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Measuring the 'Tactile Feeling' of your sub system - Page 2

post #31 of 96
what is your sub system consisting of at this point right now?
post #32 of 96
Quote:
Originally Posted by dominguez1 View Post

Great points about the suspended floor. I've heard sub systems on them before and it was definitely a cool effect...just didn't listen long enough to really pay attention to how it changes with other frequencies.

Also, good education for me about transducers. Didn't know they went that low. I've heard them implemented where I believe the rolloff was 40hz or so, IIRC. This system had the benefit of transducers as well as pressurization shake, and is definitely a nice blend.

I think it's important to differentiate between "pressurization" and "shaking". The two are completely different phenomena.

Pressurization occurs when the SPL, (Sound PRESSURE Level), reaches a point where the pressure can be "felt." It becomes a sensory input that is unrelated to a surface contact, (i.e., the floor, the sofa, etc.) The larger the room, the harder it is to pressurize it. A smaller, sealed room can be pressurized much easier than a larger, leaky room.

Shaking is a tactile sensory input that is caused by an external object vibrating from actuation by the pressure generated by the sound waves, or by actual movement caused by a tactile transducer. The vibrations are transmitted directly to the body and are sensed as movement.


Quote:
He recently moved his subs to the front stage so that none were nearfield any longer. His wife actually requested they go back to nearfield, because she wasn't getting that chest impact that nearfield subs provide!!! (what a good wife!) I guess that would be one tactile sensation that couldn't be reproduced by a transducer.

Correct, a transducer can not generate "pressurization."

Quote:
So, with my system being on a concrete floor, I don't have that resonant frequency vibrating the floor, in turn vibrating the HT seats. So, my tactile sensations are for all frequencies as well, correct? It's really my subs doing all the shaking.

If the subs are generating the sound pressure waves that are causing the seats to vibrate, (i.e, acoustic-mechanical coupling), the seats will vibrate most intensely at their resonant frequency. I can't say whether that range of frequencies is "all frequencies", but I think it would be unlikely. It depends on the seats and their construction and mass.

Craig
post #33 of 96
Thread Starter 
Quote:
Originally Posted by MKtheater View Post

What percent THD was that?

Unfortunately, we didn't take that reading...
post #34 of 96
Thread Starter 
Quote:
Originally Posted by MKtheater View Post

I have hit 123 dBs at 10hz.

This is sick...
post #35 of 96
Thread Starter 
Quote:
Originally Posted by craig john View Post

I think it's important to differentiate between "pressurization" and "shaking". The two are completely different phenomena.

Pressurization occurs when the SPL, (Sound PRESSURE Level), reaches a point where the pressure can be "felt." It becomes a sensory input that is unrelated to a surface contact, (i.e., the floor, the sofa, etc.) The larger the room, the harder it is to pressurize it. A smaller, sealed room can be pressurized much easier than a larger, leaky room.

Shaking is a tactile sensory input that is caused by an external object vibrating from actuation by the pressure generated by the sound waves, or by actual movement caused by a tactile transducer. The vibrations are transmitted directly to the body and are sensed as movement.



Correct, a transducer can not generate "pressurization."


If the subs are generating the sound pressure waves that are causing the seats to vibrate, (i.e, acoustic-mechanical coupling), the seats will vibrate most intensely at their resonant frequency. I can't say whether that range of frequencies is "all frequencies", but I think it would be unlikely. It depends on the seats and their construction and mass.

Craig

Good stuff Craig, make sense.

So, in laymen's terms:

When we commonly speak of 'Tactile Impact', it's a combination of pressurization of the room that exerts force directly on your body (e.g. chest slam) as well as the pressure that has caused your seats or floor (or both) to vibrate, causing you to shake.

Seats and suspended floors have certain frequencies that they vibrate more than other frequencies as soundwaves exert pressure on them. Transducers vibrate evenly across all frequencies because they are being driven mechanically.

Measuring the 'shaking' capability of your sub system is highly dependent of the construction and material of the seat and floor. If it's a concrete floor, then it is only the seating that is shaking.

So, going back to measuring; we can measure 'shaking' with tools like vibration meters. Is there a way to measure the pressure of a room with inexpensive tools?

Being able to measure both would give an idea of your room's 'Tactile Impact'. Combine this with all of the typical metrics we use to measure sound (frequency response, distortion, etc.) and this should give people a better understanding of what it feels and sounds like in your room without actually having to be there.
post #36 of 96
Thread Starter 
Quote:
Originally Posted by MKtheater View Post


I will try it, I did not see it on my iPhone. I am +/- 3 dBs from 7-120hz. I have hit 123 dBs at 10hz.

MK, did you ever get around to trying that app on your galaxy?
post #37 of 96
Thread Starter 
@Archaea,

Saw the vid of your caps shaking your screen...very cool. Do you have an android based phone to run this app too? I'd like to see what your room registers...give people more context with your blind meet too!
post #38 of 96
Quote:
Originally Posted by dominguez1 View Post

@Archaea,

Saw the vid of your caps shaking your screen...very cool. Do you have an android based phone to run this app too? I'd like to see what your room registers...give people more context with your blind meet too!

I get that shake of the screen as well but I have done as much as I can to fix that. I have not run the app yet as I forgot the Tablet at the office. I will try it over the weekend.
post #39 of 96
Quote:
Originally Posted by MKtheater View Post

I will try it, I did not see it on my iPhone. I am +/- 3 dBs from 7-120hz. I have hit 123 dBs at 10hz.

Based on this thread I just downloaded for my iPhone VR Mobile "free" Vibration Meter, http://itunes.apple.com/tn/app/vr-mo...469459743?mt=8


will try it out tomorrow when the wife/kids are out
126db @ last part, the famous wa-tu-shi finger hold scene!!
post #40 of 96
Thread Starter 
Quote:
Originally Posted by MKtheater View Post

I get that shake of the screen as well but I have done as much as I can to fix that. I have not run the app yet as I forgot the Tablet at the office. I will try it over the weekend.

Hey MK, did you ever get around to trying this?
post #41 of 96
Thread Starter 
Quote:
Originally Posted by mtbdudex View Post

Based on this thread I just downloaded for my iPhone VR Mobile "free" Vibration Meter, http://itunes.apple.com/tn/app/vr-mo...469459743?mt=8


will try it out tomorrow when the wife/kids are out
126db @ last part, the famous wa-tu-shi finger hold scene!!

How did this app work?

Cool vid by the way. Never seen an IB in action! Nice!
post #42 of 96
Quote:
Originally Posted by dominguez1 View Post

How did this app work?

Cool vid by the way. Never seen an IB in action! Nice!

Bracing methods came up in this thread, Most Efficient Bracing ? (less space taken) , so this weekend I'll use it and report back.

On the vid, it's neat to "show-off" the cone movement in person for guests, and let them "feel the bass" literally in their body up close, and also in the seats.
post #43 of 96
Thread Starter 
Quote:
Originally Posted by dominguez1 View Post

Good stuff Craig, make sense.

So, in laymen's terms:

When we commonly speak of 'Tactile Impact', it's a combination of pressurization of the room that exerts force directly on your body (e.g. chest slam) as well as the pressure that has caused your seats or floor (or both) to vibrate, causing you to shake.

Seats and suspended floors have certain frequencies that they vibrate more than other frequencies as soundwaves exert pressure on them. Transducers vibrate evenly across all frequencies because they are being driven mechanically.

Measuring the 'shaking' capability of your sub system is highly dependent of the construction and material of the seat and floor. If it's a concrete floor, then it is only the seating that is shaking.

So, going back to measuring; we can measure 'shaking' with tools like vibration meters. Is there a way to measure the pressure of a room with inexpensive tools?

Being able to measure both would give an idea of your room's 'Tactile Impact'. Combine this with all of the typical metrics we use to measure sound (frequency response, distortion, etc.) and this should give people a better understanding of what it feels and sounds like in your room without actually having to be there.

This is probably a long shot but...

Could a barometer measure the pressure exerted on us by our subs? If so, you could take a reading before, play a sine wave or movie clip and see how the barometer reacts?

See video below. We would represent the barometer in the bag, and when the person compresses the sealed bag applying pressure, that would simulate the sub output exerted on our bodies?



Thoughts? Is there a reason why this wouldn't work?
post #44 of 96
dominguez1, this is a very interesting topic. Thanks for starting it.

I tried to download an app for my iPad to measure the vibration. It's the VR Mobile one mentioned by mtbdudex above. However, the reading is in X Y Z numbers, it doesn't give a nice numerical reading on the scale like yours.

Anyway, as to your situation with the tactile feel being much better with the Outlaws (despite the similar looking FR) I'd venture to say that previously although your graph went down to 10Hz, it was mainly contributed by your 2 eD A7S-450s up front. As you said the PSW1 rolls off around 25Hz. The extension by the eDs mask the lesser contribution by the PSW1. So overall your graph still looks good.

But now your Outlaws extend lower and have greater output. This probably gives you a more tactile feeling than before.

From my own experiments with REW, I'd say that FR graphs don't explain everything about how a system sounds and feels. Two similar graphs can sound/feel different.
post #45 of 96
Thread Starter 
Quote:
Originally Posted by dominguez1 View Post

I have no transducers...this is all sub listening at reference level, with my subs measuring at 112-115db on a concrete floor. See video below:



Here's the scale (MMS) for reference:

1.0 - Instrumental. Felt by animals
2.0 - Weak. Felt indoors by a few people
3.0 - Slight. Felt indoors by several
4.0 - Moderate. Hanging objects swing
5.0 - Rather Strong. Dishes broken
6.0 - Strong. Heavy furniture moved
7.0 - Very Strong. Difficult to stand
8.0 - Destructive. Fall of walls
9.0 - Violent. Noticeable ground cracks
10.0 - Intense. Almost destroyed
11.0 - Extreme. Rails bent greatly
12.0 - Cataclysmic. Total destruction

Here's the conversion to the Richter Scale:



I hit 7.0 (Very Strong. Difficult to stand) on the MMS Scale, and 5.0 on the Richter scale at my main LP!!! This was on the app; Vibration Meter for the Android. I was playing the Irene scene in Blackhawk Down. I hit 7.0 during the ULF portion (7hz or so) of that scene. I hit 7.4 with WOTW.

Tweaked my setup today...I'm at 7.5 with Blackhawk Down and 7.8 with WOTW...

Has any not tried this yet? It's a pretty cool app. Can't find a good one though for the iphone/ipad.

I am planning on getting a digital barometer pretty soon to see if that can detect the increase in pressure in my room.


Edited by dominguez1 - 6/28/13 at 8:58pm
post #46 of 96
Thread Starter 

Just ordered a Pyle Sports Digital Handheld Barometer (~$32):



Looks like it has decent pressure measurement resolution:

Barometer
- Pressure Range 300.0 hPa / mbar to 11 00.0 hPa / mbar
(8.84 inHg to 32.44 inHg)
- Resolution of 0.1 hPa / mbar (0.01 inHg)
- Max. / Min. memory for Pressure
- Pressure History and Graphical display of the last
12 hours pressure readings

Once I get it, I'll play some strong LFE content at reference and see how the pressure in the room changes (it records min and max pressure). Hopefully it does so in a way that can be measured by the Barometer.

The hope is that folks can measure the pressure changes in their room and post them. This will give others that may never visit your HT a reference of how it potentially 'feels' in your room without actually being there.

We'll see...


Edited by dominguez1 - 6/29/12 at 8:39am
post #47 of 96
Thread Starter 
^^^FAIL.

That didn't work at all. I played WOTW and placed it right by the driver...pressure didn't change at all.

Ah well, I gave it a shot...
post #48 of 96
Thread Starter 

One of my questions I posed in the first post in this thread was:

Do ported subs have more tactile response compared to sealed subs? Specifically, in my case, can my A7S-450s shake the couch as much as my Outlaw LFM1-EXs?

I integrated both subs (eD and Outlaw) with my new FTW21 drivers with my eQ.2s and got the below response for the eD and FTW:

112453.jpg

Below is the response for the Outlaws and FTW:

FTW21 + 2 Outlaw LFM1-EXs

Look very similar, right? From a tactile feeling standpoint, it wasn't even close. The response with the Outlaw complete shook the couch as before, whereas the eD hardly did anything. I ran through a bunch of different demos (WOTW, Hulk, BHD, etc.), and there really wasn't a comparison. Ported won in the tactile response department. Even from a MBM standpoint, I could tell no significant difference with the eDs.

So I turned off the FTWs, and took the response of the eD and outlaw by themselves. Unfortunately, I didn't record the response of the eD that I measured in the above combined FTW/eD curve. The eD response below is actually the eD response after boosting with the eQ.2. However, the two curves were very similar from 18hz and up. The only difference in the below curve is that 10-18hz is around 10db higher because of the eQ.2 boost.

The red is the Outlaw, the black is the boosted eD

112454.jpg

If you can imagine the eD curve down 10db from 10-18hz, you'll understand the curve I was 'listening' to. You can obviously see the difference between the Outlaw and eD. It was an easy decision for me to not even try and listen to the eD boost and FTW, because even with it boosted, it could not keep up with the Outlaw in the back of my room. If that's confusing...well, it's because it is...sorry.

I guess the moral of the story is: sealed vs ported - which shakes more? It all depends on the room of course, BUT in voids (little room gain or nulls) like the one I had (apparently) in the back of my room, ported subs will hold its FR better to tune whereas the sealed will drop off. In cases like these, ported will have a better tactile response typically and won't have to work as hard (EQ) as a sealed to get the same response. In these cases, ported wins IMO.


Edited by dominguez1 - 8/4/12 at 5:44pm
post #49 of 96
Quote:
Originally Posted by craig john View Post


I think it's important to differentiate between "pressurization" and "shaking". The two are completely different phenomena.


Pressurization occurs when the SPL, (Sound PRESSURE Level), reaches a point where the pressure can be "felt." It becomes a sensory input that is unrelated to a surface contact, (i.e., the floor, the sofa, etc.) The larger the room, the harder it is to pressurize it. A smaller, sealed room can be pressurized much easier than a larger, leaky room.


Shaking is a tactile sensory input that is caused by an external object vibrating from actuation by the pressure generated by the sound waves, or by actual movement caused by a tactile transducer. The vibrations are transmitted directly to the body and are sensed as movement.

Correct, a transducer can not generate "pressurization."

If the subs are generating the sound pressure waves that are causing the seats to vibrate, (i.e, acoustic-mechanical coupling), the seats will vibrate most intensely at their resonant frequency. I can't say whether that range of frequencies is "all frequencies", but I think it would be unlikely. It depends on the seats and their construction and mass.


Craig

Hi CJ,

The vibrations you feel from a tactile transducer are from transmission. That's very different from vibrations caused by a traveling pressure wave. The traveling pressure waves will indeed cause a seat to vibrate in "all frequencies", assuming we're talking about the subwoofer bandwidth. The extent to which the vibration is felt, of course, is directly proportional to the intensity of the pressure waves, or Sound Pressure Level and not the frequency of the pressure waves.

Pressurization is a term that describes a phenomenon that has nothing to do with the discussion. Subwoofers do not change the pressure in a room, as Dominguez discovered while measuring pressure during WOTW. The subwoofers send pressure waves from their point source (driver cone, port, horn mouth) into the room. Contrary to popular vernacular, subs don't "move air". The pressure wave is simply a series of compression and rarefaction of air molecules that stay right where they are as the wave moves through them.

Rooms vary mostly in layout, but home building standards haven't changed much in 50 years. The degree to which the pressure wave keeps its intensity has a lot to do with transmission losses. Obviously, an interior wall will have far greater losses than an exterior wall and a masonry exterior wall will have less loss than a sided exterior wall. Similarly, glass will exhibit greater losses than the exterior wall. The conundrum here is that, although the clad, studded exterior wall exhibits as much as 20 times more transmission loss than a concrete basement wall (like MKT's), giving the basement walled room a huge advantage with low frequencies (like MKT's), the pressure waves have little hope of causing the massive concrete walls to vibrate. So, while you'll no doubt experience easily measurably higher level pressure waves in the typical basement due to lower transmission losses (like MKT does), a frame wall/floor room will be far more easily caused to vibrate by the traveling pressure waves.

The point is that a subwoofer cannot change the pressure in a room one iota. What's felt is the vibration of the room and objects in the room (including the human objects) caused by the traveling pressure waves.

An illustration would be the difference in what is being felt in your room if an earthquake occurs vs if a jet airliner that's taking off flies over your roof.

This is the flaw in Dom's measurement results. He's measuring the effect of sound pressure waves (jet) with a Mercalli scale which is for seismic detection (earthquake).

Dom,

If you use the AVRs rumble tone to calibrate the 2 sub systems equally, the LFM system will have less output below 30 Hz than the Ed system. As it is in your graphs, the LFM system is running around +8dB hotter than the Ed system, which is significant.

I would also suggest that you run your FR measurements at 100dB minimum, matching both systems to 100dB at 60 Hz, to give a more accurate picture of the differences between the 2 systems as well as much more accurate FR results.

Bosso
post #50 of 96
Interesting points you made there bosso particularly about the part about subs not "moving air". I recall an earlier discussion about that elsewhere.

There are some videos of objects like caps or cloth being "blown" when placed near a sub's port. Is that not air pushing those objects away? Or is it something specific to how ports work?
post #51 of 96
Quote:
Originally Posted by jchong View Post

Interesting points you made there bosso particularly about the part about subs not "moving air". I recall an earlier discussion about that elsewhere.
There are some videos of objects like caps or cloth being "blown" when placed near a sub's port. Is that not air pushing those objects away? Or is it something specific to how ports work?

No, it's not air blowing the object. If the object was suspended in front of the port, it would clearly show the pressure wave causing a back and forth motion, not as if a fan were blowing the object. Air is the medium through which the pressure waves travel. Since the "medium" in this case is a cap or cloth, the pressure wave hits the "medium", but can't move through it as it does through air. More of the wave is reflected because the cap or cloth is not a good medium. When the wave reflects, there is an equal and opposite reaction.

This is similar to how a floor or wall reacts when the pressure waves hit them. They vibrate as most of the waves are reflected back into the room. This effect is easier to detect when the waves are pulsed, like a kick drum, vs a steady state sine wave.

A good example of this effect below 20 Hz is the first scene in Star Trek, when the Romulun ship emerges from the black hole.

StarTrekShipEmergesNoHPF.jpg

The effect of that ULF spread of frequencies being pulsed at high SPL causes my floor to ripple and therefore is very noticeable. Since my subs are dual opposed and sitting in corners where the floor structure is most sound, it's definitely not extraneous vibration by transmission, but has to be the pressure waves hitting the structure. It most certainly isn't blown air as it would take a heck of a wind to ripple the floor. An opposite example is Irene, where the signal is steady state throughout the scene and therefore is much less noticed by many listeners.

Bosso
post #52 of 96
Thanks for the explanation bosso.
post #53 of 96
Great stuff, Bosso. Thanks for clarifying and the added detail. smile.gif

Craig
post #54 of 96
Thread Starter 
Quote:
Originally Posted by bossobass View Post

Hi CJ,
The vibrations you feel from a tactile transducer are from transmission. That's very different from vibrations caused by a traveling pressure wave. The traveling pressure waves will indeed cause a seat to vibrate in "all frequencies", assuming we're talking about the subwoofer bandwidth. The extent to which the vibration is felt, of course, is directly proportional to the intensity of the pressure waves, or Sound Pressure Level and not the frequency of the pressure waves.
Pressurization is a term that describes a phenomenon that has nothing to do with the discussion. Subwoofers do not change the pressure in a room, as Dominguez discovered while measuring pressure during WOTW. The subwoofers send pressure waves from their point source (driver cone, port, horn mouth) into the room. Contrary to popular vernacular, subs don't "move air". The pressure wave is simply a series of compression and rarefaction of air molecules that stay right where they are as the wave moves through them.
Rooms vary mostly in layout, but home building standards haven't changed much in 50 years. The degree to which the pressure wave keeps its intensity has a lot to do with transmission losses. Obviously, an interior wall will have far greater losses than an exterior wall and a masonry exterior wall will have less loss than a sided exterior wall. Similarly, glass will exhibit greater losses than the exterior wall. The conundrum here is that, although the clad, studded exterior wall exhibits as much as 20 times more transmission loss than a concrete basement wall (like MKT's), giving the basement walled room a huge advantage with low frequencies (like MKT's), the pressure waves have little hope of causing the massive concrete walls to vibrate. So, while you'll no doubt experience easily measurably higher level pressure waves in the typical basement due to lower transmission losses (like MKT does), a frame wall/floor room will be far more easily caused to vibrate by the traveling pressure waves.
The point is that a subwoofer cannot change the pressure in a room one iota. What's felt is the vibration of the room and objects in the room (including the human objects) caused by the traveling pressure waves.
An illustration would be the difference in what is being felt in your room if an earthquake occurs vs if a jet airliner that's taking off flies over your roof.
This is the flaw in Dom's measurement results. He's measuring the effect of sound pressure waves (jet) with a Mercalli scale which is for seismic detection (earthquake).

Great info Bosso, as usual. It makes a lot of sense (at least at a 10,000ft level).

A couple of things:

One of the reasons why I started this thread was I wanted to see if there was any tool or measurement that would allow me (and others) to really know how it 'feels' in each others room. Obviously, there are many factors that come into play and you'd never truly know how it 'feels', but my hope was that it would at least give you a general idea of what it feels like to watch a movie in your room.

Based on my experience and those who have contributed so far, I'd classify 'tactile feeling' in two ways:
  1. The shaking caused by physical objects (seating, floor, etc.) that are in contact with your body as a result of the pressure waves created by the sub or mechanical shaking of a transducer moving those physical objects. In your example, I would equate this with the 'earthquake'.
  2. The pressure waves traveling from the sub that come in contact with your body directly. I equate this sensation to the 'kick in the chest' sensation. In your example, this would be the jet, or another example would be blades of a helicopter. In this case, the pressure waves are directly affecting your body, and not indirectly through other objects. IOW, you could be standing in a concrete bunker and still feel this sensation.

Again, not exact my any means, but the tool to measure #1 could be something like the vibration meter in the Mercali Scale. I'm not directly trying to measure the pressure waves, but the affect that the waves have by 'shaking' the physical objects that are in contact with your body. I peaked around 7 on that scale. If MK measured, and peaked around 10 in his room, now I have somewhat of a frame of reference of what the 'shaking' feels like in his room compared to mine.

Now for #2, obviously the barometer isn't the right tool to measure...as to how we can measure this sensation is still unknown to me....or perhaps it is just an SPL reading? Intuitively, 120db nearfield would seem to have more tactile sensation than 120db from 20ft away. BUT, the more I think about it, perhaps we are confusing #1 and #2 for that nearfield sub. IOW, 120db sitting on a couch with the sub behind you, is going to feel much different sitting in the same couch with 120db from a sub 20ft away. Perhaps this is because the nearfield placement is better at physically shaking the couch and we perceive that as more of a tactile feeling. But if we were to remove the couch, 120db would actually feel the same nearfield as it does from 20ft away?

Does this make sense? Maybe a straight SPL reading IS the best way to measure #2...what needs to change is the way we measure it (e.g. we need to not be affected by physical objects in contact with us to measure apples to apples).

To bring it back to the beginning, combining these 'tactile feeling' measurements with FR, distortion, etc., I think it would give people a fairly good idea of what it is like to watch a movie or listen to music in your room (at least from a subwoofer frequencies standpoint) without actually having to be there.
post #55 of 96
Thread Starter 
Quote:
Originally Posted by bossobass View Post

Dom,
If you use the AVRs rumble tone to calibrate the 2 sub systems equally, the LFM system will have less output below 30 Hz than the Ed system. As it is in your graphs, the LFM system is running around +8dB hotter than the Ed system, which is significant.
I would also suggest that you run your FR measurements at 100dB minimum, matching both systems to 100dB at 60 Hz, to give a more accurate picture of the differences between the 2 systems as well as much more accurate FR results.
Bosso

All good points above. I guess I was being somewhat self serving in this test...as I wasn't trying to answer the general question of which 'shakes' more, sealed or ported for the general public... frown.gif

Given two subs with the same FR and output, I believe they should have the same impact.

For my purposes, I wanted to find out which was better for my room. With the eD's, I had that nasty dip beginning at 22hz. Even when I boosted by +15db, it still could not match the LFMs. I'm guessing it was a nasty null. I played with phase as well, and in that position behind my couch, they just weren't playing nicely. I really don't have any other positions for the room, so that's why I ended up with the LFMs. The eDs are now sold, unfortunately.

At any rate, I'm extremely happy with the results of the FTW and Outlaw EXs.
post #56 of 96
Quote:
Originally Posted by dominguez1 View Post

Great info Bosso, as usual. It makes a lot of sense (at least at a 10,000ft level).
A couple of things:
One of the reasons why I started this thread was I wanted to see if there was any tool or measurement that would allow me (and others) to really know how it 'feels' in each others room. Obviously, there are many factors that come into play and you'd never truly know how it 'feels', but my hope was that it would at least give you a general idea of what it feels like to watch a movie in your room.
Based on my experience and those who have contributed so far, I'd classify 'tactile feeling' in two ways:
  1. The shaking caused by physical objects (seating, floor, etc.) that are in contact with your body as a result of the pressure waves created by the sub or mechanical shaking of a transducer moving those physical objects. In your example, I would equate this with the 'earthquake'.
  2. The pressure waves traveling from the sub that come in contact with your body directly. I equate this sensation to the 'kick in the chest' sensation. In your example, this would be the jet, or another example would be blades of a helicopter. In this case, the pressure waves are directly affecting your body, and not indirectly through other objects. IOW, you could be standing in a concrete bunker and still feel this sensation.
Again, not exact my any means, but the tool to measure #1 could be something like the vibration meter in the Mercali Scale. I'm not directly trying to measure the pressure waves, but the affect that the waves have by 'shaking' the physical objects that are in contact with your body. I peaked around 7 on that scale. If MK measured, and peaked around 10 in his room, now I have somewhat of a frame of reference of what the 'shaking' feels like in his room compared to mine.
Now for #2, obviously the barometer isn't the right tool to measure...as to how we can measure this sensation is still unknown to me....or perhaps it is just an SPL reading? Intuitively, 120db nearfield would seem to have more tactile sensation than 120db from 20ft away. BUT, the more I think about it, perhaps we are confusing #1 and #2 for that nearfield sub. IOW, 120db sitting on a couch with the sub behind you, is going to feel much different sitting in the same couch with 120db from a sub 20ft away. Perhaps this is because the nearfield placement is better at physically shaking the couch and we perceive that as more of a tactile feeling. But if we were to remove the couch, 120db would actually feel the same nearfield as it does from 20ft away?
Does this make sense? Maybe a straight SPL reading IS the best way to measure #2...what needs to change is the way we measure it (e.g. we need to not be affected by physical objects in contact with us to measure apples to apples).
To bring it back to the beginning, combining these 'tactile feeling' measurements with FR, distortion, etc., I think it would give people a fairly good idea of what it is like to watch a movie or listen to music in your room (at least from a subwoofer frequencies standpoint) without actually having to be there.

I think this is a great thread. cool.gif

If you've noticed, I don't post much these days. That's because there aren't many threads like this that look at new areas of what we experience when listening and why we like one presentation or another more or less.

The problem here is that transmission and excitation from traveling pressure waves both cause tactile sensation. Living close enough to and working near airports in Pittsburgh and here in Charlotte, I've seen cases where a jet taking off shattered the windows in a house. Back in the 60s thru the early 80s, when legacy engines produced 130-140dB at takeoff, the airport authorities had to purchase homes and move people out of the new flight paths.

Then there's the subs that cause extraneous transmission vibrations by their design vs dual opposed subs like the SM, Empire and DIY (I've been building them for 9 years because the previous subs I built were down-firing and I immediately noticed the difference with the first dual opposed sub build).

Still, I encourage you to keep this thread alive and continue to investigate. You're obviously a smart guy and the audio world needs a metric for quantification of low frequency reproduction. There are lots of metrics and methodologies for anechoic performance, but next to none for how that translates to the listening experience in different rooms with different source material.

I just thought some basic understanding of the physics of the phenomena would help forward motion.

Good stuff, Dom. smile.gif

Bosso
post #57 of 96
Quote:
Originally Posted by bossobass View Post

Then there's the subs that cause extraneous transmission vibrations by their design vs dual opposed subs like the SM, Empire and DIY (I've been building them for 9 years because the previous subs I built were down-firing and I immediately noticed the difference with the first dual opposed sub build).

Bosso, can you elaborate a bit more on this? How do dual-opposed subs differ in terms of causing extraneous transmission vibrations? I take it you're not referring to the cabinet vibrations themselves but rather how the sub interacts with the room.
post #58 of 96
Quote:
Originally Posted by dominguez1 View Post

Now for #2, obviously the barometer isn't the right tool to measure...as to how we can measure this sensation is still unknown to me....or perhaps it is just an SPL reading? Intuitively, 120db nearfield would seem to have more tactile sensation than 120db from 20ft away. BUT, the more I think about it, perhaps we are confusing #1 and #2 for that nearfield sub. IOW, 120db sitting on a couch with the sub behind you, is going to feel much different sitting in the same couch with 120db from a sub 20ft away. Perhaps this is because the nearfield placement is better at physically shaking the couch and we perceive that as more of a tactile feeling. But if we were to remove the couch, 120db would actually feel the same nearfield as it does from 20ft away?

In your example above I assume the hypothetical figure of 120dB is as measured at the listening position? Because if you were talking about 120dB as output at the sub, then of course there is some loss as the distance gets farther (in your example behind the couch vs 20ft away).

For punch we often hear people recommending a nearfield sub placement. Is this simply so that the sub has to work less hard to produce a given spl or is there some other factor at play? confused.gif Do pressure waves have velocity? If so, does this decrease over distance?
post #59 of 96
Quote:
Originally Posted by dominguez1 View Post

Again, not exact my any means, but the tool to measure #1 could be something like the vibration meter in the Mercali Scale. I'm not directly trying to measure the pressure waves, but the affect that the waves have by 'shaking' the physical objects that are in contact with your body. I peaked around 7 on that scale. If MK measured, and peaked around 10 in his room, now I have somewhat of a frame of reference of what the 'shaking' feels like in his room compared to mine.

Unfortunately it doesn't appear to be that simple (or my room just isn't "shaking" like yours). I downloaded what appears to be the same app on my android phone and gave it a quick test just now. I threw on Bass, I Love You and cranked it up to "11". I was measuring 110dB during the 7hz and 16hz tones but was only getting peaks of ~3 (measured on the RS digital SPL meter - uncorrected, slow, max). I initially was holding the phone but didn't get hardly anything at all so I tried setting the phone on the floor and on an end table. I got the highest peaks on the end table where the phone was bouncing around visibly so I'm skeptical that I just have less "shake"...

Background: Sub is an IB "outie" manifold with 4 drivers opposed to reduce vibration. Room is my living room, nothing special, above ground with a basement underneath. Open to the rest of the house so it doesn't pressurize very easily.

I just happened to think it probably has more to do with the phone. I loaded the app just now and tried shaking my phone. I had a hard time getting it to go above 5. I had to shake it VERY hard and managed to get a 7.4 reading. I see there's a calibrate option, any idea how to go about calibrating this? Phone is a Motorola Droid Bionic.
post #60 of 96
Thread Starter 
Quote:
Originally Posted by lennon_68 View Post

Unfortunately it doesn't appear to be that simple (or my room just isn't "shaking" like yours). I downloaded what appears to be the same app on my android phone and gave it a quick test just now. I threw on Bass, I Love You and cranked it up to "11". I was measuring 110dB during the 7hz and 16hz tones but was only getting peaks of ~3 (measured on the RS digital SPL meter - uncorrected, slow, max). I initially was holding the phone but didn't get hardly anything at all so I tried setting the phone on the floor and on an end table. I got the highest peaks on the end table where the phone was bouncing around visibly so I'm skeptical that I just have less "shake"...
Background: Sub is an IB "outie" manifold with 4 drivers opposed to reduce vibration. Room is my living room, nothing special, above ground with a basement underneath. Open to the rest of the house so it doesn't pressurize very easily.
I just happened to think it probably has more to do with the phone. I loaded the app just now and tried shaking my phone. I had a hard time getting it to go above 5. I had to shake it VERY hard and managed to get a 7.4 reading. I see there's a calibrate option, any idea how to go about calibrating this? Phone is a Motorola Droid Bionic.
I am using the HTC Thunderbolt. My calibration settings say 30+12 (not sure what that means). But when I adjust the 12 to a higher number, it becomes more sensitive. What does yours say?

Why don't we calibrate all them this way. Make sure your phone does not have a case and is on a flat surface. Run the app and tap just right below the graph so it does not reset the meter. The tap should be just a normal tap; not too hard and not to soft. When I do this, I typically register from .75 to 1.25 on the scale. Adjust your calibration so that when you tap, it is generally in that range. Hopefully that will sort of calibrate our systems and you can remeasure
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