Any 21’s on the horizon with XBL^X? - Page 3 - AVS Forum | Home Theater Discussions And Reviews
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post #61 of 171 Old 07-08-2008, 12:23 PM
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Originally Posted by bossobass View Post

Yes, that's my point. Theoretical arguments for the topology have been made many times, but virtually no measurements have been included.

It struck me when Ilkka told me the Tumult MKI is a 'bad' driver, meaning high in harmonic distortions vs other drivers. This seems to have been furthered by the results of the SDX drivers tests.

If individual implementations are to blame, I wonder what they may be? Sealed is as simple an implementation as it gets.

Bosso

Hi guys,

Some recent tests I have made with a Klippel Analyzer 2 have really opened my eyes with regard to simulations vs actual measured performance. It is really interesting to see the actual reasons for non-linearities instead of just measuring THD.

The AA Tumult and CSS SDX15 are definitely quite different in design and performance, even they both have an XBL^2 motor. The Tumult seems to be more on the lines of what XBL^2 supposed to be with regard to Bl linearity. The culprit is the lack of shorting rings which cause high Le(i) distortion (flux modulation) in mid and upper bass where the current is high. At lower frequencies the Bl and Kms non-linearities are dominant, and those ones are quite small with the Tumult.

I thought that the suspension would have been the culprit of the SDX15. It isn't. It's the Bl non-linearity instead. The XBL^2 motor doesn't work at all how it should be. Inductance based non-linearities are at lower level than with Tumult, but not much better than with regular overhang (say TC2k) design. There seems to be some strange design choices there, too.

I can shed some more light and show the measurements after I have discussed with the people involved.

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post #62 of 171 Old 07-08-2008, 12:36 PM
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Originally Posted by KyleLee View Post

I have done lots of unpublished research on linear designs, the xbl^2 in theory will measure much better than overhung models, i would argue perhaps the individual implementation were to blame?? Its hard to say. I have not done dynamic measurements on any xbl woofers myself, just calculations, but as long as the flux density is symmetrical about the y-axis from the center of the void between the gaps, you can get very linear results.

Kyle,

Did you Klippel/Dumax your own drivers (TC Sounds' drivers) during/after designing them? Just asking...

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post #63 of 171 Old 07-08-2008, 01:07 PM
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Illka: I Klippel'd my TC LMS 5400 18.... if you want send me a PM, and I will ship you copies of the 17 page report. BTW.... pretty awesome!

Ask your doctor if DIY is right for you. Side effects of DIY may include anxiety, elevated blood pressure, lightheadedness, rapid heartbeat, skeletal muscle flaccidity, euphoria, psychological dependence, insomnia, confusion, blurred vision, implusivity, uncontrolled or repeated movements.
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post #64 of 171 Old 07-08-2008, 01:24 PM
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There was also another person with Klippel results of the LMS 5400, he hasn't been around much lately though https://www.avsforum.com/avs-vb/member.php?u=7493699 he claimed he tested it at 26mm each way +/-1% total BL deviation, of course, the full results are also essential.
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post #65 of 171 Old 07-08-2008, 01:24 PM
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Quote:
Originally Posted by bossobass View Post

I wasn't referring to LMS, but instead, a standard overhung driver, as in virtually every driver tested, commercial or otherwise.

I'm not sure what the distinction is between a licensed XBl^2 motor and a Wiggins designed XBl^2 motor, nor am I sure I understand what the age of the design has to do with anything (which is a little over 5 years, to answer your question).

If you're saying that any split gap motor can be called XBl^2 then the license agreement seems lacking.

The motor topology is what is licensed. As Ilkka has well demonstrated, there is more to a subwoofer than linear BL vs. excursion, even though it is a very important contributor. Linearity of the suspension, operational noises, mechanical resonances, thermal dissipation and linearization of inductance and B field with varying power and excursion are all additional contributors to the quality of the end result. Of course even then there is a big difference in a driver with a moving mass of ~300g vs ~80g and what they will be best suited for.

In the past 2-4 years Dan has been doing LOTS of commisioned research into surround design, spider design, the use of shorting rings, etc., etc., often for non-music related operation. I'm not saying Dan is the only one who knows how to design a quality driver. What I am saying that Dan's knowledge and input on a driver's design extends well beyond the rebates in the pole & top plate.

Even then, at some point the paying customer will get what they ask for, or what they are willing to pay for. Trade offs of some level are made in every design.

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Bottom line is that very few Wiggins subwoofers have been tested in a way that gives a frame of reference. There are theoretical advantages and they've been discussed many times. Dan himself has made the case you're suggesting, by mentioning the SDX and AVA drivers, that the XBl^2 license means basically nothing, specifically in the case of the Avalanche drivers, which also have never been tested.

Again, it was never said that the license "means nothing." The license means the motor topology was used as the licensee saw fit, and that an XBL^2 motor can allow for unique shaping of the BL curve, with the potential for very flat BL over some range of excursion. This says nothing of the cone, frame, surround or spider used and what their limits are.

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PA-SchmeeA and App-Schmapp. Put that driver in 5 cubes and let someone listen, then switch the driver with the Mael-X, match FR with L/T and match levels and tell me who heard what or how one was better because it's specified for HT apps.

Saying that one has more headroom above X and the other has more headroom below X, or one uses a smaller amplifier than the other, etc. is irrelevant.

If you draw the in-room extension line at 10Hz and listen at average levels in 3-4,000 cubes, there will be no discernible difference.

Not really sure what your point is above. My point was that there are efforts made in either driver which would be excessive in certain applications, and are the reason for the huge price differences. The advantages are still there. The buyer has to decide whether the differences and trade offs justify the price to them. If drivers were compared where one was being grossly over-driven, expect it to sound worse, regardless of how well it works in the first 10-20mm of Xmax.

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I understand the problems you face having to work within a strict set of parameters, but no such problems exist in DIY. That's why my subs are Tumult based and yours are not.

The pesky reality of actual availability of good performing XBL^2 drivers 2-3 years ago is the reason the SubMersive doesn't use an XBL^2 driver. I shelved a more expensive and slightly larger design as I couldn't rely on the potential suppliers at that time. Times have changed, and some variation of that product concept will come to life in the not-too-distant future.

I have sampled and rejected plenty of XBL^2 drivers, just as I am using plenty in upcoming designs for AV123, TCA & myself. I'm also still using conventional motor drivers where XBL^2 options had not yet exceeded the performance of well optimized, conventional drivers, or where I haven't had time/money to develop the right custom driver for the use. XBL^2 motor or not, a driver still has to be well optimized for its use.

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Tumult is a great driver. I've said so many times. I'm just not sure what XBl^2 has to do with that fact vs the same driver with an overhung motor.

you then followed up with:

Quote:
Originally Posted by bossobass View Post

It struck me when Ilkka told me the Tumult MKI is a 'bad' driver, meaning high in harmonic distortions vs other drivers. This seems to have been furthered by the results of the SDX drivers tests.

So is the Tumult a great driver or a bad driver? Ilkka's independent testing confirms what has been discussed here and Dan has posted long ago about the design of the Tumult. While many get caught up in a few numbers dependent on other factors, Ilkka's full set of response testing clearly illustrates that the Tumult has higher excursion and suspension linearity than the SDX. Look at the response below 30Hz as the level is increased. You can clearly approximate the excursion required for those levels and can see the lack of compression below 20Hz, which requires that BL be maintained, as well as reasonably low compression overall.

Since we aren't seeing much compression, that suggests that the distortion is related to other non-linearities, especially as excursion is relatively low above 50Hz. The obvious correlation of the distortion rise and its higher order content with the inductive roll off of the frequency response suggests that inductance & current modulation are prime suspects. Ilkka's more recent testing confirms that diagnosis. I found very similar distortion behavior in the Avalanche & Atlas-15 drivers I tested long ago.

In the end, we come back to the fact that the full execution of any design is key, and no single wonder-technology guarantees a great end result. Different motor designs, methods and techniques simply give us more options and flexibility in getting to that end goal.

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post #66 of 171 Old 07-08-2008, 01:59 PM
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Oh boy.... you are cutting loose the dogs now Ilkka.

I don't think this has anything to do with 21" subs though. Maybe the topic should be steered back on-subject.


No news on the Sicko. I need to get the latest renderings posted. We had to make some changes to the motor because of crazy prices on the machine work. Once I'm sure we have something solid I'll update you guys.

In terms of the PASUB, it sure looks cool but I don't have anything to do with the project. As Mark says, you should use the right tool for the job. A hammer may be great for nails but it sucks at driving screws. It may be the best hammer money can buy, but I'd take the Dollar store Chinese screwdriver over the Snap-On hammer any day of the week if the job required a screwdriver.

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post #67 of 171 Old 07-08-2008, 02:06 PM
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Originally Posted by Kevin Haskins View Post

Oh boy.... you are cutting loose the dogs now Ilkka.

Bad, bad doggie! Play dead! -- blam! -- yipe! Good dog!

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post #68 of 171 Old 07-08-2008, 02:22 PM
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I think we found a dog catcher..


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post #69 of 171 Old 07-08-2008, 02:26 PM
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Quote:
Originally Posted by Mark Seaton View Post


So is the Tumult a great driver or a bad driver? Ilkka's independent testing confirms what has been discussed here and Dan has posted long ago about the design of the Tumult. While many get caught up in a few numbers dependent on other factors, Ilkka's full set of response testing clearly illustrates that the Tumult has higher excursion and suspension linearity than the SDX. Look at the response below 30Hz as the level is increased. You can clearly approximate the excursion required for those levels and can see the lack of compression below 20Hz, which requires that BL be maintained, as well as reasonably low compression overall.

Actually, I don't look at Ilkka's maximum sweeps and related THD, generally speaking. They aren't realistic. The CEA test, for example, will yield 4-6dB more output with comparable THD. When I look at the 100dB sweeps, what I would consider to be the maximum torture test for a single 15" sealed subwoofer, I see better overall performance (Ilkka's chosen test BW) in the SDX, THD-wise. I see better yet overall performance from the TC2K 2X15 105dB sweep/THD numbers.

Bosso
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post #70 of 171 Old 07-08-2008, 02:39 PM
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Originally Posted by bossobass View Post

Actually, I don't look at Ilkka's maximum sweeps and related THD, generally speaking. They aren't realistic. The CEA test, for example, will yield 4-6dB more output with comparable THD.

That's power compression in play there, my friend. VC will heat up, Re will go up, power will go down, output will go down. With a short CEA-2010 burst signal power compression isn't that much of an issue.

Quote:
When I look at the 100dB sweeps, what I would consider to be the maximum torture test for a single 15" sealed subwoofer, I see better overall performance (Ilkka's chosen test BW) in the SDX, THD-wise. I see better yet overall performance from the TC2K 2X15 105dB sweep/THD numbers.

Bosso

This part of your message escaped me?

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post #71 of 171 Old 07-08-2008, 02:42 PM
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There used to be a really good write up of various coil topologies somewhere...was it ROE? Split-coil is similar to XBL but has some notable differences as does LMS. Let me see if I can dig that up for those of us that need a refresher course.

I don't see where the split coil design would have to be heavier per se at-least compared to the heavyweight LMS coil. Granted the XXX coils are pretty friggin heavy the MMS on the 18 is around 580g. The LE measured by a WFT3 was 3.88mh, but who knows how accurate that is. I need to get a laptop and REW going!
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post #72 of 171 Old 07-08-2008, 03:09 PM
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Originally Posted by michael hurd View Post

Illka: I Klippel'd my TC LMS 5400 18.... if you want send me a PM, and I will ship you copies of the 17 page report. BTW.... pretty awesome!

Those results would sure be nice to see published to all of us, than only for some underground league of subwoofer guru members.
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post #73 of 171 Old 07-08-2008, 04:16 PM
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Originally Posted by Mark Seaton View Post

the pricing I have heard for general sale of the drivers is in the $500-800 range for the 15-21" drivers.

Much less unexpected than the original comments about pricing.

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Originally Posted by Mark Seaton View Post

As the name cleary implies, "PASUB" makes drivers for pro audio. A Maelstrom and other XBL^2 drivers will be much better optimized for typical home use where multi-kW power handling and the lower weight of Neodymium have less value.

I'm not sure that's so true for a hobbyist. (For a manufacturer, sure, though perhaps the lower mass of neo will become a virtue thanks to rising energy costs at some point.) The typical DIY application I'd see for a driver like the PASub 21 or the B&C 21SW150 is a sealed box under 5 cubic feet or so, with heavy bass boost and powered by a multi-kW amp. In such a scenario, the "pro" advantages (low mass for easier install/carrying - lining up something like an Ava18 or Maelstrom-X in a flush-mount baffle is NOT fun - better thermal management for less power compression at high power) seem to dovetail exactly with pro audio design requirements.

Could equal or better performance be had with a smaller driver of the same Vd in the same-sized box? Maybe. Cost would likely be lower as well, and with a smaller driver one would have more form-factor options, too. But Also, there's no denying that a gigantic woofer looks really cool!


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Originally Posted by Ricci View Post

Correct and there's LMS also. Seems like there was one more...

The fourth, Hyperdynamics' design, is a riff on the split coil. In addition to other possible differences of which I'm not aware, the current runs in opposite directions in each coil, largely canceling out inductance. This design is used in the Velodyne DD-series subs, the JBL platform that includes their Vertec pro subs and WGTi car drivers, and some JBL studio monitors. Possibly others, though I am not aware of them.

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Originally Posted by bossobass View Post

It struck me when Ilkka told me the Tumult MKI is a 'bad' driver, meaning high in harmonic distortions vs other drivers.

I have my theories on that. Luckily, Ilkka already covered the big one, quoted infra:

Quote:
Originally Posted by Ilkka Rissanen View Post

The culprit is the lack of shorting rings which cause high Le(i) distortion (flux modulation) in mid and upper bass where the current is high.

Ilkka, ever get a chance to look at the JBL W15GTi?

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post #74 of 171 Old 07-08-2008, 04:21 PM
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Originally Posted by Ricci View Post

There used to be a really good write up of various coil topologies somewhere...was it ROE? Split-coil is similar to XBL but has some notable differences as does LMS. Let me see if I can dig that up for those of us that need a refresher course.

I don't see where the split coil design would have to be heavier per se at-least compared to the heavyweight LMS coil. Granted the XXX coils are pretty friggin heavy the MMS on the 18 is around 580g. The LE measured by a WFT3 was 3.88mh, but who knows how accurate that is. I need to get a laptop and REW going!

Dan did a write-up comparing the different linear topologies on soundillusions.net. I will try to find it when I get off work.

XBL^2 makes the most sense IMO because it doesn't put the flattening capabilities in the coil. Instead it puts it in the non-moving parts where it has little effect on other parameters. The other topologies that use the coil for it's flattening techniques force the speaker engineer to work around the extra Mms and Le. Now those may not be a problem in all designs, but it does make the topology less flexible to use. That's why XBL^2 can be implimented in midrange drivers and now tweeters.
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post #75 of 171 Old 07-08-2008, 06:07 PM
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Originally Posted by Steven Kephart View Post

Dan did a write-up comparing the different linear topologies on soundillusions.net. I will try to find it when I get off work.

XBL^2 makes the most sense IMO because it doesn't put the flattening capabilities in the coil. Instead it puts it in the non-moving parts where it has little effect on other parameters. The other topologies that use the coil for it's flattening techniques force the speaker engineer to work around the extra Mms and Le. Now those may not be a problem in all designs, but it does make the topology less flexible to use. That's why XBL^2 can be implimented in midrange drivers and now tweeters.


In fact many of the comparisons he made between LMS and XBL^2 are not accurate and i will be glad to refute claims i disagree with... mind you, i don't disagree with all of them.

its not very obvious which one is better, less so when you start to formalize parameters like magnet size, gap widths and xmax, but a few things do come clear, i'm not making any public statements about that today, but i have some very interesting result that until now... no one i know has done!

But because there are other differences, it's not a winner take all because there are advantages that are not found on both sides, so its impossible to say this advantage is better than that advantage when they don't really compare.

I will make my objective results available to the public probably in 09... xbl^2 and LMS are just 2 examples mind you, many more exist.
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post #76 of 171 Old 07-08-2008, 07:07 PM
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Quote:
Originally Posted by KyleLee View Post

In fact many of the comparisons he made between LMS and XBL^2 are not accurate and i will be glad to refute claims i disagree with... mind you, i don't disagree with all of them.

its not very obvious which one is better, less so when you start to formalize parameters like magnet size, gap widths and xmax, but a few things do come clear, i'm not making any public statements about that today, but i have some very interesting result that until now... no one i know has done!

But because there are other differences, it's not a winner take all because there are advantages that are not found on both sides, so its impossible to say this advantage is better than that advantage when they don't really compare.

I will make my objective results available to the public probably in 09... xbl^2 and LMS are just 2 examples mind you, many more exist.

Well I did some searching and couldn't find that thread. So maybe you could list what you believe the differences are?

Back before Dan released the details on how XBL^2 got a flat BL curve, there were several of us discussing different ideas on how to achieve it. One idea I mentioned to Dan was controlling the windings on the coil to accommodate for the drop in BL over excursion. I envisioned an hourglass shaped coil. This of course is very similar to what LMS does, but this was back around 02 well before LMS was released. Dan said he and David Hyre looked into this already but dismissed it because of so many inherent flaws. They instead came up with XBL^2 which as he said would work much better.
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post #77 of 171 Old 07-08-2008, 08:31 PM
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another day, in another thread... we're a bit off topic.
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post #78 of 171 Old 07-08-2008, 08:56 PM
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So people as you all seem to be doing alot of posting and reading...how about reading the subject ...

This is a thead about Kevin's upcoming driver(s).

Ask yourself mortal , do you have as much displacement as me ? The answer is no unless you have a Windmere fan sub.
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post #79 of 171 Old 07-08-2008, 10:49 PM
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I thought this was about 21's with XBL? Apparently Kevin isn't the only one that fits that category.
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post #80 of 171 Old 07-09-2008, 04:59 AM - Thread Starter
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Hey Army,

I'll take the blame here; I felt this to be sufficiently unique that further qualification in thread' title wasn't necessary. Upon inception, this thread was mocking the 18 thread of similar name and my intent was to capture the enthusiasm for Kevin's impending 21 master of doom.

Perhaps I shall tweak' the thread title ever so slightly?

Larry

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I thought this was about 21's with XBL? Apparently Kevin isn't the only one that fits that category.

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post #81 of 171 Old 07-09-2008, 05:00 AM
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Don't worry, it was a joke
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post #82 of 171 Old 07-09-2008, 05:03 AM - Thread Starter
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Cool, sometimes I'm sarcastically challenged
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post #83 of 171 Old 07-09-2008, 05:13 AM
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Naw, its my bad, I forgot to use an emoticon
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post #84 of 171 Old 07-09-2008, 06:30 AM
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well, I don't have a Klippel machine, but I can tell you that so far, between the Avalanche 18, and the Maelstrom X 18, I cannot hear not one bit of acoustical difference, and they both clip the amps at the same level, etc.

Carl Kennedy from JL Audio offered me to use his Facility some time ago if I ever wanted to do a Klippel test, etc, so I may take him up on that, and get some measurements on the avalanche and Maelstrom.
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post #85 of 171 Old 07-09-2008, 07:45 AM
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Here is the link to the comparison of motor topologies. I wouldn't take it as gospel, but there is some good info there.

http://www.soundsolutionsaudio.com/f...opic=9421&st=0

Thanks DS-21 the dual gap design used by JBL was what I was thinking of as the fourth.
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post #86 of 171 Old 07-09-2008, 08:02 AM
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Huh, its a nice little summary, but I was hoping for a little more to chew on.
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post #87 of 171 Old 07-09-2008, 08:16 AM
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Originally Posted by armystud0911 View Post

Huh, its a nice little summary, but I was hoping for a little more to chew on.

I posted this a while back:

http://forums.audioholics.com/forums...&highlight=LMT


some XBL^2 stuff from Dan:
http://www.adireaudio.com/Files/XBL2DetailsPaper.pdf
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post #88 of 171 Old 07-09-2008, 08:24 AM
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We can mull through all the differences in the different techniques all we like. In the end, you can screw up any of them!

Likewise, some are better when different parameters are preferred. Relatively low Mms & high BL takes a bit of trickery with LMS and I expect would get expensive. Many designs require high mass, but if you have high Mms from a big coil, you automatically have to watch out for Le & flux modulation problems. Most of these designs tend toward different strengths vs. cost to implement, and there are still plenty of times when a well executed, overhung coil can do the job just fine.

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post #89 of 171 Old 07-09-2008, 08:44 AM
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Which is part of what makes the LMS 5400 such an enigma, it has ok efficiency and high mms (which its supposed to), but also has very high BL, low inductance, how? Thilo really showed his colors with that woofer, there just isn't much wrong with it at all. Of course, then you have acoupower showing us all what a traditional topology can do. Seemingly every bit as nice of excursion, low distortion, low inductance, another brilliantly engineered sub.
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post #90 of 171 Old 07-09-2008, 09:03 AM
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Hi all, Mark Seaton pointed to this thread, maybe I can shed a little light on this...

1. The prices listed are for OEM quantities; the original poster contacted us asking about large OEM quantities. They are not representative of individual purchases, and for him to represent those prices as street prices is disingenuous.

2. Licensees and designs are two different things. There are several larger licensees of XBL (including Bohlender Graebner, Solidex and Microsoft) who sometimes design their own drivers. Sometimes they ask us to help, sometimes not. Likewise with smaller licensees - it is up to the licensee to decide. We do include a few free driver designs with the license, but many choose to pay for driver development beyond the initial few.

3. If you have questions about technologies/tradeoffs, please feel free to ask. Static-type measurements really aren't too representative of what you see in the real world. Dynamic tests like Klippel, burst tests, and other highly dynamic tests are much better to get an idea of what's going on. You'll often find that a driver that measures nicely with steady-state THD+N type measurements is audibly a bad performer. It's because of the dynamic nature of sound.

4. As a follow-on to dynamic testing, note that BL AND Re changes with power and position will change the effective Qes (and hence Qts) of the system. As the average BL drops (from stroke), the effective Qes increases. As the voice coil heats, Re goes up and so does Qes. Often it's best to design a driver that isn't the absolute best performer at low-to-mid levels because at high levels it will fall apart. It's a balancing act, and should be designed with the general use and application of the client in mind. There is no perfect driver; there IS a perfect driver for a specific application.

5. THD+N testing should be taken with a grain of salt; make that a block of salt. Not just in the difficulty of doing it properly (the noise portion is a serious issue), but in terms of the impact of audibility. In fact, a driver with 10% THD+N can often sound a lot cleaner AND better than a driver with 1% THD+N. It's not the level of THD+N that is so important as it is the ratio of the harmonics and the way those ratios scale with power (see Geddes et al).

Anyway, I'll try to pop in to this thread once in a while, if you have questions please feel free to ask.
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