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4.06.02
Brief description of the project:
I had found a great seller on eBay that carries good name brands at after-stock prices that I can never beat. So whenever I get a chance to check out their auctions, I do... and 6 times out of ten or 3 out of 5 times I check their auctions, I just have to get something. Well, when I had stumbled upon this sub, I really wanted a trio of them. The sub is a PPI (Power Precision Inc.) C1 series 12" sub, with an 8ohm resistance. Can you see why I would want 3???
In any case, it was a dutch auction and I got outbid by a dollar on the other 2 subs... so I got stuck with one, though it only cost me \$25 US. Can't beat the deal. I recently had a friend of mine show interest in the sub, but to entice him even further I made some ridiculous deal by telling him I'd charge him $25 for a custom box.
In order for this guy to get the bass that he wanted while not fully understanding anything I happened to be talking to him about, I suggested a ported enclosure would give him somewhere around the ballpark of +3db in efficiency, and with a single 8ohm load and 300 watts of power handling, I knew he could use it. The speaker came with a spec sheet from the factory that suggested a 1.25 cubic foot ported enclosure with 1 3"x5" port. However, I ran these numbers through some calculations and found that it tuned the port in like the 60hz range.... I want SPL, but damn where is the music??
So, I designed a 1.75 cubic foot box with not 1 but 2 3" diameter ports at 11" long. This brings port tuning downwards toward 35hz, which is what I was musically looking for. The graphs that I had run from the simulations suggested around 122db max SPL in car... with a little funny peaking right around port tuning freq. Not bad for a single 12" sub for \$25.
In any case, I constructed the box using 3/4 MDF as the back "shell" and 3/4" particle board for the baffle. This was wood I had laying around.... so I used it. I added an extra brace to the center of the baffle board, filed and rounded the insides of the ports and also pretty much bathed the baffle board in wood glue. There is actually a 1/8" rise (literally!!) on the back of the board due to the amount of glue... And yes this is a universal rise.
As far as output is concerned, I'm quite happy. I was able to hook up a Pioneer 300 watt amp (not a bad amp at all!!!) and run the sub off of one channel for break in purposes. Well, using Master P's "Make 'Em say Ugh!" I was able to hit a constant 116db and had peaks upwards of 121db. This measured 2 inches from the windshield, passenger side, then again at dead center. All in all an impressive sub.
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