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Sub "ring"


BaBaLoO

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Hey guys, so here's my ordeal: I have a 12w6v3 in a custom ported box powered by a Rockford 1000/1 and have a wetsounds 420/bt eq. Never really had an issue with the setup other than the sub wouldn't kick randomly but I figured that part out last year. Tried it out for the first time this year a few weeks ago, and noticed that I have a little "ring" almost like something is loose. I already went over most of the boat to look for loose fasteners and the ring is still there. Took the sub out of the box to see if anything was loose and it was all good. Disconnected my rca's and installed again, same issue. It is very minimal but I know this is going to annoy me all season if I don't figure it out. It seems to only happen at lower frequencies. Could it be the amp itself? The amp? Something loose that I haven't found yet? look forward to hear your input. 

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So to try and isolate the cause I would first divide the issue between a) sub/enclosure and b) boat parts becoming excited.

Starting with the sub/enclosure. Verify that the enclosure is absolutely airtight other than the port tube (terminal cup, woofer mounting holes, etc.). Try temporarily sealing the enclosure port airtight. Try raising the crossover frequency. Eliminate any form of bass boost or bass equalization. At the enclosure/port tuning frequency the woofer should move at a minimum. Below the tuning frequency the woofer moves to excess, and a subsonic filter can help with this.

If the problem is a particular boat part getting excited and resonating from the sub, then you can use a frequency sweep to isolate that certain frequency. Then you can move around the boat and apply firm pressure to various panels, parts, and junctions. However, you can easily smoke a speaker with a sine wave, so keep the gain level down and below full output during any kind of test.  

  

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Thanks David I'll try that. The box is vented, not a tube, not sure if that makes a difference. I'll try it out on the water tomorrow, so your saying to just play with the frequency on the amp with all gains turned down and play with it? Right now the frequency is at about 35-40hz. Cover the vent while the sub is going?  

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1 hour ago, BaBaLoO said:

Thanks David I'll try that. The box is vented, not a tube, not sure if that makes a difference. I'll try it out on the water tomorrow, so your saying to just play with the frequency on the amp with all gains turned down and play with it? Right now the frequency is at about 35-40hz. Cover the vent while the sub is going?  

Which frequency is 35-40hz, the enclosure/port tuning frequency or the low pass crossover frequency?

Just find a way to temporarily 'seal' off the vent. Curious as to the vent dimensions?

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The box is tuned to 33hz based on the dimensions JL gave me, I can't remember the dimensions but I'm sure it's in some of my previous posts when I was trying to make the box. The crossover frequency on the amp is at 35-40hz I believe. Any possibility that the amp itself could feed that noise? Again, it only seems to happen at a certain "tone" of the sub. 

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Well 35 to 40 Hz low pass would be way too low if that is really the case. No guarantee, but that could be your issue. Essentially that would be placing two filters at the same frequency leaving the sub as a single note resonator and making the sub and amplifier work inordinately hard in order to produce any perceived output. The low pass frequency should be much, much higher. Btw, as you raise the low pass frequency, be prepared for the output to increase substantially forcing you to turn the amplifier input gain down.  

Edited by David
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