Why does my RolaKC550 speaker rattles - Roland KC550 Amp Keyboard

May be a couple of things; The first is a resonance in the cabinet, which may not be noticeable at high volumes. If the speaker cabinet was ever dropped,or got cracked from dropping , dry weather,or whatever, there may be certain frequencies that make the cabinet rattle. Try holding the cabinet when it rattles and look for anything loose,from a side wall to a loose foot, or the speaker itself. Tighten up loose items and seal any gaps or cracks On the cabinet.
The other problem could be a partially blown speaker. Test by lightly pushing in on the outsides of the speaker to see if it moves in and out freely. If there is a scratching sound, or it drags slightly , it might be blown. Also,the dust cap or another part of the speaker may be loose. Check that, and reseal if loose. Replace or have reconed if blown.

Pay attention to the source of rattling, if its just the enclosure or comes out from the speaker and let me know to improve helping you out...

Hi,

Please specify a bit more, does the rattle is physical(Enclosure structure) or electronically hear thru speaker(Power Amp Common Issue)? I have the solution for the amp issue, let me know.

The noise MIGHT be a resonance in the cabinet. The way to find out is to sweep a frequency upward to see if something rattles at certain frequencies... Don't be surprised to find several. Within the cabinet are the usual culprits: Wires rattling against the cabinet, loose debris, grilles and the logos on them, circuit boards with crossover hardware, cabinet wood that is not glued and rattles against itself. Things like bass port tubes can rattle.
Find an audio generator and sweep the cabinet from 50Hz to 10KHz and you will be surprised. Some speakers may have resonances as well. Expect things in your room to start rattling as well.
This is really the only way to find the problem. PLEASE wear hearing protectors at levels above 90Db.

There could be a small tear in the plastic liner over the speaker. If thats the case you can try pressing some cotton on it and then put the grill back in place, or find some fabric glue and glue a thin peice of fabric over the tear.

If this is a brand new unit, exercise your warranty!

BUT FIRST see if packing material worked through the speaker grill... you know littel pieces of the packing peanuts or otherr contamination that sits in the speaker cone and rattles.

Way to find out: The minus speaker leads go to ground at the amp and therefore are electricaally connected together... just use an ohmmeter to find which two wires are tied together and connect those to the minus leads of the speakers.

The cabinet is listed as a 4 ohm unit.

We would exoect to see four, 4 ohm speakers in series parallel or four 16 ohm speakers in parallel.

If teh unit seems to rattle, first put an audio oscillator into it and sweep the frequency. It is common for grilles and also logos attached to them to rattle.

Open the unit and power each speaker the same way individually for a test.

I suspect you will find either the grille or mounting hardware is actually doing the rattling OR possibly the wires inside are vibrating.

If the sound is a scratchy buzz, then the speaker(s) have probably had voicecoils damaged by overheating.

In this case, buy 4 new speakers and replace all. It is not likely to find replacements for the Buggera brand they put in these cabinets. Also the word on the web about that brand of speaker is not very good.

NEVER disconnect a speaker with the power on the amplifier !!!!!! Good way to blow the amplifier.

If the speaker rattles while you are sending audio through it, it is likely damaged. It should be inspected as there are several failure modes, some of which as hazardous to your amplifier.

First test is to gently move the cone and listen for any rubbing of the voice coil. If you hear rubbing, then the speaker needs replacing OR re-coning.

Sometimes the magnet breaks off the back of the speaker.

Investigate this before further use.

Check for loose mpounting bolts of the speaker itself. One unit I found had a Tolex covered back closure that was vibrating. Had to put a cleat in to secure it to the wall below it. Also check for wires that are unsecured.