T/S parameters Flashcards
What are the main TS parameters needed for enclosure design
FS, QTS, VAS
Where do the T/S parameters get their name from?
Neville Thiele & Richard small. Who wrote a paper on intimate baffle / bass reflex enclosures
Another word for T/S parameters
Small signal parameter
What is “FS”
Resonant frequency in free air / the driver moves with minimal effort.
(Corresponds with the impedance spike)
What is “Q”
Quality factor / damping factor.
A unit-less measurement.
Speaker damping helps the cone resume its rest state.
The damping ensures the cone goes back to point 0 in a controlled manor.
As damping goes up, Q goes down. It is widely accepted that Q is the measurement of damping.
What is “QMS”
Mechanical Q
The damping made by suspension of the driver. (The surround and the spider)
What is “QES”
Electrical Q
The damping made by the coil / magnet assembly.
As the coil is an an inductor, when it moves through the magnetically field it has the property of inductance. This will generate a motion that opposes this motion called “back EMF” (electromotive force)
What is “QTS”
Total Q of the driver
Damping made by QMS and QES combined.
Formula- 1/QTS=1/Qes+1/Qms
What is “CMS”
The compliance of the speaker in meters/newtons
Stage stiffness of suspension (more stiff = less compliant”
Because of this, I higher cms = a lower FS
Higher cms will yield lower fs as the suspension is looser
What is “VAS”
equivalent compliance but vastly is expressed in terms of volume.
What is “RE”
The DC resistance in OHMS
Not to be confused with impedance. The re is measuring the cone as a resistor. The RE is generally lower than the nominal impedance.
What is the impedance
The AC resistance. This is not a fixed value. Generally displayed as the “nominal impedance” to keep it simple. This is the mean value.
What is “Xmax”
The maximum distance the cone can travel without distorting (mm)
Xmech
The maximum distance a speaker can travel without damaging the driver. (Mm)
SD
The effective area of the cone
Measured by a he middle of the suspension side to side.
MMD
Moving mass (g)
The weight of all moving parts (coil, cone, half of the surround, half of the spider)
MMS
MMS= MMD + mass of air in front of cone.
When you add all the components that make MMD then add this to the air in front of the cone.
The pocket of air in front of the cone moves in sync with the driver and his it’s own mass. This is taken into consideration when calculating the total moving mass.
This combined with the cms will affect the fs. (Suspension stiffness mixed with weight of moving parts will affect the fs)
High MMD - lower frequency
