Swing speed

I have just obtained a swing speed radar as I thought it would be interesting to see what my speed is and try to understand the shaft flex requirements. I had been using a TM R7 driver with a stiff shaft but had a fair amount of slice (which had improved massively in the last few months). I went to a local Direct Golf store to have my clubs checked and was measured on their machine as being around high80/low90 mark which would suggest a regular flex, so I purchased a new driver with regular flex and on the range have been getting far straighter shots so tat seems good. However when using the swing speed radar (which I know is probably not as accurate as the expensive trackman type machines) what sort of difference should I get between clubs? My driver I was anywhere between 94 and 105 (trying different swings) but with mid-irons I was around the 80 mark. Just wondered if this was normal and if there is any rough calculation I can use.