My subs aren't hitting as hard as they should?

I have a 97 Honda accord and i recently built a tuned 30hz box for my two 12s there different brand of subs one is a infinity reference series and the other is a cheap sub from Walmart but i had them in individual sealed boxes and they hit way harder then there hitting now? What's the problem i sanded the metal for ground all the wires are hooked up correctly i just don't see why there not hitting as hard? Could it be the head unit? Its a jvc i fid have a kenwood When i had them in sealed boxes please help?!

Always start with the big 3, upgrade the battery, headunit and amp. I wouldn't run any wire smaller than 4 gauge from the battery to the amp. Try wiring the subs in parallel inside the box.My subs aren t hitting as hard as they should - 1

A stereo can never sound any better than its worst speaker. The way they're wired together is also a factor. The wrong impedance can affect t the performance or even damage the amp. Make sure the material used for the cabinet doesn't flex or rattle and really IS correct volume and has the right dimensions for its port. Poorly designed cabinets can allow standing waves to partially cancel sound. Speakers out of phase with each other can reduce performance. If I knew your design I could make a better judgment, besides check all your work again.