Miata Trunk Sub
sorry no reply yet, had to work today and dont want to bust out the forum at a new job juuuuuuust yet.
so ok first order of business is a tool:WinISD free
Second, find some information on the subs you can get ahold of (and afford).
WinISD is easy enough to use so here's a brief tutorial for the awesome y8s mini trunk sub design method.
1. pick a woofer with known Thiele-Small parameters (Qts, Fs, Sd, and Vas I think are the minimum you need). 2. enter this data as a new driver in WinISD and save it 3. create a new project with the "own driver" that you just entered. regardless of the little bar in the wizard, create a "sealed" box. 4. on the "Box" tab, you can drag around on the graphic and it'll resize the box. You can also type in the volume you want. (click on the units to cycle through ft3, m3, in3, L, etc.) 5. Aim for a -3db point (use the graph) of 55-60Hz and a Q (box tab) of .65-.85. 6. click on the "box shape" button and put in the thickness of the wood and hit "optimum". If you want to change dims, enter two and click the L W or D for the 3rd to auto-calc it. Again, click on in/m/ft/etc to change units for each cell. Remember mounting diameter and depths plus air space! I stuff my boxes with pillow stuffing (ask your mom) and usually the stuffing counteracts the volume of the driver basket approximately. 7. Build the box and test it out. make sure you turn off your bass boost on your subs amp.
If it's rattly but doesn't have punch, the box is too big. Take out the stuffing.
If it's too punchy/chesty and makes your hair twitch but doesn't have any deep sound, it's too small. Add a bit more stuffing.
NOTE: Not *every* sub will work for this. Some will be close and some will not. Some good starting points for Thiele-Small Parameters are: Fs: between 20-28 Hz Qts: between .25-.35 Vas: Lower means a smaller box. Stay under 100 if you can. Sd: depends on woofer diameter. area of a circle the diameter of the center of the surround. Xmax: bigger is better
It may be easier to find non-car subs with these numbers.
As far as the CAR is concerned, I did nothing to the tunnels or parcel shelf. Just threw a box and big amp in the trunk. Works like a dream.
