Over on the tapped horn thread, Tom Danley mentioned something curious. Sounds like he's converting a CARGO SHIPPING CONTAINER into a infrasonic tapped horn.
Quite an elegant sub enclosure if you ask me. You can get those containers for peanuts, they're rigid, and they're ubiquitous. And you need a lot of displacement to create infrasonics, so it's a great solution.
Quite an elegant sub enclosure if you ask me. You can get those containers for peanuts, they're rigid, and they're ubiquitous. And you need a lot of displacement to create infrasonics, so it's a great solution.
idea from a very unrelated background
i was involved years ago with a company which made variable pitch propulsion systems for large oil tankers,a company called
Kamewa provided rapily reversible Water-jet movement by a constant motion but variable pitch blade system, perhaps some of their technology could come in handy at least as far as the technology of the "prop tilt" techlology is concerned. i realize it is water i'm talking about, but the technology can't be that different here. maybe some of the variable-vane technology from their design could be interpreted into the design. they have already done multi million dollars worth of design in this area, perhaps it could pay off in the air movement arena as well.
and in the "fan pulling pressure on both sides" idea, it seems that the most effective idea would be to have a fan pulling and pushing on both sides, and to have it pushing and pulling air on plenums directly agacent one another, and having a voice coil apparatus rapidly moving an air duct back and forth across the intake and exhaust of the fan as per the demonstration earlier.
just throwing my ideas in as an amateur audiofile and past ship propulsion experience, i thought it might help, though to be honest, i don't see how frequencies that low might benefit me, but i am ready to be knocked off this perch, so to speak.
some google searches on kamewa should generate sufficient concepts on the "variable vane technology" side of the argument.
even though a large part of my research was on the variable vane tech, i think that the fan using the "push pull" technology and the tilting plenum concept, with a voice coil attached at a 90 degree angle to the plenum would be the most effective considering the frequencies involved. relatively low noise, half the power used, and a closed loop, making the overall result more accurate, and possibly more efficient
p.s. any plenum design's efficiency and sound quality in this concept would be improved with a pressure buffer space on both sides of the wave. i.e. the fan pressurizing two halves of a chamber, as reserve pressure.
i was involved years ago with a company which made variable pitch propulsion systems for large oil tankers,a company called
Kamewa provided rapily reversible Water-jet movement by a constant motion but variable pitch blade system, perhaps some of their technology could come in handy at least as far as the technology of the "prop tilt" techlology is concerned. i realize it is water i'm talking about, but the technology can't be that different here. maybe some of the variable-vane technology from their design could be interpreted into the design. they have already done multi million dollars worth of design in this area, perhaps it could pay off in the air movement arena as well.
and in the "fan pulling pressure on both sides" idea, it seems that the most effective idea would be to have a fan pulling and pushing on both sides, and to have it pushing and pulling air on plenums directly agacent one another, and having a voice coil apparatus rapidly moving an air duct back and forth across the intake and exhaust of the fan as per the demonstration earlier.
just throwing my ideas in as an amateur audiofile and past ship propulsion experience, i thought it might help, though to be honest, i don't see how frequencies that low might benefit me, but i am ready to be knocked off this perch, so to speak.
some google searches on kamewa should generate sufficient concepts on the "variable vane technology" side of the argument.
even though a large part of my research was on the variable vane tech, i think that the fan using the "push pull" technology and the tilting plenum concept, with a voice coil attached at a 90 degree angle to the plenum would be the most effective considering the frequencies involved. relatively low noise, half the power used, and a closed loop, making the overall result more accurate, and possibly more efficient
p.s. any plenum design's efficiency and sound quality in this concept would be improved with a pressure buffer space on both sides of the wave. i.e. the fan pressurizing two halves of a chamber, as reserve pressure.
I just wanted to note something that posted well over a year ago on here. In post #13, phase_accurate posted a link to "project 48".
Anyway, in that link, Rod Elliott was saying something about pipe organs and this caught my attention. He said...
"The longest pipe on the organ is usually about 16Hz, but larger pipes still may be used. It was found necessary to stop one group of diapasons (capable of 8Hz) in the famous Sydney Town Hall organ because when they were used, the very low frequency caused building damage."
I'm not exactly sure what he really meant about this, but if he was referring to placing "stops" on the diapason, this will not make the pipe speak quieter or at a higher pitch. In fact, the "volume" of the pipe stays the same, and it also lowers the pitch of the pipe 1 octave.
IOW, stopping an 8' Diapason will make it speak as a 16' Diapason, likewise, stopping a 16' Diapason will make it speak at 32', and a 32' speak at a 64'.
And for an FYI, the Sydney Town Hall pipe organ has TWO 32' Double Open Diapasons, one wood and one metal, both of which are open (obviously by the name). Low C on both of these ranks speak at 16Hz.
There's also a 32' Contra Bourdon in the Sydney Town Hall pipe organ. Now low C in this rank is also 32' tall, but it is stopped, so it speaks as a 64', reaching down to 8Hz very effectively. This rank is still very much in use today as it always has been.
I'm not too certain about some damage happening to the Hall due to the bass of the pipe organ. If there was, it might have been an accoustic tile or something that fell, but I highly doubt anything serious.
And just to give you an idea of how large a 32' Contra Bourdon is...
Ok, now back to the regularly scheduled program.
Anyway, in that link, Rod Elliott was saying something about pipe organs and this caught my attention. He said...
"The longest pipe on the organ is usually about 16Hz, but larger pipes still may be used. It was found necessary to stop one group of diapasons (capable of 8Hz) in the famous Sydney Town Hall organ because when they were used, the very low frequency caused building damage."
I'm not exactly sure what he really meant about this, but if he was referring to placing "stops" on the diapason, this will not make the pipe speak quieter or at a higher pitch. In fact, the "volume" of the pipe stays the same, and it also lowers the pitch of the pipe 1 octave.
IOW, stopping an 8' Diapason will make it speak as a 16' Diapason, likewise, stopping a 16' Diapason will make it speak at 32', and a 32' speak at a 64'.
And for an FYI, the Sydney Town Hall pipe organ has TWO 32' Double Open Diapasons, one wood and one metal, both of which are open (obviously by the name). Low C on both of these ranks speak at 16Hz.
There's also a 32' Contra Bourdon in the Sydney Town Hall pipe organ. Now low C in this rank is also 32' tall, but it is stopped, so it speaks as a 64', reaching down to 8Hz very effectively. This rank is still very much in use today as it always has been.
I'm not too certain about some damage happening to the Hall due to the bass of the pipe organ. If there was, it might have been an accoustic tile or something that fell, but I highly doubt anything serious.
And just to give you an idea of how large a 32' Contra Bourdon is...
An externally hosted image should be here but it was not working when we last tested it.
Ok, now back to the regularly scheduled program.
Rotary subwoofers
There are non huge subwoofers that are called rotary subwoofers.
http://www.eminent-tech.com/RWbrochure.htm
Here is a link
There are non huge subwoofers that are called rotary subwoofers.
http://www.eminent-tech.com/RWbrochure.htm
Here is a link
A infinite baffle is the best way for frequencies lower than 30 Hz.
See realisations from http://ibsubwoofers, just for making your mind.
See realisations from http://ibsubwoofers, just for making your mind.
tvi said:
a few years ago my boss at a local electronics shop gave me 3 of the ribbon drivers sans boxes, two were nearly mint, one was taken apart, the good ones were alittle worn out but sounded so very good even without boxes..... sadly the two working ones were 'taken' off my hands when I lost a storage locker for non-payment... I still have the disected one in my dad's basement... does anyone have information that I could use to resurrect it and maybe build it a mate? I know this is wrong post for this but I have been searching high and low for info for these drivers
giant subs
Clairion and Kenwood both make a 32" driver but is it needed?
If you just want to reproduce 8hz You could build a transmission line enclosure for an 18" driver and that should achieve frequencies far too low for human hearing such as 8 hz!
On the other hand you might just want to have a bigass sub! does this have to be a "conventional" subwoofer? you can get a servo motor and build a woofer to be 99" if you want, check out the Adire audio Parthenon. I think that one was 44" I'll post a pic of it below
Clairion and Kenwood both make a 32" driver but is it needed?
If you just want to reproduce 8hz You could build a transmission line enclosure for an 18" driver and that should achieve frequencies far too low for human hearing such as 8 hz!
On the other hand you might just want to have a bigass sub! does this have to be a "conventional" subwoofer? you can get a servo motor and build a woofer to be 99" if you want, check out the Adire audio Parthenon. I think that one was 44" I'll post a pic of it below
Attachments
AndrewT said:
In my experiences hand building high end drivers for the last several years, when dealing with subwoofers, the voice coil it's self limits high frequency. subwoofer coils generally have more windings than a mid or even a full range driver, these extra windings act as an inductor and in return you can't get really high frequencies from a subwoofer, the cut is often around 6k for the average every day entry level woofer.Really high excursion woofers can be as low as 1k or lower.
big sub
Have you considered variable mass passive radiators?
You could run 1 driver and put it in an enclosure with several passive radiators to conserve amplifier power, as well as achieve extremely low frequencies at moderate SPL levels. Oh and the variable mass p.r.'s you can tune them yourself by adding weight to the rear of the cone, so it shouldn't be very difficult to get 8hz.
Here's the specs from audiopulse on their passives, and it looks like all but the 10" are capable of 8hz or lower!!!
10″ 12″ 15″ 18″
Qms Variable Variable Variable Variable
Mms 0.5 - 2 kg 0.5 - 2 kg 0.5 - 2 kg 0.5 - 2 kg
Fs 10 - 24 Hz 8 - 22 Hz 7 - 20 Hz 7 - 20 Hz
Sd 0.032 m² 0.052 m² 0.083 m² 0.110 m²
you can learn more about variable mass passive radiators at www.audiopulse.com
Have you considered variable mass passive radiators?
You could run 1 driver and put it in an enclosure with several passive radiators to conserve amplifier power, as well as achieve extremely low frequencies at moderate SPL levels. Oh and the variable mass p.r.'s you can tune them yourself by adding weight to the rear of the cone, so it shouldn't be very difficult to get 8hz.
Here's the specs from audiopulse on their passives, and it looks like all but the 10" are capable of 8hz or lower!!!
10″ 12″ 15″ 18″
Qms Variable Variable Variable Variable
Mms 0.5 - 2 kg 0.5 - 2 kg 0.5 - 2 kg 0.5 - 2 kg
Fs 10 - 24 Hz 8 - 22 Hz 7 - 20 Hz 7 - 20 Hz
Sd 0.032 m² 0.052 m² 0.083 m² 0.110 m²
you can learn more about variable mass passive radiators at www.audiopulse.com
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