Sealed Box: poly fill, egg crate foam or both?

I'm building a pair of kit sealed box LS3/5a clone speakers. The kit is supplied with egg crate foam for interior walls. I thought sealed box speakers all needed loose poly fill of some sort. Should I use egg crate foam, loose poly fill, or both? And if poly fill is needed, what type/brand do you recommend, and what amount?

Another question: these will be built with a traditional birch ply cabinet. What do you recommend for finishing the birch ply as far as stain, sealant, etc.? I'd like to keep it in its natural color or slightly darker at worst
 
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I would not recommend trying any modifications on an unfinished kit, that's not likely to get you anything. Build the kit as instructed, trust the designer...unless you somehow know more about it than the designer! ;) Adding poly fill will likely change the frequency and shape roll-off slope of the high pass response of the woofer.
Just build it, follow any usage recommendations the kit instructions may suggest...and sit back, relax and listen.
Oh, one more thing...new speakers generally need at least a few hours of break-in time to get the cone suspensions and spiders properly loosened up, so for the first couple of weeks, play a lot of music; stuff with prominent bass and mids are best here...and don't be to critical of what you hear at first, they usually settle in and sound better with passing time...and your ears also "break-in" to the new speakers over time.

Mike
 
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It’s easy to experiment with a puff of polyfill. It’s reversible and you can listen for yourself. Stuffing will increase the effective volume of a box and extend the bass deeper. It will do so at expense of lower SPL. I would personally never use a sealed speaker with only eggcrate foam.

Try boiled linseed oil. It penetrates the wood and cures to a hard almost plastic like matrix. Give coats 2-4 days to cure. On second coat rub the wet BLO with ultra fine sandpaper and it makes particles of wood mixed with the BLO fill all the micro surface features to leave a smooth satin finish.

Be careful with fire safety. Rags wet with BLO will spontaneously combust if wadded up and put in trash. Soak in water and leave wet in a metal tin, or let dry flat on concrete before throwing away.
 
I'm building a pair of kit sealed box LS3/5a clone speakers. The kit is supplied with egg crate foam for interior walls. I thought sealed box speakers all needed loose poly fill of some sort. Should I use egg crate foam, loose poly fill, or both? And if poly fill is needed, what type/brand do you recommend, and what amount?

Another question: these will be built with a traditional birch ply cabinet. What do you recommend for finishing the birch ply as far as stain, sealant, etc.? I'd like to keep it in its natural color or slightly darker at worst
The BBC document should tell you what to do and why. Generally, egg crate foam has very little acoustic benefit. The LS3/5A is a thin wall cabinet design that needs better wall damping.

http://downloads.bbc.co.uk/rd/pubs/reports/1977-03.pdf

On the other hand, if you build the speaker kit as provided and like the sound, then it is end of story.

Just curious, what kit do you have?
 
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