Yup I have seen bungs supplied with the speaker by the manufacturer. Cork, Rubber.
Cotton Wool or Polyester are quite interesting because they can be tweaked by compressing them.


Perhaps the issue of where sound is coming from, the suggestion that MEs should print speaker management into the audio, and the directional nature of one of the most common LF instruments, are all pertinent to topic after all.
I have seen speaker manufacturers recommend multiple full range sources rather than LF management for 5.1 rigs.

I believe quite a lot of reality is self evident. The initial wave front of a Kick Drum has trajectory. It has a starting point and will travel to say a candle flame, blowing it out. If the wavefront shown below comes at you from a full range say Left speaker, it will be very obviously sourced. Very differently to blasting equally from both sides as Mono LF would impose. A balanced cyclical wave could not do this. This 'blast' can be felt, which is how we hear such singularities, and for that matter ELF. It can be seen in the cone movement. It can be seen in the recording below. The first cycle is louder, asymmetric, and a different frequency to the subsequent settled tone.
In context the first two very unbalanced half cycles do not qualify for treatment as 50Hz. The actual pitch happens later.
http://www.soundonsound.com/sound-ad...-we-hear-pitch



DD

What do you mean by this?

If the frequencies are higher harmonics, then they will be produced by the mid-range/tweeter (depending on the exact frequencies). So I'm not sure why you are under the impression that referring to higher harmonics is relevant.

Crossovers don't work by sending kick drums to one driver and snares to another -- they send different frequency ranges to different drivers. The crossover doesn't know or care whether the 50Hz portion of the wave is originally part of a kick drum or a snare or a ground loop -- it just sends the 50Hz component to the appropriate driver.

Wikipedia has a fairly good intro to speaker crossovers. If you read that in addition to the links on the Fourier transform I shared earlier you should have a good understanding of how they work.

Because they do not have the knowledge to understand how this really works.

I will try to explain very briefly why this is a bad idea.

To make this (as suggested - 5 full-range speakers) work, each speaker must be full range, and they must have a reasonably similar response.

Since speaker location is already determined in a 5.1, this has to be fixed acoustically, with dsp/room correction, or a combination.

Even then, it will be next to impossible to get a similar sound field from each speaker, because in a small room the properties of the sound field with one small source will be largely determined by the room, and this can not be fixed by any room correction because there is no means of controlling the direction of the sound.

A sound wave can be described as pressure pulsating in periodic motion - this is what we measure, SPL - and a corresponding particle velocity vector. It is this pv part that determines the intensity and direction of the sound wave. And when the wavelengths get large compared to the size of the room, it will be the room boundaries that determines direction and amplitude of the pv vector relative to the pressure.

So even if you have 5 exactly similar full-range speakers, you will not get bass that has a wavefront (direction) coming from each speaker.

To add to this already hopeless situation, all speakers must also sum correctly for bass signals that are mixed together such that the signal comes from several speakers.

If you separate the low frequencies and add them together, you can send this one-channel signal to a bass system set up to provide a reasonably good bass response, where you actually can control all parameters. If the bass system has smooth frequency response, it will have the same smooth response for each single channel, and also for the sum of all channels. If the tactile response is good, it will be good for all channels.

With 2 subwoofer units you can often get a reasonably good response, for a small home studio. With 4 units it will usually be possible to fill all nulls in the response, and you can also - to some degree - control the direction of the sound field. With proper time alignment of the whole speaker system it will sound coherent with good transient reproduction.

This works because direction of low frequency sound is not audible or detectable due to tactile feel.


......

I usually come on this forum just to read, get some inspiration and input, and perhaps learn something new, because there are some very knowledgeable people around. I certainly do not have much to contribute with when it comes to room acoustics, at least not compared to @ DanDan here. But I know a thing or two about bass systems.

Hmm, thanks for that Kval, but I cannot accept that those who recommend multiple full range do not have a knowledge of how this works. I may try to find some of what I have read on this and come back and edit it in here.
Furthermore if a Kick drum with a leading blast is recorded accurately and played back on just one of those speakers, or even a pair, the leading blast will have a trajectory. It will blow out a candle. It will be felt on the skin facing it, not that on the other side of the body.
I have no difference of opinion as to how 'established' tone is handled. But a blast of air, a wave FRONT has direction and trajectory.
I am well aware of the benefits of multiple subs. But there are also benefits to multiple full range. https://gearspace.com/board/6450899-post14.html
Overall though, please remember that this side topic comes from a suggestion that LF Management be done at the Mastering Stage. I strongly disagree. https://www.youtube.com/watch?v=Qyclqo_AV2M


Mike, thanks for all those links and multitudes of big sized pics Mike. But you really didn't need to. Really. I am a qualified Electronic Technician, which comes with quite a high level of Maths. I met Mr. Fourier in the 70's perhaps before you were born. Crossovers etc. again absolutely no need to brush up on them here, and certainly no thanks to random Wikipedia knowledge.


DD

Dan,


We´re puzzled since you still seem to think that a low frequency sound wave produced by a normal speaker would be directional (and just to avoid possible confusion; we are not talking about the direction of cone travel, but the actual directivity of the speaker) and that you also seem to believe that low frequencies can be localized (in a normal listening room).

Even more puzzling is that you seem to think that the directional properties of a kick drum can be captured with one microphone and then reproduced by a normal (ok, sorry; two) speaker(s) …

Would you mind trying to explain how this would work?


Replying to post a you deiced to label "Ignorant" … When will the heading be included in quotes b t w?

I have repeatedly referred to the first cycle emanating from the Kick Drum, half of which predominates. I have been calling it a Wave FRONT. You keep restating 'Low Frequency Sound'. It is a bit off to refer to something I am not talking about in order to generate a false contradiction. In English we call this The Straw Man Argument.
The dominant half cycle is not a sound, it is a Pulse, a Blast. This is not exactly the same thing but illustrative enough if you truly don't understand my words. Try this. Say the word Pooooh. Hold your palm in front of your mouth. You will feel the Blast of the P but nothing from the sustained ooooh. That is the difference between a Blast or Pop Wave FRONT, which is clearly asymmetrical, and all other Low Frequency Sound.

That is an absolutely nonsensical misinterpretation of what I have said.
Again, I said that the above mentioned WaveFront will be represented by a full range speaker. Not the other directional property of lighting up the Room Modes differently with different orientations. Furthermore if that speaker is on one side, the direction from which the blast comes will be felt, and seen if a candle flame or piece of paper is in the path.

Sorry Jens I will not. All you need to do to fully understand is simply listen.
Play the first Half or Full cycle of an asymmetric Bass Drum Hit panned to one side only. Full Range Speakers no LF Management obviously. Remove everything above 80Hz if you wish. Close your eyes and get someone to pan the sound over to the other speaker. You will reliably identify the source every time. Ditto on headphones.

You haven't addressed the problem associated with headphone listening. Try listening to this on Cans. Note where the Kick is. Do you really recommend that the Mastering Engineer should make this Mono at LF?

I don't understand the last line in your post. I was referring to the practice of recommending educational material without knowing that the recipient was already familiar with it. I used the word both literally, blindly assuming such lack of familiarly is literally, ignorant. The second level of meaning is that suggesting such unfamiliarity while knowing this to be untrue, would be 'ignorant' behaviour. Sorry if it does not translate.

DD

So, just to be clear;

Are you saying that the sound of a kick drum cannot be broken down into separate sine waves and distributed to individual drivers/channels? What would Fourier say about that?

And that this would somehow explain that a kick drum reproduced by a normal loudspeaker would be directional even for low frequencies?

Or are you simply saying that low frequencies can be localized (in a normal listening room) even if all the current research says no?

You're welcome for the links but I didn't post any pics (big sized or not) so I'm not sure what you're referring to.

If you met him in the 70's, I'm pretty certain we're not talking about the same Fourier. Joseph Fourier (whom the Fourier transform is named after) was alive in the late 1700's to early 1800's. See link: https://en.wikipedia.org/wiki/Joseph_Fourier


I didn't think you understood the Fourier transform because you kept mentioning the asymmetry of the kick drum waveform as if it said something about the sound being produced by the subwoofers -- whereas if you understand the Fourier transform then you will agree that the asymmetry of the waveform indicates the presence of even-order higher harmonics and that therefore those harmonics are irrelevant to our discussion of low frequencies or their localization.

And I didn't think you understood how crossovers work because you didn't seem to understand that even if sub frequencies are converted to mono, the upper harmonics of kick drums, bass, etc., will be reproduced in stereo in the midrange/tweeters due to the use the crossovers.

Again: If following Jens' suggestion of summing low frequencies to mono, then only the low frequencies will be produced by both subwoofers. If the waveform is asymmetrical and there are higher order harmonics, then those harmonics will be produced in stereo in the midrange/tweeters and will contribute to localization, just as they would be if the low frequencies were not summed to mono.


I definitely have not previously seen your claim about localization of low frequencies via tactile sensations. I don't have a certificate from an acoustics institute, but I have read a little about localization and I've only read about Interaural Time Difference and Interaural Intensity Difference. The wikipedia on this is actually pretty decent: https://en.wikipedia.org/wiki/Sound_...uditory_system


Could you link me to any of your sources on sound localization by tactile sensation? Or, if it's original research, could you fill us all in a little? What frequencies does it work down to? How loud does the sound have to be to feel the pressure fluctuations? Is our perception influenced by the use of different clothing (heavy long-sleeved t-shirts and pants, for example)?

Oh yeah, forgot about that one:

Dan; Which Fourier are you referring to?

Perhaps you are referring to Nyqvist who was still alive in the early 70s?

Also, this whole discussion is pretty off topic relative to the benefits of implementing multiple sub-woofers to address room response vs physical bass trapping.

Would you be open/willing to create a new thread around the perception of the directionality of low frequencies?


Thank you

I have no problem accepting that others can have a different opinion on how to do bass management or not at all, and for mastering/studio I clearly see a dilemma here, still, the points I made have to be considered.

Another problem then is that the consumer playing back the program material mastered should have a similar set-up if reproduction as-intended is the goal.
If both systems are set-up with bass management this is much easier to accomplish.

Now, about the kick drum.

The leading pulse is a signal that consist of a wide frequency spectrum.
It may well be that the higher frequency energy makes the tactile perception different from different angles. I do not know, because I only tested for lower frequencies. Because at higher frequencies it is possible to create a directional soundfield such that the situation is the same as for free-field, so the problem no longer exist.

Close to the source the sound field will have very high particle velocity, but as you move away the properties of the sound field will change, and velocity relative to pressure drops. I doubt the drum will blow out a candle at a distance were people normally would listen.

I have never tried to blow out a candle, but I have no doubt it is possible close enough to the speaker. What I do know, is that sound with sufficient intensity and particle velocity certainly can be felt on the skin. And practical testing indicates that the direction of this sound field does not matter for the tactile sensations - at low frequency. Higher up in frequency, the situation may be different.

What we do know, is that higher frequencies can be localized. It is my belief that it is the higher frequency content that makes the drum possible to localize - if from hearing only or tactile sensation, doesn't matter. If this is the case, then the drum will still have the correct placement if lower frequencies are separated and played back on a one-channel bass system.

IMHO
A sweep or other kind of signal used to provide measurements and simulations are not the same thing than the music called dynamic regime.
The things are more complicated.
IMHO

As already mentioned, the P or Pop (in other words the transient) in your example consists of many frequencies ranging from subbass up to the higher midrange.

Mod mode:

Guys, keep it civil and to the point (no bickering). I don't want to have to edit or remove your posts.

Thanks!

I believe the argument we´re seeing here is due to two common myths:

1: The belief that we can localize low frequencies an acoustically small space.

2: The belief that low frequencies can have different “speed”/”attack”/”transient response”.

Once you lose these beliefs; you´ll also accept that it doesn’t matter if the sub 80 Hz or so frequency range, comes from one side or both sides of a speaker system in a room; the sound of a kick (or whatever) will still appear to come from the side that also reproduces the harmonics of the instrument recorded, and as long as the two sets of low frequency drivers are working together constructively (and not spaced too far apart and sweet spot is near the center line between the two woofer sets) and there´s no major modal problems in the room; the “attack” of the low frequency sound wave won´t degrade when being produced by two sets of woofers instead of one. As stated previously; there are only positives by letting more woofers (at least two sets, L & R) share the burden of low frequency reproduction since this results in less distortion (less cone travel per woofer needed) and a better modal situation due to the directivity accomplished by this arrangement (minimizing the excitation of modes related to width).

Am currently using 2 homemade 12" sealed coax mains and one 18" sealed sub on the floor. The sub is directly under the right main, at the same distance to the sweet spot as the two mains.

I want to add another 18" sealed floor sub under the left main.

While experimenting with various crossover settings, the "best so far" lowpasses the subwoofer 24 dB Linkwitz Riley at 500 Hz, with no highpass on the Mains 12" speakers. An earlier "good" sweet spot was symmetrical Linkwitz Riley 24 dB crossover of mains and sub at 80 Hz.

I was afraid that letting the single subwoofer extend so far into the mids would ruin the stereo imaging, but if so my ears are not good enough to know. I'm not real concerned with stereo imaging, but even rolling off the sub at 500 Hz, directionality is easily perceivable on mid-bass and low-mid instruments.

The 18" sealed sub acoustically begins rolling off above about 200 Hz but still has significant output at higher frequencies.

The 12" sealed mains begin acoustically rolling off below about 60 or 80 Hz but are strong enough to make some SPL below 40 Hz even if un-equalized. In a bigger room and louder listening level they would be strained in the bass. But at 90 dB nominal SPL, point-blank range in a small room, can be equalized flat down below 40 Hz easy enough even without the subwoofer.

Apologies the tedious description. Just saying, with low frequencies primarily coming from the sub but also helped by the two 12" sealed mains, it behaves SOMEWHAT like a 3-sub system. The bass EQ is relatively flat so that at low frequencies the sub is naturally louder than the two 12" mains, but the lesser amount of bass from the two additional speaker locations seems to help flatten the room bass frequency response. The low bass frequency response gets poorer if I highpass the 12" mains and rely only on the single subwoofer.

The reason I eventually adjusted the subwoofer lowpass as high as 500 Hz-- I have some ceiling absorption and such but had a fairly big null-peak pair around 400 Hz probably the fault of floor-ceiling bounce. Though the sub is not very loud up that high, careful placement of the sub lowpass frequency fixes that 400 Hz problem, probably by adding some extra energy from a different room location. Probably the same as the "multiple sub" bass effect, except at higher frequency.

Maybe this winter will find time to build the other sub under the left main. That along with the overlapping-frequency mains would be like a four-sub system, but dunno if it will significantly affect my most problematic 37.5 Hz null.

I had read about people overlapping frequency ranges between mains and subs and was earlier skeptical of the procedure. For one thing, it would require mains strong enough not to rattle and distort if driven with low bass. But maybe one of the reasons it could be beneficial in bass and even low mids, would be the "multiple speaker" smoothing of room modes?

Sorry evosilica, my point is not clear to you. I was trying to point very directly, pun intended, to the blast of air. I deliberately wouldn't call it a transient, just to keep it distinct from the transient say at the start of a cowbell or whatever. No air blast.
Put it another way, the skin can identify this blast, and it's direction by the absence on the other side of the body part. This is separate from the sonic issue.

Indeed there are many, same in Mixing. Do we mix for iBuds or Speakers? The difference is vast.
But the notion of taking a Mix where someone has deliberately panned LF elements to the side, typically two complementary ones, and making it Mono in Mastering, doesn't seem wise to me.

Obviously I didn't meet Mr. Fourier literally, that is just a metaphor intended to indicate a course of study a long time ago.
I will not deal with the other similar comments, they strike me as disingenuous.

I will however deal with the suggestion that my auditory experience is Myth.
I am going to state this one last time, and then hope that Thomas request is honoured.
Beater hits Kick Drum head. Pushes it quite far in one direction. If the beater is released instantly by a drummer with such a great technique, i.e. me at a live gig in the presented waveform, the skin rebounds and then settles down to oscillating with a lower frequency tone. The waveform presented (yet again, this debate is a repeat) has blatantly higher levels in one direction. A blast of air results. A one directional blast of air with a trajectory. It will out a candle near the drum. It will be felt on the skin on the side of the body exposed to it, and not on the other.
The resources to prove this fact or Myth are available to most of us here.
If not, PM me and I will send you say just the first asymmetrical half cycle or the whole sample, whatever you want. Filter out all above 80Hz, play with it. Definitely try it played by one speaker only or panned entirely to one side.
Depending on how loud, how close and how full range the speaker, one will feel the blast on the skin of the side of the body presented to the source. They sound will be reliably locatable by ears. Although everything above 80Hz has been removed, there is generally quite a lot of harmonic distortion in LF speakers struggling to cope with this stressful impulsive, asymmetrical, tonal and rich in harmonics, source. Also port noise....
There is a difference between the hypothetical, or idealised to unreal simplicity, situation
A Kick drum coming from one speaker sounds different to coming from multiple. There is no Myth.
On consideration, I do think this very particular instance, the Kick Drum, is pertinent to the Topic here.
It is very common and if it sounds different on a LF managed system to multiple full range we have to make a choice.
I will try to find the some of what I have seen written promoting the multiple full range option, just for some balance.
The benefits of LF management are well known, but there are other views. And let's face it really full range 5.1 has well, 5 subs.

DD

Since you're now appealing to harmonic distortion and port noise as the source of our ability to localize subwoofers, I take it that you're tacitly conceding the fact that the low frequencies themselves are not localized.

The ability to localize subwoofers due to their nonlinearities is exactly why people produce subwoofers with as little nonlinear distortion as possible.

You also keep bringing up asymmetrical signals.

So I will say once again, since you have never dealt with this point, that asymmetrical signals necessarily contain even-order harmonics. This is a basic fact of the Fourier transform.

It also occurred to me that your overall position on this thread is inconsistent. In post#2 on the first page, you say:

Yet in the last few pages you're claiming that sub frequencies are easily localizable and that a mastering engineer should not mess with the artistic intent of the producer/engineer by summing sub frequencies to mono.

But if sub frequencies are localizable and using two subs instead of one will cause great differences, how can you possibly advise the use of four subs when the engineer/producer (in virtually all cases) was not intending the recording to be heard on four subwoofers?

If low frequencies are in fact localizable in the way that you claim, then using 4 subwoofers to reproduce 2-channel audio would amount to listening to stereo audio on a quadrophonic system at low frequencies, with all the problems of localization that entails.

I think it´s the other way around: Evosilica’s point is not clear to you. Again; if you understand the concept of Fourier transform; you would understand why your “point” doesn’t make sense.

If the null at 37.5 Hz is due to a mode related to length, then no; adding more subs at the front wall won't help at all. If due to width, then yes; it might help (as described earlier in this thread).

When we say that for example 50Hz is not locatable, I think it's important to realize what 50Hz is:
A continuous and pure sine wave with 50 cycles per second. nothing else.
Everything that differs from that is not solely 50Hz anymore, but a wide sprectrum, that can cover the whole audible bandwidth and beyond, depending on how much it differs from a pure sine wave. "Air blast"*, pop, transients, asymmetry, all that means that there's more frequencies involved than the fundamental frequency. And those higher frequencies can of course be locatable. But a subwoofer is not responsible for reproducing them.

*(I guess what you mean by "air blast" would be subsonic/infrasonic, therefore filtered by the recording/mixing person, or if not, it won't be reproduced by most speakers anyway)

Steve,

Were all subs , Behringer, JBL, and the Subwoofer Pros, positioned in the same points in the room when tested? Was this location point the 50% spot on ALL walls? Or,, did you find different locations for front-back v/s side wall-LR locations?

And finaly, did you really put Qty. 4 Subwoofer Pros 12" in that 10x14x8 room? That could send you to the dentist if you have a loose filling.....lol
Not to mention, that's nearly $10,000 in subs once cabled up.

Thanks,
Joe

You understand my point now evo. I did repeatedly tried to describe the difference between this wave FRONT or Blast versus LF Tone etc etc
One could call it InfraSonic, but I don't think that quite fully describes it.
It occurs as half of a cycle, a very asymmetric one. Note that in the presented waveform it is the second half. More often it is the first half cycle if I remember correctly.
So does one cycle describe a frequency? If so the one in the waveform present is about 60Hz afaik Not ELF then.
One could claim it won't be represented by most speakers, who knows? My three sets certainly do.
One could simply say it doesn't matter, who cares about the Blast at the start of a Kick hit. Again, who knows, apart from personally. I would regard not representing this as a flaw in the transmission medium.

Irrespective, the phenomenon is generated by the player and instrument. It is recorded. It can be reproduced by decent speakers, one can see the cone movement and feel the air blast.
The asymmetry may well cause or increase harmonic distortion, which would allow it to be hypothetically heard.
Interesting that some here now accept that it 'could' be locatable as coming from a particular speaker, by addition of a simple, I presumed well known, theory. If the theory of harmonic distortion has been deliberately omitted to make the point that reality cannot be happening, we have a very very odd situation here.

Focussing on Theory can blind people to a reality, to the point of not even testing it.
Not a single person has posted that they have tested this and not been able to locate the single speaker playing the Kick.
Note that there has been a similar nonsensical debate previously on whether a Bass Drum is directional in a room. Ultimately the recording presented seemed to quieten the noise. But it is clear from the repeating here, that theoretically, reality has not been accepted at all.

Let us not forget the headphone listener, making Mono below 80Hz would be a serious interference with the Mixer, Producer, Artists, intentions.


Now, I have found one of the sources which advocates full range speakers rather than Sat and Sub.
A Grammy, I presume NARAS, sub committee consisting of the following audio pros.
Chuck Ainlay
Joe Chiccarelli
Bob Clearmountain
Frank Filipetti
Leslie Ann Jones
Rory Kaplan
Jeff Levison
Bob Ludwig
George Massenburg
Howard Massey
Hank Neuberger
Phil Ramone
Elliot Scheiner
Eric Schilling
Al Schmitt
Jeff Skillen
Paul Stubblebine


http://www2.grammy.com/pdfs/recordin...rs/5_1_rec.pdf

DD

I think I have an idea on how you view this topic, but I disagree. I think fourier has proven to be correct and it's not really in acordance with your explaination.

It absolutely does not. As I've said, anything that differs from a continuous sine is a mixture of several frequencies.
I've attached the spectrum of a continuous 60Hz sine wave and a single halfwave of a 60Hz sine. You can clearly see that while the continuous wave has only one peak, the halfwave has a wide spectrum having significant content at 1kHz and ranging down to DC. So it has indeed ELF components, that maybe cause the air blast you have mentioned, but no speaker can reproduce them. I have a fullrange system with 2 15" woofers going lower than 20Hz, but it still wouldn't exactly reproduce it. In fact it could be potentially damaging the speakers, so I have a subsonic HPF for such (rare) cases.

I think noone ever disagreed that a normal kickdrum is locatable. But it's only the higher frequency content that is responsible for this, not the low frequencies.

I think fourier perfectly lines up with reality.

I partially agree with that. If it's the producer's intention to place low bass to one side, then so be it. But I think it's a very bad practice, firstly because of what Jens mentioned (mono bass = both drivers work equally = less distortion) and secondly because on headphones I personally think it sounds very uncomfortable to have bass comming from one side only, kind of like overly wide bass (out of phase) sounds uncomfortable, too.

Thanks Jens

The 37.5 Hz null seems almost certainly due to width, but dunno if two front floor subs under the mains will help. Am curious to find out.

The room is 15 X 11.5 feet, but the 15 foot dimension is the front wall. The rear wall is 40 percent open into the rest of that floor of the house via two always open doorways, so the 11.5 foot front-to-back room modes are not very strong, and the bass trapping is thick enough that it seems to work "fairly good" in those higher frequency ranges.

I can't put thick wall trapping directly to my left and right because the room is too small and such trapping would block an exterior door and equipment access. There is enough front, back, ceiling and corner trapping that I suspect the remaining "not total" 37.5 Hz null might be more similar to side-wall SBIR than a resonant modal null. Decay time is longer than desirable below about 60 Hz but am guessing the null may be more the fault of early side-wall reflections rather than a long series of undamped wall-to-wall reflections. After the first couple of side-wall reflections, the corner trapping and big holes in the back wall ought dissipate a good bit of the longer decay.

I enjoyed your images of "no back wall" wave tank simulations with 1 vs 2 front wall woofers. That might be the result of two subs under the mains in my room.

A "sidewall first reflection" interpretation, dunno if it is flawed-- Very approximate figures-- For instance in a 15 foot room width, with a single sub on the front wall, 3 feet to the right of center, and listener in the left-right center only a couple of feet behind the speakers on the front wall-- The right wall first reflection would be delayed a distance of about 12 feet to the listener, phase shift of about -144 degrees at 37.5 Hz. The left wall first reflection would be delayed a distance of about 18 feet, phase shift of about -216 degrees at 37.5 Hz. If both side wall reflections are about the same amplitude, they would sum to a phase of -180 degrees at the listening position.

The direct sound of the subwoofer, delayed about 3 feet from sub to the listener would be phase shifted about -36 degrees. A direct vs reflected phase difference of about 144 degrees at listening position.

With the single sub placed 3 feet to the left of room center then the same phase relationship would hold, except in mirror-image. Left wall reflection phase-shifted -144 degrees and right wall reflection phase-shifted -216 degrees.

I had been thinking that placing two subs equally spaced from the front wall center would therefore have the same problem as only a single sub. The doubling of the same flaw yielding the identical flawed result. But maybe am thinking about it entirely wrong, which is not unusual. If I build another sub will find out. It ought to sound "better" with two subs even if it doesn't fix that null.

The results I posted were all the same locations of 4 subs at midway of all 4 walls. We also tried several other 2 and 4 sub locations but for music production this has performed the best overall. We had 2 Subwoofer Pros that were available temporarily due to a delay installation at a studio my friend was building for a client. They sounded great and performed incredibly well with one front and back wall at 50% points

No teeth were harmed

I am sorry and a bit saddened that anyone could think that evo. Quite often when we do pan LF elements there is a complementary one on the other side. I am very proud to have Produced, Mixed, and Mastered these.
https://www.youtube.com/watch?v=lFR3cUW7ogA
https://www.youtube.com/watch?v=EWWenAbeYW8
The first has cellos and bodhráns (celtic hand played frame drums)
Probably best heard on headphones the panning of the LF elements causes deliberate and very substantial shifts in the sound field. On full range speakers it stimulates great action in the room, LF action.
The second has two bass guitars, same instrument and player. Some panning was needed to distinguish them and to again cause colourful substantial shifts of the LF part of the field.
Particularly in the first making below 80Hz Mono would be very destructive.

Again, anyone with full range speakers and Kick drum samples can easily test this. Not a single poster here has challenged the fact that a single speaker trying to represent a Kick sample with everything above 80Hz removed, is reliably locatable.
Please note that my reference to any earlier debate, bickerfest to be frank, had one of the posters here absolutely insisting that a Kick Drum was Omni. Didn't matter which direction it faced. The recorded sample I posted proved otherwise.

I do think it is both possible and likely that the committee of people who have made some of the worlds greatest recordings may have good reason to hold such a strong opinion regarding the preference of full range speakers. I hold two opinions on the matter, well recognising the benefits of multiple subs.
However, as I said before, a 5 channel system of full range speakers has 5 subs. Although they be not optimally placed to garner the LF benefits nicely shown here by Jens etc, I quite like listening to stereo material in 4.0, full range speakers.
DD

Now you're just making stuff up. Myself, Jens, evosilica, and Kvalsvoll have all challenged your claim that frequencies below 80Hz are "reliably locatable".


No Dan, people have noted that the directionality of a kick drum is irrelevant to a discussion of stereo reproduction, since that directional information is lost. The directionality of a grand piano, for example, will not at all be represented in the playback of a grand piano on a speaker system. This is so basic to the theory of transducers that I'm amazed that you're disputing it. You may want to consult Wikipedia again: Directional sound: Basic theory.

One of the most relevant sections:



You have never explained why listening to stereo bass, intended for stereo reproduction, should not be played back in mono since it will distort the producer's intentions but for some reason they can be played back fine on four speakers. If low frequencies are "reliably locatable," as you say, playing back low frequencies with four subwoofers will drastically mess with the producer's intentions!

I agree that a well designed and implemented full range system is ideal. The mulitple sub-woofer approach, in the vein of the Harmon research, is a purely practical solution to severe low frequency anomalies in small rooms. In a perfectly treated full range room multiple subs, in the vein of the Harmon research, would be completely unnecessary.

The challenge is that a very large number of people record, mix and produce music in small rooms which by nature have low frequency issues that often which exceed what can be addressed with practical/affordable acoustical room treatments.

Just to try, I played a song, put a 24dB/oct LPF at 60 Hz and panned it to the left. I could easily hear the bass frequencies coming from the left speaker. This was in my untreated small bedroom. However when I played a sine wave of 60 Hz in the left speaker I couldn't hear where it came from. Only if I leaned in towards the speakers I could hear the sound coming from the left. Probably cause of the volume difference.