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Old 16th November 2012, 05:32 PM   #11
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Quote:
Originally Posted by Rive View Post
Obviously, the first question that comes to mind is, "is it music if you can't hear it?" Well, I'm going to sidestep that question altogether and move onto "what does infrasonic music sound like?"

I would at least like to get to 10 Hz any lower than that is bonus in my mind.

Being a college student, my funds are limited, but I can get some money from the school, but not a whole lot, so I will peg my budget at around $800.
I am not a fan of the term "infrasonic", low frequency can be heard down to a few Hz when loud enough.

The hugely expensive Thigpen rotary sub has a maximum output of only around 110dB between 0 and 30Hz at one meter. At 10 Hz, an output of 110 dB sounds about as loud as a quiet conversation, 60 dB at 1000 Hz.
Down around 5 Hz, it takes upwards of 140 dB to be audible.

For loud, low and cheap (other than the wood required) tapped horns offer the best bang for the buck to go low.

TH have a smooth range of around 2 octaves, going from 5Hz to 20Hz would not be a problem.
You will probably have to design the TH yourself, as none of the designs on the forum are optimized for operation below 20 Hz.

Look up Josh Ricci’s TH Gjallerhorn, it would be a good start for your design.
Gjallerhorn
At 2 meters, ground plane, outdoors it measures:
10hz 90.2db
12.5hz 105.2db
16hz 118.3db
20hz 122db
25hz 124.9db
31.5hz 125.8db
40hz 128.4db
50hz 127.2db
63hz 130.2db
80hz 130.9db
100hz 131.1db
125hz 123.6db

Add 6 dB to those figures for a one meter equivalancy, and another 6 to 12 dB for indoor corner loading, and other than in the single digit frequencies it has far more output capability, and costs far less than the Thigpen.

The Gjallerhorn is designed around a very expensive speaker, but by using multiple less expensive speakers in isobaric configuration you could meet your design goal of $800.
Hornresp is an excellent free program, start out by copying the Gjallerhorn, but make each of the horn segments twice as long.
Four Eminence Lab 12" or TC Epic 12" in two isobaric pairs would be good cost effective driver choices.
Isobaric pairs will allow for lower frequency output in a smaller cabinet, but if you can afford the wood and space, use regular loading, it will put out more output per driver.

That said, there is no replacement for displacement, the output level will be tied to the money spent on drivers and loads of plywood to house them.

Art Welter

Last edited by weltersys; 16th November 2012 at 05:39 PM.
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Old 16th November 2012, 05:57 PM   #12
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Art, this fellow wants stuff below 15Hz. it would seem...

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Old 16th November 2012, 06:09 PM   #13
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Originally Posted by bear View Post
Art, this fellow wants stuff below 15Hz. it would seem...

_-_-bear
Exactly why I suggested tapped horns, as I mentioned, TH have a smooth range of around 2 octaves, going from 5Hz to 20Hz would not be a problem.

It's not all that difficult to design "infrasonic" speakers, but since they are not very useful for music (and are huge and expensive), few bother.

An exception is the Matterhorn, a 40-driver, 40 kW self-powered Tom Danley designed tapped horn which can produce 105 dB of output at 250 meters, with a response -3 dB at 12 Hz.
That is about the equivalent of 153 dB at one meter !

http://www.danleysoundlabs.com/matterhorn.htm

I think it is still sitting behind the DSL building in Atlanta, the OP might get a demo and hear what some real LF can do .

Art

Last edited by weltersys; 16th November 2012 at 06:11 PM.
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Old 16th November 2012, 07:07 PM   #14
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Old 16th November 2012, 07:34 PM   #15
Rive is offline Rive  United States
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Originally Posted by chris661 View Post
Here's what I'd do..

Get a couple of those cheap MCM 8" long-throw drivers.

Build a box big enough to stand/sit in.

Mount the 8" drivers in the box, make sure the door is well-sealed, and eq the design flat to as low as you like, with you inside.

Getting SPL at <20Hz in a room is difficult.
Getting it in a relatively small box will be easy, and give you a fair idea of what it'll sound like - put a couple of smallish bookshelf speakers in there too, to cover the rest of the range.

Chris

That's an interesting idea. A few researchers in the article Thresholds of audibility for very low-frequency pure tones by Norman S. Yeowart and Margaret J. Evans used this same method, though with considerably larger drivers and a much more expensive box set up. Theirs was an airtight aluminum box with a volume of about 1250L. This method is extremely effective for as you said, getting effective SPL at lower frequencies, though it is a bit terrifying for my audience to be sealed in an airtight box. It's a unique performance space to say the least, and I'll keep it in mind.
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Old 16th November 2012, 08:08 PM   #16
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Adding to the others thoughts here but on the subject of money. Any DIY speaker builder soon finds out that chasing that next lower octave is expensive, going 2 complete octaves down is going to be double doubly expensive and no matter what you do., i don't think your budget will be anywhere near enough.

Add Bag End and Rod Elliot ( project 48A ) to your gooogle search for another approach to the matter and add a zero to your budget, or more depending on room size.
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Old 16th November 2012, 08:30 PM   #17
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Quote:
Originally Posted by Rive View Post
I've found plenty of information on infrasound and its alleged psycho-
physiological effects on humans, its natural and unnatural sources,
even some experimentation with augmenting musical performances
with low frequency pure tones on frequencies just shy of the range
of human hearing attempting to invoke the strange "chills down the spine"
feeling that infrasound has gotten a name for. Trust me, when it comes to
documentation, I've got a meaty pile of resources, that's not the issue.
Hi,

Look for spaces that will have natural modes at these sub frequencies.

7Hz is around the natural resonance of your guts in you abdomen,
and ambulances take a lot of care avoiding it mechanically.

FWIW its simply not a worthwhile topic to pursue regarding normal
music reproduction, live performance, under circumstances, perhaps.

rgds, sreten.
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Old 16th November 2012, 08:58 PM   #18
Rive is offline Rive  United States
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Originally Posted by weltersys View Post
I am not a fan of the term "infrasonic", low frequency can be heard down to a few Hz when loud enough.
Yeah, I recently read this in the article I sighted previously, though they did speculate that pure tones are not "heard" in the conventional way, but are more a product of bone induction and distortion in the middle and inner ear rather than a true detection of the vibration of the tympanic membrane. I just call it infrasound for lack of a better name.

Quote:
Originally Posted by weltersys View Post
For loud, low and cheap (other than the wood required) tapped horns offer the best bang for the buck to go low.

TH have a smooth range of around 2 octaves, going from 5Hz to 20Hz would not be a problem.
You will probably have to design the TH yourself, as none of the designs on the forum are optimized for operation below 20 Hz.
This is extremely helpful, thanks. The last pair of speakers I worked on were of a similar TH design and I was hoping to go this route again. Just the proportions of the box I had speculated are a bit intimidating. I'm a much better musician than I am a carpenter, but I have a good amount of time and dedication to this project.

Quote:
Originally Posted by weltersys View Post
The Gjallerhorn is designed around a very expensive speaker, but by using multiple less expensive speakers in isobaric configuration you could meet your design goal of $800.
Hornresp is an excellent free program, start out by copying the Gjallerhorn, but make each of the horn segments twice as long.
Four Eminence Lab 12" or TC Epic 12" in two isobaric pairs would be good cost effective driver choices.
Isobaric pairs will allow for lower frequency output in a smaller cabinet, but if you can afford the wood and space, use regular loading, it will put out more output per driver.

That said, there is no replacement for displacement, the output level will be tied to the money spent on drivers and loads of plywood to house them.

Art Welter
I'm going to look into this right away, thanks so much for this.
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Old 16th November 2012, 09:03 PM   #19
Rive is offline Rive  United States
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Originally Posted by gberchin View Post
Tactile transducers. Parts Express
This was another one of my plans, and I could actually do this extremely cheaply. The downside is that I could only perform my composition for one person at a time. Also, my area of focus is in the sort of ambient infrasound, the kind that is subtly experienced. I feel that the obvious shaking that occurs from tactile transducers is going to misrepresent infrasound.
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Old 16th November 2012, 09:09 PM   #20
Rive is offline Rive  United States
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Originally Posted by Moondog55 View Post
Adding to the others thoughts here but on the subject of money. Any DIY speaker builder soon finds out that chasing that next lower octave is expensive, going 2 complete octaves down is going to be double doubly expensive and no matter what you do., i don't think your budget will be anywhere near enough.
Yes, this is exactly my problem and fear. I find all of these resources that talk about the "chasing" extensively. Tons of people problem solving on how to squeeze out a few extra Hz. My hope is that if I can eliminate the need for audible sound in the design then it might shave off some of the cost, though I'm not sure how or even if that's a possible step. Just the nature of sound makes playing infrasonic tones with conventional consumer grade speakers extremely tedious.

It seems that I'm going to need to make some compromises somewhere. I want to get as much advice as I can, though, before I make those decisions.
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