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Old 17th November 2008, 07:27 AM   #1
FlipC is offline FlipC  United States
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Default How to figure out unknown specs?

So if you only have the following info on a driver:
Quote:
*Power handling: 300 watts RMS *VCdia: 2" *Le: 1.73 mH *Impedance: 8 ohms *Re: 5.98 ohms *Frequency range: 48-3,300 Hz *Magnet weight: 59 oz. *Fs: 33 Hz *SPL: 98.6 dB 1W/1m *Vas: 11.1 cu. ft. *Qms: 5.13 *Qes: 0.32 *Qts: 0.30 *Xmax: 3.0 mm *Dimensions: A: 15.15", B: 13.77", C: 5.94".
How can you figure out:
SD.Cms Mmd,Bl, and Rms ?
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Old 17th November 2008, 07:38 AM   #2
simon5 is offline simon5  Canada
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You can't.

You need at least one more parameter to fill out missing parameters.

You would need either Mmd, BL, Cms, Dd, Rms or Sd.

Sd woud be easy to approximate... then you get all missing ones.
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Old 17th November 2008, 08:21 AM   #3
BHTX is offline BHTX  United States
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Quote:
Originally posted by simon5
Sd woud be easy to approximate... then you get all missing ones.
I find myself having to do this often..
All you need to know is the average Sd for drivers of a given diameter.
Actually, I kinda have a bit of a window.. with pro drivers, I go a bit larger. With hi-fi woofers with larger surrounds, I usually go a bit smaller. Usually, I often just compare the Sd of similar drivers in WinISD Pro that I've already entered in the past. Works fine. Nothing's perfect, and the provided T-S parameters from manufacturers alone will leave you with far less accuracy than estimating Sd will.
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Old 17th November 2008, 11:19 AM   #4
djk is offline djk
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It's a 15, just use 850 for the SD.
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Old 17th November 2008, 05:17 PM   #5
FlipC is offline FlipC  United States
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I was suing 850 as SD but I was curious if
there was a way I didn't know about to figure it all out.
Thanks for the replies.
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Old 17th November 2008, 06:12 PM   #6
Ron E is offline Ron E  United States
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Quote:
Originally posted by djk
It's a 15, just use 850 for the SD.
850 in what units
- presumably 850 cm^2 or .0850 m^2

You can use the following as guess values for diameter for standard Lf units.

Frame size, piston diameter in mm, area in cm^2
4", 80mm, 50
5", 100mm, 78
6", 130mm, 130
8", 170mm, 225
10" 220mm, 345
12", 260mm, 530
15", 330mm, 855
18", 400mm, 1250

This is for woofers with "normal" excursion capability, of approx frame diameter in inches / 2 [in mm] - so 6mm for a 12" driver. Really long excursion woofers will have a smaller piston diameter.
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Old 17th November 2008, 09:30 PM   #7
Thawach is offline Thawach  Thailand
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FlipC please try to see online calculator. but some valves u must measure before.

http://www.radiocollection.net/tsp_calc.html

Reg
TW
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Old 17th November 2008, 10:09 PM   #8
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Default Re: How to figure out unknown specs?

Quote:
Originally posted by FlipC


How can you figure out:
SD.Cms Mmd,Bl, and Rms ?

If Sd=850 then:
Cms=0,3069 mm/N
Mmd=75,93 grams
BL=17,153 N/A
And Rms=3,069 kg/second


Dag
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