When is it right to reverse phase/polarity?

[grumpy]

I still wouldn't be terribly surprised if there was a goof in the documentation.

I don't have enough gumption to tear into my in-regular-use L100T pair which are very similar.

[pathfindermwd]

You are right. I shouldn't have bothered.

David, I humbly apologize for my rude behavior towards you.

[pathfindermwd]

Why can't we be friends, Why can't we be freinds, sang to Why can't we be friends.

What, no dance?

If you are in passive bi-amp mode why would you reverse the polarity on the woofer? You have not changed the woofers phase relationship with the other drivers. You most likely end up with a hole through the crossover region between the 2214 and the 104.

If you look at the L100T3 schematic they have all the drivers with the acoustic phase with a + Positive voltage to the red terminal all drivers move forward. If you look closely at the wiring the woofer is wired with the polarity reversed relative the mid and tweeter.

Rob

I noticed the polarity notation the other day.

My questions reveals several areas of weakness in my understanding...

Um, the initial reason for my query was brought about by a suggestion that I try reversing the polarity of the midrange. This was suggested as something I could try to contour the sound to my liking, not as an improvement as such. I tried it and didn't like it. This didn't really surprise me since these speakers came to me with their tweeters wired in backwards, they even went through all the trouble of soldering the posts in reverse. It was only because I had two sets (L100T/L100S) that I became aware of this while poking around inside. This inverted tweeter is actually how I got to buy the L100S since the owner said they didn't sound right, they did sound different..

I realized after trying to invert the mid that I could try to invert the woofer, and since I was in passive bi-amp, it was very simple. This actually didn't sound too horrible. It did seem to cause a "hole" in the midrange, but I can't be certain what the effect is since I read the the summing of the woofer and mid could cause a 3db increase at the XO.
Was I hearing a hole, or the lack of summation? I think it's a hole.

I wondered if the biamped XO offered any solution since it's network is divided. Apparently not.

I'm not too far away from actively bi-amping the speakers. This is all just about understanding better how my system works, and how to improve it. And addressing some long standing issues with the performance.

[DavidF]

David, I humbly apologize for my rude behavior towards you.

Acknowledged and accepted.

[pathfindermwd]

I don't know why someone would do this, but it they think it sounds better, who am I to complain.

To be fair it was suggested as an experiment with no claims for certain improvement. My understanding about it was that sometimes it's a simple design call and that there might be some room for interpretation. My initial question to the forum was posed to get a better understanding of the complexity of it, specific to this speaker design.

The L100t3 schematic both shows electrical 12db/oct type crossovers, as well as non-inversion of any drivers... which may be just
wrong, there may be an acoustic slope involved as well (rotating the phase at crossover even further), or it may just have measured
and sounded better that way. Normally, the mid would have been inverted in this arrangement.

So, you bring up a couple of points I didn't realize. 1. That the schematic doesn't definitively trace the polarity of the signal. 2. It doesn't show the acoustic slope you speak of. 3. The schematic could be wrong.

Normally, you would end up with a cancellation and a "hole" in the frequency response, but as this design might depend
on more than the electronic (passive) crossover to achieve the desired crossover function, the "cancellation" may not be as noticeable.
You may end up just hearing a change in timbre in the crossover area.

It doesn't sound as bad a reversing the mid, to my ears. It sounds attenuated, and the bass is different, sometimes heavier sounding. The sweetness of the sound goes away, so I can't call it an improvement.

I believe there are several (arta, holmimpulse,... but measurement type mics usually also require a power source and a preamp.
I think parts-express has a fairly cheap measurement package.

Thanks!

(a simple, "thanks but let me clarify what I was looking for", could have saved a lot of grief)

Duly noted.




Soon, I'll get the electronic XO hooked up. Would you hazard a opinion on how it would improve performance?
Would it offer me the ability to have a steeper XO, and would that improve phase at the XO between the mid/woofer?