B460 -2245 rattle ? need advice!

[mrbluster]

Hi,

I've owned a B460 subwoofer for about a year and it has run with no problems until now. It has been sitting for about the last two months without use. Today I tried hooking it up to a new amplifier (to see if I like it) and I heard a distinct rattle as though the voice coil was misaligned. Didn't want to push it but I tried a second amplifier (same type) with the same results. I put the sub on its back and have carefully moved the cone up and down. I don't feel any rubbing. Surround appears fine (don't know if it's original). Any assistance would be greatly appreciated.

Thanks.
mrbluster

[Zilch]

Play it on its back. Does it still rattle? If not, rotate the 2245 speaker 180 degrees. I'm thinking "sag" here.

While you have the driver loose, remove any cat toys found inside the cabinet....

[boputnam]

Hey, mrbluster...

Your instinct is / was good - to try and move the cone by hand and repeat the bad behaviour. That may not be entirely relevant, as you will have difficulty being as uniform as the magnetic field.

However, I've found that many noises like you describe can be mechanical/physical but not in the gap. Could there be a loose joint or something in the cabinet? Is the 2245 tight in it's mounts? You might remove the 2245 and see if it occurs in free-air (althought this might not be too informative, either). And, inspect the cabinet for any possible sources.

Let's see what others suggest...

[mrbluster]

Thanks for the quick response. I am a little upset about this. Tomorrow I will play unit on its back and regardless of the result remove the driver and report back. Mounting looks alright to me, but I will pay attention to that as well.

Thanks for the help!!

mrbluster

[Robh3606]

If you can try a sine sweep. You should be able to get a better handle on where the rattle is coming from. Nothing crazy just low level and slowly work up until you hear the rattle. Hopefully it's just a loose screw somewhere and not the driver.

Rob

[mrbluster]

Well here's what I did. I laid the unit on its' back checked the mounting and tried an old tube signal generator. At first, I drove the unit directly, with no problems, then I added the amp and BX63A and the noise returned(mostly around 25-30HZ) . I removed the mounting hardware intending to look inside but since the 2245 was reluctant to come out, I decided to leave it for the next day. In the mean time I listened to the "New" amps I was auditioning, A pair of 1980s' Kenwood L-07MII mono blocks, and found them to be a disapointment to say the least. The next day I got the bright idea to do some more testing before I pulled that monster out. I used one channel of a 200 wpc denon stereo amp, figuring it had a least as much power and dampening as the kenwood, and repeated the tests. To my suprise and relief no rattle (or whatever it was) at all. I then returned the mounting brackets and set the b460 back on its' feet, tested again, with the same happy result.
I do not really know how to interpret the results? Thanks to all who came to my aid, and would love to hear what you think of all this. In the meantime the kenwoods are on their way back to the store.
Mrbluster.... P.S. Any thoughts on putting a Sub1500 in an olympus box?

[Zilch]

Originally posted by mrbluster
P.S. Any thoughts on putting a Sub1500 in an olympus box?

Olympus is 6.0 cu.ft. by my empirical calculations. Several regulars recommended that size box in the Sub1500 threads, tho smaller seems to be favored.

Glad you found the problem, and that it wasn't JBL, BTW....

[scott fitlin]

Originally posted by mrbluster
Well here's what I did. I laid the unit on its' back checked the mounting and tried an old tube signal generator. At first, I drove the unit directly, with no problems, then I added the amp and BX63A and the noise returned(mostly around 25-30HZ) . I removed the mounting hardware intending to look inside but since the 2245 was reluctant to come out, I decided to leave it for the next day. In the mean time I listened to the "New" amps I was auditioning, A pair of 1980s' Kenwood L-07MII mono blocks, and found them to be a disapointment to say the least. The next day I got the bright idea to do some more testing before I pulled that monster out. I used one channel of a 200 wpc denon stereo amp, figuring it had a least as much power and dampening as the kenwood, and repeated the tests. To my suprise and relief no rattle (or whatever it was) at all. I then returned the mounting brackets and set the b460 back on its' feet, tested again, with the same happy result.
I do not really know how to interpret the results? Thanks to all who came to my aid, and would love to hear what you think of all this. In the meantime the kenwoods are on their way back to the store.
Mrbluster.... P.S. Any thoughts on putting a Sub1500 in an olympus box?

Sounds like the Kenwood amp did not have good enough control over the woofer at very low frequencies, and possibly allowed the cone/voice coil to move slightly sideways when being driven, and this would cause the rattling noise you heard!

[GordonW]

Sounds to me like either an output transistor problem or a power supply problem with the Kenwood amps. Some way, you were getting artifacts in the waveform in the outputs... probably little "spiky" things as either the power supply ran out of gas (possibly on just ONE rail, and not the other, which would make the wave asymmetric) or one output laid down (same result).

I'd agree... I'd immediately return any amp I had just bought, that exhibited that problem. That's one can of worms I wouldn't want to be involved in.

Regards,
Gordon.

[mrbluster]

Kenwood Amps are on their way back. They sounded just passable through a full range speaker. Not what I expected. The strangest thing though is that "both" examples exhibited the same "artifacts" when used with the B460. Glad I was able to get to the bottom of this problem before they did any damage!
Mrbluster