A Question That Has Burned In My Mind For Years...

laatsch55

Administrator,
Staff member
Joined
Jan 14, 2011
Messages
74,476
Location
Gillette, Wyo.
Tagline
Halfbiass...Electron Herder and Backass Woof
#1
How can a driver...say a woofer...reproduce frequencies from 30hz to 300hz , simultaneously....AND how does the ear hear these simultaneously?? Seems to me while a woof would be doing 30hz, it could not do anything else till that was accomplished...
 

Gepetto

Administrator
Staff member
Joined
May 15, 2011
Messages
13,711
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
#2
Dayam Lee...

The sound of multiple instruments and voices superimpose themselves in the air to produce a live sound. That superimposed set of sounds produces a complex waveform in the air pressure representing all of them simultaneously. The microphone picks this complex air pressure waveform and transforms it from a mechanical to electrical complex waveform which is then stored in various media forms. Upon playback, the amplifiers reproduce that complex waveform and send it to your woofer, mid and tweeter which reverse what the microphone did. Converting electrical to mechanical air pressure for you to hear.

The human body and ear are much more complex than that, so don't go there...
 

laatsch55

Administrator,
Staff member
Joined
Jan 14, 2011
Messages
74,476
Location
Gillette, Wyo.
Tagline
Halfbiass...Electron Herder and Backass Woof
#5
Funny Nando...!!

Joe, I've watched music waveforms on the scope...looked like a hot mess to me. Especially to reproduce...
 

Gepetto

Administrator
Staff member
Joined
May 15, 2011
Messages
13,711
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
#6
Funny Nando...!!

Joe, I've watched music waveforms on the scope...looked like a hot mess to me. Especially to reproduce...
Yup, complex indeed. The speakers do their best to follow that hot mess waveform. Your speaker crossovers separate the frequencies allowed by the crossover bandpass and make a modified hot mess to go to each speaker, woofer, mid, tweeter.
 

laatsch55

Administrator,
Staff member
Joined
Jan 14, 2011
Messages
74,476
Location
Gillette, Wyo.
Tagline
Halfbiass...Electron Herder and Backass Woof
#7
Yeah, but I still can't get my head wrapped around a driver being able to reproduce distinct frequencies simultaneously...lets say you have a 30hz toner lasting a second, and a 250hz tone lasting that same second. What gets compromised the 30 hz or 250hz?
 

Gepetto

Administrator
Staff member
Joined
May 15, 2011
Messages
13,711
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
#8
Yeah, but I still can't get my head wrapped around a driver being able to reproduce distinct frequencies simultaneously...lets say you have a 30hz toner lasting a second, and a 250hz tone

lasting that same second. What gets compromised the 30 hz or 250hz?
That is what inter modulation distortion is all about Lee
 

Elite-ist

Administrator, (and straight-up pimp stick!)
Staff member
Joined
Jun 12, 2010
Messages
9,848
#10
And then roll the importance of damping factor of the power amplifier into the equation.

Nando.
 

laatsch55

Administrator,
Staff member
Joined
Jan 14, 2011
Messages
74,476
Location
Gillette, Wyo.
Tagline
Halfbiass...Electron Herder and Backass Woof
#11
Ok...starting to make sense...so.....that has to be why diaphram mass is so critical, along with surround design for reversing cone travel. Is a woofer diaphram doing things we can not see with the eye?
 

62vauxhall

Veteran and General Yakker
Joined
May 14, 2014
Messages
2,303
Location
Southwest Kootenays BC
Tagline
No such things as bad days, just bad moments
#12
Celestion (and apparently Wharfedale too) used High Speed Laser Interferometry to create 3D "topographical maps" of driver surfaces in operation.

In 1982 Celestion launched an innovative hi‑fi speaker called the SL6. It deployed one of the first 'modern' metal-dome tweeters — one that employed copper pressed (literally) into service as both diaphragm and voice-coil former — and a thermoplastic-coned bass/mid driver with an unusual dust cap and surround design. Both drivers had been developed using laser interferometry. Laser interferometry employs a laser to scan across a moving surface, with analysis of the Doppler effect changes in frequency of the reflected light used to derive the detail of the movement. Using laser interferometry, Celestion could create slow-motion 3D animations of the movement of driver diaphragms and so optimise their mechanical design. It was a brilliant application of technology and Celestion's marketing department understandably made a big fuss about it. However, it wasn't entirely new: Peter Fryer at Wharfedale in 1971 had used the same technique to help inform the design of a new thermoplastic‑coned mid-range driver.
 

laatsch55

Administrator,
Staff member
Joined
Jan 14, 2011
Messages
74,476
Location
Gillette, Wyo.
Tagline
Halfbiass...Electron Herder and Backass Woof
#13
Coolness Gary...thanks..so my questions have been asked before, many times by those with a WHOLE lot more smarts...
 

AngrySailor

Veteran and General Yakker
Joined
Oct 15, 2014
Messages
3,419
Tagline
---not quite right
#14
Possibly a simpler way to look at this would be octaves or evenly divisible frequencies? I often wondered how this worked electrically and that mystified me more than the physical woofer reproducing that signal... play a song that’s in a minor key or with heavy dissonance, I think these are the hardest for a speaker to physically reproduce and some fall on their face...
 

Gibsonian

Chief Journeyman
Joined
Aug 3, 2011
Messages
791
#16
Always amazed me too Lee as well that a driver could do all that simultaneously. The ear part, nah, our best engineer on that one so I never wondered there. But the little cone doing all those frequencies and responses so accurately, made out of paper, all at the same time is a tough one it would seem. That Celestion scan showing what parts move in relation to the input would be interesting thing to see, might help wrap our minds around it better. The voice coil must do all within the required freq range, for sure, the cone, might see some differences in relation to distance from the VC, esp on the bigger cones.

And dual voice coils in same driver, one responsible for different frequencies than the other, more wizardry. Joe's explanation was like the sex explanation to a young child,, missing some important details I think! Maybe he is protecting our fragile minds.......
 

Gepetto

Administrator
Staff member
Joined
May 15, 2011
Messages
13,711
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
#17
Ok...starting to make sense...so.....that has to be why diaphram mass is so critical, along with surround design for reversing cone travel. Is a woofer diaphram doing things we can not see with the eye?
Absolutely it is Lee.
 

Gepetto

Administrator
Staff member
Joined
May 15, 2011
Messages
13,711
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
#18
Ok...starting to make sense...so.....that has to be why diaphram mass is so critical, along with surround design for reversing cone travel. Is a woofer diaphram doing things we can not see with the eye?
If you had a driver with zero mass and no reactance (inductance or capacitance) in the voice coil, you would eliminate the mechanical time constant and electrical time constant associated with real world woofers and tweeters. If those zero time constant drivers were operated in a perfect vacuum, you would approach an ideal driver situation. Unfortunately they have to move air to be effective and let you hear anything :)
 

MarkWComer

Veteran and General Yakker
Joined
Nov 1, 2014
Messages
3,368
Location
Gaston, SC
Tagline
Victim of the record bug since age five
#19
Okay, dogs- looks like I have to git my crayons 'n' draw pictures for ya's...

Top wave: 60Hz sine wave
Middle wave: 45Hz sine wave
Bottom wave: Both sine waves combined, now is no longer a sine wave, but a simplified "complex" wave.

Neither of those frequencies are compromised but interact with each other, a vertical line drawn from either the 60Hz or 45Hz wave will show a corresponding peak on the combined wave. Simplified to its most elemental form, but this is how vocal waves combine with guitar waves with violin waves with (ad nauseum...).

Further thought: consider how audio frequencies are modulated with radio carrier waves...
ComplexWave.jpg
 
Top