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Old 8th May 2002, 04:27 AM   #1
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Join Date: May 2002
Question adding mass to subwoofer to lower fs

I would like to add 10 grams of something I can paint on to my subwoofer, in the new "winisd pro" program it has a variable for adding mass to the cone and the effect it has on the freq response. I found adding 10 grams is beneficial to extending the response.

1: What can I use to paint on the subwoofer? I heard you can use elmers glue. Maybe I could glue 2 nickels on the cone! ~(paper/kevlar composite cone)

2: is it bound to degrade the performance of the magnet/motor assembly significantly thereby reducing the magnets control on the cone (break up more easily)?

Thank you for any input!
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Old 8th May 2002, 02:52 PM   #2
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Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
David Weems, who has written several books and articles on loudspeakers, has dealt with this in the past.

He points out that when you add mass to the cone, you decrease overall system sensitivity as well as lower the Fs.

He suggested that you can lower the Fs by one quarter octave, but not to go farther.

Although Weems did not say so, I think all you are doing is bringing your midbass down so that what used to be your 6 dB down point becomes your 3 dB down point-because your midbass reference is 3 dB lower.

In other words-and Weems did not say this specifically, but I think he is hinting at this-if you have a speaker that, at 1 watt, delivers 83 dB at 42 Hz, then with the extra mass it will still deliver 83 dB at 42 Hz-the only difference being that the output at 150 Hz will be lower due to the extra mass.

At any rate, if you want to try it, he did mention pennies and nickels glued to the cone as a way to accomplish this.
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Old 13th May 2002, 08:15 AM   #3
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No, don't try it. Adding mass will decrease SPL and increase Qes. The best way is using a Linkwitz Transformation Circuit. Look up True Audio. There is an article on it.
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