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Old 25th October 2008, 01:20 PM   #1
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Default adding mass to cone

It is possible to determine the T/S parameters by adding mass to the cone. Is it ever done to add mass permanently. What are the pro's and cons?
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Old 25th October 2008, 06:31 PM   #2
gedlee is offline gedlee  United States
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Added mass is probably the most common technique. Just make sure that you keep the added mass close to the voice coil connection to the cone. I have used clay but I prefer solder pieces (heavy lead) with a little dry adhesive as it makes a tighter fit to the cone - added mass must be firmly attached to work right.

I have added mass to a speaker in subwoofer apps for example. I just glue on pieces of solder. Balance it as well as possible.
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Old 25th October 2008, 11:04 PM   #3
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Is there method for calculating the new specs?
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Old 25th October 2008, 11:49 PM   #4
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Quote:
Originally posted by mitchyz250f
Is there method for calculating the new specs?

I dont' think so. You'll need to run a test with a dedicated woofer tester instrument. They are for sale at PE.
The classic Snell Model A used add mass on the RCF 12 inch woofer. They poured a resin around the porous dust cap to about 1/2 inch depth. It lowers the Fs and efficiency is sacrificed as the trade-off.
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Old 26th October 2008, 12:22 AM   #5
gedlee is offline gedlee  United States
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Quote:
Originally posted by mitchyz250f
Is there method for calculating the new specs?

If you look up the basic equations for TS parameters its easy to see what added mass will do. It lowers Fs and raises both Qes and Qms.
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Old 26th October 2008, 01:04 AM   #6
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Quote:
Originally posted by speakerdoctor



I dont' think so. You'll need to run a test with a dedicated woofer tester instrument. They are for sale at PE.
There are other options.
For next to nothing with Speaker Workshop and a handful of parts.
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Old 26th October 2008, 06:17 PM   #7
Dr_EM is offline Dr_EM  United Kingdom
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WinISD Pro can simulate a box and allow you to add mass to the driver to see the effect it will have on the driver in that box. Ideal if your doing a ported or sealed box
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Old 26th October 2008, 06:33 PM   #8
HK26147 is offline HK26147  United States
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For purposes of testing "poster caulk" ( sold at office supply stores ) works ( see audioXpress November 2008 p 35 ).
Usually 200 grams or less is used.
For permanent application - lead ( as in solder recommended above ).
Also lead foil is sold in golf pro shops
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Old 27th October 2008, 01:18 AM   #9
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I have the free version of WinISD. How do i make the changes to simulate additional weight?
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Old 27th October 2008, 02:40 AM   #10
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This is just a thought as I've not tried it, but would epoxy with a suitable filler like barium oxide or powdered nickel be any good for adding mass permanently??.
I ask as I still have a litre of West Systems epoxy and powdered aluminium and stainlees stell left over from a heatsink experiment.
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