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Thread: How-To: Verify Phase Cohesion Through A Crossover

  1. Back To Top    #11
    Noob Jdunk54nl's Avatar
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    Re: How-To: Verify Phase Cohesion Through A Crossover

    You can always check your distance measurements, but if they are close, then you should be good. If you have a ford with easy entry/exit (where your seat moves backwards when key is removed and forwards when it is placed in the ignition) make sure your keys are in the ignition prior to measuring. I messed that up a couple times and had bad measurements.

    If the distance measurements are good, get a 9v battery (or any battery but 9v makes it easy to see) and test the speakers for polarity. Hook the positive side that goes to the speaker to positive on battery, and negative to negative. This should make the speaker move out (reverse the connection and it moves in), all speakers should either move out, or all should move in (doesn't matter as long as they all move the same way). If a set moves opposite, you have them wired wrong.

    If you can't do this, there are some apps for polarity testers, but they aren't quite as good, but work for speakers you can't see easily. I still prefer doing the 9v and using a flashlight to look through the grills to make sure, but that does require a second set of hands to connect the battery for most people.

    Not that any of this really matters if you do have them summing correctly.
    Last edited by Jdunk54nl; 05-15-2020 at 10:33 AM.
    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

  2. Back To Top    #12
    Noob Cathul's Avatar
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    Re: How-To: Verify Phase Cohesion Through A Crossover

    I have a Mustang, so no easy entry in that car. Measurements were done with the new headunit. And this was the only thing that changed.
    Did some tunes in the past with SYNC3, but never had to flip polarity on any driver with 24db slopes. This was a first for me and i still think i made something wrong.
    Thinking about doing it again scares me a bit as my wife really dislikes me sitting in the car and waving the mic around my head.
    And as we all know... happy wife, happy life, but the opposite of a happy wife... well...
    SYNC3 headunit
    Mosconi Pico 8/10 DSP
    Mosconi D2 500.1
    Gladen Zero Pro 165.3 DC
    JL Audio 10w3v3 in custom enclosure (Blueprint by Mark @Caraudiofabrication)

  3. Back To Top    #13

    Re: How-To: Verify Phase Cohesion Through A Crossover

    Quote Originally Posted by jtrosky View Post
    Stupid question.... Lets say that you have a phase-induced dip (whether at the crossover or elsewhere). Is there a difference between fixing the issue with an allpass filter vs fixing the issue with EQ (assuming the end result is the same in terms of freq response)?

    I'm still trying to understand and learn how to utilize allpass filters properly.

    If a processor didn't have the ability to use allpass filters, is addressing the issue via EQ "appropriate"?

    Also - how to decide when to use a first order or secord order allpass filter?

    Thank you!
    Yes, there is a difference between using an all pass filter vs attempting to fix the issue with EQ. A dip caused by a phase cancellation causes a loss in amplitude (which is what you're measuring), but it also effects our localization of those cancelled frequencies. Let's say you have a wide phase related dip at 500Hz when you measure two speakers. If you listen to content centered around 500hz, you will likely hear it as two distinct copies coming from each speaker, rather than a single, coherent center image. Or, the center image will be awfully diffused and unfocused. Our brains treat "out of phase" frequencies this way because of their mismatch in time (since phase is directly related to time). Fixing the phase issue with an all pass filter may fix both the lost magnitude and our localization of the sound. You also need to ask why there is a phase mismatch in the first place (something I'm trying to figure out). Attempting to fix a phase induced dip with EQ will cause more distortion from wasted power and still fail to fix the localization problem. You have to be careful with using all pass filters, though. They aren't a band-aid for phase issues that should be used whenever you see a dip. Just my experience.

  4. Back To Top    #14
    DIYMA Janitor SkizeR's Avatar
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    Re: How-To: Verify Phase Cohesion Through A Crossover

    Quote Originally Posted by Justin Zazzi View Post
    I've been wanting to make a video like this for ages. This is exactly what I've been jumping up and down about for years. Bravo man, very well done. Thank you for fighting the good fight.

    I didn't think about using the overall target curve and then using the EQ module in REW to set the crossover points. That's pretty clever and avoids loading and reloading the target curves for each driver. I might have to adjust the instructions on the tuning companion spreadsheet.

    I moved the tool over here to continue supporting it.
    Now you all can have the "half-whitledge" target curve too!

    https://www.caraudiojunkies.com/show...0209#post60209
    Thanks Justin! Gunna have to add the Apicella curve for those who, like me, pretty much purely listen to death metal and needs something a bit different

    Sent from my SM-G975U using Tapatalk

  5. Back To Top    #15

    Re: How-To: Verify Phase Cohesion Through A Crossover

    Quote Originally Posted by SkizeR View Post
    Thanks Justin! Gunna have to add the Apicella curve for those who, like me, pretty much purely listen to death metal and needs something a bit different

    Sent from my SM-G975U using Tapatalk
    Please do share this..

  6. Back To Top    #16
    Wave Shepherd - aka Jazzi Justin Zazzi's Avatar
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    Re: How-To: Verify Phase Cohesion Through A Crossover

    Quote Originally Posted by SkizeR View Post
    Thanks Justin! Gunna have to add the Apicella curve for those who, like me, pretty much purely listen to death metal and needs something a bit different

    Sent from my SM-G975U using Tapatalk
    Send it over!
    Measure with mics, mark with chalk, cut with torch, grind to fit, sand to finish, paint to match.
    Updated Justin tuning sheet (Justin and Erica tuning companion for SMAART and REW)
    Do it for them.

  7. Back To Top    #17
    Noob Cathul's Avatar
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    Re: How-To: Verify Phase Cohesion Through A Crossover

    Quote Originally Posted by Justin Zazzi View Post
    I didn't think about using the overall target curve and then using the EQ module in REW to set the crossover points. That's pretty clever and avoids loading and reloading the target curves for each driver. I might have to adjust the instructions on the tuning companion spreadsheet.
    That's what i thought, too, but the speaker curves from your spreadsheet don't match up with what REW is doing if using the overall curve and then setting the acoustical xover points in REW for the corresponding speaker.
    Don't know which one is off now, but there's definitely a difference.

    See for yourself.

    Click image for larger version. 

Name:	difference_jazzi_rew.JPG 
Views:	279 
Size:	100.3 KB 
ID:	10981

    Orange-red is the unaltered curve for a middbass crossed 80Hz highpass, 2500 Hz lowpass both LR24db from your spreadsheet and blue is what REW is doing when using the overall curve from your spreadsheet, setting it to subwoofer and adding a 2500 Hz lowpass and 80Hz highpass.
    Maybe that's one of the reasons why i had to flip polarity on my midbass to have the correct summing? Never had to do that when i was using the single curves from your spreadsheet, 'cause the slopes do not match.
    SYNC3 headunit
    Mosconi Pico 8/10 DSP
    Mosconi D2 500.1
    Gladen Zero Pro 165.3 DC
    JL Audio 10w3v3 in custom enclosure (Blueprint by Mark @Caraudiofabrication)

  8. Back To Top    #18

    Re: How-To: Verify Phase Cohesion Through A Crossover

    Quote Originally Posted by Cathul View Post
    That's what i thought, too, but the speaker curves from your spreadsheet don't match up with what REW is doing if using the overall curve and then setting the acoustical xover points in REW for the corresponding speaker.
    Don't know which one is off now, but there's definitely a difference.

    See for yourself.

    Click image for larger version. 

Name:	difference_jazzi_rew.JPG 
Views:	279 
Size:	100.3 KB 
ID:	10981

    Orange-red is the unaltered curve for a middbass crossed 80Hz highpass, 2500 Hz lowpass both LR24db from your spreadsheet and blue is what REW is doing when using the overall curve from your spreadsheet, setting it to subwoofer and adding a 2500 Hz lowpass and 80Hz highpass.
    Maybe that's one of the reasons why i had to flip polarity on my midbass to have the correct summing? Never had to do that when i was using the single curves from your spreadsheet, 'cause the slopes do not match.
    When using the "Bass Limited" or "Subwoofer" "Target Type" settings in REW, it seems to use a crossover type other than Linkwitz RIley (not sure which one it uses off-hand). However, what you can do is select "Speaker Driver" as the "Target Type" in REW - that way it lets you select the crossover type manually. If you want REW to use Linkwitz Riley / 24dB slopes, you can select "Speaker Driver", then "LR4" for the "Crossover HP/LP type" fields.

    I think if you do that then the REW target curves will match the curves from the spreadsheet.

    Hope that helps.

  9. Back To Top    #19
    Noob Cathul's Avatar
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    Re: How-To: Verify Phase Cohesion Through A Crossover

    Quote Originally Posted by jtrosky View Post
    When using the "Bass Limited" or "Subwoofer" "Target Type" settings in REW, it seems to use a crossover type other than Linkwitz RIley (not sure which one it uses off-hand). However, what you can do is select "Speaker Driver" as the "Target Type" in REW - that way it lets you select the crossover type manually. If you want REW to use Linkwitz Riley / 24dB slopes, you can select "Speaker Driver", then "LR4" for the "Crossover HP/LP type" fields.

    I think if you do that then the REW target curves will match the curves from the spreadsheet.

    Hope that helps.
    Thanks for that tip. Just verified that the curves match, and they do.
    Guess my wife will hate me next week.
    On the other hand i don't really know if i need/want to do it over again as the system measures and sounds good right now.
    So i don't really know if i want to do it again just for the sake of getting rid of a phase flip.
    SYNC3 headunit
    Mosconi Pico 8/10 DSP
    Mosconi D2 500.1
    Gladen Zero Pro 165.3 DC
    JL Audio 10w3v3 in custom enclosure (Blueprint by Mark @Caraudiofabrication)

  10. Back To Top    #20
    Wave Shepherd - aka Jazzi Justin Zazzi's Avatar
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    Re: How-To: Verify Phase Cohesion Through A Crossover

    Quote Originally Posted by Cathul View Post
    Thanks for that tip. Just verified that the curves match, and they do.
    Guess my wife will hate me next week.
    On the other hand i don't really know if i need/want to do it over again as the system measures and sounds good right now.
    So i don't really know if i want to do it again just for the sake of getting rid of a phase flip.
    Ahh yes, the eternal struggle
    Measure with mics, mark with chalk, cut with torch, grind to fit, sand to finish, paint to match.
    Updated Justin tuning sheet (Justin and Erica tuning companion for SMAART and REW)
    Do it for them.

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