FFT-based fast convolution vs IIR filtering

1. Is FFT faster than convolution?
2. Why is FFT faster than convolution?
3. Which has faster response IIR or FIR filters?
4. Is convolution of IIR filter possible?

Is FFT faster than convolution?

FFT convolution uses the overlap-add method together with the Fast Fourier Transform, allowing signals to be convolved by multiplying their frequency spectra. For filter kernels longer than about 64 points, FFT convolution is faster than standard convolution, while producing exactly the same result.

Why is FFT faster than convolution?

The convolution uses your O(n) per output sample. But because the FFT over 2n points coughs up 2n points, and n of those points are 'new', you only do the FFT 1/n as many times as you'd do the convolution.

Which has faster response IIR or FIR filters?

Therefore, an IIR filter can provide a significantly faster and more efficient filtering operation than an FIR filter. You can design FIR filters to provide a linear-phase response.

Is convolution of IIR filter possible?

Since the IIR filter would need infinite coefficients, the convolution operator cannot be used to implement it in reality; instead, you would need to implement it as a difference equation.