Help needed for Sub-sonic subwoofer design.... - diyAudio
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Old 18th April 2008, 11:28 AM   #1
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Default Help needed for Sub-sonic subwoofer design....

Hello,

I am a new poster, and am interested in building a subwoofer that outputs sub-sonic frequencies in the range of 10 - 30 HZ for an audio-visual display that I am currently working on (this is "art" and consists of high speed video work and slowed audio recording of crashing objects....)

You must excuse me, and correct me, (and suggest please!!!) but these are my initial naive thoughts -

I am thinking of an extra-large low-tuned vented system or something else that will give me a really-low-frequency output.

In terms of drivers I am looking at two - the dayton reference 15" woofer - Fs 18Hz, Qes0.49, 500W RMS -
http://www.speakercity.com/Merchant2...Code=DaytonRef

Or, alternatively the horrendously expensive Mccauley 6174 18" woofer - Fs 20Hz, Qes 0.38, 800W RMS -
http://mccauleysound.com/component_overview.cfm?ID=126

I have quoted the power handling as I think this will be essential in getting the subwoofer to create this sub-sonic air movements....

I will be running the subwoofer off a big old 300W Perreaux poweramp and the sound will be only present in the 10 - 50Hz range, so higher frequency response is unimportant.

So is there anyone out there who has any suggestions or starting points for the design of ultra-low frequency enclosures? Size is not a factor as long as it is under a cubic metre or so. (Heaviness becomes an issue I am thinking....)

Any suggestions, links, help, etc. would be greatly appreciated.

In Thanks,
Sean.
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Old 18th April 2008, 01:25 PM   #2
Thawach is offline Thawach  Thailand
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Oh... guy i am a good English language. now i don't know that what you will use it for.... home or not?




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my english works well when i'm not understand. LOL
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Old 18th April 2008, 01:44 PM   #3
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your english is great! better than my speaker-design-skills!!!

this sub will be used in a gallery space (art gallery).
i realise that there will be lots of issues with the size of the gallery, but I want to get a start on researching this thing and finding possibilities.

so a big room, using lots of power, a big enclosure, with a big driver, and only needing frequencies in the range of 10 - 40Hz or therabouts....

i was looking at the sonotube by steve callas mentioned here in the forum - could be a starting point....

thanks for your reply,
sean.
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Old 18th April 2008, 02:19 PM   #4
MaVo is offline MaVo  Germany
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A word on the difficulty: Reaching 10hz with usable output means using LOTS of drivers. Your hearing threshold is about 95-100db for a 10hz wave. You need clean output without distortion at this frequency, because as the frequency rises, the hearing threshhold gets much lower, meaning that the perceived distortion masks the fundamental easily.

How to do it? : Either Lots of drivers or big horns or exotic devices. Disregarding the kind of implementation, you will probably end with a device that will be to big or too heavy or unsusable because of distortion levels. I would go the horn way, as you can substitute LOTS of drivers with a smart design and wood. I'll add a simulation of a stack of eight tapped horns, that will do 10-40hz with lots of output, but each unit is about 500liters, making the stack 4m big. You could use this as a staring point to develop a compromised system.
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Old 18th April 2008, 02:47 PM   #5
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Orangealpaca,

Do a search for "subsonic speakers" and "tapped horn subwoofer".

"Subsonic speakers" are usually long pipes with a resonant frequency below 20 Hz.

Several of the guys building the "collaborative tapped horn" claim response below 20 Hz.

Keep in mind that the enclosure for such a system will need to be very large.

Good luck,

Larry
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Old 18th April 2008, 03:19 PM   #6
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Also keep in mind that you are talking about infrasonic (below 20 Hz) woofers not subsonic. Subsonic means slower than the speed of sound.
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Old 18th April 2008, 03:36 PM   #7
AndrewT is offline AndrewT  Scotland
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Hi,
I don't know how large the art gallery is but I tend to think along the lines of Mavo's suggestion. High efficiency and lots of drivers to give that sub output.

You will also need pretty deep bass speakers to get down to around 30Hz to 40Hz to match up with the narrow bandwidth of the sub.
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Old 18th April 2008, 03:46 PM   #8
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Cal,

I stand corrected ... "infrasonic" is the correct term.

I read an article somewhere once that said that infrasonic sounds can cause nausea, fear, and a sense of "unearthly presence".

Thanks.

Larry
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Old 18th April 2008, 04:03 PM   #9
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there was once phoenix gold brand car subwoofer that could go infrasonic, it looks like a washing machine of some sort, and is very expensive. the design was said to be used for experimentation of elephants in the wild.

As of now, If that is really your dream, To go infra sonic, I think your best bet is the Aurasound 18" with NEO magnet . Use 20 pcs. of them in sealed boxes and power each of them with at least 500watts amp that could also go down to 10hz, build your own equalizer to augment 10hz and then put them in a regular sized room , with walls , floors and ceilings made of concrete.

Very easy to do, If you ask me.
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Old 18th April 2008, 04:11 PM   #10
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Thanks heaps for a beginning MaVo, Larry, Cal and Andrew.

I will do a search on infra-sonics (and sub-sonics so that I know what I am talking about!) and the horns that you mention.

The effect I am after is a felt wave rather than a heard one, with deep bass overtones of course....

I was kind of hoping that somebody would post a miracle easy solution. Oh well. But life is like that I guess - difficult, but fun!

I will start searching and see what comes up - thanks for some good starting points.

Sean.
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