LLT Explained - Discussion Thread - Page 17 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #161 of 191 Old 12-09-09, 01:58 PM
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Re: LLT Explained - Discussion Thread

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Your not planning on using your IB drivers in an LLT box sub are you?
Other than "wasting" of good x-max specs at the tuning freq what would be the problem in that? Above tuning it should act as an IB.

To answer your question, my LLT plans are on hold now that REW has vastly improved my IB experience.
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post #162 of 191 Old 12-09-09, 02:08 PM
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Re: LLT Explained - Discussion Thread

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obijon wrote: View Post
Other than "wasting" of good x-max specs at the tuning freq what would be the problem in that? Above tuning it should act as an IB.

To answer your question, my LLT plans are on hold now that REW has vastly improved my IB experience.
I'm glad to hear you are happy now. The thought of giving up on an IB build just broke my heart.
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post #163 of 191 Old 12-09-09, 02:15 PM
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Re: LLT Explained - Discussion Thread

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zation cosign wrote: View Post
Hello, First Post here.

Been agonizing over the sealed vented thing for a long time.
All my reading on it would seem to suggest that the most important consideration is how subs will be generally be used.
The type of sub you build should depend on your driver first. Then your size concerns. If your driver can be ported and you can build it ported properly you will usually have a much better sub. That being said many subs are just fine sealed. Why not try building it sealed and seeing if you like it?

Wood is pretty cheap relatively speaking so you really don't have a lot to lose. Get in the shop and try this out. Make sure to post a build thread for us.
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post #164 of 191 Old 12-09-09, 02:24 PM
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Re: LLT Explained - Discussion Thread

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obijon wrote: View Post
Other than "wasting" of good x-max specs at the tuning freq what would be the problem in that? Above tuning it should act as an IB.

To answer your question, my LLT plans are on hold now that REW has vastly improved my IB experience.
The VAS of true IB driver is much higher than that of normal drivers, meaning they are much stiffer. They are designed to work in huge cabinets (typically a room) and from that they essentially move in free air. When you put it in a smaller cab the chances are they will loose a lot of performance because the cabinet is simply too small for their designed application.
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post #165 of 191 Old 12-09-09, 02:56 PM
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Re: LLT Explained - Discussion Thread

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Moonfly wrote: View Post
The VAS of true IB driver is much higher than that of normal drivers, meaning they are much stiffer. They are designed to work in huge cabinets (typically a room) and from that they essentially move in free air. When you put it in a smaller cab the chances are they will loose a lot of performance because the cabinet is simply too small for their designed application.
Good point, but I'm already using the attic as a box so building a large box is not out of the question for me. The calculated box volume for my 2 Tempest-X drivers is 35 cu. ft. with a 15hz F3, which is no small animal, but we are talking LLT after all.
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post #166 of 191 Old 12-09-09, 03:22 PM
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Re: LLT Explained - Discussion Thread

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Good point, but I'm already using the attic as a box so building a large box is not out of the question for me. The calculated box volume for my 2 Tempest-X drivers is 35 cu. ft. with a 15hz F3, which is no small animal, but we are talking LLT after all.
I like your attitude

Ib's are stiff with low xmax because they have to start and stop themselves and move in free air. If you put it in a smaller sealed box the driver is going to struggle moving at all which is were you will loose all your performance. You could get it to move with masses of power but then the VC will probably self destruct with melt down. Putting it a very large ported box is probably the only way you possibly could use an IB driver in a normal sub.

If you give it a go then fair play to you , and whatever lesson you learn make sure you let us all in on it . Thinking out loud, I think very large ports are a must to minimise resistance on the driver. Resistance would be your biggest enemy I think, and bearing in mind your attic is extremely leaky in comparison to most sealed subs.
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post #167 of 191 Old 12-09-09, 08:16 PM
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Re: LLT Explained - Discussion Thread

A few observations...

Quote:
Moonfly wrote:
The BK Monolith is an example of a very fine LLT sub using the Peerless XLS drivers
No, the BK Monolith definitely is NOT an example of a LLT, let alone a good one - it barely meets any of the LLT criteria. Please read the LLT Explained thread so you will know what a LLT actually is.

Quote:
All a port does is tune a sub lower, to increase output of lower frequencies
A sealed sub isn't "tuned" to begin with. Proper porting allows you to gain up to ~6db of clean headroom at tuning frequency - the output then tapers off above and below that - it doesn't have to be at low frequencies. For a LLT however, there are specific characteristics that must be met.

Quote:
The VAS of true IB driver is much higher than that of normal drivers, meaning they are much stiffer
Higher VAS means a looser suspension, not stiffer. IB drivers don't work well in small sealed enclosures because they have small motor structures and they can't generate a lot of force, so they can't oversome the air spring of the small enclosure - the problem is not the driver's suspension. An IB driver should work fine in a LLT designed to match the driver.

Quote:
Thinking out loud, I think very large ports are a must to minimise resistance on the driver
How does a port minimize resistance on a driver? The port does not "leak" pressure above tuning frequency - above tuning, there really isn't much pressure buildup in the enclosure at all. That's due to the size of the enclosure, not because it's ported.





Quote:
zation cosign wrote:
Is this design suitable for the use I described? Are those Peerless woofers suitable for LLT?
No, unfortunately those drivers aren't really suitable. You need enough air moving capability to get away with a tune <=15hz at at least moderate listening levels without running out of excursion. Only high excursion 15" and larger drivers are really suitable for a LLT. You'll also want more power than 100 watts, otherwise you won't be able to put the excursion to use.

Your best bet for those drivers is to go sealed. Make it just large enough so that the knee is ~30hz if possible and so you can't reach overexcursion below ~25hz even at full power. Most music doesn't contain much bass below 30hz.


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post #168 of 191 Old 12-09-09, 09:27 PM
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Re: LLT Explained - Discussion Thread

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Moonfly wrote: View Post
Not much music goes lower than 40 hz, so that is no major concern.
Umm, check this


This isn't even counting the alternate lower tunings most Rock bands use these days, pipe organs/synthesizers which can run down to 16Hz, electronic bass which is unfortunately in the single digits these days, or the natural instrument sympathetic reverberations into the teens.

Quote:
Moonfly wrote: View Post
The VAS of true IB driver is much higher than that of normal drivers, meaning they are much stiffer. They are designed to work in huge cabinets (typically a room) and from that they essentially move in free air. When you put it in a smaller cab the chances are they will loose a lot of performance because the cabinet is simply too small for their designed application.
Quote:
Moonfly wrote:
Ib's are stiff with low xmax because they have to start and stop themselves and move in free air.
"Punch" is a function of SPL. If you want punch on a flat system turn it up. If you want "Punch" at lower listening levels add EQ. Most people complaining about "punch" are use to exaggerated bass response. Either add it in with EQ, or build a peaking enclosure and do it that way. This is why people think a small sealed sub is the only way to get "Punch." They are just altering the enclosure FR, and don't get it.

If you want "Punch" with an IB or LLT just add some boost between 60-120Hz. Done.

EDIT: Sorry mixed two treads together.
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post #169 of 191 Old 12-10-09, 02:53 PM
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Re: LLT Explained - Discussion Thread

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SteveCallas wrote: View Post
A few observations...


No, the BK Monolith definitely is NOT an example of a LLT, let alone a good one - it barely meets any of the LLT criteria. Please read the LLT Explained thread so you will know what a LLT actually is.
Hi Steve. I'll try clear it up here. Technically the Monolith isnt really a proper LLT. In the UK where I am based the Monolith is considered large (too large for many), and it is tuned low. It is in that sense I meant the Monolith is an LLT, and I was simply trying to convey the XXLS driver could be used in such applications.

I use this for sub type references:
http://www.danmarx.org/audioinnovation/theories.html

Quote:
A sealed sub isn't "tuned" to begin with. Proper porting allows you to gain up to ~6db of clean headroom at tuning frequency - the output then tapers off above and below that - it doesn't have to be at low frequencies. For a LLT however, there are specific characteristics that must be met.
Agreed. I did not mean to suggest a sealed sub it tuned, only that a ported one is by use of the port. Generally ports are used to improve the more difficult to produce low end performance, and while that doesn't have to be their only area of tune, in a sub it usually is.



Quote:
Higher VAS means a looser suspension, not stiffer. IB drivers don't work well in small sealed enclosures because they have small motor structures and they can't generate a lot of force, so they can't oversome the air spring of the small enclosure - the problem is not the driver's suspension. An IB driver should work fine in a LLT designed to match the driver.
I dropped the ball there, . Your right and I stand corrected (it was late here ). I was actually thinking about driver excursion more than driver stiffness. Sorry peeps.


Quote:
How does a port minimize resistance on a driver? The port does not "leak" pressure above tuning frequency - above tuning, there really isn't much pressure buildup in the enclosure at all. That's due to the size of the enclosure, not because it's ported.
My point, which I didnt explain to well, was that a small sealed enclosure with its air spring effect, will reduce what little excursion you do get from IB's, thus reducing its performance. By putting it in a [large] ported enclosure, you will reduce this limiting effect. Would you agree?


Quote:
soho54 wrote: View Post
Umm, check this


This isn't even counting the alternate lower tunings most Rock bands use these days, pipe organs/synthesizers which can run down to 16Hz, electronic bass which is unfortunately in the single digits these days, or the natural instrument sympathetic reverberations into the teens.
I know there is music that does extend below 40hz, but even that chart shows the vast majority is above, thats all I was saying. As such, it is my view that any decent sub will be fine with music, and one that can hit 100db at 10hz really isnt a must for music at all. Any decent well designed sub should be fairly competent down to 20hz, and 30 at the very least, meaning for music its it perfectly fine IMHO.


Quote:
"Punch" is a function of SPL. If you want punch on a flat system turn it up. If you want "Punch" at lower listening levels add EQ. Most people complaining about "punch" are use to exaggerated bass response. Either add it in with EQ, or build a peaking enclosure and do it that way. This is why people think a small sealed sub is the only way to get "Punch." They are just altering the enclosure FR, and don't get it.

If you want "Punch" with an IB or LLT just add some boost between 60-120Hz. Done.

EDIT: Sorry mixed two treads together.
I think we are talking from two different viewpoints on this one. For example I compared 2 subs sides by side in my room, a PB13U and 2 M&K MX125's. Both where EQ'd to give a similarly flat response and both gave good output down to 10hz in my room, and both waterfalls were of similar performance as well. From that technical stand point the punch should have been the same, but it wasnt.

While the MK's didnt sound as deep for obvious reasons, I much preferred the sound quality of the MK's and they had much more upper sub bass punch in my view. Whilst both subs showed to be similar on paper, their sound (and punch qualities) were completely different.




Hope that helps clear things up from my perspective for people. Sorry if I goofed anywhere

There is one other point with smaller sealed subs. They might be distorting more, and its this audible distortion some detect as better more punchy bass.
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post #170 of 191 Old 12-10-09, 02:58 PM
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Re: LLT Explained - Discussion Thread

Moonfly you didn't goof. You are correct in your assessments. I know of no driver that shows low enough distortion at 10hz to even be useful. Engineering has it's limits and most music doesn't use the lowest notes anyway.
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