How does wiring a dual vc sub affect the qts?

[crazybastard]

I have a pair of dual voice coil subs. Can someone educate me as to how these scenarios affect the qts?

1. parallel
2. series
3. only one vc used

Thanks.

[Dave Bullet]

Apart from obvious impedance options (parallel, series or only one coil), Qes halves regardless of how the voice coils are hooked up (series or parallel).

This description (copied from a Dan Wiggins Shiva subwoofer whitepaper) might help explain.

"But the most important benefit for dual voice coils is flexibility for the T/S parameters. One can actually
“dial in” a desired Qts of the driver, by resistively loading one voice coil and actively driving the other.
This configuration, which we call Resistively Damped Operation (RDO), uses the second (undriven) voice
coil as an electromagnetic brake. In essence, the resistance across the second coil will determine how
strong the brake is. The smaller the resistance, the stronger the brake.
RDO affects the Qts of the driver by decreasing the Qms of the driver. The RDO brake acts to damp cone
motion, as if the suspension was considerably stiffer. However, as it’s an electromagnetic brake, the Fs is
NOT affected (as it would raise if the suspension components – the surround and spider – were stiffened).
This allows one to literally “dial in” in a desired Qts by varying the Qms of the driver. In fact, a 250 W
5W potentiometer can be used to tune Shiva over a large range. For example, placing Shiva in an 80 liter
box, and using the RDO configuration, one can dial in a system Qtc ranging from 0.55 to 1.1. This allows
tailoring the low-end response of the system to meet most musical/home theater reproduction needs."

Voltage sensitivity remains the same whether one coil connected or both in series. Voltage sensitivity increases +6dB when both coils connected in parallel.

[Xander]

Apart from obvious impedance options (parallel, series or only one coil), Qes halves regardless of how the voice coils are hooked up (series or parallel).

This description (copied from a Dan Wiggins Shiva subwoofer whitepaper) might help explain.

"But the most important benefit for dual voice coils is flexibility for the T/S parameters. One can actually
“dial in” a desired Qts of the driver, by resistively loading one voice coil and actively driving the other.
This configuration, which we call Resistively Damped Operation (RDO), uses the second (undriven) voice
coil as an electromagnetic brake. In essence, the resistance across the second coil will determine how
strong the brake is. The smaller the resistance, the stronger the brake.
RDO affects the Qts of the driver by decreasing the Qms of the driver. The RDO brake acts to damp cone
motion, as if the suspension was considerably stiffer. However, as it’s an electromagnetic brake, the Fs is
NOT affected (as it would raise if the suspension components – the surround and spider – were stiffened).
This allows one to literally “dial in” in a desired Qts by varying the Qms of the driver. In fact, a 250 W
5W potentiometer can be used to tune Shiva over a large range. For example, placing Shiva in an 80 liter
box, and using the RDO configuration, one can dial in a system Qtc ranging from 0.55 to 1.1. This allows
tailoring the low-end response of the system to meet most musical/home theater reproduction needs."

Voltage sensitivity remains the same whether one coil connected or both in series. Voltage sensitivity increases +6dB when both coils connected in parallel.

That's really cool, thanks for posting that. It helps to explain a lot. Companies always say how DVC subs are so much more configurable than SVC, and this really shows it in ways that most people don't even think of. Would make for a fun project...

[Dennis H]

Just to clarify what Dave said a bit with an example:

Coils parallel: Qes = .35
Coils series: Qes = .35
1 coil wired, other coil open: Qes = .7
1 coil wired, other coil shorted: Qes = .35
1 coil wired, other coil with a resistor: Qes = somewhere between .35 and .7

In all cases, Qts will be a bit lower than Qes but usually not too much.

[collo]

Here's a bit more info on T/S conversions for DVC drivers

[crazybastard]

Thanks for the answers. I kinda had an idea, now I have a much better understanding.