Ported Box SIze question

You have enough space for a proper enclosure with one sub but you want to put in two.  Common sense says you use just one, and when you ask "is there any problem?" then of course the answer will be yes.  I hope you're plotting this out with a design program if you want to change any of the manufacturer's recommended box specs....but I guess if you were you wouldn't need to ask about it.

The problems could cover the range of:  poor frequency response either in loss of low end or a peak in the output, inefficiency, poor quality sound.....

When a program (like WinISD) gives you a large enclosure size for a vented application it is doing so only because it looks at "best quality output".  But a manufacturer recommendation of size is also considerate of everyday needs and actual room to put the enclosure.  That being said, if Kove said to use 2.7 ft for one sub then they are confident that the results will be dismal if you used a smaller box.

Port size in length will most likely grow considerably as the box net volume decreases, adding volume to your space that will infringe on the available sub space.  Consider using one sub instead of two and get a different amp if you need to.

Stevdart's response above is 100% correct.  But let me chime in with a simple reply since someone PM'd me and said my posts lately are over people's heads.

Probably won't damage anything but will sound like pure ass.