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post #181 of 919 Old 07-26-2006, 11:48 AM
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Nice post Sherv :)

Beautiful explanation Steve with a not so beautiful ending. :confused:

Do I make a good moderator or what? ;)

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post #182 of 919 Old 07-26-2006, 11:49 AM - Thread Starter
 
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Mark Seaton ... Thanks for the heads up. I called my brother, and he got a chuckle out of the fact that you mentioned Baltic Birch.

The reason he got a chuckle was he was trying to figure out how to explain to me that using MDF for this would be a BAD idea ... now he doesn't have to.

It will be Birch, and you are right, that is all they use. Tuning will be 14 Hz ... and he has some pretty cool ideas for a single box, dual 15 inch driver sub ... :)
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post #183 of 919 Old 07-26-2006, 12:08 PM
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The reason he got a chuckle was he was trying to figure out how to explain to me that using MDF for this would be a BAD idea ... now he doesn't have to.
The best rout from my understanding is to go with the BB rout with .5 to .75 layer of MDF on the inside. That would be one heavy unit with both drivers loaded but one to be proud of.

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post #184 of 919 Old 07-26-2006, 12:43 PM
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Tuning will be 14 Hz ... and he has some pretty cool ideas for a single box, dual 15 inch driver sub ...
In the way your going about this Craig, your going to wind up with a sub that should come in as one of the better DIY projects out there. Do you plan on veneering it?

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post #185 of 919 Old 07-26-2006, 12:52 PM
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PS - bosso, can you show me where you got that second statement that you say is mine from?
I said that these were all subs that you complimented (as opposed to the derision of the originally suggested specs in this thread).

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Soundsplinter RLp-15 driver in 24" dia. x 46" H Sonotube, 300L net internal volume, 8" dia. x 33" L sonotube port for 17.5 Hz enclosure tune.
(from OP HMenke)
SC:
Quote:
How many layers of 3/4" MDF were you planning on using for the end caps? One probably won't be enough. I'd use at least two for the top and three for the bottom. I've modeled both the dual 2ohm and dual 4ohm versions and based on what I see, I prefer the dual 4ohm version even though it won't extend as deep. Take a look at a 7.5 cubic foot enclosure with a 6" port that is ~28" long (~17.7hz tuning) fed with 1000 watts.
Your tube wouldn't need to be nearly as large as you are thinking.
He apparently went with the 300l, 17.5 tune and 700W.
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VERY nice, good work on the finishing. All these super flat FRs are tempting me to try a BFD out.
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post #186 of 919 Old 07-26-2006, 01:02 PM
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(from OP HMenke)
I gotcha. My suggestion for a higher tuning in his case was due to me not being aware of the Le and Bl parameters of the RLp15 affecting the simulation the way they do, as that was one of the early RLp15 deisgns. I was concerned about the high -3db point the software was showing in comparison to something like the Avalanche 15. After some real world measurements showing that wasn't a problem, and an explanation by LMS, I realized there was no need to tune higher with the RLp15, and haven't suggested tunings that high for it since.

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All these super flat FRs are tempting me to try a BFD out
:) This was prior to me having a soundcard that I could use with RoomEQ Wizard, so I had no accurate FR sweeps at that stage.
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post #187 of 919 Old 07-26-2006, 01:42 PM
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trust me, you should have at it...it's a very big learning experience, and a true eye opener. You don't have to start with an aggressive design (multi high excursion drivers, LLT, etc), but you can start with a simple single design, and try different configurations like Stevenn did
Imo this is one of the things so attractive about DIY. A guy can really learn by the nuts and bolts approach. It seems like allot of times we, or maybe I should say I, learn things about this hobby that I don't even know I know until it comes up.
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yes, I am delighted with the outcome of my subwoofer. It is the perfect match of what I've been looking for (excellent extension, with very visceral impact in the 20-60hz range)..... Fortunately, it has far exceeded any single driver commercial sub I've heard (a la Ultra, EP600's, etc) in every category, and it goes way deeper and lower than any of them. While it doesn't have the deepest extensions that an LLT design has (compared to say an RP-L15 sonotube like Chuck's....and just slightly at that), it does sound (to me) slightly more musical overall.
Your project turned out absolutely stellar Sherv from what I've seen and heard of your and Chucks comments and graphs. Did you ever decide to build a second unit or did the center put you over the top for awhile?

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post #188 of 919 Old 07-26-2006, 02:09 PM
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Brain food;

Variable port tuning.

Not quite but you get the idea.
Kingdaddy's sub;
http://kingdaddy.linaeum.com/Sonosub/

Low tune, high tune, sealed, all in one design. Optimize performance
in real time for whatever mood your are in ;)

Are you clever enough to design one ?

DIY sub project to beat store bought subs ? if so, hire a monkey to design
and build as it should be hard at all :p :)



The storm was gone, but dark clouds still hung around
The perfect setting for things to come......

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post #189 of 919 Old 07-26-2006, 02:34 PM
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So at some point in the future, Craig will be doing a blind comparison of this DIY unit vs the DD18, Axiom 500/600 and some other subs?
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post #190 of 919 Old 07-26-2006, 02:36 PM
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"As shocking as this may seem, Fs has almost nothing to do with a subwoofer's ability to play deep bass. It has much more to do with excursion."

I agree the importance of Fs is overrated; the difference if Fs were a more subwooferish 18 Hz is probably a dB or so.

Nevertheless, lower Fs is more desirable than high; the lower the compliance the more power is required to displace the suspension.

Availability/cost is a fine reason for choosing the RLp15; in fact, it was at the top of my list until the Ascendant closeout sale came along.

Just for kicks, I used WinISD to compare the RLp15D4 with the same driver save for a more compliant suspension; I raised the compliance and let WinISD autocalculate new values for Vas, Qe, and Fs of 18 Hz.

I've attached the result; the yellow line is the stock RLp15D4.

Steve,

"Per watt, a larger enclosure with a lower tune will demand LESS excursion in the mid to upper bass range from a driver."

Not so, as you allude to a bit later:

"But what issues do we face with using such a low tune? ...overall sensitivity takes BIG hit.

The larger enclosure will increase the sensitivity - especially the low end sensitivity - BIG TIME."

You'reOVERSTATING the effect on sensitivity. Refrence efficiency is determined by driver parameters alone; the box type will have the biggest effect at the lower freq.

"The larger diameter port also means that the length to diameter ratio won't be as big, keeping the first port resonance at least above 180hz,"

AFAIK the organ pipe resonance is determined solely by the length.
LL

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post #191 of 919 Old 07-26-2006, 02:48 PM
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Originally Posted by noah katz
Not so, as you allude to a bit later:
I didn't say per given output level, I said per watt.

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AFAIK the organ pipe resonance is determined solely by the length.
Good point, I was mistaken. Fixed it now.
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post #192 of 919 Old 07-26-2006, 03:14 PM
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Too bad about the supercilious tone because it detracts from what otherwise would be one of your better contributions. While its clearer why you take the position you do, there are various comments which do stretch things.

Quote:
Originally Posted by SteveCallas
Since the driver is almost 100% responsible for all output, all those ill ported effects don't get a chance to play a role, and the subwoofer and bass quality are just like that of a sealed subwoofer in this range. So what becomes of the ill effects? They are pushed down into frequencies so low (<20hz) that they become non issues, as those frequencies are tactile, not audible, and our sensitivity to those frequencies is extremely low, as showed by the Munson curves.
What you are not saying is that those same curves make us particularly susceptible to annoying port artifacts at higher frequencies which is an issue. . While a large diameter port does have less resonance than multiple vents, the problem does not go away. Port resonance at higher frequencies does colour the sound and can be measured well above 200hz. It doesn't take much output to change how the bass sounds and a primary reason why vented subs can sound so different from one another. Port noise along with inadequate transient response have me using ported subs for HT applications and sealed stereo subs for music listening

Quote:
How can we make transient response, group delay, overexcursion, negative port effects, and in room FR better? Seeing as they are all based upon the tuning frequency of the enclosure, the answer is to lower the tune. By using a very low tune, the driver becomes almost 100% responsible for output down until the lowest regions, at least until ~30hz, an area above which I consider the musical region, and an area which encompasses your "mid to upper bass range".
Those effects are not all based upon tuning frequency though tune does influence them. Amp, driver, size of enclosure, port length and diameter, port flaring has as much if not more of an impact than tuning frequency alone . Lowering tune to the max doesn't cure all those ills and may actually exacerbate some of them to the detriment of the sound.


Quote:
The larger enclosure will increase the sensitivity - especially the low end sensitivity - BIG TIME. It will also allow you to mold a FR that is very flat, but with a shallow rolloff (much more shallow than a sealed design, as most rooms don't give full 12db/octave gain) starting at ~40hz, and extending down until your tuning point, with the 4th order rolloff occuring somewhere below that. This shallow rolloff meshes extremely well with typical room gain, giving a reasonably flat response down to very low frequencies, as can be seen from chasw's, wackii's, w8liftr's, my own, or any other LLT owner's in room FR measurements.
That's the primary reason I like big enclosures as well.

Quote:
The larger enclosure also enables you to use a much larger diameter port, 6" or larger to be exact, with the largest at the moment, 10", belonging to steve nn's beast. This dramatic increase in port area not only reduces the audible chuffing and output compression limits, it essentially eliminates them as a concern altogether, as those limits are well below what the increased port area allows. Add a simple 3/4" rounder to the outer layer of MDF to act as a DIY semi flare, and the audible chuffing limit is a thing of the past. The larger diameter port also means that the length to diameter ratio won't be as big, keeping the first port resonance at least above 180hz, where it won't be audible. The larger size of the enclosure also allows you to have lots of clearance between the interior port opening and any surrounding planes, whether that be an MDF wall or brace, a cardboard sonotube, or even the driver itself.
But port resonance doesn't ever completely go away as you suggest. Flared vortex like openings help greatly in keeping resonace to a minimum but I remain unconvinced that even in the largest subs the port resonance can be made inaudible. Its why one can usually tell if they are listening to a sealed vs. vented design. You listen to enough subs and you realize that the port plays a big role in colouring the bass.

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Ok, so we've eliminated or stifled all the negative effects associated with ported subs that prevent you from getting the detailed, articulated, and tight bass that you want, and now you have a superb sounding sub.
I wish that were the case as you clearly believe but port issues have not been eliminated. Nor has the common problem with transient response been removed. The larger enclosure will generally produce a better sounding sub than a smaller vented one but lets draw the line there. To say it can outperform a sealed sub in the mid-bass is a non-sequiter. In fact a great sealed design like a DD-18 will outperform nearly all large vented subs because of its better transient response especially in the critical mid-bass. It just doesn't follow that a vented unit with inferior transient capabilities, its attendant group delay and minimal port resonance will sound tighter than a sealed design. You can make the enclosure as large as you want and the tune as low as you can get it but it won't change those inherent characteristics of its design relative to a sealed sub.


Quote:
Sounds to good to be true you say?
It does. While there is no doubt that sounds better than most commercial vented subs there is too much hyperbole when it comes to sealed comparisons.

Quote:
There is one drawback, LLT subs are larger, sometimes much larger, than a traditional ported or sealed subwoofer.
Not a drawback for me because I think they look good the bigger they are. :cool:

Quote:
Does it now make sense why a larger and lower tuned subwoofer will perform better than dual RLp15s in 250 liters tuned to 18hz?
I certainly understand your position better so thanks for clarifying it, but on several of the critical points mentioned above I remain unconvinced particularly as my greater concern is in the mid bass performance not in sub 20hz output.

John
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post #193 of 919 Old 07-26-2006, 05:28 PM
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jakeman, let's go over a few things.

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What you are not saying is that those same curves make us particularly susceptible to annoying port artifacts at higher frequencies which is an issue
Yes, we are more sensitive in higher bass frequencies then lower bass frequencies, that's exactly what the LLT banks on - it pushes the negative effects into very low frequencies where they will not be audible. Those negative effects will occur at higher frequencies with more traditional designs like your Axiom subwoofers.

Quote:
While a large diameter port does have less resonance than multiple vents, the problem does not go away. Port resonance at higher frequencies does colour the sound and can be measured well above 200hz
With an 80hz crossover, how high should the first port resonance be to no longer be considered an issue? Any real data you have on this matter would be appreciated.

Quote:
Port noise along with inadequate transient response have me using ported subs for HT applications and sealed stereo subs for music listening
Port noise is eliminated with the large diameter ports used in an LLT design - this can be verified with Bill Collison's work on ports and some simulation. Impulse response is a measure of stored energy decay in the subwoofer - because FR stays very linear until the 4th order rolloff occurs below tuning - which is at a very low frequency - and because there is no high pass filter in play, there is no reason the impulse response of an LLT should measure poorly. I get the impression your are trying to judge a LLT based on your own experience with ported subwoofers you have listened to - it's not a fair comparison. It would be like me judging all sealed subwoofers based on the performance of a 1' cubed HTIB sealed subwoofer.

Quote:
Amp, driver, size of enclosure, port length and diameter, port flaring has as much if not more of an impact than tuning frequency alone
First off, the amp and driver should not be considered a variable in the definition of the design alignment - I am explaining the benefits of the design compared to traditional ported and sealed enclosures for a given amp and driver - and it is to be assumed they are quality components. As for the other variables you mentioned, yes, they play a role, but the point I am making is that by using a very low tune in an appropriately sized enclosure, those aspects of performance are substantially improved in the audible range of bass reproduction, as they don't begin to become issues until subsonic frequencies, in which case it isn't really of consequence anymore.

Quote:
Lowering tune to the max doesn't cure all those ills and may actually exacerbate some of them to the detriment of the sound.
Please give me a specific example of how a very low tune in a large enclosure will exacerbate some of them to the detriment of the sound.

Quote:
But port resonance doesn't ever completely go away as you suggest
It does if the port resonance is out of the range the subwoofer will be creating moderate output in. I'll ask you again, with an 80hz crossover, how high should the first port resonance be to no longer be considered an issue? Any real data you have on this matter would be appreciated.

Quote:
Flared vortex like openings help greatly in keeping resonace to a minimum but I remain unconvinced that even in the largest subs the port resonance can be made inaudible
Please explain to me how a large flare helps greatly in keeping port resonance to a minimum. If anything, for a given length of port, a larger flare lowers the first port resonance because the air in the port has to travel even further over the surface of the flare.

Quote:
You listen to enough subs and you realize that the port plays a big role in colouring the bass.
I've just explained to you how some port effects are eiliminated while others won't begin to take place until subsonic frequencies. How can they color audible bass? You may have listened to a lot of subwoofers, but how many LLT designs have you listened to?
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post #194 of 919 Old 07-26-2006, 05:44 PM
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...bosso and I have had numerous conversations... for him to then say he's sees no benefit in using a larger and lower tuned design than a 250 liter 18hz tuned enclsoure using two RLp15s, well, I'm just baffled (no pun intended).
Make no mistake, I've been a proponent of the virtues we have discussed for several years now (and have taken quite the ear beating for them in years past). I just want to see them verified in the LLT the same as I have verified them in sealed designs, which took a few dozen iterations thereof to accomplish and good measurements to 1Hz.

BTW, are we sure Mike didn't mean each driver in 8.5 cubes, tuned to 18Hz? Craig?

It seems to make more sense with the rest of his quotes in the beginning of the thread as I read them over. And his point of not tuning below 17Hz is better made with 1 driver per box vs 300l tuned to 14Hz.

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post #195 of 919 Old 07-26-2006, 06:05 PM
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BTW, are we sure Mike didn't mean each driver in 8.5 cubes, tuned to 18Hz?
Based on the recommendations from SoundSplinter's website, I doubt it. If so, even his "space-saving" design that he mentioned would be larger then the website's recommended EBS design, and that doesn't make any sense. What looks to be the website's preferred ported recommendation is 3.5 cubes and a 24hz tune. It goes on to say this:

Quote:
Originally Posted by SoundSplinter
Home audio enthusiasts should shoot for 3.5 cu ft net internal volume, with a tuning frequency between 18 - 25 Hz.
Quote:
I just want to see them verified in the LLT
While I guess the impressions of the members who have built some so far apparently don't mean anything (and that's your perogative), you may well get your wish with some real measurements - and I'm not referring to Craig's project.
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post #196 of 919 Old 07-26-2006, 06:25 PM - Thread Starter
 
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Quote:
Originally Posted by bossobass
Make no mistake, I've been a proponent of the virtues we have discussed for several years now (and have taken quite the ear beating for them in years past). I just want to see them verified in the LLT the same as I have verified them in sealed designs, which took a few dozen iterations thereof to accomplish and good measurements to 1Hz.

BTW, are we sure Mike didn't mean each driver in 8.5 cubes, tuned to 18Hz? Craig?

It seems to make more sense with the rest of his quotes in the beginning of the thread as I read them over. And his point of not tuning below 17Hz is better made with 1 driver per box vs 300l tuned to 14Hz.

Bosso
Bosso .. .yes, it was each box at 8.5 Liters (240L) and one driver per box.

However, after spending about an hour on the phone with my brother earlier, he is pretty confident about doing twin 15's in one large, relatively consumer friendly, 600 liter enclosure ...

Stevenn .. .this box may just get stained oak ... not sure yet.

Jesse .. yes, it will be blind tested.
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post #197 of 919 Old 07-26-2006, 06:50 PM
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Steve,

"Per watt, a larger enclosure with a lower tune will demand LESS excursion in the mid to upper bass range from a driver."

The point is that the Fb has little effect in the mid to upper bass.

"I've just explained to you how some port effects are eiliminated while others won't begin to take place until subsonic frequencies. How can they color audible bass? You may have listened to a lot of subwoofers, but how many LLT designs have you listened to?

How many have *you* listened to. Correct me if I'm wrong, but AFAIK you've built your own LLT, and maybe listened to a smattering of commercial subs.

I tend to agree with a previous poster, I think your attitude exceeds your experience.

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I tend to agree with a previous poster, I think your attitude exceeds your experience.
Sounds familiar. :rolleyes:
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post #199 of 919 Old 07-26-2006, 07:25 PM
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The point is that the Fb has little effect in the mid to upper bass.
That's just not true. Tune a small enclosure to 50hz and tune a larger enclsoure to 15hz, use the same quality driver in each, and tell me how the mid to upper bass sounds. Not only did just about everyone at Craig's blind test get together prefer the Ultra in the 16hz tune, but even Ed's review makes mention of how it sounds better. And I've explained, logically, all the reasons why.

Quote:
How many have *you* listened to. Correct me if I'm wrong, but AFAIK you've built your own LLT, and maybe listened to a smattering of commercial subs.

I tend to agree with a previous poster, I think your attitude exceeds your experience.
Noah, I have a lot of respect for you, and if you want to logically debate my statements, by all means, do it, I'd really like to have that debate. But by not doing so, and just using my young age and lack of ~25 years or so of listening to subwoofers as a way to disregard all of the points I brought up (just as some others here do), well....that's pretty weak as far as I'm concerned :(
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post #200 of 919 Old 07-26-2006, 08:52 PM
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Stevenn .. .this box may just get stained oak ... not sure yet.
Considering your decor, I think that's a great idea. I was having a senior moment wondering what finish you would be going with knowing that your going with the BB. The 14 ply edges dress up very nicely from what I've seen. Varathane or the like really enhances.

I went ahead and took the liberty of tuning my test mule up to 20 Hz as a little experiment. You know it turned out better than I thought it would to be honest with you. When skimming through Eagles (hell freezes over) I found myself raising the SW trim a notch, where with the 16 I might cut it back a dB. On the drum roll at the end of (I cant tell you why - song) I noticed a little smearing with the 20 where the 16 comes across detailed and controlled. Either than that it was very close at -15 DTS.

In the movie FLIGHT of the PHOENIX, I noticed the 20 Hz tuned version had about a dB or two on the 16 in most to all of the material. Both are very hard hitting and precise, but the 20 Hz version gets the cigar for muscle although it was ever so close. At the very end I could sense a little compression when the plane flies out of the canyon with the 20, where with the lower tuned 16 holds true.

Now this enclosure is about 200 liters net, so it's not a true LLT. One thing I find for certain and it would also relate to Sherv's experience, that being the 15" AV and 15" RL-p suffers much less from some of the tune change traits that I have noticed with other smaller drivers. I'll not suggest what to attribute that to, but it is noticed.

If I were to throw my dual driver LLT into the mix, it would come across a little like the two in one. Definitely a nice ride imo, but Tuned slightly higher than what your going with and differing in the nice BB your using. Extensive bracing and veneer go along ways, but admittedly not as far as extensive bracing and BB 14 ply.

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post #201 of 919 Old 07-26-2006, 08:55 PM
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Steve,

Noah's comments are not un-warranted.

The problem is more a matter of perspective. If you talk with someone well practiced in any field, particularly outside of audio, you will generally find that if you ask them about what they really know, they will answer with all sorts of things they would like to have the answers to or suspicions they would like to test further. If you ask someone who is new to the same field what they know, they will likely rattle off all of the things they've most recently learned and conclusions they've drawn from it. There is that particular crest of realizing just how much more there is to be explored or confirmed. Suspicions and expectations are very different from confirmed or proven facts.

Yes, there is a lot of misconception in the marketplace. At the same time, most such misconceptions arose from premature conclusions being drawn without good understanding of what was occuring or why.

Quote:
Originally Posted by SteveCallas
Ok, sounds good. But what issues do we face with using such a low tune? First, the port issues can become amplified, as we're now looking at pushing much more air through the same port area - compression and chuffing can become major problems - and since the port actually has to be longer to accomodate that lower tune, the first port resonance can be low enough as to be audible based on the subwoofer's operating range.
Quote:
The larger enclosure also enables you to use a much larger diameter port, 6" or larger to be exact, with the largest at the moment, 10", belonging to steve nn's beast. This dramatic increase in port area not only reduces the audible chuffing and output compression limits, it essentially eliminates them as a concern altogether, as those limits are well below what the increased port area allows. Add a simple 3/4" rounder to the outer layer of MDF to act as a DIY semi flare, and the audible chuffing limit is a thing of the past.
Can you state with any certainty that there aren't other problems that can creep in the operation of a large port? Does the sharpness of the corner and relative damping have any effect in operation and listening?

Quote:
With a larger enclosure, for a given length of port, the diameter can be bigger while keeping the same tune, making it easier to keep the first port resonance at least above 180hz, where it won't be audible. The larger size of the enclosure also allows you to have lots of clearance between the interior port opening and any surrounding planes, whether that be an MDF wall or brace, a cardboard sonotube, or even the driver itself.

Ok, so we've eliminated or stifled all the negative effects associated with ported subs that prevent you from getting the detailed, articulated, and tight bass that you want, and now you have a superb sounding sub.
Are you certain that resonances above the low pass filter won't be audible? Do the enclosure and vent size have any relation to the amplitude of those port resonances? What does affect those port resonances? Is there some specific point at which they become audible?

Quote:
Sounds to good to be true you say? There is one drawback, LLT subs are larger, sometimes much larger, than a traditional ported or sealed subwoofer.
What happens with large, long dimensions inside an enclosure? Do they always or never pose a problem?

Finally, you have used certain subjective reports of the variable tuning with SVS subs. How do we know the perceptions are due to tuning frequency vs. frequency response or other resultant changes? Do we know if the general perceptions noted by those building huge vented subwoofers is a symptom of the tuning, port resonance, port velocity, and shallow response and not simply a reaction to more sufficient output capability in their specific use?

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post #202 of 919 Old 07-26-2006, 09:46 PM
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Originally Posted by SteveCallas
Ok, I guess I have to explain this again.

You've stated in the past the traditional ported subwoofers just don't give you the detail, articulation, and tight bass you are after, correct? Have you ever spent the time to question why that is as opposed to just lumping it all together and saying because it's ported? When the responsibility of creating output switches from the driver to the port, you get a few negative side effects. Trasient response below a certain frequency range takes a hit, group delay increases, a high pass filter is needed to prevent the driver from reaching overexcursion (which adds more group delay around the range of the tuning frequency), it may suffer from audible port effects, and since most are designed to be flat anechoically, in room, they often have a large hump down low, which may result in a muddied sound. That essentially covers the bulk of the ill effects associated with ported subs, and probably explains why - based on the subwoofers YOU have listened to - you prefer sealed.
Some sealed boxes are designed to be flat anechoically. They should also have the same problem as the vented box...

Quote:

Now sealed subs have a set of drawbacks all their own, - which I've covered those many times before - so what can we do to find a way around these issues? How can we make transient response, group delay, overexcursion, negative port effects, and in room FR better? Seeing as they are all based upon the tuning frequency of the enclosure, the answer is to lower the tune.
How about quarter wave length resonance of the port? That is really difficult to deal with. Without solving the problem to a satisfactory degree, the vented box is still not the same as sealed box, no matter how low you tune the vented box.

Quote:
By using a very low tune, the driver becomes almost 100% responsible for output down until the lowest regions, at least until ~30hz, an area above which I consider the musical region, and an area which encompasses your "mid to upper bass range". Max excursion is no longer reached early on, and thus, a high pass filter - and its accompanying negative effects - is no longer needed.
This 30hz and Munzo curve you have cited later have their historical background. The study was done when the low end frequency of transducers were no lower than 30hz and overlook the fact, the sensation of low frequency is to be felt, not heard and such a change is definitely not abrupt at a fixed frequecy. It is gradual. The question is where is that curve? It is not a surprise that the study at that time was commonly done by earphones, not loudspeakers, which further undermined the importance. The determination of 30hz is also flawed. The frequency is based on the lowest note on instruments as a steady signal. But music is meant to be changing in pace and rhythm. This dynamic behavior has increased the bandwidth requirement at both high end and low end. Why CD sampling rate was set to 44khz at the very beginning and now the new sampling rate is 88khz or even higher? It is 1) through years of actual field listening tests and we realized there is a deficiency with 44khz and 2), which is more important, through studies and research, it is clearly shown the bandwidth of a dynamic, constant changing signal is wider than if the signal is played at steady state.

Quote:
Ok, so we've eliminated or stifled all the negative effects associated with ported subs that prevent you from getting the detailed, articulated, and tight bass that you want, and now you have a superb sounding sub. How is this different from a sealed subwoofer? It's different because you have better overall sensitivy, much more clean low frequency output, a FR that will mesh better with typical room gain, and no need for any "excursion-eating" low end EQ. It is as close to getting your cake and eating it to that I know of for a subwoofer design, aside perhaps (*for Mark) from an even larger bass horn. It fixes the traditional problems associated with both ported and sealed subwoofers, all in one design.
Don't take it personally. If someone presents this idea at a conference, I am pretty sure the audience would ask "Is it possible that you can lose the advantage of the vented box and sealed box at the same time, instead of getting them?"


Brian
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post #203 of 919 Old 07-26-2006, 10:40 PM
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"The point is that the Fb has little effect in the mid to upper bass."

"That's just not true. Tune a small enclosure to 50hz and tune a larger enclsoure to 15hz, "

I thought we were restricting the discussion to LLT and not-so-LLT, like a big SVS or Hsu, meaning in either case Fb is far below mid-bass. My mistake.

"Noah, I have a lot of respect for you, and if you want to logically debate my statements, by all means, do it, I'd really like to have that debate. But by not doing so, and just using my young age and lack of ~25 years or so of listening to subwoofers as a way to disregard all of the points I brought up (just as some others here do), well....that's pretty weak as far as I'm concerned."

It's not a question of logical debate, I have no argument with what you're saying on that basis. What's weak is your insistence that you have the best answer for the best subwoofer.

I think it was Ed Mullen who nailed it a few pages back. There's nothing an LLT can do that a sealed system can't do better,by ratcheting up the overkill a moderate amount beyond what you espouse.

I have a lot of respect for you as well. I've seen you get a solid grasp on the principles in an impressively short amount of time.

But as Mark articulated so well, there are many complexities. How many of his questions can you answer in the affirmative?

Mark is so right about this: "If you ask someone who is new to the same field what they know, they will likely rattle off all of the things they've most recently learned and conclusions they've drawn from it. There is that particular crest of realizing just how much more there is to be explored or confirmed."

What's amazing is that Mark is a young guy and already knows this. I guess he gets a lot of mileage out of all that caffeine :)

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post #204 of 919 Old 07-26-2006, 11:10 PM
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What's amazing is that Mark is a young guy and already knows this.
He's young? For some reason I imagined that Mark was in his 40s at least. Hah.
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post #205 of 919 Old 07-27-2006, 12:28 AM
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This post is not back-pedaling in the least, but I do want to acknowledge that Steve Callas has made a solid case for his subwoofer design of choice. Is the LLT the 'be all end all' solution to perfect bass? No. Does he have better bass than 99.9% of the unwashed masses? You bet, and that's a big score in anyone's book.

He's got plenty of headroom, low distortion, a flat in-room FR with excellent deep extension and a good complement to room gain, an apparent absence of audible artifacts, and the design pushes the attendent phase and transient issues well toward the infrasonic region.

There is nothing to suggest that this design will be anything but an excellent performer by any normal criteria and standards. Stepping back from the PC screen for some 'real-world' perspective, I'm betting dollars to doughnuts that his sub performs darn well when it comes time to just spin some CDs and DVDs. And I'm also expecting Craig to draw similar conclusions about his own creation; it's pretty hard to screw-up your bass when you've nailed all the basics.

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post #206 of 919 Old 07-27-2006, 05:57 AM
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With all due respect to the proponents of a given design, who would praise the performance of a commercial sub before it's been tested?

Who has a slogan that reads, "Trust us, it will perform. No testing is required.", and if there was such a logo, wouldn't we all demand to see the proof?

There are indeed many reasons that a good design may not perform so well in real life.

Driver parameters are never a given, based upon published specs alone, as well as any assumption that the real specs are consistent from one driver to the next.

Commercial designers like TV, Seaton, Danley, etc., spend countless hours building and testing prototypes that verify or belie the models and many more hours putting that end product through various tweaks and into Beta.

The amplifier used is another variable. Then there is the fact that a subwoofer is only as good as it's ability to integrate with a MC system, so the delay, phase, filter options and EQ need to be considered to the point that they will render predictable results.

Go through the painful process of design, build, test, measure, beta test, setup and integrate...then you may make claims with a high degree of certainty.

I'm over bristling at youthful indiscretion as Steve and I have hashed most of this out (and I apologize to everyone who had to endure that rather lengthy process), and I also agree with most that Steve is doing a great job so far, but...

Prove the claims if you want me to buy anything.

Also, a huge hats off to Craig who once again puts his money where his mouth is and takes us all on the ride with him through another leg of the journey. This is great stuff, IMO :)

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post #207 of 919 Old 07-27-2006, 05:59 AM
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This post is not back-pedaling in the least, but I do want to acknowledge that Steve Callas has made a solid case for his subwoofer design of choice. Is the LLT the 'be all end all' solution to perfect bass? No. Does he have better bass than 99.9% of the unwashed masses? You bet, and that's a big score in anyone's book.

He's got plenty of headroom, low distortion, a flat in-room FR with excellent deep extension and a good complement to room gain, an apparent absence of audible artifacts, and the design pushes the attendent phase and transient issues well toward the infrasonic region.
Not to be a suck-up Ed, but from my simple perspective your voice of reason runs wide and true.
Quote:
There is nothing to suggest that this design will be anything but an excellent performer by any normal criteria and standards. Stepping back from the PC screen for some 'real-world' perspective, I'm betting dollars to doughnuts that his sub performs darn well when it comes time to just spin some CDs and DVDs. And I'm also expecting Craig to draw similar conclusions about his own creation; it's pretty hard to screw-up your bass when you've nailed all the basics.
I mentioned a possible perspective earlier in this Thread that I don't see taking form in Craig's decision process at all. I would even go so far as to suggest he has some leeway from my previous post, so I don't see how he can go wrong. Nope!.. I don't see his creation coming out bad at all. In fact I'll bet you a dollar bill that he'll be quite thrilled!?

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post #208 of 919 Old 07-27-2006, 06:37 AM
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Ed Mullen, you just went up a few points in my book.

Why the constant attack? You ask questions, he answers, then all you can come back with is more "your to young to know anything, and you should talk nicer to your elders."

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If you talk with someone well practiced in any field, particularly outside of audio, you will generally find that if you ask them about what they really know, they will answer with all sorts of things they would like to have the answers to or suspicions they would like to test further. If you ask someone who is new to the same field what they know, they will likely rattle off all of the things they've most recently learned and conclusions they've drawn from it.
Can you say horse sh!T. Noah K, Rythmik, Mark, and Bosso you guys are what's wrong with the world. I am sorry but you deserve no respect because you have spent a lifetime doing this. Nor does it mean you are above anyone else. You arses sound like golfers when T. Woods showed up.
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What's weak is your insistence that you have the best answer for the best subwoofer.
This is some of the weakest crap I have ever read. Every one of you push your own favorite designs down everyone elses throat, what is the difference? Lord knows I'm tired of reading about servos in post regardless of the OT, of $3000 multiple sealed set ups in cheap DIY threads. I'm sorry you were around for years before you came up with anything on your own, get over it.
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With all due respect to the proponents of a given design, who would praise the performance of a commercial sub before it's been tested?
SC isn't making commercial subs, he isn't even selling plans, or doing it on the side. Now lets see which of you do...

Do any of you have anything better for under $650 (driver, box, amp, everything), for someone who has the space for some thing this big? Is LLT the "be all end all' solution to perfect bass? No. That doesn't mean it isn't any good.

If you find something he types is in error correct it, that will help everyone learn something.

Rant over.
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post #209 of 919 Old 07-27-2006, 06:58 AM
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Ed Mullen, you just went up a few points in my book.
He has always been at the top of my list. Nothing but pure logic and reason imo.

My own conclusion is Craig has some leeway and would be hard pressed to go wrong.

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post #210 of 919 Old 07-27-2006, 07:01 AM
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Quote:
Originally Posted by Mark
The problem is more a matter of perspective. If you talk with someone well practiced in any field, particularly outside of audio, you will generally find that if you ask them about what they really know, they will answer with all sorts of things they would like to have the answers to or suspicions they would like to test further. If you ask someone who is new to the same field what they know, they will likely rattle off all of the things they've most recently learned and conclusions they've drawn from it. There is that particular crest of realizing just how much more there is to be explored or confirmed. Suspicions and expectations are very different from confirmed or proven facts.
That's a fair point Mark, but at the same time, for at least a few years prior to this recent LLT surge, how many subs using this type of design were there around in the DIY area? I joined this forum in '04, but have probably lurked here, HTF, and at other forums with a DIY section since '02, and in that time, the concept of a LLT subwoofer was miniscule to nonexistant (I realize my exposure to DIY wasn't all encompassing). There were a few EBS systems I had seen, but few if any capitalized on some of the minimum requirements I would consider for a LLT. Joe L's is one design that sticks out in my mind, as his was the one that sparked the interest in my mind about what such a design could offer, and his was the closest that came to it. In terms of drivers, correct me if I am wrong, but aside from Adire's top of the line stuff (and I don't know how far back Adire goes), were there even drivers well suited to this application prior to 2002 like there are now? What I'm getting at is that while I'm probably coming off as a cocky punk kid who thinks he has found all the answers in a short period of time and has developed the end all be all design - which I assure you is not the case - I'm just not aware of any previous work or experience with a type of design that adheres to these qualifications. Now the theory seems pretty solid, and all who have built one - many of whom have gone from sealed to LLT, and I'm not just talking about Steve nn - seem to be very impressed with what this type of design brings to the table, and prefer it to their sealed sub. They note the articulate mid to upper bass, the deep and effortless low end, and note a general sense of authority it has. I've heard no complaints about port noises or resonances, no complaints of bottoming or driver farting sounds, and no complaints about the sound quality. It seems as if the theoretical side is holding true. Honestly, I think it is something to get excited about.

Quote:
Can you state with any certainty that there aren't other problems that can creep in the operation of a large port? Does the sharpness of the corner and relative damping have any effect in operation and listening?
You've previously mentioned a large port in a low tuned enclosure probably will not offer all of the output shown in the simulations. Even if that is the case, based on my and other owner's FR measurements, I haven't found any lack of low end. But no, I can't state with certainty there aren't other problems that may creep into the scene. If there are any, I would have to assume they aren't very offensive.

Quote:
Are you certain that resonances above the low pass filter won't be audible? Do the enclosure and vent size have any relation to the amplitude of those port resonances? What does affect those port resonances? Is there some specific point at which they become audible?
I am not aware of what minimum frequency the first port resonance can dip to to be considered "in the clear". With the first few designs, I recommended it be 240hz or higher, just to be safe, as I figured at two octaves higher than the crossover frequency, there shouldn't be any problems. With different drivers, optimal enclosure sizes were much smaller than my Avalanche sub, and the port lengths were going to have to be longer. As new designs were developed, the first port resonance would get slightly lower and lower, getting away from my 240hz safety limit, I'd ask the owners if they noticed any type of resonant tone coming from their ports, and they all said no, and I became more comfortable with lower limits. Steve's sub pushed that resonant frequency the lowest yet, to ~189hz - I was a bit concerned and I made mention of that to him. But as it stands, he is not noticing any problems with it, and at this stage in the process, I now use a minimum of 180hz as a safety limit. I don't know how much lower we can go, but I don't see any need to go any lower than that. Sure, it was an experimentation process, but to this day, I can't find any safe minimum frequency data - in fact, this very question is in a recent post at htguide.com, and still, nobody has a definite answer. As far as I know, the main factor that affects this resonance point is the length of the port - whether in 100 or 1000 liters, or whether using a 10" or 6" diameter port, it's length of the port that counts for this issue.

Quote:
What happens with large, long dimensions inside an enclosure? Do they always or never pose a problem?
There is the potential to get standing waves in the enclosure and group delay is increased around the tuning point. Some will describe the highly damped sound as dead - I prefer accurate.

Quote:
How do we know the perceptions are due to tuning frequency vs. frequency response or other resultant changes?
Well they kind of go hand in hand, wouldn't you say? The lower tune results in certain changes in performance.

Quote:
Originally Posted by Rythmic
How about quarter wave length resonance of the port? That is really difficult to deal with. Without solving the problem to a satisfactory degree, the vented box is still not the same as sealed box, no matter how low you tune the vented box.
Could you explain further please? It won't mimic a sealed subwoofer 100% exactly, as it's not a sealed subwoofer, but the driver is behaving very similarly prior to any air compliance effects, no?

Quote:
I am pretty sure the audience would ask "Is it possible that you can lose the advantage of the vented box and sealed box at the same time, instead of getting them?"
Hmmm, are you suggesting that is the case?

Quote:
Originally Posted by noah katz
What's weak is your insistence that you have the best answer for the best subwoofer.
Well there is no "best" subwoofer, as everyone has different needs. But if you define your bass performance as a combination of the usual factors - FR, max output (compression), THD, group delay, and sound quality, as a whole, I think this design gives you more for your dollar than a traditional ported or sealed. Now something like an even larger bass horn, transmission line, or some other exotic design with the same driver may do those even better as a whole, I don't know, I'm not very familiar with how they operate.

Quote:
There's nothing an LLT can do that a sealed system can't do better,by ratcheting up the overkill a moderate amount beyond what you espouse.
Sure, but not on a dollar to dollar or driver to driver basis. I think it's safe to say for most DIYers, at least from what I've seen, that they are more willing and able to go with a larger design to get their desired level of performance than they are to go with a much more expensive or complex design.

Quote:
Originally Posted by Ed Mullen
This post is not back-pedaling in the least, but I do want to acknowledge that Steve Callas has made a solid case for his subwoofer design of choice
Quote:
There is nothing to suggest that this design will be anything but an excellent performer by any normal criteria and standards
Thanks Ed, I appreciate the support and the real world, common sense approach.
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