Some of the speakers I've listened to with a low woofer approach pre-date the formation of Snell, so whether by design or accident others were already doing it before Snell.
Monitoring speakers in mixing rooms are generally a lot higher than home speakers, listened to closer, and have a huge mixing panel near by so any floor bounce signature heard by the engineer won't be the same as a typical home listening room anyway. Most engineers would also do checks on headphones as well, so trying to simulate any floor bounce the recording engineer "might" hear seems doomed to failure. Better to just try to avoid floor bounce cancellation in the speaker design.
Yes a line array will certainly help with the reduction of floor bounce cancellation in the upper bass, although I'm not sure how ideal it is in other ways to have the position of drivers producing bass / low midrange stretched so much in the vertical plane, unless the line array went right from floor to ceiling, becoming a true line array.
I'm not sure that it would do any better at solving the problem than a well chosen 3 way design where the crossover frequency serves to separate the floor bounce cancellation frequencies though.
Good point, it depends what your goal is. My goal is always to try to sound like you are in the acoustic space of the recording, rather than the band is transported into your room. In this case suppressing the primary floor bounce cancellation seems to be beneficial in removing one of the "conflicting cues" of the speaker/room from the playback process. If there is a floor bounce comb filter effect in the recording this will be reproduced with minimum alteration, and hopefully serve to reinforce any other spatial cues.
As someone has already suggested a long way back in this thread, getting a "realistic" and believable (not necessarily accurate) result is more about removing conflicting cues from the reproduced sound than it is about creating specific cues - as long as the majority of conflicting cues are avoided the brain can fill in the gaps and sense a realistic result.
For a single listener in a home environment with a relatively unobstructed floor there is only one ray from each driver that will hit the floor and have the right reflection angle to arrive directly at the listeners ears after the initial reflection.
Of course there are many other reflection directions that relate to the floor (such as missing the listener, bouncing off the wall behind them and coming back) but these all involve more than one reflection, and start to become chaotic in nature.
Certainly when we're talking about the floor bounce cancellation in the upper bass range, there is a distinct notch that occurs that is directly related to the geometry which is easy to measure and predict.
There's a major difference here though - you're setting up an "original performance", a speaker in a home living room is trying to reproduce a recorded performance in a different acoustic space. Fundamental difference.
Any floor bounce comb filtering effects that occur at the live event are part of the event, part of what makes that event what it is, and sound like it does. The floor bounce effect subtly changes the sound, but it would be wrong to call it detrimental, any more than any of the other reflections or acoustic properties of the recording space - it is what it is.
Because it's a real event, all of the various auditory cues are in agreement with each other, including any floor bounce, and a sense of reality for those present results.
However on playback a speaker is trying to reproduce a recording with many encoded cues with a minimum number of additional "spurious" cues, cues that don't relate to the original recording. Yes, floor bounce effect from a speaker is a real effect that has an analogue to the original recording venue, but that doesn't mean it's ok for the speaker to introduce it's own floor bounce cancellation that is different in character from that in the recording.
For a given listening position any floor bounce effect the speaker adds is going to be exactly the same for all instruments and sounds that it reproduces, regardless of their original position within the sound field, which is unnatural and would help the brain localize the location and height of the speaker rather than allowing an illusion of a window into the event to form in the mind.
The playback speaker is unique (compared to the original instruments) in that it is reproducing all of the different instruments from the same physical location. Any characteristics introduced by the speaker that give away where it is will be overlaid on everything it reproduces.
Another analogy would be cabinet colouration - in an original instrument like a guitar, or any other instrument with a box for that matter, the woody resonance of the box is not "bad", it's part of creating the unique sound of that instrument, however on playback we don't want to add any additional woody resonance from the speaker because it will affect everything played back by the speaker, which the brain quickly realises sounds unnatural because the same "signature" is present on all instruments, which doesn't happen in real life where each instrument produces it's own sound separately.
Sound creation and sound reproduction are two fundamentally different things, especially when one reproduction device is reproducing many original instruments.
Well when I was referring to close mic'ed, I was thinking of studio recordings which are taken within a few inches of most instruments, in a relatively dead room, and then have fake reverb, stereo spread and so on added later - in these cases there can't be a natural floor bounce effect that would be equivalent to what a listener a few metres away would hear. The floor bounce cue is missing from the recording.
Yes the ear can "tune out" a lot of things, and floor bounce may not sound terrible, but it could be the difference between sounding like the sound is coming from speakers, to the speakers disappearing and sounding much closer to "being there".
The recordings I've heard it most apparently on are some binaural recordings - which although designed for headphone playback, can still impart an amazing sense of "space" even on speakers. Somehow I doubt the dummy head used to record a jazz quartet was placed 20 feet in the air 🙂
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The floor bounce is just one particular room effect but an important one. Yes, it can be easily drawn as 2 rays from the speaker. In fact, if the speaker and its reflected image beneath the floor are drawn then the two paths and their time difference are obvious.
The perceptual importance of a room reflection is a function of arrival time, strength and arrival direction. Toole and Griesinger (and Baron and everybody else in concert hall acoustics) will tell you that delayed lateral reflections give a good sense of space and evelopment. Earlier reflections, especially floor and ceiling bounces, are perceived as frequency response aberations. Binaural hearing can't separate a floor bounce from the direct sound because our sense of source height is so poor.
Bech studied this by simulating a domestic room in an anechoic chamber with a large number of surrounding speakers. All the typical room reflections were varied in level and their perceptual thresholds were determined. Floor bounce in front of the speaker was found to be likely to be heard, meanng the typical level in the typical room was higher than threshold of perception.
Kates and Salmi, who I have quoted before, both found ways to make perceptually more correct frequency response curves considering a model of human hearing. They both found that midrange reflections, primarily the floor bounce, were perceptually significant.
The arguement that a floor bounce might be naturally occuring in a recording, therefore okay, doesn't hold water. Recordings will have lots of reflections, but likely different for each instrument. With your speaker in a room everything goes through the filter of the room reflections. The primary audible effect is the first dip of the series that is widest and deepest.
David S.
The outer pinna provides cues to the height of the source, through spectral notches and peaks whose level and frequency depend on the source height. This effect only works at higher frequencies due to the small size of the outer ear. The rest of the head is too symmetrical and small to provide height cues at lower frequencies. So, the floor bounce direction can't be uniquely detected unless the reflection contains appreciable very high frequency content.
I bring this up just to point out that we use the outer pinna response as one of our means of detecting the height of the sound source. Any confusing strong vertical reflections in reproduction would also lead to confusion for this detection mechanism. Thankfully, most direct radiators are narrow enough in dispersion in these frequency ranges, that this isn't a strong source of error. Just don't point a tweeter at the ceiling.
As an aside, an artifact of this is that it is possible to mistake the height of an object purely due to strong source frequency content in very specific bands. In an anechoic chamber, play a slow frequency sweep from 5 kHz upwards and at ~ 8 kHz and 12 kHz from a mono source, the apparent source height changes (I've tried it, its disorienting).
The Japanese performed a number of studies into source height localization and frequency response perception impact in the context of concert hall acoustics, published in the Journal of the acoustical society of Japan, for those interested.
Dave Dal Farra
Thanks, this is all subtle stuff for the most part. We're way past Allison in this discussion.
To answer your question, Yes, Olive (worked with Toole but people too often confuse Sean's work for Floyd's) found that early local playback environment reflections allowed natural and valid cues of the environment which the recording was made in to be more readily heard on playback.
For how to generate a "feel good" spatial envelopment effect on playback, Griesenger's work is a good start.
Dave Dal Farra
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Dave and David, are you talking about elevation or actual source height as in apparent source width (ASW)?
Markus, for myself, for the most part, actual source elevation.
I've seen postulates for years that size of source in the vertical direction (which is what I think you were referring to by ASW) is affected by driver layout, overlap and relative phase, but haven't seen any tests to validate or refute that theory.
Dave Dal Farra
Yes, of course, but . . . what percentage of the sound radiated by the loudspeaker is represented by those two "rays" (the ear's capture area as a percentage of the speaker's radiation polar)? In a typical listening room what percentage of the sound that ultimately reaches the ear is direct? And what does our mind "expect" when we listen to *any* sound source in a small enclosed space?
Hearing evolved outdoors, in a mostly anechoic space. In that context we hear mostly direct sound, but we can sense discrete reflections as well, and sometimes even place (localize) the reflecting object as well as the original source (a capability not developed in most modern humans). Listening in enclosed spaces, and interpreting the sound heard, is a learned experience. What we mostly do is "tune out" the reflection cues, so a familiar voice (or orchestra) "sounds the same" (within limits, of course) anywhere. But at the same time one part of our brain is "tuning out" the distracting reflections, another part is busy comparing "expected" sound with "actual" sound, and using that information to define the listening environment. What we end up "hearing" is a lot more complicated than those "two rays" suggest . . .
Both, or neither...The point is that our vertical sense of either source height or source dimension is poor. The effect of a floor bounce is much as a measuring microphone reveals it. Lateral reflections are a different matter, givng a nice sense of space and being easily separated from the the direct sound, therby not messing up perceived frequency response.
This is a constant point I've been trying to make throughout this thread: With a speaker in a live room we can't just look at the response from an omni mic and a real time anayzer. We must consider how binaural hearing, directional ears and a lot of brain processing interpret what comes in.
David S.
I would say "Pure Illusion". 😉 Having heard it done more than once - and quite successfully. But I don't know what the mic layout was, so can't really say about the 20' in the air.
Spent all last night listening to lots of different music on a big Simplex theater rig in a friend's basement. "They are here" or "You are there"? Didn't really matter. Some of the old blues records where just like being in the blues club, really - except maybe not as loud. We were walking around, talking, drinking, carrying on and so where the musicians and the audience. Tons of fun and just very natural. But big speakers in a relatively big room. Worked like a charm.
I usually avoid tweaking a speaker by peering directly
at measurement results e.g. gated FR on a screen.
HolmImpulse and Arta is used quite extensively, but
for direct comparison i prefer using a reference speaker
which is well known by measurement and may even have
different dispersion than the "speaker under question".
Of course we have to calibrate our ears, day by day
and hour by our. I have e.g. different preferences
for the presence region to be adjusted "by taste" at
a forenoon spent at home, than after some busy hour's
in town having been exposed to traffic noise etc.
For this reason a "final" tuning of a speaker evolves
slowly and must not be influenced by that short term
changes in "personal calibration".
But i do not use my eyes to calibrate my ears directly.
When i look at the graphical representation of some
measurements i usually make a pause before changing
a speaker's components and i will select from options by
ear and measure afterwards.
Interpreting a FR's fine structure due to "balance" is
often not that easy. It may lead to "something to be done",
of course. Measurement contributes to the whole
picture and often i used measurement to search for
differences between audibly distinguishable settings.
Those differences may not abviously show up in the FR
at all.
But i usually do not decide what to do by tweaking a
graph directly (like e.g. switching between different
inductors in a crossover and peering at the gated FR
while doing so).
This may seem a little odd, but this is the way i come
to most "stable" results.
After a speaker is somewhat "matured" i ask for other
listeners impressions, taking also different room setups
into account whenever possible.
In the long run i do not believe in a difference between
"correct" and "pleasing".
Kind Regards
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I tried to describe some of the ways in which our perception of balance changes from time to time and exposure to various noises earlier in the thread, but got shot down in flames...
The ear (if trained by critical listening) is incredibly sensitive to relative changes in response (even a 0.25dB shelf adjustment to the treble I find detectable on familiar recordings, with 0.5dB being fairly obvious) but is a lot less reliable at detecting absolute response on a day to day basis, as our ear/brain "calibration" is affected by various things.
As well as long exposure to environmental noise (the drone inside a vehicle for example) or loud listening to a fairly unbalanced system for an extended period of time, I also find that time of day and tiredness, recent quality of sleep and amount of exercise has a significant effect on perceived sound quality and balance.
If I haven't done any exercise for at least 3-4 days and/or haven't slept well (the latter often caused by the former) things often just don't "sound right". It's hard to describe exactly how it sounds wrong, except that it tends to sound duller, less dynamic, less sound-staging, (seems more "mono-like") less bass and treble, and the vocals can sometimes sound a bit prominent and harsh especially at higher volume levels. Separation of instruments is also impaired, especially at high volumes.
It's not a huge difference, to be fair, but enough for a critical listener who is used to making small tweaks to notice something is wrong, and the perceived difference can be greater than any tweaks that may be in progress. When I realise I'm in one of these phases I avoid doing any speaker tweaking or evaluation.
One day of vigorous exercise (like an hour of squash) and a good nights sleep and the improvement in sound quality the following day can be quite startling - to the point where you find yourself listening for hours on end enjoying the music because it sounds so damn good compared to how it had been sounding in the days leading up to that.
Whether it's a psychological change with state of mind and/or level of alertness/tiredness or an actual physiological change due to improved exercise/sleep cycles I don't know.
I think this is part of the reason why the final voicing of a speaker does need to evolve slowly over a period of a few weeks minimum - so that any variations in your perception go right through the cycles of change that they may have. What sounds right in a "down" time may not sound right in an "up" time, as you attempt to over-compensate for perceived shortcomings in the sound.
I tend to be the same - trying to dig out the cause of a small perceived error in balance from a FR curve can often be difficult if not impossible, (especially shelf type errors) however after making a change based on perceived balance I usually take comparative measurements afterwards to see exactly what has changed and by how much so that I can "learn" the correlation between perceived change in sound and measured change.
After doing this enough you often find you can listen to something and pinpoint the problem frequency range immediately before you even measure anything - and find out you were right afterwards. In the process it trains your critical listening skills further.
Certain types of response errors can be misinterpreted though, due to frequency masking effects, relative balance between different critical frequency ranges being perceived more important than absolute flatness and so on, so a measurement is still useful to make sure that you're not straying too far from flat, even if measurement is not the final arbiter of the end result...
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I just want to thank DDF for the info on the pinna, which appears to be a significant part of why we perceive music played back through two speakers as having variations in perceived height. I first heard about that when I worked at Dolby Labs back in the 1980's. I also want to thank Mandrake (Simon?) for perhaps the most understandable and practical advice regarding floor bounce. Specifically putting the woofs very close to room boundaries (usually the floor) so it's listener position cancellations will be out of it's freq. range, and then putting the mid-range driver(s) far enough away from room boundaries that it's major cancellation in freq. will be below the frequencies that the crossover lets that driver put out. I also love where he points out how floor bounce cues in a recording will be different for each instrument, and therefore potentially generate a sense of space during playback, as opposed to playback environment reflection cues being too consistent, and thereby arguably detrimental to the 3-D aspect of a reproduction.
One of the best systems I ever heard had woofs on the floor aimed differently (toed inward), and from 100HZ on up was D'appolito (sp?) "satalite" cabinets hanging from the ceiling (2 five inch KEFs and upper-mid dome and tweeter dome between them), and tilted down slightly - aimed right at the listener on the couch, to reduce reflections off the ceiling. It makes sense technically, and it sounded superb with any program source.
One point I want to stress is that these listenting room reflections don't just create one notch of roughly 12dB right smack in the middle frequency range in a typical living room. They do that, and also at all the integral multiples of that frequency, hence the term "comb filter". The notches taper off at higher freqs. since higher freqs get absorbed by typical room furnishings (drapes, couch, etc.). The good news is that these cancellation notches usually get filled in by other reflection paths. You could argue that the more paths the merrier, even though it's arguably a step away from fidelity in the time domain. So attempts to deaden the acoustics of the listening room, may or may not make it sound more pleasing. You'd be reducing the "fill-ins" of what could be some huge cancellation notches. I've found that putting 2 inch cotton rope along all the corners of the room (except at the floor) kills room ringing very effectively, but has little to do with floor or ceiling bounce, which may only get worse perceptually as you try to reduce it.
One of the best systems I ever heard had woofs on the floor aimed differently (toed inward), and from 100HZ on up was D'appolito (sp?) "satalite" cabinets hanging from the ceiling (2 five inch KEFs and upper-mid dome and tweeter dome between them), and tilted down slightly - aimed right at the listener on the couch, to reduce reflections off the ceiling. It makes sense technically, and it sounded superb with any program source.
One point I want to stress is that these listenting room reflections don't just create one notch of roughly 12dB right smack in the middle frequency range in a typical living room. They do that, and also at all the integral multiples of that frequency, hence the term "comb filter". The notches taper off at higher freqs. since higher freqs get absorbed by typical room furnishings (drapes, couch, etc.). The good news is that these cancellation notches usually get filled in by other reflection paths. You could argue that the more paths the merrier, even though it's arguably a step away from fidelity in the time domain. So attempts to deaden the acoustics of the listening room, may or may not make it sound more pleasing. You'd be reducing the "fill-ins" of what could be some huge cancellation notches. I've found that putting 2 inch cotton rope along all the corners of the room (except at the floor) kills room ringing very effectively, but has little to do with floor or ceiling bounce, which may only get worse perceptually as you try to reduce it.
With regard to DBMandrakes quote:
An Audiologist once told me that it is normal for pressure to build up in the inner ear, which would cause what DBMandrake described above. You can carefully pop your ears with your finger, pulling out, if that makes sense, and notice a substantial improvement in hearing, or get it to happen with exercise. It's one of the many reasons why the ear is considered an unreliable fidelity analyzer.
An Audiologist once told me that it is normal for pressure to build up in the inner ear, which would cause what DBMandrake described above. You can carefully pop your ears with your finger, pulling out, if that makes sense, and notice a substantial improvement in hearing, or get it to happen with exercise. It's one of the many reasons why the ear is considered an unreliable fidelity analyzer.
That training aspect is important to underline in my
opinion and also the importance of measurements as an
'anchor' to keep oneself from straying but
not being the final arbiter.
I couldn't have made that approach - also preferred by
myself - more clear than you just did in your words.
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Very interesting!
I have definitely noticed exactly this effect. Sometimes when I'm in a "doesn't sound right" phase if I pop my ears outwards as you describe. (By causing a vacuum by starting with a finger pushed partly into the ear canal then pulling it out quickly)
There is sometimes a noticeable improvement in sensitivity and quality that is similar to the effect of exercise. The effect generally doesn't last long though, maybe a few minutes to an hour, and sometimes goes away with a yawn.
I had always put it down to "tin lid-ing" of the ear drum, I hadn't heard the pressure explanation before.
As you say, recent exercise of a high enough intensity does seem to have the same effect on "clearing the ears", but seems to lasts much longer - up to a couple of days.
I guess it's just another good reason for regular heart pumping exercise 😀
Certainly if you're not aware of it or don't believe that a change could occur. If you're aware of it you can learn to spot the times when things "don't sound quite right" and avoid making judgements at those times.
I generally find if I keep up regular exercise every 2-3 days my hearing and critical listening is much more stable and consistent than if I don't, and I enjoy my music much more to boot 🙂
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Another technique, useful in scuba or on planes is to plug your nose and push air into your ear canal from your mouth.
Valsalva maneuver - Wikipedia, the free encyclopedia
It can help reset an otherwise murky sounding listening experience.
Dave Dal Farra
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