Acoustics – Sound-modifying means – Housing or enclosure
Reexamination Certificate
2000-10-24
2003-02-18
Nappi, Robert E. (Department: 2837)
Acoustics
Sound-modifying means
Housing or enclosure
C181S155000, C381S334000, C381S325000
Reexamination Certificate
active
06520282
ABSTRACT:
FIELD OF THE INVENTION
This invention in general relates to sound enhancement systems and, in particular, to an inexpensive sound enhancement mechanism for use with commercially available guitar and other instrument amplification speaker systems.
BACKGROUND OF THE INVENTION
There are two fundamental amplifier-speaker formats:
1) the combo amp, where an amplifier and a speaker are combined in one cabinet; and
2) the stack, where the amplifier and speaker each have their own cabinet.
In the combo arrangement, the cabinet is usually open-backed. This is called a dipole speaker, because as much sound emanates from the rear of the speaker as from the front. Depending on the environment, some cancellation will occur between the front wave and the back wave. With lean tones, the number of component frequencies present at any given instant is low, so the number of cancellation is also low. With a distorted signal, many more frequency components are present at any one time, so both the number and intensity of cancellations is greater, which “muddies” the sound.
The sealed cabinet does not produce an external rear-wave. Sound emanates only from the front of the cabinet, directly from the speaker, so the only cancellations that can occur are caused by the room itself. These are in no way assisted by the speaker as in the dipole situation. The result is a tighter distortion tone. The sealed cabinet allows maximum power to be fed into the speaker, as the air inside the cabinet provides some acoustic dampening and support for the cone. It is important to note that combo amps with vacuum tube-type circuitry typically need the open back for ventilation.
Vented cabinets (sometimes called bass-reflex), will perform similarly to the sealed box, if the port is on the front baffle. All of the acoustical output is being blown forward, so cancellations are not too likely. Another advantage to the use of closed-back or vented cabinets, regardless of whether they are sealed or vented, is that they will perform more consistently from one environment to another.
The depth of sound of electrical guitar amplification systems is a very important characteristic. Various manufacturers of these systems commonly prize their guitar amplification systems (“amplifiers”) as having “big, spacious, open sound” with a big “bottom end.” While sound systems which can produce a spacious sound are readily available and easily built, they invariably have a number of drawbacks inherent with speaker systems capable of delivering a “spacious” or “big” sound. For instance, guitar amplifier-speaker systems that are most prized for the spaciousness and depth or richness of the sound are usually combinations of a guitar amplifier and separate, larger loudspeaker enclosures (cabinets). This is because the typical cone-type speaker systems using a vibrating diaphragm cone are generally enclosed in a cabinet to contain the sound pressure radiated behind the diaphragm so that it does not negatively interfere with the sound generated in front of the diaphragm and out from the cabinet. This results in a sound enhancement which is typically described as “fuller”, “tighter”, and better “focused”. Generally, the cabinet is designed for maximum internal volume and it is based on characteristics of the loudspeaker diaphragm to obtain the desired “fullness” or “enhanced lower-end response” of sound at lower frequencies.
Examples of these bigger systems are made by many renowned manufacturers, such as Marshall®, Peavy®, Laney®, etc. However, these systems capable of producing a “bigger sound” are usually heavy, bulky, and expensive. Thus, while these systems are generally superior for concert performances, they are highly impractical as quick, carry on, practice or recording amplifiers. Of note, the vast majority of users of these amplifier systems are guitar or other instrument players who do not perform in public. Thus storage, bulkiness and cost of these big amplification-speaker systems is burdening or impractical. In addition, in order to achieve a good sound in an electrical-guitar speaker system, one usually needs to turn the volume up, which results in a sound of very high and inconvenient levels, potentially causing hearing damage, as well as family and neighbor concerns. In contrast, smaller systems have less power and do not reach inconvenient volume levels. However, these smaller systems often lack the fullness, resonance and depth of the larger speaker systems.
The market is flooded with substantially smaller, lighter and inexpensive guitar amplification systems with both the amplifier and the speaker(s) fitted in an easily portable enclosure. As with large speaker cabinets, the speakers are mounted in an opening formed in a front wall of their cabinet. The amplifier unit containing circuitry for driving the speaker, typically is mounted below or above the speaker with the controls therefor accessible through the cabinet wall. These guitar amplifier-speaker systems are known as “combos.” Compared to the larger amplifier-speaker systems, these are light, substantially smaller systems. Unfortunately, these small combos almost universally suffer from the lack of “spaciousness,” or “bottom end,” due largely to the use of smaller size speakers and loudspeaker enclosures. It is known that improved fullness of sound can be obtained in these combo units by either a duct in the cabinet or use of insulation or other absorptive materials on the inner surface of the cabinet walls, or some combination of these features. However, larger cabinets are undesirable as they can become too cumbersome or bulky to be easily lifted and carried or transported in a vehicle. Thus, smaller amplifier-speaker systems have an inherent compromise in their sound quality or depth due to their lightweight, portable and overall small-dimension design. Therefore, there remains a need for an apparatus or method for improving the fullness, resonance and depth of the above-mentioned smaller, portable speaker systems.
In general, the ability of the combo or any amplifier-speaker system to produce lower frequencies (e.g. 70 Hz to 200 Hz) adds a certain dimension to the sound, which is highly prized in guitar or other instrument amplification systems. While the modern amplifier designs are almost universally capable of delivering the whole frequency spectrum required for guitar amplification, unfortunately it is usually the size of the speakers and their cabinets in which they are mounted that largely determine the “bottom end” or the “spaciousness” of the sound. This is especially a problem when playing at low sound pressures (volumes).
Thus, in summary:
Small amplifier-speaker systems (combos):
Easy portability/transport
Inexpensive
Light weight
Highly practical for carry-on, jamming, gigging, etc.
“Thin” sounding, lack of “bottom end” or “depths”
Large amplifier-speaker systems (combos and separate amplifier-speaker cabinet systems)
Bulky
Heavy
Expensive
Less practical for carry-on, jamming, gigging, etc.
“richer,” fuller, more spacious (“bigger”) tone
It is estimated that the vast majority of amplifier-speaker systems sold today are of the smaller size. These are used primarily in private homes for practicing, light jamming, and entertainment. While these amplifier-speaker systems are conveniently sized for transport, placement and storage, their small size also presents a clear disadvantage in quality of the sound reproduction. This disadvantage is in the form of a limitation of the range, depth, fullness and balance of tone that can be achieved with their small cabinet speaker size. Thus, there is a compromise between the speaker design, economics, ergonomics and quality of sound.
Virtually all combo amplifiers made today are either of open back or closed types. Some are equipped with a removable back panel which enables one to convert an open-back model to a closed-back model. However, even then, these combo amplifiers are confined to the volume of the cabinet. This is an obvious disadvantage for the small amplifier design as it is well known that larger cabinet
Hadzic Admir
Hadzic Junuz
Fitch Even Tabin & Flannery
Martin Edgardo San
Nappi Robert E.
Nysora, Inc.
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