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Sub unload or?

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I been woundering if the location i have the ports for the 4th bp could cause unloading or some other issue? It sounds great, but when turning the volume to where i set the gains on the amp to (conservatively), im getting some distortion or some knida odd noise. Attached a sketch of the box.

Gains set useing -5db test tones and headunit was no distortion.


2 12" skar evl, skar rp1200.1

Top chamber is ~3.5cu ; bottom is ~1.8cu

Ports: 2   4"x15.3"


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Ok, so there are two BIG problems with your ports.  The first is that you are tuned way too low.  For a bandpass box you should be tuned somewhere between 40-50 Hz, you are tuned to around 32 Hz.  The second problem, and this is probably what you are hearing, is you have way, WAY too little port area.  Your two 4" ports have about 25 sq in of port area,  based on the specs of your box and the power you are running you should have more like 60 sq in of port area.  

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I also gave the gross vol to top chamber by mistake, net is ~3.2cu so the port length lines up. I really wanted to do a square port. I have bass box pro so ill figure something out.

Thanks for ur input @Triticum Agricolam

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