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Why we bent, yet did not break, the laws of physics

Updated: Oct 30, 2022

What we usually consider as impossible are simply engineering problems... there's no law of physics preventing them. - Michio Kaku

Conventional wisdom states that in order for a speaker to efficiently produce music, especially bass, the speaker driver must be in some sort of baffle. The sound coming from its rear wave should not cancel out the sound from the front wave.

This generally takes the form of a speaker cabinet, often a rectangular box made of wood, sometimes chided as a "monkey coffin".

Cabinet types are have an important acoustic role determining the resulting sound quality and bass response. There are several cabinet types available and one that eliminates the cabinet entirely!

1. Sealed cabinet or acoustic suspension.
PROS: easiest and least expensive to build, slow roll off of bass below tuning frequency of cabinet.

CONS: Usually larger cabinets are needed to produce deeper bass.

2. Vented, bass reflex or ported cabinet.

PROS: deeper bass that sealed cabinets, relatively easy to build, nice compromise between considering size of cabinet and cost/complexity.

CONS: faster roll off below tuning frequency, requires careful measurement of port length.

Used in our Hiro 6.5

3. Horn loaded speaker cabinet.

Comes basically in two types: front loaded and back loaded.

A Front loaded horn was and still is the design used by Klipsch speakers and many others. It places a horn shaped bell in front of the driver to amplify sound. It can be used on any sized driver.
PROS: electronic free amplification, low powered amplifiers may apply here. Dynamics are presented in a more natural way.

CONS: the horn shape, and size must be near perfect to minimize distortion and coloring of the sound such as a shouty sound in vocals. A large or very large cabinet required. Costly to build.

A Back loaded horn is used to catch the rear wave of the driver and funnel it to the rear or front of the speaker. It is tuned to provide the normally 180 degrees out of phase rear wave, reversing its phase due to its 1/4 wavelength and reinforcing the front wave. This produces a 3 decibel boost in bass frequencies.

Used in our Super Hiro and Hiro speakers

PROS: Free bass. The rear wave that is usually wasted is captured by the rear horn and directed into your room. This provides a nice 3 decibel bass boost and increases bass dynamics.

CONS: Very costly to build due to the complexity of the cabinet. Can be large if not folded into a compact design. Critical design constraints require careful tuning of horn length, taper ratio, and horn mouth.

5. A Transmission line cabinet
Is kind of a hybrid between a ported design and a horn design. It provides rear wavs reinforcement, damping and moderately large cabinet size. PROS: Some say it’s the perfect compromise and provides deep tuneful bass. CONS: relatively complex to build with larger sized cabinet. Must be constructed carefully to insure performance gains. Disagreement as to its implementation regarding stuffing type, density, and implementation.

I'm sure I missed some exotic cabinet types and may have omitted some exotic details of each so please feel free to weigh in.
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