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Old 2nd August 2010, 09:07 PM   #1
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Default Qts Qes Qms WTF?

im new to this and i am having a hard time understanding Qts Qms Qes. it seems to be the mecahanical and electrical damping of a speaker. can someone please explain very slowly to me what this means?

i am used to seeing damping used in electrical engineering diagrams on paper, solved using differential equations. im not sure if this is even the same kind of damping. ex: over/under/critical damping

if someone could put some real world words to this it would help me a lot.
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Old 3rd August 2010, 12:29 AM   #2
Ron E is offline Ron E  United States
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Quote:
Originally Posted by scampo77 View Post
i am used to seeing damping used in electrical engineering diagrams on paper, solved using differential equations. im not sure if this is even the same kind of damping. ex: over/under/critical damping
All that really matters for designing sealed speaker enclosures is Qts
Qtc=Qts*sqrt(Vas/Vb+1)
Fc=Fs*Qtc/Qts
Transfer function: H(s)=sn^2/(sn^2+sn/Qtc+1) : sn=normalized frequency
Qtc=0.5 is critically damped....

For anything else, go to wikipedia, or go to The Subwoofer DIY Page - applicable to more than just subwoofers..
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Old 3rd August 2010, 02:40 AM   #3
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thanks for the response but you told me almost nothing. what im looking for is someone who understands this topic enough to be able to explain electrical/mechanical damping in REAL words or possibly an analogy.
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Old 3rd August 2010, 03:25 AM   #4
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Quote:
Originally Posted by scampo77 View Post
im new to this and i am having a hard time understanding Qts Qms Qes. it seems to be the mecahanical and electrical damping of a speaker. can someone please explain very slowly to me what this means?

i am used to seeing damping used in electrical engineering diagrams on paper, solved using differential equations. im not sure if this is even the same kind of damping. ex: over/under/critical damping

if someone could put some real world words to this it would help me a lot.
The Qms is a measure of the damping caused by the mechanical damping of the diaphragm suspension. A higher Qms means less mechanical damping.

The Qes is a measure of the electromechanical damping caused by voice coil resistance and the interaction of the voice coil in the magnetic gap. A higher Qes means less electromechanical damping or a smaller magnet.

The Qts is the total damping which is the combination of mechanical and electromechanical damping.

Qms is always much larger than Qes because the electromechanical damping always dominates.
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Old 3rd August 2010, 03:51 AM   #5
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Qts: the higher the number = the drivers inability to come to rest after the electrical signal has ceased. a rating of 0.707 is just right for a lot of folks. If you like drier bass, around 0.5 - 0.6 is better. if you like speakers from the 70's, a little higher 0.8 - 1.0 will make your ears happy.
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Old 3rd August 2010, 04:12 AM   #6
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Will "Loudspeaker Cook book" by Vance Dickason be helpful ?
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Last edited by ashok; 3rd August 2010 at 04:15 AM.
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Old 3rd August 2010, 04:44 AM   #7
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probably if it helps explain TS parameters a bit better
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Old 4th August 2010, 01:30 AM   #8
Ron E is offline Ron E  United States
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Quote:
Originally Posted by scampo77 View Post
thanks for the response but you told me almost nothing. what im looking for is someone who understands this topic enough to be able to explain electrical/mechanical damping in REAL words or possibly an analogy.
No, you want to be spoon fed an answer, but I'm not your caregiver.

Here's your analogy.
mechanical damping = shock absorber
a velocity dependent force dissipating the energy in the suspension and cone mass.

electrical damping = motor back emf try spinning a small DC electric motor with and without the power terminals shorted. also velocity dependent and dissipative, but sourced from the motion of the coil in a magnetic field, acting through the resistance of the coil + wires + amplifier output impedance. Ever heard of Lenz's law?

Good luck.
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Last edited by Ron E; 4th August 2010 at 01:43 AM.
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Old 4th August 2010, 11:18 AM   #9
HK26147 is offline HK26147  United States
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A good portion of this title can be previewed ( Google Books )...
Loudspeakers: for music recording and reproduction By Philip Newell, Philip Richard Newell, Keith Holland
Chapter 1 : What is a Loudspeaker?
On page 14 ( fig 1.7 ) is an equivalent circuit.

( This might help - Syd )
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Old 5th August 2010, 01:28 PM   #10
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so from what you guys are saying it seems like it is the mechanical and electrical drag or inefficiencies in the speaker? or the speakers "run on" after the music stops

i read the Qts dominates the box volume if this is true why would a speakers inefficiency determine box size?

ive some across lenz's law in school but never more then just touched on it in class. i can see how this would add to the speaker "stopping itself unnecessarily and all of these answers seem to be clearing things up for me, thanks everyone
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