ReaEQ Question: Hi/Lo Pass

The frequency stated for a High-Pass filter is the frequency where it is 3dB down, this is normal. If your HPF it's taking too much above (say) 100Hz when set at 100Hz (use your ears, not your eyes!) then move it down a smidging. If you want it steeper (changing bandwidth) and it sounds ok then go with it (starts looking like a chebechev filter). It's not what the graph tells you that matters (that's just there to give you a reference point and remind you what you are doing, it's how it sounds. Incidentally, the "Q" of a bandpass filter is the centre frequency divided by the bandwidth in Hz measured at the 3dB points. So a BPF at 1kHz with -3dB points 500Hz apart would have a Q of 2 and a bandwidth of about 0.7 octaves. Not sure how you measure it for a HPF. (The -3dB points would be at about 812Hz and 1312Hz, and remember the centre point is not the linear centre of the two frequencies, but the logarithmic centre ;) the bandpass curve only looks symmetrical on a logarithmic scale -i'll not go into the mathematics here as it's such a civilised forum and there might be minors present) 3dB is chosen because that's the half-power point (like in crossovers).