ported box volume question

Heres the link.  I also noticed something I was doing wrong on unibox,  the port size was messing me all up. 

http://adireaudio.com/Home/ExtremisMidwoofers.htm

Correct me if I'm wrong here.  I modeled a few different sizes keeping the tuning around 33-35 and they seem like they'd be great for what I want them for.  They were all pretty flat after 70hz from 10-21L and the above tuning.  As far as 21L @ 33hz, I was just going with what the link said even though it was for a large room.  Thanks for your help.

That driver looks real good tuned to 33 Hz with 21 liters until you start looking at the port diameter vs. the power input.  It needs a 3" diameter to handle 75 watts and up, but it causes a severe port resonance peak at ~300 Hz, which is going to be in it's range.  Reducing the port diameter to 2" eliminates that port resonance but the program warns of port noise at that size.  (Be sure to check the box that says "include effects of port resonance".)

vb_response_adire_extremis_6.8-33hz.gif

A compromise would be to tune the enclosure higher, resulting in a much shorter port length... to around 50 Hz   The crossover would have to be a steep one to cross this over with the sub at 60 - 80 Hz.  Looks a bit touchy.  And in neither scenario will the port actually function for (primary) sound, because the tuning frequency will be crossed into the sub's territory.

vb_response_adire_extremis_6.8-50hz.gif

Then you look at the sealed enclosure graph and it starts to look quite good for your application!  Looks like a nice crossover to the sub using an 18 db/octave slope on the crossover and no worries about ports and port resonance.  And....a much, much smaller enclosure, as I thought the vented boxes didn't look good under 19 liters.

cb_response_adire_extremis_6.8.gif

cb_response_adire_extremis_6.8tenl.gif

Some of the Adire Extremis gurus might take a look at this too and let you know what they think.  The reason I thought the crossover may have to be steep is because of that peak in the response that has to crossed out with the sub.  I'd have to work with both the mid and sub using a crossover designer to get a better idea of what would happen, but right away it looked like a touchier crossover than it would be with the lower-tuned model.  But if I were to go with modeling alone without having any experience with that driver, I'd choose to go with the sealed.