vibration coming from speakers

Hi guys, long story so I will start with the symptoms. Polk audio MM 6501 components installed in the front door of my 2011 genesis coupe. Noticed a rattling when bass hits. Pulled the woofer out of the door and found the vibration is coming from the speaker itself (left and right woofer). Only happens at moderate to high volume. I have had 3 pairs do this to me so far. The 4th is in the mail. The noise sounds like it might be the spider, as I hear it from behind the cone and also from behind the magnet structure.

In an attempt to troubleshoot it, I pulled each woofer to the back of the car (where the amp is: Boston Acoustics GTA 1105) and ran a wire directly from the amp to the speaker. Still happened. Tried in each channel of the amp and it still happened. I have the Polk MM 651 coax in the rear and have no problems at all. The speakers are 2.7 ohm and handle 100w RMS each side. The amp goes up to 125w x4 in 2 ohm. The amp is only turned up 1/3. The high pass crossover was at 60 hz to start. I can make the noise stop at 150 hz. But that is way too high a crossover point. There is no bass boost. The EQ on the stock deck is flat. I tried running the amp with speaker level inputs initially (as it can be) and thats where I heard the noise. So I figured maybe a decent line out converter would help. So I have the Cache coe6. Now I have RCAs to the amp. Still happens.

The vibration does not sound like clipping. I made the rear coax clip when tuning them and that sounds very different. I have already found the best ground (seat belt bolt) and have no ground noise. The noise happens if the car is running or not.

Any advice would be greatly appreciated.

Adam

Use the 150 Hz crossover setting and use a subwoofer to handle the deep bass. Make sure that the woofers are completely sealed to the door. If any air in front of the speaker can meet air behind the speaker, the cone will move too much (over excursion) and distort. The speaker will destroy itself at higher volumes. The air inside the door acts like a spring to load the back of the woofer.sparky

Hey Sparkie. Thanks for the input. Its gonna be tough to seal the door completely. There are drains in the bottom of the door that I prolly souldnt plug up. I never thought that the speaker running free air would cause the noise. It is certainly something to look into. Maybe a pre-made speaker baffle (not the foam ones, they rattled when I had them in the past).

Maybe I will build a small box to see if over excursion is the culprit. If the box is the right size, it shouldnt allow the speaker to move so freely.

As for the 150 Hz...I really dont want to go that high on this. The specs on the drivers say 40-20k Hz. I think 80 Hz is a reasonable expectation. Again, maybe sealing the speaker in a box will solve the problem.

Thanks again.

Will post again with results soon!

definitely sounds like you have too much bass playing through the speakers. and the fact that this is the 4th pair to do this to you that supports this idea. i think the new polk MOMO series is supposed to be shallow design which means they will usually have less movement in the cone. it could also be the cone slapping the basket. you dont have to have the crossover so high if you can bring yourself to turn the bass down on the eq, just because its on flat doesnt mean it couldnt be lower.