What level of accuracy is required when tuning a ported cabinet?
Or, asked another way, if my calculated volume is off by a few cubic inches, how much will that affect the tuning/sound of the sub cabinet?
I have modeled with WinISD pro. Small changes don't seem to affect the SPL curve dramatically. I just wanted to make sure because everything I've read talks about how much harder a vented box is to tune properly, so I didn't know if that was 'oops, I forgot to calculate the volume of my driver' or 'oops, I cut off an extra inch from my port tube' harder.
Makes sense - this is the story of my attempt to build my first subwoofer (my first DIY AV component of any sort, really) on a minimal budget, using parts that may never have been intended to match, and limited to the small form factor my wife will approve of.
Basically, I have a Eminence Lab-12 driver and a Klipsch Sub-12 plate amplifier, and no budget to get anything fancier. My current plan is a 20"x20"x20" cube made from .75" MDF, vented and tuned to 25 Hz. The cube, with a double thickness front face, has an internal volume of ~3.51 ft^3. My questions, in no particular order:
1. The Klipsch amp is a bit of an unknown. I don't know if it has a rumble filter / high pass filter, nor whether it has built-in bass boost anywhere. I also don't know whether I need to enclose the amp in its own box - the circuitry is exposed on the back, and I don't know how air-tight the seals are around the gain and low pass filter pots.
2. 3.5 ft. cubed is a bit bigger than the enclosure recommended on the eminence website. I figure, with bracing, amp, driver, and port subtracted, the volume will be "pretty close" to 3.2 feet, but I need to know how close it needs to be, especially for port-measuring purposes. This is where my earlier question comes in - how exact do I need to be before I get far inferior results?
3. Are there any major advantages/disadvantages to a slotted port vs. a round port?
Well, half of this discussion has just become a purely academic exercise for me, as the seller of the driver just sent a delivery intercept, so I'm back to the planning stages. Anyone have advice for a subwoofer driver that will behave well in a 3-3.5 foot enclosure? Budget is fairly low, since this is an experiment.