10 litres is pretty good for most drivers that size, and some want smaller... why do you think you’ll really notice a huge difference in 6l vs 10l for example... I would build it big and make it smaller with blocks inside ���� In reality you won’t hear any difference if you heard them in a double blind... it will only effect your mind as to which sounds different...
sure if you put it in 1litre it will sound a bit boomy, but even then in a car it’s very hard to tell (I lived with some sb acoustics mfc17 in 0.8l test enclosures for 4-5 months and it wasn’t offensive... the Q of a driver/enclosure combination only effects the sound at or near resonance... the mid range doesn’t change very much (The speakers characteristics change that more than anything), so 90hz and up won’t be very different
the slight differences are likely down to how the calculators take losses/damping materials into account (or not as the case may be)
