1995 Honda Civic Knocking/Thumping while brakeing

I just had my brake pads, brake lines, and master cylinder replaced by a mechanic after my brakes had failed on me. They work fine but now there is this loud knocking noise that occurs when I brake softly under 25mph. If I brake hard the noise goes away or if I brake over 25mph it doesn't make the knocking noise. The noise gets louder but slower as I get closer to stopping and seems to be coming from the front right wheel. Need some suggestions please, the noise is really audible and rather embarrassing when I have passengers.