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1999 Jeep Wrangler TJ
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Discussion Starter · #1 ·
I have this in my Optimizing my Beginner's System thread, but I wanted to throw this in a new thread as that thread is already huge and people may overlook it.

I've been tinkering with my system the past few days thanks to acquiring a calibrated mic (I can play with the big boys now). After a lot of adjustments recommended by Lithium (thanks, Lithium!!!) I've managed to get it sounding pretty good overall. Like lay back in the seat and enjoy the music instead of just criticizing how every bit sounds.

I do have a problem: I get a pretty big, 5 - 7 dB, dip at the 180 Hz range. I'm really not sure what to do at this point, but I'd like to address it before I start really playing with channel independent EQ for soundstaging (and learning how the heck to do that).

Rectangle Slope Screenshot Font Line


It exists on each of my mid woofers separately, combined, and with the sub playing.

Slope Font Screenshot Line Plot


It happens in every position I test. Fr Driver, Fr Pass, Fr Center, and really bad at Rr Center.

Light Black Slope Font Screenshot



Lithium suggested reading up on cabin mode, which I have, but I'm not quite getting any answers that help so far.

It could easily be the woofers I'm using. 5.25, fairly low grade, they're the weak point in my system, for sure. Everything else is pretty decent.

Also, I'm in an old Jeep Wrangler that had most of the interior panels and carpet ripped out by the previous owner. I'm sitting in what's essentially a tin can. Also, the interior of this Jeep is tiny. My sub is in the "trunk", yet the distance from it to my head is shorter than the distance from my head to the right woofer, if that gives any indication.

My crossover settings are as follows:

Font Audio equipment Electronic device Event Circle


I just changed the sub LPF to a -12 dB to see what would happen. Actually seems to improve the bass a bit subjectively.

Anyone have any thoughts/insights on this? I'm scratching my head at the moment.
 

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Have you taken a near field measurement to compare to? If the dip isn't there when you take a measurement an inch or so from the speaker, than it's due to your cabin geometry(most cars have a dip somewhere near that frequency) and seating position. This can't really be fixed unless you change up some serious stuff. Like change location of the speaker to the kick panels for example.
If it is there in the near field measurement than it is probably caused by door resonances causing some cancelation. In which case you may be able to remedy by doing more treatment on the doors.
 

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2004 Rav4 JL900/5 NVXvad2 MiniDsp 8x12(Dirac) LPG26NA GS25 Epique180-44 Um12
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This route isn’t for everyone but it’s a short read and on the second page it gets to the point. My doors are still not ideal and I’m planning under dash midbass but I managed to significantly improve the response by fiberglassing over most of the inner doors.

 

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2004 Rav4 JL900/5 NVXvad2 MiniDsp 8x12(Dirac) LPG26NA GS25 Epique180-44 Um12
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Another thought after reading the original post again is that something like the roof or other big-ish panel might be resonating. This seems to make more sense than the door deadness as I noticed the subwoofer dips seemingly in ratio to the spl produced.
Automotive tire Hood Automotive lighting Motor vehicle Trunk


Here’s a photo of when I first installed my UM12 through the floor. The circled area is a cavity where I couldn’t screw the 3/4 mdf down. I had a very noticeable dip around 80hz and when I put something heavy on the spot it completely went away. I ended up bracing underneath and now it’s all but gone.

Perhaps you can set up your measurement gear and feel around for something resonating and press on it to see if it stops.
 

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1999 Jeep Wrangler TJ
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Discussion Starter · #5 ·
Another thought after reading the original post again is that something like the roof or other big-ish panel might be resonating. This seems to make more sense than the door deadness as I noticed the subwoofer dips seemingly in ratio to the spl produced. View attachment 313370

Here’s a photo of when I first installed my UM12 through the floor. The circled area is a cavity where I couldn’t screw the 3/4 mdf down. I had a very noticeable dip around 80hz and when I put something heavy on the spot it completely went away. I ended up bracing underneath and now it’s all but gone.

Perhaps you can set up your measurement gear and feel around for something resonating and press on it to see if it stops.

I'm sorry, I should have explained more thoroughly.

I drive a 99 Jeep Wrangler TJ. I have 5.25s mounted in speaker pods in the dash. They're about seat level and face straight into my leg. I have tweeters mounted to the a-pillar. There is very little in the way of sound deadening in the vehicle. I'm about to start a deadening project, but I have to rust treat and rust proof the interior first, so it's been delayed a bit.

Would sound treatment help?

I didn't notice any resonances, but I'll play with sine sweeps in the morning. If you don't mind me asking, is there a way to test resonances with measurement gear?
 

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Discussion Starter · #6 ·
Have you taken a near field measurement to compare to? If the dip isn't there when you take a measurement an inch or so from the speaker, than it's due to your cabin geometry(most cars have a dip somewhere near that frequency) and seating position. This can't really be fixed unless you change up some serious stuff. Like change location of the speaker to the kick panels for example.
If it is there in the near field measurement than it is probably caused by door resonances causing some cancelation. In which case you may be able to remedy by doing more treatment on the doors.
Interesting! I'll certainly test that in the morning. So, run test near each speaker and compare to seated position. I am considering getting another amp to hook to the overhead speaker bar (it's disconnected at the moment) to run 80 - 200 Hz to fill that midbass. However, that might take a little while for that purchase (I have mechanical issues to fix as well), so I'd like to address it however I can in the meantime.
 

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Interesting! I'll certainly test that in the morning. So, run test near each speaker and compare to seated position. I am considering getting another amp to hook to the overhead speaker bar (it's disconnected at the moment) to run 80 - 200 Hz to fill that midbass. However, that might take a little while for that purchase (I have mechanical issues to fix as well), so I'd like to address it however I can in the meantime.
Exactly. It will tell you what's from the legit frequency response of the speaker, and what is the car.
 

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Discussion Starter · #8 ·
Exactly. It will tell you what's from the legit frequency response of the speaker, and what is the car.
Oh that's an awesome tip! Thank you. I'm tempted to run outside in the dark and give it a whirl. Don't think my neighbors would appreciate it, though 😂. I'll be up super early replacing a couple of pulleys and a serpentine belt, so I can do that right after.
 

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Discussion Starter · #9 ·
Here are the results:

Light Black Slope Font Screenshot


Red is the left woofer, green is the right woofer, blue is from the driver's head position.
 

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Discussion Starter · #10 ·
I didn't have the drivers solo'd, so I'll try that in a sec.
 

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Discussion Starter · #11 ·
Here we go. Same graphs as before, but added the woofers solo'd.

Light Slope Font Line Screenshot
 
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