1. Field of the Invention
The invention relates to speakers. In particular, the invention relates to a transducer unit, i.e. motor, having a diaphragm comprising a metallic section and a non-metallic section.
2. Description of the Related Art
A speaker, i.e. loudspeaker, is a transducer, converting electrical signals to mechanical energy. The mechanical energy displaces air to create sound. Since “speaker” may refer to a transducer units as well as one or more “speakers” in a full or partial enclosure, in this application “speaker motor” or “motor” refers to the transducer unit and “speaker” refers to one or more motors in an enclosure.
A speaker motor typically includes, among others, seven (7) basic components, a frame, a magnet assembly, a voice coil, a spider, a diaphragm, and a surround. The frame provides a means to secure the motor in a protective and/or acoustically advantageous enclosure. A magnet assembly is secured to the frame and forms a gap in which a voice coil is able to move.
A flexible damper, i.e. a spider, is secured into the frame above the magnet assembly and is glued to the voice coil to suspend the voice coil in the gap. The wide base of a conical diaphragm is flexibly suspended at a rim at the top of the frame and is rigidly secured to the voice coil.
A changing electrical signal is fed to the voice coil by an amplifier integral with another device or connected in series separate from another device. The changing electrical signal causes fluctuations in the magnetic field of the magnet assembly and the voice coil moves in the gap in relation to the fluctuations. The movement of the voice coil causes the diaphragm to move and displace air to create sound.
While all parts of the motor have an effect on sound quality, the composition of the diaphragm is particularly important. Typically, diaphragms are made of paper. A paper diaphragm excels at low frequency sounds, but distorts high frequency sounds due to the inherent flexibility of paper. Thus, paper diaphragms may be coated with a plasticizing agent.
In other instances, paper diaphragms are supported. For example, U.S. Pat. No. 2,071,828 to Glen appears to teach a paper diaphragm connected directly to the voice coil, but that is supported by a second cone in an apex region where high frequency sounds originate. This second cone is driven by the air in the air gap of the voice coil and helps the paper diaphragm achieve a high resonance.
This characteristic of paper diaphragms makes a motor sound better at certain frequency ranges while sacrificing performance in other ranges. Consequently, the speaker into which a paper diaphragm is built is limited to certain applications to woofers that produce low sounds and to midrange speakers that are suitable for everyday usage.
To produce high frequency sounds, tweeters, which may have a different structure, use a metal diaphragm. The inherent rigidity of aluminum, magnesium, or other lightweight metal or alloys permits metal diaphragms to excel at high frequency sounds. Using the motor structure described above with a metal diaphragm creates a motor that produces better high frequency sounds, but fails to produce adequate low frequency sounds.
Thus, a first need is for a motor that is suitably for a wide range of uses.
A motor with a metal diaphragm has a further draw back. Since metal diaphragms are heavier, the voice coil has more mass to move and, thus, either a stronger electrical signal must be provided to the voice coil or the magnetic field has to be improved. Similarly, to produce a more powerful motor, a stronger electrical signal must be provided to the voice coil or the magnetic field has to be improved.
A “super” magnet, also called a rare earth magnet, may be used to create a greater magnetic field that is capable of lifting a greater mass. Super magnets are typically made of neodymium iron boron, NdFeB. In comparison to ferrite magnets, these super magnets provide additional magnetic strength in a small volume, but lose their magnetism above 80 degrees Centigrade.
Thus, a second need is for a motor that dissipates heat so that a neodymium magnet may maintain its magnetic field.
To improve motors, voice coils may have the number of turns of wire coil increased. However, increasing the number of turns also increases heat proximal to the magnet assembly. Thus, a third need is for a motor that dissipates heat from a voice coil.
These and other needs are met by the present invention.