My Car Sub Cab Part II
Well, the 10" Polk cab turned out less than stellar as a bass cab, as predicted. Adding a soft dome tweeter made it a pleasing two-way PA speaker, but it was too weak in the mids.
I tried crossing over the tweet dangerously low with a 1st order blocking cap at 2KHz, and in spite of predictions otherwise, experienced phase cancelation in the 1KHz region when I changed polarity. That proves the bulky Polk indeed had output well above its 200Hz rated upper range, which game me hope that pairing a car sub with a mid might give me results that were better...
Well, I have several subs sitting around from past projects, so I dusted off a 12" JL Audio W0 and ordered myself an Alpha 6 and some crossover components to make second order filters with a crossover point around 800 Hz. Since the JL is much less beefy than the Polk, I was confident 800 Hz was well within its abilities, though due to its inefficiency, I'd have to load up on resistors to tone down the Alpha. This will be a monitor and practice speaker, not a gigging powerhouse...
Sizing the new box to give the JL enough breathing room to perform well, I ended up with about 3 cubic feet.
First sound check was VERY promising, so I decided to spend a few more bucks on this low budget build and "purdy" it up a bit. I don't have much money in the hole here, as the JL has been in storage since college. I actually have a subwoofer boneyard. The ghost of cars past!
Another sound check confirmed I had what I wanted, so I buttoned it up and played on it for an hour tonight. This thing is great! It won't belt out any power on a stage, but it damn sure shakes the kitchen, and even my drop tunings don't sound muddy like they do on my loaner combo, and I don't have to turn down the 30 Hz slider on my Hartke! Low, punchy, articulated bass with a bright mid response.
Efficiency of the JL is a cruddy 88 dB, and the sealed box doesn't do much to augment that limited volume. At 125 RMS, this is a practice speaker only, but it's also a proof of concept for myself - plus it was a free sub, and I'm a cheap bastard. :D
Here's the calculated response curve, with the lows that rattle the cabinets and the tightness that keeps even an open E string well articulated without attenuation on the EQ:
Next time I build, I'll want something that can power a bar or small club performance. I'll either go with a Fearful 12/6 or possibly another car sub bastardization just because I have more of them sitting around gathering dust. I think one of them has a sensitivity of 92 SPL and program handling of 350W, which aint too far behind the Eminence specs.
DIY at it's best. Make do, figger it out.
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