Levitation- Standing Waves

[audiobaun 5,000+ posts]

Awesome thread and valued information. very interesting for sure man.!

 

[Buck 5,000+ posts]

Distance is frequency, different distances change resonance due to wave speed and length. This is just a great visualization. When he moves the reflector and the levitation stops, that seems to me like playing a note, then suddenly making an enclosure out of resonance with the speaker frequency, so stored energy resonance is quickly lost. That's why there's different lengths to ports in sound; you lose so much energy out of resonance.

Ultrasonics - Sound - Harmonics - CTG Technical Blog

In fact, most objects can resonate at more than one frequency and in multiple modes of vibration.

techblog.ctgclean.com

Good read there gets into 1/2 wave and 1/4 wave, which a subwoofer t-line is a 1/4 wave tuned structure. Dude talks about 1/2 wave resonance with the reflector plate distance from speaker in the video.

 

[Buck 5,000+ posts]

"Here's a frequently asked question: if a quarter-wave is 90 degrees in phase length, why does it transform you 180 degrees on a Smith chart? Consider that here we are plotting reflection coefficients on the Smith chart. Thus, an imaginary signal that you send through a transmission line of one quarter wavelength must travel fully half a wavelength, since it travels down the quarter-wave line, gets reflected, then returns down the quarter-wave line."

Microwaves101 | Quarter-wave Tricks

Microwaves101 | Quarter-wave Tricks

www.microwaves101.com

There's an astonishing similarity between the physics of the resonances of electronics (like a wire) and the resonances of air with sound (like a sub t-line box), like how I've designed boxes. It's all just waves moving through a medium. Your different boxes for the same sub change the electrical nature of the sub the amp sees, so keep that in mind. In other words, different box types and styles greatly impact sub coil movement through the motor magnet, which (can) greatly change the electrical impact of the sub's stress or feedback into the whole system (sub impedance changes).

 

[Buck 5,000+ posts]

I also learned a good bit reading this site: http://www.quarter-wave.com/

 

[Buck 5,000+ posts]

"Here's a frequently asked question: if a quarter-wave is 90 degrees in phase length, why does it transform you 180 degrees on a Smith chart? Consider that here we are plotting reflection coefficients on the Smith chart. Thus, an imaginary signal that you send through a transmission line of one quarter wavelength must travel fully half a wavelength, since it travels down the quarter-wave line, gets reflected, then returns down the quarter-wave line."

Microwaves101 | Quarter-wave Tricks

Microwaves101 | Quarter-wave Tricks

www.microwaves101.com

There's an astonishing similarity between the physics of the resonances of electronics (like a wire) and the resonances of air with sound (like a sub t-line box), like how I've designed boxes. It's all just waves moving through a medium. Your different boxes for the same sub change the electrical nature of the sub the amp sees, so keep that in mind. In other words, different box types and styles greatly impact sub coil movement through the motor magnet, which (can) greatly changes the electrical impact of the sub's stress or feedback into the whole system (sub impedance changes).

"The comparison between an acoustic duct and an electrical transmission line is useful in "lumped-element" modeling of acoustical systems, in which acoustic elements like volumes, tubes, pistons, and screens can be modeled as single elements in a circuit. With the substitution of pressure for voltage, and volume particle velocity for current, the equations are essentially the same.[2] Electrical transmission lines can be used to describe acoustic tubes and ducts, provided the frequency of the waves in the tube is below the critical frequency, such that they are purely planar."

Acoustic transmission line - Wikipedia

en.m.wikipedia.org

 

[Buck 5,000+ posts]

Nice little read on visualizing how 1/4 wave resonance works, such as with a transmission line:

Resonance

home.cc.umanitoba.ca

A subwoofer 1/4 wave resonator:

Very simple way to make good sounding bass is just put your sub in a port that's the Sd of your sub and 1/4 wavelength of sub Fs or whatever frequency you want to peak bass at most. It's that simple; that is a basic subwoofer transmission 1/4 wave line enclosure.

 

[Buck 5,000+ posts]