I have actually abandoned this cab & design. The two cabs in the pic will soon be on their way to a new home. I had an opportunity to sell them cheap (which will reimburse me for ply and then some).
It is quite a spike around 75, I guess if I ran em, I'd cross the cab over around 70 anyway, so I wouldn't be to concerned about it.
HAha. I am fortunate to have a large workshop under my apartment. My wife doesn't mind the table saw and shaking floorboards occasionally,.... she would rather have that than me getting sh1t faced at the bar with the lads watching the game. The fact that I make a decent side income with the monstrous speakers I build helps too
I am happiest when I am building......
The only way to properly find out if something will work is to build and test, which you've done.
With my own designs, I usually reckon it takes at least three attempts to get it right. I've spent ages building massively complex cabs only to fire them up twice, once with an amp to find it doesn't work, the second time with some newspaper, kindling and a match!
I don't know if this is still relevant and up to date tho,
I wanted to say that I'm pretty sure the horn length is important when it comes to low frequency response!!
Generally the cone has to be long enough to hit the wanted lowest frequency! This depends on the relation and difference between the horn throat and the lip.
If possible the horn length should be quarter the wave length, and the cone has to be big enough to respond the wanted frequency ... this is sone by stacking horn loaded subs otherwise you would have to build a gigantic enclosure that wouldn't fit anywhere. So if the lip of the horn too small now, then it of course can't play these low notes, BUT this "unwanted leak" of frequency response from the resonator causes a quarter octav frequency ... basically a wave length four times as long as the horn-path ... that's what makes Transmissionline-Subwoofer work! So you get loudnes added, if you now contruct your horn-path so that you get that extra level added to the right frequency you can correct that leak! And because it's a quarter octav the way to do it is to build the horn-length 4 times shorter than the wave length you want you level to be added, so let's say I want my sub to be able to respond to 28Hz, I'd calculate the wave length (sound of speed devided by the frequency) 343m/s devided by 28Hz gives me 12,25m !! This is my length of the frequency so now devide it by 4 to get that quarter octav covered and you'll get 3,06m of horn length! That's how I do it... it's just physics! I suppose you already knew that but I wanted to be sure because I couldn't find it on here!
Sorry for my (non existent) english "skills" ... I hope you can understand it anyways :')