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What happens with a low frequency vibration on a loudspeaker

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What happens with a low frequency vibration on a loudspeaker

Postby jltfromtheb » Thu Feb 08, 2018 6:37 pm

If you somehow apply a tonic tension that results in a low frequency vibration or another sort of vibration of any frequency even, will this processing passageway combine with the sound it's given to process, by attaching a low frequency emission to the sound (or whatever frequency the loudspeaker is vibrating at on its own) ? Or will it just keep vibrating the same and not interfere with the incoming sound? I mean, loudspeakers are supposed to be silent, right? If they aren't then they'll attach sounds to incoming sounds, no? If it does attach, does it do so with far greater force on signal than with noise? If so what is the name of this phenomenon? It's not reverberation because reverberation does so in parallel with both signal and noise.
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Re: What happens with a low frequency vibration on a loudspeaker

Postby Martin Walker » Thu Feb 08, 2018 7:34 pm

Hi jltfromtheb, and welcome to the SOS Forums! 8-)

However, I can't help that the word 'homework' springs into my mind when reading this :beamup:


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Re: What happens with a low frequency vibration on a loudspeaker

Postby jltfromtheb » Thu Feb 08, 2018 7:42 pm

Lol. Thanks for the welcome :)

I promise it's not homework from school or something, but from something else entirely. I'll reveal it at the end of the thread not now to not break any bias in any possible answers. Also I am truly clueless about this subject, I'm looking for some sort of a thermodynamic sound reason for why the above would happen or something :)
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Re: What happens with a low frequency vibration on a loudspeaker

Postby Hugh Robjohns » Thu Feb 08, 2018 8:15 pm

I'm going to assume that English is not your first language, purely on the basis that what you've written in both posts so far makes very little sense. :?

However, extrapolating between the recognisable phrases, I think you might want to research the terms SUPERIMPOSITION and NON-LINEAR INTERMODULATION to find your answer.

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Re: What happens with a low frequency vibration on a loudspeaker

Postby zenguitar » Fri Feb 09, 2018 12:53 am

The problem with being cryptic is that few, if any, people have any idea what you are talking about or why. If you have a question to ask it is always far better to ask it clearly and explain. If you are planning to explain 'later', most of us will sit back and wait for the explanation.

:)

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Re: What happens with a low frequency vibration on a loudspeaker

Postby jltfromtheb » Fri Feb 09, 2018 6:21 am

I'm sorry if I didn't explain myself properly.

I come from no knowledge of sound mechanics. Thanks for those suggestions in regards to superimposition and non-linear intermodulation. I read up on them tonight and if I'm not mistaken they refer to frequencies.

However I am not too concerned with frequencies. They may be important, but I'm trying to understand something else right now. I'm thinking of an amplifier that might add its own sound of a specific frequency to the incoming sound it's treating, but first of all I want to understand a couple of things about its loudness and its suddenness. I'm thinking of a sound amplifier that sounds normal for the sounds it's treating if it's silent, but adds too many decibels to the incoming sound if said amplifier, while in silence, has entered a state of permanent vibration. I'm wondering if there's any knowledge you might have, or a theory that might explain why this vibrating amplifier thuds, vibrates and adds decibels to the incoming sound (instead of for instance merely absorb it), and why it does so predominantly when the incoming sound is a signal, increasing its vibration and thudding with noise at a much smaller intensity. My understanding of signal and noise, which may be wrong may not be, is that signal is when a sound changes in intensity, whereas noise is the background leveled out noise.
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Re: What happens with a low frequency vibration on a loudspeaker

Postby The Korff » Fri Feb 09, 2018 8:21 am

Any of you lot believe in the theory of Jungian Synchronicity?

I was editing a paragraph about IMD in a Phil Ward review only the other day. In it, he was explaining the benefits of port-loading a speaker (something I've never heard him do; regular readers will know his attitude is normally 'infinite baffle or go home!').

Anyhoo, in this text Phil explained that, because ports inherently limit LF driver excursion, they have the happy side-effect of reducing intermodulation distortion — because the greater the excursion, the more low frequencies modulate the output of high ones. And while the port picks up the slack in terms of LF output, it doesn't impose itself on the output of the cone.

So there you go. Spooky!
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Re: What happens with a low frequency vibration on a loudspeaker

Postby Hugh Robjohns » Fri Feb 09, 2018 9:53 am

jltfromtheb wrote:However I am not too concerned with frequencies. ... I'm thinking of an amplifier that might add its own sound of a specific frequency to the incoming sound it's treating...

Sounds like you're interested in frequencies to me! ;)

I'm thinking of a sound amplifier that sounds normal for the sounds it's treating if it's silent

How can an amplifier be 'silent' if it is amplifying sound? That makes no sense.

... but adds too many decibels to the incoming sound if said amplifier, while in silence, has entered a state of permanent vibration.

Do you mean the amplifier is oscillating? If so it is broken.

Or perhaps you're talking about a live-sound situation in which 'feedback' is occurring -- the whistling or howling sound that occurs when the microphones pick up the sound from the speakers and re-amplify it to create that obvious unstable 'oooooow' sound?

My understanding of signal and noise, which may be wrong may not be, is that signal is when a sound changes in intensity, whereas noise is the background leveled out noise.

All electronic equipment generates some noise, but that is usually very quiet and forms a constant background hiss. The Signal is the (usually) much louder wanted part of the sound -- the voices or music etc.

But I'm still not sure how these relate to your earlier comments. :?
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Re: What happens with a low frequency vibration on a loudspeaker

Postby Hugh Robjohns » Fri Feb 09, 2018 9:56 am

The Korff wrote:....ports inherently limit LF driver excursion...

Only down to the port's resonant frequency; below that there is no damping effect on the driver at all... which can result in damage!

I still remember reading a Hugh Ford technical review of the ATC SCM100 active monitor in Studio Sound magazine many decades ago where he pointed out that the bass driver flapped about like a wild thing below 20Hz (or thereabouts) for this very reason!

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Re: What happens with a low frequency vibration on a loudspeaker

Postby The Korff » Fri Feb 09, 2018 10:14 am

Happily, the monitor in question has a high-pass filter just below the port's resonant frequency, for exactly that reason!
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