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<blockquote data-quote="keep_hope_alive" data-source="post: 7578990" data-attributes="member: 576029">nope.&nbsp; you need diffusion to break up back waves - and in order to be effective, teh diffusion needs to be 1/4 wavelength.&nbsp; think about what that means at 500Hz.&nbsp; //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gifpolyfill isn&#039;t as effective as fiberglass - i would choose the latter.&nbsp; even still, the effectiveness depends on the thickness which determines which frequencies are effected.&nbsp;&nbsp; most if it&#039;s effect is to convert sound energy to movement.an egg shape has less benefit for diffusion but more benefit for backwave control.when i build midrange eggs/spheres i&#039;ll use concentric wood rings so my inside shape is irregular.&nbsp; then i&#039;ll fill the outside for a smooth finish (foam/glass/clay/filler/etc.).&nbsp; but you&#039;ll still want to achieve a Q around .707 so you&#039;ll want to do some calcs to figure out airspace requirements.you can vent the enclosure into the dash - but think also about what that means for tuning, response, and phase interference as that sound makes its way around the dash cavity.lining the back of the cap with deadener will change the resonance frequency of the material used, but won&#039;t make a difference in airspace or backwave control.</blockquote>

[QUOTE="keep_hope_alive, post: 7578990, member: 576029"] nope. you need diffusion to break up back waves - and in order to be effective, teh diffusion needs to be 1/4 wavelength. think about what that means at 500Hz. [IMG]//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif[/IMG] polyfill isn't as effective as fiberglass - i would choose the latter. even still, the effectiveness depends on the thickness which determines which frequencies are effected. most if it's effect is to convert sound energy to movement. an egg shape has less benefit for diffusion but more benefit for backwave control. when i build midrange eggs/spheres i'll use concentric wood rings so my inside shape is irregular. then i'll fill the outside for a smooth finish (foam/glass/clay/filler/etc.). but you'll still want to achieve a Q around .707 so you'll want to do some calcs to figure out airspace requirements. you can vent the enclosure into the dash - but think also about what that means for tuning, response, and phase interference as that sound makes its way around the dash cavity. lining the back of the cap with deadener will change the resonance frequency of the material used, but won't make a difference in airspace or backwave control. [/QUOTE]

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