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Re: unity gain Sallen-Key low pass filter designs
Posted: Fri Feb 07, 2014 4:06 pm
by mediatechnology
I remember Russ Berger seeing a similar response from some SOTA monitors that had been installed in the 80's at Tele-Image in Dallas.
One driver had the wrong polarity in both the left and right monitors.
They had been QC'd that way by SOTA.
It had the exact same bump.
Re: unity gain Sallen-Key low pass filter designs
Posted: Sat Feb 08, 2014 9:51 am
by emrr
I don't pay attention to speaker world all that much. From memory, isn't it typically tweeters that get wired opposite polarity?
Re: unity gain Sallen-Key low pass filter designs
Posted: Sat Feb 08, 2014 10:38 am
by mediatechnology
This particular speaker was a 5 way with active crossover.
One of the mid-range drivers had mis-wired polarity on both sides smack in the vocal range.
Dunno if they changed the standard but JBL woofers forever made positive voltage on the red connection suck the driver in.
I suppose that goes back to the old conventional current flow vs. electron flow definitions.
I had mine out lately for a re-foam and should have checked them.
Re: unity gain Sallen-Key low pass filter designs
Posted: Sat Feb 08, 2014 12:16 pm
by JR.
emrr wrote:I don't pay attention to speaker world all that much. From memory, isn't it typically tweeters that get wired opposite polarity?
There actually is no standard convention wrt when to flip driver polarity. Historically is used to be done for early 2 pole crossovers to prevent cancellation at the crossover point, but later 3 pole crossovers did not cancel in either polarity, and even later the 4 pole crossovers rotated all the way back to in phase again.
Yes, JBL drivers historically zigged, while everybody else in the industry zagged.
For real speakers in the real world YMMV... Modern DSP based crossovers offer a whole new range of tweaks.
JR