Archived from groups: rec.audio.high-end (More info?)
Though this same set of questions was posted in rec.audio.tech
several days ago, I'm responding to the questions here as well.
Roscoe East wrote:
> Is there a straightahead method for determining the optimum
> volume for a loudspeaker enclosure based on a particular
> driver's Thiel-Small parameters?
Yes, if you are willing to define what you mean by "optimum."
The problem being is that optimum is a multi-dimensional system.
For example, does optimum mean maximum bandwidth, flattest
response, greatest low frequency excursion limited output,
best transient response, smallest size and so forth? Or some
combination thereof? Which performance parameter(s) are you
willing to compromise to optimize some other parameter(s)?
You may answer "I want maximally flat (Butterworth) response"
as "optimum," and then learn that the driver you have simply
can't get you there in ANY enclosure. Another driver might get
you there, but at significant cost, for example, a driver with
a Qts of 0.2 COULD be used in a maximally flat, sealed box
system, to be sure, but you'd end up with a very efficient
system with a very high cutoff frequency, most likely. After
you spent all that money on this driver with it's big magnet,
you might be justified in concluding that a sealed box system
is not an "optimal" design.
> And conversely, is there a way to determine the optimum
> Thiel-Small parameters (or, really, to select an appropriate
> driver) based on an existing enclosure's volume & port size?
Again, if you can answer the question I posed above, the answer
> And is there a way to determine how a given driver will
> perform in a given enclosure if you have all that information?
Yes, to a very great extent, especially in the so-called "piston
band" region of operation.
Recently I came upon a link to a small freeware application called LinearTeam WinISD. Its loaded with features that will allow you to design boxes for almost any driver imaginable. All drivers with VAS, Q, etc. are listed and you can manipulate box size / shape / porting and a million parameters.
Very cool stuff - and free! Here is a link to their site: