Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Plural or compound reproducers
Patent
1997-02-26
1998-12-15
Le, Huyen
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Plural or compound reproducers
381182, 381335, H04R 2500
Patent
active
058504605
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a bass speaker designed for dynamic, high fidelity reproduction of low frequency sounds.
DESCRIPTION OF THE PRIOR ART
Widespread distribution of home entertainment systems for reproducing in the home and other small environments high quality audio sources and audio-visual sources has increased demand for compact speakers capable of reproducing the bass range sounds contained in those sources with power, dynamic presence, and high fidelity.
Dynamic reproduction of such bass sounds requires a large-diameter diaphragm and a sound pressure frequency characteristic that is flat to the lowest frequencies. With conventional sealed speaker enclosures and bass reflex enclosures, however, the Q of low band resonance frequencies increases as the size of the speaker opening increases relative to a constant internal speaker volume, thus producing a peak in the sound pressure-frequency characteristic. It has therefore been accepted that the bass speaker (woofer) opening cannot be very large relative to the enclosure size. High fidelity (quality) bass reproduction also means that sounds from enclosure vibration or resonance must be prevented, but it is difficult to suppress these sounds by simply increasing the thickness and weight of the speaker enclosure panels.
A bass speaker designed to obtain a flat sound pressure-frequency characteristic to low bass range sounds using a large-diameter vibrator with a small internal enclosure volume is described in "Extreme Low Frequency Sound Reproduction by a Passive Radiator and an Acoustic Transformer" (Yoshii Hiroyuki, Report of the Meeting of the Acoustical Society of Japan, October 1978, p. 281-282). The speaker described in this article is known today as a "bandpass" or "kelton" speakers. The structure of this conventional bass speaker is described below with reference to the simplified cross section thereof shown in FIG. 15.
Referring to FIG. 15, the inside of the bandpass-type speaker enclosure 103 is separated by an internal speaker divider 104 into a back cavity 105 and a front cavity 106. The driver unit 101 is mounted on the internal speaker divider 104 and a passive radiator 102 is mounted on the front enclosure panel 103a such that bass sounds are projected from the passive radiator 102. Note that the driver unit 101 and passive radiator 102 create an acoustic transducer in the front cavity 106.
The operation of this bass speaker is described next with reference to the electroacoustic equivalent circuit shown in FIG. 16 and FIG. 17 and the frequency characteristic graph shown in FIG. 18.
Referring to FIG. 16, drive force Fd is the drive force applied to the vibration system by the voice coil of the driver unit's magnetic circuit, the effective vibration mass Md is the effective vibration mass of the driver unit's vibration system, compliance Cd is the compliance of the driver unit support system (edges and dampers), and resistance Rd is the sum of the mechanical resistance of the driver unit vibration system and the electromagnetic braking resistance resulting from the counter-electromotive force of the magnetic circuit. Also indicated in FIG. 16 and FIG. 17 are the air compliance CB of the back cavity 105, the mechanical resistance RB of the air in the back cavity 105, the air compliance CF of the front cavity 106, the mechanical resistance RF of the air in the front cavity 106, the effective vibration mass Mp of the passive radiator vibration system, the mechanical resistance Rp of the passive radiator vibration system, the compliance Cp of the passive radiator support system (edges and dampers), the driver unit vibration system speed Vd, and the passive radiator vibration system speed Vp.
Other values referenced in FIG. 16 and FIG. 17 include the effective vibration area Sd of the driver unit and the effective vibration area Sp of the passive radiator, resulting in an acoustic transducer with a winding ratio of Sd:Sp. If the parameters of the passive radiator are converted from the driver unit side, an el
REFERENCES:
patent: 4146744 (1979-03-01), Veranth
patent: 4783820 (1988-11-01), Lyngdorf et al.
Hiroyuki Yoshii, entitled "Extreme Low frequency Reproduction by a Passice Radiator and an Acoustic Transformer" appears at pp. 281 and 282 of the Oct. 1978 Report of the Meeting of the Acoustical Society of Japan.
An English Language Abstract of JP No. 4-4700.
An English Language Abstract of JP No. 1-140896.
An English Language Abstract of JP No. 57-3500.
An English Language Abstract of JP No. 3-108999.
An English Language Abstract of JP No. 4-117098.
English Language Translation of JP-47-31638.
Kageyama Satoshi
Tamura Kazuaki
Tanaka Shoji
Le Huyen
Matsushita Electric - Industrial Co., Ltd.
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