# LsPower Session Notes

## Current Goal

Build a Python tool to estimate electrical power delivered to a DIY active 2-way loudspeaker from measured DSP-output audio. Current measurement point is the analog DSP output / amplifier input, captured through a MOTU UltraLite input. Amplifier output is not measured directly yet; amplifier gain is modeled as an ideal scalar voltage gain in dB.

## Project Structure

- `soundcard_input.py`
  - Single runnable entry point.
  - Provides console voltage monitor, calibration routine, GUI monitor, and console power estimator mode.
- `lspower/audio.py`
  - Shared sounddevice helpers.
  - `SoundDeviceManager`
  - `QueuedInputStream`
  - channel parsing/formatting helpers.
- `lspower/impedance.py`
  - `ImpedanceCurve`
  - Loads REW impedance exports with columns: frequency Hz, impedance magnitude ohm, phase degrees.
  - Interpolates complex impedance to FFT bin frequencies.
- `lspower/power.py`
  - `VoltageSpectrumEstimator`
  - `PowerEstimator`
  - `WayConfig`
  - `PowerFrame`
  - shared Hann/Welch voltage spectrum scaling helper.
- `impedance.txt`
  - REW impedance export, currently usable directly.
- `BC 14NDL76.txt`
  - Thiele-Small parameters for B&C 14NDL76. Useful later for safety/excursion/thermal modeling, not required for current power calculation.
- `dsp_power_estimator.py`
  - Deleted as source. If an IDE tab still shows it, that is stale.

## Calibration State

The project uses a path-specific voltage scale:

```text
voltage = sounddevice_sample * volts_per_sample_unit
```

This is not a MOTU hardware full-scale spec. It includes the Windows/MME capture path, analog gain, routing, and any software gain.

Built-in reference:

```python
DEFAULT_INPUT_CALIBRATION_REFERENCE_RMS_V = 2.32
DEFAULT_INPUT_CALIBRATION_REFERENCE_RMS_SAMPLE = 0.021384357
DEFAULT_INPUT_VOLTS_PER_SAMPLE_UNIT ~= 108.490522
```

Later calibration files are saved under:

```text
calibrations/calibration_YYYYMMDD_HHMMSS.json
```

Startup behavior:

- If `--input-volts-per-sample-unit` is provided, it is used.
- Otherwise the newest calibration JSON is loaded.
- If no calibration file exists, the built-in default is used.

CLI calibration example:

```powershell
python soundcard_input.py --device 3 --channels 1 --calibrate-known-rms-v 2.32 --calibrate-only
```

GUI calibration saves the same JSON format.

## GUI Current Behavior

Start with:

```powershell
python soundcard_input.py --gui
```

Main sections:

- Input setup and calibration.
- Input-side metrics:
  - RMS voltage
  - Peak voltage
  - Crest factor
  - Crest dB
  - Digital peak
- Estimated amplifier output power:
  - LF/HF enable
  - channel
  - impedance file
  - amp gain dB
  - Vdsp
  - Vamp
  - P
  - Q
  - Sapp
- Input waveform plot:
  - calibrated voltage y-axis
  - manual Y limit field, blank means auto
- Input PSD plot:
  - Hann/Welch scaling
  - dB V^2/Hz
- Output power history plot:
  - P as solid line
  - Sapp as dashed line
  - moving window default 30 s, user-editable

Important GUI detail:

- If LF and HF are both used, include both channels in `Channels`, e.g. `1,2`.
- Power estimation uses the same FFT size, overlap, and smoothing controls as the input PSD.

## Power Estimation Math

For each way:

```text
V_amp(f,t) = G_amp * V_DSP(f,t)
G_amp = 10^(G_amp_dB / 20)
Z(f) = |Z(f)| * exp(j * phase_Z(f))
S_k(t) = |V_amp,k(t)|^2 / conj(Z_k)
P_k(t) = real(S_k)
Q_k(t) = imag(S_k)
S_app,k(t) = |V_amp,k(t)|^2 / |Z_k|
```

Totals:

```text
P_total = sum(P_k)
Q_total = sum(Q_k)
Sapp_total = sum(S_app,k)
```

FFT scaling:

- DC removed.
- Hann window.
- rFFT.
- Welch scaling to one-sided PSD in `V^2/Hz`.
- Multiply by `df` to get bin-integrated RMS voltage squared in `V^2`.

Synthetic validation already performed:

```text
1 Vrms sine into 8 ohm with 0 dB gain -> 0.125 W
```

## Current Known Hardware Context

- Audio interface: MOTU UltraLite.
- Working input path used so far:

```text
Device 3: Line In 3-4 (UltraLite-mk5) | MME | 2 in | 44100 Hz
```

- WASAPI device 67 previously captured silence for this setup.
- REW generator was used for calibration and signal testing.
- At one point, generator was running at 50 Hz, 1 Vrms.

## Commands

List devices:

```powershell
python soundcard_input.py --list-devices
```

GUI:

```powershell
python soundcard_input.py --gui
```

Console voltage monitor:

```powershell
python soundcard_input.py --device 3 --channels 1 --input-volts-per-sample-unit 108.490522
```

Console power estimator:

```powershell
python soundcard_input.py --device 3 --way LF:1:impedance.txt:34 --input-volts-per-sample-unit 108.490522
```

## Verification Commands

```powershell
.\.venv\Scripts\python.exe -m py_compile soundcard_input.py lspower\audio.py lspower\impedance.py lspower\power.py
```

Synthetic power scaling:

```powershell
.\.venv\Scripts\python.exe -c "import numpy as np; from pathlib import Path; from lspower.impedance import ImpedanceCurve; from lspower.power import PowerEstimator, WayConfig; fs=8192; n=8192; t=np.arange(n)/fs; x=np.sqrt(2)*np.sin(2*np.pi*1000*t); z=ImpedanceCurve(np.array([20.,20000.]), np.array([8.,8.]), np.array([0.,0.])); way=WayConfig('test',0,Path('none'),0.0); frame=PowerEstimator(way,z,fs,n,1.0,0.0).estimate(x); print(frame.rms_input_v, frame.total_p_w, frame.total_s_va)"
```

Expected output approximately:

```text
1.0 0.125 0.125
```

## Likely Next Steps

- Improve GUI visual polish further if needed.
- Add file picker buttons for impedance files.
- Add measured amplifier transfer function support `H_amp(f)`.
- Add driver safety panel:
  - compare P against `Pmax`
  - later estimate excursion against `Xmax`
- Use T/S parameters from `BC 14NDL76.txt` only for model-based safety/excursion extensions, not for current impedance-based power estimation.

