Lambda motor vs. XBL^2 motor vs. any other motor - diyAudio
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Old 4th November 2008, 02:09 PM   #1
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Default Lambda motor vs. XBL^2 motor vs. any other motor

Hello

Not intending to start a war between Nick and Dan, or any fight between the owners, resellers and users of these respective technologies. So please, be polite and informed if you decide to comment.

My starting point is that I'm looking for a driver for a most ordinary home subwoofer in a sealed box. Looking at the 12" Peerless XLS driver, and what mr. Linkwitz has written about it, I can't help but notice the harmonic distortion it produces with a 20Hz or a 30Hz sine signal.

http://www.linkwitzlab.com/thor-measmt.htm and scroll down about halfway.

I'm interested in knowing if either the Lambda motor or XBL^2 motor is addressed at specifically reducing this kind of distortion. That is, 1) at low frequencies and 2) in a sealed box. Or if they, as a side effect of some other primary aim, reduce the harmonic distortion with 20Hz or 30Hz sine signal.

I'd ike to know, how are the design aims of said motors different, and while they surely excel at different situations compared to each other, what are these situations exactly? And, are there other specialized woofer motors, and how would you rate them?

Then finally comes the question whether I should replace, in my plans, the 12" Peerless with the Shiva's newest incarnation or some 12" driver in AE lineup, or some altogether different driver. I like the way mr. Linkwitz analyzes the power requirements of the driver in a smaller than optimal box, and I also plan to use EQ.

I have about 240W of amplifier power to spare (RMS into 4 ohms), so do not suggest any "three inch linear excursion and 2kW power handling" wonder drivers. I also plan to find some kind of a sweet spot with regards to the budget.
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Old 4th November 2008, 03:02 PM   #2
Luke352 is offline Luke352  Australia
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Some others drivers with a different then usual coil design is the Differential Drive drivers from JBL these are mostly from there Pro Audio range but you can also find it in there W Gti car audio range, I'm not sure if you can find it in any of there Home Audio/Theatre drivers.

Here is the white paper http://www.jblpro.com/pub/technote/J...-33%20rev3.pdf

There are several benefits to the design which the white paper covers.

One benefit is it allows the drivers to still have quite high sensitivity, unlike some XBL^2 drivers I've seen.

Here is a link to a pdf with the specs for the JBL W15Gti if you want to model it up and see how it models, (the enclosure recommendations are obviously for in car so won't have much relevance for your purpose.) http://manuals.harman.com/JBL/CAR/Bo...5GTi_rev_f.pdf
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Old 4th November 2008, 04:28 PM   #3
jbell is offline jbell  United States
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I'm a fan of the HSU 12" driver. It is an XBL2 motor, but is an overdamped driver. This reduces distortion dramatically, but means that typically you need to add a little eq in the 20hz range to bring back to flat.
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Old 4th November 2008, 06:12 PM   #4
MaVo is offline MaVo  Germany
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Double the drivers, which halves the excursion at the same level, equalling lower distortion.
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Old 4th November 2008, 10:50 PM   #5
simon5 is offline simon5  Canada
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Hi Thinkcat,

Let compare AV12-X and Shiva-X.

I'd say that roughly, XBL^2 attempts to lower distortion by linearizing the BL curve as most as possible, without increasing mms, with clever design. XBL^2 also help a design to achieve a higher xmax than usual. Le is low at 0.9 mH.

On the other hand, Acoustic Elegance prefer to lower distortion by lowering Le as much as possible. They do that with copper shorting rings by using a full copper sleeve on the pole piece. Le is VERY low at 0.196 mH.

I'd say that both are good drivers, and to me, several notches above the Peerless XLS line. I'd think they would achieve much lower distortion than the Peerless, but then, someone would need to test it.

Let compare both drivers to the good old XLS.

XLS got a Le which is 4.2 mH, poor versus 0.9 mH and very poor versus 0.196 mH. Power handling is 350W versus 600W and 1000W. xmax is 12.5 mm versus 27 mm and 23 mm.

It can't compete, really !
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Old 5th November 2008, 03:16 PM   #6
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Quote:
Originally posted by MaVo
Double the drivers, which halves the excursion at the same level, equalling lower distortion.
But let's assume the case is that I want two boxes, both maybe 50 litres in size (like Linkwitz's Thor subwoofer). That mostly means 12" or in some cases 10" drivers. How can I, from there on, improve the quality of the reproduced sound? Dipoles are out of the question for now.

If I was contracting for a basement movie theater, I would possibly like very much the B&C 18TBX100, BMS 18N850V2 or McCauley 6174, as suggested in the thread at

$1000 to spend on 12" or 15" Subwoofer

But the case is, I am looking for a good sub for my smaller than average living room. Primary aim is listening to music, i.e. a clean and articulate sound. Movies will come second, or have to get along with what is available in terms of power and displacement.
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Old 5th November 2008, 03:28 PM   #7
jbell is offline jbell  United States
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I've used these for subs in HT and in church's, up to 40x80. Only real problem with this design is it needs some more weight to keep it from jumping in the air. (had to add 10lbs of weight to the inside of cabinet) Sitting on it also works well.....

This design came directly from the good Dr. himself.
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Old 5th November 2008, 08:11 PM   #8
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Quote:
Originally posted by jbell
I'm a fan of the HSU 12" driver. It is an XBL2 motor, but is an overdamped driver.
Where could I see these drivers for sale to Europe or Scandinavia? On the manufacturer's homepage ( http://www.hsuresearch.com/ ) I could only see complete speakers and subwoofers. Maybe I did not look closely enough, but on a quick second look I was still unable to locate information on bare drivers.

But anyway, for the purpose of this thread, my biggest worry is, that does the ability to play at high excursion somehow degrade the sound quality of a driver? Basically I've began to think that yes, it does.

http://www.diyaudio.com/forums/showt...92#post1587892

http://www.zaphaudio.com/lowxmax.html

Therefore I'd love to know, which "famous" or "good" or "well known" drivers are "safe" from this kind of degradation? Are all, some or none of XBL^2 drivers? The new Shiva-X? Original 15" Tempest? Are all, some or none of Lambda / AE drivers? Is the Peerless XLS "safe" or not? Who can I trust these days anymore?
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Old 5th November 2008, 08:16 PM   #9
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Found it!

http://www.hsuresearch.com/products/asw-1203.html

But I'm still worried about the quality question.
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Old 6th November 2008, 10:57 AM   #10
simon5 is offline simon5  Canada
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Well, you want to play 20 Hz and 30 Hz. That needs massive amounts of air to be moved, or you will not be able to hear it. You will only barely feel it, by the vibrations.

Yes, usually higher xmax drivers will show higher distortion, but still, you need to factor in the performance/price ratio in this.

You could build yourself a huge array of top-of-the-line Acoustic Elegance TD15M which are 15" drivers flat to 4 kHz with 6 mm of xmax and 98 dB of efficiency with 1 watt.

At 309$ per driver, you'd need 4 of these to achieve the same loudness at 20 Hz versus a single Acoustic Elegance AV15-H which will do the job fine at 219$ per driver.

As someone said earlier here, then you could double up, or more.

Since you're looking at 20 Hz and 30 Hz, you better stick with true subwoofer drivers IMHO. If it's not loud enough or the distortion is too high, then use more true subwoofers drivers. It will be cheaper, louder, perform better and have lower distortion overall.
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