Weird noise at low volume

im not sure why this is happening, my deck volume goes up to 63. I usually listen to it at about 40-44. it sound fine at higher volumes and even almost all the way down but when i get to about 3 or 4 i can hear an odd sound from my subs. its like a hollow sound. im almost positive it is the enclosure. i never noticed it before i had this new box built. i just want to make sure i haven't damaged my subs because the only way to replace them is to take the box apart. it is built into my car and it would be a bitch to replace.
and i drew a diagram of my box on my computer but i dont know how to get it onto the post. i tried copy and paste, didnt work. neither did trying to drag it onto here. anyone know how to do it?

think i have the same problem - its like a faint wooshing noise coming from one of the channels and im pretty sure it would be the amp doing it. thort it mite be interference or sumthing but now im not so sure.

no mine is coming out of the port. its just a hollow sound. if air could rattle, that is what it would sound like. im pretty sure it is my box.

o so u hear it wen music is playing but just when its quiet and its sum sort of a resonating sound. mmm that is different, anyone know anything bout this?

I think that's probably what people call port noise.. try sanding sharp edges off anywhere air has to be moving, and it might help... I've never heard it myself, because I'm just starting out and I have a sealed box, but that's what I imaged when people started talking about it. I'm sure NG or SR or bumpin will tell you something about it.

i wish it was so easy. my box is part of the car now and cannot be accessed without destroying it. that sounds like a possibility though. it is a vented enclosure with the subs completely enclosed. the vent is right between my back seats where the arm rest folds down and is open to the trunk.
___________
back seat | fold down | back seat
____________| arm rest |____________
_______________ ________________
| \ | | / |
| \ sub | | sub / |
| \ port / |
|________\_____________ __/________|

its a crude drawing but i hope yall will understand it. any ideas on if it is the design of the box that is causing this problem?

well never mind, the diagram got all fucked up

hey, email (http://dce.ath.cx/images/me.jpg) that pic to me and I'll host it for ya. I think what you've got is some sort of bandpass box.

i emailed it. i dont know why i cant just copy and paste to the thread

I haven't gotten it yet (might just be lag time) so I can't host it just yet. You can't copy and paste into the thread because the code of this forum doesn't support displaying pictures that way. You have to use tags ([IMG ]whereyourpictureis.com[/IMG ]) and an external picture server to host it. There is provision for very small pictures to be hosted in your gallery, but it's not really worth it. I think Google has a picture hosting thing called picasa (http://www.picasa.com/index.php?tid=Y2NpZD0zNzQy) that I haven't looked at but read about.

that's definitely not port noise

Port noise happens when there is too much air trying to push through the port at the same time. In order to get all of it through the air has to go very fast, and the result is sort of a "whistling" sound coming from the port. It only happens at very high output near the tuning frequency of the box (that's when the amount of air going through the port is highest). What you're describing sounds like an electrical problem. Check the rcas to make sure they're not pinched, that's the only thing I can think of.

i sent it again from yahoo.com this time. i used my outlook before.

Ok, here's what you sent me, reduced from 2.3 MEGS... to 37 kb.

http://dce.ath.cx/images/diagram.jpg

Ok, here's what you sent me, reduced from 2.3 MEGS... to 37 kb.

http://dce.ath.cx/images/diagram.jpg

unless that port is actually 4 ports more than 3in d each thats way too small for two 12s.

(((im not implying your amp is cheap or that it sucks)))

I agree with the RCA diagnosis, cheap amps have noise no mattta what, pull the RCAs and turn the deck on and listen for noise. if you hear noise with no signal then your amp sucks. if you don't start moving up -> cables, headunit... if it happends only when the cars on maybe alt noise..

The reason you may not have heard it before is that sealed boxes require more power to move the sub, so the static from your amp may have been drowned out, not that you have a bandpass there is no air resistance on the vc so you can hear every detail from the amp.

the port is actually a vent that is 11 inches tall, 2 inches wide, and 7 inches deep (approx., the measurements are taken down to the thousandths of an inch). previously i had a regular vented enclosure and i didn't notice any noise. i can try pulling the rcas but im certain it is not the amp. i have a precision power. their slogan is "absoulutely state of the art mobile audio" and i agree with it 100%. im starting to think that their might be an air leak in the chamber for the right speaker. also is it possible that having gain up too high or frequency boost up too high could cause this much the same way your components distort when you turn up the bass and treble on a H/U? the freq boost on my amp has a maximum jump of 13db. i have my freq boost a little under 3/4 of the way up and my gain is about 3/4. im not quite sure where my freq is set at. that is another question i have. is there a trick to setting the freq on your amp if you have a tuned box? perhaps a formula for it? my box is tuned to 32 Hz so if there are any recommendations for setting the freq i would appreciate it.

can anyone answer my amp freq question? or is it just, turn it till it sounds good?

Well first off, there's a good chance you're clipping the amp. 3/4 gain in the first place is too high 90% of the time, and with a ~9dB boost on top of that you're just asking for trouble. In case you didn't know, every 3dB requires twice the power, so at the frequency of your boost the amp is trying to put out 8 times as much power as it is the rest of the time, which is a VERY easy to way to throw it into clipping.

And what freq are you talking about? The lowpass frequency or the boost frequency?

LP freq

start around 80, and adjust it up or down depending on how it sounds

thanks