FAST: Aperiodic or Folded TQWT

[ljfont]

I just got a pair of CSS EL70eN and Alpair6p from my last visit at CSS. (Thank you Bob)

I'm looking to build a FAST two way with a removable supra baffle for both full range speakers. I think the Alpair6p will be better with aperiodic and the EL70eN at folded. I have CSS SDX7 as mid bass and will use it sealed.

What determines aperiodic or folded TQWT? Which T/S parameters should I be looking at?

Thanks.

[planet10]

Aperiodic is used when:

1/ you have a driver with too high a Q that you want to put in a box and knock back the system Q as much as possible.
2/ you want to remove (most of) the back wave. Usually in this case an aperiodically damped TL (i use these for midTLs in FASTs)
3/ you want to minimize the size of the impedance of the resonant peak

These are not mutually exclusive.

ML-TQWT (i prefer ML-Voigt), toincreasequanity of bass.

You don'twant to push the A6p at the bottom too much, it is a small driver, and you'll limit its midrange magic.

EL70eN (you must have gotten 1 of the 2 pair i did up for Bob) has substantial bass capability -- there is a good ML-V for it -- and the ML-V will work to maximize that.

In a FAST the bass capability of the ML-V would be lost, so there is not much point. If you are trying to meet up with a true subwoofer below 60 Hz it would be worthwhile (but that is not an SDX7)

There is a minimum modification that i highly recommend for the SDX7, it is pretty simple and very effective. A few of the SDX7 Bob has had i have done this mod to.

dave