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Why not LLT?

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19K views 106 replies 13 participants last post by  1Michael 
#1 ·
I'm getting ready to break earth on an LLT project (2 340liter working-volume boxes each holding one Dayton 15" MkIII, 15Hz target tune). But I haven't made any sawdust yet, so there's still time to change course. To all the LLT nay-sayers, please speak your peace :rant: (or point me to a thread where you've already done so). I'll start skimming the LLT discussion thread in parallel. I already plan to use an HPF (Reckhorn B-2?), so I'm open to arguments in favor of up'ing my tune frequency. I only care about sound quantity&quality. The size of LLT enclosures are not a problem (besides getting two of these beasts up my stairs), but still, smaller would be slightly better.

Thanks,
--Myles
 
#3 ·
I'm not an LLT naysayer, but I recently went from a dual sealed setup (where i had flat in-room response to about 12hz) to a passive radiator system (cut holes in my boxes and installed the PRs). The boxes are tuned to 22hz and I am considerably happier since i have far more output in the regions where i can actually hear it. All the test tones and sweeps i ran prior showed i could not hear anything under 20hz despite a small sealed room and very powerful subs. All i saw was cones going crazy with movement - if not for that I'd never know a 15hz tone was playing at 100+db
 
#4 ·
LLTs sacrifice headroom for unnecessary extension is the strongest argument against an LLT. Headroom vs extension is always the battle with subs.

another argument against it might be that LLTs produce sound not mastered into the track, but any big truck or subway driving by the studio. Since sub 20hz is nearly impossible to stop.

Another argument against it might be that your neighbors will egg your house more and the Police will visit more due to the constant shaking, but that risk happens with any decent sub.

I would not build an LLT because I see the extra size and extension as unnecessary. But subwoofer design is largely personal preference or spouse restricted:T.
 
#6 ·
The problem with LLTs for me is the cabinets are just too large for the drivers. The result is a sound that is devoid of life. An LLT is merely about the most performance from a single driver, and nothing else. They completely ignore sound quality preference in the search for max spl. Super deep and super clean low output is all fine, but its like buying a car based on how fast it will go, just because its fast doesnt automatically mean you will enjoy the ride.

If max spl per $ is your primary concern, then an LLT is everything you could hope for. For me, I'd rather pay more, and get the performance from a sub I actually really like the sound of. This isnt to say LLTs will sound bad, because they wont, but for me they just dont deliver that smile you get from a sound quality you really love. Even an EBS is a bit devoid of character IMO. I would only go the route of an LLT if I had some very capable and probably very large main speakers that only need the lowest octaves taking care of.

LLT naysayer? You mean a misinformed dullard? :devil:
Its a funny thing, I feel the same way about those who cant see past an spl graph :D
 
#8 ·
An LLT is merely about the most performance from a single driver, and nothing else. They completely ignore sound quality preference in the search for max spl.
I agree with the first statement, but the second one invites subjectivity into the equation. To say a LLT 'ignores' sound quality would infer that the design tries not to achieve optimal performance. If one wants clean, accurate bass reproduction, then they want a linear FR, minimal distortion, and high output capability. If one wants some variation upon bass sounds - which is fine - then they want some deviation from those primary performance characteristics.
 
#10 ·
Oh they dont ignore sound quality, as you say they are about clean output. My point is they have a preference of max spl over designed sound quality taste. One problem for me is that they are just too clean, and focused on being too low. This tends to lead to a lack of upper bass sound in the material they produce, hence the lack of character, because that is derived from the bass you can hear.

Low clean output is perfectly achievable from even a sealed design, it just costs more money, but you get what you pay for IMHO. Ive yet to hear any ported designed sound as good to my ears as a high performance sealed. You can argue all day that a ported design gives more output per watt/driver, and thats not disputable, but there is more to bass that simply getting the most spl from your driver. Sure you will get a linear response and sure your LLT will go very low, but from only having say a single driver, its at the cost of upper bass punch (unless you get this from your speakers, in which case an LLT is probably the more suited design) similar to a sealed sub with an incredibly low Q sound.

IB's suffered from this at first, before specific IB drivers existed. When you put a driver in a massively oversized cabinet, you rob it of its character and punch. IB drivers have a specifically designed response to counter this.

LLTs are good at what they do, but you just need to ensure that what they do is exactly what your looking for. For me, its not, they represent a cost cutting short cut to more spl at the expense of some of the stuff I like, and to be honest, wont be without.

Personally, if I was going to build say a couple 350 litre subs, rather than put in a 15" driver and tune to 15hz, I would rather use say a 21" driver (smaller cab comparatively), and you will get the same performance, but with a different sound character, but again it costs more money.
 
#9 ·
Just got back in town. Stuck at the inlaws in BFE Texas (Childress to be precise) with zero internet access (you read that right, not even Edge/3G on the iPad). Too late-night for a detailed reply. I'll type more tomorrow night. But quickly:

1. Thank you for rehashing what I'm sure can be found in 27 other threads in these forums.
2. Big really isn't a problem. In fact, I'm kind of looking forward to the visual shock and awe that a couple of 370liter working-volume monsters will inspire :dumbcrazy:. I'm blessed with my own do-as-I-please HT room (14x11x8ft). Gotta love $120/sq-ft housing in Austin. And that's the upper-middle-class neighborhood price. You can easily get $90/sq-ft in sketchier neighborhoods.
3. I'm going to target a 17Hz tune, but I'm chickening out and adding the ability to replace the port with another of different length (or seal altogether if the whim hits me, but doubt it ever will).

Thank you thank you thank you!! :T
--Myles
 
#11 ·
Do as you please = 4 corner loaded subs for me. If you want to do tapped horns there are some very nice options. For ported I'd use the Dayton Reference 15" drivers. Low cost and with 4 of them loading the corners you will get plenty of bass with a very even in room response.

If money grows on trees grab some LMS Ultras or Maelstrom 21" drivers.

Austin isn't too shabby with its 30 dollar movie theaters and high class toll roads. A Juan in a million burrito sounds very good at the moment.
 
#12 ·
If you want a good argument against LLT but don't care about cabinet size, I can't help you, I'm stuck. I may add that LLT's like power but it doesn't sound like $$ is a big issue for you so an EP4000 or two shouldn't be a deal breaker.

My first system had a large sealed Velodyne sub. Sounded good - great in fact, at first. Then I got tired of the "boominess" of it. Good "punch" but not low.

Second system had two MFW-15s in it. REALLY good subs - for the money and for commercial subs. Good "punch" and much better lows.

Current system has two LLTs (15" TC-2000s) in it. Different planet. Punch is equal to the MFWs and the Velodynes but extension was crazy. Felt things in movies unheard of prior to. Not trucks running by the mixing studio either. Movement. Ease.

Good luck.
 
#13 ·
Thanks Phil! That's just what I was looking for. Someone with listening experience. My personal experience is limited to my 10" REL sealed "audiophile" sub, and my current MkIII sealed kit box (which I'm actually pretty happy with except that it feels "stressed" during monstrous cinematic bass passages).

I re-read StevieC's LLT article again so I think I'm going to lower my tune back to 15Hz. Grrrr... Can't stop vacillating. Bad news is that it's raining all week in Austin, so I can't get any MDF from HD to my home. Another week to bounce back and forth.

I'm definitely going to build in a port replacement capability, so maybe I'll play around with different tunes eventually (and sealed).

Reading Lateral's thread (http://www.hometheatershack.com/for...ojects/36751-sonosub-mal-x-21-1200l-14hz.html) has me scared of super-sub-sonic content, so despite Steve's argument that an HPF isn't necessary, I want to employ a Reckhorn B-2 @ ~14Hz (4th order). What do you guys think? I don't ever want to hear my VC crashing against the magnet. Will it introduce noticeable group delay. I just tested with WinISD and I see that it adds 20ms @ 20Hz (from 15ms to 35ms). Ugh... Will this sloppify my bass experience? Or will it not matter for blowing $%*# up?
 
#14 ·
Felt things in movies unheard of prior to. Not trucks running by the mixing studio either.
:D

so despite Steve's argument that an HPF isn't necessary, I want to employ a Reckhorn B-2 @ ~14Hz (4th order). What do you guys think? I don't ever want to hear my VC crashing against the magnet. Will it introduce noticeable group delay. I just tested with WinISD and I see that it adds 20ms @ 20Hz (from 15ms to 35ms). Ugh... Will this sloppify my bass experience? Or will it not matter for blowing $%*# up?
If you are convinced you want to use a highpass, at the very least, please don't use it that close to the tuning frequency (14hz highpass with a 15hz tune). I'd look at centering it closer to 10-11hz so you don't rob a lot of the benefit of the porting.
 
#15 ·
I dinked around with the cutoff freq until cone excursion dropped out of the stratosphere. However, recalling from your LLT-explained article, Xmech ~ 1.5*Xmax. So my MkIII will probably be able to sweep ~30mm before crashing the pole piece (or stressing the surround/spider). Using that assumption, I am able to drop the cutoff to 12Hz (32mm excursion @ 12Hz; 700W input). With cutoff of 11Hz, I'm seeing 38mm excursion @ 12Hz. That cuts my group delay by 3ms FWIW, and of course gives me a little deeper response.

I hate that I even have to worry about this deep sub-sonic content. One would think the sound designers would digitally hack this stuff out before it hits the sound track on the disc :foottap:. Oh well, such is life in ported'ville.

 
#16 ·
You're not taking into account the FR linearity of your dvd player, receiver, any type of EQ unit if you have one, and amplifier. I can assure you they won't all be perfectly flat to 10hz.

You're also using peak cone excursion as opposed to RMS, which is fine if you are going to listen to sine waves, but probably not the best representation of the way sounds are recorded in movies, music, and games.

You're also assuming you're going to watch movies, music, and games at master volume levels equivalent to using the full rated power from you amplifier for all dynamic peaks, which you won't. You're amp would be clipping like crazy and if you are properly calibrated, it would be painfully loud.

You're also assuming there is hotter content below 12hz than there is above 12hz over the course of a movie, song, or game, of which I can think of less than a handful.


So sure, if your upstream electronics all have perfect FR linearity to 10hz, your bass content is shaped like an extended sine wave instead of a burst, you're going to watch at volume levels that constantly drive your amp into clipping, and you happen to be doing this while watching that one particular movie with hotter <12hz than >12hz content, you should worry about the infrasonic material.

:innocent:


One would think the sound designers would digitally hack this stuff out before it hits the sound track on the disc
I'm glad they don't.
 
#17 ·
I have nothing against LLT subs but one thing I have noticed since building a multi tuned sub which is net nearly 450 litres each and run by a Q18 in each that the low tune off 12.5hz gives me less impact where it counts than the 17.5hz tune. Transormers 2 for example there is much more bass impact on all scenes in the 17.5hz tune than the low tune. Even the 21.5hz tune has bassier elements to it.

If I never had built the subs with 3 tunes then I would never have found this out. The 3 tunes give me so much more flexibility than compared to just one tune. I can even go sealed and be flat to 10hz so in my case I wouldn't limit myself to just one tune ever again.

Music is best in the 21.5hz tune compared to the others too.

Don't get me wrong the low tune is fun for stuff like bassotronics, opus dei and so on but thats it in my experience.

cheers

Graham
 
#23 ·
That's what EQ is for :) - If you used EQ to get the same response from each of your tunes over the same FQ range then they should sound the same. The lower tune will obviously have more headroom at the lower end and the higher tune will have a bit more headroom further up. Choose where you want the headroom and EQ to suit your preference.
 
#19 ·
I guess that's the beauty off probably being one off the only people to build one and actually be able to test the differences between a sealed, low, mid and a high tune in one go.

Its easy to build a particular sub with a particular tune and say that sounds best but you need to be able to test 3 different subs in the same location which is never on the cards.

But I can. Yippee!

cheers

Graham
 
#24 ·
Using additional eq adds in group delay, which becomes more noticeable further up the range. Why eq it in if you can do it without the eq. Besides, doing it the eq route doesnt always result in the same sound, even if the spl charts look the same. There are some things an spl graph cant tell you.
 
#25 ·
Add in time domain measurements then :) I find the room has more impact on what the bass sounds like than the topology of the sub used. YMMV. Have you done any testing to see how much EQ is required before the group delay actually becomes audible let alone a problem ? I'd be interested to read any research that has been done in that regard.
 
#26 ·
Your spot on about the room :T

As far as group delay goes, I only really have my experience of modelled subs group delay, of which I have built a few. Ported subs always have much greater GD than sealed, and Ive never heard a ported sound as quick and accurate as any sealed IMHO. I have always tried to keep eq I use to the bare minimum, and auto eq systems like Audyssey take into account the effect have on things like GD so as not to introduce the effects into what you actually hear. What I consider the effects of group delay is based upon experience of ported vs sealed subs, and the modelled GD of those I have built. I havent yet actually tried to add in GD with eq on purpose to test how that sounds, Ive simply always tried to avoid it as much as I can.

As far as trying to define how added GD actually sounds, I'm not sure I could convey that that well, or do it with any real authority. As you say, to honestly do that would require measurement data to back up what you hear/say.
 
#27 ·
Thanks for the answer mate. I've heard good and bad sealed and ported subs. I find its the implementation that matters more than the topology used. That said I have two largish sealed subs :)
Your spot on about the room :T

As far as group delay goes, I only really have my experience of modelled subs group delay, of which I have built a few. Ported subs always have much great GD than sealed, and Ive never heard a ported sound as quick and accurate as any sealed IMHO. I have always tried to keep eq I use to the bare minimum, and auto eq system like Audyssey take into account they have on things like GD so as not to introduce the effects into what you actually hear. What I consider the effects of group delay is based upon experience of ported vs sealed subs, and the modelled GD of those I have built. I havent yet actually tried to add in GD with eq on purpose to test how that sounds, Ive simply always tried to avoid it as much as I can.

As far as trying to define how added GD actually sounds, I'm not sure I could convey that that well, or do it with any real authority. As you say, to honestly do that would require measurement data to back up what you hear/say.
 
#28 ·
That's what EQ is for - If you used EQ to get the same response from each of your tunes over the same FQ range then they should sound the same. The lower tune will obviously have more headroom at the lower end and the higher tune will have a bit more headroom further up. Choose where you want the headroom and EQ to suit your preference.
The only EQ I have applied is Audyssey. With having two subs in my optimum positions I get a very flat response without any EQ at all. There is no point is adding any EQ to any off the tunes because that is the whole point, I don't want them to sound the same. The very point off doing the 3 tunes is for flexibility on what format I want to listen to.

Low tune 12.5hz - bassotronics and crazy low bass music. Fun tune
Mid tune 17.5hz - movies. This is way the best tune for films.
High tune 21.5hz - Music. Again this has much more impact for music than any off the other tunes.

See my graphs on my 15 cu ft sub build to see what I mean.

http://www.hometheatershack.com/for...5-cu-ft-fiq18-multi-tuned-ported-subs-16.html
 
#29 ·
Wouldn't a sub with a greater group delay sound boomier hence why a sealed sub sound better with music because you hear the bass tones with more definition with being faster. Some ported subs you don't hear this as effectively because 2 bass tones almost sound like one because the transition from one bass note to another isn't there. Something like that. Or I could be completely wrong.

cheers

Graham
 
#32 ·
Dan,

I am flat to 10hz in sealed mode and get extremely good bass. I watched resident evil with very good effect but it still doesn't compare output wise to the low tune. The 21.5hz tune has alot more 20hz and up bass than any off the other tunes including sealed and with only having to set the hpf on minimum, its happy days.

Have you heard the new daft punk album for Tron. Brilliant album.

I can run 800 watts them in sealed without going over max excursion. They are at 16.5 cu ft sealed because I add the volume off the ports to the internal box size due to them being blocked. Qtc is at 0.76. Here's my winisd file.

cheers

Graham
 

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#34 ·
Some people inevitably want more though.

The AE AV15-X woks well in 100 litres. If you built a 300 litre cab in an LLT you will get more output, but if you put 3 drivers and triple the power in there the sealed will beat it hands down all the time. IMHO that is the only way to compare a sealed to a ported. A sealed will always give the best performance, but at the cost of triple the price.
 
#35 ·
1 cu ft is about 14" square which is only going to fit a 12" driver at best and the peerless 12" driver only gives 96db at 20hz and that is only with 300 watts max which is not a great amount to be honest.

My sunfire HRS-12 which was powered by a 1000 watt amp and I have to say that was pretty potent but thats a £900 sub and competed very well against the SVS PC13 ultra as I demo'd them side by side and I can't see the peerless driver keeping with that sub.

I would go back to sealed but it would have to an IB as anything else in comparison would be a backward step because off the amount off drivers and amps I would have to buy.

cheers

Graham
 
#37 ·
I don't use a peerless driver. Mine is the TC Sounds 12" 1000 series and it can get plenty of output in the 1.0 cuft box it's in. I would ideally love to have a folded slot port sub, but I don't think that would go over well with the wife and neighbors. :paddle: Considering it cost me less than the Dayton sub-120 to make I'd say it is a fantastic deal in the end. :T
 
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