Folded Horn for 2.5" Driver

[aurimasmb]

I'm trying to build a folded horn for a 2.5" driver (a satellite speaker from the Boston Acoustics BA745 2.1 System) as a sort of warmup before building a subwoofer folded horn. Unfortunately, I can't find some of the specs I need in order to get a hornresp model for the driver I'm using, presumably because these specs are usually provided only for subwoofer drivers.

The specs I do have: ????????????????

Specifically, I need to either compute or reasonably estimate:
VAS
Qes
Qms

I've read here that all other T/S parameters can be calculated by hornresp.

I'm unclear on how to get this one though...
Le

Is Fs both the resonant frequency and the cutoff frequency of the speaker?
Is it safe to take the manufacturer's spec for this from the link above? (240 zh)

Also, I read that horn calculations are reasonably accurate at low frequencies, but (presumably) not so at higher frequencies?
The frequency response of the driver is 240 to 20k hz.
Does this mean that for this small of a driver it may be simply impossible to model the system accurately enough?
Are the tolerances much smaller at these frequencies?

Thanks a lot!

 

[lcsaszar]

Don't expect too much from an unknown PC speaker. I don't think it is worth the effort, the result will be most likely disappointing. I recommend this as a minimum:

http://www.tb-speaker.com/detail/1208_03/w3-871sc.htm

Tang Bands are used in some Logitech PC speakers...

 

[aurimasmb]

Yeah I don't expect much - the project is for a CNC class, where the current assignment is to basically build anything to practice joint construction - I'm taking the opportunity to get more familiar with horn design, even if its at a small scale.

Thanks for the link - I think I'll use these as rough approximations for the specs of my driver and see what I can do with them in hornresp.

 

[OscarS]

you can measure all the pertinent T/S parameters via signal generator, voltmeter, resistors, etc. The methodology has been in place for decades. A simple google search will yield great results if you don't already have the Loudspeaker Cookbook.

 

[picowallspeaker]

I guess you haven't read http://www.diyaudio.com/forums/multi-way/208799-western-electric-1928-how-far-have-we-come-last-100-years-104.html
as ( as I understood ) the horns were made for the very specific driver, which
have different characteristics from regular Dynamic Drivers .
Indeed they don't necessitate of an impedance adapter device