Wierd Speaker / Sub Problem

ijwalla · 08-03-2007, 12:42 PM

I dont know much about audio stuff, but he's what I do know.

As soon as I go to close my trunk lid, my sub begins to hum eradicly.
After the lid is closed, the sub relaxes, but the speakers in my car reduce in volume and begin to crackel.

I assume its something to do with air flow, I just dont know what exactly.

The specs of my setup are below, any suggestions would be very much apreciated.

4 Channel Sony Amp
1300w Sony Amp
2 Sony speakers

Sub Box Size (3ft Width,1.2ft Depth, 2ft Height)

Oh and if it of any use, the air intake hole of the sub box is the size of a tennis ball. I had the box custom made for my car...

Thanks again...

BiG K · 08-03-2007, 05:23 PM

Check the ground wire from your AMP, not sure how it all works, but make sure it is grounded properly!
A more experienced member will be able to tell you more, or if you search around the forums, you will find the answer!

pancit175 · 08-03-2007, 08:25 PM

My first reaction with this problem is to ask this question: Are any wires or cables that are run around the area where the trunk lid's arms or torsion bars are traveling where there is a possibility of being pulled, pinched or grounded?

At first glance I dont think it has to do with the amount of air-flow available because of the collateral effect to your interior speakers.

greatwhite · 08-03-2007, 08:30 PM

Quote: Originally Posted by pancit175

My first reaction with this problem is to ask this question: Are any wires or cables that are run around the area where the trunk lid's arms or torsion bars are traveling where there is a possibility of being pulled, pinched or grounded?

At first glance I dont think it has to do with the amount of air-flow available because of the collateral effect to your interior speakers.

Airflow?

Very doubtful..............

"Air intake hole"? In a sub box?

Sony?

Umm.....nothing personal, but you weren't kidding about the newb thing.

I would suspect your air intake hole is a port for a ported box.

And sony isn't the highest quality stuff. Acceptable to begin with, but don't expect alot out of it sound quality wise........

Read a few online tutorials about audio, re-check you install, and go from there.

Did you install it yourself or have a shop do it? If a shop did it, take it back and have them fix it...........

Good luck

ijwalla · 08-03-2007, 09:00 PM

Quote: Originally Posted by pancit175

My first reaction with this problem is to ask this question: Are any wires or cables that are run around the area where the trunk lid's arms or torsion bars are traveling where there is a possibility of being pulled, pinched or grounded?

At first glance I dont think it has to do with the amount of air-flow available because of the collateral effect to your interior speakers.

Im 100% sure there are no wires around the trunk lid.

The only reason I think its air flow related it because having the trunk lid open with plenty of air flow, works perfectly, absoloutly no problems. After I close it, the sounds begins to get distorted...

As for the air intake hole on the sub box, most boxes have them, its a small hold on the side to let air either in or out...

greatwhite · 08-03-2007, 09:05 PM

and it's called a "port". For a ported box. There should be a small length of tube in it, not just a hole.

It's used to tune the bass response.

And no, most boxes don't have them. Low to average subs are usually better off with a sealed enclosure.

If you're running a sony sub, most of them are recommended for a sealed enclosure. Not ported (although some will work in a ported enclosure if it's big enough). Check the documentation that came with the sub if you want to be sure.

Basically here are three types of boxes (with some variations):
sealed
ported and;
bandpass

Hmm......

Are you running the 4 channel in a 2/1 configuration? meaning 2 channels for the speakers and 2 channels bridged to one for the sub from the 4 channel sony amp?

If so, I'd double check that it is wired correctly. Again, check the documentation that came with the amp if you're unsure.

Once again, airflow? Very doubtful............

Kind of an urban myth for most setups really.................

Are you sure it's not just the trunk panel/body pannels rattling/vibrating?

90% of the time, problems are related to a poor install (cheap/too thin power wires, wired wrong, poor RCA's, power draw from poor source, grounds, etc) or low end components.

Closing the trunk lid should have no effect on the cabin speakers. At all. I'm betting you have an install problem somewhere.......

Good luck

pancit175 · 08-03-2007, 09:39 PM

Respectfully, I believed I asked about the travel of the arms of the trunk lid, and not the lid itself. The point I mean to make is if something is getting pinched, or pulled when you are closing your trunk.

I really, really, doubt that its an "air-flow" problem. Subs require little surrounding air to provide air compression and pressure differential. There are many reasons why the majority of people put their subs in the trunk, other than the lack of space any place else. An example with home theater, a sub is not as effective in the center of the room as it is effective in the corner of the room. Plus that amp and sub combo is not nearly powerful enough to even start worrying about the acoustical dynamics of your vehicle. So something has to be going on with how everything is wired up.

Greatwhite puts up a great point, How many amps do you have? And how do you have them hooked up in relation to your source?

ijwalla · 08-03-2007, 09:43 PM

Quote: Originally Posted by greatwhite

Are you running the 4 channel in a 2/1 configuration? meaning 2 channels for the speakers and 2 channels bridged to one for the sub from the 4 channel sony amp?

If so, I'd double check that it is wired correctly. Again, check the documentation that came with the amp if you're unsure.

Once again, airflow? Very doubtful............

Thanks for your advice, seriously...

As far as I know its a sealed box, as for the hole, not sure why it has one, its has meshing over it...

Here is the schematics I followed, its exaclty as you described...

I dont know what those two switches are for, but its setup exactly as shown...

Quote: Originally Posted by pancit175

Respectfully, I believed I asked about the travel of the arms of the trunk lid, and not the lid itself.

Correct u did say that. The lid has some piston arms that are seperate from the inside cabin of the trunk. Its a 5 series BMW.

I'm leaning towards my theory of air intake being wrong too... hummm

Hope the Image helps...

pancit175 · 08-03-2007, 09:54 PM

Is that amp just powering the 2 subs, or do you have the interior speakers hooked up to it as well? If so do you have the subs in parallel together or in series? There is a great possibility that you do not have the impedances at safe configurations.

The switches are used to turn on the High Pass Filter (HPF) to only allow high frequencies through, the other is a Low Pass Filter (LPF) to only allow low frequencies through. You want the LPF "on" at the channels that you have the subs hooked up to. And it shows the cut off frequencies are @ 80Hz

ijwalla · 08-03-2007, 10:02 PM

Quote: Originally Posted by pancit175

Is that amp just powering the 2 subs, or do you have the interior speakers hooked up to it as well? If so do you have the subs in parallel together or in series? There is a great possibility that you do not have the impedances at safe configurations.

The switches are used to turn on the High Pass Filter (HPF) to only allow high frequencies through, the other is a Low Pass Filter (LPF) to only allow low frequencies through. You want the LPF "on" at the channels that you have the subs hooked up to. And it shows the cut off frequencies are @ 80Hz

I just have the 1 sub hooked up exactly as shown in that image.

Also the images show both the HPF & LPF to be set to "on" which is how I have it.

As for the impedance levels, the subs 4 ohms and the cabin speakers are 2 ohms each, so they should be ok right?

XC-C30 · 08-03-2007, 10:07 PM

5-series BMW? hmmmmm sedan.....

Almost 100% sure it has to do with the box. Probably tuned too high. If you open up the trunk you'll let it play sort of free air for a while. If I were you, I'd build a new sealed enclosure (yes the one you have now is a vented one, otherwise it wouldn't have the "air intake").

About sony being crap: Not totally true. But the thing is sony is just too expensive for what it is. But I've heard some installs where I really got surprised when seeing they had a sony sub. I'm not saying it's the best you can get, but it'll do....one 1 condition:..... you have to box and tune it right. I know some of you are gonna say: "enclosing and tuning is crucial with whichever speakers you use!." True but with a really good driver it won't come to little details.... with a sony sub, it does.