Adire's XBL2 versus TC Sound's LMT
12-23-2005 | 10:20 AM
#1
Adire's XBL2 versus TC Sound's LMT
Haven't seen a technical thread in this forum in awhile...
Anyone know the pro and con's of each? I know both of these motor design tries to maintain very linear movement, even at high excursion levels. I personally have experience with the XBL2 with my Brahma, and it was a very clean sounding sub. No experience with LMT though (or how similar/different it is from my RL-p's TC9 design)
Anyone know the pro and con's of each? I know both of these motor design tries to maintain very linear movement, even at high excursion levels. I personally have experience with the XBL2 with my Brahma, and it was a very clean sounding sub. No experience with LMT though (or how similar/different it is from my RL-p's TC9 design)
12-23-2005 | 11:15 AM
#2
12-23-2005 | 12:14 PM
#5
try researching.. atlas 15 will not be loud enough unless you put it in the rear deck which would be cumbersome at best. yeah gordon i read the thread recently, fun to read from educated people responding.
12-24-2005 | 02:06 AM
#19
Originally Posted by slickrick
what you're going to put in there is a quality system when you sell enough dope/ "loans" to afford one. 
Quality + Avi's systems = notgonnahappen.
not anymore ARCIFICATION COMING SOON!
12-24-2005 | 09:22 AM
#22
Originally Posted by Pearl96Max
Ummm didnt get done til late yesterday, then still had things to do...
Thats alright, just let me know when the best day will be next week. Otherwise I'll keep bugging you
12-25-2005 | 10:39 PM
#23
Joined: Apr 2003
Posts: 2,586
From: the OC & Silicon Valley
according to tc sounds, xbl^2 requires a very precisely set voicecoil. if the voicecoil is even slightly offset (as is usually the case in most drivers since they are glued by hand), it will result in the undesireable double-humped curve, not the seemingly flat BL curve that proprieters of the technology would have you believe
12-26-2005 | 10:11 AM
#25
Joined: Apr 2003
Posts: 2,586
From: the OC & Silicon Valley
that's just what i've been told. in fact i have a drive unit report with some graphs on a 10" brahma (from TC) showing this. if any of you want it PM me, but like i said it WAS from TC, a company that competes with others employing xbl^2...
12-26-2005 | 04:51 PM
#26
a section of Dan Wiggin's post:
So I guess each guy have their own opinion on each motor design.
LMT does flatten the BL curve. You also have massive power handling from the huge voice coil; it will take a ton of power to cook one!
However, it also carries with it several, IMHO fatal, drawbacks:
1. High moving mass. You start with an overhung, and add even more turns to it. And to get long stroke, you need a really long overhung voice coil to start with, which means the ends are so far out into the far fringe field you need a LOT of extra turns at the ends to add the proper amount of integration. And of course lots of turns means point 2 -
2. High inductance. Lots of turns = lots of inductance. This can be combated quite effectively with shorting rings; however, to lower the inductance linearly requires copper lining the gap, and that widens the gap. And you have to add a LOT of copper (in terms of thickness) to significantly affect inductance in the lower frequencies, meaning a really wide gap. Which brings us to point 3...
3. Low B field. Because you have extra layers in the voice coil, you need to widen the gap to account for the extra layers. This can double, or even triple the required width across the gap, meaning the flux in the gap will significantly decrease. Now, you get some total BL back from the extra turns, but it's usually better to get BL from B, not L. So you have to go to point 4,
4. Big motor size. To get lots of stroke in an overhung driver, you need a LOT of height. Imagine a 2" long voice coil with a 0.5" tall gap. Just at rest you must have 0.75" ((2-0.5)/2) of magnet stack, with ZERO motion. Now say you want 1" of backward stroke. That magnet stack is now 1.75" tall, minimum. Backplate thickness is added to it.
And it typically takes WIDE magnet stacks. Magnet force really goes as the area of the magnet, not the thickness. Since we're starting with really low B fields (see #3), we need a LOT of flux to make up to get anything decent in terms of B field in the gap. So we need to use bigger diameter magnets. Not only do we need a thick magnet stack, we need a wide magnet stack, which means a lot of extra weight, more volume occupied in your box, and limits how far down you can scale the design.
The most obvious example of this motor is the SoundSplinter RL-s design. A quick look at the T/S parameters will confirm that it has a VERY high moving mass (200+ grams for the voice coil alone, over 7 ounces!), and while it has a very long stroke (the voice coil is probably 3.5" long to reach the rated Xmax), it is VERY lossy; a BL of 13 N/A for a 3.5" long voice coil is extremely low (consider that the lowly Shiva Mark I, with a 1.5" long, 2" diameter voice coil - less than 30% of the copper - had a BL of 13 N/A).
However, it also carries with it several, IMHO fatal, drawbacks:
1. High moving mass. You start with an overhung, and add even more turns to it. And to get long stroke, you need a really long overhung voice coil to start with, which means the ends are so far out into the far fringe field you need a LOT of extra turns at the ends to add the proper amount of integration. And of course lots of turns means point 2 -
2. High inductance. Lots of turns = lots of inductance. This can be combated quite effectively with shorting rings; however, to lower the inductance linearly requires copper lining the gap, and that widens the gap. And you have to add a LOT of copper (in terms of thickness) to significantly affect inductance in the lower frequencies, meaning a really wide gap. Which brings us to point 3...
3. Low B field. Because you have extra layers in the voice coil, you need to widen the gap to account for the extra layers. This can double, or even triple the required width across the gap, meaning the flux in the gap will significantly decrease. Now, you get some total BL back from the extra turns, but it's usually better to get BL from B, not L. So you have to go to point 4,
4. Big motor size. To get lots of stroke in an overhung driver, you need a LOT of height. Imagine a 2" long voice coil with a 0.5" tall gap. Just at rest you must have 0.75" ((2-0.5)/2) of magnet stack, with ZERO motion. Now say you want 1" of backward stroke. That magnet stack is now 1.75" tall, minimum. Backplate thickness is added to it.
And it typically takes WIDE magnet stacks. Magnet force really goes as the area of the magnet, not the thickness. Since we're starting with really low B fields (see #3), we need a LOT of flux to make up to get anything decent in terms of B field in the gap. So we need to use bigger diameter magnets. Not only do we need a thick magnet stack, we need a wide magnet stack, which means a lot of extra weight, more volume occupied in your box, and limits how far down you can scale the design.
The most obvious example of this motor is the SoundSplinter RL-s design. A quick look at the T/S parameters will confirm that it has a VERY high moving mass (200+ grams for the voice coil alone, over 7 ounces!), and while it has a very long stroke (the voice coil is probably 3.5" long to reach the rated Xmax), it is VERY lossy; a BL of 13 N/A for a 3.5" long voice coil is extremely low (consider that the lowly Shiva Mark I, with a 1.5" long, 2" diameter voice coil - less than 30% of the copper - had a BL of 13 N/A).
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