Speaker enclosure design for begginers

P Max, yes, continuous power of the driver, 400W or thereabouts for the 3015LF IIRC.

VRC - Yes, deduct the volume of the backside of the driver here. Some manufacturers provide this - I think Eminence are one that does so you should be able to get it from their product page. However it'll only be 3 or 4 litres for a neo 15, so won't make a vast difference when you've got 100 ish litres to play with. It makes much more difference for midhorns where the rear chamber is much smaller.

NOTE - you've entered LRC in mm where it should be cm (10x smaller) - that's why your schematic looks so odd. This will also fix the red text warning you asked about.

VTC - for a design like yours, that would only be the volume of the cavity represented by the loudspeaker cone itself - so something like 3-4 x SD would be enough as a rough estimate to get you started here. 

ATC - for your design, use SD assuming you would simply cut a circular hole in the baffle and have the whole driver fire straight into the horn.

S1, S2 etc, yes those are the areas of the horn as you move down its length. Note that what you've drawn is actually closer to an arrangement called "Offset Driver" in Hornresp - double click on the input field Nd to select this, or I think it can be found in one of the menus in the design wizard too. It's only when using this option (or a couple of others) that you need S2 to be at the middle of the driver - in a straight mid horn for example, S1 would be the area nearest the driver.

L1,L2 etc - you want these spaced relatively evenly down the length of the horn, taking care to set them at representative locations eg if you had a horn that flared out towards the end you'd want to make sure S4 was at the start of that last flare, where the change in expansion happens.

As to the type, you select whatever matches what you're trying to model. Par actually matches the mathematical relationship between length and width best, for the type of horn you're playing with.

I never mask the resonances as I prefer to see a worst case scenario - if you turn on the masking you get a smoother looking graph (which is sometimes closer to reality), but can leave you ignorant of issues that may need fixed. Again, like the driver volume/VRC thing, it makes a bit less difference on a bass horn than a mid though.

HTH,

David.

It's the mathematical relationship between the length of the horn and it's cross sectional area at any given point along its length.

Here's a quick illustration, but remember that in a horn with parallel walls such as your eg (and almost all bass horns) you're looking at having expansion in only one dimension instead of two, which is why the Par characteristic, even though it doesn't look like it's right, is actually the better fit.