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Thread: All Pass

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    All Pass

    This seems to be a factory allpass, I think it is messing with my time alignment. Is it an all pass? Every time I try to remove it by say by putting in an allpass 2nd order at around 315 on one of the channels, it seems to shunt the dip down the frequencies. Is there more going on?

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    Noob Jdunk54nl's Avatar
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    Re: All Pass

    Can you post a screenshot of no input eq but +Front L and +Front R. The first image is +Front L and -Front R. Then the second one has an allpass, but we have no reference to what it was before to see if that actually fixes anything.
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

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    Re: All Pass

    For some reason I cant repeat my advanced ISA results, not sure if its the computer or the cheap usb dongle I am using.

    However I have repeated the same results with the simple input analyser. Blue and red lines are front left and right on their own. The green line is when they are summed and the yellow line is when they are summed but one of them has the polarity flipped. Am I correct in assuming factory all pass between 315 - 400 Hz? When I tried an all pass on one input channel around 360 it flattened it when summed but pushed the dip lower down the frequency range. The slopes of the all pass do not seem to be symetrical, one is steeper when viewed inverted. My attempt to fix is not shown.

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    Noob Jdunk54nl's Avatar
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    Re: All Pass

    If you are using the advanced method, just send that signal into rew or Jl tun. Don’t use the helix stuff. Not fast enough nor high enough resoltuion.
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

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    Re: All Pass

    How do I do it using rew, is it just a case of hooking up as I would with the Helix dsp tool and set the helix software to measurement mode and then selecting the usb interface as input device in rew preferences > rta > record button and start playing pink noise?

    Are there any other specific settings I need to change in rew?

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    Re: All Pass

    Red and blue are l & r , the green with the dip is them summed, the green peak is them summed and a polarity flipped.

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    Noob Jdunk54nl's Avatar
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    Re: All Pass

    So now that you got rew going, do a sweep and get the phase of each channel. Then you’ll have phase info and can look directly at what’s going on there.
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

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    Noob Jdunk54nl's Avatar
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    Re: All Pass

    Or use open sound meter and look at phase in real time in a much easier to see way.
    2014 F150 Limited -> Kenwood DDX-9907xr -> Helix DSP.2 -> Alpine PDX-V9 -> SI M25 mki in Valicar Stuttgart Pods, Rear SB17's, Sub SI BM MKV's in MTI BOX. Alpine PDX-F6 -> SI Tm65 mkIV, SI M3 mkI in Valicar Stuttgart Pods

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