PeteMcK said:
It's not clear to me what 'narrow' & 'broad' output is....
How wide its gain BW is. The object of a driver cab is to boost the driver's BW below its mass corner, i.e. its point source BW or where the driver's response starts to roll off (Fhm). The lower its Qts (stronger motor), the higher in frequency (Fhm) the roll off occurs, ergo the more gain BW the cab must handle for a given Fb (Fp, Fc).
Since short of a large compression horn there can only be so much cab efficiency, it stands to reason that as Fhm rises, so also Fb must rise for a given response curve and why low Qts drivers tend to require small cabs tuned high for a T/S max flat alignment with high Qts drivers needing large cabs tuned low.
Anyway, TL loading causes 'ripple' in the passband, so must be damped if used for more than two octaves to smooth it out, negating much of its gain, so a high Qts driver is required if you want a ~flat response over a wide BW since its response will ~mirror the driver's IB response down to Fs if tuned this low.
The TQWT (reverse tapered horn) can load the driver more, so can be shorter for a given tuning (Fp) and here the low Qts driver's stronger motor is preferred with the TQWT's aspect ratio increasing with decreasing Qts. Another advantage of these is that you can fine tune them by adding straight vent sections to the terminus to keep net Vb from getting to far out of hand with a really low Qts such as 0.2.
GM