Title sort of says it all.
What's the general consensus on loose polyester stuffing in vented boxes, for a Markaudio CHR-120 driver ?
I've built an enclosure identical in volume to this 56 liters box :
https://www.kjfaudio.com/wp-content/uploads/2020/04/CHR120-classic-vented-box-standmount-large.pdf
Yay or nay for Polyfill?
Thank you all.
What's the general consensus on loose polyester stuffing in vented boxes, for a Markaudio CHR-120 driver ?
I've built an enclosure identical in volume to this 56 liters box :
https://www.kjfaudio.com/wp-content/uploads/2020/04/CHR120-classic-vented-box-standmount-large.pdf
Yay or nay for Polyfill?
Thank you all.
not sure what BR stands for
But I take it as a nay 🙂
Thanks
I did line it with felt btw
A BR is a resonance system consisting of one resonance caused by the driver+box and another resonance by box+air in the reflex pipe/opening. The point of the BR is to add radiation resistance to the driver (less cone motion for a given bass output. Adding fluffy polyester will add a resistive component to the resonances and counteract the radiation resistance to the point that the box work as a closed box (with a leak)
With subwoofer BR it is common to have no damping material at all. If the woofer is working higher up damping is added but there is a a trade off between reducing internal reflections bouncing about in the upper bass and midrange on one hand and maximising the radiation resistance on the other hand.
This usually ends up in feltcovered walls and some BAF fibers added but with an unobstructed free volume between the driver and the BR port.
With subwoofer BR it is common to have no damping material at all. If the woofer is working higher up damping is added but there is a a trade off between reducing internal reflections bouncing about in the upper bass and midrange on one hand and maximising the radiation resistance on the other hand.
This usually ends up in feltcovered walls and some BAF fibers added but with an unobstructed free volume between the driver and the BR port.
That makes a lot of sense. Thank you for the thorough explanation.
Is it counterproductive then, to have the BR port in direct line to the driver, on the opposite/rear face of the cabinet? It seems that that would decrease the radiation resistance.
Is it counterproductive then, to have the BR port in direct line to the driver, on the opposite/rear face of the cabinet? It seems that that would decrease the radiation resistance.
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For the main function of the port it does not matter where it is placed. However, the port can have higher resonances and the box can have resonances. How and if these unwanted resonances are transmitted through the port is affected byt the placement of the port.
Having the port on the backside is a good thing as unwanted resonances are sent away from the listener. The rear port can also be a problem if the loudspeaker is (too) close to the backwall.
Having the port on the backside is a good thing as unwanted resonances are sent away from the listener. The rear port can also be a problem if the loudspeaker is (too) close to the backwall.
You can avoid those wrong resonances in a port by making it big enough so the air speed is low enough. Port on the rear is alway effected by the wall behind it, so often not so easy to use right. On the front the wall is mostly far enough to not be an issue. But the choice of front or rear ported is speaker depending and not only determinded by acoustic reasosn, sometimes there is no place on the front panel to do it or it's asthetically not wanted. Rear ported can be a solution, if the speaker is standing far enough from the backwall (what often is not possible in a hifi enviroment. down or side ported is also done btw and can also be good when used right.