Hi all. I started constructing a box for a 12" shallow pioneer sub (ts-sw124d fs-31Hz, qts-0.55 qes 0.56) ) using 10mm Pressed Wood (think its also called particle wood). The reason for this is that I have VERY limited space (pickup). The only way I can get to Pioneer's recommended 0.8 cu ft is to use 10mm (0.39") wood. I have a large enough piece in the garage and want to build a "proof of concept" box. I see everywhere that the recommended wood is 3/4" MDF. Do you guys think it’s a total waist of time and glue to continue or would it be better to use ticker / stronger wood and loose out on the cu ft? I was thinking of using bracing etc. (with bracing I could still end up with sufficient cu ft). I want to make a sealed box first.
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Nick
Nick - I'd use stronger wood. Stuff it with acousta-stuff. The problem with 10mm is that unless you use A LOT of bracing you'll get some significant wood resonance.
But hey, you have the wood, I say give it a shot. Something to try is to buy some damping material and line the inside of the box with it.
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New Project: 2003 Pathfinder
The amount of space you save by giving up that 3/8" on the walls is insignificant compared to the poor response you'll get if the walls flex. Generally, the volumes given in manufacturer's specs are smaller than ideal for the sub, anyway, so a few hundredths of a cu foot isn't going to mean much. If you want to use the wood you have, double-wall it, using screws and glue. Use polyfil stuffing to expand the perceived air volume. Adding bracing to a box that small will not end up worth the accumulated cubic inches the bracing will take up, and actually might end up taking up more air space than the thicker walls would. And you are adding woofer displacement to the target volume, I presume?
Hi, thanks for replies. Based on some calculations I have done, the diff in volume is: 10mm - 0.76cu ft (still below recommended .80cu ft and woofer displacement not even considered in my calculation!) to 3/4" - 0.633cu ft. To me this sounds like quite a lot (percentage of total volume). I guess the flexing is not major worry as thus far the box feels pretty solid and I'm thinking of using 16mm + for front. I'm more concerned with the box resonating... Max dimensions for box that will fit behind the seat - width: 26.77", height1: 5.12", height2: 3.22", depth: 14.17" (all outside measurements).
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Nick
Edited: After looking at this again with fresh eyes, your numbers look correct. And using two layers of 10mm (rather than 3/4 MDF) makes it even more of an infringement on available space. But you'll have to be inventive to find a way to build the enclosure very solid, spec'd with the proper 3/4" walls, and still have the air space needed for performance.
The sub itself will probably be about .07 cu. ft. and will have to be accounted for (you'll have to look it up in your specs). The best response from the sub will most likely be at the upper volume rather than the minimum. Look for a way to create an offshoot of the box to encompass more air space. (The box can be oddly designed.) Adding polyfil will give the box about 20% more volume, too.
Flexing will be an issue with sub freqs...believe it. You mentioned resonance...but that is another way of talking about the same thing. It just takes an imperceptible amount of flex on the long side of a box to cancel out the impact of a bass hit.
Seeing the very flat nature of your box, a couple of well placed front-to-back braces should be called for, even with double 10mm or 3/4" walls. Use threaded bolts or dowel rods to save air space. Good luck.