Cube (and spherical) enclosures are obviously undesirable from a standing wave POV but can the resonances be supressed by a combination of driver placement (offset from center) & port placement (center placement with port entrance at the center of the cube)?
Why a cube, because subwoofer MDF box kits of various sizes are available, oblong boxes not so much.
Also appreciated, any insight into the best placement of sound absorbing stuffing?
Why a cube, because subwoofer MDF box kits of various sizes are available, oblong boxes not so much.
Also appreciated, any insight into the best placement of sound absorbing stuffing?
Yes, it is the odd concept of "piling up", in that...take your cube & adroitly measure the distances from the cone inside towards a surface, we will note all the distances are the same...even if we bounce off multiple surfaces!
As such those internal waves of pressure all arriving back at the same time will conspire to set in motion the cone as if like a microphone. The simple act of offsetting the driver as to not be at its exacting center will kill those "return times" of the internal pressure waves. Now, if we have, say a five-inch driver, and an enclosure that is only eight by eight inches, the offset value is limited....a twelve by twelve size gets us a better offset ability.
Look at an image of the Infinity Qb speaker...lots of math crunching to offset its drivers to minimize internal standing waves.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
As such those internal waves of pressure all arriving back at the same time will conspire to set in motion the cone as if like a microphone. The simple act of offsetting the driver as to not be at its exacting center will kill those "return times" of the internal pressure waves. Now, if we have, say a five-inch driver, and an enclosure that is only eight by eight inches, the offset value is limited....a twelve by twelve size gets us a better offset ability.
Look at an image of the Infinity Qb speaker...lots of math crunching to offset its drivers to minimize internal standing waves.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
A cube gives you a higher frequency start to the standing waves. First check they are out of the sub's range.
Ok. Driver and port placement may not be very helpful. Stuffing at perhaps 30% or more in each dimension is a good place to start for the inside of the box. Rounding might benefit the outside.
I built a folded transmission line into a 2 ft cube, and with judicious lining with acoustic fibreglass was able to get a very usable set of speakers, with a very flat bottom end down to 50Hz.
I made myself three cabinets from cheap 12mm (1/2") chipboard for a W4-2142. A CB with external 141mm Wx 180mm Hx 222mm D, a folded TABAQ MLTL and the folded TABAQ as tapered TL with the same port size. Without stuffing the MLTL has clearly less unwanted midrange output from the port compared to the tapered version.
The W4-2142 got a 12dB HP @150 Hz and I played with stuffing from 0 to 100%. To my ears the folded TABAQ totaly stuffed (aperiodic, basically no output from the port) sounded considerably cleaner than the CB. I think the CB doesn't have room for enough damping material to kill the internal sound. For a midrange the aperiodic MLTL is my favorite. If you need output from the port you have to make a compromise.
In theory you don't need any stuffing for a subwoofer, for BR and TL usually there is little stuffing between driver and port. As you know everybody has different taste/opinion, therefore playing around with cheap test cabinets tells you what is important for you.
The W4-2142 got a 12dB HP @150 Hz and I played with stuffing from 0 to 100%. To my ears the folded TABAQ totaly stuffed (aperiodic, basically no output from the port) sounded considerably cleaner than the CB. I think the CB doesn't have room for enough damping material to kill the internal sound. For a midrange the aperiodic MLTL is my favorite. If you need output from the port you have to make a compromise.
In theory you don't need any stuffing for a subwoofer, for BR and TL usually there is little stuffing between driver and port. As you know everybody has different taste/opinion, therefore playing around with cheap test cabinets tells you what is important for you.
Given this bit worksa on the air as a slug, little difference.
Making the inside not like the outside is a good trick, oldfi approach quite logical.
A mass of damping at the middle of the cabinet with more thruout…
dawe
Last edited:
Yes.
The other point about placing the driver at one edge of the cabinet can make the response look good on axis, but it may differ from the general balance. Keeping the driver in the middle of the baffle but rounding it helps extend the baffle step lower, and if done right may produce a more consistent polar presentation.
The other point about placing the driver at one edge of the cabinet can make the response look good on axis, but it may differ from the general balance. Keeping the driver in the middle of the baffle but rounding it helps extend the baffle step lower, and if done right may produce a more consistent polar presentation.
Last edited: