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Subwoofer normal noises

blackfly

blackfly

Fidelius Claritus
This is a bit of a perplexing question for me.

I own 2 JL Audio f113's, and have had them new since March. No issues whatsoever.

I get the bright idea of using a subwoofer test signal from a Delos test disc I have and it cycles down the frequencies from 120 to 20. By about 30 hz my subs start making noises, other than the frequencies. The cones themselves start making "rattling noises". It sounds like a machine gun at the 20 hz frequency. Both do this but one moreso than the other but not by much.

Is this normal? Any ideas anyone. They are under warranty and I did buy from an authorized shop AND I have the boxes. Can anyone convince me this is normal and I shouldn't be worried. Maybe it is normal?

I did play Zarathrusta with the 20hz note at the start and both cones (one more than the other) and I could hear some rattling, not much, but it is definitely the cone.

I find it hard that both could be defective or I was hosed (why would I, I have warranty) but does anyone else have a similar story/experience, especially with JL? I am in no rush to get them out but my feeling is both are "defective". I hope not but I think so.

Any car buffs with JL out there have any thoughts?
 
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My guess would be that overexcursion is causing the cone to misalign which is making the voice coils rub.
Just a guess but in that case it would be normal.
 
Amp. box may be rattling?

Many sub units have a plastic "box" that houses the amplifier unit and this box is just inserted into the back of the enclosure of the main speaker box.

This combination of "boxes" may cause the back wall of the amp. box to vibrate and make "unmusical" noises.

My unit is not new or under warranty, and I fixed the problem by screwing\gluing a piece of plywood to the back of the amp. box and reinstalling it back into the main box.

You might try and see if any of the existing screws are not quite snug and tighten them (don't slip, you may void your warranty!)

ALSO! Plug your sub into a switched outlet, just because it "turns on" when sound is present, the main power supply probably does not shut off and the capacitors will be likely be dried out rather quickly with it plugged in "24/7".

Mark T.:music:
 
I don't own JL's (and they might have specific issues with the cones) but I have had experience with over-excursion and power damge using a test CD. I managed to melt the spider off the cone of an ID subwoofer using too much power and very low sweeps.

The JL W7 cone is actually two cone materials bonded together at the perimeter and center. I would imagine that it is very easy to have these two cone materials in resonance using all the power available and reproducing very low tones. That could be the cause of the rattling that you are experiencing. If you have this rattle with normal listening levels, I'd suggest you use the warranty and replace them. They may be defective or may have suffered some damage.
 
Thanks all. They are NOT in overexcursion. They have 4 inches total travel and I am NOT at high volume. If I were I would no longer need them. They are designed to be the "ultimate" at the lowest frequencies. But the suggestion about bonding the cone..... could be.

I am going to send each to get checked, but one at a time. Hopefully this is not too involved. I think I am going to arrange for pickup.

What is more scary is the fact had I REALLY been driving them hard I might understand but I have 2 f113's in a 16x12x8 room, not like I CAN overdrive them without the room rattling so badly.
 
Are the drivers easily removable? If so, look for wire, or box stuffing too close to the back side of the driver (had this happen to me with the wires to the speaker touching the back side of the cone). Also, sometimes driver can rattle if speaker baffle is warped or screws overtightened. See if driver still rattles when removed from cabinet. Careful not to overdrive when drivers are out of the cabinet. YMMV.
 
Blackfly, did you get your JL Audio F113 rattling noise resolved? I have the same issue with my F113. It's more noticeable in Transformers 2 (2007) at the very beginning of it. Thanks.
 
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