Possible problem with PRX718s

[DJ Spek]

Hey guys. I just bought a brand new pair of JBL PRX718s's. I have a small problem with them, but not sure if this is normal. Whenever there is a kick or deep bass, i hear i high pitch rattling(not too loud from far away) that sounds like it's coming from the grill. Any ideas?

[soul-x]

 

Any ideas?

 

 

Put your hand on the grill to dampen it for confirmation of your suspicion?

[DJ Spek]

Yeah, i tried that, but no difference :/

[soul-x]

 

Yeah, i tried that, but no difference :/

 

 

Remove the grill and try again? Look for rattling other places?

[DJ Spek]

Could it just be the air doing something weird? I just don;t want to take the grill of since they';re only a few days old.

[DJ Spek]

and they're on carpet, if that makes a difference...

[Mogwix]

 

Could it just be the air doing something weird? I just don;t want to take the grill of since they';re only a few days old.

 

Don't know how to use a screwdriver?

 

Take it back to where you bought it and try to replicate the problem.

[agedhorse]

What are you driving it with, and where is the input level control set on the PRX sub?

[DJ Spek]

Input is at 9 or 10 o clock. It's not near the limiting light being on. It's being driven by a presonus firebox(firewire soundcard)

 

@mogwix: I don't have very much time right now so i'll take the grill off later...

[gspointer]

Any chance it is something in the room?

[Bobby1Note]

Are you sure the rattling is coming from the sub itself? Have you looked around the room to see if the low frequencies are causing vibration somewhere? Maybe a glass table-top, a nic-nac on a shelf,,, that kind of thing.

[agedhorse]

Bring the level up to 12:00 and back off on the input to the soundcard. You may be overdriving the signal before the sub itself. Just an educated guess.

[DJ Spek]

Thanks Andy! I'll give that a shot tomorrow and let you know how it goes.

 

I'm almost completely sure it's not something else rattling in the room.

[abzurd]

Could also be the amp module rattling. listen for it there. If there are screws visible, see if they are tight. Have that problem with my Yorkville NX550P tops and LS700P subs.

[DJ Spek]

@agedHorse: Just tried turning the gain up on the speakers and down on the sound card, but same result :/ Could it be the foamy sheet that lines the grill?? It's so weird that it's happening on both brand new speakers.....

[agedhorse]

Can you try the same setup on a different pair of subs? This is not a typical problem. Are you using the internal crossover (any way it's bypassed?)

 

You might need the help of your local JBL service guy to troubleshoot this, it may not be obvious and sometimes it's worth getting an expert involved before heading down the wrong road.

[JoeDirt]

Are you 100% positive it is the cabinet? I also have two PRX718S and they are rock solid and don't make any rattles.

 

But they do cause quite a bit of rattles in my basement where we practice. A ton in fact.

[agedhorse]

Try this outside just to be sure it's not in the room. It's really hard to localize a rattle inside a room.

[jgthatsme]

This past weekend I heard a rattle coming from one of my subs. It was the loose fitting sub/sat pole. Waiting for the "good" ones to be available from USS.

[jwlussow]

 

This past weekend I heard a rattle coming from one of my subs. It was the loose fitting sub/sat pole. Waiting for the "good" ones to be available from USS.

 

 

Good point. I forgot about that noise. I ended up putting a single layer of gaffer's tape on the pole and the noise stopped.

[DJ Spek]

I finally took them outside, and same problem. I just sounds like something very light is vibrating.... Any ideas?