Mixed order XO's and tweeter polarity

[bkeane1259]

Noobish questions....here goes.

Does the ROF for reversing polarity on the tweeter only hold when it's a 2nd order XO on both the tweeter + woofer? What if you have a 2nd order on the tweet and a higher order on the woofer?

I've seen odd order XO's with reverse polarity tweets....I'm very confused. Is there a consensus?

Thanks....:D

[dthomas]

Noobish questions....here goes.

Does the ROF for reversing polarity on the tweeter only hold when it's a 2nd order XO on both the tweeter + woofer? What if you have a 2nd order on the tweet and a higher order on the woofer?

I've seen odd order XO's with reverse polarity tweets....I'm very confused. Is there a consensus?

Thanks....:D

It does hold true but only if your acoustic slope follows a true 2nd order transfer function. If the acoustic slope is truly 2nd order then you will have to reverse polarity.

Just because your topology looks like a classic third order network does not mean your crossover will have third order acoustic slopes. That all depends on the drivers frequency response and impedance profile. This is the main reason textbook crossovers never work out as expected.

[Chris Roemer]

Noobish questions....here goes.

Does the ROF for reversing polarity on the tweeter only hold when it's a 2nd order XO on both the tweeter + woofer? What if you have a 2nd order on the tweet and a higher order on the woofer?

I've seen odd order XO's with reverse polarity tweets....I'm very confused. Is there a consensus?

Thanks....:D

Not cut and dried.

As elements are added to any pass filter (raising its order), the phase rotates a little farther each time. If I've got a filter pair that rolls two drivers into each other well (w/OUT looking at the summing yet), THEN look at their phase, it they're out by 180*, I'll reverse the tweeter.

It's said that "odd order" rolloffs (by definition?) are not in phase, but are 90* o-o-p (known as "quadrature"). In those cases, you can leave them as is (reversing the tweeter polarity leaves them still 90* out, but throws the lobe the other way - up or down), OR add another element to either (or both) filter(s) to adjust the phase alignment to whatever you're shooting for.

Chris