If by "spliced them together" you mean that the red wire from one sub is electrically connected to the red wire from the other sub, and the yellow wire from one sub is electrically connected to the yellow wire from the other sub, that would be wrong.
That would result in both subs reproducing an identical monophonic signal representing the low frequency content of the sum of the two channels, rather than the left sub reproducing the low frequency content of the left channel signal, and the right sub reproducing the low frequency content of the right channel signal. So you wouldn’t be gaining most of the advantage of having two subs.
But if you just mean that they are physically bundled together, and none of the wires are electrically connected to each other, that would be ok. Or, alternatively, you could electrically connect left sub red to left sub yellow, and connect that combination to the amp’s left channel +, while connecting right sub red to right sub yellow, and connecting that combination to the amp’s right channel +. With the RCA plugs that are connected to the black wires plugged in as I described in my previous post.
Best regards,
-- Al
