Unibox and midranges...

[zimjj]

I'm contemplating a 3-way and have been fussing with several mid-ranges. It seems that unibox prefers vented, at least for the ones I selected. When I go to unibox I can get perfectly good-looking performance in a closed 2.0 liter box. If I got to vented I have to go to a box twice as large, or more, to keep from getting huge 'jaggies' when I turn on port resonance, plus there is always a huge hump at the selected Fb and there's the extra work of fitting another port.

It seems to me much more practical to go closed, and I wouldn't be asking advice if it weren't for the fact that I'm thinking of emulating (not duplicating) one of Troels Graveson designs (Poor Man's Strad), and he specifically said he wanted the Mid vented. He uses a SEAS Prestige Mid and I'm thinking of going with SB Acoustics (for all drivers).

Do you think his desire is based on the mid he used, the baffle design (very wide) or he just prefers the sound of a vented mid.

Any insight would be appreciated,

JohnZ

 

[DcibeL]

From Troel's site:

The mid cabs are 4.3 litres net volume and the vent is a 40 x 70 mm PVC tube with an ID of 37 mm. Actually this vent doesn't do much in the traditional way of a vented box. I made it because the mid shouldn't be in a closed box.
I don't dig closed boxes for larger midrange drivers! It kills the midrange. Actually I have a small amount of wool material stuffed in the vent, so its function is more like an acoustic vent. So take your pick.

And the mid cab vent is on the rear panel (I've had that one too 🙂)

The mid cabs aren't really vented, more like aperiodic damping.

IMO, The decision for a sealed of vented mid cab is mostly based on available excursion and bass depth. Since a mid is usually crossed over at >300Hz, a ported cab should not be necessary. Moving to a ported cab will make group delay and transient response suffer a bit, so be sure to look at the graphs, and decide what is best for your design.