Optimal Q for a BR-box is said to be around 0.7
I must have misunderstood something. I was pretty sure that the alignment of a BR-box would determine the Q and thus make the system possibly overdamped or underdamped.
Vented boxes are effectively 4th order, so that is two Q's in series.
If Qbox is higher than about 0.6 you'll have a hard time venting.
This is an oversimplification, and essentially useless as an aid in understanding a VB.
What are you trying to say here? I would interpret Qbox as box losses (combined leakage, absorption and port) and if Qbox is 0.6, there isn't much point at all in venting...
1) Its not an oversimplication, all 4th order is cascaded 2nd order.
2) So you completely agree, unless you want a boombox alignment.
So you won't have any trouble deriving two "real, unique" Q values for "any arbitrary" BR alignment, will you? And their combination will ultimately solve the question of what is over and underdamped in a vented box entirely, right? That's sarcasm, in case you didn't catch that...
You misunderstand entirely. What is Qbox? I interpreted it as 1/Qb=1/Qa+1/Ql+1/Qp, or any one of those on its own.
If Ql or Qp or Qb are 0.6, the box is essentially an extremely leaky sealed box, or a really lossy port vented box, which is the same as a leaky sealed.
All vented alignments can be modelled actively by two cascaded
2nd order filters because in theory that is what a vented box is.
(In the same way all sealed boxes are a 2nd order filter.)
Qbox is simply driver Q in the box if it was sealed.
I know what a cascade is.
Pull out those two Q's you talked about and show us how useful they are.
I've never seen a reputable paper use this terminology, or this concept.
Show us how it's useful!