Sunday, December 26, 2010


 today i started working on enclosure. i am using 3/4" mdf for all sides and internal braces. it is cheap material and easy one to finish.
 all pieces cut to size. i might do some sanding to fine tune the fit.  now i need to rout circular opening for driver, openings in brace and cutout in back baffle for amp.

 routing window brace
all openings routed. next i will start gluing the box together.

today i managed to start assembling box together. i also installed hurricane nuts for driver attachment. i didnt enclose the box completely just yet as i will be sealing all the connections inside the box with caulk.

completed box. all glued together and inside connection caulked airtight.

next step is finishing mdf enclosure. i am going to attempt white glossy finish. first, i rough sanded all sides with finish sander and 80 grit paper. mainly i concentrated on mdf connections as these required most attention to be nicely smooth and flush. i didnt really touch anything else with 80 grit.
next i patched fine blemishes with speckling paste as i already had it. bondo or wood filler can also be used and are probably better way to go. when it dries i will sand it with 150grit. if it looks good i will follow with 220. if it doesnt i will do another round of speckling paste. 

i used countersunk hurricane nuts for leg inserts.
last thing to do was to chamfer all the edges just a bit.

Monday, December 20, 2010

diy subwoofer

i am building subwoofer to accompany my new ht setup. after a lot of research i decided for diy build. this way i can design whatever enclosure shape, volume (more about this later) and finish i want. this really matters as i want to blend it with our white interior and keep jana happy. it is still going to be somewhat monsterous box in order for it to sound good, but i can play with parameters and adjust shape and size to our satisfaction. also it will kill any mainstream brand sub on the spot for about half price. based on the volume of our living room i decided to go with 12" driver in sealed enclosure. sealed subs are known to be less efficient comparing to ported ones, but tend to be more accurate, smaller and simpler to build. and i can still port it later if i wanted to.

 for enclosure design i used winISD, which is freeware that calculates recommended enclosure volume based on thiele/small parameters. it is very simple program. the value that needs to be selected is Qtc, which basically is total resonance of speaker, whatever that means. the ideal value is 0.707, which should give flattest response and lowest possible f3 for a given driver. some people like it lower, but that enlarges enclosure volume significantly. higher Qtc will result in smaller enclosures, but too high values will result in "boomy" sound. i am going to play it safe and shoot for 0.69. that results in 3cf enclosure which with internal braces, driver volume and amp volume subtracted will give Qtc of around 0.71.  my curve looks pretty decent and gives f3 value of 36hz.

i ordered Dayton RSS315HF-4 12" Reference HF  4 Ohm driver along with bash 300 amp, mounting hardware and grill cloth and frame set from Parts Express. I am expecting delivery tomorrow.

i just got the shipment in. bash amp is on back order till february though. here are some images of dayton driver.

driver weights 25 pounds. size of the magnet itself is enormous.

also got cloth with frame set, mounting screws and hurricane nuts.

Sunday, December 19, 2010