subwoofer damping using soundproof sheets

[dannyjmf]

Another subwoofer project here ... tuned to 35Hz ... having resonance problems around 120Hz region somewhat like vibration/ringing issue seems like coming from the port ... i found a new idea to tackle these problems that is using sound proof sheets/dynamat and line them around those problematic sections (the panel top that sits along with the driver) and another problematic one which is the front panel with the dual ports ... and also some will be applied on to the port surface to add rigidity and some around the large area panels inside ... next will be some polyfill from pillows and another pillow act as a volume reducer ...

will this trick using dynamat or equivalent will work to cut down those nasty resonances? or they help little or no effect ... the box inside was full of bracing and it just would not get rid of the 120Hz glare/resonance ... thanks

 

[weltersys]

Mohamad Danny Al Saleh,

Adding polyfill will reduce overall output level, adding Dynamat would lower the resonant frequency of walls.

Wall resonances at 120Hz normally would not be heard through the ports.

You wrote "the box inside was full of bracing", all that is visible is a single cross brace, not adequate to stiffen the walls, and likely the source of transmission of side panel resonance to port rattle/120 Hz noise.

Some foam rubber between the ports and the x brace, and securing the "X" cross might eliminate the "vibration/ringing issue coming from the port".

Art

 

[dannyjmf]

ok since the materials were already bought ... time to apply them ... the front panel with the port was treated with 4 layers of sound proof meanwhile the rear panel receives 2 layers of soundproof and supported by a pillow ... another pinewood long block used to hold the pillow down ... rear panel received 3 layers and sides 2 layers ... after that polyfill was added ... towards the rear panel they were heavily stuffed but quite empty behind the driver and around the port ... there were also some polyfill around the port area and the front and the port were wrapped with some soundproof sheets as well ... as you mentioned the brace close with the port i did something to it added some sound proof layer and isolated them ...

the picture with polyfill is the first trial and error with too much filled inside and later was removed (not in photo) ... results huge improvement with these 3 materials as enclosure treatment ... the 120Hz resonance vibration has gone away and the sound is much more solid now ...

i plan to use the idea of soundproof for full range speaker box and for any future large subwoofer box design with 4 to 5 layers each panel ... will they be beneficial? thanks