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Thread: Windsheild destructive reflection remedies

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    Noob Truthunter's Avatar
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    Windshield destructive reflection remedies

    So I've got my mids mounted in my stock corner of the dash locations in my Camry. They actually sound pretty great overall except for a terrible 1.5khz null as seen here. They are actively high passed at ~250-300hz using the crossover in the amp and low passed at 2200hz using the morel passives. Blue trace is after some eq work through the headunits dsp:




    Here is how the speakers reside:




    The null remains with the tweeters off and also with the polarity switched on them. So, I'm 99% sure its destructive reflections from the windshield.

    Before I proceed with expanding my system with additional equipment, I'm determined to remedy this 1.5khz null as I can plainly hear it and I believe it's killing presence in voices/strings and the snappiness of snares.

    Here are a few possible remedies which I am contemplating but I'm always open to other's suggestions/critiques. Please feel free to let me know if these ideas are poop or if you have any other ideas.

    1. Dash Pod for the mid to tilt them up to be on axis and further away from the windshield. Like this but just for the mid (tweeter will go in piller or sail):



    2. Move mids to kick panels. -Concerns of losing stage height.

    3. Replace tweeter with something that can play lower to take this null out of the mids passband... perhaps something like a Pioneer TS-S062PRS mid in the pillar or sail and on axis. I realize it would not provide the same top end extension but I honestly can't hear anything above 11khz anyway. I would cross it over to the mid 900-1khz. I heard these in a vehicle recently and was really blown away by them albeit they were accompanied by the prs tweeter.

    I'm really looking for direction here. I know some of you have dealt with this issue before and I would like to hear about your experiences in trying to remedy it.
    Last edited by Truthunter; 09-06-2017 at 06:38 PM. Reason: grammer

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    Re: Windsheild destructive reflection remedies

    While I don't doubt this may be a suck out because of location of drivers (always a possibility), I also feel you should test bypassing the crossover before getting to hung up on changing stuffs around. May be a shot in the dark, but a quick test of just the mid high passed off of the amp could rule out any "voicing" of the driver set via the passives, something not that uncommon at all.

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    Noob naiku's Avatar
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    Re: Windshield destructive reflection remedies

    Quote Originally Posted by Truthunter View Post
    2. Move mids to kick panels. -Concerns of losing stage height.
    I had this exact same concern when moving my mids to the kick panels. I had been temporarily running them in PVC cups on the dashboard while debating making little pods like you are describing, but for me, they took too much away from the stock look I wanted. I was definitely worried about losing the height in moving them to the kick panels, but it is a non-issue. I have mine at 450Hz to 3500Hz, could be wrong on the 3500, might be higher, and the stage is currently about 4-6" above the dash height, vocals are right up in the middle of the windshield.

    If you decide to go with kick panels, then don't worry about the stage height, especially since you will ultimately be putting the DSP in there as well.
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    Senior Member chefhow's Avatar
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    Re: Windsheild destructive reflection remedies

    I have a couple of suggestions.
    1. can you drop the front of the mid to create an angle similar to that of the windshield so that you try to minimize the reflection you have that may be causing the null you are experiencing?
    2. Have you turned off the mic and just listened to music? Not trying to be an ass, just a suggestion we often times forget to do(myself included). 1.5-2K is where you get a lot of sibilant off notes in vocals that can come off as harsh and some nasal qualities. Having a natural dip there may be more beneficial than you know.
    3. Is it possible to change the grill to allow you to corner load the mid range so its more on axis from the passenger side dropping the left side of the driver or raising the right side into the corner? Rather than build HUGE pods make a small cosmetic change to just the grill.

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    Owner BigAl205's Avatar
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    Re: Windsheild destructive reflection remedies

    Yeah, I was going to suggest changing the driver angle. Of course if you were feeling really industrious, you could make a whole new baffle similar to Jason's BRZ






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    Owner BigAl205's Avatar
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    Re: Windsheild destructive reflection remedies

    Also, have you put something behind the driver to make sure the back wave isn't creating cancellations?

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    Senior Member chefhow's Avatar
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    Re: Windsheild destructive reflection remedies

    Al, thats what I was thinking when I suggested the angling of the driver. I knew i had seen it but i couldnt remember where. Thanks for digging up the pics!!

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    BURNED OUT Hillbilly SQ's Avatar
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    Re: Windsheild destructive reflection remedies

    Quote Originally Posted by BigAl205 View Post
    Also, have you put something behind the driver to make sure the back wave isn't creating cancellations?
    Yeah that's more important than a lot of people realize. Back wave isolation isn't just for midbass.
    They might say "don't try this at home" but nothing about not trying it at your friend's house.

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    Noob Truthunter's Avatar
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    Re: Windsheild destructive reflection remedies

    I don't have access to CAJ from work... it's blocked while the other forum is not for some reason. And for some reason I'm not getting email notifications of replies (probably need to set my preferences for that ). So I was at work all day waiting for a notification email and wondering if anyone was ever going to respond.

    Great questions and suggestions... So here we go:

    Quote Originally Posted by claydo View Post
    While I don't doubt this may be a suck out because of location of drivers (always a possibility), I also feel you should test bypassing the crossover before getting to hung up on changing stuffs around. May be a shot in the dark, but a quick test of just the mid high passed off of the amp could rule out any "voicing" of the driver set via the passives, something not that uncommon at all.
    I did perform this test and the null remained.


    Quote Originally Posted by naiku View Post
    I had this exact same concern when moving my mids to the kick panels. I had been temporarily running them in PVC cups on the dashboard while debating making little pods like you are describing, but for me, they took too much away from the stock look I wanted. I was definitely worried about losing the height in moving them to the kick panels, but it is a non-issue. I have mine at 450Hz to 3500Hz, could be wrong on the 3500, might be higher, and the stage is currently about 4-6" above the dash height, vocals are right up in the middle of the windshield.

    If you decide to go with kick panels, then don't worry about the stage height, especially since you will ultimately be putting the DSP in there as well.
    Thanks Ian for reminding me of your setup. I remember now that your stage was on the dash and your mids in the kicks. I will keep this in mind.


    Quote Originally Posted by chefhow View Post
    I have a couple of suggestions.
    1. can you drop the front of the mid to create an angle similar to that of the windshield so that you try to minimize the reflection you have that may be causing the null you are experiencing?
    2. Have you turned off the mic and just listened to music? Not trying to be an ass, just a suggestion we often times forget to do(myself included). 1.5-2K is where you get a lot of sibilant off notes in vocals that can come off as harsh and some nasal qualities. Having a natural dip there may be more beneficial than you know.
    3. Is it possible to change the grill to allow you to corner load the mid range so its more on axis from the passenger side dropping the left side of the driver or raising the right side into the corner? Rather than build HUGE pods make a small cosmetic change to just the grill.
    1. Yes, I plan on experimenting with this to see if it makes a difference...

    2. Yes, I've been listening to it like this for a while now and overall it sounds good with most music. And I understand that some may cut this area to reduce harshness. But I feel like voices/strings sound as though they are muffled because of this deep and wide null causing a lack of presence... like there playing down in a hole. It's not really noticeable with transient electric music but it sounds off with tracks that contain vocals/strings or similar sounding instruments that play through this range with smooth amplitude variations.... I hope that makes sense

    3. I think this is similar to what you are saying in point 1?... but maybe tilt the driver toward the center more?.. Yes, I did think of this as I demo'd Jason's car at Ian's this spring and asked him why his mids were tilted like they were. I do plan on experimenting with this to see if it helps... I really like how Jason's dash mounted mids came out and it sounded incredibly realistic but unfortunately I don't think I have the skills to make it look so nice


    Quote Originally Posted by BigAl205 View Post
    Also, have you put something behind the driver to make sure the back wave isn't creating cancellations?
    The dash locations are mostly open to out the bottom of the dash but they do have HVAC ducting that runs about an 1" under where the mid resides in about 30% of the area. I have stuffed two layers of 5lb carpet padding in there to try and absorb any reflections they may be occurring... whether or not that's helping is unknown.
    I also made sure that any openings like the back edge of the dash (by the windshield) and the holes the grills clip into are sealed to prevent any back wave energy from escaping. This actually made a positive change to the sound... more controlled/snappy and improved low end output.



    So, I think I will perform the following tests and go from there:

    1. Unmount the mid and measure it free air on-axis to off axis to verify it's not just a problem with the driver FR itself.

    2. Experiment with tilting the mid in different directions like Howard suggested to see if the issue improves.
    Last edited by Truthunter; 09-06-2017 at 06:49 PM.

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    ~Paw~Paw})]<^>¥ Hic's Avatar
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    Re: Windsheild destructive reflection remedies

    What do you have to "temporarily" block these reflections ? Redirection via a 90 degree / right angle pvc elbow of sufficient size ( 6 inch ).
    Ie: rubber / carpet / towels / et cetera , think softest surface and extremely thick , facing drivers in direction that allows you to avoid majority of reflections - " temporarily ". Perhaps towels wrapped around rear of speakers and speakers firing at each other ! I believe your ears will suffice for your temporary testing to determine that reflective energy is your issue ( my bet ).
    Last edited by Hic; 09-10-2017 at 07:40 AM.
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