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Bass production and membrane area

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Thread Starter #21
Your questions suggest a much more limited scope than the problem you really seem interested in. That problem does not seem to be clearly defined. It sounds like a circle of confusion problem.
In discussing the topic of bass, the thread is invoking other concepts that are distinct from bass alone: motor design, directivity, diaphragm modes, and efficiency. The response of a drum isn't limited to just the output in the bass region; it will have significant harmonics poking into the midrange.
Ok, so let's limit the question only to the bass domain.
 

tomtoo

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#22
Ok, so let's limit the question only to the bass domain.
The most importend is the spl you want to reach. If you like listen to Drums,e-bass, the typical instruments, at low levels a 6" inch could work. If you like to listen at a original kick drum level no way. To get spl the speaker needs to move air. For that you have only two ways membrane area or membrane swing thats physics. Than engineering starts, what mixture of this is the most practical to use?
Just think of the moved air volume is that of a zylinder. Where you have the base area and a high=swing.
 
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solderdude

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#24
You can move a pin 10m but will get little displacement of air volume
You can move a large surface 1mm and get a lot of displacement of air volume
 
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solderdude

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#26
very little its why they can be tensioned.
The swing is also frequency dependent of course.
 

Juhazi

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#27
Area times stroke is basic theory, but air is not solid - so area is more important than stroke because of air compression losses with high stroke. Making high excursion is difficult, there will be mechanical problems with linearity, and net result is lower efficiency and higher distortion, and lower spl limit than expected per simple area x stroke formula.

https://barefacedbass.com/technical-information/Volume-displacement.htm

Test of a good subwoofer here, with some general info hidden in the text https://www.audioholics.com/subwoofer-reviews/jtr-captivator-rs1
 

RayDunzl

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#28
how much do the membranes on a Magneplanar move?
I have to try hard to see my 'stats move. They fade out below the crossover at 180Hz, so, that helps some.

Pound them hard, and reflect a laser pointer off the mylar diaphragm and onto the wall.

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Using a calculator, and pretending a panel is a cone, for a simplistic guesstimation...

12" cone vs 15x48" panel at 50Hz and 90dB:

Woofer

1598332915626.png



Panel

1598332830254.png


http://www.baudline.com/erik/bass/xmaxer.html
 

Wombat

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#29
Just interesting what it is the difference between distance and displacement?
Distance is a measurement of separation of two points. Displacement is a measurement of distance or volume moved wrt loudspeakers.
 
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#30
Side note: while "moving air" usually means the displacement in this context, a loudspeakers job is to pressurize air, not move it.
 

Frank Dernie

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#31
A church organ can go as deep as 16hz and this with a lot of spl. Nothing for toy speakers. Not a good example.
Kick Drums have a lot of energy in the 50Hz region thats more easy.
8“ inch speakers can do 50Hz well. As long as you not want to reproduce the kick at original spl. If you like to reproduce a kick in original spl you are easaly in the region of 18" drivers.
My horn loaded 15 inchers are pretty impressive here.
 

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