• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Bypassing passive crossover - phase question

S

singzh

Active Member
Hi guys,

It has a switch on the cabinet for bi-amp, and bypassing part of the internal crossover network (mainly LF and MF).

Since this is a 2nd order crossover design, it will shift the phase by 180 degree on the woofer. When flip to bi-amp mode, there is no phase shift on the woofer. My question is, in bi-amp mode, do I need to change the polarity of the woofer to match the original phase?


Thanks,
 
Last edited:
Register to hide this ad
Here's The Owner's Manual, it doesn't mention reversing polarity. I think it's the same thing that was throwing you off in your previous post about this crossover, the whole red/black/+/- situation. I seriously doubt any manufacturer would design a system with a bi-amp switch that, if used, would necessitate re-wiring the components.

ETA: It does mention that to actually bi-amp the speakers with the straps removed and switch flipped, you need the DX-1 active crossover unit. Those are really rare and hard to come by. So if you don't have one of those, you'd be on your own to set up the drive curves of a different active unit. And that might be a chore if you don't have the tools handy.
 
Last edited:
singzh said:
Is it possible that polarity really does not matter?
Click to expand...

Polarity does matter, it's just that the designers have already taken it into account when they designed the crossover. You will just have to trust them that they knew what they were doing, and that maybe they understand the crossover they designed better than you and I do. If nothing else, please take a look at figures 1, 2, and 3 on pages 4 and 5 of the owner's manual I posted a link to earlier. Notice how, in every instance, both + and - of the amps and the speaker connections are called out. Also note how no mention is made of cracking the speaker open and reversing any polarities on any of the drivers. Hopefully these steps might help assuage any concerns you might have about how the designers intended their product to be operated in the three different modes of operation.
 
Last edited:
Some JBL woofers are marked with the pos black and the neg. red on purpose. Haven't seen this convention anywhere else.
 
Hi Jeffery,

Thanks for the detailed info.
I am reading the manual trying to understand if I need to reverse the polarity of the woofer when switching to "Bi-amp" mode
Regards,
 
Last edited:
singzh said:
Hi Jeffery,

Thanks for the detailed info.
I am reading the manual trying to understand if I need to reverse the polarity of the woofer when switching to "Bi-amp" mode without DX-1 (I am using an Ashly XR1000)


Regards,
Click to expand...

I've never claimed to be a crossover designer, but it's my understanding that on 12dB/oct crossovers, it's the relative polarity between the woofer and the the next higher driver that's reversed. The woofer doesn't reverse polarity, it is what it is. The 180 degree phase shift of the crossover dictates what the polarity of the mid would be, but again, I cannot fathom a reason why any speaker designer would create a system where it's up to the user to take the speaker apart and go to swapping wires on the drivers to accomplish something that JBL has already accomplished in numerous designs before the XPL-200, namely the ability to bi-amp the speaker.

While I cannot be 100% certain, I can almost guarantee that JBL never intended the end user to swap the wires on the drivers to facilitate bi-amping the XPL-200 speaker system.
 
I believe that when you use the switches ,You do not have to do anything manualy it changes polarity automaticly.like when you use a subwoofer out of phase one terminal opens and the other closes to do this automaticly.I take it you want to use the ashley,wel just use the bypass and use it and enjoy it.
 
Jeffery said:
I've never claimed to be a crossover designer, but it's my understanding that on 12dB/oct crossovers, it's the relative polarity between the woofer and the the next higher driver that's reversed. The woofer doesn't reverse polarity, it is what it is. The 180 degree phase shift of the crossover dictates what the polarity of the mid would be, but again, I cannot fathom a reason why any speaker designer would create a system where it's up to the user to take the speaker apart and go to swapping wires on the drivers to accomplish something that JBL has already accomplished in numerous designs before the XPL-200, namely the ability to bi-amp the speaker.

While I cannot be 100% certain, I can almost guarantee that JBL never intended the end user to swap the wires on the drivers to facilitate bi-amping the XPL-200 speaker system.
Click to expand...

Agreed ,If that were so there would be jumpers available on the outside of the speaker.it is all automatic done with internal open/close switches.

if You are still uncertain Call JBL the number is on the manual.
 
Hi... I've looked briefly at the circuit. The way it's done, it is hard to know the phase definitively, short of typing all the nodes and components into a simulator. These kinds of crossovers, in fact, crossovers in general, rarely show text book phase shifts due, in part, to the response and impedance of the driver. And, remember, the external filter has its own set of phase relationships which, for similar response to the passive crossover, should mimic its phase behavior.

OK, so if I had to guess, I would say no, don't change the phase going biamp. If your ears tell you different... so be it.

-k
 
Last edited:
I'm very happy you got you tweeter working!

I think you should leave L3 in for now.

On the XPL200A, the switch puts in a much bigger capacitor, as you realize. This bigger capacitor is now out of the crossover circuit almost completely. However, it still protects the mid-range from DC, etc., in case they are hooked up wrong. You could leave it in, or take it out, if you are not worried about that. Either way, the sound should be about the same.

-k
 
Jeffery said:
ETA: It does mention that to actually bi-amp the speakers with the straps removed and switch flipped, you need the DX-1 active crossover unit. Those are really rare and hard to come by. So if you don't have one of those, you'd be on your own to set up the drive curves of a different active unit. And that might be a chore if you don't have the tools handy.
Click to expand...

For this particular speaker the DX-1 doesn't seem to have much magic. We can look at the cards for the xpl-200. There is just enough components (two caps per signal) to make a 12dB slope for the high pass and same for low pass. There isn't enough components to do anything else. It appears that there are polystyrene bypass capacitors. Note that they are only on the HP card.

Hopefully this puts the mind at ease. No need to chase that rare thing and it is rare. It does have the fancy diode biasing in the buffer stages however.:scratch2:

I believe the ashly is L-R 24dB slopes which will work. The L-R 24dB filters are in phase and the 12dB butterworth filters are 180 deg. from each other. It seems that this would warrant trying out the woofer phase.

xpl 200 cards
 
You must log in or register to reply here.
Back
Top Bottom