Introduction to Cabinets

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Horns:

Horns are used for several different purposes. They typically act like a transformer, changing high pressure, low volume air at the throat (beginning) of the horn to low pressure, high volume air at the mouth (end). This does a couple of things: It increases the efficiency of the driver (more sound pressure per watt of power input), it keeps the driver from moving very far (reducing distortion), and controls directivity (the sound goes only in the direction of the horn). Properly designed they add efficiency, phenomenal dynamics, and greater detail. Badly designs add colorations and/or have very ragged frequency response.
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Front Loaded Horns:

These sit on the front of the driver, and horn load the highs and mid-range information only. The best known examples for Lowthers are the Oris Horn and the Azurahorn. Both of these are well designed, refined systems.
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Back Loaded Horns:
The driver sits on the front of a small box called the compression chamber. The compression chamber has an opening (called the throat) which opens up into the horn. The size of the compression chamber and throat combine to create a low pass filter (so only the bass goes through the horn).

This is the traditional cabinet design for Lowthers. The Acousta, Medallion, Alerion and many other cabinets are designed as rear loaded horns. Because Lowthers are limited in the X-max (how far they can move without distortion or dynamic compression) a rear horn highly desirable to extend bass response. On the negative side, they are difficult to build, and can be very large for deep bass response.
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Front and Rear Loaded Horns:

This occurs when the driver is sandwiched between two horns. The front horn is for the mid’s and high’s, and the rear for the bass. The TP1 and OPUS designs are examples.
Open Baffles:

Basically a slab of wood (or other stiff material) with the driver mounted to it. This has several advantages. Without a box, there are no box resonances or colorations. With the driver radiation energy to the front and rear, the reflected sound off the rear wall opens up the sound, giving a very large, open soundstage. Because the sound travels the front and rear of the baffle, at the edge they cancel. This means there is no edge diffraction effect. The sum total is a design that offers minimal colorations with a big, open sound.
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On the negative side these require placement from the rear wall of at least 3’, with 4’ being preferred. If placed too close, the sound will be smeared due to the back wall reflections coming too soon, affecting the front wave.

Bass response is severely limited, to about 150 hz on a 2’ x 5’ baffle, or 200 hz on a 18” x 42” baffle. A good, fast woofer is required.

For more information, go to this page:
Open Baffles

Taper Quarter Wave:

This is a form of a resonant pipe. Sometimes called a Voigt Pipe after the inventor (yup, the same Paul Voight who started Lowther). An easy to build box that considerably extends bass response. There is a lot of information on these on the web. Requires careful tuning to get the proper compromise between excessively lumpy response when under-stuffed and poor dynamics when over-stuffed.

Closed Boxes:

Using a simple 1.5 cubic foot closed box will allow a typical 8” Lowther to have response to about 150 hz. A nice woofer to fill in the mid-bass and low bass is required. But you will have a beautiful mid-range/high driver. It is recommended that a high pass filter be used to remove bass in this configuration. Note that the Q of the driver will affect the low frequency response, with higher Q drivers like the PM6A or DX2 having better response than lower Q drivers. Simple, easy to build, but not full range. If improperly designed and built these have problems with standing waves, edge diffraction, and poor dynamics.

Bass Reflex Cabinet:

This is a closed box with a resonant pipe that helps extend bass response. Because of the low Q of most Lowthers, use in a bass reflex will result in either no real low end response, or a dip in the mid-bass. When used in a bass reflex, corner placement is often used to reinforce bass response. The higher Q drivers should be used. There are many trade-offs in design and execution, meaning that some form of compromise is required for this design.