Kvalsvoll
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Posts posted by Kvalsvoll
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@maxmercy, I use a modified 10" driver, it is an old discontinued seas. 10" is a good size - good area for sensitivity, not too large so it does not change the sound field it is supposed to measure.
The 3x has less velocity in the important 30-40hz range, and a little less above up to around 120hz. Changing eq or delay on the BL back unit changes velocity response.
The 3x sounds better because it fills in a dip in the response around 60hz, phase is same, spectrogram is a little better.
The loss in velocity 30-40hz is noticeable. The increased v at ulf is more noticeable, because low freq noise stands out and becomes annoying - too much is not good. Further experiments can be to move the high-pass on the BL up in frequency, this will change the phase and perhaps make the velocity smoother - less ulf, fill in the dip 30-40hz.
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Sound field properties are important for how low frequencies are perceived.
Sound field properties are the relations between pressure, particle velocity and intensity. Both level and phase of velocity relative to pressure can change significantly inside a small room when properties of the bass system are changed - position of sound sources, delay, eq settings.
In Room2 I experiment with different bass system configurations, to find methods for setup that are repeatable and consistent. I experience differences even if the measured frequency response is the same. Some of those differences are caused by time-related issues like phase and decay. But some effects, notably at lower frequencies, are caused by differences in sound field properties.
The system I test now is a FL FR + BL config - one additional unit located at the back of the room. In this setup there is and increase in velocity and sound power around and below 20hz, which causes more movement in the floor than desired, on many music recordings there is simply way too much ulf.
I noticed this instantly, before doing sound field measurements - too much ulf. And indeed it looks like the BL back unit changes the sound field from 20hz and down, there is more velocity in the vertical direction.
The way to fix it is to adjust the frequency response - reduce the level around 20hz. It gets much better, but still not perceived as neutral - there is too much ulf, and noise and unintentional ulf sounds become distracting.
Also further up in frequency, there seems to be a clear correlation between velocity level and perceived bass quality - smooth is more neutral, more velocity is better and sounds more powerful and natural. Simply more fun.
Above the 40-50hz range the situation changes, velocity is still important, but will be more of a measure of sound directivity. In the upper bass range phase and timing and frequency response is the important properties to focus on, as the velocity and intensity more or less follows due to the sound waves being smaller compared to room dimensions and distance to sound sources.
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15 minutes ago, SME said:
By noise free, do you mean acoustic (i.e. fans), electric( i.e. hiss), or both?
If you're open to plate amps, you might look at some of the lower power offerings from SpeakerPower. They work best with 4 ohm, however. I believe they are based on the ICE amps, so you may be able to find other amp designs based off of ICE in EU. (Most of the ICEs I think like 4 ohm more.) Finding anything that's acoustic noise free with that power level will be tough.
Acoustic noise - fan noise.
Signal noise is rarely a problem with power amplifiers.
Plate amp is a no-go, requires cabinet building. They also tend to be more expensive.
Crown could work, I see they have the xli 2500 with regulated fan. Or if we could find a used K2.
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Looking for a reasonably priced power amp for midbass use - 2 channels, around 500-1000W/8 ohms/channel, NOISE-FREE.
Something like the inuke 3000, without the noise.
I have a design for some very powerful and compact midbass horns, and now I found a customer for them, so if we can find a suitable amplifier they will be built and tested. My SA-700 can be used, but it is kind of overkill, and quite expensive.
Any tips for such an amplifier? And no fan-mods or similar tweaking, it must work out-of-the-box.
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Unfortunately the de-clip does not work.
Clipping is usually caused by lower frequency transients, and when the signal clips, a very noticeable duration of higher frequency content is lost, and this can not be accurately restored. Some more advanced plugins may have algorithms that try to restore by estimating what should be there, by looking at previous and after signal content, but it will not be possible to restore the content completely.
For the lfe channel a declip can work better, but it requires gain adjustment to make room for the recovered transients, so the overall level will be reduced, and there is no gain in transient impact before gain is restored by increasing gain later in the chain.
Clipping is annoying and destructive for sound quality because of the harmonics that are introduced. For lfe, the lfe signal will always be filtered somewhere later, so the destructive effect is not so severe. And a clipped transient will add up to 3dB headroom, you can see this by low-pass filtering a clipped signal, the result will look like a de-clipped signal and it will have a higher peak amplitude.
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13 hours ago, SME said:
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.
And you need some method to measure it, doesn't need to be accurate or calibrated, just to be able to compare.
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7 hours ago, SME said:
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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.
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I really should find something new for another article to post, so we can continue to go far-too-deep into something else, don't think we disagree enough to continue this one much more now.. I have one, most of the text is ready, there are pictures and measurements, perhaps tomorrow.
I think @Ricci's post sums it up quite nice - mostly, not an issue, but, depends - some subwoofers, placements, floor and building issues, can cause problems.
I still see your example here as surprising, even when considering that those subwoofers will create much more force than the very different V110. To give a substantial difference in tactile feel, there must be a very significant difference in vibration level. And this can be measured. It should show up on the frequency response, and can be measured with a mobile accelerometer app.
It is actually possible to partially replicate this experiment; you could run only one driver active and short the other one - it won't be the same as single driver as the dead driver will still move a little, but should be enough to show a difference in vibration level form the subwoofer. With 2 drivers it should be dead, with one there will be motion.
And just when writing this, I read another difference - from PORTED to sealed. That can also be a factor in tactile feel experience, but is it really that huge..
Maybe I should repeat the measurements comparing sealed and ported/horn. Difficult to seal off the horn output in a V110, and there may actually be too little output left even for a measurement only.
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I can assure you the floor is not more stable and firm and damped than any other typical house. It is a very old house, so the walls are heavy, but the floor does not seem to be more rigid than in typical newer houses. It gives a nice and pleasant tactile effect, from around 20hz and down towards 10-12hz.
The problem you mention SME, about resonating and vibrating coupling between any loudspeaker and the floor certainly can cause audible problems, but it is also easy to fix, even those isopod products should work well for that. I consider this to be something that should be designed in to the speaker/subwoofer, so that the customer does not find the need to buy additional products to fix rattling and noises.
When you have something capable of decent output full-range, clean, then all kinds of rattles and noises suddenly appear, often from outside the room you are listening in. On the processor in Room2 there is a small strip of tape attached to the acrylic display cover - it rattles. The spotlight assembly in the ceiling in The Moderate Cinema rattled, then there are the structural noises from the house, which can not be fixed so easily.
The measurements were done with only one V110. Really no reason to complicate things by trying to decouple several subwoofer units.
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11 hours ago, SME said:
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.
After looking into specifications - which I could not find, because there are none - for the product you mention, I now looked into a different product, where I was informed that the resonance frequency was 5hz. I could not find any information on the product's web site to verify this claim. I could not find any relevant technical information. So I stand corrected about the specifications for those products, and the description reads like snake-oil to me.
If the spring is too hard, it will place the resonance right in the active working range of the subwoofer, and potentially make things worse. It also need to decouple in all directions - pivot, fore-aft, up-down, rotational.
It is easy to verify if it can work. If the spring is compressed less than several inches/cm, it is too stiff. If you measure the deflection of the spring, the resonance frequency can be calculated, provided the spring is linear. A foam pad is not linear.
If you make one large foam platform , sufficiently thick and soft to provide a low resonance, it would still be too stiff on the fore-aft direction, because the supported area is too large. A platform with springs in the corners could work. The foam blocks I used are only suitable for experiments, the subwoofer is not stable on top.
But the most important observation here is that it makes no difference, even if the decoupling is made so that it significantly reduces mechanical coupling down to frequencies below working range.
The floor in the room used for measuring this is what I consider quite normal for a wooden floor. But the subwoofer is placed close to walls, close to a corner. And in that location, the floor is much more rigid than in the center of the room, because the beams supporting the floorboards are supported only at the ends where the floor meets the walls.
The subwoofer vibrates, it moves, and it is transmitting those vibrations to the surface it sits on. It just that the level is too low to be significant, compared to the effect from the acoustic sound pressure in the room, which acts on the whole surface of all walls and ceiling and floor.
And the reports from people who tried this, says the same - no sound reduction for the neighbor.
The V110 is different from the usual sealed box subwoofer with long-excursion, heavy-moving-mass driver. The moving mechanical mass is 118g - very low compared to the usual around 500g or more. But the driving force is similar or higher. And it is quite tall, creates a large momentum. The main force from the surroundings acting on the cabinet will be the acoustic load on the port exit, and this load is far less than the typical 500g mechanical mass. The 118g cone assembly does not move much, due to the acoustic loading, so even comparing the moving mass to a different subwoofer is not relevant. Still, this subwoofer certainly moves and vibrates. The older ancestor T138 in the media room is more lightweight, they move and have to be pushed back into location occasionally.
A dual-opposite design is one solution to remove low frequency vibration, that actually works. But the floor still vibrates.
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7 hours ago, SME said:
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.
Focusing on only one part makes it easier to follow:
The decoupling I used works. I knew before I did the measurements, actually I did the measurements because I had a readily available decoupling solution that works TECHNICALLY. However, this solution is not suitable for ordinary use due to looks and the fact that the subwoofer floats on top and is very unstable. I had the blocks because i use them to handle the subwoofers when moving them around.
Transfer of vibrations are determined by only 2 parameters - resonance frequency and damping. If the resonance frequency is low enough, and the damping is not too high, it works.
The problem with foam is that the spring stiffness increases in a nonlinear fashion when compressed. If the foam is too soft and too low, it will compress and give a resonance frequency that is too high. The product you link to here (spec-sheet) can not work, because there is only 1 inch foam to act as the spring. this product may very well work to remove vibrations at higher frequencies, but it will not decouple at very low frequencies. If I had used a similar product or solution, it would be correct to assume that the measurements are not valid becuase the subwoofer is in fact not decoupled at low frequencies.
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12 hours ago, SME said:
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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.
The measurements and the article explains how this works, and why it is so.
It is explained and verified by measurements that vibrations and movement in the floor is caused by acoustic energy in the room, and that any directly induced vibration by mechanical transfer from the subwoofer to the floor is not significant.
The decoupling requires no advanced science, anything that gives a resonance frequency below around 5hz will work. The foam I used is very suitable for this purpose.
Commercially available isolation platforms have specifications for resonance frequency. Obviously the platform must be dimensioned to match the weight and surface area of the subwoofer. The flaw here is not the claimed function of the product - it will isolate the subwoofer mechanically from the floor. The flaw is the assumption that this will give less vibration in the floor, which it does not, because it is not the mechanical vibration of the subwoofer that causes the floor to move.
I may - or may not - do an English language translation of the article. Fixed it, here it is:
https://www.kvalsvoll.com/blog/2018/03/29/myth-or-fact-vibration-damping-platforms-for-loudspeakers/
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Another audio-myth busted: Vibration damping platforms for loudspeakers.
Place your subwoofers on an isolation platform, and reduce vibration and noise emitted though floor to keep your neighbor happy.
But this does not work. Because it is the acoustic energy in the room that excites walls and floor to create vibration, it is not due to the subwoofer jumping up and down. Actually, most subwoofers remain quite stable, even at excessive loudness levels, and they do not transfer much motion down to the floor.
We know that - either from experience or simply because we have some basic understanding of acoustics and physics involved.
I decided to measure this, to verify whether it works, or is it one more example where basic theoretical principles and engineering trumps the marketing department.
The article is up on the web-site in the blog section, but only in Norwegian language. I will post some links to measurement results, and make some comments here.
One V110 was measured, both spl at listening position, and floor vibration, for 2 cases - original solid base, and blocks of foam creating a completely decoupled and dangerously unstable base.
Results reveal that there is no reduction in vibration level with the decoupling - as expected. There is also no significant change in frequency or time domain at the listening position.
SPL difference at lp:
Vibration difference at floor below lp:
We see that the vibration response did change, but not enough to be noticeable, and at very low frequencies there is no change at all.
The decay plots also show very little difference. However, at higher frequencies, above 100Hz, there may be a difference, depends on the loudspeaker and the floor. A good isolator can have a positive effect on vibration and decay higher up in frequency, and thus impact sound quality. But on the V110 the effect is so small it is very unlikely to make any audible difference.
On a different floor, such as concrete in a basement, the situation will be very different, with no movement at all at very low frequencies.
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2 hours ago, maxmercy said:
LCRS were shelved away at significantly different rates, similar L/R/S, and then C was very different with more ULF.
BigMarket and escape from same was very good, as was the initial damaged ship flying over the pearls. Significant content there. Decent film, but like Dredd, not sure there is enough traction for a sequel.
JSS
I liked it, simple and no-nonsense story. With spaceships and decent sound quality with BEQ, and some nice actors, what more can you wish for.
Favorite scene is where the girl is serving the king his lunch, and suddenly realizes that she is the meal..
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18 hours ago, maxmercy said:
Valerian and the City of 1000 Planets:
I did a simpler approach on this one, and found huge improvements.
Did you find any ulf at all in LCR? I remember they dropped off very high.
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Posted this eminent solution on FB. It is basically useless for its intended purpose, but some will find it cool to use the phone to calibrate the stereo.
Some phones will work, some will not. There are no speccs available, so you just need to try a phone and see what happens. If you have my horns, you can place the phone in the horn mouth, and see if you get a reasonably flat graph down to below 20hz - if you don't, the phone is useless.
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@SME, I only tested with a HTC, and that one looks good below around 1-2K, and down to at least 10hz.
I have observed the SPL meter apps are popular, and they look nice and advanced, but I have always had my doubts regarding accuracy of those. Even a decent measurement mic needs to be calibrated, so what can you expect from a very cheap mic inside a mobile..
Dynamic range should be a concern for spl meter app, but for pink noise freq response can be assumed that the level is kept fairly low. I noticed there was not much correlation above around 5-8k, but below say 1k the response matched REW very well.
Those spectrum apps must be set up properly, to show a graph with stable and correct response. This complicates the use. If I write my own app, it can be tailored specifically for this purpose, no settings or tweaking needed.
If many phones have significant deviation from flat below 1K, that is actually a show-stopper for any app for speaker calibration. There is a point here were total complexity and cost becomes higher than the simplest REW + mic system - which actually works.
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How can you set up a bass-system if you have no measurement rig. Believe it or not, most people actually does not have acoustic measurement equipment.
Here is how:
1. Download and install a spectrum analyzer app on mobile.
2. Download the <don't remember the name> full frequency range spectrum pink noise file from my web site.
3. Play the file on repeat and monitor what happens to the sound using the spectrum app.
What can be fixed using this approach:
- Setting level for bass system.
- Adjust delay for main speakers.
- Add custom parametric filters for horrible and obvious resonances.
Very far from REW or similar, but compared to going totally blind this can fix integration and calibration to a level where many will be happy with the results.
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Just to continue, in between measuring the V110 in detail..
Frequency response is useful, as a tool - when used right. Tonal balance, potential resonances, getting the relative levels correct. It is also good for presenting a nice, smooth graph, after some heavy smoothing.
Impulse is nice to look at, I use step response for bass. But it doesn't tell much about the sound. There is little correlation between perceived sound and the shape of the curve.
Decay is important. Here the peaks that shows in freq can be analyzed, if they are resonances those will stand out as ridges, easy to see.
Waterfall is great for show-off.
Spectrogram is the other important graph. It shows how the sound start and stop, and reveals problematic reflections and decay.
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@SME, more knowledge often reveals that things are more complicated than you once believed, and you realize you don't have a simple answer anymore.
Frequency response is always the first we look at, and its destroys the day as we see it is not completely smooth, there are obvious flaws that needs to be corrected. As we learn more, gain more knowledge and experience, we realize this is just one visualization of what goes on, and reading a frequency response graph to actually get useful information out of it is not that easy. It is a steady-state visualization, and most of the signals we want to reproduce are transient in nature.
Right now I am working on bass-systems. Trying to find universally applicable methods and rules to set up the subwoofers. Does not help with a very good subwoofer, if it is not set up and calibrated properly. And in most practical cases, room acoustics efficiently destroys the possibility to achieve perfect sound in a simple and predictable way.
Measurements are accurate and very useful as a tool to compare before and after when doing changes on the system. But to be able to say exactly how it sounds, by merely looking at the measurements, that is not easy.
When I observe something about the sound, I try to find a way to objectively measure and quantify what I hear. Then perhaps i can be better at predicting how it sounds, and find ways to improve faults. The first thing, though, is to verify what I think I hear - not as easy as one might believe. Often it is necessary to rig experiments.
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@maxmercy, I have never heard one with drivers mounted across the whole wall.
There are practical problems with SBA/DBA solutions - obviously. And - I may be scolded for saying this - I am not convinced they add so much more than a more conventional system can do, when properly set up and calibrated, and you can manage to somehow get rid of the cancellation reflections.
From the experiments when I first found that velocity has significant impact for low bass perception - especially in the 20 - 50hz range - I also had a set-up with very much of that powerful wall-of-sound feel, and part of this has to do with getting more velocity than you get in the steady-state free-field condition. Similar to what you can achieve with near-field subs.
A DBA done right will get predictable and very good results. Other solutions often end up with one part of the freq range having some special and very good performance, but then there are faults in other places. The trick is to achieve that special part, but at the same time be able to fix the bad parts.
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@maxmercy, yes, now, that is the question to ask.
Fact is, I did not notice any huge difference. Even the 1x is as good as should be expected, and the 2x and 4x does not really have that much more, though they sound a little bit more tight and immediate, 2x a little better, and 4x even a little more. But I can not say there was a difference large enough in tactile experience to really differentiate the systems.
The 1x hold up with bass-heavy music up to +3dB, enough for some tactile feel. But the larger ones can do much louder, and THAT makes a huge difference.
ULF below 20-25hz is similar, as long as kept within limits.
I still have 2x V110, so I can test some more, perhaps find a way to measure and get objective information.
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8 minutes ago, SME said:
but I can say with confidence that a perfectly flat or smooth in-room response is not optimal unless the room is completely dead.
This is the tricky part. If the solution is to just eq to flat, it would be easy. But it isn't.
Especially in the bass range, velocity and intensity matters. And you have to measure at different locations, at least cover different locations in height where the listener is located.
Decay is important. Resonances will affect perceived tonal balance.
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Velocity measurements now available:
Sideways velocity (90 degrees):
Green is 1x configuration.
Vertical (h):
Red is 4X.
Normal to front wall (0 degrees):
Frequency response has a huge, narrow dip around 60-70hz. This must be caused by reflection from the back wall corners. This dip becomes progressively more deep and narrow as the sound field from the source gets closer to plane wave.
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@SME, inside a room the situation is complex, because boundaries are not rigid, there are windows, and sometimes openings, such as in Room2.
These velocity measurements are only another tool to try to get more information, to get a better understanding of what is going on.
Sound intensity and sound field properties affect perception of sound, we know that now. But velocity alone is only one part of this, and especially for higher bass frequencies - where chest slam occurs - it looks like intensity pressure is more important, due to the acoustic impedance properties of our body. To feel the sound moving your clothes, you need velocity.
Also, frequency response and phase behavior have huge significance for perception, both what we hear and tactile.
Just finished testing the V110 in the Moderate Cinema, to find out if it is suitable for movies. It is. But compared to the original T138 horn, it drops off a little below 20hz, above 15hz the V110 has more output, and should sound cleaner and more defined because there are no resonances left around the crossover, where the T138 no longer performs well in the time domain.
I didn't bother doing a proper calibration, did not even use the default dsp settings, but the freq response looked reasonably similar to the T138, so I just left it like that.
And does it sound better? Is it better to have this vertically large sound source? Does the effort put into the advanced design pay off in better sound quality?
It does sound different, but not necessarily better. I suspect my lazy calibration approach comes to play here.
The sub bass is experienced as similar, the level drop in the 10-15hz range does not seem to have much significance. The airplane-flyover-scene from Hanna sounds similar, Oblivion works fine, the storm in Kon-Tiki moves the whole house.
Mid-bass is stronger and more powerful. Nice punch, and there is capacity available to turn it up, bass-heavy music at +6dB works fine, and then you add another +6dB on the bass system for that visceral feeling.
Transients with large bandwidth lacks some of the precision and sudden impact. I blame this on my lazy calibration. Example - the cannons in Hunger Games.
All in all, my conclusion is that the V110 works for movies. Same powerful bass transients with impact, like you are hit by a small shock-wave.
Now I will look at the measurements to see if it is possible to see something there that corresponds with what I think I hear.
, 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 Bass EQ for Movies Thread
in Bass Content
Posted
Huge gain on the LCR+Surronds here in your BEQ, also more gain on the lfe than I would assume, but now I have not seen the spectrums, an the result looks fine to me.
Just listened briefly to some scenes, and I wonder if just some boost below 20hz will do most of what is needed here. Also agree with your BEQ in that there is no need to reduce any mid-bass bump.