[sdiy] inductors, B fields, and confusion

[Scott E.]

Don,

Thanks for this explanation. As an additional question on this scenario, 
what would the effect the two driver setups would have on the damping 
ability of the amplifier driving the loads? As I recall, the damping 
factor of an amp related to the amp's output impedance and the load 
impedance. Although the 16 ohm driver in parallel and the 4 ohm drivers 
in series present the "same" 8 ohm load to the amp, I cant help but 
think that the damping of the parallel drivers should be better as well. 
Can you confirm this or explain otherwise?

Thanks, Scott Evans
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Don Tillman wrote:
>    > Does this mean that the 16 ohm speakers would be louder or am I 
>    > skipping something?  Is there some sort of physical saturation point 
>    > that I'm ignoring? 
> 
> I believe so.
> 
> The bible on this is the original Neville Thiele article
> "Loudspeakers in Vented Boxes", parts 1 and 2.  Also the Richard
> Small articles.  These are nicely reprinted in the Loudspeakers
> Anthologies available from the Journal of the Audio Engineering
> Society.  
> 
> (I haven't looked at these for a while, so it's entirely possible I'm
> missing something here.)
> 
> Thiele states that the efficiency of a speaker is:
>   eff = (rho/4 pi c) (B^2 l^2 Sd^2 / Re Mm^2)
> 
> (details in the article)
> 
> The interesting parts here are Re, the dc resistance of the voice
> coil, and l, the length of wire in the magnetic field.  The 16 ohm
> speakers will be louder because they have some many more windings in
> the magnetic field.
> 
>   -- Don
> 

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