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post #181 of 367 Old 05-15-2014, 08:32 PM
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Bad comparison however, as that frequency is shared by other instruments, is clearly audible, and does not take highly unusual playback capability and extremely loud SPL to produce the clearly audible effect.  rolleyes.gif

It takes as much or more capability.

The transient strike of a 10" triangle is centered at around 5k Hz and is 90dB at 1M.***

Except...nobody cares what the SPL is at 1m, except the percussionists and the horn players in front of them. Recordings generally aren't made from the perspective of the percussion section The relevant distance at which to measure its SPL is...whatever the distance from the triangle player to the seats the recording is designed to place the listener in.
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4) I say used closed boxes with decent volume displacement, equalize flat to 20Hz or so, and then whatever comes under that is a bonus. Don't hesitate to highpass if doing so kills a rattle.

I generally agree with this statement so long as the sealed subwoofer isn't high passed.

IME, sometimes the rattles aren't worth the extension.
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Your statement about humans being less sensitive to changes in SPL at lower and lower frequencies is exactly the opposite of what I pointed out above, and is entirely incorrect once above the threshold of hearing.***

Honestly, I don't care enough about the super-low stuff to argue further, but it's counter to intuition and experience to suggest that we're more sensitive to level differences at the extremes than we are in the midrange.
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post #182 of 367 Old 05-15-2014, 08:44 PM
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It's a bad comparison because the sound a triangle makes is in the normal audible frequency range and is more easily produced by common, affordable equipment.  You are correct that my subs cannot produce that frequency...I decided that, for me personally, it was not a worthwhile pursuit.  I had 100+ dB playback capability down to 10 Hz and could have accommodated doubling that output, but found that frequencies below 16 Hz produced no noticeable effect in my room.  I chose to pursue 16+.  I have not seen the movie with the 5 second 6 Hz clip, but I am confident I am not missing much by not being able to replicate that tiny clip with its subtle sensation for a couple secs.  Just my opinion though, I know others feel differently, and that is totally fine.  After all, this is a hobby and people are free to pursue whatever capabilities they choose.

Trust me, you aren't missing much. That movie has so much cheesy dialogue and aimless gunfire that it becomes dreadfully boring. It appears the movie gets better once you've invested thousands to hear 6 seconds of it though, lol.
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post #183 of 367 Old 05-15-2014, 09:16 PM
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Edited to quote:
Craig, that is not correct.

The "Inverse Square Law" (ISL) still applies when there are boundaries. It's just that the ISL is applicable to each and every source of sound pressure. When you add boundaries (a room), you add sources and the ISL is applicable to all of them. In a room, the net result of the ISL's -6dB/dd attenuation and these multiple additional sources (walls, floor, ceiling, furniture) is often significantly less loss of SPL. This result may be expressed as a reduced attenuation with distance (say to the listening position), but that doesn't mean the ISL only applies when there are no boundaries.

I agree that around -3dB/dd is a good rule of thumb for the result in typically furnished domestic rooms.
.
While this discussion may seem like pedantic semantics, the fact remains that the Inverse Square Law applies *only* to a single source of sound. It is based entirely on a single, anechoic propagation of a single soundwave.



Anything that impacts that single anechoic propagation of the soundwave will impact the concomitant sound wave. However, that is not addressed in the ISL primarily. The ISL only addresses what happens to a soundwave with no boundary reinforcement.

What happens to a soundwave AND ITS' CONCOMITANT REFLECTIONS off the regional boundaries, (i.e., in an enclosed space), is whole different discussion... as you've noted above, and with which I completely agree.

Again, this is a "pedantic semantics" discussion. wink.gif

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post #184 of 367 Old 05-15-2014, 09:22 PM
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Trust me, you aren't missing much. That movie has so much cheesy dialogue and aimless gunfire that it becomes dreadfully boring. It appears the movie gets better once you've invested thousands to hear 6 seconds of it though, lol.

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post #185 of 367 Old 05-15-2014, 10:34 PM
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4) I say used closed boxes with decent volume displacement, equalize flat to 20Hz or so, and then whatever comes under that is a bonus. Don't hesitate to highpass if doing so kills a rattle.

I generally agree with this statement so long as the sealed subwoofer isn't high passed.

IME, sometimes the rattles aren't worth the extension.

That's certainly the easy/lazy approach, and sometimes needed when the system is open to a space like a kitchen. In any sort of dedicated area the rattles should be eliminated mechanically with foam, felt screws or glue. These are the lowest cost improvements in most systems with the possible exception of vibrating HVAC ductwork. Taking the point further, we would never recommend castrating a system with a brickwall at 26Hz if the projector vibrates violently at 22-24Hz... we would give suggestions on how to properly re-mount the projector.
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Your statement about humans being less sensitive to changes in SPL at lower and lower frequencies is exactly the opposite of what I pointed out above, and is entirely incorrect once above the threshold of hearing.***

Honestly, I don't care enough about the super-low stuff to argue further, but it's counter to intuition and experience to suggest that we're more sensitive to level differences at the extremes than we are in the midrange.

It's only counter intuitive if you're mistaking a high threshold of hearing for lack of sensitivity. In evolutionary terms such reaction makes perfect sense as there are many low level VLF sources in nature, but it's quite important we take note of the loud ones. Of course there's no intuition required as you can directly read what I describe off the graph as I explained.

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post #186 of 367 Old 05-15-2014, 10:35 PM
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Bad comparison however, as that frequency is shared by other instruments, is clearly audible, and does not take highly unusual playback capability and extremely loud SPL to produce the clearly audible effect.  rolleyes.gif

It takes as much or more capability.

The transient strike of a 10" triangle is centered at around 5k Hz and is 90dB at 1M.***

Except...nobody cares what the SPL is at 1m, except the percussionists and the horn players in front of them. Recordings generally aren't made from the perspective of the percussion section The relevant distance at which to measure its SPL is...whatever the distance from the triangle player to the seats the recording is designed to place the listener in.



Along that same line of thinking I was going to mention the distance from the triangle to to the conductor. What SPL level does he hear the triangle SPL let alone what SPL level does the audience (or microphone) hear?




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Your statement about humans being less sensitive to changes in SPL at lower and lower frequencies is exactly the opposite of what I pointed out above, and is entirely incorrect once above the threshold of hearing.***

Honestly, I don't care enough about the super-low stuff to argue further, but it's counter to intuition and experience to suggest that we're more sensitive to level differences at the extremes than we are in the midrange.



Mark is quite right.

If you follow the equal loudness curves, let's say that you turn down your master volume to 10 dB below calibrated reference level. At 1K Hz, the volume is decreased by 10 dB SPL by definition between adjacent 10 dB spaced phon curves. However per the equal loudness curves, 10Hz content should only decrease by 5 dB due to the spacing of the same adjacent 10 dB phon curves if you want to maintain the same balance based on what you hear. So if you playback with your master volume set to 10 dB below the reference level setting, the 10 Hz should be boosted by 5 dB to maintain balance per the adjacent ELC (10 dB @ 1 K Hz and 5 dB @ 10 Hz)..

Mark made the same point but in a different manner. He said that if you increase the master volume by 10 dB SPL @ 1K Hz, you jump two EL curves at 10 Hz when you increase the master volume by 10 dB @ 1K Hz.

Not sure how that works out for "feeling" the bass. The ELC does not apply to "feelings"!
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post #187 of 367 Old 05-15-2014, 11:31 PM
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Quote:
Originally Posted by craig john View Post

Quote:
Originally Posted by GIEGAR View Post

Edited to quote:
Craig, that is not correct.

The "Inverse Square Law" (ISL) still applies when there are boundaries. It's just that the ISL is applicable to each and every source of sound pressure. When you add boundaries (a room), you add sources and the ISL is applicable to all of them. In a room, the net result of the ISL's -6dB/dd attenuation and these multiple additional sources (walls, floor, ceiling, furniture) is often significantly less loss of SPL. This result may be expressed as a reduced attenuation with distance (say to the listening position), but that doesn't mean the ISL only applies when there are no boundaries.

I agree that around -3dB/dd is a good rule of thumb for the result in typically furnished domestic rooms.
.
While this discussion may seem like pedantic semantics, the fact remains that the Inverse Square Law applies *only* to a single source of sound. It is based entirely on a single, anechoic propagation of a single soundwave.



Anything that impacts that single anechoic propagation of the soundwave will impact the concomitant sound wave. However, that is not addressed in the ISL primarily. The ISL only addresses what happens to a soundwave with no boundary reinforcement.

What happens to a soundwave AND ITS' CONCOMITANT REFLECTIONS off the regional boundaries, (i.e., in an enclosed space), is whole different discussion... as you've noted above, and with which I completely agree.

Again, this is a "pedantic semantics" discussion. wink.gif

Craig

GIEGAR is technically right on the semantics here. wink.gif Sound waves do not interfere with or confine each other (until super high SPL). They sum locally where ever they are both present and observed, but continue on just as if there was no other sound present.

The confusion of how sound travels or falls off over distance generally comes from rules of thumb or ideal conditions that often don't really exist. Even line and planar sources behave perfectly as an integration of points which fall off at 20dB per 10x the distance (typically approximated to -6dB per doubling). For specific cases of an infinite line or plane of continuous point sources sound is observed to sum such that it approximates a 3dB loss per doubling of distance for a line, or no loss vs. distance for a plane. Of course the real world deals in non-continuous elements of finite dimensions.

This does have some application in understanding what happens in a room. For larger acoustic spaces we see a more clear point where the reverberant sound energy becomes equal to the direct sound from the speaker. Acousticians commonly refer to this as the critical distance. The behavior of the speaker and the acoustics of the space determine how far the critical distance is from the speaker at different frequency bands. While somewhat simplified, this link shows a good graphic explaining the situation. Beyond this distance the sound reflected from all surfaces dominates and we find the sound level mostly remains the same as you move further away:





At very low frequencies, speakers spray sound in all directions, and rooms are very reflective, making this distance quite close to the subwoofer. While room modes complicate things, this is exactly the effect observed in the measurements Bosso' posted. In some cases this distance may only be 1m away at low frequencies. As a result, we see that depending on room size and construction, beyond 2-4m you see very little loss from distance and mostly variation due to room mode intensity. Anyone with a 2nd or 3rd row of seating against the back wall knows a portion of the frequency range will be louder near the back wall than in the middle of the room.

The last point to add to this is another common misunderstanding relating to filling larger and larger spaces with deep bass. While larger rooms do require more power, it is not a linear and continuous scaling. A simple distance and loading of the front wall sets a maximum reduction you can observe at your listening distance from subwoofers at the front wall. The way some mistakenly describe the issue you would think bass was impossible to create outdoors. With sufficient SPL you can most certainly create a pant-leg flapping HT experience outdoors as was done with this setup Keith Yates assembled and kept adding to over the years in his backyard (that's me behind the top left of the screen):

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post #188 of 367 Old 05-16-2014, 05:35 AM
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Let me assure you, measured with over a $2500 measurement rig, the graph is accurate, and the mic is measured and tested flat to 2hz.

Not really that expensive to do room treatments correctly if you know what you are doing, or utilize the excellent folks at GIK. They will run through a full room treatment suite with you if you just give them your information. My panels, front wall treatment, ceiling, rear wall etc are all treated. By "that expensive" I have less than $1k in all the panels that are needed, and I prefer a more dead room than most. I venture to say between my room treatments, sub system, and amplification, (all DIY) that I am still under the cost of a single JL fathom, and ridiculously more capable than even 6 of them. This is not a DIY plug at all, just pointing out that room treatments and anything else HT can be cheap if you just spend a little time researching exactly what you need and what works best for your room.

This was not refuted, you just have some things backwards it appears. You seem to be close to understanding it all, but over the past 20 or so posts there is plenty of explanation to correct any misunderstanding you might have had smile.gif

I guess if you dampen all the surfaces, including the floor and ceiling, to greatly reduce or eliminate all reflections, you can accurately reproduce the long wavelengths in a small room. You would effectively make the room much larger from an acoustical point of view. The downside to doing this is you would lose room gain and hence would require some very powerful subs to compensate for that. Is it doable? yes. Does it cost a lot of money? To me, it would be expensive. You would spend probably 5x what a good system down to 20 Hz would cost to get down to single digits. Not worth it to me, but to others I guess it is.
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post #189 of 367 Old 05-16-2014, 05:47 AM - Thread Starter
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Let me assure you, measured with over a $2500 measurement rig, the graph is accurate, and the mic is measured and tested flat to 2hz.

Not really that expensive to do room treatments correctly if you know what you are doing, or utilize the excellent folks at GIK. They will run through a full room treatment suite with you if you just give them your information. My panels, front wall treatment, ceiling, rear wall etc are all treated. By "that expensive" I have less than $1k in all the panels that are needed, and I prefer a more dead room than most. I venture to say between my room treatments, sub system, and amplification, (all DIY) that I am still under the cost of a single JL fathom, and ridiculously more capable than even 6 of them. This is not a DIY plug at all, just pointing out that room treatments and anything else HT can be cheap if you just spend a little time researching exactly what you need and what works best for your room.

This was not refuted, you just have some things backwards it appears. You seem to be close to understanding it all, but over the past 20 or so posts there is plenty of explanation to correct any misunderstanding you might have had smile.gif

I guess if you dampen all the surfaces, including the floor and ceiling, to greatly reduce or eliminate all reflections, you can accurately reproduce the long wavelengths in a small room. You would effectively make the room much larger from an acoustical point of view. The downside to doing this is you would lose room gain and hence would require some very powerful subs to compensate for that. Is it doable? yes. Does it cost a lot of money? To me, it would be expensive. You would spend probably 5x what a good system down to 20 Hz would cost to get down to single digits. Not worth it to me, bit to others I guess it is.

 

This thread has some of the best-ever comments about how bass works. Mark Seaton is shared some really good insights that are worth re-reading.

 

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It's a bad comparison because the sound a triangle makes is in the normal audible frequency range and is more easily produced by common, affordable equipment.  You are correct that my subs cannot produce that frequency...I decided that, for me personally, it was not a worthwhile pursuit.  I had 100+ dB playback capability down to 10 Hz and could have accommodated doubling that output, but found that frequencies below 16 Hz produced no noticeable effect in my room.  I chose to pursue 16+.  I have not seen the movie with the 5 second 6 Hz clip, but I am confident I am not missing much by not being able to replicate that tiny clip with its subtle sensation for a couple secs.  Just my opinion though, I know others feel differently, and that is totally fine.  After all, this is a hobby and people are free to pursue whatever capabilities they choose.

Trust me, you aren't missing much. That movie has so much cheesy dialogue and aimless gunfire that it becomes dreadfully boring. It appears the movie gets better once you've invested thousands to hear 6 seconds of it though, lol.

 

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post #190 of 367 Old 05-16-2014, 06:09 AM
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I would actually like to hear a system that hits below 10hz with a fair amount of demonstration source material. It would be more straightforward to judge whether it was "worth the money" to go below 16hz.

My system is at -3db at 16hz and I would bet the drivers would bottom out if I tried to PEQ boost much in that range. After careful remeasurement (assuming a UMIK is accurate), i think at 10db I am at -12db.

I do love the bass in my room now and its about as deep and loud as is reasonable to get in this particular house. I do like always gathering knowledge for the next build though...

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post #191 of 367 Old 05-16-2014, 06:22 AM
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Originally Posted by KidHorn View Post

I guess if you dampen all the surfaces, including the floor and ceiling, to greatly reduce or eliminate all reflections, you can accurately reproduce the long wavelengths in a small room...

You can't eliminate reflections at long wavelengths in a residential room with absorption. That's just not how it works. No one has space for 20' of fiberglass, yet we still are able to produce ULF.
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post #192 of 367 Old 05-16-2014, 09:42 AM
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Finally checked my Sub performance.

My wife heard the 20 Hz test-tone in the next room and we felt the 16 Hz tone. Seems like my system is pretty capable. Subwoofer is a 300 Watt sinus Nubert, a German company that sells only direct from factory. Price in 1998 was $ 1.100. Still happy with the performance. A second one will come anyways at one time or another.
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post #193 of 367 Old 05-16-2014, 09:56 AM
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Quote:
Originally Posted by KidHorn View Post

Quote:
Originally Posted by beastaudio View Post

Let me assure you, measured with over a $2500 measurement rig, the graph is accurate, and the mic is measured and tested flat to 2hz.

Not really that expensive to do room treatments correctly if you know what you are doing, or utilize the excellent folks at GIK. They will run through a full room treatment suite with you if you just give them your information. My panels, front wall treatment, ceiling, rear wall etc are all treated. By "that expensive" I have less than $1k in all the panels that are needed, and I prefer a more dead room than most. I venture to say between my room treatments, sub system, and amplification, (all DIY) that I am still under the cost of a single JL fathom, and ridiculously more capable than even 6 of them. This is not a DIY plug at all, just pointing out that room treatments and anything else HT can be cheap if you just spend a little time researching exactly what you need and what works best for your room.

This was not refuted, you just have some things backwards it appears. You seem to be close to understanding it all, but over the past 20 or so posts there is plenty of explanation to correct any misunderstanding you might have had smile.gif

I guess if you dampen all the surfaces, including the floor and ceiling, to greatly reduce or eliminate all reflections, you can accurately reproduce the long wavelengths in a small room. You would effectively make the room much larger from an acoustical point of view. The downside to doing this is you would lose room gain and hence would require some very powerful subs to compensate for that. Is it doable? yes. Does it cost a lot of money? To me, it would be expensive. You would spend probably 5x what a good system down to 20 Hz would cost to get down to single digits. Not worth it to me, but to others I guess it is.

As Mark (imagic) already suggested, please go back and re-read my response to you earlier in this thread. You are still confusing sound creation/recording with reproduction.
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post #194 of 367 Old 05-16-2014, 10:58 AM
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The transient strike of the triangle in the 60 piece orchestra last miliseconds. Probably should cut it out of the mix then. rolleyes.gif

Damn right. F**k that triangle! I came here for brass and strings.

wink.giftongue.gif

Hahah
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post #195 of 367 Old 05-16-2014, 11:22 AM
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Just contributing some graphs... while everyone is focusing on movies, music is getting overlooked a bit. I mic'd this at my desk in the back of my room just to show how much low frequency content there actually is in music. This is with my current setup. The mic is a generic capsule plugged directly into my pc's sound card, no idea on low frequency rolloff, but I imagine there's a little bit going on there which is unaccounted for in the graphs.


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post #196 of 367 Old 05-16-2014, 11:30 AM
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You're delusional, Rob what with all that empirical evidence of ULF in .....things.

Also. You have wasted all your money attempting to recreate these signals in your home.

Thumbs down and my butt hurts.
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post #197 of 367 Old 05-16-2014, 11:51 AM
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I agree with imagic, this thread has turned into a treasure chest of good information on bass. Thanks to all who are taking the time to share their knowledge. Also thanks to all who have shared photos of some seriously intense systems. Keep it all coming, it's turned into a pretty cool thread.  :cool:

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post #198 of 367 Old 05-16-2014, 12:12 PM
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Every time i have improved my subwoofer capability, nearly all my music has sounded better and you can hear bass frequencies in music that were not obvious before. I use 2.x for music with a crossover at 80hz and i get a much smoother overall response. I dont get any sense that I can sense the direction that sub 80hz is coming from. With 4 subs 8 drivers (one per corner, all hidden behind fabric) I bet anyone that while seated, you can't figure out precisely where the subs are actually located or how many there are. During music, they just blend in without distractions.

With this setup I am easily getting the bass performance of the Utopia speakers or wilson speakers (full range) that I have had a chance to audition. There is no obvious loss of stereo imaging or the sense that sounds are coming from the wrong place. In audition conditions those other speakers may not even have a linear in-room response without PEQ and additional subwoofers for placement flexibilityade still going to be needed. I am not a believer in "full range speakers" anymore and I find much more cost effective speaker sizes are available when all true bass performance is delgated to multiple and positionable subwoofers.

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post #199 of 367 Old 05-16-2014, 12:21 PM
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Originally Posted by notnyt View Post

Just contributing some graphs... while everyone is focusing on movies, music is getting overlooked a bit. I mic'd this at my desk in the back of my room just to show how much low frequency content there actually is in music.
While you're at it do a chart with nothing actually playing. You'd be surprised to find how much VLF energy there is in the average home that you're unaware of because it's not loud enough for you to hear it. I became acutely aware of environmental VLF background noise when doing concert sound RTAs that showed a constant 50-55dB base level from 20 to 32Hz, whether the band was playing or not. The source? Everything from people walking to refrigeration equipment to traffic on roads 2 miles away. It never interfered with the concert sound, being well below the threshold of audibility, but the measurement gear had no difficulty reading it.

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post #200 of 367 Old 05-16-2014, 12:29 PM
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How low (and how loud)? When your vision blurs and confusion, dizziness and nausea take over and your underwear is damp... it's low and loud enough.
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post #201 of 367 Old 05-16-2014, 12:32 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

While you're at it do a chart with nothing actually playing. You'd be surprised to find how much VLF energy there is in the average home that you're unaware of because it's not loud enough for you to hear it. I became acutely aware of environmental VLF background noise when doing concert sound RTAs that showed a constant 50-55dB base level from 20 to 32Hz, whether the band was playing or not. The source? Everything from people walking to refrigeration equipment to traffic on roads 2 miles away. It never interfered with the concert sound, being well below the threshold of audibility, but the measurement gear had no difficulty reading it.

I'm pretty sensitive to vlf, and can generally hear/feel when there's a car idling down the block, which the mic will indeed pick up. It's pretty interesting... HVAC will show up often as well. I also live near the water, so I get sounds from the ocean and wind popping in there as well.

It's pretty quiet at the moment, bit of wind...

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post #202 of 367 Old 05-16-2014, 01:11 PM
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Let me assure you, measured with over a $2500 measurement rig, the graph is accurate, and the mic is measured and tested flat to 2hz.

Not really that expensive to do room treatments correctly if you know what you are doing, or utilize the excellent folks at GIK. They will run through a full room treatment suite with you if you just give them your information. My panels, front wall treatment, ceiling, rear wall etc are all treated. By "that expensive" I have less than $1k in all the panels that are needed, and I prefer a more dead room than most. I venture to say between my room treatments, sub system, and amplification, (all DIY) that I am still under the cost of a single JL fathom, and ridiculously more capable than even 6 of them. This is not a DIY plug at all, just pointing out that room treatments and anything else HT can be cheap if you just spend a little time researching exactly what you need and what works best for your room.

This was not refuted, you just have some things backwards it appears. You seem to be close to understanding it all, but over the past 20 or so posts there is plenty of explanation to correct any misunderstanding you might have had smile.gif

I guess if you dampen all the surfaces, including the floor and ceiling, to greatly reduce or eliminate all reflections, you can accurately reproduce the long wavelengths in a small room. You would effectively make the room much larger from an acoustical point of view. The downside to doing this is you would lose room gain and hence would require some very powerful subs to compensate for that. Is it doable? yes. Does it cost a lot of money? To me, it would be expensive. You would spend probably 5x what a good system down to 20 Hz would cost to get down to single digits. Not worth it to me, but to others I guess it is.
You REALLY don't understand the physics of acoustics and recording/playback do you?

You can reproduce wavelengths longer than the room. Yes, reflections from room boundaries can create peaks and nulls in the response, but those can be sorted with proper placement, EQ and treatment to produce accurate playback.

Recording is a a whole different ballgame. If you've EVER been involved in studio audio recording (as opposed to just reading stuff on the internet without really understanding it), you would be aware of several simple principles:
- recording in enclosed spaces potentially means capturing the space's reflections, reverberations and echoes. In small spaces like studio environments, this is usually undesirable as playback tends to mean a doubling of the effect (i.e. if you record the reflections and reverberations of the recording space, when you play it back, you have the reflections and reverberations of the small recording space AND the reflections and reverberations of the playback space on top of that which sounds like crap).
- In studio recording, the goal is to eliminate all that with acoustic treatment so you can capture the pure sound of the instrument or vocalist, without the recording space's reflections and reverberations. When the recording is mixed, it is possible to add reverb back in to produce the ambient sound desired, but it's much more difficult to try to remove it if it's in the actual recording
- Yes, some recordings actually strive to capture the ambience of a recording space by capturing the reverberations, but these are generally recordings in much larger spaces (like 2L's penchant for recording small ensembles in old churches etc.)

The practices for recording studios vs playback spaces are completely different things for completely different reasons. If you've ever been in a recording studio sound booth, you'd know how dead they sound as the acoustic treatment's goal is to kill reflections that might be captured by the mic. Most folks who are unused to it get a little uncomfortable being in one after a little while because they aren't used to the quiet and lack of reflected sounds/echoes.

If accurate playback of wavelengths longer than the room wasn't possible, all CD, DVD and BD audio tracks would be filtered at 60Hz since that wavelength is about 18.8 feet and most rooms that these tracks would be played in won't be much bigger than that, and we know how ridiculous THAT notion is.


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post #203 of 367 Old 05-16-2014, 02:36 PM
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To summarize, what changed my mind was those damn spectrographs of the digital content. It actually shows you what is on a disc! Dammit, if it is on the disc I want it and I want it in a big cinematic way. Why don't you guys start doing digital graphs of the whole movie and whole frequency range and when a movie does not have much above 10khz you could low pass it then, right?
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post #204 of 367 Old 05-16-2014, 02:48 PM
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In designing vibration isolation systems that involve humans (things like automobile suspensions, elevators, bridges and floors in buildings), design rules usually try to minimize acceleration in the range of 2-12 Hz or so. The exact numbers depend upon the application but this is a range of extreme human sensitivity due to resonances in the body cavity and other factors.

It stands to reason that we would also be keyed in to this same frequency range in a tactile sense from high SPL levels. So even though these frequencies are below the range of hearing, the human body is quite sensitive to them. While this translates to discomfort if experienced for extended periods in a car, it would seem to me that it also provides awesomeness in a transient home theater experience.

Folks with transducers are producing these accelerations more directly on a couch or riser. Doing this by creating pressure waves in a large room isn't the most efficient solution in the sense of power consumption but sure is cool. I have a mere two 18" drivers in a concrete basement with a lot of room gain but even for me boosting the 8-20Hz range makes for a completely different movie experience.
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post #205 of 367 Old 05-16-2014, 03:19 PM
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Quote:
Originally Posted by notnyt View Post

I'm pretty sensitive to vlf, and can generally hear/feel when there's a car idling down the block, which the mic will indeed pick up. It's pretty interesting... HVAC will show up often as well.
I recently did a consult for a major installation of my cabs and the owner was giddy when he saw what he was getting at 20Hz, until we turned the system off and the 20Hz didn't change. It was his HVAC, which had a register directly above the FOH where we took the RTA. rolleyes.gif

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post #206 of 367 Old 05-16-2014, 03:26 PM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post

Quote:
Originally Posted by notnyt View Post

I'm pretty sensitive to vlf, and can generally hear/feel when there's a car idling down the block, which the mic will indeed pick up. It's pretty interesting... HVAC will show up often as well.
I recently did a consult for a major installation of my cabs and the owner was giddy when he saw what he was getting at 20Hz, until we turned the system off and the 20Hz didn't change. It was his HVAC, which had a register directly above the FOH where we took the RTA. rolleyes.gif

When I take measurements, the difference between ambient vibrations and actual sub-20 Hz bass is massive; and from a sensory perspective, guttural. Very different from passing trucks, hvac, and etc. I can definitely sense that stuff though, when it's present. It might even be because as a photographer I became acutely aware of vibrations that could affect tripod-mounted telephoto shots.

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post #207 of 367 Old 05-16-2014, 03:28 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

I recently did a consult for a major installation of my cabs and the owner was giddy when he saw what he was getting at 20Hz, until we turned the system off and the 20Hz didn't change. It was his HVAC, which had a register directly above the FOH where we took the RTA. rolleyes.gif

Lol!

Now that is a true, "Wah wahhhh" situation right there. tongue.gif

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post #208 of 367 Old 05-16-2014, 03:58 PM
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Originally Posted by imagic View Post

Quote:
Originally Posted by Bill Fitzmaurice View Post

Quote:
Originally Posted by notnyt View Post

I'm pretty sensitive to vlf, and can generally hear/feel when there's a car idling down the block, which the mic will indeed pick up. It's pretty interesting... HVAC will show up often as well.
I recently did a consult for a major installation of my cabs and the owner was giddy when he saw what he was getting at 20Hz, until we turned the system off and the 20Hz didn't change. It was his HVAC, which had a register directly above the FOH where we took the RTA. rolleyes.gif

When I take measurements, the difference between ambient vibrations and actual sub-20 Hz bass is massive; and from a sensory perspective, guttural. Very different from passing trucks, hvac, and etc. I can definitely sense that stuff though, when it's present. It might even be because as a photographer I became acutely aware of vibrations that could affect tripod-mounted telephoto shots.

And extreme enlargements... Rodagon-G anyone?biggrin.gif
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post #209 of 367 Old 05-16-2014, 06:54 PM
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Personally, I value having linearity down deep, but not necessarily do I need my system to play linear "at reference."

In short, reference level is insanely loud, and not something I find pleasant to deal with for 2 hours while watching a movie. As such, my system can stay linear much lower, because it isn't being demanded to play so darn loudly.

Perhaps I just don't know any true bassheads, but nobody I've ever demo'd a clip for, at reference volume, has asked to watch an entire movie at that level.

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post #210 of 367 Old 05-16-2014, 07:10 PM
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Quote:
Originally Posted by Suntan View Post

Personally, I value having linearity down deep, but not necessarily do I need my system to play linear "at reference."

In short, reference level is insanely loud, and not something I find pleasant to deal with for 2 hours while watching a movie. As such, my system can stay linear much lower, because it isn't being demanded to play so darn loudly.

Perhaps I just don't know any true bassheads, but nobody I've ever demo'd a clip for, at reference volume, has asked to watch an entire movie at that level.

-Suntan

I generally run about -12 or -8db reference so I think you are right about most folks not watching at full volume.

Just got done watching godzilla at the theater and the sound system there sucked despite it being a 3d theater. The only useful screen at our theater is the imax certified one. The bass in my own house blows away most of our theater experiences near us.

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