Help with sub woofer problem

So today I decided to take the stuffing out of the sub and oh boy does it help. Filled I could turn it up and shake stuff in the apt without much trouble. Now it makes the windows rattle, heheheh. But now there is a rattling in the woofer. One thing was the wires that run along the actual woofer where hitting, that was an easy fix, just force the wires away. But in the pic you can see the back part of the sub has that little mesh screen vent or something. I only call it a vent because you can feel air moving out of it. When I put my hand over it or the sub is back in the box it makes a rattling sound. Now I can only assume that vent is there for a reason so I am not putting duct tape over it although I bet that would fix it. The rattling is very noticeable so any help would be greatly appreciated.


Thank you. It’s Friday and I would love to resolve this problem by 4pm as my friends will be coming over a lil after that and I want to destroy there ear drums or at least make them bleed





only click on video link if you can help as i am running out of bandwidth. also you can only realy here the nois in the last 5 or so seconds.

thanks again

 

The vent is for cooling the voicecoil. Is it the mesh that's rattling??

 

no, just sounds like something inside, i will go listen again....but i dont think i feel it actually rattling


ok. the sub is in box it makes noise
sub out of box it is clean
sub out of box with my hand covering vent makes noise

it really sounds as if the sub itself is resonating at certain frequencies when the vent is covered or it is in a box. But the box is vented. Anyway I hope my sub is not fucked because I will be pissed.

 

So basically it makes the noise when its in a simulated enclosure. When its in the box it makes the noise and when you seal off the hole you get the noise. I would take a look at the spider and see if that is in good shape. Chances are that some of the glue might have given way and in a vacuume when it hits its just too much pressure for it to take.

You could port the box and that might work

 

box is ported

 

The screen covers the vent to the voice coil. This is for cooling.

The strange noise sounds to me like it's coming from the voicecoil. Typically the voice coil can be damaged in two ways. Mechanical damage to the voice coil can be caused by overdriving the sub and bottoming it hard. This is audible and will only happen when the sub is driven at such high power levels that it constantly bottoms out. Eventually the voice coil bobbin and/or the spider can be damaged.

Electrically the voice coil can be damaged by turning up the volume too high and over driving the amp which forces it into distortion (clipping). This essentially puts DC current out of the amp and will quickly overheat the voicecoil windings, burning the varnish which holds the voice coil windings in place on the bobbin or in the worst cases burning through the windings completely and making the woofer inoperable.

If the noise is still there no matter what the volume I think you've somehow damaged the speaker, most likely by forcing it to run at damaging levels. If the noise is there only at high volume you're trying to play it too loud.

 

200rms 400max with a 240 amp....dont see how i could have really overpowerd it. amp gets signal from a my reciever wich is putting out L & R each 100 watts but never at full volume.


nois can be herd at all valume now. I need to take it appart again and check out that spyder again to make sure its perfect. It also sounds like a rattling noise. with everything screwd back together its hard to hear unless its really thumping. to bad i like it loud.

 

everything looks perfect, but then again this is the first sub i have ever really taken a close look at.

 

Doesn't matter. You can very easily kill a 200W speaker with a mere 20W amp if you overdrive the amp and make it clip.

Speakers essentially run off an AC current which the amp supplies. Once the amp is driven into clipping by trying to play it louder than it's capable of cleanly doing you get small amounts of DC current from it. This can quickly damage the voice coil even though your speaker may be rated for much more power than the amp is capable.

If I had to guess you've overdriven the amp and damaged the varnish on the voice coil windings. The windings are now loose on the bobbin and flapping around inside the gap. The sound would be sort of like small metal shavings rattling around inside the voice coil.

 

oh i get it now. so if i where to even get this sub fixed or a new one under warrenty the amp could still **** it up. I mean shouldent an amp rated for a certain level be able to play at that level.

also the gain on the amp is usally at 3/4 1/2 or 1/3rd about for different music and stuff.

never at full.


Also what can I do to make sure this does not happen.

Ok again I think your right. I had the gain up all the way when I first took the stuffing out and it sounded great so I left it there, then I started to turn up the crossover and like normal it started to distort so I turned the crossover and gain down till I felt it sounded good. But this was for under a minute, guess that’s all it takes.

 

Amps do not make loudness, speakers do. For a given amount of power a more efficient speaker will play louder than a less efficient one. 200W of power does not translate into a certain loudness, that depends on the speaker connected to the amp and different speakers will play at different loudness when given the same power. It is safe to say however that for a given speaker a 200W amp will be louder than a 100W amp.

You have to understand what an amp really does. The amp receives a low level AC signal and amplifies into a much more powerful AC signal to drive the speaker. If you were to look at the signal on an oscilliscope the signal coming into the amp would be of some frequency and amplitude. The signal coming out of the amp would be the exact same frequency but at much greater amplitude. Power comes from the amplitude of the waveform so the greater the amplitude the more power. The amp will keep increasing amplitude as the volume is turned up until the power supply in the amp runs out of juice and is incapable of maintaining enough power to complete nice pretty waveform at their peaks. This is where the term "clipping" comes from as the waveforms no longer have nice round highs and lows; they are clipped off and flat. These flat areas are DC current and can be damaging to the speaker at high power levels.

You can make the amp clip two ways. You can attempt run the amp at higher levels than it's truly capable of by sending it an input signal that's already too high (volume turned way up) and max out its power supply which causes the amp to clip. You can do this to any amp no matter how much power it's rated for. At minimum this causes audible distorion in the sound, at worst it causes ugly mechanical noise from the speaker or damages the speaker. It also may not be the amp's fault at all. If the low level signal the amp is receiving is already clipped or distorted the amp is merely sending that same nasty signal back out, just at a much higher level. The amp takes whatever signal it gets and makes it louder. If what it gets is already poor...


True, but this is not the fault of the amp or the speaker. It's always possible to do damage if not using something correctly. Anytime you hear large amounts of distortion or strange mechanical noises turn the volume down. If the amp begins clipping you'll hear it right away as distortion. If the speaker is overdriven you'll hear it right away as distortion or strange noises from it. If you don't heed the warning things can be damaged.

http://www.sfu.ca/sonic-studio/handb..._Clipping.html

http://ftp.ec.vanderbilt.edu/compute....is.sound.html

 

well at least i know its not the reciever. I can turn it up till it hurts and the voigt pipes still sound crystal clear. so now it looks like i am going to get the woofer replaced and get either a limiter or an amp that can put out the power i want without cliping.

Learning is fun, but not as much fun when it cost money and time.

 

Assuming the amp IS clipping. If instead you've already maxed out the speaker and it's bottoming out more power won't help. If I were standing in the room I could tell you instantly what was happening

Just don't turn it up so dang loud!

 

Well from my half *** assumption of audio stuff I think it’s the amp. The sub can play loud and clear at low frequencies (high excursion), cross over at 80ish with gain all the way up and receiver loud enough to rock the house. But it then becomes distorted as the crossover gets turned up 100+Hz if I had to guess. So I am just assuming the amp runs out of power to drive the speaker that fast. Since the sub can play loud and clear at low Hz and I can see it moving a great deal back and forth (excursion) I can assume it is not bottoming out. If it is not bottoming out then then why would it at higher frequencies. Or I am wrong with my half *** logic. I looked around a few websites for limiters real quick but did not find anything. If you have a link handy that would be nice, if not no bigy I have a few weeks before I go home to ship it back and get it all sorted out.

also the amp gets very hot, not burning hot but hot. the sub never seems to get more then slightly worm

 

I have looked on a few audio sites and all over google, but I can’t find just a limiter without buying some crazy high price audio equipment or a whole new amp with a limiter.

Can you recommend something that can allow me to not kill woofer again.

I read around trying to figure out if I should just buy another amp with a limiter. This lead to me trying to find out exactly what RMS was and how it would relate to what kind of amplifier I should get. This just led to a 100 more questions. I give for now. I just want a system that is rock solid.

 

Play the speaker to the volume before you clip and set the amp gain to that. Thats the only way you can guarentee your sub will not blow up. When I use to install, I can't remember how many installs you set up and then they come back with "it sounds like ****". You check there amps and they turned the gain all the way up. Of cource it's going to sound like ****.

 

Are you only powering the sub with the amp?

 

It may just be that your box is too big for the sub. If you have too much air inside the box it will allow the sub to bottom out at a certain frequency, which usually sounds like a clicking noise. This will also happen if the sub is not sealed well in the box, allowing air to move around it, therefore being the same as a bigger box.

Although this would not solve the problem of the rattle when you cover the vent on the voice coil. One of the biggest problems with audio equipment is that there are so many components it is hard to narrow it down to what the problem really is unless you have lots of experience with it. I would take it to a car audio shop near your house and ask them what they think it is, have them listen to it. They will probably try to sell you something once they tell you the problem, but if your sub is under warranty then just tell them you will be back when you have money, or whatever excuse works for you.