Which 15 or 18 ınch woofer- best for open baffle

I think 1 kHz is quite high for a 15 incher... sound may bundle and get less detailed at top-end. The Pure audio project Neo woofer was used up till 950 Hz so it can do it. Perhaps you could still buy it separately if you ask Zeev nicely. But consider to add a mid(bass) driver...