I have alot of questions about acoustics, both in car audio, high end home,. And exotic.
If I Invision the simplest passive Radiators enclosure, it's a tube with a passive at one end, and a driver at the other, int the shape of a u such that both passive and driver are colocated. If the tube is the correct length, such that length = length / speed of sound = a whole number multiple of the frequency being played. In this situation it will yield the best possible output and sound. But only at that frequency.
I am an engineer and a physics want to be,. But I can think of a number of ways to make rapid changes to the different properties of an enclosure and or the driver which would allow for the running frequency being changed, on the fly, each time the frequency of the output changes. I worked in nanotechnology alot,. And I'm certain that I could design such an enclosure. So I'm sure other have. If not, and anyone would like me too, I will. But if I am missing something that fundamentally creates a problem,. Ide rather someone tell me.
I would use some type of microwave structure which can be opened and closed nearly instantaneously to modify the length of the tube,. And a variable magnetic field to regulate the resent frequency of the passive.
Ben
If I Invision the simplest passive Radiators enclosure, it's a tube with a passive at one end, and a driver at the other, int the shape of a u such that both passive and driver are colocated. If the tube is the correct length, such that length = length / speed of sound = a whole number multiple of the frequency being played. In this situation it will yield the best possible output and sound. But only at that frequency.
I am an engineer and a physics want to be,. But I can think of a number of ways to make rapid changes to the different properties of an enclosure and or the driver which would allow for the running frequency being changed, on the fly, each time the frequency of the output changes. I worked in nanotechnology alot,. And I'm certain that I could design such an enclosure. So I'm sure other have. If not, and anyone would like me too, I will. But if I am missing something that fundamentally creates a problem,. Ide rather someone tell me.
I would use some type of microwave structure which can be opened and closed nearly instantaneously to modify the length of the tube,. And a variable magnetic field to regulate the resent frequency of the passive.
Ben
Perhaps you meant to say you could increase a resonance by combining different factors. What that has to do with best output and sound, I'm not sure.
Well, my thinking is that the best output sound as well as the most efficient, would ooccur when the length of the tube is precisely the same as the the wavelength of sound in air of that density. So the PR is in phase with the driver - 2pi rads. And when the resonent frequency of the PR is the same as the frequency of the input.
Say the PR has voice oil and magnet,. (Not intended to drive,. But to vary the resonent frequency of the the PR to mage the input frequency at any given instant.
The tube length would need to be varied to match said frequency as well. That is much more difficult to accomplish rapidly,. But the same effect could be achieved by varying the air temp or pressure and density inside the tube. Or by a number of other methods, most would require some work.
I may just need to learn the math.
Say the PR has voice oil and magnet,. (Not intended to drive,. But to vary the resonent frequency of the the PR to mage the input frequency at any given instant.
The tube length would need to be varied to match said frequency as well. That is much more difficult to accomplish rapidly,. But the same effect could be achieved by varying the air temp or pressure and density inside the tube. Or by a number of other methods, most would require some work.
I may just need to learn the math.
Yes, I got that from your first post. Ok, lets say this causes large output at that frequency. Will that not be out of place?
This will not readily change the resonant frequency.
I guess my unwarranted supposition was that with a subwoofer, any given instant would have a single frequency. Would it not?
It would, if a constant current is applied to a coil attached to the PR, in the presence of a stationary magnet, it will change the resonent frequency of that subststem
Not at all. An acoustic transient, such as a kick drum being hit by the beater of a pedal, has energy at all frequencies 'from DC to blue light' simultaneously starting at the impact and decaying to the fundamental tuning frequency of the drum skin along with the characteristic ratio of harmonics (multiples of the fundamental) for a drum. A note that is not in steady-state implies there is transient content with a broadband, noise-like energy spectra.
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Complex Waveforms, can be anywhere from 2 to Thousands of sinewaves.
And music is full of complex waveforms.
As far as ported or passive radiators, every Audio enclosure has trade offs and benefits.
Up to the designers what they want to accept and need.
To improve low end extension or frequency response, many choose not to use ported or passive.
They use drivers capable of doing so in a sealed application.
Which comes with the usual tradeoffs and benefits.
Vented/Reflex or Passive have a tradeoff of reduced transient at the resonate frequency.
Cone movement is reduced when the port takes over. It is one of the many downfalls or trade offs
of a reflex system.
Basically its bad enough they are tuned to one frequency, not sure why you would want
to change resonance, to ruin even more of the bandwidth. Ideally you want resonance to be low as possible.
So it has less effect on the upper transients or basically the bandwidth your trying to accurately create.
Pressure needed to make resonance does not magically come from nowhere. It comes from the speaker.
So whatever pressure is needed to make port work, comes from the speaker. Speaker no longer
can accurately reproduce the complex waveforms its being feed. Its now putting energy into the port instead.
And music is full of complex waveforms.
As far as ported or passive radiators, every Audio enclosure has trade offs and benefits.
Up to the designers what they want to accept and need.
To improve low end extension or frequency response, many choose not to use ported or passive.
They use drivers capable of doing so in a sealed application.
Which comes with the usual tradeoffs and benefits.
Vented/Reflex or Passive have a tradeoff of reduced transient at the resonate frequency.
Cone movement is reduced when the port takes over. It is one of the many downfalls or trade offs
of a reflex system.
Basically its bad enough they are tuned to one frequency, not sure why you would want
to change resonance, to ruin even more of the bandwidth. Ideally you want resonance to be low as possible.
So it has less effect on the upper transients or basically the bandwidth your trying to accurately create.
Pressure needed to make resonance does not magically come from nowhere. It comes from the speaker.
So whatever pressure is needed to make port work, comes from the speaker. Speaker no longer
can accurately reproduce the complex waveforms its being feed. Its now putting energy into the port instead.
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