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Re: LMS-5400 / RL-p18" buy-in

o quite different than the Tumult or the TC-2000s I measured last time. Then there is also power compression. The massive 4" VC with titanium former should perform really well when some real men power will be utilized. Then we will know more about the real difference to "weaker" drivers.
:praying: for a GP session this fall.
 

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Re: LMS-5400 / RL-p18" buy-in

Ilkka, the free air measurements of the two TC2k drivers appear to be better behaved at the top end as compared to the measurements while in an enclosure. Why is that?

According to Dan Wiggins (who has kind of been taken down a notch in my mind after your testing), inductance was supposed to be a big problme for LMS motor technology, but clearly that doesn't seem to be the case. So it begs the question of whether or not this motor technology could be put to use to make an ultimate midrange/midwoofer. I'm still puzzled why the Tumult had such poor inductance when the coil should theoretically be pretty short. Also, Dan appears to be off the target on his commentary on dual spiders as well.
 
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Re: LMS-5400 / RL-p18" buy-in

YAH RIGHT, lok what i did to mine, and they where the oem10 passives with extra strong cones. dual passive enclosure with a single OEM10 both passives went. took very little figer presure to turn the cone out like that afterwords

I guess those ti cones would help then :scratch:
 

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Re: LMS-5400 / RL-p18" buy-in

Ilkka, the free air measurements of the two TC2k drivers appear to be better behaved at the top end as compared to the measurements while in an enclosure. Why is that?
Does it really? ;) If you look at the THD graphs below, you can see that the upper one does have a dip at around 18-21 Hz (orange curve). That's the Fs of the driver (18 Hz by the spec). THD dips there because current varying inductance Le(i) (also known as flux modulation) dips there too. Impedance peak is at Fs, so the current through the VC will be low.

When put in an enclosure, Fb raises up. Now the impedance peak is at around 40 Hz. That's the Le(i) and THD minimum point now. Sealed enclosure also prevents back wave cancellation, unlike free-air "alignment". Combine these two and you'll realize that it only seems like the driver would behave better at the upper-end while measured in free-air. Also notice that the absolute sound pressure levels between these two measurements can not be compared.





According to Dan Wiggins (who has kind of been taken down a notch in my mind after your testing), inductance was supposed to be a big problme for LMS motor technology, but clearly that doesn't seem to be the case. So it begs the question of whether or not this motor technology could be put to use to make an ultimate midrange/midwoofer. I'm still puzzled why the Tumult had such poor inductance when the coil should theoretically be pretty short.
It seems that inductance and its effects on performance are probably one of the hardest things to simulate properly. The most commonly used, Le at 1 kHz, value is totally useless with subwoofer drivers. The more accurate Ls, Lp, Rp triplet seems to work pretty well with more traditional motor topologies, but not with LMS (or else the figures given by the TC Sounds are wrong).

It is also important to notice that the inductance varies with both excursion (Le(x)) and current/frequency (Le(i)). Here's an inductance simulation done on the AA Tumult 15D2 MK2. It was on AA's website while it was still up. Notice how the inductance raises really high during the backstroke, especially at low frequencies. That is normal behaviour since during the backstroke there is more iron inside the coil.



Below is a Klippel analyzer measurement on an Eclipse LMT SW8200 (by npdang at Diy Mobile Audio). It shows that the inductance variation with the excursion is really small. Maybe this is one of the reasons why the LMS seems to have such a good upper-end performance?

edit: These two inductance measurements are NOT comparable.



Also, Dan appears to be off the target on his commentary on dual spiders as well.
Could you refresh my memory?
 

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Re: LMS-5400 / RL-p18" buy-in

Ilkka, I should have been more specific. I wasn't referring to the higher frequency distortion, but the actual FR. In the free air measurements, the dropoff at 100hz is less than it is when the driver is in an enclosure.
Yes, that's the Qtc in effect. In free-air/IB the Qtc will be close to Qts, meaning very low (~0.3), but in an 70 liter enclosure (my own dual subwoofer), the Qtc will be around 0.7. That is what makes the frequency response to change its shape.
 

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Re: LMS-5400 / RL-p18" buy-in

I saw this the other day: http://forums.audioholics.com/forums/showthread.php?t=21421

You posted in that thread. :R

Anyways, about half the way down, a post by ssabripo (from Wiggins) talks about dual spiders.
Oh yeah, I remember that. :whew:

Well, even though I greatly respect Mr. Wiggins (and Hyre too), I have to say that the XBL^2 has been a slight letdown. So therefore I would take his "other" info with some reserve.
 

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Re: LMS-5400 / RL-p18" buy-in

Oh yeah, I remember that. :whew:

Well, even though I greatly respect Mr. Wiggins (and Hyre too), I have to say that the XBL^2 has been a slight letdown. So therefore I would take his "other" info with some reserve.
i wouldn't necessarily call it a "letdown" per se, but I hear ya.... In its defense though, I have to say the XBL^2 drivers I've played with (Avalanche, tumult) have had some of the cleanest, most accurate bass I've heard, including the older LMT15 (pre-cursor to the LMS 5400).

But yeah, some of the hoopla on the XBL^2 in that paper by Dan has been proven to not be exactly the case. :daydream:

ps- just to clarify, not all those comments are straight from Dan. Some of it came comments from Deon Bearden and Tom Nousaine
 

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Re: LMS-5400 / RL-p18" buy-in

i wouldn't necessarily call it a "letdown" per se, but I hear ya....
I started to feel a little bit bad about that sentence so I edited it.

In its defense though, I have to say the XBL^2 drivers I've played with (Avalanche, tumult) have had some of the cleanest, most accurate bass I've heard, including the older LMT15 (pre-cursor to the LMS 5400).
Exactly. And that leads us to the real million dollar question: Is slightly higher upper-end (say above 40-50 Hz) distortion actually preferred by many? Does it make the driver sound more accurate and punchy because there is more high frequency content in the mix? :hide:
 

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Re: LMS-5400 / RL-p18" buy-in

I have to say the XBL^2 drivers I've played with (Avalanche, tumult) have had some of the cleanest, most accurate bass I've heard
Is slightly higher upper-end (say above 40-50 Hz) distortion actually preferred by many? Does it make the driver sound more accurate and punchy because there is more high frequency content in the mix?
It would be nice to see an Avalanche 18 measured because some owners are saying there isn't enough punch in the higher frequencies. I have to think that be because it is clean near the top, and they want that synthetic punch. The Tumult that was measured IS a letdown to me - Dan could go on for pages about how everything he did was the right choice, but the measurements say something else. I dare say it measures poorly for the price - they were going for ~$600. I wouldn't be suprised to see the Avalanche at half the cost best the Tumult in just about every regard....except maybe for power hadling capability.
 

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Re: LMS-5400 / RL-p18" buy-in

"Send me one and I'll promise to measure it."

I'm all for that. The Avalanches are the most highly regarded unmeasured dwoofers I can think of.

I'll chip in $50 toward the shipping.
 

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Re: LMS-5400 / RL-p18" buy-in

It would be nice to see an Avalanche 18 measured because some owners are saying there isn't enough punch in the higher frequencies. I have to think that be because it is clean near the top
You reckon its significantly cleaner in the upper frequencies than the SDX?

I dunno...I'd actually say the those complaining of a lack of "punch" in the upper frequencies are merely complaining about the roll off in upper frequency output (not to say its extreme, but it is there). Rob has an AVA 15 and his RS390 has a definite advantage in the upper frequencies due in part to its lower inductance. He's already commented on gunshots sounding much better than ever before...no surprise there.
 

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Re: LMS-5400 / RL-p18" buy-in

Ilkka said:
You have three of them? Send me one and I'll promise to measure it.
If you were in the states I would probably be up for it, but I wouldn't want to take the risk of one getting damaged (or lost) sending it overseas - you can't really go out and buy a replacement.

noah said:
I'll chip in $50 toward the shipping.
You have four of them yourself if I'm not mistaken. I'll chip in if you want to send one of yours.

Willy said:
I dunno...I'd actually say the those complaining of a lack of "punch" in the upper frequencies are merely complaining about the roll off in upper frequency output (not to say its extreme, but it is there).
It would show up in their FR then. But that brings up a good point because it reminds me that the two owners complaining of lack of punch have pretty terrible in room FRs. Sometimes the culprit is the most obvious culprit.

As for high end rolloff on the Avalanche 18, there is some, but it shouldn't cause any dips in response as long as you don't use a crossover higher than 80hz. I've never had any problem keeping that range nice and flat in my setup at my old place or new one. Attached are some close mic FRs I took of the ported Avalanche 18 using an 80hz and 200hz crossover with all speakers off.
 

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Re: LMS-5400 / RL-p18" buy-in

It would show up in their FR then.
Oh but it does show up in a measurement. Here are two near field measurements. One of an AVA15 and the other of the 390. The difference is obvious.





As for high end rolloff on the Avalanche 18, there is some, but it shouldn't cause any dips in response as long as you don't use a crossover higher than 80hz
I won't talk about dips, but since the crossover to the sub isn't a brickwall, the linearity of the driver beyond the xover point is indeed relevent. So it only makes sense that a more linear driver in the upper frequencies would sound punchier than one that rolls off the high end to a degree.

Now yeah, the rolloff in the last graph you posted is certainly not bad. Only ~4dB down at 100Hz, right? Still there though...so I guess all I am saying is...blaming others thoughts about the Ava's lack of punch on their penchant for higher distortion may not be entirely correct. It could be...but I think the ava's roll off also may be a good portion of it. We've yet to be given a reason to think the Ava has abnormally good upper frequency response.

If you were in the states I would probably be up for it, but I wouldn't want to take the risk of one getting damaged (or lost) sending it overseas - you can't really go out and buy a replacement.
Hey, what about a Klippel? I am pretty sure npdang (he's in CA) would test an Ava 18 for free. That'd be much cheaper, easier, and safer than sending one overseas. Quite informative too!
 

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Re: LMS-5400 / RL-p18" buy-in

Willy said:
Oh but it does show up in a measurement
That's only the sub. If there were a lack of punch due to a dip in FR in the upper bass range caused by the rolloff of the sub above the crossover frequency as you mentioned in your previous post, you'd need to measure up to ~200hz with the mains in play to see it. Seeing as most processors use a 4th order crossover slope, that would put the sub 24db down by 160hz. A couple db difference in output form the sub that high shouldn't really matter, especially when you consider that room effects play a huge role in that range.

Now that said, again, I have't observed such dropoff in upper bass myself, and I know my VR3s don't have humped bass above 100hz which could be making up for it. My response up to 200hz was extremely flat in the old place - haven't measured it at this new place.

Also, I'm not necessarily "blaming" others' perceived lack of punch on low distortion, as I just remembered after your post that they both have pretty bad in room FRs.
 

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Re: LMS-5400 / RL-p18" buy-in

That's only the sub. If there were a lack of punch due to a dip in FR in the upper bass range caused by the rolloff of the sub above the crossover frequency as you mentioned in your previous post, you'd need to measure up to ~200hz with the mains in play to see it.
Yeah, I understand what you're saying.

But the fact that those measurements I linked to are only of the sub driver doesn't negate them, if anything they are more useful. Their deficiencies can't be masked. If a roll off exists, it will show up.

Also, I'm not necessarily "blaming" others' perceived lack of punch on low distortion
Well, you kind of hinted at it with this:

"It would be nice to see an Avalanche 18 measured because some owners are saying there isn't enough punch in the higher frequencies. I have to think that be because it is clean near the top, and they want that synthetic punch."

You say it is clean near the top but how clean, relative to what, and where is the evidence?

Seeing as most processors use a 4th order crossover slope, that would put the sub 24db down by 160hz. A couple db difference in output form the sub that high shouldn't really matter, especially when you consider that room effects play a huge role in that range.
Now that said, again, I have't observed such dropoff in upper bass myself, and I know my VR3s don't have humped bass above 100hz which could be making up for it. My response up to 200hz was extremely flat in the old place - haven't measured it at this new place.
But you do use a 60Hz xover, so it'd only make sense that you shouldn't suffer from such problem. Have a FR of just your VR3s? Boundary gain could definitely increase their response around 100Hz.

Just things to think about.
 
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