Til bass opp til Schroeder eller litt mer burde det holde med lavere samplingfrekvens vel? Kan man sette 24 eller 12 khz i AL? Og få dobbel eller firedobbel oppløsning?
Blir vel kanskje andre problemer..
FIR filter må alltid dekke hele frekvensområdet som skal avspilles ref
Nyquist–Shannon sampling theorem dvs 2x høyeste frekvens som skal gjengis.
Et lite Copilot svar
Copilot
Yes — you
can design an FIR filter with
fewer taps if you want to adjust only the
20–400 Hz range, even though the full audio bandwidth is
20 Hz–20 kHz.
BUT there are important trade‑offs.
Let me break it down clearly.
Short Answer
Yes, you can use fewer taps, but:
- The fewer the taps → the worse the filter’s frequency resolution, especially at low frequencies.
- Low frequencies (20–400 Hz) require longer FIR filters to create sharp or smooth transitions.
- If you only need a gentle shaping (EQ curve) → few taps are OK.
- If you need a sharp crossover or notch filter in bass → many taps are required.
Why Bass Requires More Taps
An FIR filter’s minimum number of taps is determined by:
Frequency resolution
Δf≈fsN\Delta f \approx \frac{f_s}{N}Δf≈Nfs
Where:
- fsf_sfs = sample rate
- NNN = filter taps
Example at 48 kHz sample rate:
| FIR Taps | Frequency Resolution |
|---|
| 64 taps | 750 Hz → too coarse for bass! |
| 256 taps | 187 Hz |
| 512 taps | 94 Hz |
| 2048 taps | 23 Hz → great for bass shaping |
So to manipulate only
20–400 Hz precisely, especially if you want a clean band‑limited adjustment, you typically need:
500–2000 taps
(depending on how sharp you want the filter)
But what if you only want gentle bass EQ?
Example:
+3 dB shelf around 80 Hz
or
A smooth boost at 100 Hz
Then
you can use as few as 128–256 taps.
Because gentle EQ doesn’t require sharp transitions.
What if you want a sharp filter at 400 Hz?
A sharp cutoff (e.g., subwoofer crossover at 120 Hz, or isolating 20–400 Hz band) requires:
1500–3000 taps
(typical in room‑correction DSP or linear‑phase crossovers)
Reason:
Bass wavelengths are long → FIR needs many samples to model them.
So the answer becomes:
YES — fewer taps can be used
BUT only if the bass adjustment is smooth and broad
NO — if you need a precise or sharp adjustment in bass
Because FIR filters need long tap lengths to accurately shape low frequencies.
Want a rule‑of‑thumb?
For 48 kHz sample rate:
| Task | Recommended FIR taps |
|---|
| Gentle bass EQ (shelf / wide peak) | 100–300 taps  |
| Moderate band shaping (20–400 Hz) | 300–800 taps  |
| Sharp crossover or precise bass control | 1500–3000 taps  |
| Very high‑precision correction | 3000–8000 taps  |