LMS-5400 buy-in - Page 19 - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #181 of 312 Old 09-22-07, 07:45 PM
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Re: LMS-5400 / RL-p18" buy-in

That measurement was with an 80hz crossover, I only switched to 60hz after moving to this new place. FR of the VR3s is the purple line.



I've measured them to be flat to 30hz in room.

Quote:
Boundary gain could definitely increase their response around 100Hz.
The sub would be the one getting the most boundary gain, as it's in a corner. The baffles of the mains are 3.5' out away from the front wall and the nearest side wall to one of them is ~6' away.

Quote:
You say it is clean near the top but how clean, relative to what, and where is the evidence?
The inductance isn't bad and it's an 18" driver, so logically it should be pretty good. We can see from Ilkka's measurements that more linearity up top equates to lower distortion, and that an 18" is more capable than a 15" (no suprise). That some people claim it lacks punch would also point me to that conclusion, but again, the overwhelming factor in that would be their in room FR. Relative to what would be relative to whatever they were using as a subwoofer before.


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post #182 of 312 Old 09-22-07, 08:44 PM
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Re: LMS-5400 / RL-p18" buy-in

A few comments:

Ilkka is right on the money about the TC woofers having a more linear compliance (because of their 10" spiders with deep rolls) and this having an effect on the distortion measurement below resonance. However, if you have a spider that is more linear in one direction than another (which is many times the case) and you mirror image them, while things can be a little more symmetrical, you kind of get the worse of both rather than the best. I think this was Danís main point along with the idea that it doesnít help rocking as much as is though but that may be debatable.

Obviously the LMS 4" diameter >3" long coil with an average of >4 layers will have higher self inductance (and issues with modulation distortion etc) than a 3" diameter ~1.5" long 4 layer coil like an SDX15 or Tumult. What you're seeing in the 5400 is a difference in implementation of shorting rings etc., not proof that there isnít an issue with this with the LMS design.

The tough thing about shorting rings is that hey are not effective at low frequency without being really thick. Also, if you sleeve the pole (TC mentions using a 4.5" long copper sleeve) you're making an already very wide gap even wider (since copper has about the same DC permeability as air), further reducing the flux density which makes low frequency modulation distortion even worse. In short, it looks like TC was only able to get good performance with that huge motor structure (4 ~11" OD magnets and 4" coil) to get the Q back down to reasonable. The Eclipe 8200 has shorting rings are reasonable performance but isnít really well suited to its application (Mms too high, BL too low). And really needs the larger magnet etc. Basically, we're seeing more of an issue with differences in implementation and so you really cannot make accurate blanket statements about the technology.

With XBL^2, the rebate between the top plates is a natural place for a shorting ring (and a fairly thick one can be put there) without lowering flux density in the gap and adding a lot of cost. Ideally, additional shorting rings or a sleeve on the pole need to be implemented to balance things throughout the stroke of the driver.

However, since you have two gaps, it requires a lot of magnet to get the BL high enough and so you see a lot of 4 layer coils and such is all of the subs. Of course the best way to address the inductance issue is to have most of your BL coming form B and with a huge magnet system like the 4 HP (or some big Neo thing) you I'd be curious to see an XBL^2 driver with a longer 1-2 layer coil take on a super woofer.

The inductance graph shown by Dan is a simulation, not a measurement. However, you can see the effect of the shorting ring near the rest of the driver (i.e. between the top plates) and how it is effective more at higher frequency than lower. Of course, inductance increases inward into the motor because of the presence of more steel (making the coil essentially iron core instead of air core). In reality, things mighty be a hair better than this measurements because of some/most of the steel being in saturation, as this sim isnít taking into account the relative DC permeability.

The Klippel inductance result isnít at all directly comparable. It is a lumped model which is somewhat skewed by the low frequency side of things (required to get the high displacement). In short, if you make this graph flat, you could be putting too much copper in the motor (making the curve very non-flat in the range where the copper is effective). This is the case with some drivers like the Eminence Magnum and probably also some of the PE stuff.

The Ascendant Avalanche uses the exact sample coil and gap dims as a Brahma. They used a softer spider and use a slightly shorter different magnet (short magnet with a large bumped back plate) but Iíd expect the distortion performance to be basically identical (i.e. no revelation with the AVA15 tests). Itís a round wire coil that ~20% shorter than a Tumult and inductance, Max and power handling is a bit lower but they are really more similar than different.

Basically, yhere is a lot more to the total picture and root causes than most understand (including myself) but some guys here know enough ďto be dangerousĒ and campaign in a certain direction that is somewhat misleading.
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post #183 of 312 Old 09-22-07, 09:42 PM
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Re: LMS-5400 / RL-p18" buy-in

Quote:
Chris Brunhaver wrote: View Post
A few comments:
Hi Chris,

Hopefully you don't mind me mentioning that you used to work for Adire Audio, so that people know where we're coming from.

As you have probably noticed, I'm more of facts and objective data than marketing talk type of guy. I have no business interests towards any manufacturer making complete HT subwoofers or just drivers for them/car audio. Therefore I also do not campaign in any certain direction, other than towards good performance. Whether that road leads to TC Sounds, JL Audio, SVS, CSS, or any other company, doesn't really matter to me at all.

Quote:
Obviously the LMS 4" diameter >3" long coil with an average of >4 layers will have higher self inductance (and issues with modulation distortion etc) than a 3" diameter ~1.5" long 4 layer coil like an SDX15 or Tumult. What you're seeing in the 5400 is a difference in implementation of shorting rings etc., not proof that there isn’t an issue with this with the LMS design.
I don't think anyone tried to even hint that it would have lower inductance than, say, an XBL^2 coil. But the way they have handled and tamed it is the impressive thing. For example the MK1 Tumult clearly shows that low self inductance doesn't really count unless also other improvements (shorting ring etc.) are being applied properly.

Measurements show extremely low THD and very flat upper-end frequency response for the LMS coil. In the end that is much more important than just saying that the other design must have lower inductance due to shorter VC.

Quote:
The inductance graph shown by Dan is a simulation, not a measurement. However, you can see the effect of the shorting ring near the rest of the driver (i.e. between the top plates) and how it is effective more at higher frequency than lower. Of course, inductance increases inward into the motor because of the presence of more steel (making the coil essentially iron core instead of air core).
Thanks for the correction. I accidentally had the inward/forward stroke backwards.

Quote:
The Klippel inductance result isn’t at all directly comparable. It is a lumped model which is somewhat skewed by the low frequency side of things (required to get the high displacement). In short, if you make this graph flat, you could be putting too much copper in the motor (making the curve very non-flat in the range where the copper is effective).
Ok. I was a bit hesitant to post it because I wasn't sure how comparable they would be. I edited my post to reflect this new info.
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post #184 of 312 Old 09-22-07, 10:01 PM
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Re: LMS-5400 / RL-p18" buy-in

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but some guys here know enough “to be dangerous” and campaign in a certain direction that is somewhat misleading.
Out of curiousity, what direction has been misleading in this thread? The fact that companies don't share any REAL data is what creates these types of situations, and we are all in debt to Ilkka for actually going out and performing these tests. XBL^2 may have several theoretical and potential advantages, but Ilkka's testing of the Tumult and LMS goes to show that theoretical is one thing and real world is another. As an Avalanche 18 owner, I'm happy knowing its performance lies somewhere between the two for a fraction of the cost of either


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post #185 of 312 Old 09-22-07, 10:04 PM
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Re: LMS-5400 / RL-p18" buy-in

Quote:
The inductance isn't bad and it's an 18" driver, so logically it should be pretty good. We can see from Ilkka's measurements that more linearity up top equates to lower distortion, and that an 18" is more capable than a 15" (no suprise). That some people claim it lacks punch would also point me to that conclusion, but again, the overwhelming factor in that would be their in room FR. Relative to what would be relative to whatever they were using as a subwoofer before.
Someone just needs to send an Ava to (npdang ) for a Klippel. Its long overdue. Seems like more than a few people would be willing to chip in too.
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post #186 of 312 Old 09-22-07, 10:41 PM
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Re: LMS-5400 / RL-p18" buy-in

I did mention on the other thread that I did work for Adire and don't mind you mentioning it. Of course I haven't worked there is a couple of years but still am working the the speaker business at another company. However, I would think that this would help m credibility not hurt it, as I have had a lot of experience with these sots of drivers.

I'm not a hardcore engineering type and know more than some but an still in the "enough to be dangerous" category as well. I just think it is a mistake to come to conclusions about a particular technology or approach like LMS or XBL^2 from the particulars of a given driver and many times the dominant factors are the particular execution and trade-offs made.

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.

Klippel has real problems with a Brahma / AVA as these drivers as they are suspension limited enough that you can't get a proper BL curve fit. I don't think it will tell you what you're looking for and the distortion measurement approach is probably better.

Last edited by Chris Brunhaver; 09-22-07 at 10:52 PM.
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post #187 of 312 Old 09-22-07, 10:50 PM
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Re: LMS-5400 / RL-p18" buy-in

Quote:
Chris Brunhaver wrote: View Post
I'm not a hard core engineering type and know more than some but an still in the "enough to be dangerous" category as well. I just think it is a mistake to come to conclusions about a particular technology or approach like LMS or XBL^2 from the particulars of a given driver and many times the dominant factors are the particular execution and trade-offs made.
So are you saying that neither the AA Tumult nor the CSS SDX15 represent the XBL^2 properly?

If yes, may I enquire which driver does then?
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post #188 of 312 Old 09-22-07, 10:55 PM
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Re: LMS-5400 / RL-p18" buy-in

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A avalanche is essentially a Brahma and so isn't between a Tumult and 5400 at all.
The Avalanche 18 as compared to a Tumult 15 has a flatter top end, more displacement, and one would have to imagine less distortion at a given output level due to less travel being needed. Power handling is more than adequate for a LLT application, to which it is perfectly suited.

On top of that, when you take the price tag of the Tumult into account, based on Ilkka's tsting, I'd be nice if I said the performance wasn't exactly stellar.


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post #189 of 312 Old 09-22-07, 11:35 PM
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Re: LMS-5400 / RL-p18" buy-in

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The Avalanche 18 as compared to a Tumult 15 has a flatter top end, more displacement, and one would have to imagine less distortion at a given output level due to less travel being needed. Power handling is more than adequate for a LLT application, to which it is perfectly suited.

On top of that, when you take the price tag of the Tumult into account, based on Ilkka's tsting, I'd be nice if I said the performance wasn't exactly stellar.
Well do remember that the Tumult Ilkka tested was a Mk1. The Mk2 had at least this change:

"New for the Mark II design is an integrated shorting ring, lowering inductance even further and drastically lowering flux modulation. "

But who knows how significant the difference really is?

Quote:
Attached are some close mic FRs I took of the ported Avalanche 18 using an 80hz and 200hz crossover with all speakers off.
And here is one of my TC-2000.



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.

Quote:
The inductance isn't bad and it's an 18" driver,
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?
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post #190 of 312 Old 09-23-07, 10:10 AM
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Re: LMS-5400 / RL-p18" buy-in

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.
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