more factors that are much more critical then BL.

Example of a flat BL woofer is the AA SMD.

Example of a high BL woofer is a DD99Z

[NcHalfrican]

Flat BL curve can be better SQ, but depends on so many more factors that are much more critical then BL.

Example of a flat BL woofer is the AA SMD.

Example of a high BL woofer is a DD99Z

How can you determine the Bl curve of a woofer off it's Bl rating, like 15.51 T*m.

[HHR Ed]

How can you determine the Bl curve of a woofer off it's Bl rating, like 15.51 T*m.

A BL rating is simply its peak BL.

The curve has to be mapped with the proper tools.

The BL will change depending on where the coil is in the gap.

[sundownz]

You will typically need a Klippel or DUMAX to measure the BL curve.

You can assumme, though, that most overhung (long coils) at quite parabolic in nature... most under-hung have a flat spot in the center and then become parabolic.

There are ways around this... Alpine flattens it out nicely in the new Type-R with some clever pole machine work:

They machined in a bell shape inside the pole that flattens out the BL curve in the center -- here is an image from their patent:

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Some other examples below.

First we have an overhung - the below is an approximation of the NS v.2 motor... very long gap / long coil design but still parabolic as it's overhung. As far as overhung goes the BL distortion is quite low as with the 71mm coil and 40mm top plate we achieve ~27mm linear one-way throw.

* You see some of the coil sits outside the flux field and the flux is centered in the gap at highest level.

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Next we have underhung - where you can immerse the coil in the peak flux field and it won't leave that area for some amount of stroke therefore giving you a small flat area before becoming parabolic.

* One issue is the tall top plate and short coil tends to make the motors weak as there is poor flux utilization unless you use a giant magnet.

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Now we have something really fancy called XBL^2 -- you have two gaps and the flux is steered around to immerse more coil than underhung and it also forces the flux out farther to extend the flat area of the BL curve.

* Not the greatest example for SQ purposes as it's a big Neo SPL woofer... but you can see how the flux is broken up into two peak concentrations (dark blue areas) with some of the coil in each of those areas. The middle is no longer the strongest spot. As the bottom of the coil leaves the lower flux concentration it equally enters the top concentration so BL does not change for quite some time. These gaps can be stacked if necessary to achieve TONS of flat BL.