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You don’t have to take our word that bandpass boxes are outstanding for bass reproduction. Read D. B. Keele’s comments:
"The advantages of the band-pass style of vented-box enclosure include the following:
First, because the sound is radiated only from the port, and not directly from the cone, all forms of distortion are potentially lower. This is due to the high linearity of the acoustic resonance system as compared to the mechanical resonance system of the cone driver.
Second, the acoustic resonant system acts as an acoustic low-pass filter which attenuates any extraneous noises, such as distortion generated by the low-frequency driver.
Third, the low-frequency response of the system rolls off at only 12 dB per octave, the same as a closed-box system, rather than the faster roll-off of a standard vented box, which is 24 dB per octave. This greatly increases the low-frequency energy below the system's 3-dB down point and also improves the system's low-frequency transient response.
Fourth, the sealed box loading one side of the cone adds additional stiffness to the driver and thus increases the system's subsonic power-handling capability. This overcomes one of the major disadvantages of the standard vented-box enclosure, which essentially unloads the driver at frequencies below the vented-box resonance frequency." --D. B. Keele Jr.
This quote was taken from a review of a highly rated stereo speaker in the February 1988, AUDIO magazine. (Pages 88-102.) It was a KEF model 107, which was named a Class A speaker in Stereophile for years. It used two tens in push--pull, in a bandpass enclosure, not unlike the TOBY Ranger. An engineer for the British speaker maker, KEF, named Laurie Fincham, revived the bandpass speaker, originally patented in 1934 with an AES Journal paper in 1978. KEF brought out several models with this concept in the eighties and is still making them.
Keele was an engineer for Electro-Voice, then JBL, and Klipsch. Few speaker engineers in the country have better credentials, and even fewer have the ability to listen to speakers and write reviews on how they sound.
The contribution of TOBY Corp to bandpass subs, was simply to be aware of the information above--to read the technical papers, to buy and analyze the KEF speakers and to write computer programs to model them. Then we created our own designs. Following is an introduction to TOBY subs..
Toby BandPass speakers make excellent subwoofers because they can produce deep, clean, powerful bass in practical-sized enclosures. Unlike conventional direct radiating woofers mounted on the outside of an enclosure, the Toby bandpass boxes have two enclosures. The driver is mounted between them. Frequencies above 100 Hz are filtered out in the coupling cavity and all of the sound is delivered through a port . Each Toby BandPass speaker comes with an individual computer-generated graph of its frequency response. Large diameter cones are not needed in these subs because the air load is in the coupling cavity, not in open air.
For example, the Ranger has more captive air load than four direct-radiating fifteen’s! All of the TOBY BandPass drivers have 2 or 2 1/2 inch diameter voice coils, the same size used in most fifteen-inch drivers, so they have the same power handling. We use premium carbon graphite loaded polypropylene cones to withstand the tremendous air load presented by the BandPass design. All BandPass subs come with a single 4 Ohm woofer or a dual coil 4 Ohm/4 Ohm woofer except the Ranger, which has two 4 Ohm drivers. (For very high power always choose the Ranger!) All of 4 Ohm/4 Ohm subs can be converted into one channel 8 Ohm by jumping the adjacent black and red terminals or converted to 2 Ohm by paralleling the channels. All TOBY subs can be ordered in one channel--4 Ohm except the Ranger.
When you hear a well designed bandpass subwoofer, you’ll recognize the advantages of the band-pass style of vented-box enclosure for bass in the home or car. It might well be a TOBY.