DiyMobileAudio.com Car Stereo Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
344 Posts
Discussion Starter · #1 ·
I have been rtaing the car and notice a 5db dip at 160hz. My EQ only has 125 and 200 so I can not correct it with eq settings.

The door has 2 layers of rammat on the outer skin, 1 layer of closed cell foam, the inner panel has a layer of rammat + spray on rubber coating. The door panel itslef has a layer of rammat and rubber coating so it is pretty solid.

Any suggestions on how to get rid of the dip? Should I put more foam behind the speaker maybe some egg crate foam?
 

·
Registered
Joined
·
403 Posts
Does it sound like the frequency is missing something? Or, is the RTA god?
 

·
Registered
Joined
·
513 Posts
Did you RTA using multiple spots and average the results? Just a couple inches can change things dramatically.

As for the dip, its pretty common to have 5db peaks and dips like that. That's why cars are so complicated to get right acoustically. Personally, I have a 7 db dip at ~160 on my left and about a 4db dip on the right. Unfortunately foam isn't going to do anything at that low of a frequency.

Your EQ options are, believe it or not, very good for this IMO. You don't want to be boosting dips anyway as they're often caused by cancellation, so boosting could actually make the dip even deeper. If you can use your EQ to drop 125 and 200 to approximately flatten the area out that would probably work a lot better in the end. Just use as high of a Q as possible so you don't overly affect 160.
 

·
Registered
Joined
·
687 Posts
Is 160Hz near a crossover point?
Try running a sine sweep and listening by ear (no RTA) and see if you can spot the drop or not. Also try a sine sweep on the left side only and the right side only to see if one or both of the drivers are the culprit. Separate left/right EQ may help, and a 160Hz band obviously would help, but the previous poster mentioned, if you happen to have slight peaks at the 125 and 200Hz ranges, toning those down may help.
 

·
Registered
Joined
·
344 Posts
Discussion Starter · #5 ·
I'm running the 800prs so I do have left and right eq control so will have to try the sweeps and lower 125 and 200 to see if I can smooth it out.
 

·
Registered
Joined
·
522 Posts
It is probably an issue with reflection. You might be getting a cancellation on that particular frequency due to a phase issue that is created by the distance between your midbass speakers and each other, or some other surface in the car that is reflecting the orignal soundwave from the midbass and bouncing back something that is out of phase at the frequency. One way that this is dealt with in an installation is to angle the midbass drivers rather than have them point directly at each other. That is tough to do.

160 Hz wave is 7 ft long. If you have an obstruction (like a console) that is right in the middle, you could be getting reflections that are out of phase with the original soundwave. Lots of ways this could be happening, but it most likely an issue with reflections. No sound deadening is going to help that, but speaker placement might.
 

·
Blue Collar Audiophile
Joined
·
10,287 Posts
Do you have a tuning disk with tones on it? I'd imagine tuning by ear with tones would be superior to the rta. I've gotten everything to sound flat BY EAR with frequency centered pinknoise with good results.
 

·
Registered
Joined
·
4,916 Posts
It is probably an issue with reflection. You might be getting a cancellation on that particular frequency due to a phase issue that is created by the distance between your midbass speakers and each other, or some other surface in the car that is reflecting the orignal soundwave from the midbass and bouncing back something that is out of phase at the frequency. One way that this is dealt with in an installation is to angle the midbass drivers rather than have them point directly at each other. That is tough to do.

160 Hz wave is 7 ft long. If you have an obstruction (like a console) that is right in the middle, you could be getting reflections that are out of phase with the original soundwave. Lots of ways this could be happening, but it most likely an issue with reflections. No sound deadening is going to help that, but speaker placement might.
Damn Car, if its not one thing it's another. As Danny stated earlier you can think of a dip as two peaks.
 
1 - 8 of 8 Posts
Top