Frequency Ranges For Shelving Filters in L/M/H EQ?

Hi, I am interested in creating a simple EQ for low/mid/high, similar to what one might find on a DJ's mixing board. I've gone about creating this through 3 biquad/filtergraph combinations, one lowpass, one bandpass, one highpass. My frequencies for each respective filter are 200, 500, and 1500. However, comparing the signal that gets passed through these filters, even when all their gains are at 1, to the original signal, I found the filtered signal to be missing some frequencies, particularly in the low range. I was hoping someone would have recommendations for the frequency that each filter should be set at, or possibly a different approach to creating this kind of EQ.

Thanks!