I need Bl/Bl Curve Explained

[sundownz]

wow this is great info... i could definitely read about the technical shit all day... but i might add that its good to have someone there to draw it out in Crayons for me...

Ive always looked at woofer specs and have been baffled on what each thing means, what it does, and what its related to as far as the other parameters... all i know is that when i was ready to buy new woofers i compared a few that were in the same power category and Found that the Sa-12 looked like it was king... so i bought a couple...lol

There hasn't been much technical discussion on the forums for years. So I'm hoping we can get some information posted up from various sources without getting into fights about whose stuff is the best ever So far so good - maybe Nick will come back with some more additional information as well and we can get a decent thread rolling!

IMO... there is not a "perfect" design... only the best for the application and the person who is using it. There are MANY approaches that can get great results.

[sundownz]

I also hope that additional contributors will try to make it easy to understand -- when you do this every day it can be easy to forget that it's pretty complicated stuff to those that don't do it every day

[Rogers]

definitely a cool idea... we definitely need a bunch of the specs explained individually and how they go hand in hand with the other specs...

[lt1z323]

Are their any advantages to having two BL peaks such as with the JBL GTI Series?

[sundownz]

The goal was likely to make it flat but the spacing wasn't quite right in the center - resulting in a valley.

If XBL^2 is not implemented properly you will get a BL curve just like that.

[NcHalfrican]

Woah! Thanks jacob, as well as the other comments! Cleared a hell of alot stuff up...sorry for the late reply, my computer has been on the fritz lol

[Ray]

Dont know how Ive been missing this thread.

And nice to know you rate xmax @ 30% loss

Any of you know where the video is of wiggins showing the flux of the motor outside ..... where it was magnetizing shit to the motor?

[finkster]

as for XBL^2 giving you the most excursion, I can believe that.

Here is one of Wiggin's designs that had 72mm one way excursion.

[NDMstang65]

as for XBL^2 giving you the most excursion, I can believe that.

Here is one of Wiggin's designs that had 72mm one way excursion.

XBL^2 does NOT give you the "most excursion" period...it is a topology that simply gets ride of the high flux concentration areas by carving steel out of the gap and getting rid of the "peaks" that you hear/see...it doesn't mean "High Excursion"...it is linear if that is what you are going for..there are drawbacks with it as well as with any other topology..

You are also VERY limited to the length of the coil you can do (in order for it to work how it is intended), which in turn effects thermal power handling. If you can only have a 28mm long coil for it to work...then you can only push it so much. You can do a 12 layer..but then you have inductance so high that it rolls off at 55Hz on the upper end...

You can make things more compact which is where it makes sense in mids and tweeters...or in shallow mount subs and still have decent excursion...when you get up to subs that move significantly you are fighting mass...and taking steel out of a gap at that point when you are trying to fling the parts very far simply doesn't make any sense at that point...Which is where you run into supergauss..

We use supergauss in the SMD..which has a very parabolic BL curve..that is very high...because coils never leave the gap. If you don't have wire in the gap, or you don't have steel in the gap..you have ever decreasing motorforce...

Then you have the Havoc carbon 7's have pretty much the highest excursion of a mid on the market still to this day..at 11.5mm 1 way..and it's a split coil design...and still sound fantastic while doing it as well. You don't get the muddy sound that you get with many "midbass drivers" and you have plenty of low end extension. I've got mine crossed down to 56Hz on the bottom end..and start rolling them off around 2300Hz or so on the top end..I can take them up to 5500Hz with no issues before you run into cone breakup, but I simply don't like having a mid play that high. I'm more of a fan of crossing things over much lower and having the stage sound like it is infront of you..instead of running a sub up to 125Hz and being able to locate it easily in the car...

To each his own though Just wanted to clarify that one.

[sundownz]

Nick is right - you can get a ton of excursion with all sorts of designs like split coil as well.

Everything has it's place for a given application

For example - I'm using XBL^2 for my Neo 8" to keep the motor as shallow as possible for a given amount of linear throw -- in the "Street" style enclosures it is designed for you don't want a huge motor taking up all sorts of room in the box. I did need to use a "fat" coil to get good thermal power handling and the level of motor force that I wanted for that design -- to combat the inductance with a 12-layer coil, which is a legitimate concern as Nick mentioned, shorting rings are being implemented inside the XBL^2 rebates. Pending testing I may implement even more extensive shorting rings if it still rolls off too much on the top end.

So, as we've been mentioning throughout there are trade-offs made for every design - really depends on what you are trying to accomplish. The Neo-8, for example, is made primarily for one thing - and that is high SPL in tiny enclosures - so I started with a topology with the highest linear excursion to depth ratio so it would actually FIT in the tiny boxes and then dealt with the trade-offs from that point. Each one results in another trade off -- the short coil called for alot of layers, which then called for shorting rings due to inductance, which in turn makes the design more expensive and complicated, but in the end results in what was needed for the application which was a shallow motor with high motor force and high linear excursion.

I typically use over-hung for Sundown Audio designs for the reasons Nick and I have mentioned here -- the longer coil is alot more durable. That is also a big plus for the new Super-Gauss design too - the big ol' coil is going to be difficult to damage.