Bass reflex enclosure expert??

[yodnnee]

Hey,

Just wondering if anyone could explain what is the purpose or idea is behind these enclosures?

My primary concern: Bass reflex enclosures work by bringing the sound waves generated by the rear of the speaker driver into phase with those of the front of the driver? However given that sound waves have an infinite wave length, wont this given any one position of the "port" cause only a small range of frequencies to come into phase, whilst having the opposite effect on sound waves that have wave lengths which are not multiples of those which have been successfully brought into phase.


Obviously I'm incorrect because bass reflex enclosures are popular amongst many manufactures. I just don't understand why??

Any assistance would be greatly appreciated,

Cheers!

 

[timoteo]

Someone will explain it much better than me but:
Yes but more so on paper.
No for the most part to our ears due to our perception of sound at low frequencies.
However we do percieve it enough to hear that sealed is tighter because bass is generated from 1 source, not a 2nd i.e port or PR.

Believe it or not im no expert!!!!

 

[GranteedEV]

A bass reflex enclosure, is a loading whereby the internal pressure from the rear wave pushes a mass of air (vent) or passive radiator to create bass that is in tune with the front wave.

Below that tuning, the mass of air actually behaves more like a hole or opening. The driver no longer sees the internal pressure of the box at all (like it's in an infinite baffle) so its excursion rises, and the sound produced by the vent or passive radiator slowly begins to move out of phase with the driver, leading to a 24db/octave rolloff below tuning instead of the 12db/octave rolloff of just a sealed speaker. Below tuning, it is effectively a DIPOLE.

However we do percieve it enough to hear that sealed is tighter because bass is generated from 1 source, not a 2nd i.e port or PR.

Tuned correctly, we actually don't perceive this at all. Floyd Toole's research, among many other controlled tests, show we actually can't recognize a good bass reflex from sealed at all.