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| university:courses:electronics:electronics-lab-speaker [06 Sep 2019 14:31] – replaced Z plot Pop Andreea | university:courses:electronics:electronics-lab-speaker [05 Apr 2023 18:43] (current) – [Background:] Doug Mercer |
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| ====== Activity: Measuring a Loudspeaker Impedance Profile ====== | ====== Activity: Measuring a Loudspeaker Impedance Profile - ADALM2000====== |
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| ===== Objective: ===== | ===== Objective: ===== |
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| Knowing the resonate frequency and the minimum and maximum impedances are important when designing cross over filter networks for multiple driver speakers and the physical enclosure the speakers are mounted in. | Knowing the resonate frequency and the minimum and maximum impedances are important when designing cross over filter networks for multiple driver speakers and the physical enclosure the speakers are mounted in. |
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| | Dynamic loudspeakers are abysmally inefficient electro-mechanical conversion devices, as [[wp>Loudspeaker|Wikipedia]] substantiates: “Loudspeaker efficiency is defined as the sound power output divided by the electrical power input. Most loudspeakers are inefficient transducers; only about 1% of the electrical energy sent by an amplifier to a typical home loudspeaker is converted to acoustic energy.” Yes, 1% is an abysmal efficiency as we try to “be more green”, but so far it is the best we have that sounds good (and each dynamic transducer only sounds good over a limited frequency range). |
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| ==== Loudspeaker Impedance Model ==== | ==== Loudspeaker Impedance Model ==== |
| To help understand the measurements we are about to make, a simplified electrical model of a loudspeaker is shown in figure 1. | To help understand the measurements we are about to make, a simplified electrical model of a loudspeaker is shown in figure 1. |
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| {{ :university:courses:electronics:alz_f1.png?600 |}} | <WRAP centeralign> {{:university:courses:electronics:loudspeaker_model.png?600|}} </WRAP> |
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| <WRAP centeralign> Figure 1. Loudspeaker Impedance Model </WRAP> | <WRAP centeralign> Figure 1. Loudspeaker Impedance Model </WRAP> |
| • F<sub>S</sub> is the resonant frequency of a loudspeaker. The impedance of a loudspeaker is a maximum at F<sub>S</sub>. The resonant frequency is the point at which the total mass of the moving parts of the loudspeaker become balanced with the force of the speaker suspension when in motion. The resonant frequency information is important to prevent an enclosure from ringing. In general, the mass of the moving parts and the stiffness of the speaker suspension are the key elements that affect the resonant frequency. A vented enclosure (bass reflex) is tuned to F<sub>S</sub> so that the two work in unison. As a rule, a speaker with a lower F<sub>S</sub> is better for low-frequency reproduction than a speaker with a higher F<sub>S</sub>. | • F<sub>S</sub> is the resonant frequency of a loudspeaker. The impedance of a loudspeaker is a maximum at F<sub>S</sub>. The resonant frequency is the point at which the total mass of the moving parts of the loudspeaker become balanced with the force of the speaker suspension when in motion. The resonant frequency information is important to prevent an enclosure from ringing. In general, the mass of the moving parts and the stiffness of the speaker suspension are the key elements that affect the resonant frequency. A vented enclosure (bass reflex) is tuned to F<sub>S</sub> so that the two work in unison. As a rule, a speaker with a lower F<sub>S</sub> is better for low-frequency reproduction than a speaker with a higher F<sub>S</sub>. |
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| • R represents the mechanical resistance of a driver's suspension losses. | • R represents the mechanical resistance of a driver's suspension losses. Part of the “mechanical resistance” in the system is the resistance of the cone to moving through the air, which happens to be the mechanical process that produces the pressure variations that we perceive as ‘sound’. |
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| ===== Materials: ===== | ===== Materials: ===== |
| ==== For further reading: ==== | ==== For further reading: ==== |
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| [[http://www.analog.com/static/imported-files/application_notes/236037846AN_843.pdf|Measuring a Loudspeaker Impedance Profile Using the AD5933]] | [[adi>static/imported-files/application_notes/236037846AN_843.pdf|Measuring a Loudspeaker Impedance Profile Using the AD5933]] |
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| http://en.wikipedia.org/wiki/Electrical_characteristics_of_dynamic_loudspeakers | http://en.wikipedia.org/wiki/Electrical_characteristics_of_dynamic_loudspeakers |
| <WRAP round download> | <WRAP round download> |
| **Lab Resources:** | **Lab Resources:** |
| * Fritzing files: | * Fritzing files: [[downgit>education_tools/tree/master/m2k/fritzing/loudspeaker_imp_bb|loudspeaker_imp_bb]] |
| * LTSpice files: | * LTSpice files: [[downgit>education_tools/tree/master/m2k/ltspice/loudspeaker_imp_ltspice|loudspeaker_imp_ltspice]] |
| </WRAP> | </WRAP> |
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