and yes, GM, I will need to make sure that the building is up to it! I am not expecting to use horrendous SPL, just wanting to get the effect of felt waves rather than audible ones, for a sort of shock-wave effect with audible harmonics above it.
excuse me if i sound ignorant of all these things - i am wading through all the jargon, and i haven't even got close to working out the design beginning!
cheers,
sean.
excuse me if i sound ignorant of all these things - i am wading through all the jargon, and i haven't even got close to working out the design beginning!
cheers,
sean.
Hello orange,
I dont think that it's gonna be easy building a very low frequency horn that produces usable spl around 20hz and lower, I imagine that the horn would be as big or bigger than a room. really impractical.
If you really wanna have loud very low freq. I think the easiest way is to use sealed box, because it doesnt unload the driver at the very lowest freq. and it is also smaller than comparable vented box. You can start with one high quality 18" or two 12" subs with at least 500watts of power, then you can add more and more untill you're satisfied.
I think 14hz low enough. No need to go 10 hz, cause I doubt that you have a CD or movie with recorded sound that could go down to 10hz, but 14hz is more likely.
I dont think that it's gonna be easy building a very low frequency horn that produces usable spl around 20hz and lower, I imagine that the horn would be as big or bigger than a room. really impractical.
If you really wanna have loud very low freq. I think the easiest way is to use sealed box, because it doesnt unload the driver at the very lowest freq. and it is also smaller than comparable vented box. You can start with one high quality 18" or two 12" subs with at least 500watts of power, then you can add more and more untill you're satisfied.
I think 14hz low enough. No need to go 10 hz, cause I doubt that you have a CD or movie with recorded sound that could go down to 10hz, but 14hz is more likely.
It might be more sensible to rent some pro sound gear, like a ServoDrive Contrabass or two or four.
Or, inquire with speaker or car audio manufacturers or distributors; see if you can finagle a loan of some gear by convincing them that the publicity would be beneficial.
Or, inquire with speaker or car audio manufacturers or distributors; see if you can finagle a loan of some gear by convincing them that the publicity would be beneficial.
hi I am the artist too.
Understand Your special needs...
Maybe You can consider the dipole sub,
and proper active crossover before the amp?
design could bee 2x15in and maybe 4x12in?
The boxes would not be big to much I suppose...
and drivers will be well suited and protected inside
so when You move from gallery You will avoiding damages.
try to inform about this more
Understand Your special needs...
Maybe You can consider the dipole sub,
and proper active crossover before the amp?
design could bee 2x15in and maybe 4x12in?
The boxes would not be big to much I suppose...
and drivers will be well suited and protected inside
so when You move from gallery You will avoiding damages.
try to inform about this more
Oh, just to mention
friend of mine was built, for the one exibition,
a ultra low fr gun. Something more like the big organ pipe
with a several meters long and wry wide.
driven by a air flow from,
the preseted big fun speed...
it was beyond ears...
but he has to test for the low fr db licens
because the something of about 7.5Hz is the heart resonant fr...
and could damage the hert
friend of mine was built, for the one exibition,
a ultra low fr gun. Something more like the big organ pipe
with a several meters long and wry wide.
driven by a air flow from,
the preseted big fun speed...
it was beyond ears...
but he has to test for the low fr db licens
because the something of about 7.5Hz is the heart resonant fr...
and could damage the hert
Hope I don't get crucified for this...
I recommend a 4th order BP. Why? Because your greatest challenge is overcoming the harmonics. With a 10hz note, the 2nd, 3rd, 4th etc harmonics can easily be perceived as louder than the fundamental. You need the harmonics to be very very low, and a 4th order BP attenuates the harmonics via an acoustic filter.
How large is your studio, and what is your floor made out of? Room gain is an important factor at the frequencies you are considering. If you are on the ground with a concrete floor, you can count on at least one boundary reflection to reinforce the bass.
Dan
I recommend a 4th order BP. Why? Because your greatest challenge is overcoming the harmonics. With a 10hz note, the 2nd, 3rd, 4th etc harmonics can easily be perceived as louder than the fundamental. You need the harmonics to be very very low, and a 4th order BP attenuates the harmonics via an acoustic filter.
How large is your studio, and what is your floor made out of? Room gain is an important factor at the frequencies you are considering. If you are on the ground with a concrete floor, you can count on at least one boundary reflection to reinforce the bass.
Dan
hello all and thankyou for your generous responses!
I have been trowelling the net (when I should be actually MAKING stuff) and it is becoming obvious to me that horn loading is very arcane territory with differing opinions and possibilities. That I don't mind, but I am no pro at speaker design. I need to work out my basic priorities. So here they are.
1. deep soundwaves - not necessarily down below 20Hz, but strong and readily tactile in the air - able to move a volume of air easily in a large-ish room.
2. able to be powered by a 300W Perreaux amp (6000B)
3. a design which is fairly simple, or a complex one that I can adapt without too much esoteric loudspeaker research (I don't mind complex construction at all, but the design is a little beyond me at the moment...)
One other thing which is very important - I can attenuate the sound - which I edit myself on Soundtrack Pro - to suit the room, and also I can equalize the output to make a nice flat response in the room I am using it in (and then burn a new copy of the audio, and, voile!)
This is not a hi-fi system - it is a way to produce very low frequencies - I am not so concerned about the fidelity - just don't want it to be ultra muddy or full of clipping....
This brings me to the point that I could bass-boost significantly using equalising of the audio I am making, and move the air in the room if my driver and amplifier were up to the task. So, would it not be best for me to go the easy route and build a simple sealed enclosure and boost an octave below? Say using these Dayton 15" (http://www.speakercity.com/Merchant...roduct_Code=RSS390HF4&Category_Code=DaytonRef) to make a sealed 0.7Qtc enclosure of around 6cuft with resonance of around 32Hz. I could give it boost down to the 20Hz range without fear of driver over-excursion due to the small enclosure, just having to watch the power levels....
Does this make sense? Easy, simple, but with quality components and solid construction?
Thanks again to anyone who has followed my muddly path thus far - I am only now realising my priorities and what it is I actually want....
Cheers,
Sean.
I have been trowelling the net (when I should be actually MAKING stuff) and it is becoming obvious to me that horn loading is very arcane territory with differing opinions and possibilities. That I don't mind, but I am no pro at speaker design. I need to work out my basic priorities. So here they are.
1. deep soundwaves - not necessarily down below 20Hz, but strong and readily tactile in the air - able to move a volume of air easily in a large-ish room.
2. able to be powered by a 300W Perreaux amp (6000B)
3. a design which is fairly simple, or a complex one that I can adapt without too much esoteric loudspeaker research (I don't mind complex construction at all, but the design is a little beyond me at the moment...)
One other thing which is very important - I can attenuate the sound - which I edit myself on Soundtrack Pro - to suit the room, and also I can equalize the output to make a nice flat response in the room I am using it in (and then burn a new copy of the audio, and, voile!)
This is not a hi-fi system - it is a way to produce very low frequencies - I am not so concerned about the fidelity - just don't want it to be ultra muddy or full of clipping....
This brings me to the point that I could bass-boost significantly using equalising of the audio I am making, and move the air in the room if my driver and amplifier were up to the task. So, would it not be best for me to go the easy route and build a simple sealed enclosure and boost an octave below? Say using these Dayton 15" (http://www.speakercity.com/Merchant...roduct_Code=RSS390HF4&Category_Code=DaytonRef) to make a sealed 0.7Qtc enclosure of around 6cuft with resonance of around 32Hz. I could give it boost down to the 20Hz range without fear of driver over-excursion due to the small enclosure, just having to watch the power levels....
Does this make sense? Easy, simple, but with quality components and solid construction?
Thanks again to anyone who has followed my muddly path thus far - I am only now realising my priorities and what it is I actually want....
Cheers,
Sean.
sounds scary zoran - sounds fabulous too!
i just need sense of real presence when two objects are colliding on a large projection - they collide very slowly - slowed down over 30 times, so it is very soft visually, and the accompanying audio needs to be up to scratch....
but as said, i am only now starting to realise what it is I really want! still trowelling the net....
thanks for the post! if there is any info out on your friend's infrasonic cannon, do send me details!
sean.
i just need sense of real presence when two objects are colliding on a large projection - they collide very slowly - slowed down over 30 times, so it is very soft visually, and the accompanying audio needs to be up to scratch....
but as said, i am only now starting to realise what it is I really want! still trowelling the net....
thanks for the post! if there is any info out on your friend's infrasonic cannon, do send me details!
sean.
the program is calles hornresp, its free, just google it. the thread that expleains everything about them is tight next to this one, the Collaborative Tapped horn project thread.
If much output for little money is a concern, then using a dipole is probably the worst choice one can make, followed closely by closed boxes.
BUT, i would go with what GM said. He is the one in this thread who knows the most and i would take his advice as the best possible for your situation.
If much output for little money is a concern, then using a dipole is probably the worst choice one can make, followed closely by closed boxes.
BUT, i would go with what GM said. He is the one in this thread who knows the most and i would take his advice as the best possible for your situation.
Just a thought, is that Perreaux amp mono, stereo or bridged mono?? It will make a difference to the load you can drive
owdi said:
Hmm, seems to me this was already suggested.......... 😉 Anyway, its harmonic suppression capability will be for naught if you don't deal with the out of BW harmonics that can't be digitally EQ'd out of the TL sized vent such a low tuned alignment will require and why I suggested dual PRs.
Since tapped horns are an interesting variant, then as Tom Danley has shown with his DTS-20, a properly designed one using a driver optimized for the BW will have more output/watt plus its out of BW harmonics can be digitally EQ'd out, but will be considerably larger.
Another option in this BW would be a folded up acoustic wave cannon, though its bulk will be greater than the PR vented BP for what I'm guessing will be about the same output/watt.
Then there's the traditional TQWT which will give you more high SQ BW to work with at the expense of losing some of the BP's higher acoustic efficiency: http://www.mach5audio.com/download/bassboy.pdf
GM
There is another method I am aware of but of which i have no personal experience.
Check out Rod Elliots sound pages for the ELF design, drivers working below resonance in a sealed box.
http://sound.westhost.com/index.html
Athough he does warn that power requirements and X-max requirements are quite high, perhaps a combination of both types of woofers would do the trick, as the infra woofers are used below resonance the enclosures are supposed to be fairly small.
Also check-out Bag End who use this technique
http://www.bagend.com/products.htm
Check out Rod Elliots sound pages for the ELF design, drivers working below resonance in a sealed box.
http://sound.westhost.com/index.html
Athough he does warn that power requirements and X-max requirements are quite high, perhaps a combination of both types of woofers would do the trick, as the infra woofers are used below resonance the enclosures are supposed to be fairly small.
Also check-out Bag End who use this technique
http://www.bagend.com/products.htm
GM,
Thanks for the link to the transmission line - he seems to be covering the same sort of territory. The transmission line enclosure folded is an ideal format for me - on its side at the rear of the gallery. Size is not really a big issue, but this would be perfect.
It seems that the transmission lines are easier to design than the horns, but I need to do more internet scouring....
I followed DrewP's thread about a bass cannon with a Vifa driver - it would sound awful in a hifi setup but might be perfect for what I want.... Does anyone know of any other articles that have gone into further detail?
I will follow up on the transmission line, acoustic wave cannon and maybe look at the passive radiators again (it seems that horn or transmission line would be better than these in every respect other than size though - and having to buy the "dead" radiators is a little strange....)
Thanks heaps for the post!
Sean.
Thanks for the link to the transmission line - he seems to be covering the same sort of territory. The transmission line enclosure folded is an ideal format for me - on its side at the rear of the gallery. Size is not really a big issue, but this would be perfect.
It seems that the transmission lines are easier to design than the horns, but I need to do more internet scouring....
I followed DrewP's thread about a bass cannon with a Vifa driver - it would sound awful in a hifi setup but might be perfect for what I want.... Does anyone know of any other articles that have gone into further detail?
I will follow up on the transmission line, acoustic wave cannon and maybe look at the passive radiators again (it seems that horn or transmission line would be better than these in every respect other than size though - and having to buy the "dead" radiators is a little strange....)
Thanks heaps for the post!
Sean.
My short answer is - listen to GM and make a badass bandpass. He knows what he is talking about. I have a long answer too but it takes awhile.
The long answer - is more complicated. First thing you need to do is decide what you NEED. So far, you have mentioned 10 - 30 hz, 10 - 40 hz, 10 - 50 hz, not necesarilly down below 20 hz, etc. My advice is to beg borrow or steal your way into an audition of some capable local gear to get a real life feel for the tones you actually want. It sounds like you are striving for the tactile sensation of being gripped by an unseen force, accompanied by some moderate level audible very low bass sounds. At 50 hz, the sensation will be almost entirely audible, and at 10 hz the sensation will be almost entirely felt rather than heard. You need to find where you need to be in that spectrum and then design your system to be optimally efficient in that band. I would speculate that the best way to maximize this tactile sensation would be to use pure sine waves, as opposed to any other waveshape, so you can feel the air pulsing.
Now assuming that you really want this system to play as low as 10 hz the next thing you really absolutely need to consider is human exposure. I think we can assume that it will not be loud enough to cause hearing damage, but even at very low levels, prolonged exposure can make people very sick. This is a very common problem in ventilation systems in very large buildings. Workers or inhabitants can suffer a great deal and never even know why since the sound is so low in frequency and amplitude that it is impossible to localize or even hear. Symtoms include (but not limited to) sense of anxiety, fear, depression. A 10 minute presentation will probably not bother anyone at all, but if there are people working in the gallery (yourself included) that will be exposed to this 8 hours a day, over and over for months, this could be an unhealthy situation, even at very low volume levels. At moderate to high levels, there may even be legal implications, as someone has already mentioned.
The next thing that really needs to be considered is the room. The size and shape and construction materials are very important factors. A 10 hz subwoofer will sound very different in a very large drywall room than it would sound in a very small concrete room. Additionally, the sound level and frequency response will be very uneven throughout the room unless it is extensively treated for sound. If you cannot precisely locate the subwoofer and presentation area where they sound the best, you may end up with less than perfect positioning for both. This requires trial and error, moving the sub, and yourself around the room to find the area of best response. If the sub or the presentation area or both are in deep null areas, no amount of power or eq will provide acceptable performance. You seem to be under the impression that the frequency response can be fixed with digital signal processing, but that is not entirely true. DSP can make the response flat in a certain location (the mic location) but since response is so dramatically different at different points around the room, fixing the response at one location can make it many times worse in another location. Anyway, the room size and construction will mostly determine how much subwoofer you need, based on your frequency response and spl goals. And improper placement can kill a good design. Also, don't forget that the bass will always be strongest along the walls - which incidentally is usually where the pictures are hung in an art gallery. Too much bass and the pictures (and everything else not tied down) might rattle right off the walls.
And finally it's time to consider the subwoofer itself. All designs are a compromise. Size vs bandwidth vs spl, and on and on. All the box designs have their pros and cons but the bandpass is the only one which provides a mechanical means of severly choking the response to a limited band of frequencies. At 10 hz, passive radiators really will be required, as per GM's orders, but they will actually save a great deal of space, so that alone is worth consideration. It really is worth it to choke off the high end "noise" if the tactile sensation in the air is the ultimate goal. If you don't do everything you can to mute the harmonics, the box noise and the driver noise, they will easily overpower the performance and the bass will be deafeningly loud and inarticulate by the time it's physically tangible. FYI I am the guy that wrote that tl .pdf that GM linked to. I love that box (although 12 hz tuning is a bit low, and I actually prefer it at a 15 hz tuning) but there's a reason GM listed tqwt as a 3rd option. As he mentions, it is a high sq, wide bandwidth (+/- 2 db from 12 hz to past 1000 hz when properly stuffed) sub, and if you don't need that much bandwidth you can get better low end performance from a smaller package from a bandpass with PR and a driver designed for very small boxes.
Any way you do it, it's not easy to make 10 hz with low distortion. Horns are too big, any resonant type enclosure with a port will need a massive vent length which introduces quarter wave harmonics, small sealed boxes with massive eq will work but you need a huge stack of them to get any reasonable output, dipole output suffers severely at low frequency, and infinite baffle requires some freedom to alter the room.
Good luck.
If you are successful in creating a low distortion, very low frequency tactile pressurization in your target area, the effect will surely be stunning. In addition to the negative side effects of very low frequency bombardment, with a bit of positive persuation there are many positive side effects which can be induced. Feelings like euphoria, otherworldly presence, reverence, energy, etc. We've been using low frequency tones to induce emotion for centuries now, and there's a good reason all the old churches have the biggest, lowest pipe organ they can afford. Low frequencies can create a powerful emotional response.
The long answer - is more complicated. First thing you need to do is decide what you NEED. So far, you have mentioned 10 - 30 hz, 10 - 40 hz, 10 - 50 hz, not necesarilly down below 20 hz, etc. My advice is to beg borrow or steal your way into an audition of some capable local gear to get a real life feel for the tones you actually want. It sounds like you are striving for the tactile sensation of being gripped by an unseen force, accompanied by some moderate level audible very low bass sounds. At 50 hz, the sensation will be almost entirely audible, and at 10 hz the sensation will be almost entirely felt rather than heard. You need to find where you need to be in that spectrum and then design your system to be optimally efficient in that band. I would speculate that the best way to maximize this tactile sensation would be to use pure sine waves, as opposed to any other waveshape, so you can feel the air pulsing.
Now assuming that you really want this system to play as low as 10 hz the next thing you really absolutely need to consider is human exposure. I think we can assume that it will not be loud enough to cause hearing damage, but even at very low levels, prolonged exposure can make people very sick. This is a very common problem in ventilation systems in very large buildings. Workers or inhabitants can suffer a great deal and never even know why since the sound is so low in frequency and amplitude that it is impossible to localize or even hear. Symtoms include (but not limited to) sense of anxiety, fear, depression. A 10 minute presentation will probably not bother anyone at all, but if there are people working in the gallery (yourself included) that will be exposed to this 8 hours a day, over and over for months, this could be an unhealthy situation, even at very low volume levels. At moderate to high levels, there may even be legal implications, as someone has already mentioned.
The next thing that really needs to be considered is the room. The size and shape and construction materials are very important factors. A 10 hz subwoofer will sound very different in a very large drywall room than it would sound in a very small concrete room. Additionally, the sound level and frequency response will be very uneven throughout the room unless it is extensively treated for sound. If you cannot precisely locate the subwoofer and presentation area where they sound the best, you may end up with less than perfect positioning for both. This requires trial and error, moving the sub, and yourself around the room to find the area of best response. If the sub or the presentation area or both are in deep null areas, no amount of power or eq will provide acceptable performance. You seem to be under the impression that the frequency response can be fixed with digital signal processing, but that is not entirely true. DSP can make the response flat in a certain location (the mic location) but since response is so dramatically different at different points around the room, fixing the response at one location can make it many times worse in another location. Anyway, the room size and construction will mostly determine how much subwoofer you need, based on your frequency response and spl goals. And improper placement can kill a good design. Also, don't forget that the bass will always be strongest along the walls - which incidentally is usually where the pictures are hung in an art gallery. Too much bass and the pictures (and everything else not tied down) might rattle right off the walls.
And finally it's time to consider the subwoofer itself. All designs are a compromise. Size vs bandwidth vs spl, and on and on. All the box designs have their pros and cons but the bandpass is the only one which provides a mechanical means of severly choking the response to a limited band of frequencies. At 10 hz, passive radiators really will be required, as per GM's orders, but they will actually save a great deal of space, so that alone is worth consideration. It really is worth it to choke off the high end "noise" if the tactile sensation in the air is the ultimate goal. If you don't do everything you can to mute the harmonics, the box noise and the driver noise, they will easily overpower the performance and the bass will be deafeningly loud and inarticulate by the time it's physically tangible. FYI I am the guy that wrote that tl .pdf that GM linked to. I love that box (although 12 hz tuning is a bit low, and I actually prefer it at a 15 hz tuning) but there's a reason GM listed tqwt as a 3rd option. As he mentions, it is a high sq, wide bandwidth (+/- 2 db from 12 hz to past 1000 hz when properly stuffed) sub, and if you don't need that much bandwidth you can get better low end performance from a smaller package from a bandpass with PR and a driver designed for very small boxes.
Any way you do it, it's not easy to make 10 hz with low distortion. Horns are too big, any resonant type enclosure with a port will need a massive vent length which introduces quarter wave harmonics, small sealed boxes with massive eq will work but you need a huge stack of them to get any reasonable output, dipole output suffers severely at low frequency, and infinite baffle requires some freedom to alter the room.
Good luck.
If you are successful in creating a low distortion, very low frequency tactile pressurization in your target area, the effect will surely be stunning. In addition to the negative side effects of very low frequency bombardment, with a bit of positive persuation there are many positive side effects which can be induced. Feelings like euphoria, otherworldly presence, reverence, energy, etc. We've been using low frequency tones to induce emotion for centuries now, and there's a good reason all the old churches have the biggest, lowest pipe organ they can afford. Low frequencies can create a powerful emotional response.
just a guy, thankyou for an amazing reply.
yes - these are all things that are important for me to work out, as you say - i have no real idea of what i need. this is definitely step number one.
i have been getting carried away with the idea of putting this thing together - when i was young (15 - 17) i used to work in a small hifi shop part-time, and i got a taste for audio, which i have never really followed though. i can still remember my boss hooking up a pair of wee proacs to the very same model perraux monster i now have, and being completely stunned - insane, but compelling sound out of such small boxes.... punchy accurate transients - oh my god....
but for this project, which is a two-year project, i will calm down and get more of a practical feel for what i need. it seems that you have narrowed down the reasons why others are making decisions about enclosure type, and for me this is very valuable - i like to know why. now i understand the need for passive radiators i will research more into their design.
thankyou for an excellently informative post, and i look forward to the journey of realising this infrasonic art accompaniment (maybe it will lead me back to proper audio as a sideline?!)
appreciated,
sean.
yes - these are all things that are important for me to work out, as you say - i have no real idea of what i need. this is definitely step number one.
i have been getting carried away with the idea of putting this thing together - when i was young (15 - 17) i used to work in a small hifi shop part-time, and i got a taste for audio, which i have never really followed though. i can still remember my boss hooking up a pair of wee proacs to the very same model perraux monster i now have, and being completely stunned - insane, but compelling sound out of such small boxes.... punchy accurate transients - oh my god....
but for this project, which is a two-year project, i will calm down and get more of a practical feel for what i need. it seems that you have narrowed down the reasons why others are making decisions about enclosure type, and for me this is very valuable - i like to know why. now i understand the need for passive radiators i will research more into their design.
thankyou for an excellently informative post, and i look forward to the journey of realising this infrasonic art accompaniment (maybe it will lead me back to proper audio as a sideline?!)
appreciated,
sean.
Hi Sean,
I don't come out of lurk mode here often, but I had a few things to procrastinate tonight. 🙄
In the past 6 months I've designed and installed a few subwoofers similar to what you are describing. GM & just a guy are steering your correctly with the suggestion of a bandpass. I would recommend a 6th order bandpass rather than 4th order, with the caveat that there tends to be more surprises in reality vs. the model if you have not used the driver before.
4 x 15" or 4 x 12" or 2x 18" in 1000L gross internal volume with the 1000W of power you have available (500W x 2 @ 4 Ohms) should be capable of 110-120dB @ 1m in the 10-100Hz range. I prefer to use a PR for the front chamber, but there are rather few suitable PRs readily available. Ports can work just as well, but be sure to not under-size the front chamber porting. The dozen variations I have prototyped or installed have been extremely clean in subjective operation, which I believe would be desireable in this application.
I would echo the recommendation to experiment on a smaller scale first. A DIY sealed subwoofer used in an automobile would be a simple way to at least get an idea of the effects of the signals. A very small, rigid room like a bathroom or closet might also work as a proof of concept and for experimentation. The important part is that low frequency operation to 10Hz vs. 16Hz is a huge difference so far as efficiency and stress on the drivers. Know that below 16Hz, we no longer identify "tone" but rather identify the feeling of the pressure modulation and its effects on us and the objects around us. Depending on the space and the intent, you might not have much need/desire for output below 15Hz, which could easily allow you a smaller package, or much greater output.
Sounds like an interesting project.
I don't come out of lurk mode here often, but I had a few things to procrastinate tonight. 🙄
In the past 6 months I've designed and installed a few subwoofers similar to what you are describing. GM & just a guy are steering your correctly with the suggestion of a bandpass. I would recommend a 6th order bandpass rather than 4th order, with the caveat that there tends to be more surprises in reality vs. the model if you have not used the driver before.
4 x 15" or 4 x 12" or 2x 18" in 1000L gross internal volume with the 1000W of power you have available (500W x 2 @ 4 Ohms) should be capable of 110-120dB @ 1m in the 10-100Hz range. I prefer to use a PR for the front chamber, but there are rather few suitable PRs readily available. Ports can work just as well, but be sure to not under-size the front chamber porting. The dozen variations I have prototyped or installed have been extremely clean in subjective operation, which I believe would be desireable in this application.
I would echo the recommendation to experiment on a smaller scale first. A DIY sealed subwoofer used in an automobile would be a simple way to at least get an idea of the effects of the signals. A very small, rigid room like a bathroom or closet might also work as a proof of concept and for experimentation. The important part is that low frequency operation to 10Hz vs. 16Hz is a huge difference so far as efficiency and stress on the drivers. Know that below 16Hz, we no longer identify "tone" but rather identify the feeling of the pressure modulation and its effects on us and the objects around us. Depending on the space and the intent, you might not have much need/desire for output below 15Hz, which could easily allow you a smaller package, or much greater output.
Sounds like an interesting project.
A few of these might do the trick... although I don't believe they are readily available quite yet...
MONSTER PR-18"
Sd: 1120 cm^2
Mmd: 210g
Qms: 6.3
Vap: 1106L
Cms: 0.63mm/N
Fp: 13.8Hz
Xsus: 43mm
from here http://www.audiocircle.com/circles/index.php?topic=53594.0 (DIYCABLE)
just a guy said:
Good Catch. I know Kevin and knew of the PRs but hadn't taken notice that they start life with only 210g of Mms. This can work in common volumes you will encounter in 6th order BP designs. The Maelstrom 18" is also well suited to this design. PRs being used for the low frequency tuning are even better, just more expensive and trickier to fit if box size isn't large in dimension.
PRs give the DIYer the advantage of easily adjusting any variations in real response and actual tuning frequency. A single Maelstrom would be a good starting point that would fit easily in a 500-600L internal design with output to near 10Hz. Power each VC of the woofer with one channel of the amp, and you're well within safe operating limits.
Thanks Mark and Justaguy,
I will send an email to diycable and see if they will ship their monster over (or there may be a local dealer here in Australia - likely slow and expensive....) This sounds like a good solution.
So in terms of design, I will start working with the design programs and have a fiddle, but are you suggesting a split interior volume with the driver inside and passive radiators mounted to room from each volume? Or just more conventional with the woofer and the two passive radiators all mounted to room? Sorry for the dumb question - I saw the 6th order bandpass enclosure designs and wasn't sure if you meant to use passive radiators instead of ports in that style of design..... I will start working out numbers and getting my head around it....
Your help is appreciated!
You are probably right about the 10Hz issue - no doubt 16Hz will be enough of a shock to the system and supply ample awe and effect alongside the video....
I need to get started and wading my way around this all in reality - this sounds like a good place to begin, with hardware that will allow me to find a solution (if not at first, then soon after!)
Again, much appreciated!
Sean.
I will send an email to diycable and see if they will ship their monster over (or there may be a local dealer here in Australia - likely slow and expensive....) This sounds like a good solution.
So in terms of design, I will start working with the design programs and have a fiddle, but are you suggesting a split interior volume with the driver inside and passive radiators mounted to room from each volume? Or just more conventional with the woofer and the two passive radiators all mounted to room? Sorry for the dumb question - I saw the 6th order bandpass enclosure designs and wasn't sure if you meant to use passive radiators instead of ports in that style of design..... I will start working out numbers and getting my head around it....
Your help is appreciated!
You are probably right about the 10Hz issue - no doubt 16Hz will be enough of a shock to the system and supply ample awe and effect alongside the video....
I need to get started and wading my way around this all in reality - this sounds like a good place to begin, with hardware that will allow me to find a solution (if not at first, then soon after!)
Again, much appreciated!
Sean.
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