4412 woofer problem

[mimo_proshol]

Investigating the lack of bass in my system, i've noticed: when tapping slightly on the woofers they respond differrently. One with "boomy" sound, another - much quieter thud. I've examined that one in and out. It has no visible damage. Cones, foaming, etc. - everyting's identical and looks perfect, but seems to sound differently. Any thoughts, what is the problem and how to cure?

[Eaulive]

Is the compliance the same on both woofers? Meaning, when you move the cones do you feel the same resistance?
A difference in sound can also be caused by a different electrical loading of the woofer, if the coil sees an open or a short circuit, it will sound different when you tap on it because of different damping.

[mimo_proshol]

Is the compliance the same on both woofers? Meaning, when you move the cones do you feel the same resistance?
A difference in sound can also be caused by a different electrical loading of the woofer, if the coil sees an open or a short circuit, it will sound different when you tap on it because of different damping.

My fingers are not sensitive enough to feel the difference.
The "tapping responce" sounds different even when no wires attached. Measured resistance is about the same on both monitors.

[DavidF]

My fingers are not sensitive enough to feel the difference.
The "tapping responce" sounds different even when no wires attached. Measured resistance is about the same on both monitors.

Any reason to think that the coils may have been overloaded? High output from the amp or a recent amp failure?

Best thing is to pull the suspect woofer. Using light touch with both hands use push on the back of the cone. Checking for any resistance to movement. You have to keep in mind that even a small amount of rocking the cone can cause the voice coil to get out of alignment and rub, so go easy. You may even pull both woofers to get a sense of any difference between the two. The woofer cone should move freely without any dragging or any noise that suggests rubbing.

A short cut would be a quick battery test. Saves you from pulling the woofers initially and could show a displacement problem. I would rather you pull the woofer, though, since a jolt to the coil may not be the best thing unless you know if the driver is OK.

[mimo_proshol]

It seems to be a problem with cabinet. When swapped woofers, the "tapping response" remains the same in the same speaker. Also the cabinets look flawless from outside:confused:
May those invisible cracks have such a huge affect on bass output?
No signes of coil problems detected.

[ivica]

It seems to be a problem with cabinet. When swapped woofers, the "tapping response" remains the same in the same speaker. Also the cabinets look flawless from outside:confused:
May those invisible cracks have such a huge affect on bass output?
No signes of coil problems detected.
Check vent tube, may be.

[pos]

Both channels pluged to the same amp?
Also try the same test with the woofer unplugged (damping from the amp, filter, etc...)

[DavidF]

Both channels pluged to the same amp?
Also try the same test with the woofer unplugged (damping from the amp, filter, etc...)

Hmmm, good thought. Could some excess DC from one channel of an energized amp be causing some problems?

[Eaulive]

He said he tried it without wires attached, same difference.