2 x XLS10 / vented box + added mass?

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Lo,

I'm messing about with Winisd at the moment looking at configurations for 2 subs to form the bottom sections of a new loudspeaker project.

I'm thinking of side firing subs mounted back to back in a push push configuration to cancel vibrations, in a vented enclosure.

If I go for a 60l enclosure tuned to 24Hz and add 25g mass to each cone, I get a modelled response that looks like the attached pic. This looks good to me but is adding mass a bad idea? I don't want to end up buying 4 x XLS drivers and 2 plate amps if I'm likely to realise a totally different response from actual speakers.

Should I just stick to using a PR and single driver per side instead and try to deal with the vibrations induced in the rest of the cabinet in another way?

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Sorry - I didn't search properly - would a mod please delete this thread - apologies.