Mark the linear-phase LR24 crossover experimental

The low frequency performance is too poor at this filter size and the
DSP load impact is too high. This needs to be implemented using FFT
convolution instead.

plugins/crossover/src/crossover/fir.rs

@@ -22,10 +22,10 @@ use std::simd::{f32x2, StdFloat};
 use crate::biquad::{Biquad, BiquadCoefficients, NEUTRAL_Q};
 use crate::NUM_BANDS;
 
-// TODO: These filters would be more efficient when processing four samples at a time instead of
-//       processing two channels at a time. But this keeps the interface nicer.
+// TODO: Move this to FFT convolution so we can increase the filter size and improve low latency performance
 
-/// The size of the FIR filter window, or the number of taps.
+/// The size of the FIR filter window, or the number of taps. The low frequency performance is
+/// greatly limited by this.
 const FILTER_SIZE: usize = 121;
 /// The size of the FIR filter's ring buffer. This is `FILTER_SIZE` rounded up to the next power of
 /// two.

plugins/crossover/src/lib.rs

@@ -81,7 +81,7 @@ enum CrossoverType {
     #[name = "LR24"]
     LinkwitzRiley24,
     #[id = "lr24-lp"]
-    #[name = "LR24 (LP)"]
+    #[name = "LR24 (LP, experimental)"]
     LinkwitzRiley24LinearPhase,
 }