Purpose of flat response below 20Hz - Why does it matter? - Page 10 - AVS Forum
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post #271 of 585 Old 07-22-2011, 06:31 PM
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Originally Posted by floridapoolboy View Post

I read something once about "the brown note", is that what you are referring to?

Not sure. I do recall seeing studies that different organs in our bodies, and that includes our eyes their own unique and overlapping resonant frequencies. Also certain frquency ranges are known to evoke specific emotional responses. The old composers like Brahms, Beethoven, Mozart, and others knew it especially when they were commissioned to create works for the Church. Take for example the theme song in the movie Titanic by Celine Dion. Whether intentional or not, it evokes a sense of spirituality in many who hear it. So I do wonder with all this low frequency stuff that Bosso and others have demonstrated exists if it's an attempt to tap into other emotional responses.

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post #272 of 585 Old 07-22-2011, 07:04 PM
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Well, the brown note might evoke an emotional response in a few...

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post #273 of 585 Old 07-22-2011, 07:19 PM
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LMAO...Can't believe this thread is still going....

Too many so called "scientists" on here.
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post #274 of 585 Old 07-22-2011, 07:40 PM
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Originally Posted by Chu Gai View Post

Just wondering here, Bosso. Medical science knows that various organs in the body have certain resonant frequencies (low) and sundry studies have indicated correlations with frequencies and perceived sensations (paranormal comes to mind but there are others). In your opinion, do you think the reason for the presence of low level information in movies is an attempt to tap into these perceptions?

From an article I read back a ways (sorry, lost the link):

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Infrasound has been known to cause feelings of awe or fear in humans. Since it is not consciously perceived, it can make people feel vaguely that supernatural events are taking place. Truth be told, some Movie soundtracks make use of infrasound to produce unease or disorientation in the audience

Ping MKT. He hipped me to The New Daughter and I Spec-Graphed a scene for him. Had a long ULF multi-tone drone in a scene. Def for tension, IMO.

I know this; back in the beginning, around 10 years back, I used a 1/12 octave sine tone CD and the RS meter with correction file for making graphs by hand. The tones began at 10 Hz. I could see the driver moving, but heard no sound and the first few times I ignored it as insignificant, as I'd never experienced freqs below hearing. But, I still let the disc play from the beginning for each graph.

About the 3rd day of changing EQ and making a graph many times over, I became rather nauseous and disoriented and it lasted for quite some time.

Thank goodness for sine sweeps, REW and a mic that requires no cal file..

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post #275 of 585 Old 07-24-2011, 04:52 AM
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Originally Posted by bossobass View Post

A higher sensitivity driver equals a lower sensitivity <20 Hz.

Excuse me? I know you're smarter than that.

The efficiency of the driver has basically nothing to do with sensitivity below 20Hz. The cabinet volume sets the efficiency down low. Take a 99dB/W/m driver and an 83dB/W/m driver of the same volume displacement, put them in the same sized box, and you'll get the same sensitivity at 20Hz.

Now, if you're talking about different alignments that trade bandwidth for efficiency (vented, TH, etc.) that's a different argument. But one the words you actually wrote did not make. The words you actually wrote are simply incorrect on fact.

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Originally Posted by bossobass View Post

When I say people are preferring that choice currently, I don't mean to say that they're doing so from an understanding of transient response vs dynamic tracking of transients.

Well, then please explain what exactly you were saying when you said I specifically was conflating low inductance for dynamic tracking, because so far all you've written in that area is demonstrably wrong and/or an incoherent mess;

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Originally Posted by bossobass View Post

I've said many times and posted the evidence to back it that a flat, full BW FR equals a) better accuracy (reproducing what's on the disc vs not doing so really comes under 'duh'), b) a better listening experience.

Incorrect on both counts.

For instance, let's take that 13Hz signal on the Sting track you mentioned. That's interestingly close to the 14Hz kwarmy noted on some spoken word.

So tell us, is that simply an artifact from close-micing a vocal track? If not, how does it actually relate to the music? That is to say, what musical instrument produced that tone?

Given that you have absolutely refused to answer that simple question, one has to conclude that ULF is content is either (a) simply a mistake that slipped through, or (b) actually deleterious to the musical performance.

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Originally Posted by bossobass View Post

Yes, we are in agreement on many aspects of the low end of things. The difference is that I have 2-1/2 octaves more BW and lots more headroom, which equates to a more accurate system.

Why must you personalize the discussion? It's just not relevant.

What's actually relevant to this thread is the following general two-step inquiry:
(a) is extreme ULF (<16Hz fundamental) present in recordings of musical performances. Not special effects, where we all concede they're there, and that given the ability of "best bass" disks to move product probably intentionally at this point even if the first ones were mere accidents, but musical performances; and
(b) if the answer to (a) is "yes," then are those signals, first, intentional, and second, perceptually relevant?

Nothing else but the answer to those two questions matters.

In the case of one track, you have answered (a) affirmatively, but (a) is just the threshold requirement to get to (b), the more important inquiry.

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Originally Posted by bossobass View Post

The subjective difference is irrelevant.

No, it's not. Arguably, it's the only thing.

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Originally Posted by bossobass View Post

Debating the validity of non-filtered recorded source is irrelevant.

No, it's not. The recording process produces artifacts that are not part of the original performance. Such as 14Hz tones coming from a spoken-word track. Is your argument really that a 14Hz signal from someone speaking is not spurious, simply because it happened to end up on the disk?

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Originally Posted by bossobass View Post

It's not that I haven't presented a shred of evidence. It's that you've decided to shred the evidence I've presented.

Yes, because what hasn't been incomplete to address the relevant inquiry has simply been irrelevant. Or, as in the case of the statement with which you started the post I'm currently quoting ("A higher sensitivity driver equals a lower sensitivity <20 Hz") simply incorrect on fact.

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Originally Posted by bossobass View Post

In the real world, all transients have content to DC. In the real world of recorded source, there is intended content to <3 Hz. If your playback system rolls off at 20 Hz, an audible form of distortion exists.

Of course, all transients have content to light as well. So if a system can't produce rolls off top top before the terahertz range, an audible form of distortion exists as well. Like your above-quoted statement, mine is equally true, and equally irrelevant to the reproduction of music.

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post #276 of 585 Old 07-24-2011, 07:57 AM
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Originally Posted by DS-21 View Post

Given that modern best practices (i.e. the methods and procedures that provide the overall smoothest response in small rooms)...

"Best Practices"??? What are "best practices" as they refer to subwoofer system integration. I see you use this "catch-phrase" all over the forum, and I have no idea what it means. In your little world, the only "best practices" are the Geddes procedures, with random, multi-subwoofer placement with no Bass Management. In those "best practices", FR management is the only goal. System headroom, max SPL and ULF extension are not even considerations.

There can be no rigidly defined "best practice" for subwoofer(s) system integration. Every ROOM, speaker system, Bass Management system, subwoofer(s) system and, (did I say), ROOM!!! is different and each one requires a custom solution for optimization of the bass response. More importantly, subwoofer optimization is dependent on the expectations and goals of the optimizer. One optimizer might only want 20 or 25 Hz extension, (YOU), while others might want flat response to single digits, (me, and many others.) Some might only want 100 dB max output while others might want 125 or more dB. Some might have smaller satellite speakers with limited LF extension while others might have large towers with extension into the subwoofer regions. Some might have the ability to place bass traps optimally around the room while others not so much. Some might want optimization of a single listening position while others might want a large listening area optimized. Some elitists might only value music reproduction while others might value accurate reproduction of Hollywood's "bass spectaculars", (check the "Master List of Bass in Movies" thread if you don't believe me.)

All these different design goals require different strategies for subwoofer optimization. There is no single "best practice", not even Geddes procedure, that encompasses all the different rooms, systems and goals, so get over yourself with this nonsense.

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post #277 of 585 Old 07-24-2011, 08:40 AM
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Originally Posted by craig john View Post

"Best Practices"??? What are "best practices" as they refer to subwoofer system integration.

The methods that have been shown to provide:
(a) the smoothest upper bass frequency response in a small room, and
(b) the least seat-to-seat variance in the listening area, as the listening area is defined by the user (who can, of course, choose the area over which s/he will take spatially-averaged measurements, never single-point always spatially-averaged if one cares about getting good data), with the caveat that said listening area must be reasonable. For example, trying to optimize for seating in the middle of a room and seating on the back wall is likely to result for bad overall sound, because the defined listening area is simply unreasonable.

Today, that means one of three options:
(a) Geddes if one's doing things manually in most domestic living rooms; or
(b) double-bass-array if one's room fits in a very narrow and specific geometry, one can place subwoofers appropriately, and one is willing to add some extra volume displacement to make up for the lost boundary-loading advantages; or
(c) Sound Field Management (Toole/Welti/etc.) if one wants a good automated approach and is willing to pay for the appropriate gear (JBL BassQ or Synthesis)

Tomorrow, someone may introduce a method that's easier to do and/or higher-performing and/or cheaper to implement. But we are where we are today.

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Originally Posted by craig john View Post

I see you use this "catch-phrase" all over the forum, and I have no idea what it means.

I am not to be held responsible for your puzzling inability to look up "best practices" on google and/or wikipedia and learn what the term means if you are unable to derive the meaning from context.

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Originally Posted by craig john View Post

[pointless ad hominem attack deleted]***the only "best practices" are the Geddes procedures, with random, multi-subwoofer placement with no Bass Management.

Actually, see supra.

The fact that those three methods (Geddes, DBA, SFM) use different techniques but seem to end up with the same measurably and audibly superior result speaks well for all three methods. The fact that other methods do not compare speaks comparatively poorly about them.

(As for "bass management," It's not at all incompatible with the general setup procedure outlined by Geddes. Regardless of setup procedure, "bass management" is just a crutch for people who can't/won't use mains with closed boxes to limit excursion and sufficient volume displacement to act as viable sources in the modal region. Most systems composed of the small, inefficient mains typically marketed to home audio will require that crutch, my current one as discussed in the "modest multisub" thread included. The best systems will not. Interestingly and as an aside, with multisubs properly set up it seems that the frequency threshold for localization is higher compared to lesser setups. Whereas in a setup a single corner sub crossed over at 90Hz may at times make its presence known, with a multisub setup using that same corner sub does not have localization issues even with a 2d order electrical - and acoustical, more-or-less - crossover between mains and sub at 120Hz. Indeed, with these speakers and subs in this room, at 200Hz the localization issues with multisubs were about as bad as they were with the single corner sub crossed at 90Hz. That, I think, has interesting implications for mains design/specification.)

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Originally Posted by craig john View Post

In those "best practices", FR management is the only goal. System headroom, max SPL and ULF extension are not even considerations.

That is correct. System headroom, SPL, and ULF extension should not be considerations in the set up phase, which is what the Geddes method, DBA, SFM are about. If one must futz with setup to obtain the desired SPL or extension, then the system was badly designed/specified from the start.

Headroom/SPL and LF cutoff are, rather, design phase considerations. One can only reach the desired SPL and LF cutoff one seeks by selecting subwoofers of appropriate volume displacement and bandwidth* and obtaining the required amplifier power and signal processing to meet those goals.

*Low inductance is required to meet the upper-bass bandwidth. If one is using subs that unload below tuning (vented/PR, >4th order bandpass), the subs' native tuning also matters, because the subs won't pressurize the room below tuning. With sealed and 4th-order bandpass subs, native LF cutoff is irrelevant because any well-designed system will include processing to tailor the low end response to taste, be it the one-trick pony "Bassis" that Bosso likes or a more flexible box with parametric EQ and/or shelf filters.

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Originally Posted by craig john View Post

There can be no rigidly defined "best practice" for subwoofer(s) system integration.

That depends, of course, on one's definition of "rigidly defined."

If you think that term fits the following:
specifying subwoofers adequate volume displacement, power, and signal processing to meet one's goals (the system design phase), and then fitting them in the room where you realistically can, and setting them to optimize upper-bass frequency response (the system setup set-up phase),
then I simply disagree with your definition of "rigidly defined."

It seems, to my mind, rather a flexible process.

And, as you know, I've done it several times, with a wide variety of gear but one constant: superior results. And that's not because I have any great competency or much better equipment.

Most goals are met (or fail to be met) in the design phase, assuming some intellectual rigor was used in setting realistic goals (per one's budget, aesthetic tolerances, etc.). One can roughly estimate the volume displacement required for a given output and LF cutoff in a room of a given volume. (With in-room measurements of previous systems, knowing their theoretical abilities, one can have less of a fudge factor in those estimations.)

The iterative set-up process then optimizes the system along the only major variable that cannot be accounted for in the design phase: the response of that system in the modal region of that room.

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Originally Posted by craig john View Post

More importantly, subwoofer optimization is dependent on the expectations and goals of the optimizer.

Unless you're arguing that the optimizer may have low expectations as to sub-mains integration and flatness of response in the modal region, how is that even the very slightest bit inconsistent with anything I've written?

Again, LF cutoff and SPL are design phase considerations, not setup phase considerations. If one must kludge the setup to make up for lack of rigor or faulty assumptions in the design phase, that's not the fault of the setup method but rather of the system designer.

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Originally Posted by craig john View Post

Some might have the ability to place bass traps optimally around the room while others not so much.

That raises the question of what value "bass traps" have. I don't think they have much. As you've seen, I routinely achieve excellent performance without even considering such eyesores.

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Originally Posted by craig john View Post

All these different design goals require different strategies for subwoofer optimization. There is no single "best practice", not even Geddes procedure, that encompasses all the different rooms, systems and goals

Based on what you've written, you seem to hold that position primarily because you don't understand my arguments. Perhaps that is my fault, because I have written with insufficient clarity. Hopefully now you understand them better.

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post #278 of 585 Old 07-24-2011, 09:17 AM
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Yeah, everyone regularly uses an 83dB 1W/1M driver. Please stop rambling and post a real example. Where's this 99dB driver? Show the details so we can see what you're trying to say here. Why do you insist on talking to me like it's my first day?

Lower Fs = lower sensitivity = lower F3 in a sealed box. Higher sensitivity = higher FS = higher F3. Lower F3 = higher sensitivity below 30 Hz. Higher F3 = lower sensitivity below 30 Hz. Sealed box 101.

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Originally Posted by DS-21 View Post

Around 0.5mH if memory serves. (The new Parallels doesn't seem to work right now, so I can't check it against my Unibox database.)

But basically, lower than anything else with the same volume displacement. An underhung (i.e. short) single-layer coil and copper sleeve on the motor will do that.

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Originally Posted by DS-21 View Post

Believe it or not, Penn, you're not the only person to have owned several different models of subwoofers.

But as to your second comment, it depends on the bandwidth. If you're talking below 30Hz, sure, they're all airpumps. They'll all work fine. All that matters there is how much air each can pump. Well, that and power compression, which suggests get the largest-diameter voicecoil with the best possible cooling system.

But play 'em much higher and the story changes. You can't just EQ out the effects of that sky-high inductance, sorry.

Something with large volume displacement, linear motor and suspension, and low inductance.

Of currently-available drivers, I submit the Aura NS18 and B&C 21SW150 (I think that's the model) are tops. TC's LMS and Aura-knockoff lines are up there well, if one wants to roll the dice on TC's build quality.

Fake crashes, explosions, and the like are rather different from, say, reproducing a tympani roll recorded live. There's no real event to reference, so it's not about accuracy but believability. That is to say, does it sound like what you think a crash or explosion in that place might plausibly sound like?

Nonsense. It means wide bandwidth, low distortion, and high output. Not only one or two of those things.

And severe bandwidth-limiting compared to a good driver.

REAL DATA:



How about 87.3dB 1W/1M vs 97.4dB 1W/1M?

The CSS SDX-15 has inductance of 1.8mh. A pair of them at 87.3dB 1W/1M has higher sensitivity below 30 Hz than a PAIR of B&C 21" drivers at 97.4dB 1W/1M. The B&C pair has the LOWEST sensitivity below 20 Hz of any system Josh has tested.

I don't see this severe BW limit you refer to. In fact, I do know better. It's pure hogwash.

It's also interesting that you believe "you can't just EQ out the effects of that sky-high inductance, sorry", but at the same time, "F3 is irrelevant. You can EQ the FR to taste".

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Originally Posted by DS-21 View Post


F3 is irrelevant. It could be 70 Hz and still be the foundation of a great sub! What matters is volume displacement. With enough volume displacement, you can EQ the frequency response to taste.

F3 is irrelevant? EQ the FR to include subwoofer BW with the B&C sub and you lose the top end sensitivity, whether you use a shelf or L/T.

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Originally Posted by DS-21 View Post

By contrast, the Fi Q-series just another excessively long coil driver with no shorting rings in the motor. Note that Fi doesn't even specify the inductance of the Q18. What you'll see from one is roughly what Josh got from the eD sub: plenty of output, at the expense of fidelity due to the high inductance.

Challenge: You build a system with your Aura 18 and I'll build a system with 2x18 Fi Q (price difference gives you 2 for 1 Q vs Aura). We''ll submit them to Josh and start a thread discussing the actual facts of the matter. Let's make it fun and educational vs this sort of childish exchange, eh?

If subjective opinions of <20 Hz content "... is the ONLY thing", I would suggest you're waaaaay behind the curve in answering that for yourself, as no one can tell you what anything means to you subjectively, so stop asking the silly question of others and then blindly arguing that they're wrong.

"You're wrong", is no argument. In fact, once you've said that, what's next, "you're really, really wrong"? Prove it's artifact. Prove it has no subjective significance.

For the record, this sort of banter is tiresome for me. You're never gonna convince me that black is really white and I would have left the thread a while back because what you believe regarding an area you have no experience with holds no interest for me. The only reason I post to point out your mistaken views is because I get PMs from folks who won't post because of your bully style of putting the other guy down to elevate yourself.

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post #279 of 585 Old 07-24-2011, 09:51 AM
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Originally Posted by bossobass View Post

Yeah, everyone regularly uses an 83dB 1W/1M driver.

There are certainly 83dB/W/m drivers used as subwoofers. The Eclipse LMT8200 (a 12 with 30+ mm of xmax with TC's LMT coil) is an example of one.

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Originally Posted by bossobass View Post

Show the details so we can see what you're trying to say here. Why do you insist on talking to me like it's my first day?

Because you're writing as if it's your first day. I know you know better, but you seem to just want to pick a fight. Which is fine, so long as readers aren't misled by incorrect information.

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Originally Posted by bossobass View Post

Lower Fs = lower sensitivity = lower F3 in a sealed box. Higher sensitivity = higher FS = higher F3 [in a sealed box].

Correct.

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Originally Posted by bossobass View Post

Lower F3 = higher sensitivity below 30 Hz. Higher F3 = lower sensitivity below 30 Hz. Sealed box 101.

Incorrect, unless you're talking about relative sensitivity.

In terms of absolute sensitivity, box size is what matters. A driver that's 99dB/W/m at 1kHz will have the same sensitivity at 20Hz as a driver that's 83dB/W/m at 1kHz. The former will just have rolled off more from its reference sensitivity than the latter. Hoffmann's Iron Law 101.

If F3 was truly that important, you wouldn't be using "undersized" boxes with a Linkwitz Transform. You'd be using Qtc=0.707 boxes, as they have the lowest F3. And you'd be massing the hell out of your subwoofer cones, to lower efficiency and thus F3. But you don't, do you? Yet, because you seem to be in attack dog mode, that is the very approach you're currently attacking.

Quote:



Think for a moment about what those data show, and how it doesn't relate to my point in the slightest. Is box size held constant? If so, is volume displacement the same?

Given that I'm arguing the correct position, that box size determines low end efficiency, data where box size is not held constant just shows you didn't understand the argument to which you were replying.

Again, it's Hoffmann's Iron Law 101.

And a graph of maximum output has absolutely nothing to do with sensitivity. THAT's just Reading Graph Labels 101.

Look at both drive-units, in the same sized box, with a given constant level of drive. 2.83V is the standard, but I don't see why it matters what the actual level is so long as it's not so high as to fry the coils, or so low as to be lost in the measurement's noise floor. That will tell you the sensitivity, and that they are in fact the same sensitivity down low despite the B&C driver's considerably higher broadband sensitivity.

Maximum output, obviously, is a function of volume displacement and not of sensitivity unless the system is amp-limited. Obviously, ultimately volume displacement of a subwoofer can be amp limited. But that's not particularly relevant here, because to reduce amp limiting one needs more power and/or a bigger box with either driver.

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Originally Posted by bossobass View Post

The CSS SDX-15 has inductance of 1.8mh.

What's your point? Are you saying that fits my rubic of "sky-high?" If so, you're just willfully misinterpreting what has been so clearly spelled out. Inductance on its own is meaningless. Inductance must be considered along with resistance. What's the Re of the SDX-15? According to their spec sheet, 3.6Ω. So the normalized Le is in fact about 0.5mH/Ω. That's reasonable, considering the coil is relatively short for the throw (XBL^2) and it uses shorting rings. And 0.5mH/Ω is pretty darned low, no?

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Originally Posted by bossobass View Post

It's also interesting that you believe "you can't just EQ out the effects of that sky-high inductance, sorry", but at the same time, "F3 is irrelevant. You can EQ the FR to taste".

There is no inconsistency there to a thoughtful person.

And, it's worth noting, I'm making the exact same argument you've made for years: EQ the F3 to your desired low-end cutoff (you specify a Linkwitz Transform, whereas I would use a combination of parametric EQ and shelf filters, guided in my approach by in-room measurements of those subwoofers in that room, but that's a detail difference) and use enough subs/amp to get the headroom you want.

You seem to have such distaste for my words that they're causing you to reject your own long-held positions and argue against them. How many times have you written that it's good practice to take advantage of the high-Q efficiency bump and then EQ the low end? Have you fundamentally changed your mind about that? If so, why?

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Originally Posted by bossobass View Post

F3 is irrelevant? EQ the FR to include subwoofer BW with the B&C sub and you lose the top end sensitivity, whether you use a shelf or L/T.

In practice, what does that mean though? Neither the driver or the amp is working that hard. Sounds fine to me.

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Originally Posted by bossobass View Post

Challenge: You build a system with your Aura 18 and I'll build a system with 2x18 Fi Q (price difference gives you 2 for 1 Q vs Aura).

I have better things to do with my time than to "prove" something obvious to anyone capable of applying human thought.

Especially given that you seem to be manufacturing disagreement even where there is in fact none. What I am posting is entirely consistent with your past posts and your past and present practice, but you're just trying to make noise for some reason.

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Originally Posted by bossobass View Post

"You're wrong", is no argument. In fact, once you've said that, what's next, "you're really, really wrong"? Prove it's artifact. Prove it has no subjective significance.

As you know, I can't currently reproduce that content. You can, yet you have no interest in asserting even its relevance, only its presence. That speaks plenty to people intellectually equipped to draw reasonable inferences.

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post #280 of 585 Old 07-24-2011, 12:13 PM
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Originally Posted by DS-21 View Post

There are certainly 83dB/W/m drivers used as subwoofers. The Eclipse LMT8200 (a 12 with 30+ mm of xmax with TC's LMT coil) is an example of one.

Great. Now, post the 99dB 12" driver specs and we'll do the comparison.

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Originally Posted by DS-21 View Post

Because you're writing as if it's your first day. I know you know better, but you seem to just want to pick a fight. Which is fine, so long as readers aren't misled by incorrect information.

This post has no point. Post the 99dB 12" driver specs and we'll have something to discuss.

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Originally Posted by DS-21 View Post

Incorrect, unless you're talking about relative sensitivity.

There is only relative sensitivity.

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Originally Posted by DS-21 View Post

In terms of absolute sensitivity, box size is what matters. A driver that's 99dB/W/m at 1kHz will have the same sensitivity at 20Hz as a driver that's 83dB/W/m at 1kHz. The former will just have rolled off more from its reference sensitivity than the latter. Hoffmann's Iron Law 101.

Show examples. This is another grossly incorrect generalization that has nothing to do with HIL.

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Originally Posted by DS-21 View Post

If F3 was truly that important, you wouldn't be using "undersized" boxes with a Linkwitz Transform. You'd be using Qtc=0.707 boxes, as they have the lowest F3. And you'd be massing the hell out of your subwoofer cones, to lower efficiency and thus F3. But you don't, do you? Yet, because you seem to be in attack dog mode, that is the very approach you're currently attacking.

Box size doesn't change a drivers parameters. Try to stick with your argument in stead of hiding behind one straw man after the other. Also, instead of telling me what I've done, try asking me. Who says my boxes are undersized? You? What size are they? What drivers are in them?

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Originally Posted by DS-21 View Post

Think for a moment about what those data show, and how it doesn't relate to my point in the slightest. Is box size held constant? If so, is volume displacement the same?

Given that I'm arguing the correct position, that box size determines low end efficiency, data where box size is not held constant just shows you didn't understand the argument to which you were replying.

Wow. Box size won't change the point being made. Your .5mh Le 99.7dB driver has less sensitivity below 30 Hz than a pair of the 1.8mh [per driver] SDX-15 [3.6mh in series, so what does "sky-high" mean?]

Box size is determined by Cms/Vas. It's not arbitrary. Holding box size constant for different drivers is a ridiculous with no point. Grossly varying the required box size to alter Q slightly will alter sensitivity below the knee, but at the same time will limit output above the knee. This proves nothing relevant to the point being debated.

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Originally Posted by DS-21 View Post

And a graph of maximum output has absolutely nothing to do with sensitivity. THAT's just Reading Graph Labels 101.

Of course it does. Read the graphs again, please. There's a nearly 1 to 1 correlation.

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Originally Posted by DS-21 View Post

Look at both drive-units, in the same sized box, with a given constant level of drive. 2.83V is the standard, but I don't see why it matters what the actual level is so long as it's not so high as to fry the coils, or so low as to be lost in the measurement's noise floor. That will tell you the sensitivity, and that they are in fact the same sensitivity down low despite the B&C driver's considerably higher broadband sensitivity.

There are 3 drivers on the graphs. Box size has been addressed. The rest of the post makes no sense.

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Originally Posted by DS-21 View Post

Maximum output, obviously, is a function of volume displacement and not of sensitivity unless the system is amp-limited. Obviously, ultimately volume displacement of a subwoofer can be amp limited. But that's not particularly relevant here, because to reduce amp limiting one needs more power and/or a bigger box with either driver.

You said F3 is irrelevant because you can EQ to taste. I said most every sub available is amp limited. The 2 are directly related. It's inductance and 1W/1M specs that are irrelevant here, which is the point I've been trying to make.

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What's your point? Are you saying that fits my rubic of "sky-high?" If so, you're just willfully misinterpreting what has been so clearly spelled out. Inductance on its own is meaningless. Inductance must be considered along with resistance. What's the Re of the SDX-15? According to their spec sheet, 3.6Ω. So the normalized Le is in fact about 0.5mH/Ω. That's reasonable, considering the coil is relatively short for the throw (XBL^2) and it uses shorting rings. And 0.5mH/Ω is pretty darned low, no?

No, I'm asking you to specifically detail this non-existent Le requirement. Sky-High is your term. Put numbers to the assertion and show proof of their relevance.

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Originally Posted by DS-21 View Post

There is no inconsistency there to a thoughtful person.

Then I have to assume you just don't read your own posts.

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Originally Posted by DS-21 View Post

And, it's worth noting, I'm making the exact same argument you've made for years: EQ the F3 to your desired low-end cutoff (you specify a Linkwitz Transform, whereas I would use a combination of parametric EQ and shelf filters, guided in my approach by in-room measurements of those subwoofers in that room, but that's a detail difference) and use enough subs/amp to get the headroom you want.

I've never said or agreed with no shorting rings = low fidelity. I've never said ULF content in recordings is unintended artifact. I've never said ULF is subjectively irrelevant. I've never disparaged Fi products as inferior and not worthy of attempting to use in a subwoofer build. I've never favorably compared the Dayton Ref driver to a Fi Q as a superior product, nor would I with a straight face. I've never said the Fi Q has unacceptably high Le, then in the same sentence admit I don't even know what its Le spec is.

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Originally Posted by DS-21 View Post

You seem to have such distaste for my words that they're causing you to reject your own long-held positions and argue against them. How many times have you written that it's good practice to take advantage of the high-Q efficiency bump and then EQ the low end? Have you fundamentally changed your mind about that? If so, why?

It's not my subwoofers we're discussing here. There are 3 things we're supposed to be discussing. The OT asks if a flat response to below 20 Hz matters. You've asserted that any driver without shorting rings is low fidelity. I've said that most every available subwoofer system is amplifier limited, which limits <20 Hz reproduction and squashes or clips transients.

To the first and main question, you've gone on and on about the lack of relevance, that it's artifact from sloppy production practices, that it only appears in source you consider garbage, etc. You've tried to defend this position by burdening others to prove it to you personally while posting nothing whatever to back your assertions.

To the second point, although Dolby, THX and everyone else in the MC audio world has standardized the LR4 LPF at 80 Hz, you assert that a subwoofer must be crossed over at 150-200 Hz to exhibit fidelity. Again, zero data to back your position, just disparaging remarks to those who try to point out the obvious, backed by an entire industry.

To the third point, a flat response at the LP with enough headroom to safely cover the 30dB peak-to-average seen regularly in quality soundtracks is what counts regarding accurate reproduction of source. It was again you who chose to argue against this point against your own previous assertions.

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In practice, what does that mean though? Neither the driver or the amp is working that hard. Sounds fine to me.

At max output <20 Hz, it's weakest link, and therefore it's headroom ceiling, it seems to be working quite hard to me, unless you prefer a grossly distorted FR linearity.

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Originally Posted by DS-21 View Post

I have better things to do with my time than to "prove" something obvious to anyone capable of applying human thought.

But you have unlimited time to ask others to do the very same thing.

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Originally Posted by DS-21 View Post

Especially given that you seem to be manufacturing disagreement even where there is in fact none. What I am posting is entirely consistent with your past posts and your past and present practice, but you're just trying to make noise for some reason.

Nice.

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Originally Posted by DS-21 View Post

As you know, I can't currently reproduce that content. You can, yet you have no interest in asserting even its relevance, only its presence. That speaks plenty to people intellectually equipped to draw reasonable inferences.

It's relevance is that a) it's on the disc, b) my system accurately reproduces it and c) if your system does not, there is an audible distortion in the presentation. How intellectually equipped does one have to be to get that?

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post #281 of 585 Old 07-24-2011, 02:21 PM
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Originally Posted by DS-21 View Post

The methods that have been shown to provide:
(a) the smoothest upper bass frequency response in a small room, and
(b) the least seat-to-seat variance in the listening area, as the listening area is defined by the user (who can, of course, choose the area over which s/he will take spatially-averaged measurements, never single-point always spatially-averaged if one cares about getting good data), with the caveat that said listening area must be reasonable. For example, trying to optimize for seating in the middle of a room and seating on the back wall is likely to result for bad overall sound, because the defined listening area is simply unreasonable.

Today, that means one of three options:
(a) Geddes if one's doing things manually in most domestic living rooms; or
(b) double-bass-array if one's room fits in a very narrow and specific geometry, one can place subwoofers appropriately, and one is willing to add some extra volume displacement to make up for the lost boundary-loading advantages; or
(c) Sound Field Management (Toole/Welti/etc.) if one wants a good automated approach and is willing to pay for the appropriate gear (JBL BassQ or Synthesis)

Tomorrow, someone may introduce a method that's easier to do and/or higher-performing and/or cheaper to implement. But we are where we are today.



I am not to be held responsible for your puzzling inability to look up "best practices" on google and/or wikipedia and learn what the term means if you are unable to derive the meaning from context.



Actually, see supra.

The fact that those three methods (Geddes, DBA, SFM) use different techniques but seem to end up with the same measurably and audibly superior result speaks well for all three methods. The fact that other methods do not compare speaks comparatively poorly about them.

(As for "bass management," It's not at all incompatible with the general setup procedure outlined by Geddes. Regardless of setup procedure, "bass management" is just a crutch for people who can't/won't use mains with closed boxes to limit excursion and sufficient volume displacement to act as viable sources in the modal region. Most systems composed of the small, inefficient mains typically marketed to home audio will require that crutch, my current one as discussed in the "modest multisub" thread included. The best systems will not. Interestingly and as an aside, with multisubs properly set up it seems that the frequency threshold for localization is higher compared to lesser setups. Whereas in a setup a single corner sub crossed over at 90Hz may at times make its presence known, with a multisub setup using that same corner sub does not have localization issues even with a 2d order electrical - and acoustical, more-or-less - crossover between mains and sub at 120Hz. Indeed, with these speakers and subs in this room, at 200Hz the localization issues with multisubs were about as bad as they were with the single corner sub crossed at 90Hz. That, I think, has interesting implications for mains design/specification.)



That is correct. System headroom, SPL, and ULF extension should not be considerations in the set up phase, which is what the Geddes method, DBA, SFM are about. If one must futz with setup to obtain the desired SPL or extension, then the system was badly designed/specified from the start.

Headroom/SPL and LF cutoff are, rather, design phase considerations. One can only reach the desired SPL and LF cutoff one seeks by selecting subwoofers of appropriate volume displacement and bandwidth* and obtaining the required amplifier power and signal processing to meet those goals.

*Low inductance is required to meet the upper-bass bandwidth. If one is using subs that unload below tuning (vented/PR, >4th order bandpass), the subs' native tuning also matters, because the subs won't pressurize the room below tuning. With sealed and 4th-order bandpass subs, native LF cutoff is irrelevant because any well-designed system will include processing to tailor the low end response to taste, be it the one-trick pony "Bassis" that Bosso likes or a more flexible box with parametric EQ and/or shelf filters.



That depends, of course, on one's definition of "rigidly defined."

If you think that term fits the following:
specifying subwoofers adequate volume displacement, power, and signal processing to meet one's goals (the system design phase), and then fitting them in the room where you realistically can, and setting them to optimize upper-bass frequency response (the system setup set-up phase),
then I simply disagree with your definition of "rigidly defined."

It seems, to my mind, rather a flexible process.

And, as you know, I've done it several times, with a wide variety of gear but one constant: superior results. And that's not because I have any great competency or much better equipment.

Most goals are met (or fail to be met) in the design phase, assuming some intellectual rigor was used in setting realistic goals (per one's budget, aesthetic tolerances, etc.). One can roughly estimate the volume displacement required for a given output and LF cutoff in a room of a given volume. (With in-room measurements of previous systems, knowing their theoretical abilities, one can have less of a fudge factor in those estimations.)

The iterative set-up process then optimizes the system along the only major variable that cannot be accounted for in the design phase: the response of that system in the modal region of that room.



Unless you're arguing that the optimizer may have low expectations as to sub-mains integration and flatness of response in the modal region, how is that even the very slightest bit inconsistent with anything I've written?

Again, LF cutoff and SPL are design phase considerations, not setup phase considerations. If one must kludge the setup to make up for lack of rigor or faulty assumptions in the design phase, that's not the fault of the setup method but rather of the system designer.



That raises the question of what value "bass traps" have. I don't think they have much. As you've seen, I routinely achieve excellent performance without even considering such eyesores.



Based on what you've written, you seem to hold that position primarily because you don't understand my arguments. Perhaps that is my fault, because I have written with insufficient clarity. Hopefully now you understand them better.

Your method for bringing about a smooth frequency response without using eq or room treatments works well at doing just that, but it introduces artifacts that are worse and are not really repairable. Having asymmetrically placed subs around the room will cause a smearing in the time domain. You are probably going to try to tell me that it can be corrected with the proper delays or phase settings to compensate for the distances, but it's not that simple. Delays can only align the sound that goes directly from the sub to your ears. Unfortunately, most of the sound in the bass range is reflected sound. That sound coming from several different places and distances and reflected differently off of different boundaries cannot be aligned and the result is smearing. What makes it much worse in your case is that you are smearing things well up into the upper bass (200hz?). That includes the fundamentals of voices and almost everything.

With multichannel sound, this smearing is not much of a problem in practice because there are properly many different originating sources of sounds anyway, but with two-channel stereo where symmetry rules, it's an unrepairable mess. Your technique is a perfect example of how you can have a flat frequency response, and still have unrealistic sound because of time related smearing and it's well up into the range that many of us consider lower midrange. You've introduced bigger problems than frequency response anomalies and they can't be fixed with eq. That can be reduced somewhat with room treatments, but you don't believe in those either.

You are focusing on a flat response but ignoring other factors that contribute to realism and are likely to be even more significant.
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If I remember DS-21's position on time domain issues (based upon posts here and here), and if I am mistaken I do apologize, is that they do not matter (in a nutshell). As evidence of their lack of import, I believe he has posited that several well know acoustical guru's, such as Gedes and Welti, did not measure these.

Obviously, others may disagree (myself included).

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Originally Posted by Snowmanick View Post
If I remember DS-21's position on time domain issues, and if I am mistaken I do apologize, is that they do not matter (in a nutshell). As evidence of their lack of import, I believe he has posited that several well know acoustical guru's, such as Gedes and Welti, did not measure these.

Obviously, others may disagree (myself included).
I don't consider it nearly as important with multichannel sound, but with two channel sound being properly played back in stereo, it is very important. It's importance also dramatically increases as you go up in frequency. At your typical 80hz, it doesn't matter all that much. Up at 200hz, you better believe it matters.
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There are many ways to get a flat response. Here is a response that uses no EQ, subs all in the front behind the screen, crossed over at 80hz into 2 speakers(mains). Who is to say which is higher fidelity? This one is raw with no smoothing so think how flat it would be 1/3rd smoothed. I purposely want that bump down low as this is the feel region.

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Here is any other of a different sub system with the same XO, 80hz, and speakers.

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post #286 of 585 Old 07-30-2011, 12:45 PM
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Quote:
Originally Posted by mojomike View Post

Your method for bringing about a smooth frequency response without using eq or room treatments works well at doing just that, but it introduces artifacts that are worse and are not really repairable.

No, it doesn't.

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Originally Posted by mojomike View Post

Having asymmetrically placed subs around the room will cause a smearing in the time domain.

In theory and practice, that is simply incorrect.

As for the theory, let's dispense with that first with Dr. Toole's words from Sound Reproduction. at 245.
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Originally Posted by Dr. Floyd Toole View Post

However, because we know that low-frequency room resonances generally behave in a minimum-phase manner, we know that if there are no prominent peaks protruding above the average spectrum level, there will not be prominent ringing in the time domain. It is this indirect, inferential knowledge that permits us to confidently use frequency responses as a primary source of information about room behavior at low frequencies.

As for practice, frankly, your argument is one only available to a person who simply has no relevant practice. That is to say, s/he has simply not experienced a properly set-up multisub system. Subjectively, I've found that a well set-up multisub system will sound firmly "locked" in time, far more so even than a stereo pair of full-range speakers, let alone a system using a single subwoofer crossed over in the modal region. Transients have more impact, the sonic image is more palpable, and the overall sound of the upper bass is just...natural. In a way that no stereo pair of monopole speakers (or speakers sitting atop subs, or single subs with a pair of monopoles, etc.) can be. (Dipoles can get close - the best 2-channel bass I've heard, including the Orions at AXPONA this year and a friend in Vienna's Audio Artistry Dvoraks, were from a pair of Gradient Revolutions) but have placement restrictions that make them untenable, at least for me. I suspect the same applies to cardoids.)

My experience is consistent with that of others who have tried it. (As well as high school buddies now playing in major symphony orchestras who have heard my system. One asked me to design a similar system for her - yes, her, the ULF stuff doesn't seem to appeal to anyone but a small subset of men, but more natural sound in the upper bass interestingly enough seems to appeal to everyone who loves music - after she heard it.) Look on the forums for subjective reports from people who have heard Dr. Geddes' home system. All comment on how natural the bass sounds. In fact, the only negative report of a multisub system I've heard has some from Penn, who simply did not (and still seems not to) understand the concept well enough to apply it with the slightest modicum of competence.

Not only that, but also experience listening to such a system will sensitize one to the wretched state of upper bass reproduction in most audio systems. IOW, the nasty bass response measurements one sees even from stellar "full range" stereo mains well set up by knowledgeable people are audible in practice, even if people without experience in high fidelity bass reproduction do not seem to notice.

And the fact of the matter is, in-room upper bass response for stereo pairs of loudspeakers in domestic living rooms is just tragically bad. (Measurements for systems using a single subwoofer are generally worse, because there is one one pressure source driving the room, as opposed to two.)

Here is the best in room measurement of a stereo pair of "full range" monopole-in-the-upper-bass loudspeakers I've ever seen.



The loudspeakers are Revel's Studio2, and they were measured for Stereophile by JA in Slate foreign affairs columnist Fred Kaplan's room. There is also an in-room measurement for a lesser speaker - Verity's nasty sounding $40k Parsifal - in the same room on that graph; The Revel is in red.

Note that from 30-120Hz there is about a 12-13dB swing. (The lesser speakers have about an 18dB swing over the same bandwidth; even that is better than most in-room measurements) Compare that with my various multisub setups' in-room measurements. Most people, because of both the relative inferiority of their speakers* and setup, will have much worse results than the Revels achieve in Dr. Kaplan's room!

For reference, here is the Revel's native frequency response, in the bass and elsewhere:



*Performance-wise, the Revels are basically unimpeachable. Also, I suspect the big Revel's combination of two bass drivers relatively high off the ground and a bottom-firing port with an EBS tuning frequency offers smoother in-room upper bass than would a single woofer of equivalent volume displacement placed near the floor.)

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Originally Posted by mojomike View Post

What makes it much worse in your case is that you are smearing things well up into the upper bass (200hz?). That includes the fundamentals of voices and almost everything.

Not really. I wouldn't use a 200Hz crossover to subs. Well, maybe Parham-style "flanking subs," were I to use them (and there are measurable benefits to doing so).

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Originally Posted by mojomike View Post

Your technique is a perfect example of how you can have a flat frequency response, and still have unrealistic sound because of time related smearing and it's well up into the range that many of us consider lower midrange.

Again, such things could only be written in the absence of practical experience with such a setup.

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Originally Posted by mojomike View Post

You are focusing on a flat response but ignoring other factors that contribute to realism and are likely to be even more significant.

You have the weight of basically the entire serious audio community against that assertion.]

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Originally Posted by MKtheater View Post

There are many ways to get a flat response. Here is a response that uses no EQ, subs all in the front behind the screen, crossed over at 80hz into 2 speakers(mains).

Is that a real measurement (i.e. a spatial average) or a cherry-picked single point?

If the former, impressive.

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Originally Posted by bossobass View Post

Great. Now, post the 99dB 12" driver specs and we'll do the comparison.

I don't know why you seem to be so adamantly opposed to the obvious physical reality that the volume of the cabinet sets the system's low end efficiency. Not the driver, the box.

Again, that's just Hoffman's Iron Law.

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Originally Posted by bossobass View Post

There is only relative sensitivity.

Simply incorrect on fact.

There is absolute sensitivity, i.e. x dB at y Hz at when driven with z V, and there is relative sensitivity, i.e. down m dB at n Hz re: p Hz.

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Originally Posted by bossobass View Post

Box size doesn't change a drivers parameters.

We agree on something, it seems.

Box size changes system parameters, however. Such as, for example, low end efficiency.

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Originally Posted by bossobass View Post

Wow. Box size won't change the point being made. Your .5mh Le 99.7dB driver has less sensitivity below 30 Hz than a pair of the 1.8mh [per driver] SDX-15 [3.6mh in series, so what does "sky-high" mean?

Obviously, drivers in different sized cabinets will have differing low end efficiency. Nothing new to anyone here, including you or me. So why are you arguing, again?

Also, you're simply not so daft as to not understand the notion of normalized Le, which is Le/Re. You just seem to be playing that way on this thread. I get the feeling that no matter what I write, you're going to say I'm wrong. I could write that speaker wires don't matter as long as they're a sufficient gauge, and you'll counter with "nonsense, you need High End cables that cost at least $500/ft to hear anything."

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Originally Posted by bossobass View Post

Box size is determined by Cms/Vas. It's not arbitrary.

Wait a minute. Are you claiming what I think you are, i.e. that there is a platonic ideal closed box?

I'd like you to elaborate on that point, because I've taken something quite different from your previous posts on the subject. Perhaps I've misinterpreted.

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Originally Posted by bossobass View Post

Holding box size constant for different drivers is a ridiculous with no point.

Hardly. In the real world people have space constraints, and may wish to see if a given driver will give them advantages in a given box volume. A driver that offers increased sensitivity in the top end of the subwoofer's bandwidth (120Hz, maybe as high as 150Hz) will be advantageous, if it still has sufficient volume displacement to reach the desired low end cutoff at a given SPL. The amp will have to work less hard in the upper bass that way, given that the system is more efficient up top and equally efficient (because ULF efficiency is set by the box size) down low.

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Originally Posted by bossobass View Post

Of course it does. Read the graphs again, please. There's a nearly 1 to 1 correlation.

I've read the graphs. They simply don't support your point.

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Originally Posted by bossobass View Post

You said F3 is irrelevant because you can EQ to taste. I said most every sub available is amp limited. The 2 are directly related.

Perhaps because I assumed that reasonable people would fill in the rest of my sentence. Since my assumption may have been unfounded, here's the rest of it.

"F3 is irrelevant because you can EQ to taste, within the limits of the volume displacement of the subs, which is limited by the drivers' excursion and/or the available power."

Obviously, for any LF cutoff at a given SPL, one needs first to have the volume displacement to get there, and the power to push the woofers to that volume displacement. Among reasonable enthusiasts, those points should be givens.

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Originally Posted by bossobass View Post

It's inductance and 1W/1M specs that are irrelevant here, which is the point I've been trying to make.

We agree that inductance is irrelevant to ULF performance, and also presumably also agree that it very much matters for upper-bass performance. Also, I presume we can agree that upper bass appears constantly in musical program material, so it makes sense to prioritize its reproduction over the reproduction of signal that appears sporadically at best. (And is of debatable perceptual relevance in the first place.)

We also now agree that 1W/1M specs are irrelevant in the low bass, apparently, though you claimed above that less efficiency was ipso facto better.

Hopefully, we also agree that the reason why is because the low-end efficiency of a closed-box subwoofer system is set by the trapped volume and not the driver.

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Originally Posted by bossobass View Post

I've never said or agreed with no shorting rings = low fidelity.

Yet, of course, in actual practice you prefer drivers with shorting rings and low inductance. Just as I do.

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Originally Posted by bossobass View Post

I've never said ULF content in recordings is unintended artifact.

Though you must concede that it can be, right?

Quote:
Originally Posted by bossobass View Post

I've never said ULF is subjectively irrelevant.

Obviously not. You're asserting the opposite, but aren't able to offer any evidence for that assertion other than the occasional mere presence of ULF. And even then, you've only given one example, outside of the program material we both agree contain ULF that in the current day is probably intentionally-placed and that some people may prefer to reproduce.

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Originally Posted by bossobass View Post

I've never disparaged Fi products as inferior and not worthy of attempting to use in a subwoofer build.

Nor have I, only that they are not worthy of use except in very limited circumstances, i.e. as ULF air pumps in systems with multisubs to cover the spectrum above their very limited bandwidth. The primary disadvantage of that approach is that one needs more subwoofers, because a ULF air pump cannot also act as a pressure source in the modal region without compromising the whole system. An advantage is that despite that requirement it may be cheaper, because all of the drive units can be less expensive if they are well-chosen to play specific bandwidth-limited roles.

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Originally Posted by bossobass View Post

I've never favorably compared the Dayton Ref driver to a Fi Q as a superior product, nor would I with a straight face.

For most uses, the Dayton Ref is heads and shoulders superior. It can be used as both a ULF air pump and as an upper-bass pressure source at the same time, because of its motor design.

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Originally Posted by bossobass View Post

I've never said the Fi Q has unacceptably high Le, then in the same sentence admit I don't even know what its Le spec is.

A reasonable person can infer from the design (long, heavy coil, no attempt to control inductance or inductance modulation over stroke) and the lack of a published spec that it has unacceptably high Le to be anything but a ULF air pump with extremely limited top-end bandwidth.

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Originally Posted by bossobass View Post

To the first and main question, you've gone on and on about the lack of relevance, that it's artifact from sloppy production practices, that it only appears in source you consider garbage, etc. You've tried to defend this position by burdening others to prove it to you personally while posting nothing whatever to back your assertions.

Again, I'm not the one making the rather extraordinary claim that a Sting album released in 1999 (before basically anyone had a system capable of perceptually-relevant levels of ULF) has perceptually-meaningful ULF content.

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To the second point, although Dolby, THX and everyone else in the MC audio world has standardized the LR4 LPF at 80 Hz, you assert that a subwoofer must be crossed over at 150-200 Hz to exhibit fidelity. Again, zero data to back your position,

First, you're misstating. I wrote 120-150Hz.

Second, I have data: upper-bass measurements of actual systems in real rooms.

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It's relevance is that a) it's on the disc,

Obviously not dispositive to a question of perceptual relevance, even to a simpleton.

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Originally Posted by bossobass View Post

b) my system accurately reproduces it and

Totally irrelevant and out of the scope of the discussion.

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Originally Posted by bossobass View Post

Ic) if your system does not, there is an audible distortion in the presentation.

Way too many assumptions in there that may not hold.

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post #289 of 585 Old 07-30-2011, 09:54 PM
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No, it doesn't.



In theory and practice, that is simply incorrect.

As for the theory, let's dispense with that first with Dr. Toole's words from Sound Reproduction. at 245.


As for practice, frankly, your argument is one only available to a person who simply has no relevant practice. That is to say, s/he has simply not experienced a properly set-up multisub system. Subjectively, I've found that a well set-up multisub system will sound firmly "locked" in time, far more so even than a stereo pair of full-range speakers, let alone a system using a single subwoofer crossed over in the modal region. Transients have more impact, the sonic image is more palpable, and the overall sound of the upper bass is just...natural. In a way that no stereo pair of monopole speakers (or speakers sitting atop subs, or single subs with a pair of monopoles, etc.) can be. (Dipoles can get close - the best 2-channel bass I've heard, including the Orions at AXPONA this year and a friend in Vienna's Audio Artistry Dvoraks, were from a pair of Gradient Revolutions) but have placement restrictions that make them untenable, at least for me. I suspect the same applies to cardoids.)

My experience is consistent with that of others who have tried it. (As well as high school buddies now playing in major symphony orchestras who have heard my system. One asked me to design a similar system for her - yes, her, the ULF stuff doesn't seem to appeal to anyone but a small subset of men, but more natural sound in the upper bass interestingly enough seems to appeal to everyone who loves music - after she heard it.) Look on the forums for subjective reports from people who have heard Dr. Geddes' home system. All comment on how natural the bass sounds. In fact, the only negative report of a multisub system I've heard has some from Penn, who simply did not (and still seems not to) understand the concept well enough to apply it with the slightest modicum of competence.

Not only that, but also experience listening to such a system will sensitize one to the wretched state of upper bass reproduction in most audio systems. IOW, the nasty bass response measurements one sees even from stellar "full range" stereo mains well set up by knowledgeable people are audible in practice, even if people without experience in high fidelity bass reproduction do not seem to notice.

And the fact of the matter is, in-room upper bass response for stereo pairs of loudspeakers in domestic living rooms is just tragically bad. (Measurements for systems using a single subwoofer are generally worse, because there is one one pressure source driving the room, as opposed to two.)

Here is the best in room measurement of a stereo pair of "full range" monopole-in-the-upper-bass loudspeakers I've ever seen.



The loudspeakers are Revel's Studio2, and they were measured for Stereophile by JA in Slate foreign affairs columnist Fred Kaplan's room. There is also an in-room measurement for a lesser speaker - Verity's nasty sounding $40k Parsifal - in the same room on that graph; The Revel is in red.

Note that from 30-120Hz there is about a 12-13dB swing. (The lesser speakers have about an 18dB swing over the same bandwidth; even that is better than most in-room measurements) Compare that with my various multisub setups' in-room measurements. Most people, because of both the relative inferiority of their speakers* and setup, will have much worse results than the Revels achieve in Dr. Kaplan's room!

For reference, here is the Revel's native frequency response, in the bass and elsewhere:



*Performance-wise, the Revels are basically unimpeachable. Also, I suspect the big Revel's combination of two bass drivers relatively high off the ground and a bottom-firing port with an EBS tuning frequency offers smoother in-room upper bass than would a single woofer of equivalent volume displacement placed near the floor.)



Not really. I wouldn't use a 200Hz crossover to subs. Well, maybe Parham-style "flanking subs," were I to use them (and there are measurable benefits to doing so).



Again, such things could only be written in the absence of practical experience with such a setup.



You have the weight of basically the entire serious audio community against that assertion.]

Dr. Floyd Toole is simple dismissing time domain smearing because he doesn't want to deal with it or account for it in his chase for a flat smooth frequency response. That doesn't mean that it doesn't exist or that it can't be heard. Stereo sound images better when all parts of the sound sources originate from the same proxcimity. If that part of accurate sound reproduction is not a high priority to you, that's a personal choice and in my opinion, a personal compromise. To each their own.
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Dr. Floyd Toole is simple dismissing time domain

Actually, had you read the quote and understood its content you would not have the mistaken impression that Dr. Toole dismissed anything. He simply pointed out that one can infer the time domain performance from the FR. If the FR is flat, the time domain performance will be good.

Subjectively, I've certainly heard improvements in "timing" as upper-bass FR has improved. I suspect anyone else who has set up or even heard a high-fidelity bass system would report likewise, because the improvements as one goes from a stereo pair to a stereo pair overlapping with a sub, to a stereo pair overlapping with multisubs is decidedly unsubtle.

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Stereo sound images better when all parts of the sound sources originate from the same proximity.

Again, a reasonable person can only assume you're talking without a lick of relevant experience.

Also, given your bleating about proximity, do your mains use coincident drivers or some other form of point-source (e.g. Quad ESL-63)?

I've not had a stationary audio system in the last 8 years that hasn't been anchored by mains with KEF Uni-Q's or Tannoy Dual Concentrics. So I know a thing or two about the advantages of getting as much of the spectrum as possible from the same point in time. And because I have functioning ears, I know that the only thing that happens if the bass comes from the same place as the rest of the spectrum is lumpy, amusical upper bass.

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post #291 of 585 Old 07-31-2011, 04:07 AM
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Actually, had you read the quote and understood its content you would not have the mistaken impression that Dr. Toole dismissed anything. He simply pointed out that one can infer the time domain performance from the FR. If the FR is flat, the time domain performance will be good.

Subjectively, I've certainly heard improvements in "timing" as upper-bass FR has improved. I suspect anyone else who has set up or even heard a high-fidelity bass system would report likewise, because the improvements as one goes from a stereo pair to a stereo pair overlapping with a sub, to a stereo pair overlapping with multisubs is decidedly unsubtle.

The whole point is that a flat frequency response does not necessarily infer time domain performance. If that were the case, then any system which shows a flat frequency response whether by eq or otherwise would automatically have no time domain problems. That is nothing more than wishful thinking. It doesn't really matter that you, Dr. Toole, and a whole army of followers happen to believe in this. That doesn't make it so. You are simply trading away time alignment in the bass range for a flat frequency response. If that sounds good to you, that's great. It might be a worthwhile trade in your case, but don't delude yourself in thinking that by some miracle you fixed the lack of time alignment. You traded one problem for another and found that you preferred what resulted from that particular compromise. Again that's great if it's a worthwhile exchange for you. It's just not the only way to do things nor is it necessarily the best. Just like there is more than one religion in the world, more than one political system or more than a few philosophies on how to live your life, there are different ways to achieve satisfying audio results.

Unlike you, I'm not claiming that the way I do it is the only way or the best way. It is a means to an end that works very well for me in my room.


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Again, a reasonable person can only assume you're talking without a lick of relevant experience.

Also, given your bleating about proximity, do your mains use coincident drivers or some other form of point-source (e.g. Quad ESL-63)?

I've not had a stationary audio system in the last 8 years that hasn't been anchored by mains with KEF Uni-Q's or Tannoy Dual Concentrics. So I know a thing or two about the advantages of getting as much of the spectrum as possible from the same point in time. And because I have functioning ears, I know that the only thing that happens if the bass comes from the same place as the rest of the spectrum is lumpy, amusical upper bass.

No, my speakers are not time aligned in the midrange or in the highs to the degree of a single point source. It is probably a minor shortcoming of my system that I live with. I'm not going to pretend that somehow this lack of perfect time alignment either doesn't exist or that it can somehow be fixed by flattening the response. As it cannot be fixed this way in the bass range, it likewise cannot be fixed in the mids and highs. I know it exists and it is a compromise that I acknowledge and live with. The bass from 40-100hz, however, originates just a few inches from the main speakers. Relative to the wavelengths in this range, the bass is time aligned with the main speakers. Asymmetrical bass systems cannot be time-aligned by any means. It is impossible as long as there are room boundaries involved causing there to be a high ratio of reflected sound. That would mean virtually any room that is not an anechoic chamber. The higher up in frequency range you run your scattered bass system, the bigger the time aligment problem.

Fortunately, there is nothing lumpy or amusical about my upper bass. Perhaps in your case, you were getting lumpy bass because your room had poor acoustics and you didn't want to improve that with acoustic treatment or eq of any kind.
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post #292 of 585 Old 07-31-2011, 09:02 AM
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I don't know why you seem to be so adamantly opposed to the obvious physical reality that the volume of the cabinet sets the system's low end efficiency. Not the driver, the box.

Again, that's just Hoffman's Iron Law.



Simply incorrect on fact.

There is absolute sensitivity, i.e. x dB at y Hz at when driven with z V, and there is relative sensitivity, i.e. down m dB at n Hz re: p Hz.



We agree on something, it seems.

Box size changes system parameters, however. Such as, for example, low end efficiency.



Obviously, drivers in different sized cabinets will have differing low end efficiency. Nothing new to anyone here, including you or me. So why are you arguing, again?

Also, you're simply not so daft as to not understand the notion of normalized Le, which is Le/Re. You just seem to be playing that way on this thread. I get the feeling that no matter what I write, you're going to say I'm wrong. I could write that speaker wires don't matter as long as they're a sufficient gauge, and you'll counter with "nonsense, you need High End cables that cost at least $500/ft to hear anything."



Wait a minute. Are you claiming what I think you are, i.e. that there is a platonic ideal closed box?

I'd like you to elaborate on that point, because I've taken something quite different from your previous posts on the subject. Perhaps I've misinterpreted.



Hardly. In the real world people have space constraints, and may wish to see if a given driver will give them advantages in a given box volume. A driver that offers increased sensitivity in the top end of the subwoofer's bandwidth (120Hz, maybe as high as 150Hz) will be advantageous, if it still has sufficient volume displacement to reach the desired low end cutoff at a given SPL. The amp will have to work less hard in the upper bass that way, given that the system is more efficient up top and equally efficient (because ULF efficiency is set by the box size) down low.



I've read the graphs. They simply don't support your point.



Perhaps because I assumed that reasonable people would fill in the rest of my sentence. Since my assumption may have been unfounded, here's the rest of it.

"F3 is irrelevant because you can EQ to taste, within the limits of the volume displacement of the subs, which is limited by the drivers' excursion and/or the available power."

Obviously, for any LF cutoff at a given SPL, one needs first to have the volume displacement to get there, and the power to push the woofers to that volume displacement. Among reasonable enthusiasts, those points should be givens.



We agree that inductance is irrelevant to ULF performance, and also presumably also agree that it very much matters for upper-bass performance. Also, I presume we can agree that upper bass appears constantly in musical program material, so it makes sense to prioritize its reproduction over the reproduction of signal that appears sporadically at best. (And is of debatable perceptual relevance in the first place.)

We also now agree that 1W/1M specs are irrelevant in the low bass, apparently, though you claimed above that less efficiency was ipso facto better.

Hopefully, we also agree that the reason why is because the low-end efficiency of a closed-box subwoofer system is set by the trapped volume and not the driver.



Yet, of course, in actual practice you prefer drivers with shorting rings and low inductance. Just as I do.



Though you must concede that it can be, right?



Obviously not. You're asserting the opposite, but aren't able to offer any evidence for that assertion other than the occasional mere presence of ULF. And even then, you've only given one example, outside of the program material we both agree contain ULF that in the current day is probably intentionally-placed and that some people may prefer to reproduce.



Nor have I, only that they are not worthy of use except in very limited circumstances, i.e. as ULF air pumps in systems with multisubs to cover the spectrum above their very limited bandwidth. The primary disadvantage of that approach is that one needs more subwoofers, because a ULF air pump cannot also act as a pressure source in the modal region without compromising the whole system. An advantage is that despite that requirement it may be cheaper, because all of the drive units can be less expensive if they are well-chosen to play specific bandwidth-limited roles.



For most uses, the Dayton Ref is heads and shoulders superior. It can be used as both a ULF air pump and as an upper-bass pressure source at the same time, because of its motor design.



A reasonable person can infer from the design (long, heavy coil, no attempt to control inductance or inductance modulation over stroke) and the lack of a published spec that it has unacceptably high Le to be anything but a ULF air pump with extremely limited top-end bandwidth.



Again, I'm not the one making the rather extraordinary claim that a Sting album released in 1999 (before basically anyone had a system capable of perceptually-relevant levels of ULF) has perceptually-meaningful ULF content.



First, you're misstating. I wrote 120-150Hz.

Second, I have data: upper-bass measurements of actual systems in real rooms.



Obviously not dispositive to a question of perceptual relevance, even to a simpleton.



Totally irrelevant and out of the scope of the discussion.



Way too many assumptions in there that may not hold.

"Daft", "simpleton", "perceptual relevance", "shorting ring", "150 Hz crossover", "Geddes", "garbage", "spacial average", "absolute sensitivity", "ULF air pumps" "same box for every driver", "Dayton".....

Yeah, got it.

BTW, purpose of flat response to <20 Hz... why does it matter?

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post #293 of 585 Old 07-31-2011, 11:03 AM
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Yeah, got it.

BTW, purpose of flat response to <20 Hz... why does it matter?

Simple petulance is definitely a large improvement over spreading incorrect information just because you're mad at me or something. So thank you for that.

And sadly, the question of why flat response below 20Hz may matter has not come even close to having been answered. The best guess, based solely on your hand-waiving, is probably "it doesn't, much."

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The whole point is that a flat frequency response does not necessarily infer time domain performance.

Well, unless you have data to show otherwise, that's simply your word against the consensus empirically-backed opinion of serious audio engineers.

That said, it's entirely possible you are right and everyone else is wrong. Those kinds of situations are how science develops.

Do you have measurements to back up your assertion? I'm certainly willing to take a look. But absent measurements showing some validity to your assertions, you're just blowing smoke.

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If that were the case, then any system which shows a flat frequency response whether by eq or otherwise would automatically have no time domain problems.

Down low, at least, where the wavelengths are large compared to the size of the room, that is correct.

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You are simply trading away time alignment in the bass range for a flat frequency response.

Incorrect. Fixing the FR in the modal region fixes the time domain, too. See Toole, supra.

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Originally Posted by mojomike View Post

If that sounds good to you, that's great.

It doesn't sound good just to me, mind. It seems to sound good to everyone who's actually tried it. (Except for Penn, who as mentioned didn't really know what he was doing. He seems to have thought spreading a few 8's in his room and setting them up sequentially per Geddes would give him adequate SPL in a fairly large room, and condemns the method because of his poor optimization in the design phase of the system setup.)

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there are different ways to achieve satisfying audio results.

You're shifting the scope of the discussion from "high fidelity reproduction" to "satisfying audio results." Plenty of people get "satisfying audio results" from the the earbuds that came with their iPods, so that standard is not a particularly high one to reach.

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Unlike you, I'm not claiming that the way I do it is the only way or the best way. It is a means to an end that works very well for me in my room.

You really haven't read my posts very carefully or with much comprehension. I've never claimed my way is the "best way," I've simply (and accurately) claimed that the methods I use consistently lead to superior measured performance, i.e. higher fidelity to the source material, in the upper bass. There are a few other ways to get there, for instance given one's room geometry fits the assumptions and one is willing to have bass arrays on two opposed walls, a Double Bass Array done right produces high fidelity upper bass. Loudspeakers with dipole or cardoid radiation patterns in the upper bass is another approach that tends to result in smoother upper-bass response, at least for people who are willing to have wide loudspeakers jutting out in the middle of their rooms. (I am not among that group. I prefer my audio be heard and not seen.)

But whether someone actually wants high fidelity to the source material or not is a personal preference issue. Though generally speaking it's a preference that most listeners cannot really form, given that they haven't actually experienced a system with the bass set up per current best practices. I don't know why, honestly, as it's not terribly expensive to do well and it tends to be pretty easy to integrate/hide in a domestic living room as well.

I also cannot help but note that you've not answered my claims in a relevant way, that is to say by showing spatially-averaged measurements of a system doing things totally inconsistent with what I've found (and demonstrated through posted measurements) works but that still achieves exemplary upper bass frequency response linearity and smoothness.

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No, my speakers are not time aligned in the midrange or in the highs to the degree of a single point source.

IOW, in practice I actually care more about "time alignment" than you do, given that every loudspeaker I've bought for years has been a single point source at frequencies where such things may matter (smaller wavelengths). Interesting. And absent measurements to show that your assertions are based in some sort of observed reality, that means a reasonable reader can safely dismiss the rest of your post as silly hand-waving about a total non-issue.

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Fortunately, there is nothing lumpy or amusical about my upper bass. Perhaps in your case, you were getting lumpy bass because your room had poor acoustics and you didn't want to improve that with acoustic treatment or eq of any kind.

First, I do use EQ, of course. When needed, at least. EQ can fix issues in a limited area with poor sub placement. With a multisub system set up according to current best practices, EQ can fix issues over a larger area, because seat-seat variation in the bass is lower.

Given that you haven't shown measurements, one can reasonably infer that your in-room response in the upper bass is at best no better than JA measured with the big Revels in Dr. Kaplan's room. That kind of upper-bass performance I think is fair to characterize as "lumpy" and "amusical." Though someone who hasn't heard a system with more natural upper bass may well simple ascribe the difference to the deficiencies of canned vs. live music. People with actual experience enjoying unamplified live music (or making it in the first place) are usually surprised by how natural and lifelike upper bass - and thus music - can sound in a room, simply because they've never before heard such a thing.

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probably "it doesn't, much."

Could've saved this thread the endless drivel and just said this^^^

Of course, it would need to be followed by; IMO.

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a reasonable reader can safely dismiss the rest of your post as silly hand-waving about a total non-issue.

As I suspect is the case with the majority of people reading this thread, a lot of the points being made are a bit above our heads. I personally like to read this stuff because I can learn from it. However, the quote above, along with all other such examples in your posts, just make you come off as a pompous know-it-all. That tends to lend less credibility to your points, not more.

And before you reply with an even more pompous "well, I'm RIGHT. Don't be upset at me if others can't acknowledge that," just remember a couple things: there are obviously no absolutes as you claim, or else there wouldn't be so many differences of opinion (both among pros and lay-people). And irrespective of your "rightness," your condescending tone and constant shots about people's lack of understanding or daftness make people tune you out. So if your point was to instruct, you fail.

And that's all I've got to say about that.
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As I suspect is the case with the majority of people reading this thread, a lot of the points being made are a bit above our heads. I personally like to read this stuff because I can learn from it. However, the quote above, along with all other such examples in your posts, just make you come off as a pompous know-it-all. That tends to lend less credibility to your points, not more.

And before you reply with an even more pompous "well, I'm RIGHT. Don't be upset at me if others can't acknowledge that," just remember a couple things: there are obviously no absolutes as you claim, or else there wouldn't be so many differences of opinion (both among pros and lay-people). And irrespective of your "rightness," your condescending tone and constant shots about people's lack of understanding or daftness make people tune you out. So if your point was to instruct, you fail.

And that's all I've got to say about that.
Thank you, and well said.

Having been accused of spreading misinformation, I would like to just say, for the readers of this and similar threads, that the idea that content below 20 Hz in modern digital recordings being unintended artifact has been beaten to death and is an absurd insinuation.

As to it's relevance, Scott sums it up quite well:

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I perceive all these <20hz effects even at low volumes levels, btw. You become conditioned to the effects and signature of super deep bass once you've lived with that capability for some time. It's quite hard to miss once you know what it feels like. Bosso knows what I mean.
Lot's of folks with capable systems will co-sign Scott's sentiments. Those who continually argue against the relevance just happen to be those folks who've never experienced full bandwidth audio.

As to posting pertinent data, DS-21 has posted nothing, save the following:

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Why do you want to minimize "bass overlap?"

It is precisely that overlap that leads to smoother upper-bass response! It's what takes a system from low-fidelity mush in the upper bass:


(single sub in a corner)

to high fidelity:

(properly configured three subwoofer system, using the above subwoofer from 20-120Hz, and the other two subs from their ~40Hz low-end cutoff until 120Hz as well.)

Of course, one does need to take measurements to properly set up a subwoofer.
So, using the Velo SMS-1 and its included Behringer EM-8k mic, which is not worth much below 30 Hz and grossly smoothed in the area DS-21 crows about, he believes he can use only that data to proclaim what is relevant, high fidelity and low fidelity mush.

OTOH, I use state-of-the-art measurement microphone, microphone power supply, microphone pre-amp and computer interface hardware, along with software that provides infinitely more accurate data for examining the crossover region.

That would make the Velo SMS-1 kind of a silly tool in comparison and many reading this thread know this. Yet, instead of those in the know bringing it up to DS-21, it is DS-21 who waves his primitive graph around as though he's found the Holy Grail and everyone else is in the dark.

Here's a measurement before any post processing (like the MiniDSP DS-21 prefers to use), using the resolution of the SMS-1, but being absolutely accurate to 10 Hz with no calibration needed:



This is using a "high Le, thus low fidelity driver", and obviously could be tweaked to a ruler-flat line with any post PEQ hardware and little effort.

Unfortunately, this is the same measurement with no smoothing:



So, applying post massage PEQ would be of little value, but more importantly, it exposes the delusion a smoothed version of the measurement can induce, not to mention the caution required against beating one's chest over the smoothed graph as evidence of some superior setup method and truncated BW preaching.

I could post this graph instead and make up some pseudo-tech baloney as to why my setup method and driver parameters are far superior to Gedde's and whatever other flavor-of-the-week gurus.



That would be embarrassing to me. Apparently not so to many people who are lots smarter than I.

Get a flat response to as low as you can given your budget and room. The lower you can cleanly reproduce, the more your enjoyment of movie playback will be. That's not an opinion, it's a consensus of opinions among those who have done so over the years and recently, right out of the gate.

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post #297 of 585 Old 07-31-2011, 03:22 PM
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Having been accused of spreading misinformation, I would like to just say, for the readers of this and similar threads, that the idea that content below 20 Hz in modern digital recordings being unintended artifact has been beaten to death and is an absurd insinuation.
Actually, "unintended artifact" is to date the most reasonable hypothesis for that ULF content you found in that Sting track from 1999.

And I think it's telling that you've come up with precisely one example from outside the world of plotless special effects wonders, though in fairness you've also written on this thread that you can't stand to listen to actual music on your system...

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So, using the Velo SMS-1 and its included Behringer EM-8k mic,
Actually, I'm not using "its included***mic." My measurements are a 5-point spatial average using Velodyne's MIC-5 spatial averaging kit.

The distinction between "its included***mic* and "its included***mics" is non-trivial.

And you know or should know that. It's been posted in this thread. So why you keep intentionally and/or recklessly spreading misinformation is beyond me.

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Originally Posted by bossobass View Post
which is not worth much below 30 Hz and grossly smoothed in the area DS-21 crows about,
Actually, I've previously found that the SMS-1 gives basically results to the same mic setup run sequentially through an M-Audio FireWire Solo using FuzzMeasure Pro on my MacBook and averaged in the program.

Others have compared it to REW and other consumer measurement systems and found the same result.

So, given that I do have "better" stuff, why continue to use the SMS-1? Its real-time continuous sweeps and large display make setup easier and faster, compared to an MLS system. One doesn't have to go back and forth between multiple computer programs (the DSP setup and the measurement program).

So you're just blowing smoke, which as an added bonus gives you an extra opportunity to brag about how expensive your measurement setup is. (I never claimed mine was lab grade. It's simply not necessary for the application.)

Also, despite your expensive setup, all the measurements you post are single-point. As you know or should know, single-point measurements are a statistical approximation of the true response. (So are spatial averages, of course, but just as with any statistic, a higher n will get closer to the true value.)

So what you're getting is simply bad data despite the fancy measurement gear.

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post #298 of 585 Old 07-31-2011, 04:08 PM
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All I know is that this



Does not sound nearly as good as this with music or movies



I measured every seat(7) and they were all within +/- 3 db's thru the whole range.
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post #299 of 585 Old 07-31-2011, 04:57 PM
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Quote:
Originally Posted by MKtheater View Post
All I know is that this



Does not sound nearly as good as this with music or movies



I measured every seat(7) and they were all within +/- 3 db's thru the whole range.


That's no easy feat!
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post #300 of 585 Old 07-31-2011, 07:46 PM
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Quote:
Originally Posted by MKtheater View Post
All I know is that this...

Does not sound nearly as good as this with music or movies
Agreed. And, even in your masonry room where there is likely less shake than in my frame room, I know you know the difference with and without <20 Hz is a no-brainer, because you've been there with a hundred flicks.

My son and nephew were here with a couple of their friends, so I decided to (yet again) run the simple test. I had Star Trek in the player. I asked them to sit down and watch a few scenes. I said that I would play the scenes one at a time and repeat each scene twice and then repeat the scene once more. I asked them to pay attention to the sound the first 2 times, then to see if they notice a difference the 3rd time. I asked them to hold comments until the scenes were all watched this way.

I ran SL graphs of one of the scenes. The first 2 times the scene was played with an 18 Hz HPF in line. This is only a 2nd order filter, so there is still some output below that (more so than a ported, PR, BP, horn sub, for example). The 3rd time I repeated the scene with full BW.

Here's the scene with 18 Hz HPF:



Here's the same scene with no HPF:



Comments afterward:

"Waaaaay different!".

"The floor felt like it rippled".

"It was like the Matrix, where Neo flexed the hallway".

"No question there's a BIG difference".

It's the same reaction every time. Age, gender, movie preference... doesn't matter, they always say there is a very noticeable difference and with ULF is "better", "way more fun", "scary", "intense", etc.

If it weren't unanimous, I wouldn't post that <20 Hz is as important as I know it is.

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