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Science on low frequency quality?

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jsilvela

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So if you are not looking for science (studies?) that proves that it works, are you looking for studies explaning WHY it works? If you are asking for blind tests it sure seems like you're looking for evidence that there is an audible difference? What else would they be doing in the blind test? :)
The Welti/Geddes/Toole approach seems predicated on getting flatter FR at more locations, and less spatial uniformity.
That is coherent with the general direction of their approach in higher frequencies. This makes good sense to me.

The Fazenda et. al. paper, cited in a previous response in this thread, uses a blind test with 20 subjects and several sub setups, and ends up concluding (caveat emptor, this is a single study etc. etc.)
To quote from it:
It appears that, for high quality critical listening conditions, those systems ensuring a faster decay of low frequency energy are preferred over those attempting a direct “flattening” of the magnitude frequency response.

I guess that this appeals to me. More debate. Blind tests can lead to unexpected outcomes.
 

sigbergaudio

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The Welti/Geddes/Toole approach seems predicated on getting flatter FR at more locations, and less spatial uniformity.
That is coherent with the general direction of their approach in higher frequencies. This makes good sense to me.

The Fazenda et. al. paper, cited in a previous response in this thread, uses a blind test with 20 subjects and several sub setups, and ends up concluding (caveat emptor, this is a single study etc. etc.)
To quote from it:


I guess that this appeals to me. More debate. Blind tests can lead to unexpected outcomes.

I haven't read the Fazenda paper, but I'm assuming by reducing decay they suggest / refer to acoustical dampening of the room? Is that correct?
 

sigbergaudio

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Skimmed the Fazenda paper now (which is apparently a decade old). It seems in all their equalizing tests they're using 1/3 Octave bands(?), which obviously results in a very imprecise and limited equalization. The results shown in this paper isn't very relevant to what can be achieved with DSP today. Disclaimer: I didn't read every word of the paper so I may have missed something here.

Example, from the study, here is before and after EQ of a single sub in their test:
1674062552786.png


Any modern DSP and/or manual EQ from a competent person would get a far better result than this. Based on the different measurements of all the things they tried in that paper, I bet I could get a perfectly flat 20-100hz (within +/-2dB) in that room with a couple of subs + DSP / manual EQ.
 
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jsilvela

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I haven't read the Fazenda paper, but I'm assuming by reducing decay they suggest / refer to acoustical dampening of the room? Is that correct?
Not damping, no.
In the two "winning" configurations, they used subs in anti-phase (taking the wave propagation time into account) to cancel out the largest modes.
 

sigbergaudio

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Not damping, no.
In the two "winning" configurations, they used subs in anti-phase (taking the wave propagation time into account) to cancel out the largest modes.

Right, sounds way more complicated than necessary, and the results didn't look any better than a typical dual sub setup. The decay times were apparently better, which is good - but you started this by complaining that people suggested complicated solutions, so this approach should be disqualified from that premise I assume? :)
 

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I took the OP to mean that sub optimization takes lots of time and money. So OP has a question: can a person have a reasonable expectation that the expenditure of time, effort and money will be worth it in the end? How can I know it will be worth it? Has research been done to show that listeners actually prefer an optimized system?
I think that the original question has been answered, and answered well, that yes, the research has been done, and yes, optimization has been shown to be preferred.
 

youngho

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Hand-waving: At 80 Hz a wavelength is about 14 feet (169", 4.3 m). Your ears are maybe 8" apart, or about 0.047 of a wavelength at 80 Hz (a delay of about 0.6 ms). At low frequencies the wavelength is so large relative to our head that the sound appears to arrive at both ears at (nearly) the same time, making it difficult to impossible to resolve phase differences, so we lose the ability to determine direction. Our hearing sensitivity is also much lower (look up equal loudness curves and see how much louder 80 Hz needs to be to be heard as loud as 1 kHz).

See e.g. https://en.wikipedia.org/wiki/Sound_localization for a discussion of ITD and IID (time and intensity differences used to determine direction) and some of the math describing how small an difference we can localize. At higher frequencies, we can resolve down to the microsecond level, but at low frequencies wavelengths are too large to distinguish direction. From the Wikipedia article:

"The lowest frequency which can be localized depends on the ear distance. Animals with a greater ear distance can localize lower frequencies than humans can. For animals with a smaller ear distance the lowest localizable frequency is higher than for humans."

HTH - Don
I have the following problems with this explanation:
1. At 160 Hz, the wavelength is 7 ft, and at 320 Hz, the wavelength is 3.5 ft (still wider than the human head), etc, so at what frequency range would this hand-waving explanation predict one's ability to localize the direction of the sound?
2. The speed of sound is constant, so sound will appear to arrive at each ear at nearly the same time, regardless of frequency.
3. If the lowest note on a double bass is plucked by a player standing on your left side, would your hand-waving explanation suggest that you would be unable to localize it?

Interesting history about the choice of 80 Hz for crossover: https://twit.tv/shows/home-theater-geeks/episodes/1, specifically 20:50-22:30 or so. Tomlinson Holman also discusses it briefly in his book Surround Sound, second edition, which I don't have available right now, but I don't remember him mentioning the detail about Swedish radio there.

Griesinger's video (well-respected, developed Logic 7, used to work at Harman, mentioned in Toole's book and many articles about concert hall acoustics) is worth reviewing.

In our home media room, we have two subwoofers, currently used with Dirac correction up to 400 Hz. Our setup would not allow for mid-front and mid-rear wall positioning, so I have one on each (nearly) mid-sidewall--I found the node for the first length mode for each wall, which is a little different because of the position of the entry door and equipment closet door on the left side, and split the difference for symmetry purposes. This way, a la Toole and Welti, the subs do not excite the first length mode and actively cancel the odd-order width ones. Is there such a thing as stereo bass? Welti doesn't believe in it (https://hometheaterhifi.com/technic...n-interview-with-todd-welti-and-kevin-voecks/), Griesinger says yes, @Matthew J Poes discusses here: https://www.audioholics.com/room-acoustics/stereo-bass. I actually have the subs as stereo for the possibility of contribution to the perception of spaciousness or spatiality when stereo bass content is available, otherwise most bass content is likely to be mono, anyway, and I'm using bass management, so what's the harm? This setup with the wider subs may also take advantage of Blumlein shuffling. In addition, I have several PSI AVAA C20s, so it's my eventual plan to do more home listening tests and comparisons, along with some measurements--part of my endless to-do list.

I do like seeing different ideas.

That was my main purpose in participating here. Instead of considering amplitude/phase (EQ/delay) correction versus electroacoustic damping, you might be interested to read about Dirac Active Room Treatment, which promises to combine the best of both worlds: https://www.dirac.com/introducing-dirac-live-active-room-treatment/.

Young-Ho
 
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jsilvela

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Right, sounds way more complicated than necessary, and the results didn't look any better than a typical dual sub setup. The decay times were apparently better, which is good - but you started this by complaining that people suggested complicated solutions, so this approach should be disqualified from that premise I assume? :)
Right, not going with that approach, but will definitely test the Front-Back (taken from Welti) as well as Front-Back anti-phase. Location-wise, those actually work in my living room.
And again, I was not trying to declare a winner. I do like seeing different ideas.

On the complexity of this whole thing. Let's say in a few decades, domestic low-frequency reproduction is a done deal, and people can buy a ready-made solution, from a few with good reviews at ASR of course. I hope then we'll look back at the current state of affairs and find it over-complicated.
 

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I have the following problems with this explanation:
1. At 160 Hz, the wavelength is 7 ft, and at 320 Hz, the wavelength is 3.5 ft (still wider than the human head), etc, so at what frequency range would this hand-waving explanation predict one's ability to localize the direction of the sound?
2. The speed of sound is constant, so sound will appear to arrive at each ear at nearly the same time, regardless of frequency.
3. If the lowest note on a double bass is plucked by a player standing on your left side, would your hand-waving explanation suggest that you would be unable to localize it?

<elided>

Young-Ho
That is why I linked to the Wikipedia article. It is not just wavelength, it is related to the phase, or time difference in arrival at a certain frequency, that we can resolve. That time difference is a function of spacing of the ears (and presumably brain processing the signals) and frequency (wavelength). The speed of sound determines how long it takes, but location depends upon the phase (or time) difference for the sound arriving at the ears (interaural time difference, ITD; we also use interaural intensity difference, IID). At long wavelengths (and thus low frequencies) the phase difference is too small to resolve. At higher frequencies the phase difference (based upon the spacing between ears) is much larger and thus much easier for us to resolve. This is not my area of expertise so I defer to the Wikipedia article and references therein for details, along with my old psychoacoustics text (I do not remember that one off-hand; the courses I took focused more on wave theory and mechanics, along with electrical analogs of the mechanical things like mics and speakers, than the psychoacoustics of it).

The argument about locating a bass or other instrument (or tone generator) is a common one but misleading. A bass produces a range of signals far above the fundamental, well into the kHz region for the bow or plucking fingers on the strings, so we can localize based upon that. Similar for other instruments. Decades ago when I was researching this I quickly found I needed to use a clean sine (single-frequency) generator to determine when we could no longer localize the bass. Back then I found different folk varied from nearly 60 Hz to nearly 100 Hz or so if I remember correctly (may not). There are also transients, again typically having higher frequency content, that enable us to localize things like percussive from plucked strings, kettle drums, and so forth.

HTH - Don
 
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DonH56

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hm, I think I've put my foot in my mouth.
In no way did I mean to be dismissive. Nor do I want to waste anyone's time. I'm sorry that's what's coming off.

I have seen the Welti presentation, as well as Geddes. And I have read the first edition of Toole's book that presented the Welti work.
The solutions to the LF conundrum they propose, are complex. More complex than appeals to me.
I may end up going exactly that route (I think MSO is an implementation of the Welti idea?)
I'll start slow, though. First get a second sub. Play with location, take measurements, repeat.

Of course I'm aware this is a forum, I was hoping for links, references, not a dissertation. The Fazenda et al. paper cited in a previous post here, for example, has been super interesting.
I, and perhaps others, are struggling to understand exactly what you are asking. I tend to multiplex ASR with work stuff so often do not read all the posts and get tripped up by not knowing the entire background. That said, one one hand you seem to consider using REW or MSO and dumping the numbers they spit out into a miniDSP complicated, but then find the applied papers from Geddes and Welti lacking in science. I'm confused by exactly what level of "science" you want to read. The high-level theory is simply (ahem...) the wave equation applied to small spaces and boundaries, figuring out how the waves interact with boundaries and each other. Like EM theory courses (which were a prerequisite for my acoustics classes), solutions quickly devolve from theoretical to empirical/numerical when you move beyond relatively simple situations like an empty rectangular room. There are programs like COMSOL designed for complex cases, and Matlab and other math analysis SW to help if you want to do it yourself.

If you want a simple solution, what I usually suggest is skimming the Welti presentation to help situate (place) the sub(s), then you can use REW to analyze the frequency response and play with delay and amplitude settings for each sub to optimize the in-room response. For a single sub, or two, that is not too hard.

HTH - Don

p.s. I have 1st, 2nd, and 3rd editions of Toole's book. The third edition is greatly enhanced and expanded so worth getting IMO. I don't recall if there is a much more on subwoofers, but there is a lot of additional info in the third edition. Skip the 2nd; it is basically a recovered 1st with a little extra tidbit here and there.
 
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jsilvela

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I, and perhaps others, are struggling to understand exactly what you are asking.
My bad. I don't have such a well defined idea myself, and evidently I am failing at articulating what I mean.

That said, one one hand you seem to consider using REW or MSO and dumping the numbers they spit out into a miniDSP complicated, but then find the applied papers from Geddes and Welti lacking in science. I'm confused by exactly what level of "science" you want to read.
Oh, shit. I did not mean to imply that the Welti and Geddes approaches are un-scientific.
I don't mean to demean their research.
And wanting to hear about blind tests having been done is not a dis on the people at ASR telling me that multi-sub / MSO / etc. have worked for them and they have noticed an improvement.

I'm sure many at ASR will have had the experience of showing their new setup, with one extra sub, 5 PEQ filters / a new component / whatever ... to a friend, wanting to get a WOW reaction, and have gotten a bemused "sounds nice. To be honest your system already sounded great".

If you want a simple solution, what I usually suggest is skimming the Welti presentation to help situate (place) the sub(s), then you can use REW to analyze the frequency response and play with delay and amplitude settings for each sub to optimize the in-room response. For a single sub, or two, that is not too hard.

HTH - Don

p.s. I have 1st, 2nd, and 3rd editions of Toole's book. The third edition is greatly enhanced and expanded so worth getting IMO. I don't recall if there is a much more on subwoofers, but there is a lot of additional info in the third edition. Skip the 2nd; it is basically a recovered 1st with a little extra tidbit here and there.
will try these suggestions. Thank you.
 

youngho

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That is why I linked to the Wikipedia article. It is not just wavelength, it is related to the phase, or time difference in arrival at a certain frequency, that we can resolve. That time difference is a function of spacing of the ears (and presumably brain processing the signals). The speed of sound determines how long it takes, but location depends upon the phase (or time) difference for the sound arriving at the ears (interaural time difference, ITD; we also use interaural intensity difference, IID). At long wavelengths (and thus low frequencies) the phase difference is too small to resolve. At higher frequencies the phase difference (based upon the spacing between ears) is much larger and thus much easier for us to resolve. This is not my area of expertise so I defer to the Wikipedia article and references therein for details, along with my old psychoacoustics text (I do not remember that one off-hand; the courses I took focused more on wave theory and mechanics, along with electrical analogs of the mechanical things like mics and speakers, than the psychoacoustics of it).

The argument about locating a bass or other instrument (or tone generator) is a common one but misleading. A bass produces a range of signals far above the fundamental, well into the kHz region for the bow or plucking fingers on the strings, so we can localize based upon that. Similar for other instruments. Decades ago when I was researching this I quickly found I needed to use a clean sine (single-frequency) generator to determine when we could no longer localize the bass. Back then I found different folk varied from nearly 60 Hz to nearly 100 Hz or so if I remember correctly (may not). There are also transients, again typically having higher frequency content, that enable us to localize things like percussive from plucked strings, kettle drums, and so forth.
I agree that it's more complicated than the initial hand-waving explanation, so I would have just omitted that part entirely. I also wonder how the perception may differ in relative free space versus a highly enclosed one, along with different source material (continuous test tones versus something with an initial attack and decay envelope, as often occurs with music.

It's certainly not my area of expertise, either, which is why I linked to Martens and Griesinger, as well as Poes. Griesinger is actually an expert, whose work has been cited many times (https://acousticstoday.org/the-art-...ons-in-research-and-design-kelsey-a-hochgraf/ and https://asa.scitation.org/doi/10.1121/1.4944787), so I wouldn't use WIkipedia to dismiss his belief. It's also possible that he's particularly sensitive to spaciousness, just as Toole seems to prefer lateral reflections. An analogy could be pitch sensitivity, where someone who has really acute absolute/perfect pitch may be particularly sensitive to wow/flutter from tape or record reproduction and may find historically informed performance (HIP) tuning to be intolerable, while my perfect pitch (I can identify any note played on the piano or violin, for example, without seeing it) is flexible enough that I can enjoy HIP recordings. It would be easy to imagine testing a few dozen listeners and concluding that perfect pitch does not exist, since it's relatively rare.

Part of the reason I brought up the history of 80 Hz is that it's interesting that this seems to have been chosen based on a single report using Swedish radio, which has certain implications regarding bandwidth and also source material.

In any case, it does seem possible to me that there may be more to bass "quality" as than simply flat (or smooth, if tilted) monophonic frequency response, and I hope the links I provided may illustrate some opportunities for further consideration or even discussion.

p.s. I have 1st, 2nd, and 3rd editions of Toole's book. The third edition is greatly enhanced and expanded so worth getting IMO. I don't recall if there is a much more on subwoofers, but there is a lot of additional info in the third edition. Skip the 2nd; it is basically a recovered 1st with a little extra tidbit here and there.

The second edition has a section on bass and subwoofers outlining Welti's earlier work (the original multisub), while the third edition goes into Welti's later work (looking at MSV and MOL for different subwoofer configurations and seating areas) in good detail. The second edition did have great data on acoustic treatments that was omitted from the third.

Young-Ho
 

youngho

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the applied papers from Geddes and Welti lacking in science
I find it interesting that the Welti approach seems to result in what I believe should be highly correlated monophonic bass at the listening position, while the Geddes approach from its very premise depends on decorrelated bass sources (besides https://www.dagogo.com/an-interview-with-dr-earl-geddes-of-gedlee-llc/, see https://www.diyaudio.com/community/...lly-localize-bass.247583/page-20#post-3769637, for example, and I notice that his comment here supports my part of my original speculation regarding his approach and the perception of bass spaciousness).
 

sigbergaudio

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The argument about locating a bass or other instrument (or tone generator) is a common one but misleading. A bass produces a range of signals far above the fundamental, well into the kHz region for the bow or plucking fingers on the strings, so we can localize based upon that. Similar for other instruments.

This is also a good argument for why stereo subwoofers isn't really necessary, almost everything have harmonics high enough that your speakers will reproduce them, thus giving a stereo image despite running mono subs. I typically run dual subs in mono, and I have atmosphere / perception of room / spaciousness in heaps.
 

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I agree that it's more complicated than the initial hand-waving explanation, so I would have just omitted that part entirely. I also wonder how the perception may differ in relative free space versus a highly enclosed one, along with different source material (continuous test tones versus something with an initial attack and decay envelope, as often occurs with music.
Others have argued that my simplified explanations, trying to make a complex subject more understandable, too often leave out too much. Point noted.

It's certainly not my area of expertise, either, which is why I linked to Martens and Griesinger, as well as Poes. Griesinger is actually an expert, whose work has been cited many times (https://acousticstoday.org/the-art-...ons-in-research-and-design-kelsey-a-hochgraf/ and https://asa.scitation.org/doi/10.1121/1.4944787), so I wouldn't use WIkipedia to dismiss his belief. It's also possible that he's particularly sensitive to spaciousness, just as Toole seems to prefer lateral reflections. An analogy could be pitch sensitivity, where someone who has really acute absolute/perfect pitch may be particularly sensitive to wow/flutter from tape or record reproduction and may find historically informed performance (HIP) tuning to be intolerable, while my perfect pitch (I can identify any note played on the piano or violin, for example, without seeing it) is flexible enough that I can enjoy HIP recordings. It would be easy to imagine testing a few dozen listeners and concluding that perfect pitch does not exist, since it's relatively rare.
I have not read the papers, will need to download tonight or this weekend. My point in linking the Wikipedia page was to (a) add depth to my explanation and (b) provide a reference others could easily find. Hopefully nothing in my post could be read as dismissing Griesinger; I did not couple the two in my mind and certainly did not think anything I posted implied that.

Part of the reason I brought up the history of 80 Hz is that it's interesting that this seems to have been chosen based on a single report using Swedish radio, which has certain implications regarding bandwidth and also source material.
My memory is of a THX paper back in the early 1980's, I think, but for all I know it could also reference the Swedish radio study (which I have not read). I also performed a number of experiments (part of a college class project) using subs in-room and out in a field (free space) to try to determine when we can localize them. 80 Hz was pretty much right at the mean of the 20~30 people who participated, IIRC. I tried using transients but decided I could not separate the higher-frequency energy so everything was steady-state. I really wanted to resolve the debate about whether we could sense and localize the initial pressure wave, but my limited tests were inconclusive. Again from old memory, indications were we located a drum rom the higher-frequency sounds and not the initial pressure wave, but since I could not separate the two I was never able to get a definitive answer. These days, digital recording and processing would make it easier to create a test signal with just the initial pressure wave. Be an interesting experiment.

And again, I have no idea how or if this ties into the papers you linked, have not read them yet.

In any case, it does seem possible to me that there may be more to bass "quality" as than simply flat (or smooth, if tilted) monophonic frequency response, and I hope the links I provided may illustrate some opportunities for further consideration or even discussion.
I wish I still had my AES membership! There, or one of the IEEE papers, had some interesting comments on how using just frequency response as a metric could be limiting. For myself, one of the problems is that subs still have a fair amount of energy well above the crossover (octave or more), so enough higher-frequency content can be present to localize them and mess up the image of things like that bass player if you aren't really careful. And of course getting a perfect response at one point often leaves very "bumpy" response elsewhere, maybe only a foot or so away. That is also one of the arguments for stereo subs. The counter is that most source material mixes all the LF sounds to mono anyway. I expected multichannel (SACD, ATMOS, etc.) to change that but from what I have experienced, read, and been told by folk doing film mixing, it is still mostly mono. Note LFE is a mono track in movies (yes, I know you know that).

For myself, I ran my subs mono and stereo, and ultimately decided I could not tell the difference except on maybe one or two tracks, and aligning stereo subs (pairs, in my case) was way more work.

The second edition has a section on bass and subwoofers outlining Welti's earlier work (the original multisub), while the third edition goes into Welti's later work (looking at MSV and MOL for different subwoofer configurations and seating areas) in good detail. The second edition did have great data on acoustic treatments that was omitted from the third.

Young-Ho
I had completely forgotten that, thank you. I had discussed the editions with Dr. Toole a number of years ago when the third edition first came out, and to the best of my memory I paraphrased his words. Now that you remind me, I think he decided Todd Welti had covered the basics well enough he (Toole) did not need to include it in the third edition but went to Todd's later work, but that is a fuzzy 10+ year old memory now. Again IIRC, some of the acoustic materials data was outdated and available elsewhere so he dropped it. He is an ASR member so better to ask him directly; my memory is fading these days.

Thanks for keeping me straight, or trying to - Don
 

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Not exactly.
The issue I'm going for in this thread is more of:
The "average" (loaded term I know) advice at ASR is to get multi-sub, use MSO, apply room EQ, have drivers that go to 20Hz etc.
The "beginner package" for low frequency is steep. Does it really make such a difference? Is it borne out by the science? Blind tests?

This is a website for perfectionists. You most likely can get pleasing sound with much less than the "average advice." That falls to taste, source material, whether you are a perfectionist, etc.

Also, the "beginner package" for LF is headphones. You reduce the "room" to a controlled, much more precisely defined volume that is worlds easier to pressurize. On the other hand it's harder to mic, and if you're getting pants-flapping bass from headphones you are assuredly wearing them wrong.
 

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My memory is of a THX paper back in the early 1980's, I think, but for all I know it could also reference the Swedish radio study (which I have not read). I also performed a number of experiments (part of a college class project) using subs in-room and out in a field (free space) to try to determine when we can localize them. 80 Hz was pretty much right at the mean of the 20~30 people who participated, IIRC. I tried using transients but decided I could not separate the higher-frequency energy so everything was steady-state. I really wanted to resolve the debate about whether we could sense and localize the initial pressure wave, but my limited tests were inconclusive. Again from old memory, indications were we located a drum rom the higher-frequency sounds and not the initial pressure wave, but since I could not separate the two I was never able to get a definitive answer. These days, digital recording and processing would make it easier to create a test signal with just the initial pressure wave. Be an interesting experiment.
I haven't seen the paper myself, but Holman's description of it was Swedish (presumably national) radio moving a subwoofer around, using the most sensitive program material and the most sensitive listeners, and 80 Hz was 2 standard deviations below the mean. From I remember of statistics, +/- 1 standard deviation encompasses 66% of a bell curve distribution, while +/- 2 standard deviations encompasses 95%, so 2.5% outlying at either end. I have no idea in terms of details like the material in question, how "most sensitive listeners" were determined, and how many Hz were in one standard deviation.

Interesting in your experiment that 80 Hz was the mean, which is lower than Holman's description, but this seems to suggest that a significant proportion of your subjects may have been able to localize lower than that.

Again, I still wonder whether it's possible that some listeners may be more sensitive to stereo bass.
I had completely forgotten that, thank you. I had discussed the editions with Dr. Toole a number of years ago when the third edition first came out, and to the best of my memory I paraphrased his words. Now that you remind me, I think he decided Todd Welti had covered the basics well enough he (Toole) did not need to include it in the third edition but went to Todd's later work, but that is a fuzzy 10+ year old memory now. Again IIRC, some of the acoustic materials data was outdated and available elsewhere so he dropped it. He is an ASR member so better to ask him directly; my memory is fading these days.
Actually, the acoustical treatment data that I found particularly fascinating was the effect of angle of incidence on absorption on OC fiberglass , as well as the effect of covering with cloth. This was provided by Peter d'Antonio, and it remains highly relevant but not readily found elsewhere. The Welti MOV/MSV and listener position data was new to the third edition and well-summarized in his table.
This is also a good argument for why stereo subwoofers isn't really necessary, almost everything have harmonics high enough that your speakers will reproduce them, thus giving a stereo image despite running mono subs. I typically run dual subs in mono, and I have atmosphere / perception of room / spaciousness in heaps.
Yes, I believe that this argument was part of why Bose chose 180 Hz as their crossover for their Acoustimass system. Since significant modal issues persist up to several hundred Hz in typical listening rooms, if flatter frequency response across a wider sitting area is the only consideration, it would actually make more sense to crossover the subwoofer higher than 80 Hz.

Young-Ho
 

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Yes, I believe that this argument was part of why Bose chose 180 Hz as their crossover for their Acoustimass system. Since significant modal issues persist up to several hundred Hz in typical listening rooms, if flatter frequency response across a wider sitting area is the only consideration, it would actually make more sense to crossover the subwoofer higher than 80 Hz.

Young-Ho

Yep, as anything else it's a compromise of many things.

After lots of testing on a number of elements (including localization), we ended up with 100hz (24dB/octave) as the roll-off point for our subs when they're configured to play with our speakers (which are subwoofer dependent).
 

DonH56

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I haven't seen the paper myself, but Holman's description of it was Swedish (presumably national) radio moving a subwoofer around, using the most sensitive program material and the most sensitive listeners, and 80 Hz was 2 standard deviations below the mean. From I remember of statistics, +/- 1 standard deviation encompasses 66% of a bell curve distribution, while +/- 2 standard deviations encompasses 95%, so 2.5% outlying at either end. I have no idea in terms of details like the material in question, how "most sensitive listeners" were determined, and how many Hz were in one standard deviation.
Got it. Aside, nothing to do with your post, but "small world" moment: his son once contacted me about an engineering position when I was looking for a new job. Unfortunately I had just taken a new position, but we had a nice chat.

Interesting in your experiment that 80 Hz was the mean, which is lower than Holman's description, but this seems to suggest that a significant proportion of your subjects may have been able to localize lower than that.
It was actually fairly sharp IIRC, a fairly narrow bell curve. But it was long ago...

Again, I still wonder whether it's possible that some listeners may be more sensitive to stereo bass.
Some certainly claim to be, but I have no direct proof either way.

Actually, the acoustical treatment data that I found particularly fascinating was the effect of angle of incidence on absorption on OC fiberglass , as well as the effect of covering with cloth. This was provided by Peter d'Antonio, and it remains highly relevant but not readily found elsewhere. The Welti MOV/MSV and listener position data was new to the third edition and well-summarized in his table.
Good points. I have it in other references and actually think of Toole for other things though he has lots of good data on it in his books. There are things like the old CRC handbooks and such that I usually go to first for data on acoustic materials; I had them before I had my first copy of Toole's book, back when I actually did some of this stuff for a living (sort-of).

Yes, I believe that this argument was part of why Bose chose 180 Hz as their crossover for their Acoustimass system. Since significant modal issues persist up to several hundred Hz in typical listening rooms, if flatter frequency response across a wider sitting area is the only consideration, it would actually make more sense to crossover the subwoofer higher than 80 Hz.
Higher room modes not handled by the main speakers is one of my main arguments for sometimes using a higher crossover (the other being speakers too limited in LF response). The problem is that the subs definitely get localized IME with high (>100 Hz) crossovers, so you have to use either stereo subs or place one on the centerline to prevent (reduce) that problem, and that can compromise smooth response.
 
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jsilvela

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[...]
if you're getting pants-flapping bass from headphones you are assuredly wearing them wrong.
Ha, love that. Duly noted.

Years ago I got into photography. That's another hobby for perfectionists and people who have both an artistic and a technical side. Like audio.
In photography I found "my level". I haven't changed camera or even bought a new lens in the last 10 years.
On audio, it had been dormant for *years*. When I got my first real audio set, I found this publication by Richard Hardesty "Audio Perfectionist".
 
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