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Low Frequency Subwoofers

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Platinum - Posts: 5,054
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: May 09, 2005 at 6:42 AM / IP Logged  
Poormanq45 wrote:
Good read. Note that I just said that it requires an extreme amount of power to get a useable tone at sub-sonic frequencies
No, It's cool... Also note, I said nothing about that NOT being true in my previous post...
However, I am now going to say that is not NECESSARILY true. I have mentioned before the 18 inch transmission line subwoofers I helped build for/with my buddy Dave.    Here is the link to see the smaller of them... the other is approximately 4 inches larger in cross-section, and 6 inches longer. In room, these monsters will reach 112dB at 18Hz, with only 20 watts per channel! (I will admit, 18Hz IS an even order harmonic of the room's resonant frequency - a ghastly 72Hz, floor to ceiling, and 36Hz, wall to wall, TWICE... for a 12dB peak at 36Hz - Blech! - square rooms SUCK for bass...) At 13Hz and 12Hz, (their resonant frequencies, respectively) we honestly don't KNOW how loud they get, as we never had a mic that was effective at those frequencies. I will tell you, though, when we decided to go for an Fs of 15, and the tuning ended up that much lower, we never MEANT to land RIGHT on the resonant frequency of the house in which they are installed! With less than 25 watts @ 13Hz we have LITERALLY vibrated the garage door - and I ain't talking just a little vibe, either - it was more like a SHAKING of the garage door!
So you see, your statement is a little misleading... Not wrong, however... It is possible to achieve EXTREME output in the subsonic regions, with a very SMALL amount of power, you just need to be certain your system is designed properly to PRODUCE such a frequency, and the room helps. Low Frequency Subwoofers - Page 2 -- posted image.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Silver - Posts: 246
Silver spacespace
Joined: November 17, 2004
Location: United States
Posted: May 09, 2005 at 7:55 AM / IP Logged  
get on ebay and pick up a phoenix gold cyclone. thats what they're made for
Moderator - Posts: 10,741
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Joined: April 22, 2003
Location: Arizona, United States
Posted: May 09, 2005 at 12:07 PM / IP Logged  

Extremely low frequencies at sufficient SPL have been shown to cause loss of voluntary muscle control.  I was involved in a project with the Navy back in the 70's looking at this very phenomenon.  However, it is extremely unlikely and probably impossible for any commercially available audio system to generate sufficient pressure waves to cause this.  And if it had been accomplished. it would not affect selective human bodies but rather everyone within the pressure wave boundary.  Low frequency sounds cannot be "aimed."  So if one person had "crapped themselves," so would have everyone who happened to be the same distance or closer to the source.  (This, by the way, was predicted using mathematical models and proven in a warehouse on Mare Island, California in May 1979 when a test system was energized and six people within a 20 foot radius fell to the floor.  The system generated 4.3Hz at approximately 210dbC.)

Back to the original question, any good subwoofer can generate all the lower audible frequencies, but it is the system design that determines actual response below 100Hz (as haemphyst has described.)  Most people cannot hear anything lower than about 25Hz, by the way, although sounds below 50Hz are easily felt in your body's sympathetic vibrations.  Prolonged exposure to 85db is sufficient to cause hearing loss below 100Hz.

Silver - Posts: 584
Silver spacespace
Joined: June 21, 2004
Location: United States
Posted: May 09, 2005 at 12:11 PM / IP Logged  
Imagine the chicks I could pick up if I had subs that made people pass out.
Tell the Snap-On guy I'm not here!
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