Tuning Qes Qts Bl Mms

[P Zolt]

Qes=1/(ws*Cms*Res) and Cms=Vas/(rho0*c^2 *Sd^2) and Res=(Bl)^2 / Re
Bl=sqrt((rho0*c^2*Sd^2*Re)/(ws*Vas*Qes))
Qes=w0*Mms/((BL)^2/Re)=w0*Mms * Re/(BL)^2
Qts value is determined by Qes=ws*Mms/Res, where Res=(Bl)^2/Re
BL = f(Fs, Vas, Qes, Qms, Re, Sd)
Formula from the board. I have no idea how to use.

Using Unibox Software
+Qes = +Qts = -BL
+Re = -Spl
Can I assume +Mms = +Qes =+Qts =-Bl
A change in the voice coil Re does not effect Qts yet really drops Spl = not good.
If I raise Qes (driver Re at Fs) the Qts goes up to a very nice .38 = great
and SPL drops by 1 db, mostly in the midrange leaving the bass intact. Slight drop in BL.
A higher Qts of .38 is an ideal situation for this Pro driver. Can I do this ??


Power Applied 50W
Fs 38.2
Re 5.0 Ohm
Qms 7.73
Qes 0.32
Sd 858.0
Vas299.0L
Xmax 5.5mm

SPL at 1 W 1 m 99.1 db
SPL at 2.83 Vrms 1m 101.1 db
Qts 0.307
Effective Qts 0.307
Mms 60.03g
Cms 0.289mm/N
Rms 1.864 Kg/s
Bl 15.00Tm
Ref efficiency, n 5.007%
Applied voltage 15.81 Vrms
========================

Now with a change to Qes of .40

SPL at 1 W 1 m 98.1 db
SPL at 2.83 Vrms 1m 100.2 db
Qts 0.38
Effective Qts 0.38
Mms 60.03g
Cms 0.289mm/N
Rms 1.864 Kg/s
Bl 13.42Tm
Ref efficiency, n 4.006%
Applied voltage 15.81 Vrms

I will be adding Dammer Varnish to the cone area to change the sound and add mass.
Is this the trick for a higher Qts higher Qes lower Bl yet leaving the Voice coil Re as is ??
How many grams need to be added for a Qts of 38.
I can post a jpg of Parameters or SPL plot, just ask TIA

 

[markp]

You will not be changing Re by coating the cone. You will be changing Mms, which will affect Qms and Qts.

 

[RobM]

You will not be changing Re by coating the cone. You will be changing Mms, which will affect Qms and Qts.

Fs and Qes, too. Fs will go down, Qms, Qes, and Qts will go up.

 

[markp]

Fs and Qes, too. Fs will go down, Qms, Qes, and Qts will go up.

Yep....

 

[MethMan]

what's happens with Cms and Bl? Stays the same? I Try to calculate added mass for spkr. I have no suitable software for it.

Now:
Qms=1,85
Qes= 0,44
Qts=0,36
Mms=65g
Cms=330e-6
Fs=35
Bl=13,3
Re=5,6

My resuts for added 45g:
Qms=2,61
Qes=0,58
Qts=0,47
Mms=110g
Fs=26,4

I assumed the Bl and Cms stays same. Is it true?

OTOH I can see small (3%) difference in parametres (could be affected with changing Cms) in table in Dickanson's LDCookbook. Misfortunately the mentioned part is very brief. There is a reference to Tom Nouissiane (probably distorted name- sorry) article in Speaker Builder from 80's which isn't procurable for me.

 

[Ron E]

CMS and BL are constants.

(Fs/F1)^2=(Mmt+Mass added)/Mmt
Qe1 = Qes*(Mmt+Mass added)/Mmt
Qm1= Qms *(Mmt+Mass added)/Mmt

Vas is constant

 

[Ron E]

Sorry, brain slip.
CMS and BL are constants.

(Fs1/Fs2)^2=(Mmt+Mass added)/Mmt
Recalculate Qes and Qms with new Mmt and Fs2.

Vas is constant

 

[MethMan]

Clear. Thanks.

 

[planet10]

Fs will go down/ Qts will go up.

a graphic example

dave

 

[MethMan]

Btw. I've got advice that paint, with exception of say resin-based thin impegnacy of the cone just for light stiffening, is not so good solution of adding mass because of higher loading or even possible overloading loudspaker's joints. Right solution is to fasten interrupted-ring shaped ballast made of non-magnetic metal directly into the former.

 

[planet10]

Or as suggested by John Cockcroft...

http://www.t-linespeakers.org/projects/cockroft/appendix.html
Wallflower -- Appendix

An externally hosted image should be here but it was not working when we last tested it.

dave