Acoustics – Diaphragm and enclosure – Reflector baffle
Reexamination Certificate
2001-06-18
2003-06-17
Lockett, Kim (Department: 2837)
Acoustics
Diaphragm and enclosure
Reflector baffle
C181S154000
Reexamination Certificate
active
06578660
ABSTRACT:
FIELD OF THE INVENTION
This invention is in the field of speaker systems and in particular to speaker enclosures intended for operation at the lower or bass frequencies of the audio range.
BACKGROUND
Speaker enclosures have been used as long as sound was reproduced by a conventional electro-mechanical speaker. Enclosures were used as a structural support to hold the speaker in place and to baffle or reduce the effect of noises or out of phase sound waves, created by the operation of the speaker and which interfered with the reproduction of the a true sound intended to be reproduced. In connection with speakers used to produce bass
13
tones at the low frequency end of the audible range, for example from 150 Hz and below the speaker enclosure had to be made large enough so pressures produced with the creation of the sound frequency waves, did not interfere with the extended movement of the speaker cone at those lower frequencies.
As background, speaker enclosures were built with baffles to extend the path for backwardly projected out of phase audio waves emanating from the rear of the speaker, to prevent these waves from interfering with the forward directed waves from the front of the speaker, because of the production of undesirable elements for example standing waves, air turbulence port noise, whistling, and port chuffing. In the case of speaker enclosures at the lower frequency ranges, the enclosure size had to be large enough to accommodate the pressures created at these lower frequencies which prevented the reduction in the size of the enclosure and prevented the enclosure from being made small so that pressure could not be properly vented without producing the before mentioned undesirable sound effects.
Many attempts have been made to solve the problems created by low frequency enclosures for the purpose of making a smaller size enclosure which do not suffer sound degradation associated with higher internal pressures or backwardly directed waves. For example, U.S. Pat. Nos. 5,517,573 and 4,196,792 show ways of using ports to vent the enclosure so low frequency sounds may be reproduced and whistling diminished and so the size of the speaker enclosure could be made smaller. However, these devices were limited as the use of ports to release the speaker internal pressures while effectively managing the standing wave problem from the backwardly projected waves, prevented a reduction in the size of the enclosure. In connection with the projected sound, a large portion of the sound energy in the backwardly projected sound was lost as the object was to reduce the effect of the speaker on the air mass inside the speaker enclosure and the efficiency of the speaker was reduced as the energy associated with the backwardly projected sound wave were not effectively utilized to enhance the sound produced by the speakers. While U.S. Pat. No. 4,231,445 made an attempt to disperse the backwardly or rearwardly projected sound waves, relative to the forward projected sound waves from the front of the speaker, the rearward sound waves were not utilized to project the sound around the speaker enclosure or to extend the sound path relative to the length of the sound waves at the lower frequency range to prevent or minimize degradation of the total sound from the speaker.
SUMMARY OF THE INVENTION
The venturi expander invention disclosed herein in its preferred embodiments and according to the principles of the disclosed invention, overcomes the problems of the prior art devices in removing or relieving the pressures in the speaker enclosure which impede the movement of the speaker cone at low frequencies, for example at 150 Hz. and below, without the accompanying distortion of port noise such as whistling or port chuffing. The venturi expander operates with improved venting; reducing the internal pressure of the enclosure, and permits the volume and size of the enclosure to be reduced. Speaker size reduction using the venturi expander can be accomplished without sacrificing an extended audio path to disperse the backwardly or rearwardly projected out of phase sound waves so their reflections do not create cancellation by the mixing of out of phase rearward sound waves with the forward projected sound waves from the front of the speaker.
The efficiency of the speaker enclosure is enhanced by the venturi expander by providing a path for dispersing the backwardly or rearward projected sound waves, in an extended path through surfaces which direct the movement of the sound waves out of the enclosure in a compound path transverse to and through bell ports placed in the speaker enclosure, extending the path of the sound waves by reflection in the transverse direction while the propagation of the sound waves is through the bell ports. An air port tube in line with the rear of the speaker and opposed to the rear of the speaker is vented at the rear wall of the enclosure, providing a tube like path for relieving the pressure built up in the enclosure around the speaker. The sound waves propagating in a compound path out of the bell ports are in a pattern that causes reflection of the sound waves from the sides, top and bottom of the speaker enclosure and residual sound waves via air port tube exhaust. These sound waves contribute to a 360-degree pattern when combined with the sound waves projecting from the front of the speaker.
The compound sound propagation path is through the speaker enclosure rear wall port opening and the inlet to the bell ports and through the bell ports to the bell port opening, and projecting the rearward sound waves at an angle to the forward sound waves projected from the front of the speaker. The effect is that of a surround sound or 360 degree sound, so for example, in a live performance musicians playing at the sides or rear of an instrument amplified by a venturi expander design speaker enclosure may hear the sound waves from that instrument as do those musicians sitting in the path of the forward projected sound waves.
The bell ports, according to the principles of the venturi expander and as shown in a preferred embodiment of the invention, receive the sound waves emitted from the rear of the speaker and reflected from the interior side walls of the speaker enclosure and exterior of air port tube, and are arranged to reflect the sound back and forth against the rear exterior wall of the speaker enclosure and the sides of the bell ports. In a preferred embodiment, the sides of the bell port are stepped with the distance between the sides of the bell port and the rear wall of the speaker increasing in the direction of propagation from the bell port inlet to the bell port opening. In this way the reflected waves will move obliquely with a direction component transverse to the direct propagation path through the bell port, extending the propagation path and reducing the effect out of phase sound waves would have on the forward propagated waves from the front of the speaker. At the same time, the energy in the rearward-propagated sound waves is not lost or reduced to produce the effect of 360-degree sound wave dispersion.
In accordance with the principles of the invention and the preferred embodiments disclosed, the air port tube extending through the rear wall of the enclosure and through the venturi expander, is in line with, and opposed to the rear of the speaker and vents the higher than ambient air pressure out from the enclosure. The tube may be of a varying size and is placed opposed to the rear of the speaker to effectively vent the internal pressure created by the operation of the speaker. The small size of the air port tube inlet port relative to the cross sectional area of the speaker at the inlet port, allows the flow of air and the release of pressure without interfering with the backwardly projected sound waves reflected internally from the walls of the speaker and the exterior radial wall of the air port tube and out the bell ports. The air tube cross sectional area may be reduced where the size of the speaker is made smaller and may be blocked where the size
Lockett Kim
Rosenblatt Joel I.
LandOfFree
Speaker enclosure venturi expander does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Speaker enclosure venturi expander, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Speaker enclosure venturi expander will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3157583