Originally Posted by Mpoes12
Just two thoughts based on my own opinions on this topic. I find it of value to avoid port tuning frequencies that are in the middle of areas that are "modally busy." By this I mean an area for which there are 2-3 modes or more in a particular 1/3 octave bin. This is because I have found that when the tuning is very close to any of the modes in that bin, you get greater excitation of that mode. I have found it better, where possible, to move the tuning of such speakers to below 40hz, as in the majority of small rooms, there would only be one or often even no modes in that region (with the exception of the lone axial mode typically in the 20-25hz range).
It would be my suggestion that you either move the tuning to below 40hz or you look at the room modes in your room and select the tuning so it is substantially away from the modes in that bin. My room is something like 23'x11'x8'. In the bin between 44hz and 55hz I have two modes at 48 and 50hz. In the next bin down I have no modes. That means if I tune to 40hz, the ports output is still nearly flat (within 1 db or so) of its output at 48hz. If I move the tuning down to 35hz, then the output is down about 3db's by 48hz. The point being, try to keep the port tuning substantially away from any modes, especially when there are multiple modes close together. It can exacerbate ringing in the room.
Second point is about the ports themselves. I think a single 4" port is going to audibly chuff in this setup. The model seems to suggest you will hit xmax with around 2-300 watts and at that point the single 4" port is going to have an air velocity that is in excess of 30m/s, you will have audible chuffing and significant port compression. Two 4" ports would be better and keep the air velocity below the point of audible problems. For a 2 cubic foot box, a port tuning of 45hz would require two 4" diameter ports that are about 13.75" long. If I were building these I would probably prefer a tune of around 35hz and that would require the ports to be 24" long (which may not be possible in your boxes).
Thanks for the suggestions.
I sure am getting lots of different port options! I'm surprised to see all the different variations lol.
I will be using a Crown XLS drive core 1002- 2 series in stereo mode, that's only 350W per channel @ 4oHm. With the paired 15" woofers wired in parallel, I'm thinking average 175W per woofer.
My thinking is using four woofers instead of one or two (same SPL) will lower max excursion per woofer, and with high passing them at about 40Hz,
I think Its safe from any port chuffing there?
Ill try a 4" D x 4.5L port like LTD02 suggests, before trying dual ports at 13.75"L or 24"L since its so much easier. If it sucks then Ill give the longer ports a go.
The cabs are each 31" tall, so I could make that happen, even with the 24"L for the lower tune.
Now I'm going down the "box mode" rabbit hole?