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Old 30th November 2012, 08:35 PM   #1
Izuall is offline Izuall  Romania
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Default Resonant port...help

Hello my fellow wise DIYers...im am a big noob and i seek your asistance.
There are plenty of guides on how to build a box but very little on how to correct an existing one.
So i have this active speaker system(internal dimentions are Depth of 9.1in/Hight
13.6in/With=9.1in rear ported with a 6in long port and 2.2in in diameter the entire cabinet is made of MDF 0.2in thick)It houses a 6.5in woofer and a 1in dome tweeter.The port is located above the woofer in exact alignment with the tweeter.
My problem with it is that at @ 128hz the port starts resonating peaking at @ 132hz and gets diminshed at 136hz...how can i fix this.Please explain it to me as if im an idiot?(what are the solutions without changing the overall sound if possible or as little as posible...should i change the port ? fill the box cuz its empty if so how?)
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Old 30th November 2012, 10:45 PM   #2
Dissi is offline Dissi  Switzerland
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You say the box is empty (no damping at all) and the walls are only 0.2 inch (5 mm)?
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Old 30th November 2012, 10:51 PM   #3
Izuall is offline Izuall  Romania
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yes.
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Old 30th November 2012, 11:46 PM   #4
Dissi is offline Dissi  Switzerland
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Maybe the thin walls are resonating at 132 Hz. Examine the vibration of every wall with your hand. You should be able to feel if there is a strong resonance.
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Old 1st December 2012, 07:36 AM   #5
Izuall is offline Izuall  Romania
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Ur right the cabinet is resonating at that frq(i stuffed the ports to check)the resonance is still there even with the ports stuffed.i assumed its the ports becouse of the tube like sound i was wrong aparently...
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Old 1st December 2012, 11:32 AM   #6
Dissi is offline Dissi  Switzerland
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The walls of your box are much too thin. Maybe you can improve the stability by adding some bracing. For example a stick or a small board connecting the middle of opposite walls should help a lot.

Add some damping too. Only a 1 cm layer on walls, which are accessible through the woofer hole. Old cloths, carpet, curtain, anything will do. But leave the volume free. Pieces of an old carpet glued on some walls would be fine.
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Old 1st December 2012, 12:48 PM   #7
Izuall is offline Izuall  Romania
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Will try that..thank you very much for the advice.
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