Hello
I'm planning on building an infra-bass subwoofer based on these instructions (Build an Infrasonic Subwoofer) but I have doubts as to the effectiveness of their design... I was wondering if you could help me out, I'm new to the world of acoustics and speaker-building.
The main problem is this: their choice of subwoofer - the 21" PylePro - has a frequency response of 22hz to 4khz (according to their website).
As I understand it these numbers delineate the range of frequencies the driver is capable of producing. Am I wrong? ... Could I still generate 18hz at a significant amplitude enough for people to really feel it in their bodies with this speaker despite these specifications?
My plan, based on these instructions, is to house a 21in Pyle in a large (1.2 x 1.1 x 0.3m ish) enclosure and use a 1000 watt amp. My budget is around £500 - £600. Does this sound feasible?
If you have any advice at all, or can point me in the right direction I would be very grateful!
I'm planning on building an infra-bass subwoofer based on these instructions (Build an Infrasonic Subwoofer) but I have doubts as to the effectiveness of their design... I was wondering if you could help me out, I'm new to the world of acoustics and speaker-building.
The main problem is this: their choice of subwoofer - the 21" PylePro - has a frequency response of 22hz to 4khz (according to their website).
As I understand it these numbers delineate the range of frequencies the driver is capable of producing. Am I wrong? ... Could I still generate 18hz at a significant amplitude enough for people to really feel it in their bodies with this speaker despite these specifications?
My plan, based on these instructions, is to house a 21in Pyle in a large (1.2 x 1.1 x 0.3m ish) enclosure and use a 1000 watt amp. My budget is around £500 - £600. Does this sound feasible?
If you have any advice at all, or can point me in the right direction I would be very grateful!
Ya, that Pyle sub isn't going to do it. You need a lot of displacement to do what you want, depending on the SPL you want.
I have 6 x 12" subs and my room starts to give gain below about 25hz. I can get output down below 10hz no problem, but my output is maxed out around 100db at the LP. Maybe a little more if I had more power. Without the room help, I'd be even lower.
So, what is your SPL and low frequency target?
I have 6 x 12" subs and my room starts to give gain below about 25hz. I can get output down below 10hz no problem, but my output is maxed out around 100db at the LP. Maybe a little more if I had more power. Without the room help, I'd be even lower.
So, what is your SPL and low frequency target?
Hi,
Not really, its pretty hard to mess up a sealed box.
Its a 2x21" each with 9mm excursion so low bass is always doable with EQ.
Though one driver in the same box vented at 18Hz will do low bass better.
There is a misleading statement regarding box shape, not what it really
means, which is the box truncated to a cube is too small for two drivers.
No box stuffing is a major oversight.
Mass loading the cones is all wrong, doubling mass drops resonance by
root2 not half, and is a pretty much a meaningless throwaway comment,
as no consideration is given to any of the real effects of actually doing so.
The real issue is the choice of drivers, for the intended purpose.
rgds, sreten.
You don't necessarily need a ridiculous SPL in order to "feel it". To feel the earth move, yeah, that takes a big horn loaded PA. I was "feeling" 18 Hz sinewaves with a couple of 12's that had an 8 mm x-max in 10 cubic foot monkey coffins driven by about 20 miserable watts. As a matter of fact, it could be "felt" in the shower down the hall to a greater extent than the bedroom where the speakers were being tested. Get a more capable subwoofer and filling up a normal living room with the same sensation should be no problem. Will it be as loud a a Who concert? No. It may only be 90dB or so, but you will "feel it".
Thanks for your responses everyone, I realise I haven't been that clear about my intentions so I should probably just tell you what I want to achieve and let you advise me as to the best route.
Essentially I want to recreate the experience of engineer Vic Tandy as described in his paper Ghost in the Machine. To cut a long story short, Tandy has demonstrated a connection between infrasonic standing waves and seemingly 'supernatural' experiences.
If you haven't read any of this it's not very long and is absolutely fascinating. You can find it online at http://users.iafrica.com/s/sa/salbu/apollo/HumA2.html if you're interested.
In short: at the laboratory where he worked, people often experienced feelings of a 'presence' in the room, cold shivers, fear, anxiety. Tandy himself, whilst sitting halfway down the room at his desk, hallucinated a greyish figure to his left one evening. Being an engineer (and rationally minded) he dismissed the experience, thinking he was simply cracking up. The next day he was using the vice at his desk to repair his fencing foil (sword) and noticed it vibrating back and forth. This led him to suspect that infrasound was responsible, something he later proved with measuring equipment. He also noted the wobbling increased towards the centre of the room and decreased towards either end. Apparently and infrasound of 18.98 hz was generated by the extractor fan at one end of the room.
It turns out that the length of the room - 30ft - corresponded with the length of the 18.98 Hz in such a way that a standing wave was created: it was "just the right frequency to be completely reflected back by the walls at each end, so it was not going anywhere". The point of peak energy was the middle of the room - where he was sitting when he hallucinated the figure.
According to NASA technical report 19770013810 the resonant frequency of the human eyeball is around 18hz, perhaps causing a smearing of vision subsequently interpreted by the brain - in a state of fear/anxiety - as a figure. Whole body vibration can also hyperventilation. Infrasound has also been demonstrated to instil fear etc. in people in a couple of other tests. Vic Tandy has also demonstrated infrasound standing waves causing similar effects in other locations (http://www.richardwiseman.com/resources/Something-in-the-Cellar.pdf)
So, I want to make a 18.98hz standing wave for a sound installation.
In the 'Something in the Cellar' incident in a Coventry basement the 19hz frequency is only about 38db or something like that. Unfortunately he did not measure the amplitude of the wave in his lab. I have thought it'd be good to have the potential to go up to 100-130db for the sake of flexibility, I'm not sure though obviously. Sorry I can't be any more specific.
Any ideas how I might do this? I have a 30ft(ish) room. Just need dem standing waves!
Essentially I want to recreate the experience of engineer Vic Tandy as described in his paper Ghost in the Machine. To cut a long story short, Tandy has demonstrated a connection between infrasonic standing waves and seemingly 'supernatural' experiences.
If you haven't read any of this it's not very long and is absolutely fascinating. You can find it online at http://users.iafrica.com/s/sa/salbu/apollo/HumA2.html if you're interested.
In short: at the laboratory where he worked, people often experienced feelings of a 'presence' in the room, cold shivers, fear, anxiety. Tandy himself, whilst sitting halfway down the room at his desk, hallucinated a greyish figure to his left one evening. Being an engineer (and rationally minded) he dismissed the experience, thinking he was simply cracking up. The next day he was using the vice at his desk to repair his fencing foil (sword) and noticed it vibrating back and forth. This led him to suspect that infrasound was responsible, something he later proved with measuring equipment. He also noted the wobbling increased towards the centre of the room and decreased towards either end. Apparently and infrasound of 18.98 hz was generated by the extractor fan at one end of the room.
It turns out that the length of the room - 30ft - corresponded with the length of the 18.98 Hz in such a way that a standing wave was created: it was "just the right frequency to be completely reflected back by the walls at each end, so it was not going anywhere". The point of peak energy was the middle of the room - where he was sitting when he hallucinated the figure.
According to NASA technical report 19770013810 the resonant frequency of the human eyeball is around 18hz, perhaps causing a smearing of vision subsequently interpreted by the brain - in a state of fear/anxiety - as a figure. Whole body vibration can also hyperventilation. Infrasound has also been demonstrated to instil fear etc. in people in a couple of other tests. Vic Tandy has also demonstrated infrasound standing waves causing similar effects in other locations (http://www.richardwiseman.com/resources/Something-in-the-Cellar.pdf)
So, I want to make a 18.98hz standing wave for a sound installation.
In the 'Something in the Cellar' incident in a Coventry basement the 19hz frequency is only about 38db or something like that. Unfortunately he did not measure the amplitude of the wave in his lab. I have thought it'd be good to have the potential to go up to 100-130db for the sake of flexibility, I'm not sure though obviously. Sorry I can't be any more specific.
Any ideas how I might do this? I have a 30ft(ish) room. Just need dem standing waves!
Yevesy,
38 dB SPL at 19 Hz could be done easily by any decent 12" low FS speaker in a cabinet tuned (Fb) to 19 Hz.
A Pair of Eminence Lab 12 (22 Hz Fs) in a 5.13 cubic foot box with an Fb of 19.15 Hz can do 112 dB half space with 800 watts, though for extended periods (more than a minute or so) the pair of speakers only handle 400 watts of sine waves, so long term 109 dB.
In room, the level could be more, -or less, depending on the rooms modes and volume.
110 dB SPL at 19 Hz only sounds about as loud as 70 dB to your ears, but makes me feel queasy after a short period of time, 5 minutes is more than enough.
Assuming the dual Lab 12 design above was used, it would take around 12 cabinets driven with 4800 watts to produce 13 dB.
A fan driven approach for a 19 Hz specific frequency would give far more output per watt than a loudspeaker. A pipe (as in pipe organ) with a few horsepower fan (about 1500 watts) probably could achieve 140 dB at 19 Hz.
With a "trombone" slide on the pipe, you could vary the frequency a few Hz, everybody's resonant frequencies vary a few Hz.
Art
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If you want to have fun with low frequencies like that, build a sturdy box that you can fit inside and use a 15" driver or so. Or just start with a smaller driver to see what you need.
Measure the response and EQ to desired effect.
Some damping along the walls and you can get pretty good response with normal sized monitor speakers for fullrange use.
And I suggest a panic switch to cut out all sound. I know from experience that loud LF sounds can make you ill and it might even knock you out if loud enough.
It is also very easy to get high SPL that way so be careful. And the fact that you seal yourself in might also be dangerous.
Measure the response and EQ to desired effect.
Some damping along the walls and you can get pretty good response with normal sized monitor speakers for fullrange use.
And I suggest a panic switch to cut out all sound. I know from experience that loud LF sounds can make you ill and it might even knock you out if loud enough.
It is also very easy to get high SPL that way so be careful. And the fact that you seal yourself in might also be dangerous.
So let me get this straight, is it or is it not possible to get infrasound frequencies by putting subs in a box that is tuned low and EQed (though I'm not sure exactly what this EQing would require), even if their range starts above 20hz?
Can anyone recommend any subs that start in the infrasound range?
weltersys - your single freq pipe organ idea sounds promising! I wonder if it would be possible to used a curved/spiralling pipe (like many brass instruments) to save space? Otherwise I imagine it would have to be very long...
Can anyone recommend any subs that start in the infrasound range?
weltersys - your single freq pipe organ idea sounds promising! I wonder if it would be possible to used a curved/spiralling pipe (like many brass instruments) to save space? Otherwise I imagine it would have to be very long...
Sealed subs will play lower than their spec. Don't pay much attention to the spec.
Of course it can be done. The problem is many on this side of the fence don't do it. Try the hometheatershack forum. Also the mentality on the subwoofer forum is either sealed or horns. So if you are looking at reflex, you will not find many participants over here.
"Infrasound" in itself is a misnomer, we can hear down to a few Hz if loud enough. Reproducing very low frequency you need to decide how low and how loud you desire, the lower and louder, the more displacement needed.
If you want to go all the way down to a few Hz, sealed subs are generally the way to go.
Horn and ported cabinets can be far more efficient than sealed cabinets to a specific cut off frequency, then they drop at around 24 dB per octave, while sealed only drop around 12 dB per octave.
If you look at the DataBass site you can compare the low frequency of various systems, sealed, bass reflex, and tapped horns.
http://www.data-bass.com/home
Front loaded horns for frequencies as low as 19 Hz have been built, but they would not fit in your room.
A PVC organ pipe could be built in a small area using multiple 90 degree bends.
Although the fan driven pipe could be louder at a given frequency, being able to reproduce various tones and music is far more useful. Also, the pipe will have harmonics, they would be heard, rather than felt.
A simple box like the one below can be made with a low tuning, if you make the ports external,using PVC pipe, you can play with various tunings or seal the cabinet.
Art
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There's a 'Shadow of the Beast - Adventures In Closet-Sized Subwoofers' thread on another forum, with dual opposed 18' Re XXX being put into something like 400 cu ft in total IIRC - the different models predict anything from 110dB to 128dB at 10Hz, depending on alignment.
ULF SPL can knock you unconscious?
So it sounds like my initial suggestion of using a 21" Pyle subwoofer in a sealed enclosure might not have be too far from what I'm after...
I don't think I'll need to go below 10hz to be honest. My main target is to be able to make a 19hz standing wave, and I'm not worried about people being able to hear it. It would be great to have the flexibility of going lower but not essential. For volume up to 100db would be my target... Does the fact that the wave is a standing wave amplify or exaggerate it further, in that it is constantly reflecting back upon itself and is self-reinforcing?
So my plan of action/formula:
Get a big subwoofer, perhaps two, with as low freq response as possible. (not sure on the other specifications...)
+ Large sealed enclosure. As I understand it the cubic footage of the box determines its tuning; if I enter the details of my driver(s) into that winisd programme I will be able to find out what dimensions will 'tune' the speaker to 19hz or lower.
+ amplifier, 1000 watt. (This is another guess, made based on the amount used for the speakers in the instructable I posted previously.)
I've found a pair of refurbished 18in sub speakers online for £200 and the seller isn't too far away from me. Perhaps this is a good option?
http://i.ebayimg.com/t/celestion-b18-1000-18-1000w-pair-speakers-driver-reconed-/00/s/MTAyNFg3Njg=/z/3jYAAOxyJU1SMfoa/$T2eC16VHJHoFGlV-ekvzBSMfoZqu7Q~~60_12.JPG
Thank you all so much for your advice! And apologies once again for my ignorance.
I don't think I'll need to go below 10hz to be honest. My main target is to be able to make a 19hz standing wave, and I'm not worried about people being able to hear it. It would be great to have the flexibility of going lower but not essential. For volume up to 100db would be my target... Does the fact that the wave is a standing wave amplify or exaggerate it further, in that it is constantly reflecting back upon itself and is self-reinforcing?
So my plan of action/formula:
Get a big subwoofer, perhaps two, with as low freq response as possible. (not sure on the other specifications...)
+ Large sealed enclosure. As I understand it the cubic footage of the box determines its tuning; if I enter the details of my driver(s) into that winisd programme I will be able to find out what dimensions will 'tune' the speaker to 19hz or lower.
+ amplifier, 1000 watt. (This is another guess, made based on the amount used for the speakers in the instructable I posted previously.)
I've found a pair of refurbished 18in sub speakers online for £200 and the seller isn't too far away from me. Perhaps this is a good option?
http://i.ebayimg.com/t/celestion-b18-1000-18-1000w-pair-speakers-driver-reconed-/00/s/MTAyNFg3Njg=/z/3jYAAOxyJU1SMfoa/$T2eC16VHJHoFGlV-ekvzBSMfoZqu7Q~~60_12.JPG
Thank you all so much for your advice! And apologies once again for my ignorance.
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