Well to summarize, before there were different specific issues I wanted to fix:
- lack of clarity around 80hz (compared to headset for ex)
- lack of deep low end (first octave)
- Sub in the center caused some right ear "fatigue" (There was really a strong difference between both ears)
- Sub localization (rattles/box resonance)
The new 15" helped with the low end, but in the same time it increased the rattles/resonances.
Here I just have to modify the box, with more bracing, and add some deadening in some places (rear firewall/floor).
It helped also on low end clarity, I guess because of its lower distortion.
The 12" had enough output, but not as clean.
Its new placement, moved to the right, also helped with ear fatigue.
So now I have to work on the sub/midbass xo.
My midbass' are I think too weak around 80hz. I'm not sure and I don't know how to measure or confirm this. The output is here, and the distortion plots are well below 5% there. But I still feel like they don't like to be pushed too low.
Crossed a bit higher they sound better, and I then also get the biggest impact from the sub.
But there's a limit or it becomes too much localizable.
For one week I had the sub on right, tuned with xo at 80hz/24db, same target.
Everything sounded cleaner, everything in front with sub almost not localizable (except for resonances/rattles).
But it was less fun, not the big big impact on drums I had at 120hz.
Yesterday I placed the sub to fire right behind driver seat.
Quickly tuned but will finish today. The seat seems to act as an high pass, would probably help for localization. Also it will be at the same distance for both ears, should help too.
The seat has a hard shell in the back, so I hope it won't be felt too much in my back (1" clearance).
Goal is to move up the xo to find the sweet spot impact/localization.
So I'll know more tonight.
If this doesn't work, I can:
- port the midbass. In theory this should lower excursion near 70/80hz so help a bit. Delay should not be an issue it's only few ms more on winisd.
- or doubling the midbass, 4x8" in 2.5 way, for a very clean output. This would need only minor modifications of my boxes.
- or going for 2x10"... but they won't fit in doors, will need a big job in kicks, I'm not sure I can do it.