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Stronger motor makes higher sensitivity?


Pete-FIN
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Hello! My first post here:)
(I asked these questions on a headphoneforum, but didnt get much help, so hopefully you guys can help me.)
 

 

 

 

I have a few questions related to speaker voice coil and magnet. 


I have been told that speaker sensitivity is mostly determined by how "strong motor" the voice coil and magnet together are. Some other aspects also affect speaker sensitivity (like weight of the moving mass), but the biggest factor to sensitivity is the strength of the motor. At Least, this is what I have been told by hifi enthusiasts, I don't have education on this subject, so please, feel free to correct the previous statement if needed.


Here are my questions:


*Can someone please edcate me on the differences of voice coils and magnets (meaby by comparing different kind voicecoils and different kind magnets)?
*What are the very basics when calculating voice coil and magnet related properties (focusing on those calculations that help me understand the strength of the motor and sensitivity of the speaker)?
*Is there a "gain and lose thing" when thinking the strength of the motor (for example, would making stronger motor possibly effects negatively to some other measurable aspect)?


Right now, all I know about voice coils is the basic working principle, and, the more rounds around the voice coil the bigger the resistance for an amplifier.


In your answers, I would be very happy if you could go into very detailed answers about speakers individual parts and how they interact with each other. Outer dimensions, shape, mass, width of gap for coil, material composition, and magnetic properties are some of the factors I'm assuming play a role in making "a powerful motor", and I would be very happy to know more about this complicated subject.


If you have in your browser's bookmarks some good and educational web links related to the topic, please share those too.


if you choose to participate in the debate or answer my questions, I would really appreciate it.
 

 

 

 

PS. I found some interesting web pages related to this.


https://www.prosoundweb.com/channels/av/use_the_force-_inside_moving_coil_loudspeaker_motors1/
Here is a good article about speaker voice coils. The idea of trade-offs, related to different speaker motor designs, is explained quite well.


http://techtalk.parts-express.com/f...s-regarding-magnetic-field-pole-piece-gap-etc
Here is some interesting discussion about focusing magnetic field in the voice coil gap. Quote: "...based on this principle of focusing the magnetic energy into this one small area, with the lines of flux perpendicular to the direction of the cone movement. This tightly focused magnetic field with many lines of flux give the speaker coil something to push against."


I am still wondering, how to design a woofer that gives a good result in the sensitivity area of speaker operation. I'm sure the strength of the magnetic field in the gap is essential, but there must also be other areas of the speaker motor design that effect the sensitivity. I can only guess these other areas, so proper knowledge would be highly appreciated.


Feel free to join the conversation if you have something to share related to the topic.

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There's a BBC Research Department white paper from '79 called "Design of the high-level studio monitoring loudspeaker type LS 5/8" (C.D.Mathers, M.Sc., M.I.E.E) which may provide some useful though somewhat superficial information (page 1 - 3. Drive Units):

 

http://downloads.bbc.co.uk/rd/pubs/reports/1979-22.pdf

 

P.S.: decided for a different paper

"Science draws the wave, poetry fills it with water" Teixeira de Pascoaes

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The most sensitive speakers I know of are the biggies like the Klipschorn, Altec etc. "voice of the theater", Cerwin-Vegas, etc.  Generally, as they get smaller and still try for an extended bandwidth, the sensitivity goes down.  If the impedance (worst-case impedance, not nominal imoedance) goes down as well, then you need to make sure your amp can handle it with low distortion and without overheating.

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