This invention relates to a dynamic speaker design utilizing a diaphragm, voice coil assembly, and magnet system producing acoustic output as a dipole radiator. The invention also relates to a method of utilizing the dipole radiating dynamic speaker design for tweeter and mid-range speaker applications used in home, automotive, and professional audio systems.
Dynamic speakers utilizing a diaphragm, voice coil assembly, and magnet system providing acoustic output as monopole radiators have been manufactured for many years and are still widely used in commercial, professional, and home applications. The dynamic speaker has endured as the most popular speaker design due to its low cost, compact design, ease of use, and reliability. However, the dynamic monopole speaker audio reproduction quality is considered inferior to other more expensive speaker design technologies such as electrostatic, planar magnetic, and ribbon type.
A dynamic speaker system generally utilizes multiple dynamic speakers that provide acoustic output for specific frequency ranges. Dynamic speakers that provide mid-frequency and high-frequency acoustic output are generally known as mid-range and tweeter units, respectively. This patent addresses the design deficiencies with prior art mid-range and tweeter dynamic speakers.
A brief explanation of acoustic wave propagation is necessary to effectively describe the prior art dynamic speaker design deficiencies. A speaker generates acoustic wave output by converting an electrical signal into mechanical diaphragm motion. In operation, the diaphragm vibrates proportional to the electrical signal passing through the voice coil producing forward and rearward propagating acoustic wave output. The diaphragm movement produces half of the acoustic output energy in the forward direction and half in the rearward direction. This fundamental wave propagation principal is common to all speakers producing acoustic output in response to diaphragm motion.
In general, speakers that provide low frequency output utilize an enclosure to prevent acoustic cancelation caused by the interaction of the forward and rearward wave propagation. Typically, midrange and tweeter dynamic speakers are mounted in a common enclosure with other low frequency producing dynamic speakers. The low frequency dynamic speaker produce acoustic output of sufficient magnitude within the enclosure that damage to the mid-range and tweeter diaphragms would result if acoustic isolation were not provided. As a result, the prior art of mid-range and tweeter dynamic speaker design incorporate a means of blocking the acoustic output from other speakers in order to isolate and protect the diaphragm. These mid-range and tweeter dynamic speakers produce acoustic output in only one direction as monopole radiators.
The main flaw in the prior art dynamic speaker design is the incorporation of the acoustic wave blocking means. The acoustic wave blocking means also acts to block the rearward propagating acoustic output from the tweeter or mid-range speaker. As a result, the trapped rearward propagating acoustic output is reflected within a space internal to the speaker causing acoustic wave distortion known as constructive and destructive interference. This distorted acoustic output is dissipated primarily on the diaphragm due the reflective characteristic of the materials utilized in the dynamic speaker construction. Subsequently, the forward propagating acoustic output is corrupted due to the dissipation of the distorted acoustic output from the rearward propagating acoustic output. In effect, half of the dynamic monopole speaker acoustic output energy is distorted and dissipated on the diaphragm causing significant degradation of the forward propagating acoustic output accuracy. As a result the dynamic monopole speaker design produces inferior imaging resolution and audio reproduction accuracy compared to other speaker design technologies.
The prior art of dynamic speaker design does not effectively address the audio reproduction quality degradation caused by the containment of the rearward propagating acoustic output.
The following drawings illustrate prior art mid-range and tweeter dynamic monopole speaker design. Those skilled in the art of dynamic speaker design, operation, and manufacture will be familiar with the construction and operation. The following drawings illustrate prior art dynamic speaker design deficiencies described above.
FIG. 1 illustrates a typical prior art dynamic monopole speaker design. Dynamic mid-range and tweeter speakers generally contain the following main components: a diaphragm 10, a voice coil assembly 12 containing the voice coil and former, front and rear flux conductor plates 14 and 16, a solid pole flux conductor 18, a permanent magnet 20, and a mounting frame 22. The flux conducting components are composed of a ferro-magnetic material, for example, steel. This dynamic speaker construction utilizes a solid pole flux conductor 18 secured to the rear flux conductor plate 16. This construction provides an economical speaker assembly that has been manufactured for many years. However, this construction suffers from the fundamental design flaw that degrades the audio reproduction quality. The solid pole flux conductor 18 acts to block the rearward propagating acoustic output emanating from the vibrating diaphragm 10. The area contained between the diaphragm 10 and the solid pole flux conductor 18 forms a closed chamber that traps the rearward propagating acoustic output. As a result, the rearward propagating acoustic output forms constructive and destructive waveform interference that is reflected and dissipated on the diaphragm 10. This distorted acoustic output negatively impacts the forward propagating acoustic output resulting in audio reproduction quality degradation.
FIG. 2 illustrates an improved prior art dynamic monopole speaker construction. This dynamic speaker is designed with the same components as described in FIG. 1 with the exception of the following components. The improved design utilizes a vented pole flux conductor 24 containing a cylindrical hole providing a passage to a rear chamber C1 formed by a sealed rear housing 26. The rear chamber C1 contains acoustic damping material 28 which acts to dampen the rearward propagating output by dissipating a portion of the rearward propagating acoustic output over time. However, this construction entraps half of the acoustic output energy within the limited volume of chamber C1 and does not adequately address the adverse effects caused by the fundamental design flaw. The stored acoustic output contained in the rear chamber is reflected and dissipated on the diaphragm 10 which negatively impacts the forward propagating acoustic output resulting in audio reproduction quality degradation.