My initial thought was:
A bass reflex box emphasizes the midrange too, because of resonance. It emphasizes the midrange more so than a TL.
A low pass notch filter (one inductor and one resistor in parallel as a unit, and the unit in series with the driver) will allow for a HIGHER resistor value without losing clarity, since the midrange is getting emphasized in the BR box.
Of course, a higher resistor would lead to MORE bass.

So, for a given driver, the differential effect of a low pass notch filter will be greater for a well designed BR box, than for a well designed TL box.

I understand that the BR may not emphasize all frequencies equally, and a TL may be a bit less colored, but put that aside for a while.

What do you all think?
-akhilesh

In both transmission line and bass-reflex loudspeakers, the designer generally intends for midrange energies entering the cabinet to be attenuated so that they are not present. Low-pass filters formed by acoustic insulation and by woofer crossover components both serve to reduce energies that energize unwanted higher-frequncy resonances. But for what energies are within the cabinet, the major issues are caused by standing waves, which is the property transmission lines are based upon.

You may be interested in the paper called Acoustic Filters, Waveguides and Transmission Lines, by Daniel Russell.

Basically, the "hollowness" of the BR should make it more resonant of the higher frequencies. Of course if adequate absoorptive material is used around the walls , then you are right, it won;t matter. In fact the resonant frequency will be a single one for the BR box, as you say.

So, what do you think, will the contour shaping notch filter circuit affect a BR more or less?

-akhilesh

If we restrict our discussion to a classic TL (no restriction at the open end) and a classic BR (no stuffing). Ignoring any internal standing waves between the sides or the front and back of the boxes. In the BR ignore the standing wave from the top to the bottom, we need to include this direction in the TL or it would not work.

The BR will have a smoother midrange response which is essentially just the woofer's SPL response. The mass of air in the port should kill all higher frequency output, remember that the port's acoustic SPL response rises at 12 dB/octave to a peak at the tuning frequency and then falls at 12 dB/octave above the tuning frequency. The SPL output from the port above the tuning frequency should monotonically fall as frequency increases.

The classic TL's output from the terminus will produce gentle peaks and dips at the odd higher harmonics of the tuning frequency (assuming it is a straight line). This will create a ripple around the SPL that the woofer would naturally put out over the midrange.

In the midrange, where baffle step occurs, the two systems should exhibit essentially the same average efficiency complete with the 3 to 4 dB rise due to the baffle step. The correction circuit should have the same effect on both types of designs. The only difference might be the frequency range which BSC cuts in due to size differences in the enclosures.

Martin

True, but in a straight TL the harmonics are in an odd multiple order.In a TQWT the harmonics are in an even order(closer together) which gives a greater LF response bandwidth.
Even though the TQWT will not go quite as low as a TL in frequency (given the same sound path length)i like the TQWT a bit better as the LF has a better response over a greater frequency range.
ron