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Double Bass A theoretical amp/speaker question - reproducing sub-sonics

Steve Freides

Steve Freides

Former Mannes College Theory Faculty
Supporting Member
Dec 11, 2007
2,576
1,508
Ridgewood, NJ
#1
A theoretical speaker question

If I were to take a tone generator, such as those you can find easily online these days, hook AI Ten2 or similar up to my computer, and started dialing the frequency down, _if_ there were no limits, somewhere around 20-25 Hz, I'd stop being able to detect a pitch, and as I passed through 20 Hz or so, I'd start being able to hear distinct pulses, almost like a metronome. E.g., 10 Hz is ought to be like setting your metronome on 600 - 10 pulses per second, times 60 seconds.

Is any/all of that right?

Is my Ten2 up to the task of trying this?

Can sub-sonics can even be called sounds?

Thanks - no practical application, just curious.

-S-
 
#2
Hi.

Every speaker is able to go down as low as You want, a fraction of a herz is hell to the motor, even in the best drivers, but it can be done.

The problem is that in a real life situation with limits, You have to monitor the power and the voice coil temperature very carefully, as You probably can't really hear a thing below, say, 20 Hz, just see the cone move. Dedicated sub-sonic drivers are a different thing, the one in my shelf still waiting for "that build" has the -3dB point in 14Hz IIRC. Takes 2Kw to power that thing to its full potential though, and since it has two 1 Ohm voice coils, that means either 0.5 Ohm or 2 ohm capable 2-3Kw amp (or a second speaker in series for 4 ohm operation). With 89dB (IIRC) sensitivity, it's not that loud though, just low.

Regards
Sam
 
#3
What you would hear would depend on the frequency response of the amplifier, how much power it is capable of delivering, and the type of waveform that was sent to the speaker.

If the waveform was a sine wave, or other very smooth waveform, you wouldn't hear anything below around 20 Hz. The sound would just die out to nothing.

If the waveform was a series of impulses, or other waveform with a sharp transition such as a sawtooth or ramp function, you would hear a transition from a distinguishable pitch to ticks or thumps.
 
#4
I'm using a demo of the NCH Tone Generator, which offers 4 different wave shapes. I'm going to try this, probably by taking a laptop over to my Ten2. I'll report back when I do.

Thank you for your comments.

-S-
 
#5
Hi.

SteveFreides said:
I'm using a demo of the NCH Tone Generator, which offers 4 different wave shapes. I'm going to try this, probably by taking a laptop over to my Ten2. I'll report back when I do.

Thank you for your comments.

-S-
Click to expand...

Again, watch very carefully that You don't over excurse the speaker when going below the tuning frequency that seems to be 40 Hz.

Below the tuning frequency it'll only take a few watts to over-excurse the driver. I'd be willing to bet there's some sort of HPF in the AI as well, in order to protect the speaker.

If You want my advice, blow something cheaper first, a car "sub" perhaps.

And I'm not kidding either.
Been there, done that, WASN'T happy afterwards. And that was during a normal test, just a sloppy turn on the dial :(.

Regards
Sam
 
#6
Frankly I'd very very careful about abusing your AI Ten2. A speaker that can easily reproduce 60 or 80 Hz at a relatively loud volume level can be very challenged to reproduce 30 or 40 Hz at even a modest volume level. At even lower frequencies it becomes increasingly easy to overdrive and overheat the driver(s) trying to get them to reproduce sounds they weren't designed to. And don't use anything but a sine wave if you're using a signal generator. Other shapes, such as square waves, are like playing with fire -- possibly literally.

If you really must do this, I'd experiment on a speaker I didn't care about.
 
#8
Well, they are called "infrasonic" frequencies, not "sub-sonic." Sub-sonic means below the speed (velocity) of sound. Infrasonic means below the limit of what is nominally audible. "Sub-woofer" is actually a misnomer to the extent that it refers to frequencies.

If you hear pulses or thumps given a sine-wave input, then you are not reproducing sign waves. Rather, you would be hearing distortion products.

Now, with all due respect, running this experiment with a driver about which you care, may be one of the dumbest moves you can make. As others have correctly pointed out, you will quickly reach the excursion limits of the driver. For a constant input voltage to the driver in an infinite baffle, displacement of the cone of the driver is inversely proportional to frequency. Now, put that driver in a tuned cabinet and the simple relation goes out the window.

Assuming that nothing is over-driven and that you're testing with sine waves, then, as others have pointed out, the output will simply become inaudible. At some point, it'll be replaced by a tactile perception (you can feel it), assuming the driver in the cab is radiating enough power to produce that. For your speaker in its cabinet, by then you'll likely have bottomed out the voice coil, potentially done damage, and, perhaps, smell something nasty and even see some smoke.

Listen to T-Bird.
 
#9
SteveFreides said:
A theoretical speaker question

If I were to take a tone generator, such as those you can find easily online these days, hook AI Ten2 or similar up to my computer, and started dialing the frequency down, _if_ there were no limits, somewhere around 20-25 Hz, I'd stop being able to detect a pitch, and as I passed through 20 Hz or so, I'd start being able to hear distinct pulses, almost like a metronome. E.g., 10 Hz is ought to be like setting your metronome on 600 - 10 pulses per second, times 60 seconds.

Is any/all of that right?



-S-
Click to expand...

Hey there, are you doing this to explore the relationships between how our brains perceive rhythm and pitch?

I did something for a class university a while back, going the other way. I started with a rhythm, 3:2 polyrhythm that one can hear, and then using a computer sped it up until it became it a pitch. At a point one could hear the P5 interval, and then it just became a timbre.

My "piece" (homework assignment) was like an X. At the start, one hears the rhythm and a note way up there. The rhythm starts the get faster, and the note starts lowering in pitch. After a point the rhythm turned into a pitch and kept going up and the two notes met. Then the note slowly started turning into a rhythm. At the end of the piece, the rhythm was a pitch way up, and the pitch a rhythm way down, same as the beginning but reversed.

Starting with an audible rhythm to create a pitch as it is sped up, seems to be quite a different thing than starting with a natural pitch and trying to slow it down to hear a rhythm in regards to speakers and amps. The other folks explained it better.
 
#11
Ric Vice said:
Steve and Les
As I recall the U.S. military was exploring using infrasonics
as pulse shock weapons. Of course, you speaker will most likely implode before you get to those levels. Mother Nature really doesn't want us to go there.

:hiding:

Ric
Click to expand...

Uh... then there was the finding, IIRC, that sufficient energy around 6 Hz causes some loss of normal bowel function. :eek:
 
#12
drurb said:
Uh... then there was the finding, IIRC, that sufficient energy around 6 Hz causes some loss of normal bowel function. :eek:
Click to expand...

Yes the infamous "brown note". I believe Meyer Sound took part in one experiment with founder John Meyer providing a test rig that provided over 150 db at 9 hz and some what less at 5 hz. Apparently nausea is produced at these frequencies but no loss of bowel control was evident.

read more Brown note - Wikipedia, the free encyclopedia



bob
 
#13
bassphase said:
Yes the infamous "brown note". I believe Meyer Sound took part in one experiment with founder John Meyer providing a test rig that provided over 150 db at 9 hz and some what less at 5 hz. Apparently nausea is produced at these frequencies but no loss of bowel control was evident.

read more Brown note - Wikipedia, the free encyclopedia



bob
Click to expand...

Thanks for some closure on a ****ty topic. :)
 
#14
Ric Vice said:
Steve and Les
As I recall the U.S. military was exploring using infrasonics
as pulse shock weapons. Of course, you speaker will most likely implode before you get to those levels. Mother Nature really doesn't want us to go there.

:hiding:

Ric
Click to expand...

I'm sure that the damage caused has as much to do with the volume as the frequency. There are animals that make and hear sounds too low for humans to hear. Elephants communicate with sounds as low as 15 Hz, and several species of whales "speak" even lower than that. Blue whales have the lowest, loudest voices in the animal kingdom, and scientists believe that they can hear each others' vocalizations from thousands of miles away. (Remember that sound carries better in water than in air).

- Hal -
 

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