[milosz]

With a pair of GR SW-12-08 facing forward in my H-Frame I see the wiring diagram shows to wire the drive coils in parallel to my HX410PEQ-OB amp, and the sensing coils in series.

Wouldn't using the servo system in this way average the correction feedback from the two drivers?  Seems to me you'd want to use a separate amp for each driver, so each driver's sensing coil would provide feedback to correct that drivers' specific behavior.

I suppose if GR SW-12-08 driver manufacturing QC is kept very tight then both drivers will behave very nearly in identical fashion, so using a combined feedback signal from series-connected sensing coils should involve minimal performance compromises compared to a separate servo amp for each driver configuration.

I am having a hard time understanding how combining the output of the sensing coils corrects the individual behavior of each driver.  Can someone fill me in on this?

Thanks

[Hobbsmeerkat]

The OB subs are 16 Ohm drivers, so driving them in parallel, cuts the load on the amp to a more reasonable 8 Ohm.

The sensing circuit is run in series because each driver is only doing half the work, a sensor would see this as a single driver only working half as hard as it should, and the amp will boost the output dramatically to compensate.

Running them in series allows the sensor to perceive both drivers as a single output. Tolerances should be tight enough to not be an issue, and will be automatically compensated for across both drivers.

Running multiple amps on a single tower, while possible, is kind of wasteful, esp when the 16 Ohm drivers are designed for OB use, and the 8 Ohm units are intended for Sealed/Ported cabinets.

[Captainhemo]

No,  the   SW12 04 's are for sealed use in a single driver configureation.
IIRC, the   idea behind the 8 ohm  version of the drivers  was so  folks  could   get the most out of the  A370PEQ with a  2 driver tower... that being said,  we have never "run out of gas" with the  A370PEQ  while   using  a pair of the SW12 16FR's in a dual  OB h-frame.
 When using the  8 ohm version,  there is the   possibility of  over driving the  2  woofers with max power of the  A370 only being spread out over  2 woofers

jay

[milosz]

Communicating with Rhythmik they told me to order two SW12-08 and one HX410PEQ-OB amplifier per OB frame:

"Hi Bill,
 
I understand your confusion.  The only version of SW12-08 is for OB and therefore I drop the FR. But they are for OB for sure.

-Brian"

The answer to my question about the sensing connections is "The sensing circuit is run in series because each driver is only doing half the work, a sensor would see this as a single driver only working half as hard as it should, and the amp will boost the output dramatically to compensate.

Running them in series allows the sensor to perceive both drivers as a single output. Tolerances should be tight enough to not be an issue, and will be automatically compensated for across both drivers." 

So the assumption is that both drivers will be so similar that any misbehavior requiring servo correction will be identical between the two drivers so summing the sensing coils works.  OK, I can accept that.

OB frames in process