Windsheild destructive reflection remedies

[captainobvious]

Do you have measurements of *JUST* the midrange playing? Those look like they are the whole system playing...
Also, try stuffing some towels down in the dash behind that driver to soak up the rear wave and measure again.

[chithead]

Listen to him ^^^ He's pre-law. Or pre-med. What's the difference.

[Truthunter]

Do you have measurements of *JUST* the midrange playing? Those look like they are the whole system playing...
Also, try stuffing some towels down in the dash behind that driver to soak up the rear wave and measure again.

Yes, I did measure with just the mids (though did not capture the results) and found the same response anomaly around 1.5khz.

There was several layers of 5lb carpet padding behind the mids back when these measurements were taken. The padding is being replaced with Ultratouch denim insulation... actually any empty void in and under the dash and elsewhere in the car will be filled with ultratouch.... thanks to you

Working with Mr. Apicella for a permanent driver tilt solution kinda in the fashion of Mr. Bertholomy's mids

[chithead]

Thats good stuff right there. Harman had a writeup regarding windshield reflections and found a sweet spot of sorts, long as the speaker had a specific angle to the windshield.

[sssnake]

Harman had a writeup regarding windshield reflections and found a sweet spot of sorts, long as the speaker had a specific angle to the windshield.

Do you have a copy of this article. I had it on my laptop but have recently switched to a new one and can't find it on either.

[Truthunter]

Permanent solution in progress:

[Hic]

WOW , that looks GREAT !

[klimbo]

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:



I did perform this test and the null remained.




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.




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 Tutuapp 9apps Showbox




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.

hi
i have a very interesting question can you help me please ?

[Truthunter]

hi
i have a very interesting question can you help me please ?

Hi,
Maybe I or someone else here can help... what is your question?

[dumdum]

The comb is determined by the distance of the mid from the screen, you may get more energy from the screen at higher freqs with them tilted up a little, but that’s likely due to the mids being a touch less of axis

a shallow angle and the rear lip as close as you can get to the screen will push the comb higher, you’re also getting a reflection from the a pillar, by moving the mids closer to the screen upwards you will change the relationship between the two reflections and spread them more, there will be an optimum height and distance from the a pillar to get the two out of sync with each other and one will reinforce the others dip so the net gain or loss due to combing will be way less than a symmetrical spot if that makes sense, also the left will need a different spot to the right without question as you are at different angles to both drivers, reflections will be at different freqs

by making them symmetrical you are putting combs and phase issues due to reflections at different freqs, this makes it harder to get good phase coherence between left and right... the drivers side wants to be a little further away from the pillar to the passenger side, passenger side will suffer worse with reflection dips due to the angle your listening to it from as they will be lower in freq normally