Sub gets louder when I open the trunk???

[reible82nd 10+ year member]

Hey everyone, here's what I'm currently running:

Vehicle: 2009 Toyota Camry

Head Unit: Eclipse CD5435

Fronts and Rears: Eclipse Point Source 6x9s

Sub: Auditor RIP 250S (I know...)

Wiring: Cadence 4G Power and Ground, Knu Karma RCAs, 14G speaker wire...

I just tuned everything with a DMM...the highs sound great but when I crank the volume the bass sounds like it's distorting or something. When I open the trunk, the bass cleans up and gets substantially louder. Right now the sub is at the back passenger-side corner facing the driver's side (sideways). Are the 6x9s in the back dash and the sub out of ttime or something? Where do I need to place the sub to solve the issue?

Click to read more...

 

[quackhead 10+ year member]

maybe take the 6x9's out and let the sound in the trunk enter the cabin?...just curious, but what amp and box do you use?

 

[THATpurpleKUSH 5,000+ posts]

sounds like a sealed box if its in the corner facing sideways

 

[mazdakid 5,000+ posts]

Lots of trunks are like that. Mine is mostly sealed off all facing forward and i still gain on the meter when i open the trunk.

 

[reible82nd 10+ year member]

Oh, sorry guys...I'm running an Eclipse EA 3532 on everything...the sub is in a sealed enclosure...

 

[reible82nd 10+ year member]

.75 as a matter of fact...a little small for the sub but makes it a bit more punchy which benefits double-bass notes when listening to death metal //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[basshead7890 10+ year member]

a post from another forum that might help you out

Either i'm misunderstanding what he's trying to do or he's misunderstanding what he's trying to do and when/why it should be done. Judging from the posts he's made it sounded to me like he wanted to completely seal off the trunk from the cabin to "negate that sound wave issue in cars with trunks" (cancellation). But he never made any mention of firing his sub(s) into the cabin, furthermore he was asking "what dimensions did you make the sheet of MDF", until he chimes in to clear the air I can only assume his plan is to simply put up a wall directly behind his back seat to seal his trunk from the cabin. The only way that would work well is if he is:
A.) Going to run his sub(s) in IB alignment

B.) Going to build a 4th order and port it through the rear deck or ski pass opening.

or

C.) Going to run his sub(s) and port forward with that wall being used as the baffle of the box.

If he's not planning on doing either of the above, sealing off the trunk is a bad idea.

The whole purpose to sealing off the trunk is to eliminate the issue of cancellation due to the front and rear sound waves being out of phase with each other. How do you know if you have cancellation? Easy. Sit in your car and listen to a song you're familiar with, while you're listening to the song have a buddy open the trunk, if the bass gets louder then you indeed are having cancellation issues. How can the bass get louder with the trunk open? Makes no sense huh?

In this picture the vertical line is the back of the trunk and the black box is the subwoofer box which is facing towards the cabin. When the sub hits, the sound goes foward into the cabin (red wave) but also reflects off the back of the trunk to become the reflected wave. When those two waves are way out of alignment as shown in the picture there will be major cancellation. Simply opening the trunk will cause that reflected wave to "disappear" and not reflect back in the trunk and not cause cancellation in the process.

In this picture the sub is aimed at the trunk and the result is that the waves aren't nearly as out of phase as the first picture, resulting in much better bass response but still not as good as it can be.

In this picture the sub box is moved so it's closer to the back of the trunk with the sub firing towards the trunk resulting in the waves nearly being in phase with each other resulting in the best bass response.

Firing the subs/port into the cabin with the baffle of the box sealed off from the trunk results in a wave patter much the same as the last picture, directs all the sound/air into the cabin area and nearly eliminates that horrendous trunk rattle on high powered systems too.

 

[zako 10+ year member]

This could be a phase relationship issue. This is just one theory. Your subwoofer is out of phase with your midbass speakers, which causes some cancellation of SPL around the crossover region. Why you open the trunk, the out of phase wave escapes instead of reflecting back into the car from the rear end. Try to flip the electrical phase of the subwoofer. Also try changing the location and orientation of subwoofer box.

This article may be helpful to read.

Aiming a woofer box in a car trunk - bass cancelation -

 

[reible82nd 10+ year member]

Thanks for the help everyone! I think because the 6x9s are exposed in the trunk (facing into the cab in the back dash) it's disrupting the sound waves coming from the sub...I think I'm going to put the sub in-line with the 6x9s facing the rear of the trunk, that should get the sound waves from both the 6x9s and the sub in sync and fix the problem. I'll post an update once that's done.

 

[gunz4me2 10+ year member]

It could also be a standing waves cancellation issue from all the reflections and popping the trunk allows those standing waves to escape.

After all, the wave length for various frequency tones are roughly as follows:

30 Hz ≈ 37.67 feet

40 Hz ≈ 28.25 feet

50 Hz ≈ 22.6 feet

60 Hz ≈ 18.83 feet

and so on

The point? What is the typical length of the interior of a modern day trunk car? Going further, what about the detriments of putting a suwoofer box in a box (i.e. the trunk)?

 

[quackhead 10+ year member]

Thanks for the help everyone! I think because the 6x9s are exposed in the trunk (facing into the cab in the back dash) it's disrupting the sound waves coming from the sub...I think I'm going to put the sub in-line with the 6x9s facing the rear of the trunk, that should get the sound waves from both the 6x9s and the sub in sync and fix the problem. I'll post an update once that's done.

This would be a reason for audible distortion as well, the subwoofer may be actually driving the 6x9's and causing all kinds of sonic issues....try removing the 6x9's and see if there is a audible difference in bass quality inside the cabin.

 

[hispls 5,000+ posts]

You should do a LOT of experimenting with box position and aiming.

 

[stevew007 10+ year member]

well i had the same problem in a 91 grand am it had like a 7" rear deck. i took out the 6x9's built a bandpass box that ported towards the 6x9 holes.still had the same problem until i shoved a towel in the 2" space between the top of the box and the rear deck.it made the biggest difference in the world.

 

[reible82nd 10+ year member]

What if I went I.B. with my sub (aiming into the cab) and left the 6x9's there? That would make the trunk an "eclosure " for both the 6x9s and the sub...sort of liked a shared chamber.

 

[stevew007 10+ year member]

do the seats fold down?