How a Speaker Works

solacedagony · Post by **solacedagony** » Thu Mar 09, 2006 5:19 am

Yea that does help immensely.
So "the gap" is the itty bitty section between the permanent magnet and the pole piece. And the voice coil is sitting in there.
I ordered the Loudspeaker Cookbook, so hopefully there'll be even more information in there!
I learned so much about speakers and magnets in the past couple days, my brain is just flowing with information! haha

Post by **GlassWolf** » Thu Mar 09, 2006 6:39 am

geo, that large diagram is actually just a "speaker" and not so much a "sub" so if you think of it that way, it explains the large pole vent a bit better. Think or it more like a small midrange.

That memphis one I just posted because I see those silly things more and more, with the double spiders etc..

geolemon · Post by **geolemon** » Thu Mar 09, 2006 8:02 pm

solacedagony wrote: I ordered the Loudspeaker Cookbook, so hopefully there'll be even more information in there!

The cookbook IS an invaluable source of information...
...but for this project, you may be disappointed.

Vance focuses on enclosure and crossover design - in quite some depth, providing formulas that you'll possibly never use (in light of great software that makes hand-cranking numbers obsolete, like WinISD which is free).
He doesn't so much touch on actual loudspeaker DRIVER design as much -although he does walk through how to hand-measure speaker parameters... much of it does help you understand what certain motor parts do, but for a novice it's likely confusing, because it really does completely leap past the "basic architecture of a speaker", and even leaps past the particular part of the speaker being measured quite often.

The "loudspeaker design cookbook" focuses on how to design "loudspeakers" - the term refers to a complete system - a working loudspeaker involves a speaker cabinet of a particular design and construction, a crossover network, possibly more signal processing, and of course - a speaker that goes in the cabinet.

What you are looking for with this paper, as I understand it, is more related to speaker DRIVER design, right?

Don't cancel that order of the LSDC... it's a tremendous value, an incredible source of information - and I'm sure would lend your paper something, worst case.... but as an enthusiast, it describes for you the pros and cons of different types of enclosures (and the majority of the book of course telling you how to design them), different types of crossovers (ever wonder what the difference between a Butterworth, or Linkwitz/Riley crossover slope was, and what the tradeoffs, the pros and cons of each - the "why do I even care?" aspect of things? The book has it.

geolemon · Post by **geolemon** » Thu Mar 09, 2006 8:04 pm

GlassWolf wrote:geo, that large diagram is actually just a "speaker" and not so much a "sub" so if you think of it that way, it explains the large pole vent a bit better. Think or it more like a small midrange.
That memphis one I just posted because I see those silly things more and more, with the double spiders etc..

I'm not criticizing - I think it's huge that you would take the time to find and post those images!

I've looked up cutaways in the past, and was surprised at how much trouble I've had.

I think the links you posted he can print out and use directly in his paper! That's awesome.

Jonathan · Post by **Jonathan** » Thu Mar 09, 2006 8:48 pm

I'm just wondering how detailed he should worry about getting. I think with the great minds on this forum, we can combine and give some killer info on the operation of a speaker, the design, but it's just a question of how in-depth he really wants to get.

geolemon · Post by **geolemon** » Thu Mar 09, 2006 9:02 pm

solacedagony wrote:Yea that does help immensely.
So "the gap" is the itty bitty section between the permanent magnet and the pole piece. And the voice coil is sitting in there.
I ordered the Loudspeaker Cookbook, so hopefully there'll be even more information in there!

Just to clarify...
"The gap" is the itty bitty section between the top plate and the pole piece - that's what the voice coil is suspended between.

The reason the top plate is magnetically charged is because of the magnet.
The reason the pole piece (and back plate!) is magnetically charged is because of the magnet.

Post by **GlassWolf** » Fri Mar 10, 2006 5:53 am

the gap is important (just to tie this together) because when the speaker is at near-limits of excursion, the coil can leave that magnetic gap without actually reaching Xmech (and thereby shredding itself or reaching mechanical limits.) When this does ocur (depending on speaker design.. XBL^2 limits this moreso than a typical overhung motor) the driver uses considerably more power with less control over the moving mass of the driver (if I recall correctly. I know amplifier design better than driver design details.)

solacedagony · Post by **solacedagony** » Fri Mar 10, 2006 7:10 am

Actually, this paper is more specifically aimed at how the speaker actually works, what makes it tick, but I'm also adding basic detail on some history of speakers that I found, and also hearing and soundwaves incase the common person didn't know how those worked. I also want to add a little bit on top of that about how enclosures affect them.

solacedagony · Post by **solacedagony** » Fri Mar 10, 2006 7:15 am

Yea I wanted that book anyway, after I saw the contents of it.

geolemon · Post by **geolemon** » Fri Mar 10, 2006 7:26 am

solacedagony wrote:Actually, this paper is more specifically aimed at how the speaker actually works, what makes it tick, but I'm also adding basic detail on some history of speakers that I found, and also hearing and soundwaves incase the common person didn't know how those worked. I also want to add a little bit on top of that about how enclosures affect them.

Since you are going to be speaking in terms of "converting an electrical signal into sound energy" in discussing how a speaker works - you might make an analogy of the ear, compared to a microphone.

Why?

You can make the point that any electrical motor operated in reverse becomes an electrical generator...
...and therefore, make the point that a speaker is also a microphone.

Both have a diaphragm that vibrates when the sound pressure energy in the air stimulates it, and convert the sound energy into an electrical signal.

The ear doesn't have a coil of wire or a magnetic field - it uses it's own means - but the analogy is there.

And most often, microphones use other, more efficient, more broad-band technologies than a voice coil motor... but that's more akin to the laundry-list of alternative speaker technologies that exist out there as well - many ways to make a microphone, but this certainly is one.

If you operated a speaker "in reverse", by hooking it's terminals up to a recording device, you'd see that you could make a recording.

The sound energy stimulates the cone into motion, and the coil of wire begins moving in the magnetic field - generating electricity, with a waveform that emulates the motion of the cone - emulates the sound striking the cone.

Cool, no?

Of course, a speaker is designed for high excursion, to produce sound...
Sound energy wouldn't stimulate a cone to high excursion levels - so a microphone motor would be tweaked to be more efficient within the ultra-low excursion levels it would be encountering - and a mic like this would need a pretty big diaphragm, and an "enclosure" just like a speaker - but you can make an analogy in your paper!

I think it would be particularly appropriate in the scope of a paper - it shows a true understanding of the mechanics and mechanism you are trying to explain, and alternatives this mechanism is used for.