Qes, Qts, Qms???

 

New member
Username: Reaudio

Post Number: 5
Registered: May-04
I just wanted to know about Qts, Qes, and Qms and what it has to do with the subs and there performance. Mainly just wondering what they mean? Thanks
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 3199
Registered: Dec-03
Thiele-Small Parameters

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

BL
The magnetic strength of the motor structure.

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 driver's 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.

L
length of wire immersed in magnetic field, in meters

Lces
The electrical inductive equivalent of Cms, in henries

L
Length of wire immersed in magnetic field, in meters

Ms
The total moving mass of the loudspeaker cone.

Mmd
Diaphram mass, in grams

Mms
The driver's effective mechanical mass (including air load), in kg

n0
The reference efficiency of the system (eta sub 0) dimensionless, usually expressed as %

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

Pa
Acoustical power

Pe
Electrical power

Q
The relative damping of a loudspeaker

Qa
The system's Q at Fb, due to absorption losses; dimensionless

Qec
The system's Q at resonance (Fc), due to electrical losses; dimensionless

Qes
The driver's Q at resonance (Fs), due to electrical losses; dimensionless

Ql
The system's Q at Fb, due to leakage losses; dimensionless

Qmc
The system's Q at resonance (Fc), due to mechanical losses; dimensionless

Qms
The driver's Q at resonance (Fs), due to mechanical losses; dimensionless

Qp
The system's Q at Fb, due to port losses (turbulence, viscousity, etc.); dimensionless

Qtc
The system's Q at resonance (Fc), due to all losses; dimensionless

Qts
The driver's Q at resonance (Fs), due to all losses; dimensionless

R
Ripple, in dB

Ras
Acoustical equivalent of Rms

Res
The electrical resistive equivalent of Rms, in ohms

Revc
DC voice coil resistance, in ohms

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

Rms
The driver's mechanical losses, in kg/s

Sd
Effective piston radiating area of driver, in square meters

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

Vas
"Equivalent volume of compliance", this is a volume of air whose compliance is the same as a driver's acoustical compliance Cms (q.v.), in cubic meters

Vd
Maximum linear volume of displacement of the driver (product of Sd times Xmax), in cubic meters.

Xmax
Maximum peak linear excursion of driver, in meters

does that help?
 

New member
Username: Reaudio

Post Number: 9
Registered: May-04
Yes it helps for the technical definition of it but i was wondering if you need to think about those when building a box or if a higher Qes or Qts is better or worse.
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 3262
Registered: Dec-03
Electrical and Mechanical Q will hae an effect depending on the type of box you're building, but honestly unless you're calculating for a custom bandpass, TL, or folded horn type box, you really don't need that info for a sealed or ported box.
Those are fairly simple designs, and easy to tune simply based on the speaker size.
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