Best kind of digital EQ filter? 2013-11-07 16:06:58 An audio company that I have some influence over is designing a new digital audio player and programming the digital EQ section. Their engineer told me that they're implementing it as an FIR filter. They're planning to play back hi-res music files up to 192k/24b on a somewhat dated SoC. I see two potential problems:1. 192000Hz audio requires a LOT of taps in an FIR filter to get at the low frequencies. Frequency resolution is calculated as (Fs/N(taps)), so even a 2048 tap FIR filter can only get down to 100Hz or so. Not much of a bass boost filter, more like a midbass bloat effect.2. The company director was also complaining of "phase shift" with digital filters. Now as you may know, corrective EQ filters are best implemented as minimum phase filters to cancel out the phase shift introduced by the headphones themselves, but FIR filters tend to be implemented as linear phase. However linear phase looks better on paper and sounds better to... somebody?I suggested that they change the design to a minimum phase IIR filter, but the engineer said "isn't FIR supposed to be higher fidelity?" Where I have yet to get his word on what this "higher fidelity" entails.I searched and found this:http://www.dspguru.com/dsp/faqs/iir/basics1.4 What are the advantages of IIR filters (compared to FIR filters)? IIR filters can achieve a given filtering characteristic using less memory and calculations than a similar FIR filter.1.5 What are the disadvantages of IIR filters (compared to FIR filters)? They are more susceptable to problems of finite-length arithmetic, such as noise generated by calculations, and limit cycles. (This is a direct consequence of feedback: when the output isn't computed perfectly and is fed back, the imperfection can compound.) They are harder (slower) to implement using fixed-point arithmetic. They don't offer the computational advantages of FIR filters for multirate (decimation and interpolation) applications.Now, I suspect that neither of the first two disadvantages apply, since they told me they're implementing their existing filter using 64-bit arithmetic. That sounds like plenty enough accuracy, and 64-bit has got to be floating point, I guess?But what does the last point mean?And can someone offer me some examples of how much more noise / distortion an IIR filter would generate compared to an FIR filter given the same bit precision in calculations?