以前用另一ID發過，整理重發。
密閉箱體設計
T/S參數定義：
VAS，驅動器的空氣等效容積。VAS具有的聲順等于驅動器振動系統的聲順。
VAS=ρ·c↑2·
CAS
其中
CAS是驅動器支撐的聲順。
換種說法：
VAS是令驅動器諧振頻率提高到自由空間中數值的√2倍的密閉音箱中的空氣容積。
ρo：空氣密度
C：聲速
SD：等效輻射面積
Co：順性
驗證一下這條的式子
SEAS H1488-08 L16RNX
ρo：1.18 Kg/m↑3
C：344 m/s
SD：.0104m↑2
Co：0.0011m/N
計算結果
VAS=0.0166 m↑3，即16.6 Litres，seas提供的數據為 16 Litres
密閉箱箱體諧振頻率計算
Fc：箱體諧振頻率
Fo：單元諧振頻率
Vc：箱體淨容積
Vas：單元等效容積
驗證一下這條的式子
seas H416 P17REX
VAS: 30.5 Litres，
Fo: 34Hz，裝入淨容積 12 Litres閉箱，計算結果：
FC=63.9 Hz.
無聲室測試結果，看看阻抗曲線，准確性如何？
The Laboratory
The Seas laboratory is located in the south end of the Seas building, resulting in a very little traffic noise, and as far away as possible from our mechanical production. We have an anechoic chamber, a reverberation room (used today as a storage room), a laboratory with lots of measurement systems, offices, listening room, and two meeting rooms.
The south wall has only one opening of 1 x 1 m for free field measure infinite baffle measurements. This is today more an interesting curiosity since it’s no longer being used. In the basement, we have a well isolated room for long term power handling tests of loudspeakers. We also have an enormous storage room in the basement for physical storage of different projects and samples going back, more than 30 years
The anehoic chamber
The anechoic chamber consists of a shell of concrete and Leca that rests on coil springs (16 x 3 ) to dampen noise from vibration in the ground. The mass (approx 200 tons) together with the springs results in a 2. order low pass filter with a cut off frequency of 2.5-3 Hz. The dimensions inside the shell is ( L x W x H ) 960 cm x 650 cm x 755 cm.
All walls inside the anechoic chamber are covered with mineral wool wedges placed 5cm from the walls. These wedges together with the 5cm air layer represent an absorber/resonator which gives an absorption coefficient of more than 0.99 for frequencies above 70 Hz. The floor in the anechoic room is a net made from tensioned steel wires.
The entrance into the room consists of two coupled steel doors which opens outwards, together with a 1m thick frame construction with wedges which open inwards. Loudspeakers, microphones etc. can be connected to the measuring equipment outside the room with a sophisticated cable system. The cables are led into the room through noise traps.
A system of hooks from the roof and the floor gives us the possibility to mount different installations in different ways. The available room within the wedges above the wire floor is (Lx W x H): 750 cm x 440 cm x 480 cm. The room can be used for all kinds of free field measurements.
Our measurement systems
Klippel
We’re using the Klippel measurement system to develop and document.
WinMLS
The WinMLS is another very good measurement system, developed by Lars Morset in Norway.
SeasGraph
SeasGraph is our own viewer for all the different measurement system. We needed a really good program to compare and present our measurements, and ended up by designing our own computer software.
Comments to the datasheets
The resonance frequency (f0) and the impedance at resonance (Z0), are measured using a 2 VRMS sine signal.
Our woofers are measured in a closed cabinet with outside dimensions according to the table you will find here. The cabinet is loosely filled with damping material.
All loudspeakers are measured at 0.5 m/2.83 V on axis in our anechoic chamber using the TRF-module from Klippel GmbH. The microphone is a B&K 4133.
Before measuring the T/S-parameters the driver has been run in at near maximum excursion in free air using a sine signal at f0 for 2 min. The resonance frequency and impedance at resonance are measured using a 2 VRMS sine signal.
The moving mass and the BL-product are measured with the laser equipment from Klippel GmbH.
Below, you will find some information which may make it easier to interpret the technical data.
Power data is given with reference to IEC 168-5. The signal is white noise, shaped to a defined spectrum, and amplitude limited so that the peak voltage is two times the RMS voltage.
The maximum noise power which the drive units can take without permanent damage for sixty cycles consisting of one second ON and one minute OFF is the specified short term maximum power.
The specified long term maximum power is defined as above but with ten cycles consisting of one minute ON and two minutes OFF.
The mounting conditions in the above tests and during the sound pressure frequency response measurement are identical.
Voice coil inductance is a controversial topic since the loudspeaker impedance towards higher frequencies can not be represented by a simple inductor. We have calculated the inductance value at the frequency where the impedance has risen 3 dB from its minimum above the resonance frequency.
Resonance frequency fs is measured using 2 Vrms sine wave. Please be aware that differing power levels and measurement methods may give significantly different fs, and consequently different values for other parameters dependent upon fs.
Suspension compliance Cms (the inverse of the suspension stiffness or spring constant) is related to the moving mass Mms and the resonance frequency fs by the equation:
( 2 ∏ fs) ² . Mms . Cms = 1
Linear coil travel is the total distance peak to peak which the coil can move with no significant change in the force factor.
Maximum coil travel is the total distance peak to peak which the coil/cone can move without experiencing gross mechanical non-linearities and limitations.
密閉箱容積計算
Vc： 聲箱的淨容積，單位 Liter.
VAS： 單元的等效容積，單位 Liter.
Fc： 聲箱諧振頻率，單位 Hz.
Fo： 單元諧振頻率，單位 Hz.
