what is BL?

[sound giant 10+ year member]

i was just looking at specs for some subs what is BL? what does it stand for? is a higher number better or lower? say BL is 15.9....good spl?

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[DBfan187 5,000+ posts]

measurement of the motor strength. Usually measured in telsa meters™

 

[boister77 10+ year member]

This is a measurement of the motor strength of a speaker. A high BL figure indicates a very strong transducer that moves the cone with authority.

 

[squeak9798 5,000+ posts]

Flux density x Effective length of coil in the gap.

 

[sound giant 10+ year member]

so is 15.9 high number in subwoofers? u want more motor strength correct?

 

[Acidburn 5,000+ posts]

yes, more motor strength is better

for comparison: (all 15")

XXX:17.1

Magnum: 21.5

Brahma: 15.9

Death Penalty: 26.591

 

[InhumanAcura 5,000+ posts]

MT:37.27 Tm

 

[DanWiggins 10+ year member]

yes, more motor strength is better
for comparison: (all 15")

XXX:17.1

Magnum: 21.5

Brahma: 15.9

Death Penalty: 26.591

You can have too much motor strength, just like you can have too little. You want enough motor strength to accomplish your design goals, and no more. No less, either...

Dan Wiggins

Adire Audio

 

[sound giant 10+ year member]

well brahmas have low BL compared to the rest listed. does that mean less SPL? Dan Wiggins how do u think brahmas compare to the other 3 subs in SPL potential?

 

[hoss 5,000+ posts]

BL is the mechanical force created by the woofer, and it can be defined as B x L. where L represents the length of wire on the coil, and B represents the given flux density, or magnetic capabilities of the wire used.

and as Mr. Wiggins pointed out, there can be such a thing as too much Bl. but typically, more Bl leads to better cone control and excursion capabilities, all of which leave the picture once the coil leaves the gap though...

 

[DanWiggins 10+ year member]

well brahmas have low BL compared to the rest listed. does that mean less SPL? Dan Wiggins how do u think brahmas compare to the other 3 subs in SPL potential?

Scottie Johnson set quite a few records with Brahmas. Tempests have a BL of 14.2, and Marshall Joyner just won World Finals MR2 for MECA.

In other words, BL is not a guideline in terms of SPL... SPL is about displacement. The driver with the most stroke for the applied power wins. Period. You want the motor to be strong enough to reach full excursion with the power you have available in the box you're running, if you want full-on SPL. If you can do it with a BL or 10, then any BL above that level isn't really needed.

but typically, more Bl leads to better cone control and excursion capabilities, all of which leave the picture once the coil leaves the gap though...

No, doesn't really mean anything for cone control at all. It does mean less power required for a given excursion level (all else being equal); however, it also means less bass. If you get your BL from lots of extra L, then you increase mass, and lose your efficiency gain. And having a really high BL means you generate a lot of back EMF, so you have higher impedance swings (really only an issue with tube amps).

Dan Wiggins

Adire Audio

 

[mdma 10+ year member]

Would the Magnum have trouble being powered by a tube amp? What about a Brahma/XXX?

 

[hoss 5,000+ posts]

No, doesn't really mean anything for cone control at all. It does mean less power required for a given excursion level (all else being equal); however, it also means less bass. If you get your BL from lots of extra L, then you increase mass, and lose your efficiency gain. And having a really high BL means you generate a lot of back EMF, so you have higher impedance swings (really only an issue with tube amps).

thanks for explaining that, im still trying to learn it all, as you can probably tell ive got some of the basic principles... just havent learned the applications. when i said cone control i meant the excursion levels... i just didnt word it right //content.invisioncic.com/y282845/emoticons/spank.gif.0d78e34d42ea8780359e903aeb6697d6.gif