90* out of phase :(

[g.costanza]

My Camry has an awesome jbl factory stereo but the hu and amp are inseparable. Anyway, ALL I WANTED TO DO was add a sub. I installed a sealed 12 and amp. I tapped into the rear woofers for the speaker level signal for the amp. The problem is that with the sub wired up either at 0 or 180* out of phase with the mains, im getting a lot of cancellation between woofers amd sub. The cars woofers have really good deep bass respsonse, which isnt helping. I imagine that they r either 90 or 240* out of phase. There's really no way for me to hi pass the cars woofers passively. They r 2 ohm...Bass blockers would roll off at like 300hz . I AM NOT GOING TO CHANGE THE FACTORY SYSTEM beyond adding the sub. Any ideas on a way to insert a 90* phase shift? What about a stand alone LOC vs the one built into the amp? Any of those have phase adjustments? This isn't a competition system, btw Thanks!!!

[MarkZ]

What kind of crossover options do you have for the subwoofer? Slope? Continuously adjustable crossover point?

Where, exactly, is the sub located in the car?

[chad]

some amplifiers have variable phase. IIRC there is an all pass filter that continuously adjusts phase also.

There is already likely a HPF on everything else, and it likely slides with volume, compounding the issue.

[thehatedguy]

18 dB slope.

Done

[Aaron'z 2.5RS/WRX]

Tap off the front speakers and see if the problem goes away...

[minbari]

Originally Posted by g.costanza

My Camry has an awesome jbl factory stereo but the hu and amp are inseparable. Anyway, ALL I WANTED TO DO was add a sub. I installed a sealed 12 and amp. I tapped into the rear woofers for the speaker level signal for the amp. The problem is that with the sub wired up either at 0 or 180* out of phase with the mains, im getting a lot of cancellation between woofers amd sub. The cars woofers have really good deep bass respsonse, which isnt helping. I imagine that they r either 90 or 240* out of phase. There's really no way for me to hi pass the cars woofers passively. They r 2 ohm...Bass blockers would roll off at like 300hz . I AM NOT GOING TO CHANGE THE FACTORY SYSTEM beyond adding the sub. Any ideas on a way to insert a 90* phase shift? What about a stand alone LOC vs the one built into the amp? Any of those have phase adjustments? This isn't a competition system, btw Thanks!!!

why only 300hz? bass blocker (IE: HPF) can be made to any freq you like. not sure why you want 90° specifially, but a 6db/oct would give you 90°

[chad]

I'm wondering how the 90 degree number was chosen, it sounds more of a bass/midbass integration issue rather than a 90 degree phase issue.

[minbari]

Originally Posted by chad

I'm wondering how the 90 degree number was chosen, it sounds more of a bass/midbass integration issue rather than a 90 degree phase issue.

ya, not a clue. I suspect if he does get his 90°, it will not fix it, but who knows.

[thehatedguy]

x2 to the above 2

[envisionelec]

Originally Posted by g.costanza

My Camry has an awesome jbl factory stereo but the hu and amp are inseparable. Anyway, ALL I WANTED TO DO was add a sub. I installed a sealed 12 and amp. I tapped into the rear woofers for the speaker level signal for the amp. The problem is that with the sub wired up either at 0 or 180* out of phase with the mains, im getting a lot of cancellation between woofers amd sub. The cars woofers have really good deep bass respsonse, which isnt helping. I imagine that they r either 90 or 240* out of phase. There's really no way for me to hi pass the cars woofers passively. They r 2 ohm...Bass blockers would roll off at like 300hz . I AM NOT GOING TO CHANGE THE FACTORY SYSTEM beyond adding the sub. Any ideas on a way to insert a 90* phase shift? What about a stand alone LOC vs the one built into the amp? Any of those have phase adjustments? This isn't a competition system, btw Thanks!!!

A 90° shift is accomplished by using a first order network like a capacitor or inductor. Or using a third order network on one and a second order on the other.
AP (All Pass) filters generally perform the same thing, but only at the crossover frequency.

I've found that the only way to fix this situation is to use time alignment. Related: I used to use a 90° phase shift left to right to move my front stage to the dash - this was well before DSP was affordable. People would always think I had tweeters in the vents (remember those days!?)