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Re: LLT Explained

Steve, I'm still trying to understand your "amp-limited" concept as you conceive it. How are you determining amp size for a particular application to make it properly amp limited?
As Willd touched upon, I don't want to feed it so much power that it can exceed the driver's xmax capabilities above tuning.....in the tuning range of LLTs, max excursion use should peak ~20hz. Now, if you ever drive the amp to the point of clipping, you know two things. First, turn it down a bit, and second, if you see clipping occur on a more than rare occassion, your listening habbits demand more subwoofage.

Hmm, it clearly states "peak" right on the input screen. In addition, it appears to use that number as though it was p-to-p when calculating the VD
Vd should be peak to peak, but for the sake of modeling something like an amp limited design, one is only interested in the one way safe travel limits.

I do happen to think that the LMS-5400 and possibly the upcoming 4100 are better suited to passive radiator subs because they seem to like smaller enclosures which would problematic to port properly. They don't need 19ft^3 to work well, you know? And in a smaller enclosure, they can handle more power (like a full 3200W).
You'd be giving up low end sensitivity for high end sensitivity and running more power through the coil, in which case you may as well just go sealed with a LT. The goal should be as much output as possible with as little power as needed in my opinion, but to each his own. The 4000 practically demands a large enclosure - I don't know what the deal with the 4100 is, but I thought it was just a 4000 with a more efficient motor due to a different magnet :dontknow:

As for port issues, were I using a LMS 5400 18", I'd probably go 480 effective liters with a 7" diameter port that is 32" long and flared and feed it with 1800 watts. Good luck trying to find a 7" diameter cylinder, but if you can, air velocity is fine as long as you aren't constantly pushing the full 1800 watts with low teen material, conservatively getting ~117db levels. If you are, you shouldn't be trying to do it in a single driver sub anyway.

I wouldn't recommend making the first resonance much lower than 190hz....at some point it's gonna become audible. Assuming an 80hz, 4th order crossover, having it much lower than 190hz might be getting too close to the edge. Remember, the LLT is supposed to be as much of a no performance compromise design as possible - that means in all regards. If you wanna judge a guy based on what he does with his own stuff, my first port resoannce models to be ~270hz, so..... :nerd:
 
Re: LLT Explained

I don't know what the deal with the 4100 is, but I thought it was just a 4000 with a more efficient motor due to a different magnet
No, thats only where the differences begin. Not only will it be far more efficient (close to or better than the TC-2000) but have more Bl, much more excursion (38mm 100% linear compared to the 4000s 30mm) with a mechanical excursion of close to/around 50mm one-way.

It'll have a tall-roll surround, a titanium cone instead of an aluminum cone, higher power handling...basically, it is far better than the 4000.

Also, it'll have a much lower Q, therefore it won't need ridiculously large boxes like the 4000 does. I suspect it won't need more than 10ft^3 for a good LLT design, but we'll see.
 
Re: LLT Explained

A high Bl and a low Qts typically makes it hard to have a smooth tie of port ouput with driver rolloff. Such cases result in a resurgence of output near tuning, or an underdamped port region. The RLp15 is ALMOST guilty of this. Here's a link talking about Bl - ported alignments get mentioned in the 9th paragraph. Such qualities - high Bl and low Qts - typically work better in smaller enclosures, which makes it more suited for sealed. But who knows how much the parameters will be shifted.
 
Re: LLT Explained

I believe Willy was mentioning the LMS 4100 to have a significant improvement in Bl in comparison to the LMS 4000 which has an advertised Bl of just 11T*m. I don't think its fair to assume it'll suffer from issues with port/driver output roll off because it'll have a "higher" bl than that of the LMS 4000. For all we know, the final product may have a lower/similar bl to an Rl-p 15 which has already been proven to give pretty flat in-room response regardless of what simulations have shown about port output and driver roll-off.

Its fair to say the Rl-p 15 IS guilty of the phenomenon you mention Steve.The LMS-4100, if it measures closer to a TC-2000 in the Qts/Bl/ Vas will probably not suffer from this Fr linearity issues to a point where anyone would have to worry about it, especially since the Rl-p 15 LLT in-room measurements I've seen do not look like the simulations.

It would be very interesting to see a test rounding up a few drivers with certain power handling capabilities and see how the effect of VC heating effects the THD among these drivers. An educated guess would be to assume that Driver A with its higher power handling capabilities will probably be more resistant to VC heating side effects in comparison to Driver B with a lower thermal power handling capability.
 
Re: LLT Explained

For all we know, the final product may have a lower/similar bl to an Rl-p 15 which has already been proven to give pretty flat in-room response regardless of what simulations have shown about port output and driver roll-off.
Its fair to say the Rl-p 15 IS guilty of the phenomenon you mention Steve
The RLp15 LLT design doesn't suffer from this because I accounted for it in the design. 260 effective liters with a ~15hz tune minimizes the discrepancy in the tie in of port output to driver rolloff enough that it isn't a significant issue.

especially since the Rl-p 15 LLT in-room measurements I've seen do not look like the simulations
That's because an it's an in room measurement :bigsmile: room gain and/or reflections easily mask any small FR changes. To match the simulations, you'd want to do a ground plane measurement.....since that's not very easy, close mic measurements of the drivers and port with no crossovers in play is the next best option. Ryan happend to do something close to that, except he left the 100hz crossover in play.



You take out the crossover and the upper frequency bass will be even higher in magnitude. In the case of Ryan's specific design, max output should be somewhere in the neighborhood of 110hz. You combine the close mic driver response with the port output and you have a response that looks VERY similar to the simulation. All said and done, the simulations are very accurate. A ported sub response is no more difficult or no less accurate to predict than a sealed sub with an EQ boost (the EQ boost is replaced by port output).

Aside from the issues a resurgence in port output will create if left unattended to, the bigger problem is that such drivers that are prone to that want smaller enclosures to get away with lower tunes. This goes against being able to create an affective LLT, and this is why the RLp15 is ALMOST not a good choice. Much smaller than 260 effective liters and you'd fall into port troubles as well as reduce low end efficiency to the point that in room response probably wouldn't be as flat as it is.
 
Re: LLT Explained

An educated guess would be to assume that Driver A with its higher power handling capabilities will probably be more resistant to VC heating side effects in comparison to Driver B with a lower thermal power handling capability.
Absolutely. The LMS drivers have HUGE coils with lots of turns of copper, so they can handle a lot of power and will be more resistant to THD created by vc heat than a driver with a small coil like one using xbl^2. That said, less power is still always going to be better than more power. Aside from the direct THD issues, one also has to wonder if high power handling in small sealed enclsoures could heat the internal enclosure air enough to expand the air, increasing the internal spring force, decreasing low end efficiency.
 
Re: LLT Explained

I am sorry, but are you saying xmax is an informal standard but Vd is set in stone as peak to peak displacement?

Thats a bit odd, don't you think?
Yes, it is. I suppose Vd might not be set in stone, but I do believe it's typically calc'd using peak-to-peak excursion. In any case, I suppose we could check with LinearTeam to see which way they intended the Xmax to be entered. A definitive answer on this would be nice.

Xmax is almost always given as the one-way linear excursion. I can't think of many examples where it isn't. Its not our fault that in WinISD, the formula used to calculate Vd is simply xmax x Sd, when usually it is 2 * xmax * Sd. I don't know why you think you need to put in the peak-to-peak xmax simply because of this.

"Having the right Vd value for your model" is completely irrelevant. That value it gives you for Vd is not used in the actual simulation. You only need to pay attention to what the simulation gives you (i.e SPL)
Absolutely. I was only using Vd as a means to understand how to enter the Xmax.

And you're correct about the resonance, 156Hz shouldn't be much of an issue. Do you actually have any intentions of building an 5400 LLT? That would be interesting..to say the least.
Yes it would. I don't know that I'll do it using the LMS driver just yet, but I'll probably put an LLT together using either a 12" or 15" TC-2000 to evaluate it vs my sealed subs. I'm leaning toward using Sonotube in this effort, even though I've never built a sonosub before. The larger enclosures required for LLTs would make MDF enclosures extremely heavy and difficult to work with. So, for those of you who have built sonotube enclosures and don't mind offering up some of your wisdom on what works and what doesn't, I'd be interested in hearing it. Stuff like how to make an endcap. A Jasper Jig will cut a disk about 18" in diameter, but not 24" or 30". How is it normally done? I suppose I could rig something to use as a pivot for a router...
 
Re: LLT Explained

Well, I built an LLT using the 15" TC-2000 and have been very pleased with it so far.

Yeah, a 12-13ft^3 MDF enclosure would be pretty heavy, which is one of the main reasons I chose to go the sonotube route.

Most folks make their own jig to cut the big diameters, but there is a jasper jig available that is capapble of much larger diameters. http://www.rockler.com/product.cfm?page=5960
 
Re: LLT Explained

The RLp15 LLT design doesn't suffer from this because I accounted for it in the design. 260 effective liters with a ~15hz tune minimizes the discrepancy in the tie in of port output to driver rolloff enough that it isn't a significant issue.
Right, it isn't a significant issue...thats exactly right. If the issue can be resolved with proper volume and tuning frequency, then its totally possible to take the same precautions with another driver that may also suffer from the effects of high Bl and low Qts in this alignment obviously. But keep in mind, we were talking about the driver itself and how it effects the entire allignment...not one of your designs.


That's because an it's an in room measurement :bigsmile: room gain and/or reflections easily mask any small FR changes.
That pretty much goes without saying...and I never said in-room measurements should or normally do look like simulations. This was said only in reference to a comment you made about port output and driver rolloff... at this point its a non-issue even with drivers with high bl and low Qts because we account for them in the design phases, except for those extreme situations...like a Tc-5200 for example.

To match the simulations, you'd want to do a ground plane measurement.....since that's not very easy, close mic measurements of the drivers and port with no crossovers in play is the next best option. Ryan happend to do something close to that, except he left the 100hz crossover in play.



You take out the crossover and the upper frequency bass will be even higher in magnitude. In the case of Ryan's specific design, max output should be somewhere in the neighborhood of 110hz. You combine the close mic driver response with the port output and you have a response that looks VERY similar to the simulation. All said and done, the simulations are very accurate. A ported sub response is no more difficult or no less accurate to predict than a sealed sub with an EQ boost (the EQ boost is replaced by port output).
The above also goes without saying, and is certainly good information for people to know :T

Aside from the issues a resurgence in port output will create if left unattended to, the bigger problem is that such drivers that are prone to that want smaller enclosures to get away with lower tunes. This goes against being able to create an affective LLT, and this is why the RLp15 is ALMOST not a good choice. Much smaller than 260 effective liters and you'd fall into port troubles as well as reduce low end efficiency to the point that in room response probably wouldn't be as flat as it is.
Whether or not the Rl-p 15 is or isn't a good choice for an LLT alignment was never questioned..............not by me or anyone else in this thread IIRC. There are many other great things about the driver that make it suitable for this use but having a relatively high bl and low qts isn't its strong point for reasons already discussed here.

Will, **** thats huge :raped:
 
Re: LLT Explained

This was said only in reference to a comment you made about port output and driver rolloff... at this point its a non-issue even with drivers with high bl and low Qts because we account for them in the design phases, except for those extreme situations...like a Tc-5200 for example.
How many other high Bl and low Qts drivers have been used in LLT designs? :scratch: The problem is as I mentioned, to resolve the issue of a resurgence in port output one must use a smaller enclosure with a lower tune, and this gets away from a successful LLT design. Try making a LLT with a RLp12 D2 - just ain't gonna happen. The RLp15 just makes it. The reason I keep saying that is to make the point that high Bl and low Qts work against a LLT design.
 
Re: LLT Explained

:dunno: Couldn't answer that as I'm nowhere near qualified to answer that. I haven't kept track of every LLT design built :) Plus, Its totally irrelevant to my entire post, even the section you're quoting. :rolleyesno:

The problem is as I mentioned, to resolve the issue of a resurgence in port output one must use a smaller enclosure with a lower tune, and this gets away from a successful LLT design.
Correct, but...now where did I say this wasn't the problem? An Rl-p 12d2 LLT just would not happen for the same reasons (although not to the same degree) an LMS-5200 LLT would not work. Your observation (and pretty much common knowledge for people that can read/understand programs like Unibox or WinISD etc) regarding Low Qts/High Bl drivers and the methods of overcoming those two factors hasn't been challenged in this entire thread and SHOULD be noted. We're agreeing with each other, Gosh! :T

So I hope that at this point everyone understands why low Qts/high Bl aren't something to look for to use in an Xl-sized Ebs alignment...its been repeated enough times in this thread :bigsmile:

Now, Someone build me a large and low tuned Sono for my 1030ft^3 bedroom! :neener:
 
Re: LLT Explained

Well, I built an LLT using the 15" TC-2000 and have been very pleased with it so far.

Yeah, a 12-13ft^3 MDF enclosure would be pretty **** heavy, which is one of the main reasons I chose to go the sonotube route.

Most folks make their own jig to cut the big diameters, but there is a jasper jig available that is capapble of much larger diameters. http://www.rockler.com/product.cfm?page=5960
I wasn't aware Jasper made a larger jig. Thanks for the pointer, Willy.

BTW, what are the particulars on your TC-2000 LLT? I was looking at using the TC2K 15" SVC, going about 13 cu ft with a 13hz tune and three 4" ports.
 
Re: LLT Explained

Plus, Its totally irrelevant to my entire post, even the section you're quoting
Your observation (and pretty much common knowledge for people that can read/understand programs like Unibox or WinISD etc) regarding Low Qts/High Bl drivers and the methods of overcoming those two factors hasn't been challenged in this entire thread and SHOULD be noted. We're agreeing with each other, Gosh!
I guess the part I am misunderstanding or getting hung up on is this:

at this point its a non-issue even with drivers with high bl and low Qts because we account for them in the design phases
It's only really been accounted for with a design for one driver, and it just gets by. In fact, the main reason it had to even get by was because there was no other quality 15" driver available at a reasonable price from a reputable dealer from about Sept. '05 to something like early summer '06. Ideally, such things shouldn't have to be worried about or dealt with (ideally :R ). If some wanted a good LMS driver to use for a LLT, the 4000 would be it aside from its poor sensitivity, so it would be nice if the 4100 was similar with just a more efficient or sensitive motor.
 
Re: LLT Explained

Ahh, yeah I understand that completely. That was the time when I first started getting into DIY subs...unfortunately.

Anyway, I hope the 4100neo proves to be a good LLT contender. It'll be good to have yet another option out there...especially after that dry spell you mention. Its slowly beginning to look better for DIY again. From what I've heard it'll model very similarly to the LMS-5400 which will be a good thing.

Can't wait for that rl-p18 either. Its going to be ridiculous.
 
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