they did from me.
i had him design me a box for flat response with my xxx 18, and it actually sounded pretty decent, but it was really big. i never worked out the exact specs but it was about 8 cubes after sub displacement. that 18 tore one tinsel lead on each side and i had to repair them before selling the sub.
i switched out to a dd 9518g, and had him design me another box, this one just to get piss loud to the ear. again, it was huge, more like 9-10 cubes after sub. it got pretty loud... but i burned up the tinsels inside the spiders, reconed it, and did it again... first time it lasted about 3 months, second time about 6. i emailed DD about it, and they said if i was doing that and not burning up coils that it was just moving too much from too large a box.
i still need to build a box for my hdc3 18s, but i'm going right in the middle of what dj recommends, at 5.5 cubes per sub and 38 hz.
can anyone recommend me another person to do the design for me?