The present invention relates to a loudspeaker system and especially to a loudspeaker system using an elongated hollow tube having wide range speakers mounted in each end thereof for emanating sounds from each of the tube.
The loudspeaker tube system in accordance with the present invention will produce a stereophonic sound or a dual monophonic sound system which is self-contained in a single length of pipe or tubing with a full range loudspeaker at either end of the length of the pipe. The design simplifies the otherwise cumbersome loudspeaker components normally associated with higher quality sound systems by having a single module that does all of the work for the system.
In the past, stereophonic sound systems of high quality sound reproductions have been incorporated into two or more loudspeaker enclosures. These enclosures employ more than one driver inside the loudspeaker box and many employ a woofer, midrange, and a tweeter driver in at least two enclosures separated by distance between the two speakers to achieve a sound stage. Sometimes a subwoofer is used to handle bass frequencies below 100 Hz.
The present invention is a full range loudspeaker system which maximizes the bass frequencies in the subwoofer range and isobaric configurations set the two drivers out of phase with each other in the tube to increase the lower frequency sound pressure levels while minimizing box size requirements. This technique is commonly called "push-pull" because one loudspeaker pushes while the other pulls using the air pressure in the enclosure. This technique has been successfully used in low frequency units in the past but has had severe limitations in full range loudspeakers. One problem in full range loudspeakers has been the phase shift in a full range loudspeaker system, particularly where a stereophonic or discrete two channel signals are introduced. The phase must be correct or the sound stage will be off-center. In addition, one speaker will seem to have more bass than the other speaker, which will sometimes appear tinny or thin. An advantage of the present system using a length of tubing is that a discrete stereo signal can be placed in phase to each driver by having one driver face the furthest distance from the other inside a single pipe. The signal from channel one will cause the associated driver to push out thereby rarifying the air within the container and pulling the opposing driver along while doubling the SPL and bass frequency response. The second driver, which receives a second signal, will electrically be pulling in the opposite direction to that of the acoustic action caused by the first signal reaction. Thus, a dual opposing signal or extended stereo signal can create a push-pull affect on a full range loudspeaker system if that system is contained in a single unit where the drivers are set to the furthest point within the unit away from each other, in phase electrically, and where the enclosure is equal to a minimum of twice the length of the radius of one of the drivers and assuming both drivers are of equal character, size, shape, and general electrically acoustical response to one another.
There have also been small stereophonic systems in the past but the advantage of the cylindrical tube is that it is a singular and small pipe with a length of five inches or more, can put out more bass with more sound pressure level, and more full range frequency response with more clarity and with more perceived volume than systems three to four times its size and weight.
In the stereophonic full range mode, the sound stage can be easily adjusted using simple mechanical controls or walls to reflect the sound in the direction you would have it to go. The width of the sound stage can be spread out or brought in closer depending upon how far out you choose to place the simple deflection walls.
Another way to create a sound stage which incorporates an acoustic center field image is to cut a hole into the center of the pipe equal in size to at least half the radius of either of the two drivers and force a length of pipe, at least the length of the diameter of the hole, into the hole, closing off all air from escaping outside the center hole. The interaction between the two stereo signals using standard tuning procedures, like a helmholtz or a small theile tuned port, will produce the third product of sound which results from the tuned port or an acoustical center field.
In a dual mono-mode, where each of the two speakers are driven by a monophonic signal, a better bass signal can be produced and two pipes can be used driven by the same monophonic signal to produce a bigger, louder sound capability. In the dual monophonic configuration each driver can be wired in standard phase, which produces a single point source full range uniform response, or out-of-phase using the isobaric configuration. In this configuration, the bass response will increase below 150 Hz but the length of pipe needs to be cut to be equal to at least the length of one of the drivers radius. For instance, if the driver is 4" around, the length between the two drivers would be approximately 4" long. The disadvantages of this configuration is the sacrifice that some of the full range uniformity but where two separate pipes are employed, the bass extension or in-phase driver can be loaded towards the wall to increase the bass by 3 db per pipe with the full range sound extended into the room acting as the point source. The same system can be also accomplished with a longer pipe but the electroacoustic phasing will not be as effective for delivery of deeper bass as it would in the smaller enclosure using generally standard type drivers.
Prior art speaker systems may be seen in the following U.S. patents. In the Ashe U.S. Pat. No. 2,905,259, a tubular speaker housing has a single loudspeaker mounted in the middle of two truncated cones attached to form one tube spreading in each direction. The Lanternier U.S. Pat. No. 4,905,788, shows an electro-acoustic transducer which uses a single hollow cylindrical support for an active speaker at one end and a passive radiator mounted at the opposite end thereof for increasing the bass response from the tube. Two systems are required for stereo response. In the Flanders U.S. Pat. No. 4,753,317, a trapezoidal loudspeaker enclosure mounts a loudspeaker at one end at an angle and passively at the other with attached base plates over each angled end of the enclosure. The Manger U.S. Pat. No. 4,268,719, is a loudspeaker arrangement giving a pair of back-to-back loudspeakers in an infinite baffle arrangement. The Seville U.S. Pat. No. 4,655,315, teaches a speaker system having a plurality of serially connected angularly disposed hollow tubes with a loudspeaker mounted at one end, which tube can be adjusted to different shapes. The Virva U.S. Pat. No. 4,164,988, shows a fine tuned column speaker system in which a bellows is formed in part of tube or in which telescoping tubes can be adjusted for a single loudspeaker to vary the length of the back tube for the backwave of the speaker. The Robinson U.S. Pat. No. 3,945,461, is a sound speaker system which has an adjustable telescoping tube which can be locked in place and has a loudspeaker mounted facing the bottom of one of the tubes.
The aim of the present invention is to have a loudspeaker system with a single elongated hollow tube which may be a rigid tube or a telescoping tube with a wide range speaker mounted in each end thereof and the tube length set to accomplish the desired affect in both the wide range sound and increased bass response and also to utilize positioned end deflectors for directing the sound.