If you measured with an SPL meter, you have to take crest factor into account there, since an SPL meter isn't peak reading even in the "fast" (100 ms) mode. This causes no end of confusion.Problem with this calculator is it doesn't factor in the crest factor of recordings. This calculator tells me I would have 102.8db at my listening position with a 50W amp I used to own and 85db efficient speakers, but it got nowhere near that when the volume was maxed (measured this with a Radioshack SPL meter).