onken-like enclosure with 'folded' ports to gain length

An ebay seller from Taiwan is selling some "mini" "Onken" cabinets for 4" fullrange drivers that have one interesting feature I have not run across before in reading up on Onkens (I have been reading a lot about Onkens, because I am intrigued and considering an Onken configuration for a future build):

The unique feature is that the ports fold back on themselves into the main inner part of the enclosure, to gain more length than is possible with the "direct" depth of the enclosure's sides. That additional pair of vertical pieces that create the innermost fold would also seem to increase rigidity of the top and bottom of the enclosure.... Picture attached

This seems very ingenious - is there any drawback that'd suggest why I am not seeing this in other designs or discussions about Onkens?

Also, the seller claims that this cabinet is optimized/adaptable for a wide variety of 4" fullrange drivers - is that even plausible? Seems appealing, but too good to be true...

Appreciate input on the above, especially whether there's any downside (other than complexity) to the "folded" vents. Thanks!


  • Mini Onken with extended vents & bracing.jpg
    Mini Onken with extended vents & bracing.jpg
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Folding slot vents isn't especially unusual in itself; I've seen several examples of this in Japanese enclosures in the past.

No particular reason other than, presumably, a lack of necessity; it will likely only tend to occur when small box volumes and low tuning frequencies are required for the desired alignment, which then raises the issue of self-harmonics (vent ducts are 1/2 wave resonators).

Optimised for a wide range of drive units? No. Adaptable? Possibly, assuming their load requirements fall within reasonable limits.