LMS-5400 buy-in - Page 20 - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #191 of 312 Old 09-23-07, 12:24 PM
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Re: LMS-5400 / RL-p18" buy-in

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So are you saying that neither the AA Tumult nor the CSS SDX15 represent the XBL^2 properly?
The the extent that XBL^2 isn't that well suited for this sort of application then yes. For small box subwoofers you need high BL, high Mms and high power handling and this isn't a great fit for XBL^2. It is better suited to moderately low BL and Mms and wider band drivers. If you jump over into the Fi forum and read Scott's comments (a man with a lot of experience with this stuff), I think that they are right on the money.

All of these use fairly high inductance copper coils and the Brahma / Avalanche could have used shorting rings and we gapped a little wide (though not as bad as a Tumult, which was gapped for an 8 layer flat wire aluminum RE XXX coil). At least the SDX15 has a shorting ring (to address this somewhat) but this could probably be improved somewhat (at a cost). The Mark II Tumults were quite similar to the SDX15 (with a hair bigger magnet) and the same comments apply. I didn't really get a chance to play with these (though a friend has one) but I don't think they had as good a spider or as rugged a build quality as the originals.

The Avalanche 18 was under motored, as is the new stuff from DIYcable. Steve, I'm glad you like your 20+ cubic foot EBS enclosure but I'll pass. This, in part, is why Adire didn't do one (i.e. Tumult of Brahma 18) and also that slow Maelstrom sales had scared them away from 18's.

Probably the best implemented XBL^2 design were the CSS FR125S (though it could use a bit more magnet and better shorting ring implementation) and RE XXX 6 (he original Extremis) which had the an awesome motor design though the mass was a bit high and soft parts ho-hum.

For subs, the Blueprint 01 (w/ XBL^2) / Koda motor was a pretty elegant solution. With some shorting rings and a bigger magnet, this 22 mm top plate ~16 mm Xmax solution was a bit of a sweet spot.

That is of course just my $.02. While they are cool to talk about and get a lot of attention, I'm not really in favor of the single huge subwoofer and would rather do a few smaller subs spaced throughout an HT.

Last edited by Chris Brunhaver; 09-23-07 at 06:22 PM.
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post #192 of 312 Old 09-23-07, 02:57 PM
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Re: LMS-5400 / RL-p18" buy-in

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Ricci wrote: View Post
Illka,
Are the enclosure/s for the LMS's done? Do you know what alignments you'll be going with and can you give an estimate of when the outdoor testing will take place? Sorry if you've already stated all of this info before.
No, I haven't stated any of this yet. I should have much more information in a couple of weeks. Please be patient.
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post #193 of 312 Old 09-23-07, 03:24 PM
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Re: LMS-5400 / RL-p18" buy-in

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Willy wrote:
Doesn't quite match up to Ilkka's measurements does it? Maybe we shouldn't go around posting our measurements taken by RS meters as the absolute truth.
Ilkkas measurements of two TC2k drivers show moderate inconsistencies - I have no reason not to believe your RS meter measurement as the truth.

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Doesn't appear to be any lower than TC-2K's either, yet you've said the TC-2ks inductance is unfortunate and it should be crossed over at 60hz. How is the Ava any different?
Not any lower than yours, no.


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post #194 of 312 Old 09-24-07, 08:07 AM
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Re: LMS-5400 / RL-p18" buy-in

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Chris Brunhaver wrote: View Post
A avalanche is essentially a Brahma and so isn't between a Tumult and 5400 at all. Tumult is is its bigger brother with significantly high power handling and stroke and BL but with somewhat higher inductance as well. The 5400 is something different altogether. There are some measurements of a Brahma 12" based ported woofer in Keith Yates "way down deep" article here:
http://www.ultimateavmag.com/feature...ay/index1.html
As you can see, it is similar to the Tumult with less output but also a little less upper end modulation distortion. Still, that inductive hump is there.
Hi Chris...is there any links or info you could share to corroborate this statement?

Because it certainly doesn't match up with the numerous emails and chats I've had with Chad regarding the Avalanche 18, its topology vs Adire's XBL^2 topology, differences between them, etc........and certainly it is NOT a Brahma with a different dress.

Obviously we would love to hear more details and learn more, but as soon as I get an OK from Chad to share some thoughts on the subject, I can post some of his comments on this.



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post #195 of 312 Old 09-24-07, 11:07 PM
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Re: LMS-5400 / RL-p18" buy-in

The plot thickens.


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post #196 of 312 Old 09-24-07, 11:15 PM
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Re: LMS-5400 / RL-p18" buy-in

ssabripo,

I guess the point is a bit moot because neither driver is available any longer. I currently have neither a brahma or avalanche to cut apart and show you.

However, if you have them side by side I think you'll find that while the avalanche has a larger single magnet (~220 mm OD) versus the ~178 mm triple stack a brahma has, they both have:

1. a 3" 2.8 ohm DCR copper coil of the same length and construction
2. the same top plate and rebate heights - same Xmax
3. probably the same cone/surround (depending on what version Brahma we're talking about),
4. the same basket,
5. the same lead wire
6. the same spider profile and manufacturer (except the avalanche spider is softer).

The avalanche T-yoke has a bump in it and the exact pole vent and extension are probably different and it has a carbon fiber dust cap but we're talking about basically the same driver, as I previously stated.

If you understand how XBL^2 works and that for a given Xmax and coil DCR there are particular coil and gap dims and ratios used, you'd see what I mean. Keeping these exact is important, especially with coil length being a little "twitchy".

Of course the Atlas is a little different (with the nifty shorting coil thing that Scott came up with).

I'm not calling anyone a lair but doubt to hear any comments/corrections. I wouldn't see why anyone would pipe in as Chad is no longer using this design and has a new business and product line to promote (which I hope he does well with). Still, what did he say was different and do you want him to prove it (as you suggested I do), or would you take his word for it?

Personally, I'd be more interested to hear about the monster 18" he using in his "conquest".
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post #197 of 312 Old 09-24-07, 11:20 PM
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Re: LMS-5400 / RL-p18" buy-in

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The plot thickens.
Indeed it does.
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post #198 of 312 Old 09-24-07, 11:30 PM
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Re: LMS-5400 / RL-p18" buy-in

While I'm hesitant to jump into this "measuring contest," there are some important things that have been mentioned that should be re-iterated. First and foremost, and as Ilkka has pointed out, these are relative comparisions in one specific situation. This was a test at a fraction of the rated excursion, low current as compared to some designs & uses, and no loading of any sort from a box. Some of these differentiators are less important in some cases, and more important in others. We should not get the illusion that we can characterize technologies with one set of measurements of specific examples. Ilkka is merely benchmarking and probing the performance of these specific drive units.

As with any technology and design, execution is everything, and the choices made in each example depend entirely on the priorities and goals of the designer. I have measured a my share of big coil, overhung motors of very different design types, as well as an assortment of XBL^2 designs, both commercial and custom built units. I have tested and used moderate excursion drivers that extend past 20kHz, as well as others with inductance humps and HF attenuation that left me head-scratching based on expected Le figures. The result entirely depends on the specific design.

We don't expect all ported enclosures to have identical sets of strengths and weaknesses, so why should we with a given motor topology. There have been plenty of bad examples of large, overhung drivers, but there also have been a few that performed fairly well. There are plenty of contrasting overhung motors of comparable excursion that range from HUGE inductive losses, and others that extend into the kHz range.

The LMS motor is an expensive way to get the result they did, but it obviously functions very well in this condition and listeners have been impressed with the results. Before any declarations are made, I would suggest getting the drivers in a box and outdoors as Ilkka intends to do. Things may change somewhat in different conditions.

There are some things that XBL^2 affords you in design flexibility just as an overhung does vs. underhung vs. LMS, etc. We still have to determine how well a particular driver works for the intended application in the desired enclosure, and if simple measurements track what we hear.

The Avalanche 18 is a long retired design, and we still haven't had anyone take one outdoors to measure in any enclosure. I did measure an Avalanche 15 and Atlas 15 long ago, but do not know with certainty if the 18 used the same motor as the 15, but I expect they are pretty close. I believe Chris was in some error in the similarities to the Brahma, as the Avalanche was a 3" VC and I thought the Brahma was a 2.5" VC, but I'm not certain.

In the end, there's a lot more to a driver than it's Le characteristic, even though it can throw a real hurdle in the way towards achieving great sound.

Mark Seaton
"Make no little plans; they have no magic to stir men's blood..." - Daniel H. Burnham
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post #199 of 312 Old 09-25-07, 12:01 AM
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Re: LMS-5400 / RL-p18" buy-in

What's both great and sad about this thread is that we wouldn't even be able to have this conversation if Ilkka didn't go out and take some measurements. If manufacturers can talk up their products for pages and pages, I don't understand why they won't share some simple measurements. It's like the growing population of professional boxers who can go on for hours about how they will dismantle their opponent in the ring but then avoid any and all contact once the bell rings. Then afterwards they talk about how great they were again. They do this to "stay in the game" longer and not get injured so they can keep making money.....probably very similar to driver manufacturers


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post #200 of 312 Old 09-25-07, 12:13 AM
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Re: LMS-5400 / RL-p18" buy-in

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SteveCallas wrote: View Post
What's both great and sad about this thread is that we wouldn't even be able to have this conversation if Ilkka didn't go out and take some measurements. If manufacturers can talk up their products for pages and pages, I don't understand why they won't share some simple measurements. It's like the growing population of professional boxers who can go on for hours about how they will dismantle their opponent in the ring but then avoid any and all contact once the bell rings. Then afterwards they talk about how great they were again. They do this to "stay in the game" longer and not get injured so they can keep making money.....probably very similar to driver manufacturers
EXACTLY...

Either put up or shut up...


Ilkka thank you very much for spending your time to test the woofers and give us some hard data.
 

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