ive got myself a bass after playing my normal guitar for a while i wanted something new. On youtube there are tutorials about Slap Bass playing which i have been looking at. I can manage the E and A string but am struggling on the other two, i just cant get the right sound. Anyone know what im doing wrong?

cheers

Are using a compressor?

What sound are you getting?

Do you have enough action on the strings for slap? Light gauge and round wound give the best results – or so the slappers say. Newer strings work better as well.

its an acoustic bass not plugged into an amp, i'm getting a slap from A and E and a normal but slightly muted note from G and D

You normally slap down on the E and A stings and pull up on the D & G strings, as the thinner strings don't have the mass for the thumb slap.

Slap the E & A /D, pop on the D & G.
Light gague strings, roundwound, and lower them a bit.
Something like Ernie Ball Super Slinky's, or some Bass Boomers.
Personally, I loved the Slinky's, a nice bright funky sound.

I agree with the above posters. It is possible to get a slap sound but defo harder on the d and g strings. It's also easier to get a nice percussive twangy yet fat sound through an amp. Make sure your cuff is not touching/muting the strings.Keep up the practice – it will come. Good luck.