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Old 30th December 2009, 09:51 PM   #1
markusA is offline markusA  Sweden
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Default Jordan fx92s experiences?

How well does the datasheet compare to the actual measured values of the drivers? Jordan fx92s
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Old 30th December 2009, 11:41 PM   #2
MJK is offline MJK  United States
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Here are my measured T/S parameters.

DRIVER #1

=praxis= Thiele/Small Parameters
__________________________________________________ ____

__________________________________________________ ____

Qts = 0.526 Total Q
Qes = 0.712 Electrical Q
Qms = 2.008 Mechanical Q
Fs = 49.751 Hertz, Free Air Resonance
Res = 5.3 Ohms, DC resistance
Ls = 119.6u H, series inductance
Lp = 139.3u H, lossy series inductance
Rp = 989.7m Ohms, loss across Lp
Dia = 100m meters, effective
(%shift) 39.4 %, resonance with mass
Vas = 15.46 litres, air volume equivalent
mms = 5.733 grams, effective mass
cms = 1.785m m/N, compliance
bl = 3.652 T*m, motor strength
n0 = 257.1m %, max efficiency
SplSens = 86.10 dBSPL max @1W absorbed
(Added mass) 10 grams

__________________________________________________ ____


DRIVER #2


=praxis= Thiele/Small Parameters
__________________________________________________ ____

__________________________________________________ ____

Qts = 0.522 Total Q
Qes = 0.700 Electrical Q
Qms = 2.050 Mechanical Q
Fs = 49.742 Hertz, Free Air Resonance
Res = 5.3 Ohms, DC resistance
Ls = 131.7u H, series inductance
Lp = 139.6u H, lossy series inductance
Rp = 962.8m Ohms, loss across Lp
Dia = 100m meters, effective
(%shift) 39.6 %, resonance with mass
Vas = 15.60 litres, air volume equivalent
mms = 5.682 grams, effective mass
cms = 1.801m m/N, compliance
bl = 3.667 T*m, motor strength
n0 = 263.8m %, max efficiency
SplSens = 86.21 dBSPL max @1W absorbed
(Added mass) 10 grams

__________________________________________________ ____


Hope that helps,
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Old 31st December 2009, 02:29 AM   #3
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they do need warm up before the TS acquisition. Here's a cold driver.
Ones they are played for an hour or so and voice coil warms up, TS are on the dime.
Delta V of 1.2ft used.
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Old 31st December 2009, 09:19 AM   #4
markusA is offline markusA  Sweden
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MJK> Do you remember if those measurements are from a "cold" unit?

R-Carpenter>Pardon me if I'm a litte slow but english is not my native language. To be absoulutely clear, do you mean that the measured data corresponds exactly (or very close to) to the drivers data sheet after they are warmed up?

My reason for asking is this. Years ago I modelled an enclosure and built it based on the TS found in the data sheet. I never finished the speakers due to poor economy. A week ago I decided to finish the project.
I'm worried the box is all wrong because I didn't use measured data, only what the manufacturer posted on his website.
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Old 31st December 2009, 01:01 PM   #5
MJK is offline MJK  United States
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Quote:
Originally Posted by markusG View Post
MJK> Do you remember if those measurements are from a "cold" unit?
I played music through my new Jordans for a few weeks before doing any measurements, probably 40 to 60 total hours. When I connect drivers to my measurement system I use 10 to 20 averages of the input signal to calculate the driver properties. I probably do this several times before getting the final results. These are all low level voltage/small deflection measurements. So I would characterize my results as being for a driver with some hours on them that have been running immediately prior to measuring at a low input power level.


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My reason for asking is this. Years ago I modelled an enclosure and built it based on the TS found in the data sheet. I never finished the speakers due to poor economy. A week ago I decided to finish the project.
I'm worried the box is all wrong because I didn't use measured data, only what the manufacturer posted on his website.
Any time you use only manufacturer's specs to design an enclosure or speaker system you take some risk. The manufacturer's specs might be very accurate or complete fiction, you won't know in advance.

Sometimes you can find measured driver properties on the Internet in a forum or documented in somebody else's design work. Maybe you could use google to see if anybody has real data on your specific drivers. But that can also be a risk, probably a little less than just using the manufacturer's data sheet.
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Old 31st December 2009, 02:40 PM   #6
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Quote:
Originally Posted by markusG View Post
MJK> Do you remember if those measurements are from a "cold" unit?

R-Carpenter>Pardon me if I'm a litte slow but english is not my native language. To be absoulutely clear, do you mean that the measured data corresponds exactly (or very close to) to the drivers data sheet after they are warmed up?
Correct. Some call it "burn in" but it has to do more with the temperature of the voice coil.
It is of cause best to measure yourself but I think you'll be fine with 92s.
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Old 31st December 2009, 03:03 PM   #7
markusA is offline markusA  Sweden
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In that case I'll hope for the best and remember to give them a good "burn in" before passing judgement.
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Old 31st December 2009, 03:07 PM   #8
markusA is offline markusA  Sweden
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MJK> Since R-Carpenter seames to have gotten measurements close to specs I'll keep my hopes up. Still it was very good to see your mesurements as well. (I'll remember not to get my hopes up to high)
I think it was you're MathCad spreadsheets I used for the modelling. It was years back but they were very nice to work with.
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Old 31st December 2009, 04:14 PM   #9
MJK is offline MJK  United States
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Originally Posted by markusG View Post
Since R-Carpenter seames to have gotten measurements close to specs I'll keep my hopes up. Still it was very good to see your mesurements as well. (I'll remember not to get my hopes up to high)
I think it was you're MathCad spreadsheets I used for the modelling. It was years back but they were very nice to work with.
If you used the Jordan datasheet properties to do the design calculations you are probably in good shape. Jordan's stated properties are a lot more accurate then the Fostex or Lowther manufacturer specified properties.
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