掰掰耳機「核心參數」Thiele/Small參數

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Thiele/Small是1970年代 A.N.Thiele和R.H.Small首次提出了直接輻射式揚聲器的幾個獨立的小信號參數，這些小信號參數用於表徵揚聲器的低頻性能，廣泛用於揚聲器系統（音箱）生產和設計過程。國際電工委員會（IEC）將其稱為Thiele-Small參數。

Thiele/Small參數 (通常縮寫為T/S、TSP以及簡稱為TS參數) 是一組定義揚聲器單體低頻表現的機電參數。這些參數記載在揚聲器單體製造商提供的規格文件中，以便設計者挑選現成的單體進行揚聲器設計。使用這些參數，揚聲器設計者可以模擬振膜的位置、速度、加速度、輸入阻抗和揚聲器系統的聲音輸出。

B

Magnetic flux density in gap, in Tesla-meters (TM)

BL

The magnetic strength of the motor structure. "Expressed in Tesla meters, this is a measurement of the motor strength of a speaker. Think of this as how good a weightlifter the transducer is. A measured mass is applied to the cone forcing it back while the current required for the motor to force the mass back is measured. The formula is mass in grams divided by the current in amperes. A high BL figure indicates a very strong transducer that moves the cone with authority!"

C

Propagation velocity of sound at STP, approx. 342 m/s

Cas

Acoustical equivalent of Cms

Cmes

The electrical capacitive equivalent of Mms, in farads

Cms

The drivers mechanical compliance (reciprocal of stiffness), in m/N

D

Effective diameter of driver, in meters

F3

-3 dB cutoff frequency, in Hz

Fb

Enclosure resonance (usually for bass reflex systems), in Hz

Fc

System resonance (usually for sealed box systems), in Hz

Fs

Driver free air resonance, in Hz. This is the point at which driver impedance is maximum. "This parameter is the free-air resonant frequency of a speaker. Simply stated, it is the point at which the weight of the moving parts of the speaker becomes balanced with the force of the speaker suspension when in motion. If youve ever seen a piece of string start humming uncontrollably in the wind, you have seen the effect of reaching a resonant frequency. It is important to know this information so that you can prevent your enclosure from ringing. With a loudspeaker, the mass of the moving parts, and the stiffness of the suspension (surround and spider) are the key elements that affect the resonant frequency. As a general rule of thumb, a lower Fs indicates a woofer that would be better for low-frequency reproduction than a woofer with a higher Fs. This is not always the case though, because other parameters affect the ultimate performance as well."

L

Length of wire immersed in magnetic field, in meters

Lces

The electrical inductive equivalent of Cms, in henries

Le

"This is the voice coil inductance measured in millihenries (mH). The industry standard is to measure inductance at 1,000 Hz. As frequencies get higher there will be a rise in impedance above Re. This is because the voice coil is acting as an inductor. Consequently, the impedance of a speaker is not a fixed resistance, but can be represented as a curve that changes as the input frequency changes. Maximum impedance (Zmax) occurs at Fs. "

Ms

The total moving mass of the loudspeaker cone.

Mmd

Diaphram mass, in grams

Mms

The drivers effective mechanical mass (including air load), in kg. "This parameter is the combination of the weight of the cone assembly plus the 『driver radiation mass load』. The weight of the cone assembly is easy: it』s just the sum of the weight of the cone assembly components. The driver radiation mass load is the confusing part. In simple terminology, it is the weight of the air (the amount calculated in Vd) that the cone will have to push."

n0

The reference efficiency of the system (eta sub 0) dimensionless, usually expressed as %

p uppercase Ρ, lowercase ρ or ?;

(rho) Density of air at STP 1.18 kg/m^3

Pa

Acoustical power

Pe

Electrical power

Q

The relative damping of a loudspeaker

Q Parameters

"Qms, Qes, and Qts are measurements related to the control of a transducers suspension when it reaches the resonant frequency (Fs). The suspension must prevent any lateral motion that might allow the voice coil and pole to touch (this would destroy the loudspeaker). The suspension must also act like a shock absorber. Qms is a measurement of the control coming from the speakers mechanical suspension system (the surround and spider). View these components like springs. Qes is a measurement of the control coming from the speakers electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock. Qts is called the Total Q of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same.

As a general guideline, Qts of 0.4 or below indicates a transducer well suited to a vented enclosure. Qts between 0.4 and 0.7 indicates suitability for a sealed enclosure. Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications. However, there are exceptions! The Eminence Kilomax 18 has a Qts of 0.56. This suggests a sealed enclosure, but in reality it works extremely well in a ported enclosure. Please consider all the parameters when selecting loudspeakers. If you are in any doubt, contact your Eminence representative for technical assistance."

Qa

The systems Q at Fb, due to absorption losses; dimensionless

Qec

The systems Q at resonance (Fc), due to electrical losses; dimensionless

Qes

The drivers Q at resonance (Fs), due to electrical losses; dimensionless. "A measurement of the control coming from the speakers electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock."

Ql

The systems Q at Fb, due to leakage losses; dimensionless

Qmc

The systems Q at resonance (Fc), due to mechanical losses; dimensionless

Qms

The drivers Q at resonance (Fs), due to mechanical losses; dimensionless. "A measurement of the control coming from the speakers mechanical suspension system (the surround and spider). View these components like springs."

Qp

The systems Q at Fb, due to port losses (turbulence, viscousity, etc.); dimensionless

Qtc

The systems Q at resonance (Fc), due to all losses; dimensionless

Qts

The drivers Q at resonance (Fs), due to all losses; dimensionless. "The Total Q of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same."

R

Ripple, in dB

Re

"This is the DC resistance of the driver measured with an ohm meter and it is often referred to as the DCR. This measurement will almost always be less than the drivers nominal impedance. Consumers sometimes get concerned the Re is less than the published impedance and fear that amplifiers will be overloaded. Due to the fact that the inductance of a speaker rises with a rise in frequency, it is unlikely that the amplifier will often see the DC resistance as its load."

Ras

Acoustical equivalent of Rms

Res

The electrical resistive equivalent of Rms, in ohms

Rms

"This parameter represents the mechanical resistance of a driver』s suspension losses. It is a measurement of the absorption qualities of the speaker suspension and is stated in N*sec/m."

Revc

DC voice coil resistance, in ohms

Rg

Amplifier source resistance (includes leads, crossover, etc.), in ohms

Rms

The drivers mechanical losses, in kg/s

Sd

Effective piston radiating area of driver, in square centimeters. "This is the actual surface area of the cone, normally given in square cm."

SPLo

Sound Pressure Level, usually measured at 1 watt, at 1 meter in front of the loudspeaker

Vas/Cms

"Equivalent volume of compliance", this is a volume of air whose compliance is the same as a drivers acoustical compliance Cms (q.v.), in cubic meters. "Vas represents the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker. Vas is one of the trickiest parameters to measure because air pressure changes relative to humidity and temperature — a precisely controlled lab environment is essential. Cms is measured in meters per Newton. Cms is the force exerted by the mechanical suspension of the speaker. It is simply a measurement of its stiffness. Considering stiffness (Cms), in conjunction with the Q parameters gives rise to the kind of subjective decisions made by car manufacturers when tuning cars between comfort to carry the president and precision to go racing. Think of the peaks and valleys of audio signals like a road surface then consider that the ideal speaker suspension is like car suspension that can traverse the rockiest terrain with race-car precision and sensitivity at the speed of a fighter plane. It』s quite a challenge because focusing on any one discipline tends to have a detrimental effect on the others. "

Vd

Maximum linear volume of displacement of the driver (product of Sd times Xmax), in cubic meters. "This parameter is the Peak Diaphragm Displacement Volume — in other words the volume of air the cone will move. It is calculated by multipying Xmax (Voice Coil Overhang of the driver) by Sd (Surface area of the cone). Vd is noted in cc. The highest Vd figure is desirable for a sub-bass transducer."

Xmax/Xmech

Maximum peak linear excursion of driver, in meters. "Short for Maximum Linear Excursion. Speaker output becomes non-linear when the voice coil begins to leave the magnetic gap. Although suspensions can create non-linearity in output, the point at which the number of turns in the gap (see BL) begins to decrease is when distortion starts to increase. Eminence has historically been very conservative with this measurement and indicated only the voice coil overhang (Xmax: Voice coil height minus top plate thickness, divided by 2). Xmech is expressed by Eminence as the lowest of four potential failure condition measurements times 2: Spider crashing on top plate; Voice coil bottoming on back plate; Voice coil coming out of gap above core; Physical limitation of cone. Take the lowest of these measurements then multiply it by two. This gives a distance that describes the maximum mechanical movement of the cone."

Zmax

"This parameter represents the speaker』s impedance at resonance."

這些參數，許多僅在共振頻率下被確切定義，但此模擬方法一般可應用在振膜作動主要是活塞運動時的頻率範圍。意即振膜整體一起往外或往內運動，而無振膜分割現象的時候。

好費解啊， 是不是啊？

好費解啊， 是不是啊？

好費解啊， 是不是啊？

請記住他們的名字：

Albert Neville Thiele, OAM (4 December 1920 – 1 October 2012), generally known as Neville Thiele and publishing under the name A. Neville Thiele, was a distinguished Australian audio engineer.

Thiele was born in Brisbane, Australia. He was particularly noted for his work on electronic filters and on developing the Thiele/Small parameters for characterising loudspeakers as an aid to loudspeaker cabinet design. He died in Sydney, Australia.

Richard H. Small (born 1935) is an American scientist, who has worked mainly in the field of electroacoustics. He is known for the commonly used Thiele/Small parameters for loudspeaker enclosure design, which are named after Small and his colleague Neville Thiele. Small was born in San Diego, California. His father was an amateur pianist. Having a keen interest in electronics he built the amplifiers to drive the speakers in his parents house. His father built various enclosures for the loudspeakers, following the trends of the times. He earned a Bachelor of Science degree from the California Institute of Technology in 1956 and a Master of Science degree in electrical engineering from the Massachusetts Institute of Technology in 1958.