When I use the second order passive crossover, the polarity of tweeter is inversed to keep the sonic in phase.Anyway, do I also need to inverse the polarity of the tweeter when I use the second order electronics crossover?
Besides, does the polarity is need to change with different slopes (18, 24db/octave, etc.)
Thanks!
In theory, yes, assuming it is separately crossed. You want to attempt to have all drivers operating in phase.Originally Posted by smartpolo
Not with 24dB, which yields 360° phase shift, i.e., back home again.
18dB, I don't know what to do with. If you invert it, it'll behave like 6 dB with respect to phase, I suppose; either case can result in lobing and tilting of the coverage pattern. Whatever sounds best, maybe.
Phase response also varies with the mechanical alignment of the drivers.
What's the manual say?
That is not necessarily so.
All drivers operating in the same band-pass should definately be in-phase. That is, all LF's the same, all MF's the same, etc.
However, it is relatively common in 3-ways that the MF is out-of-phase with the LF and HF. And in two-ways, the HF is most commonly out-of-phase with the LF. The cancellation in the crossover area(s) can improve imaging. Depends on the slopes, and the sound you like.
bo
"Indeed, not!!"
Hi Boputnam, so you mean there is no need to reverse the polarity of tweeter when using second order electronic crossover. Now I 'm confusing, why I need to reverse the polarity to get the stage when using passive 2nd order crossover?
Yea, or, No.
Try it both ways - there will be an acoustic difference. There is really no "right" or "wrong". The only areas of the frequency spectrum that are impacted are in the zone of crossover. Outside of that, the tweet will be operating in a frequency range without any chance of cancellation.
There are subtle differences in each approach. It's much like what Zilch was saying. Drivers working out-of-phase with moderate crossover slopes can sound much like divers running in-phase using very steep crossover slopes. Do some listening. It is quite subjective, unless you are trying to replicate someone else's engineering - then you should follow their design.
bo
"Indeed, not!!"
So sayeth the JBL 5235 Electronic Crossover operating manual...."Note: If the crossover point lies above 2 kHz, reversing the polarity of the high frequency driver will create little (if any) perceptible difference in system performance. The "correct" polarity in such a case will be that which yields the most natural quality with a variety of program material."
Anyway, my crossover point is 500Hz, I think the polarity is important.
bo
"Indeed, not!!"
At lower frequencies I believe connecting drivers with opposite polarites is done to reverse the effects of phase change in the crossovers. That is, it puts the drivers back in phase. The original version of Drew Daniels' system is a good example.
David
An excellent set of articles:When I use the second order passive crossover, the polarity of tweeter is inversed to keep the sonic in phase.Anyway, do I also need to inverse the polarity of the tweeter when I use the second order electronics crossover?
Besides, does the polarity is need to change with different slopes (18, 24db/octave, etc.)
Thanks!
http://sound.westhost.com/articles.htm
"Anyway, my crossover point is 500Hz, I think the polarity is important."
Yes at 500Hz it sure is. Do you have an RTA?? What you can do is set up the system in phase with a 12db network and set-up to get the deepest null on the display when you have as much cancelation as you can get reverse phase. At 500 Hz it going to be very obvious which is correct as the null will be plainly vissible.
1 pole network is 90 degrees 6db Try Both
2 pole network is 180 degrees 12db network Typically change phase
3 pole network is 270 degrees 18db Try Both
4 pole network is 360 degrees 24db Typically same phase with delay
Rob
"Note: If the crossover point lies above 2 kHz, reversing the polarity of the high frequency driver will create little (if any) perceptible difference in system performance. The "correct" polarity in such a case will be that which yields the most natural quality with a variety of program material."
Hello Zilch
Yes you should go with sounds best however you can see destructive cancellation right in the 1-2K region easilly with your RTA. Most pa cabinets with driver spacing and horn lenghts I can understand why they say that but with close driver spacing and direct drivers I would definitely take a look at what's going on with an RTA as an example and watch for any nulls.
Rob
That may be in that example.
However, on many I have measured at the cone output(s) using the Galaxy "Cricket" the MF is often out-of-phase with the LF. Thus, my posts, above. It's handy to actually measure what is going on, but then to let your ears decide...
http://www.galaxyaudio.com/CRICKET.html
Get 'em here: http://www.northernsound.net/Sales/t...o/cricket.html
bo
"Indeed, not!!"
Thank you Ian, just what I was looking for.
Yup.
'specially the one on Phase, Time and Distortion in Loudspeakers with the section on Phase Audibility.
http://sound.westhost.com/ptd.htm
That website has long provided good stuff.
bo
"Indeed, not!!"
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