SME

I can agree to your first statements, but I'm confused by what you mean in bold here. Do you mean to say that there are many more unfiltered movies than it appears because many movies are not measured here? Yes, good surround mixing is a big plus too, as well as is overall better tonal balance, which also has a big impact on the perception of both bass and ambiance.

I think "How to Train Your Dragon" should be near the top of the list for ULF as well, and it's also a pretty good movie if you like family / animation. Some would argue it's tilted toward the bottom a bit too much. The movie is full of ULF, but one noteworthy scene is maybe 1/3 of the way through in a large hall with a lot of thunder and a big door slam. That door really gets the air moving and is very noticeable because it is an isolated effect. Another animated movie with great overall bass and plenty of ULF is "9". It has many good effects. Among my favorites are the scene about 1/4 of the way through which bombs being dropped and huge mecha stomping around. A good one-off effect is the firing of the artillery near the end. The Dolby Atmos trailers I'm familiar with don't have a lot of ULF, but there are a few minor moments. In "Amaze", the "thundering bass" scene has some 14 Hz. I think it also has some 16 Hz at the very end. IIRC the leaf demo also has some 16 Hz at the end but nothing else. The "Horizon" demo has a few moments with moderate ULF, but it's completely inconsistent. The "Unfold" demo actually has good extension but isn't especially loud. Unfortunately, the trend with newer movies seems to be more filtering. A handful of us are able to work around this issue by re-EQing the soundtrack before bass management. Other than "Hacksaw Ridge", another recent Atmos mix that has ULF is "Wonder Woman". Even though most of the content is above 20 Hz, there's enough below 20 Hz to matter and the bass overall is top notch IMO.

Hmm, I think I could could do this pretty easily actually. The drivers are in isolated chambers, and they are wired in parallel. All I have to do is disconnect the SpeakOn on one side of each, I think. The only issue is that the gap between them and the wall may not be big enough to cleanly disconnect the cables, and I'm not willing to pull them out from the wall because the speakers are on top and are precisely aligned.

You know that this project *obligates* you to play some proper Hammond organ music with the bass 20 dB hot from time-to-time after you are finished, right?

I think it's helpful to distinguish between direct vibration transmission that's a problem, where a sub is rattling against the floor or not staying in place, and vibration transmission that is not a problem but still contributes to tactile feel. I was honestly very surprised by how much tactile feeling I gave up going from the old pair of single-driver ported subs to D.O. sealed subs. Partly as a consequence, I'm running my bass quite a bit hotter than I used to. I know I'm not alone here either. I've seen people on AVSForum report similar observations. Then there was that crazy guy who purposely ran his HS-24s free air for a while and reported all kinds of infrasonic shaking effects, which were probably entirely from vibration instead of SPL, and actually did damage his house. FWIW, the ported subs were on rubber feet and at high output definitely shook a lot. I recall once or twice putting a glass of water on a coaster on top of the Hsu VTF-15H sub while it was playing the low organ notes in the Saint-Saens Symphony and marveling at the patterns that developed on the surface of the water. This didn't happen with the glass placed on any other room surface. By comparison, the new subs are inert except at the few frequencies (i.e. 11 Hz and 19-24 Hz) where the floor under them shakes, and only then at higher SPL than it used to take. It's possible that @Kvalsvoll 's testing involves a floor that's firm enough to resist most direct transmission, and the fact that he's testing with horns probably means more SPL vs. vibration from the same drivers. Another thought is that multiple subs spread out may exhibit more or less vibration depending on how they combine in the air vs. combine in the floor system. There are lots of variables here.

I did my force analysis for a sealed box sub and found the results interesting. Keeping SPL constant, the force is essentially frequency independent. I'm curious how it would change for a ported sub and/or horn sub, but those would be a bit harder. My guess is that the ported subs would get a bit more SPL vs. force near tune, and the horn would get more SPL vs. force in its prime range. I'm not exactly certain though. A more complex analysis would look directly at the force balance on the moving vs. stationary assembly of the driver, which must take into account motor force, back EMF effect, and the differential pressure on each side of the cone. For a sealed box, the latter is quite trivial to evaluate, but the situation is much more complicated for ported boxes and horns. As for neighbor complaints, a lot depends on the circumstances. If the house units are detached, it's likely to be relatively high frequency bass that's more offensive. Content at around 100 Hz is relatively easy to hear at low levels and often passes very efficiently through walls and windows. I believe some triple pane window designs can be even worse because the middle pane acts as a resonator. I once worked in an office in which the windows had a strong resonance at around 100 Hz, which was very annoying at times. Thunder tended to create a very loud tonal sound, and I recall one day in which a lawn mower being operated hit the resonant frequency and was annoyingly amplified.

The Auralex products are probably the most popular for subwoofer and speaker "isolation". Most products I've seen marketed for audio use are very similar. At least we agree that such products are not capable of working as advertised. I'm still skeptical about the foam blocks you describe, but without data I can't know for sure either way. And even if they are providing isolation, it's possible that your floor is just more resilient to direct transmission. Perhaps the floor vibration you do measure comes mostly via the walls, which may be made to vibrate by the sound alone. I do think there is potential for a sub isolation system, one that actually works , to reduce unwanted vibration and possibly reduce neighbor annoyance. However, the approach will be hit or miss. It's going to depend on the details of the construction and how vibrations induced directly vs. via sound are transmitted throughout the structure. And because an effective isolation system is likely to be impractical, expensive, or both, it makes much more sense to opt for D.O. subs if possible. I did that, and I unquestionably (albeit by subjective opinions of myself and others who experienced before vs. after) experienced a substantial reduction in structural vibration, even though it was not eliminated completely.

The assumption in bold is stated above and in the article as *unquestionable fact* without any evidence or theoretical physical analysis to justify it. The rest of the conclusions are based on that unverified assumption being correct. However, my argument is that foam products do not provide good low frequency isolation, and I stand by that argument. Do they? I have never seen such a specification published for any isolation product targeted to the audio market. For example, the spec sheet for the popular Aurelex Subdude HT-II platform claims to "decouple your subwoofer from the floor" but does not give any quantitative performance specifications whatsoever. No platform is capable of providing total isolation at all frequencies, so without quantitative information, it is pointless to try to evaluate their claims by looking at the specs. Now, if you want to see a legitimate example of a vibration isolation solution, checkout the offerings from minus k technology. The embedded video is a very cool depiction of what their tech is capable of. Also read their application list where you'll find many examples of applications where working vibration isolation is critically important. Note that audio does not appear on the list, which is not to say that audio is not necessarily a useful application. It's just that unlike audio in which products that don't work still manage to sell well because of placebo effects and a misunderstanding of physics ,the applications listed depend on tech *that actually works* with consequences that are obvious if it doesn't work. Note that their product also includes proper engineering test data compared to another legitimate but lower performing competitor's product: Read the fine-print concerning the test procedures, and you will learn that the test platform is supporting a weight of 650 lbs. Note that I'm not trying to endorse the above product over others that may be available. I'm merely giving an example of a legitimate vibration isolation product, to contrast it with the fake products being peddled by multiple vendors to the audio marketplace. It's not even a matter of advanced vs. basic science. It's a matter of science vs. pseudoscience. Likewise, without data or at least some theoretical justification, it's anyone's guess how well any particular product (including the foam you are using for your tests) performs in reality. As I've said many time, foam is a poor low frequency isolator, and in all likelihood, the foam used in your tests provides near zero isolation at the low frequencies of interest. ****** I will add that I have directly witnessed evidence of subwoofers transmitting vibrations directly into a floor. I already mentioned my experience going from front/side-firing single driver subs to D.O. subs, but I observed much more dramatic effects when free-air testing my new 21" UH-21v1 drivers. For the test, I placed a single driver face up on my living room floor and fed it sine waves at varying amplitude and frequency. In free air, the driver produced very little actual sound below 60 Hz or so, but vibration levels rose rapidly below, down to an apparent peak at 30 Hz. At 30 Hz, the vibration was alarmingly strong with even a tiny amount of input power (i.e. < 1 W). The vibration was transmitted efficiently throughout my the structure of my house. I could hear my attic vents rattling, which means that neighbors could probably hear the noise if they were outside. If I fed that sub more like 1000W to take it to Xmax, I fear I would have caused actual structural damage! In contrast, after installing the driver in cabinets in a D.O. configuration, there is almost no perceivable vibration at 30 Hz, even at very high levels. At such high levels, the sound still creates a sensation, but it is that strong "back massage" sensation with no shaking whatsoever. It is a completely night-and-day difference. ****** Lastly, let me support my argument for direct vibration transmission further using an analysis based on actual physics. The force that a subwoofer motor imparts on the cone is always matched by an opposing force on the "stationary" parts of the driver, which is also transmitted into the cabinet that the driver is mounted in. In a D.O. configuration, each driver contributes opposing forces on the cabinet which cancel, so there is no force imparted to the floor. Otherwise the cabinet itself experiences a net force from the driver(s), which must be canceled by a force from the floor in order for the cabinet to remain stationary relative to the floor. So if the cabinet is not D.O. and is well anchored to the floor (not hopping or walking), the cabinet *must* be transmitting forces into the floor. The direction of these forces depends on the orientation of the driver(s). For up-down firing, the force will act perpendicular to the floor. For front-firing, the force will act parallel to the floor. Either way, how the floor reacts depends entirely on the properties of the construction and crucially, the magnitude of the forces involved. So let's talk about these forces using real quantities. For brevity, I will give a formula that relates the force between the moving assembly and the rest of the driver (let's call it the "recoil force") in terms of SPL at 2 meter ground-plane for a sealed cabinet operating under far-field conditions. For a single driver sealed system, this is the force that will be transmitted to the cabinet and to the floor. This can be readily related to measurements published here on DataBass. Upon request, I'm more than happy to show a detailed derivation of the formula below. It is derived using "Newton's first law of motion", the relationship between driver acceleration and SPL at a distance, and the definition of SPL in terms of pressure: Recoil Force = (0.000411 m^3/s^2) * 10^(SPL_@_2m_GP / 20) * Mms / Sd For unit consistency, Mms must be specified as kg and Sd as m^2. As general points of interest note that for a given SPL, higher Mms increases recoil force, and higher Sd decreases recoil force. Let's throw in some typical numbers and see what happens. For example, we'll consider output of 120 dB SPL RMS at 2 meter GP from a "typical" deep-bass 18" driver with an Mms of 0.75 kg, and Sd of 0.120 m^2: Recoil Force = 2570 N = 578 lbf These are RMS numbers. The respective peak quantities are 3630 N and 817 lb. For a down-firing configuration then, imagine a 1634 lb (740 kg) weight (doubled because of peak-to-peak difference in force) being repeatedly added and removed to the location of the sub and you get the idea of how strong the forces can be. This is another reason why stout cabinet construction is important, not just to maximize efficiency of the driver(s) but to also maintain cabinet integrity at high output levels. Of course, 120 dB SPL @ 2 meter GP is running things pretty hot (max capability for a lot of 18" drivers), but the forces involved are still significant at lower levels. For example, at 100 dB SPL @ 2 meter, 20 dB less, the forces will be 1/10th as much, which is likely to still be enough to vibrate a suspended floor. ****** So to summarize, direct vibration transmission between a cabinet and floor can be quite substantial and almost certainly contributes noticeable vibration in addition to the vibration induced by the sound itself. This transmission occurs even if the subwoofer appears relatively motionless. If the subwoofer is actually visibly moving, the low frequency vibration transmission may be reduced, but the repeated collision between the sub and floor will create a lot of unpleasant high frequency rattling noise. And of course, a moving subwoofer is potentially unstable if it's part of a stack. Reading other threads here, I know @Ricci has reported that "sub walking" can be a serious issue in a pro setting where they are often pushed to peak levels for an extended period of time. The real reason that sub isolation platforms fail to reduce vibration is that they don't work as advertised. While foam can prevent the unpleasant high frequency noise that occurs when a vibrating sub or speaker rattles against a floor, it does little to isolate the low frequency vibrations of the sub from being transmitted directly to the floor. An apparent lack of visible motion is useless as an indication of isolation. In fact, an isolated subwoofer will move *more* than one that is not isolated. That's because in order for the forces transmitted to the floor to be zero, a net force must be acting on the cabinet, which will cause it to vibrate in-place instead.

I agree with you that subwoofers induce vibrations in room surfaces via transmission of sound through the air; however, most subwoofers also transmit substantial vibrations directly into the floor. Just because the subwoofer is not visibly jumping up and down does not mean that it is not transmitting oscillating forces into the floor. My experience transitioning to dual-opposed subs suggests that this contribution may be very substantial. The problem with devices that claim to decouple subwoofer vibrations from the floor is that they don't actually work as claimed. I wouldn't put any trust in a device that does not come with engineering specs. Such specs should indicate in a table or plot: percentage isolation (or "tan-delta" or "loss coefficient") vs. frequency vs. mass applied. A good isolation system will isolate the object well for frequencies well above the system natural frequency and relatively poorly at and below the natural frequency. The natural frequency depends on the mass of the object to be isolated. I'm not aware of any isolation product targeted to the audio market that includes this information. Therefore, I doubt that any isolation products marketed for audio actually do what they claim. Good isolation systems typically follow one of two different approaches. For lower mass objects, the best isolators are made using viscoelastic polymers. Rubber is often described as viscoelastic, but this is not really accurate. Rubber is an elastic solid but is not viscoelastic. A viscoelastic material exhibits the viscous flow property of liquids in addition to be elastic like rubber. The viscous properties are necessary for damping within the material to occur, which is necessary to reduce energy transmission through the isolator near the natural resonance frequency or at harmonics. For higher mass objects (usually things more massive than subwoofers), a system using springs and/or hydraulic dampers may be used. An example of such systems are seen in the suspension systems of cars, which help isolate high frequency (but not so much low frequency) vibrations of the road from the rest of the car. Another example are the kinds of systems used to make buildings earthquake safe by decoupling the buildings from the high intensity ULF vibrations that occur during such events. When using viscoelastic polymers for isolation, both the material and geometry must be optimized for the application, which depends on the mass and shape of the object to be isolated and how low in frequency the isolation should work. The material itself must be optimized to provide sufficient rigidity but retain sufficient damping capability within the temperature range of interest. The natural frequency of the elastic system depends on the inherent stiffness of the material (technically the Young's modulus and shear modulus), which in viscoelastic materials is frequency dependent. It also depends on the geometry of the isolator. The geometry is very important because it affects how the weight is distributed throughout the material and how the material deforms around it. A large slab of material, as is typically found in commercial products spreads the mass over a very wide area, and therefore tends to have a very high natural resonance frequency. This means that such products don't really isolate low frequencies at all. An effective viscoelastic low frequency isolation system will typically consist of one or (usually) more isolators that have a geometry that's relatively tall and narrow but not so much as to be prone to buckling or other kinds of mechanical failure. With proper design and optimal material choice, it is possible to provide good isolation for objects to as low as ~10 Hz, which is quite useful for decoupling subwoofers from a floor. One viscoelastic material that is relatively easy to obtain but is rather expensive is called Sorbothane. It is an engineered polyurethane material available in several different hardnesses. The manufacturer publishes engineering guides from which one can estimate the properties of a system in order to choose the optimal hardness and geometric design. I actually use small squares of the stuff under my speakers to get ~ > 30 Hz isolation, and it works. The material can be bought as sheets, strips, feet, and other forms for different applications. While other materials exist with similar damping capabilities from specialty manufacturers like 3M, I'm not aware of how to obtain them easily without purchasing them in extremely large quantities. Anyway, sorry for the long post, but I just want to clarify the nature of the myth. Subwoofers do transmit vibrations directly to the floor. The myth is that the isolation "slabs" sold for speakers and subwoofers actually do something, when they don't (at least for low frequencies). Nevertheless, isolation *is* possible with a properly engineered system. It can get expensive though. Often a better option is to build a dual-opposed sub design. Keep in mind too that vibration isolation may also be useful for video projectors installed in rooms with heavily subwoofer induced vibrations.

I have no idea about the actual movie, but the "Pacific Rim Uprising" trailers have some serious infra bass.

A big caveat here is that the response of phone mics is a big unknown. I have a Google Pixel XL, and I recently installed an SPL meter / analyzer app. I figured it'd be helpful for a quick SPL measurement while playing music, without having to get up and go get my SPL meter. The app is pretty comprehensive and allows selection of Z-weighting for flat response, in the app at least. Unfortunately, the mic on my phone seems to have much diminished response in the sub range and also has poor dynamic range. IIRC, it taps out in the 80s dB, which is pretty much useless for measuring music that's loud enough to be fun. The sub response on the phone seems to be bad enough that it'd be useless for doing sub measurements. I wonder if they high pass it on purpose to improve speech clarity and reduce unwanted clipping? Oh well.

I agree that there should be no advantage to SBA/DBA solutions, provided that "you can manage to somehow get rid of the cancellation reflections", or otherwise remove the effects of the room using another method. In both cases, one achieves very smooth (near-anechoic) bass frequency response (when viewed without using smoothing) across a wide region of space. I don't have an SBA/DBA, but I do have DSP-optimized filters to achieve the above near-anechoic ideal. This condition is maintained up to about 65-70 Hz, above which I have multiple issues preventing me from maintaining an completely smooth response. This is probably an issue in most other types of near-anechoic sub systems, including SBA/DBA also. To be honest, I wasn't expecting to have to go back and shape the broad response by ear the first time, and I was even more surprised when I had to shape the broad response *in a different way* after I re-did it with new crossovers. More recently, I did an EQ overhaul of my mains speakers above 160-200 Hz only, and I had to re-do the broad shape of the subs *again*. These weren't minor changes either. Whereas before, boosting below 40 Hz even 0.25 dB caused the bass to go to mud, with the latest config, I was able to boost the low end by several dB without loss of intelligibility. So at this point, I'm not convinced that any particular way is better than another. If anything, my work with mid and high frequencies has convinced me that some early reflections are better than none, provided that the speaker is well-behaved. The main reason so many pros are convinced that early reflections are bad is because they are experienced with using monitors with poor off-axis response, and the elimination of early reflections prevents that nasty off-axis sound from corrupting the better on-axis sound. With good speaker design, that's no longer an issue. It does lead me to wonder if maybe early reflections are good for bass too, to a point. It appears to be well established that modal resonances have negative perceptual consequences, but do early reflections have as much impact as we think they do? We practically hear through early reflections for mids and highs. We may also do so for bass, but it probably depends on how much reflected sound energy there is in total and how well it is distributed in time. At lower frequencies, there is definitely a propensity for the sound field to become quite structured within the room, even if discrete modes are not obvious. This is a substantial open problem that I plan to devote more time to in the future. I would strongly caution anyone not to read too deeply into frequency response data. Because we hear pitch (frequency) and level, it is easy to assume that a frequency response (FR) plot tells us how different pitches will be emphasized, relative to one another. However, this is far from the truth. An FR plot with smoothing is largely meaningless because the smoothing discards most of the information that's relevant to perception in the first place. An FR plot without smoothing and with phase data does contain that information, but it is a terrible visualization of that information. Time-frequency plots like waterfalls and spectrograms are kind of a step in the right direction, but it is hard to glean quantitative information from them and the information within them is still not weighted very close to how perception weighs the information. All of this makes sense if you imagine what it would take to analyze an IR to determine the true spectrum of a source within the room. One must deal with a variety of acoustic interference effects and possible obstructions in the path of the direct sound. It takes some very clever processing in order to accomplish this with the accuracy that our ears and brain do. As can be seen, I'm rather short on good advice here. I am less confident in what I know about bass reproduction than I ever have been, having tried a variety of strategies and having failed, in the sense of not achieving any consistency. And that's just in one room. And this is yet another reason why I am very skeptical of the relevance of particle velocity, independently from pressure. Why? Because there's so much we don't understand about how pressure response affects perception. Unless or until one constructs an experimental apparatus in which velocity response can be varied while keeping pressure response *exactly the same*, no one has proven anything with regard to the relevance of velocity response. In practice, this kind of test is extremely difficult to do. Almost anything that changes velocity response will change pressure response in some way. "Close" does not cut it here.

Of course the boundaries of a real room are not perfectly rigid. They are lossy, especially at certain mechanical resonance frequencies. Your room is also open at the rear. However the side-walls, floor, and ceiling are rigid enough that the sound field between those dimensions is qualitatively similar to what I described. Pressure still peaks at the boundaries where velocity drops to almost zero, and there are likely dips at certain frequencies . My point is that the effect of multiple subs on your velocity measurements is entirely consistent with this perspective. I don't know what you mean by "intensity pressure". If you mean merely pressure, then we are in agreement that pressure is the most important characteristic for transmission of vibration from the air into the body of the listener. The proposition that the motion of clothing depends on velocity is interesting, but I suspect the situation is more complicated than that. It may have more to do with pressure gradients, which may coincide with areas of high velocity as it does for standing wave sound-fields, but high velocity and high pressure gradients don't always present together. It would be interesting to do some experiments with subs outdoors to see if clothing movement perception is affected by source distance, while pressure is kept constant. In the far-field of a monopole radiator, pressure and velocity both drop with 1/R, but the pressure gradient drops with 1/R^2. Thus, if what I suggest above is true, we'd expect less clothing motion at greater distances, even after compensating for SPL. To your point that frequency response and phase are very important, I totally agree, but I would say it's a lot more complicated than most people think. And of course, the sub range is only one part of the picture. The rest of the speaker response also impacts perception a lot, and 100-500 Hz is particularly important for tactile sensation. Unfortunately, this range is often harmed by speaker placement problems, but there may be ways to fix this with EQ. This is work in progress for me, but I can say with confidence that a perfectly flat or smooth in-room response is not optimal unless the room is completely dead. And if the room is completely dead, then you have another problem.

So if the listening position is approximately half-way between the two side-walls and approximately half-way between the floor and ceiling, it makes sense that you see a lot of velocity along those dimensions with a single sub. The 1st order room mode contributes pressure peaks at each boundary and a pressure null in the middle. For velocity, the reverse is true with a velocity peak where each pressure null is. When you place sub(s) at opposing boundaries across a particular room dimension, they cancel the mode, leading to a much more even distribution of pressure and near elimination of the velocity vector in that dimension for those frequencies. More generally, where standing waves dominate response, the particle velocity at a point in space is usually proportional to the spatial-gradient of pressure, i.e., the rate of change of pressure with respect to spatial location. (This is more or less the same as saying that they are separated in phase by 90 degrees because [math alert] the derivative of a sine is a cosine and the derivative of a cosine is a negative sine, and so on.) The pressure gradient is actually highest in the nulls (it quickly rises in either direction), and velocity peaks here. In contrast, when approaching a rigid boundary, the pressure gradient in the direction normal (i.e. perpendicular) to the boundary tends toward zero as does the particle velocity. Here's a visualization, from here: Note that if you are concerned about sound intensity, it is essentially zero in both pressure peaks and nulls. In fact, a key feature of standing waves is that, on average, no net energy is transmitted through space at all, so sound intensity (in the RMS average sense) is essentially zero everywhere. Instead, the energy of the standing wave oscillates between potential (pressure) and kinetic (velocity) forms and sloshes back-and-forth between the pressure/velocity peaks and nulls in the process. Of course, the situation changes in the presence of a listener, which acts kind of like a membrane bass absorber. Sound intensity across the skin depends mostly on frequency (i.e. chest cavity resonance) and pressure because the impedance of the solid/liquid flesh is much higher than that of the air.

It's a very narrow room. Those are 12" woofers, so you can kind of eyeball the width as maybe 8-10 feet. I don't recall, but I think the room stats were discussed earlier in this thread. So with 4 subs, almost all the velocity is in the front-rear dimension? What do the absolute magnitudes look like in each case? I.e., the square root of the sum of the squares of velocity in each dimension?

Hey! Who said there's anything wrong with chick flicks? ... assuming they have good bass, of course.

You make a good point and are probably right that at least some home mixes are done with very minimal effort. We have no idea why the -3 dB limiter was put on the TFA track, and purposeful dynamics reduction is only one possibility of many. I do believe the TFA track was re-EQed, and I actually think it is very nice sounding as far as EQ balance is concerned. Of course, that doesn't necessarily mean that they devoted a lot of time to perfecting it. Maybe Skywalker Sound Studios offers a kind of standard re-EQ filter-set that they recommend to mixers as a starting point that generally works well for content mixed in their cinema track facilities. Seeing PvAs of cinema vs. home mixed versions of a track would certainly be insightful. Even better would be to hear from the mixers themselves, but unfortunately, they don't frequent forums much. And when they do, they often have to confront a lot of negative sentiment about their practices and about the quality of the mixes. I can't blame them for not wanting to visit when they face so much vitriol, but I also don't believe it's one-sided either. In some exchanges (not naming any names here) I have noticed a know-it-all attitude and an unwillingness to consider alternative viewpoints. I've seen insistence that home systems are inherently inferior to larger room systems or that small rooms can't adequately reproduce the lowest bass frequencies. (!) Then there's the stubborn insistence that mixing in the near-field somehow approximates a home environment better than a dub-stage, even though the data I've seen suggests more similarity between a home theater and dub-stage than between near-field and either environment, particularly if the dub-stage is calibrated to a more neutral target than the X-curve. By itself, the reliance on the X-curve standard is a serious embarrassment to the industry, a problem I don't blame on mixers because they have a job to do which is not calibrating the systems or developing the standards. Nevertheless, it is for precisely that reason that the insistence of "knowing what's best" for production of home content deserves serious criticism.

That's not necessarily true, at least if the mixers are recent enough. From what I understand, "mixes" these days are actually implemented in meta-data rather than done literally. That's to say that a "mix" now-an-days consists of all the original tracks and objects along with instructions regarding how they should be combined. When an engineer hits "play" or instructs the system to export content for master, everything gets mixed in the DAW on-the-fly. If that's the case, then the filter(s) may just be meta-data regarding how to process a certain group of sounds or perhaps specific destination channels. Those filters could in principle be changed with just a few adjustments in the software. Of course, adjusting the filters is likely to have other knock-on effects such as a suddenly increasing headroom demand in parts that could lead to more aggressive activation of compressors, limiters, and/or more propensity for clipping. Of course, if it's a high headroom home mix with re-EQ, then there might be extra headroom for a more relaxed filter ... or not. If a mixer can adjust EQ levels for dialog separate from FX, then he/she might pull back the bass a bit in the dialog while leaving most of the sub effects hotter. Why not? Everyone likes more bass, right? Then again @maxmercy's BEQ work suggests there's already plenty of spare digital headroom in most tracks to not use filters. Incidentally, I have heard that there is some kind of unofficial limit for bass-managed output that the industry is supposed to adhere to, something like 120 dB total @ reference. (?) I think cinemas are told to spec their subs to be able to reach that level of output. However as evidenced by measurements here, not every soundtrack actually adheres to that limit.

Obviously, they remixed the track for the BD release. There are many good reasons to do remixes, but unfortunately the quality can vary a lot. As for filters, chances are that the mixers had no idea what they were cutting out. Often the systems used for these remixes aren't really up to the task. I've seen evidence that tiny near-field monitors and a single compact near-field sub, used in a huge room. Such a sub is likely to struggle to keep up even with the content above 30 Hz and at the lower monitoring levels commonly used. There are many possible reasons the filters get applied. First, many mixers assume the content below a certain point does not contribute to the mix and apply the filter as a matter of habit. Most cinema systems don't extend below 30 Hz either, so this shouldn't be a surprise. Second, mixers may be applying filters to protect their own equipment or prevent it from distorting. This is very unfortunate because I'd argue that the mixers ought to be applying such filters to their monitor output and not to the soundtrack itself. On the other hand, some mixers worry that if they can't hear what's going on "down there", then something they don't want to have on the track may slip through. I would argue that this happens anyway because of a combination of issues: poor quality monitors (which is most of them), poor quality listening space (near-field monitoring in a large room is a very poor listening environment for hearing soundtrack details), etc. Third, mixers may be applying filters in order to make the soundtrack louder. I'd argue that this is something that shouldn't happen for a home remix but probably does. While home remixes should be monitored at a lower level, consistent with changes in listening distance, room size, and other factors, they are often monitored at even lower levels than that. The assumption is that home listeners will listen even more quietly than a "room appropriate" reference level, so the mixers want to boost low level details to ensure they aren't lost. I don't really have a problem with that, but it goes very wrong when mixers start boosting the level of loud content too, in order to "increase impact" or "satisfy director's intent". The fact is, home listeners don't usually set their volume to a number but do so by ear based on loudness, so boosting loud content will only make home listeners turn down the content more, especially if they hear clipping and distortion that often gets introduced in such a process. I suspect that earlier home mixes including many BD re-releases suffered more from quality problems than more recent home mixes. Dedicated rooms designed to mimic home theaters and using better quality monitors (such as the new JBL M2/708 series) are becoming more common. However, filtering in general is still wide-spread and is more the norm than the exception, as can be seen by following this thread. We can only hope that, in time, more dedicated rooms are built and equipped with more capable sub systems. I can understand the concerns about equip a full size dub-stage with subs that extend into the single digits, but in a dedicated home theater mix room, this kind of setup should be much more practical. We'll see.

Holy humped filter Batman! It looks like they used PEQs instead of shelves to attenuate the low-end, given the sharp rise below 3 Hz.

I watched "9" tonight. My verdict? It sounds *excellent without EQ correction*. The dialog on the film sounds very natural and well-balanced with excellent mid-range clarity and just the right amount of fullness. It also goes without saying that the bass effects on this soundtrack are tremendous. The large hits are very wide bandwidth, combining both slam and weight. The "9" soundtrack is a reference for home theater audio systems in every respect.

I want to make some other notes about recently watched movies. After finishing re-EQ of my front stage, I watched "Finding Nemo 3D" on BD (2010), IIRC released in 2012. Being that the original was mixed in Skywalker Sound Studios, I was curious if the re-release might have a quality re-EQed home mix. It would seem not. It's possible that they didn't bother with a remix at all, being that the major change was in the video (3D conversion). Or if they did remix it, they did so in a Disney studio instead of at Skywalker Sound. A -2 dB/octave HF slope and -2 dB bass shelf cleaned it up very nicely, as is typical for other cinema mixes out of Skywalker Sound like Wall-E. Apart from being tainted by cinema EQ, the mix is very high quality as with most Pixar stuff. It deserves mention that the dialog is noticeably hot on this mix. It makes me wonder if Disney did a "lazy" home mix and just punched the dialog up 3 dB or whatever. Tonight I watched "Zootopia". This is a very recent Disney release (2016) with audio post done in Skywalker Sound Studios, so I expected a re-EQed mix. However, the mix was obviously shelved in the 200-300 Hz range (the usual spot for that sort of thing). I could not judge the highs because there was obvious low-end masking, but perhaps this movie did not get a home mix, was not done in Skywalker Sound's dedicated room, or did not get re-EQed for some other reason. Who knows? As a curiosity though, the "Zootopia" BD contained several "Deleted Scenes", and the spectral balance of the audio in those scenes was totally different. It sounded much more natural and balanced, if even a bit thin (in the low frequencies). The more balanced rendition revealed a lot more mid-range detail and nuance in the actors and actresses voices. This was even more obvious at a few points in which the directors replayed snippets from the actual movie in order discuss the (deleted) scene that was about to be presented. As such, the difference in spectral balance probably did not arise because of work a mixer did on the audio for the special feature itself. My guess is that the audio for the deleted scenes was presented as it was recorded, albeit with whatever EQ was applied to the clean-up the signal from the mics. Clearly these scenes were cut during an earlier phase of development as some consisted only of hand-drawn stills while others were CGI rendered at lower quality. The implication here is that the dialog audio presented in those scenes was from an earlier phase of production, perhaps before it had ever seen an X-curve calibrated dub-stage, at which point, bass boost was applied.

I plan to resume this work soon. It's taken me a long time to develop new EQ configs for my speakers after becoming aware of the "hidden resonances" I described. The effort has been very well worth it, and my sound quality is substantially improved from before, which was very good already. I finally finished updating the surrounds early today, but I want to take some time to watch a lot of movies and develop full confidence in this new configuration before attempting to do any critical work. From what I've heard so far, I'm not inclined to revise anything I've argued in this thread so far. With these new EQ configs, the broad tonal imbalances found on typical cinema tracks are somewhat less objectionable to me than they were before, particularly with regard to the low frequencies. However, the imbalances are just as apparent if not more so. On the other hand, fixing the hidden resonances will help immensely with getting my judgments right. The center had some significant issues in the 200-300 Hz, which I was aware of and did my best to work around. This range is crucial because it is where anechoic flat speakers tend to see a lot of gain from baffle step loss and/or reverb time increase and so is a region where alterations as part of the X-curve calibration procedure are likely to be more substantial. It is the range that I most often apply center shelving filters to deal with low frequency excess. I also had significant "hidden" resonances around another crucial area, between 2-3 kHz or so. In hindsight, this explains why "getting the knee right" seemed to be such an unforgiving exercise. Though, I imagine this region will still continue to be difficult simply because the X-curve "knee" resides at 2 kHz. As I previously noted, the soundtracks I've worked on sound quite bad with a sharp knee at 2 kHz. A more gradual transition from "flatish" to "sloped" seems to be required for the best sound, but getting the shape of the transition right is crucial and is different for every track. The area around 2 kHz has a big impact on speech and the upper-mid "punch" in many sounds. As an aside, I own a copy of Floyd Toole's most recent (3rd) edition of "Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms", which is a superb book on the subject, which is a superb reference for all things having to do with high quality audio reproduction. I can't recommend the book enough! Anyway, Toole dedicates an entire chapter to cinema sound and the X-curve with a lot of great info. He has a lot to say about the knee at 2 kHz as well: Anyway, there are many other details in that chapter that are worth discussing here at some point in the future. I'll just say that my arguments here are reasonably well supported by Toole's opinions as well. The X-curve standard degrades sound quality, both during the production process and during the reproduction in typical cinemas.

OK, that makes a difference.

Most of the BEQ configs posted here apply different filters to each channel *in the soundtrack*. That means that the filters must be applied before bass management (in which the bass for each main channel and everything from the LFE channel is summed and sent to the sub woofer). As such, using the PEQ built in to your subwoofer is not likely to yield the best results, and in many cases, it won't be clear which settings you should use. The benefit of the NanoAVR is that it is installed before your AVR in the device chain, and therefore, it is capable of applying processing to the channels in the soundtrack before bass management. Another point is that I don't know how big your room is, but these BEQ filters require a lot of capability below 20 Hz to take full advantage of. While the PB16 can certainly play below 20 Hz, its capabilities are quite limited compared to many of the systems people here use for that sort of thing. Of course, a lot depends on how your room behaves, but you might want to consider at least a second PB16 if not a more substantial DIY system if you want to get more out of BassEQ.