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ok basically lets say i can hear to about 22 hz.


if i cut off at 22 hz then if i want the bass to shake me then i will also hear it and it may not be something that was intended to be heard, only felt.


therefore response must extend below audibility to enable effects which are tactile ONLY with no audible coloration of program.


also response must go low enough to enable all tactile sensation mechanisms. for example if chest resonates at 40 hz and the system doesn't go that low then it is unable to tap into this sensation.


but what is the lowest such frequency that is relevant ? there are no resonances in the body below 20 hz.


furthermore your clothes and hair don't vibrate from air pressure, but from air movement. and air movement diminishes below room pressurization frequency - at lowest frequencies indoors you have pressure, but no movement. room pressurization begins at around 30 hz depending on room size.


the only thing left below 20 hz that is of interest is building resonances - but those can simply be taken care by bass shakers.


so i propose that we need a band below 22 hz ( or whatever is deemed threshold of audibility ) for certain special effects like making pants flutter but this band doesn't need to be wider than a few HZ - it just needs to exist. so lets say this band can be 12 hz - 22 hz.


and then if you want extra room shaking just add bass shakers - they will shake your room at least as well as subwoofers but take up NO space.


of course you can't completely fool the brain. a system with acoustic response to DC is still going to have a better slam ( not more powerful, but better ) in the chest but i think the cost benefit in trying to go after frequencies below 12 hz or so is not there.


also now i am thinking if you want to get your hair and pants to move about then double bass array is the only technology that will do it properly. and multiple geddes / welti style subs will actually be the WORST for this - as they tend to pressurize the air without moving it.
 

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Good to see you back, glad to see you havent changed!
 

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Yeah,but some people want 5 hz.
I think someone here claimed that with a 4 inch woofer.
 

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I was playing some test tones on my two FI Q18 ported bad boys and got things rattling pretty easy on 7hz and that was only on volume -20db on the onkyo. I believe Bassotronics I love you has some 8hz frequencies in it and I love it.


I take it you don't watch films like the hulk, black hawk down, pulse, wotw etc.... blah blah blah.


Anyone who thinks that low frequencies are pointless go wash your mouth out with soap.


cheers


Graham
 

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Quote:
Originally Posted by gperkins1973 /forum/post/18233125


I was playing some test tones on my two FI Q18 ported bad boys and got things rattling pretty easy on 7hz and that was only on volume -20db on the onkyo.

When you run test tones run an RTA as well and see what's actually there. It's almost impossible to play a sine wave and not have significant harmonic content, even with laboratory grade gear. Compare the audibility of those harmonics versus the fundamental on equal loudness curves at the playback level. In most cases what you're hearing isn't the fundamental, it's the harmonics (that's how BassMaxx works). As for the fundamentals, you can feel those if they're at high enough levels. In a home the room sizes are small enough to get adequate pressurization to feel what can't be heard. But in larger spaces the power required for infra-sonic pressurization is so high that manufacturers don't even attempt to build cabs capable of doing so, not even those intended for IMAX installs.
 

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He's baaaaaaaaack! All this time away and this is the best you can come up with? No crazy diagrams of flux or any of that crap, just this low frequencies are pointless argument that's been rehashed on this board time and time again? I don't really care to play along but I have two letters that destroy your whole point (although not viable for the majority):


IB
 

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All these comments and he hasn't responded. I didn't realise he was well known on here. Perhaps he's gone again to build himself some nice high tune subs so he can listen to some lovely classical music.


cheers


Graham
 

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While the OPs title was certainly "inflammatory" his actual claim is not. He is not saying low frequencies are pointless, just that it may be more practical to reproduce their effects with a tactile transducer below the audible range instead of huge cone movement and their accompanying huge footprint. Not at all an absurd statement, but one which for many works out better than an IB array due to room or size limitations. Maybe I'm reading too much into his post, but I think his assertion of 12 hz was just an example, not a rule.
 

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more posts deleted


if you have nothing to add, consider not posting here


Thanks
 

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Ok, now that I got that out of the way...


If 12 is an arbitrary value, when why not 15? 10? 6? Unless it's a simple factor of 'ease of construction', wherein a lower tune would require more volume/longer port in a LLT, and 12 Hz is a pretty convenient tune. I'll assume he's not really referring to horns, as 99% of the time aren't suited for all that much below 20Hz, with a couple notable exceptions.


But I ask, what is 'cost' associated with producing lower notes? With a ported sub, you trade volume, port length, and excursion. IB and sealed simply trade excursion. Coupled with room gain, it's relatively 'inexpensive' to get those low frequencies as compared to adding in additional shakers and amps for them. So the real question is, Why Not?
.


I'll admit, probably not much of value under the resonant frequency of your house, or around 7-8Hz. But down to that? Go for it!
 

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None of this matters to me, at least now, because my response in room starts rolling just under 25 Hz, and I'm at no risk of having significant output from my sub at 15 Hz or 12 Hz or whatever.


While I always liked what a sub could do for me in my car, I'm not convinced that the experience of bass frequencies in a pressurization/depressurization environment is the same as the experience of those frequencies in a space where they have room to breathe. Which is to say, to the extent people are seeking to take advantage of pressurization, they're shooting for something other than realistic recreation of the recording/theater/mixing stage experience.


I rather suspect that if you were standing close enough to a large explosion outdoors your clothing would indeed flap, and in the total absence of any room pressurization at all.


None of which is in any way instructive as to whether or when any individual might prefer a tactile transducer over a sub that goes way deep . . . so I'll shut up now.
 

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Quote:
Originally Posted by vasyachkin /forum/post/18232778


but what is the lowest such frequency that is relevant ? there are no resonances in the body below 20 hz.

You are wrong. There are certain body muscle resonances at 4-12Hz. I'll leave it to you to find out what exactly since you seem to be so well documented.
 

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Quote:
Originally Posted by Th3_uN1Qu3 /forum/post/18235599


You are wrong. There are certain body muscle resonances at 4-12Hz. I'll leave it to you to find out what exactly since you seem to be so well documented.

Besides, having no resonance doesn't mean objects can't be vibrated, just that it takes more power to do so.
 

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Down to some point, Low bass is not pointless, it is increasingly difficult, what appears to be a limit you perceive is in fact a limit to what your listening through and what is actually present deliberately on soundtracks.


Look up a copy of the equal loudness curves, notice that the minimum level just to be audible at all, or perceived as a fixed loudness rises steadily as the frequency falls.

Most charts end at 20Hz but in reality, the curves continue on more or less the same angles as a result of leakage or self cancellation in the form of ones Eustachian tubes.


Thus, the difficulty and physical size needed increases dramatically as the desired low frequency corner falls. For example, in homage to Hoffman and his unpleasant iron law', keeping the box size the same but lowering the low corner an octave, reduces the maximum possible efficiency by 9 dB and requires four times the displacement to produce he same SPL .

Now, to compensate for the slope in ones hearing -LF sensitivity, it requires much more displacement.

That same hearing slope means that against a silent background, you will hear the third harmonic of 20Hz tone much more easily than the 20Hz fundamental. Due to perceptual masking, higher bass frequencies can mask (make inaudible) lower ones.


There is a reality check you can perform if you wish how much low frequencies matter, obtain a sealed box subwoofer with a corner frequency at about 40-50Hz.

Place it in your car where the sealed box roll off will roughly compliment you car's room gain assuming it's not a convertible).

Sample some of your favorite move soundtracks in your car, maybe use a spectrum analyzer to see what your hearing.

In a tiny airspace like a car it is relatively easy to produce pneumatic feeling bass.

In a larger space like a living room, it takes much more displacement and a lower corner Frequency. In an even larger space like a full theater, there is little or no room gain, if there is, it is really low.

Best,

Tom Danley
 

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Quote:
Sample some of your favorite move soundtracks in your car, maybe use a spectrum analyzer to see what your hearing.

In a tiny airspace like a car it is relatively easy to produce pneumatic feeling bass.

In a larger space like a living room, it takes much more displacement and a lower corner Frequency. In an even larger space like a full theater, there is little or no room gain, if there is, it is really low.

Best,

Mr Danley, Very cool suggestion!!
 

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In my own case, I seem to be able to hear frequencies of around 14-15hz if the level is high enough and we are talking quite high indeed (Judging by DTS-10, and various other high powered bass devices). Below that I don't seem to be able to hear much of anything unless it is gargantuan loud. I once produced a 120db 12.5hz sine wave for a few seconds in my house and I don't think that I heard anything other than rattles and flapping of the structure along with the 2nd and 3rd harmonics. I could feel it loud and clear and there was no doubt that something was going on, but it feels more like a mechanical shaking or an air pressure change on your whole body than sounding like anything. Anybody that says that you wouldn't be able to tell the difference between the fundamental being missing and listening to just the harmonics is plain crazy.


I do wonder about how that same type of level would be experienced outdoors away from anything to rattle or shake, other than the dirt and the air. The ground is much harder to shake from 12ft away and perhaps this would leave you with only a weird sort of pressure feeling? I've never operated a system outdoors that had the sort of extension and power necessary to test that. In a car it's easy.
 

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Quote:
Originally Posted by Tom Danley /forum/post/18235924


Sample some of your favorite move soundtracks in your car, maybe use a spectrum analyzer to see what your hearing.

As I alluded to before much of the misconception about what's actually being heard is the fault of spectrum analysis. Guys look at the charts of what's present in their media, and they look at charts of what their systems are putting out, and if they see all sorts of content below 20 Hz and they perceive a lot of low end they put two and two together and assume that they're hearing 20 Hz and below. But in this case two and two equals three. You can only be sure what you're hearing is at 20 Hz and below when your spectrum analysis shows that there's nothing there above 20 Hz.


The same applies to playing a very low frequency test tone and, based on hearing something, assuming is it's that frequency. This is where doing an RTA is beneficial, as you'll see that, while that test frequency may be there (or not, if the speaker doesn't actually go that low) there's a lot of harmonic content, and that's what's actually being heard. As for what's being felt, that's another story entirely.


These conclusions are based on my experience measuring LF tones that are pure enough for harmonic content not to scotch the results. I can't hear a 20 Hz tone at 110dB, though my measuring gear can. Outdoors I can't feel it either, unless I'm within a few feet of the speaker, and then all I can feel is air movement. But indoors at even 95dB SPL I can feel the impact of 20 Hz and below just fine, it's all a matter of containing that energy in a small enough space.
 
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