Thanks

Bass-reflex speakers use Helmholtz resonance. However, it is important to realize that both standing waves and Helmholtz resonance are possible at the same time. Standing waves develop inside any chamber, depending on its dimensions and whether it is open on one or both ends or somewhere in between. Helmholtz resonance also sets up in any chamber that has an opening. So the two features aren't mutually exclusive.

Thanks for the reply, and the info about Transmition lines.

One thing more. You did not answer my question as to the 2Pi Towers. Are they or are they not TL's.

Thanks

Thanks Wayne.

Take care!

Two π towers are bass-reflex cabinets with Helmholtz resonance tuned to 40Hz. But they are not immune to standing waves along their long axis. Quarter-wave resonance is controlled by stuffing and by the placement of the port and speaker. I would imagine that other similar looking speakers designed to be used as quarter-wave pipes control Helmholtz resonance by using port dimensions that shift the Helmholtz frequency out of the passband or using it to advantage as a secondary acoustic device. But the primary acoustic feature of a two π tower speaker is the Helmholtz resonator of its bass-reflex cabinet.