Subs with XBl^2

[Steven Kephart 10+ year member]

dual gap technologies, have - you guessed it, two motor\plate gaps, for a 'stronger motor force'... but i cant see this working very well unless there is a bigger coil and stuff. so i dunno if its actually that much better or not (as far as linerarity is concerned).
and is there a cross section of these motors? ive seen standard and overhung cross sections done before. but how about XBL2,

Here's a link to our tech page explaining XBL^2: http://www.adireaudio.com/Files/XBL2DetailsPaper.pdf

XBL^2 pretty much takes the best of overhung and underhung. It acts as an overhung in that the coil is longer than a single gap. But it acts as an underhung as the coil is shorted than the top plate height. What happens is that the coil trades off between gaps. As it moves out of one gap, it moves into the other so no motor force is lost. In fact no motor force is lost until the coil starts to leave the single gap, and doesn't have another gap to move into (above and below the top plate). Since the coil is longer than a single gap, you get even more excursion without a loss in BL. It's a real clever way to get a lot of excursion out of a short coil/top plate (compared to the previous design).

Here's a tech paper showing a comparison of the linearity of the different motor types: http://www.adireaudio.com/Files/XBL2TechPaper.pdf

Steven Kephart

Adire Audio

 

[SPL140.2 5,000+ posts]

This is all pretty interesting. I have never care of how a subwoofer worked but the more info i read on this the more interested I get. Got anymore info? Feed me more! //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[req 5,000+ posts]

Here's a link to our tech page explaining XBL^2: http://www.adireaudio.com/Files/XBL2DetailsPaper.pdf
XBL^2 pretty much takes the best of overhung and underhung. It acts as an overhung in that the coil is longer than a single gap. But it acts as an underhung as the coil is shorted than the top plate height. What happens is that the coil trades off between gaps. As it moves out of one gap, it moves into the other so no motor force is lost. In fact no motor force is lost until the coil starts to leave the single gap, and doesn't have another gap to move into (above and below the top plate). Since the coil is longer than a single gap, you get even more excursion without a loss in BL. It's a real clever way to get a lot of excursion out of a short coil/top plate (compared to the previous design).

Here's a tech paper showing a comparison of the linearity of the different motor types: http://www.adireaudio.com/Files/XBL2TechPaper.pdf

Steven Kephart

Adire Audio

thanks mr steve for sheding some light (with info to back it up). i love learning about this stuff! and now that you made the relation about the coil moving to the lower gap and keeping the BL the same at both of them, it makes more sense on how it actually works.

what didnt make sense, is with the DGT from DEI (or whoever they liscense it from) they have two magnets (one slug, and one single-layer with multiple slugs, and a plate on top of each one) and each plate acts as the gap.

why is XBL^2 better than this technology? because all thats needed is the 'two-gaps-in-one' instead of two plates and sets of slugs? or does it go further than that?

//edit

heres a good pic i just made from the PDF that steve linked (eaiser to see)

//content.invisioncic.com/y282845/emoticons/veryhappy.gif.fec4fed33b4a1279cf10bdd45a039dae.gif

correct me if i made any mistakes //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[Warbleed 10+ year member]

To further clarify what I said earlier, with an overhung motor, making the top plate taller increases BL and reduces Xmax. With an underhung motor, making the top plate taller increases xmax and BL linearity, but will likely not effect BL, since the same amount of the coil is still going to be in the gap.

As far as coil adjustments go, making the coil longer on an overhung driver increases xmax, reduces BL, and increases BL linearity. In an underhung driver, increasing coil length increase xmax and reduces BL linearity, and increases BL.

So the greater the VC to gap ratio in an overhung, the better the BL linearity, and the lower the VC to gap ratio in an underhung, the better the BL linearity.

Underhung motors have very flat BL curves by nature, essentially not losing any BL at all until turns of wire start leaving the gap. However, the two goals of xmax and BL linearity are at odds with one another in an underhung design. To have great BL linearity and high xmax, you need a very large gap.

That's one advantage of XBL^2, is that you can great BL linearity and xmax without having a gargantuan top plate. An underhung can get the same xmax or linearity as an XBL^2 motor with the same gap, but it can't have both of them at the same time.

 

[zebo 10+ year member]

I have read before, and maybe someone here knows for sure, that the H2’s use DGT technology and that they cannot be reconed because they are magnetized after they are fully assembled (that’s why when you blow an H2, you don’t get the original back, just a new one). I don’t know if this is an inherent trait of the motor topology or just of that sub. If it just the nature of that topology that would be a serious disadvantage as opposed to xbl^2. Also, when you are adding multiple top plates and slugs you are adding to the mounting depth of the driver, another drawback.

 

[req 5,000+ posts]

and - most importantly, you are adding to the weight.

ever seen a shocker SIG? freggin top plate was like a few inches thick. i think it was an underhung design - but im not sure.

 

[zebo 10+ year member]

In an underhung driver, increasing coil length increase xmax and reduces BL linearity, and increases BL.
So the greater the VC to gap ratio in an overhung, the better the BL linearity, and the lower the VC to gap ratio in an underhung, the better the BL linearity.

Underhung motors have very flat BL curves by nature, essentially not losing any BL at all until turns of wire start leaving the gap. However, the two goals of xmax and BL linearity are at odds with one another in an underhung design. To have great BL linearity and high xmax, you need a very large gap.

Does power handling come in to play much here? Underhung coils are going to be relatively smaller than overhung coils and all thing being equal would seem to handle less power. Does the underhung design just require less power, or does it have the drawback of not handling as much power?

 

[zebo 10+ year member]

and - most importantly, you are adding to the weight.
ever seen a shocker SIG? freggin top plate was like a few inches thick. i think it was an underhung design - but im not sure.

Whats the drawback of a driver being heavy (besides mounting concerns and performance of the vehicle)? My xxx mids are heavy as hell for a 7" speaker, but I love how they perform.

 

[req 5,000+ posts]

just for the fact that heavy woofers require bracing and all kinds of stuff. the cost is more because they require more steel too.

theres just more there to buy you know? sigs are freking HUGE, most of that is the top plate too (compared to a regular woofer)

i think theres a pic of a sig somehere in the "subs youve owned" thread. heres a vid of one.

http://www.woofervids.com/displayimage.php?album=128&pos=0

 

[squeak9798 5,000+ posts]

Also, when you are adding multiple top plates and slugs you are adding to the mounting depth of the driver, another drawback.

And production/material costs //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif XBL^2 can be implimented with little effect on production costs, since you are not "adding" anything (material wise) to a standard driver.

 

[zebo 10+ year member]

And production/material costs //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif XBL^2 can be implimented with little effect on production costs, since you are not "adding" anything (material wise) to a standard driver.

Well, you would be "adding" a larger\taller top plate, but thats far from adding a second top plate and more slugs.

 

[req 5,000+ posts]

Well, you would be "adding" a larger\taller top plate, but thats far from adding a second top plate and more slugs.

not really. its really quite a minimal addition - compared to a UH motor. unless you are doing somthing like the brahma or the XXX - the top plates on those are huge to say the least.

but as far as 'adding' material. its a minimal addition, yes - its another bit there, but the performance gain versus material cost is well worth the trade off.

technically - all they ahve to do, instead of cutting off the bottom half of the top plate that sticks out into the gap, they cut out the middle. thats about it //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

with whatever additions they have to the coil length and what not. my koda8 has a normal sized magnet\back plate, but the top plate is like 1\4" thicker than other 8's ive seen. and they are supposed to play clean very high - in fact, the great 8 challenge, they got the koda to 200w with zero distortion, and kept turning it up - and it died with NO warning because it has such linerarity. thermal RMS is 150 on them (i believe) and adire dosnt lie //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

they were all surprised when it went because there was no warning via distortion or anything. sweet little drivers.

 

[Steven Kephart 10+ year member]

About the only downside to XBL^2 compared to an overhung motor is a lower power handling due to the shorter coil height. However the benifits are well worth it. Plus I think that the Brahma, Tumult, and XXX all prove this isn't really too much of a problem. Just ask Scottie Johnson who has never burnt up a voice coil on his Brahma's, even though he burps them with 9 kilowatts of power each.

Steven Kephart

Adire Audio

 

[audioholic 5,000+ posts]

About the only downside to XBL^2 compared to an overhung motor is a lower power handling due to the shorter coil height.

xbl^2 helps the driver's efficiency though doesn't it? Which would offset the power handling issue, at least some.

Its hard thinking of a Brahma or xxx as having it's power handling hampered, they already handle a massive amount. heh

 

[zebo 10+ year member]

not really. its really quite a minimal addition - compared to a UH motor. unless you are doing somthing like the brahma or the XXX - the top plates on those are huge to say the least.
but as far as 'adding' material. its a minimal addition, yes - its another bit there, but the performance gain versus material cost is well worth the trade off.

technically - all they ahve to do, instead of cutting off the bottom half of the top plate that sticks out into the gap, they cut out the middle. thats about it //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

with whatever additions they have to the coil length and what not. my koda8 has a normal sized magnet\back plate, but the top plate is like 1\4" thicker than other 8's ive seen. and they are supposed to play clean very high - in fact, the great 8 challenge, they got the koda to 200w with zero distortion, and kept turning it up - and it died with NO warning because it has such linerarity. thermal RMS is 150 on them (i believe) and adire dosnt lie //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

they were all surprised when it went because there was no warning via distortion or anything. sweet little drivers.

Sorry I didn't clarify, I was just using a comparison to an overhung driver, underhung is a whole different story.

I'd never question the results of using a xbl^2 driver, I've owned a few and enjoy them all. A taller top plate is nothing in comparison to the advatages you gain by using a xbl^2 enabled motor.

Haven't played with the koda 8 yet, but I am sure I will get around to it. I'm sure it sounds great.