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What SPL (dBz/flat) do you start to feel the subs?

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Sonic the hedge View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic the hedge Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2021 at 7:02pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

How much experience you have being exposed to high sound pressure levels will determine the amount of tolerance you can handle under a given scenario. The person with the least amount of experience, will be easily amazed by the air pressure propagating from a single large woofer. Such individuals have a lower threshold of expectations for bass. Those who have experienced multiple large woofers playing at high sound pressure levels, will have a higher expectation to reach their level of satisfaction

The above is not limited to bass. It applies to everything in a human's life


I don't fully agree - if you pardon the pun - as KaphaSound mentioned, there are base things that trigger a visceral response in humans. These are basic evolutionary instincts so are not in any way related to experience. Since it's essentially genetic there may however be variation in how it's felt between individuals.

Originally posted by KaphaSound KaphaSound wrote:

Tinnitus Rex I believe there are sensory cells (parcinian corpuscles to be exact) in our skin that enable us to feel low frequencies (likely evolved due to predators/natural disasters etc) so the whole human body really encompasses the full sense of hearing. 

In nature loud rumbles typically always signify danger e.g. earthquake, thunderstorm, stampede etc. As such human survival instincts that have evolved over millennia subconsciously trigger an increased state of alertness and perception. This is why loud bass sounds exciting and provokes an emotional response. This response does not diminish with repeated exposure.

While repeated exposure may develop an increased perception of tolerance for loud sounds I don't believe that the underlying reaction changes; only our conscious response to it.

 In my experience a certain relatively fixed level of Bass will always provoke the same response, it's not like a drug addiction where more and more is needed due to desensitisation. IMO It's really just the level at which your skin and other body parts start to resonate. Below that point your skin doesn't pick anything up; much beyond that point additional levels have minimal effect and may actually simply become irritating, particularly if accompanied by excessive levels of midrange and HF. 

loud sound also triggers tympanic reflex which protects the eardrum from overload. This response is relatively slow - again probably because the ear damaging sound levels that exist in nature are all low in frequency, so our ears are evolved to protect against such sounds. But it does mean that the ear self-regulates in the presence of loud bass, which also reduces the level of higher frequencies reaching the eardrum incidentally.

Just my opinion/experience. Of course everyone's senses are slightly different so each individual will have a different experience. Sound is an inherently subjective experience so it important not to generalise or make assumptions about what's 'correct', IMO.







Edited by Sonic the hedge - 15 April 2021 at 9:54pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KaphaSound Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2021 at 9:19pm
Couldn’t agree more that bass heads will have a much higher tolerance for their insides being rattled than opera connoisseurs. Completely agree as well with what Sonic is saying that there is a fixed level at which point your skin starts to really resonate and vibrate, and although you can acclimatize to that sensation it is very obviously noticeable if it’s there or not, as if someone is literally hitting you with a pillow for example 40 times a second. I’ve also been trying to go down the rabbit hole of converting spl to force and then trying to find a list of examples of forces to see if for example 120db equals being hit by a paperclip, but this has not been fruitful understandably because it is very dependent on high vs low frequencies.

I would still think though that many members here have taken many SPL measurements without crazy distortion levels as citizensc pointed out and have a fairly consistent idea of what they consider a satisfactory level of tactile sensation. I know this will differ from person to person but I’m really still just curious what everyone’s personal satisfactory levels are. 

So far between Reddit and this thread there have been north of 70 comments and only 1 comment gave a number: 100dBc “at 6' with a D2 (about 70hz) note will rattle you but a D1 (about 37 hz) is def better feeling”. So that’s at most 105-110dBz. I’ve heard in this forum before that 115dBz isn’t really all that impressive, so my guess is minimum 115+ might be closer to what I’d like to be able to provide for maybe 50-200 people, with the real speaker freakers at the front getting a good bass bath. I definitely intend on taking this kind of measurement when I do have a stack and no noise restrictions, but until then the idea is to make sure I’ll be able to provide enough so any other thoughts on a rough number would be greatly appreciated!


Edited by KaphaSound - 16 April 2021 at 5:42am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tinnitus Rex Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2021 at 9:30pm
Perhaps I could sell a very expensive box with two LEDs on it one RED that means "insufficient" and one GREEN that means "sufficient".( this would really confuse DJs).. Remenber ,"no gain without pain".
I can't make you sound good, I can make you sound better
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2021 at 9:37pm
Originally posted by martinsson martinsson wrote:

What is the relation between sound intensity  (W/m2) and SPL (dB) and how do these couple to the physical sensation? I have been given to understand (told) that these are equal and follow eachother, but I cannot recall it being explained to me, the reason I mention this is a suspicion that they might differ and that this may explain why a greater coupling area (apart from directivity aspects) may render a more physical experience earlier on the SPL scale.


Efficiency is a metric of acoustic power output, which translates to sound intensity. The acoustic sound power of a loudspeaker is given for a spherical field - it has no directional component. Sensitivity is taken on-axis, and is subject to directivity. A less efficient loudspeaker may have a larger sensitivity value on the spec sheet because of the directivity.

You can’t really talk about output without understanding both, and you can convert between the two once you do.

Larger stacks of subs will radiate differently than smaller ones. There’s a change in directivity, but also a change in acoustic impedance.

I forget who asked about studies but the short answer is yes, a fair few tests along those lines and plenty of others. If you don’t want to hit up Google Scholar, then I’d suggest getting some of those things called books. They might not be cool, but this is a field of science and as such there’s quite a lot of stuff written down and looking at some equations and graphs will do a lot more for your understanding than the occasional inebriated subjective assessment of apples and oranges.

The one place that research has lacked in somewhat is large scale low frequency noise propagation for music, at gig levels. The most comprehensive investigation into whole body vibration belongs to NASA, and can be easily found online. It’s a bit of a monster but there are some fun experiments contained within.
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2021 at 9:58pm
Originally posted by Sonic the hedge Sonic the hedge wrote:

Originally posted by Elliot Thompson Elliot Thompson wrote:

How much experience you have being exposed to high sound pressure levels will determine the amount of tolerance you can handle under a given scenario. The person with the least amount of experience, will be easily amazed by the air pressure propagating from a single large woofer. Such individuals have a lower threshold of expectations for bass. Those who have experienced multiple large woofers playing at high sound pressure levels, will have a higher expectation to reach their level of satisfaction

The above is not limited to bass. It applies to everything in a human's life


I don't fully agree, if you pardon the pun as KaphaSound mentioned there are base levels that trigger a visceral response in humans. These are basic evolutionary instincts so are not in any way related to experience. Since it's essentially genetic there may however be variation in how it's felt between individuals.





The keyword is Tolerance. The level of tolerance varies from one's personal experience.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote martinsson Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2021 at 9:08am
Toastyghost, you are right, and there has been a couple of books on my desk over the years, mostly before internet though to be honest, and mainly on the topic of how to design boxes from t/s parameters.

But for sure there still is alot left to learn from books, take Leo. L. Beraneks acoustics for example, I actually have given it a try but it was a bit to heavy for me at the time, perhaps I should give it try again now that a bit more time has passed.

Sorry for drifting of topic, I think maybe my previous experiences are clouding my judgment here, my experience tells me more boxes (greater coupling area) even if at subjectively the same levels as half the number boxes does give another sensation physically in favour of the first case, but the keyword here is subjectively, chanses are the the levels differed alot and the lack of distortion or increase in range or both may have fooled me into thinking levels where similar.

This is a very old memory, standard 2241 218 br, we upped the number of boxes per side from two to four but keept the rest of the system intact, and made sure we stayed on the right side on the levels in both cases, it sounded very different in the low end, more solid and more in the chest/stomach.


Edited by martinsson - 16 April 2021 at 9:09am
Swedish Pro-fi diy-nerd - http://www.martinsson.cc/blog/
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2021 at 9:43pm
Originally posted by martinsson martinsson wrote:

This is a very old memory, standard 2241 218 br, we upped the number of boxes per side from two to four but keept the rest of the system intact, and made sure we stayed on the right side on the levels in both cases, it sounded very different in the low end, more solid and more in the chest/stomach.

The first time ever that bass made me want to move and dance was a similar setup. Outdoors, four jbl double 18" reflex bins stacked per side, powered by a bunch of CA18. It could be felt from half a mile away... ....

Hug
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 19 April 2021 at 11:32am
This paper answers your question, for both dBZ SPL (at the listener) in 1/3rd octave bands, and how that translates to physical acceleration for those same frequencies.

https://www.aes.org/e-lib/browse.cfm?elib=20383

The terms you need to use are Whole Body Vibration; it’s different for each person as we all have an individual Body Related Transfer Function. It doesn’t seem to matter if you’re fat or not.

I noticed you mentioned trying to convert sound pressure to physical measurements. That’s not difficult, sound is often measured or calculated in Pascals and converted.

They had 28 test subjects who were fitted with six accelerometers, at key points for conduction like the chest and shoulders. It’s a bloody good paper, frankly. They only used a single dual 18” French sub but that’s absolutely fine in the test environment used.

Here are the juicy bits:




Be aware these are taken out of context before you throw judgement! If you haven’t read the methodology and prior research, then you may find it hard to put aside your subconscious bias.

I won’t share the full paper, but if you’re really serious about answering these sorts of questions then the AES journals are a damn good place to start looking. Even if you don’t get everything that’s being discussed, you then have jumping off points for more research and reading, or to ask more specific questions. It isn’t ‘cheap’ but I found I got my money’s worth very quickly. Not just on journal access, but the several meets and education sessions every month.

As an aside I’m often quite shocked how many supposedly professional ‘engineers’ don’t seem to want to spend the very reasonable annual AES membership fee. I guess it doesn’t fit with the stereotype of repeating the same old waffle in a grumpy manner? 😅

If you’re a student, it’s damn cheap and takes 5 years to hit full price. Take advantage of that situation if you can!

Edited by toastyghost - 19 April 2021 at 11:34am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote madboffin Quote  Post ReplyReply Direct Link To This Post Posted: 19 April 2021 at 5:41pm
What's dBz?
All the sound measuring equipment I have used over the last 50 years has been fitted with various combinations of A, B, C, Lin (and sometimes D) scales.



Edited by madboffin - 19 April 2021 at 5:42pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 19 April 2021 at 6:41pm
Originally posted by madboffin madboffin wrote:

What's dBz?
All the sound measuring equipment I have used over the last 50 years has been fitted with various combinations of A, B, C, Lin (and sometimes D) scales.




You could probably have googled it in the time it took to post that...

Quote Z Weighting

[Z-weighting is a flat frequency response of 10Hz to 20kHz ±1.5dB. This response replaces the older "Linear" or "Unweighted" responses as these did not define the frequency range over which the meter would be linear.

Z-weighted measurements are expressed as dBZ or dB(Z).


From noisemeters.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KaphaSound Quote  Post ReplyReply Direct Link To This Post Posted: 20 April 2021 at 3:05am
Wow thank you toastyghost! This is exactly the kind of thing I’m looking for and to top it all off it’s even in dBz by frequency. I know AES have tons of papers but this one strikes me as one of the more interesting (alteast personally). I have actually done some research into body resonances which show some interesting results as far as where you may predominantly feel certain frequencies and how your build may affect this, but the threshold was never particularly clear.

From the abstract: “ Perceptual tests identified a frequency dependent threshold of 94-107dBZ required to induce a perceivable whole-body vibration.” I don’t think the answer gets more clear than that so again thank you! Just a few follow up questions: I’m assuming the black lines in the grey bars are the variations between subjective results? So what is the black line graph since it doesn’t look like an average of the grey bar trend? And is the acceleration measurement a result of both frequency and spl (apologies if this is a basic question)?

My guess based on this info is that ~130dbz should be enough for a physical experience over a space big enough for 50-200 people or so. I am hoping these horns will actually be able to hit 140 continuous down to about 32hz in groups of 4, but I’ll have to take measurements to confirm.


Edited by KaphaSound - 20 April 2021 at 4:35am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote imageoven Quote  Post ReplyReply Direct Link To This Post Posted: 20 April 2021 at 9:30am
Originally posted by toastyghost toastyghost wrote:

Originally posted by madboffin madboffin wrote:

What's dBz?
All the sound measuring equipment I have used over the last 50 years has been fitted with various combinations of A, B, C, Lin (and sometimes D) scales.




You could probably have googled it in the time it took to post that...



I'm glad he did ask, I was assuming dBz was street slang...Embarrassed
Keep pushing on, things are gonna get better.
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