paralleling voice coils

Opie · 15th November 2002, 01:13 PM

Hello,
I have found a sub in my basement collection with dual voice coils. What is the effect on spl when the voice coils are put in parallel as opposed to series?

thanks,

Opie

AndrewJ · 15th November 2002, 01:41 PM

Opie, the efficiency of the driver will be unchanged with either connection, but the sensitivity will be different.
Suppose each coil is four ohms, and driven from a voltage source providing 2volts. With the coils in parallel, each will draw a current of 2/4=0.5 amps. If the product of flux density and coil length (Bl) is say 5 for each coil, then the force produced is F=Bli x2= 2.5 x 2 =5
Now wire them in series. Each will now only have 1volt across the coil, so the current in each coil is now only 1/4=0.25 amps. The total force is now 5 x .25 x 2 = 2.5.
The force on the cone is now one half that of the parallel connection, so the output is 6dB down, though the impedance is 8ohms rather than 2ohms.

Andrew

15th November 2002, 01:13 PM	#1
Opie diyAudio Member Join Date: Oct 2001 Location: UW Stevens Point Campus	paralleling voice coils Hello, I have found a sub in my basement collection with dual voice coils. What is the effect on spl when the voice coils are put in parallel as opposed to series? thanks, Opie

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15th November 2002, 01:41 PM	#2
AndrewJ diyAudio Member Join Date: Sep 2001	Opie, the efficiency of the driver will be unchanged with either connection, but the sensitivity will be different. Suppose each coil is four ohms, and driven from a voltage source providing 2volts. With the coils in parallel, each will draw a current of 2/4=0.5 amps. If the product of flux density and coil length (Bl) is say 5 for each coil, then the force produced is F=Bli x2= 2.5 x 2 =5 Now wire them in series. Each will now only have 1volt across the coil, so the current in each coil is now only 1/4=0.25 amps. The total force is now 5 x .25 x 2 = 2.5. The force on the cone is now one half that of the parallel connection, so the output is 6dB down, though the impedance is 8ohms rather than 2ohms. Andrew

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