room-eq-wizard-mcp

An MCP server that connects LLMs to Room EQ Wizard (REW): typed control of REW's HTTP API plus local acoustic analysis that reduces measurement data to something a model can reason about.

REW is the DSP engine — sweeps, RT60, averaging, EQ optimization all run inside REW, and this server drives them through the API. What the server adds is the layer REW doesn't have: peak/null detection with Q factors and severity, per-band statistics, before/after comparison, room-mode prediction correlated against measurements, and log-decimated curves sized for an LLM context instead of megabytes of base64.

Requirements

• Node.js 20+
• REW 5.40+ running with its API server enabled:
  • macOS: open -a REW.app --args -api
  • Windows: roomeqwizard.exe -api
  • or enable it in REW Preferences → API
• API-triggered measurement (run_sweep) additionally requires a REW Pro upgrade; every read/analysis/EQ tool works without it.

Install

// Claude Desktop (claude_desktop_config.json) or any MCP client config
{
  "mcpServers": {
    "rew": {
      "command": "npx",
      "args": ["-y", "room-eq-wizard-mcp"]
    }
  }
}

# Claude Code
claude mcp add rew -- npx -y room-eq-wizard-mcp

The REW API address defaults to http://127.0.0.1:4735; override with the REW_API_URL environment variable if you run REW on another port.

Tools (46)

Area	Tools
Status	status, list_api_commands
Measurements	list_measurements, get_measurement, rename_measurement, delete_measurement, save_all_measurements, load_measurement_files, run_measurement_command, get_measurement_commands
Groups	list_groups, create_group, update_group, delete_group, add_measurements_to_group, get_group_measurements
Data	get_frequency_response, get_rt60, get_distortion
Measuring	run_sweep
Import	import_frequency_response, import_impulse_response, import_frequency_response_data, import_impulse_response_data, import_rta_file, import_sweep_recordings
Signal generator	generator
SPL meter	read_spl
EQ	auto_eq, get_eq_filters, set_eq_filters, get_predicted_response, list_equalisers
Processing	average_measurements, align_spl, arithmetic, smooth_measurement, add_spl_offset
Alignment	align_measurements, create_aligned_sum, get_alignment_state, configure_alignment, run_alignment_command
Analysis	analyze_response, compare_measurements, room_mode_analysis

Typical session: status → run_sweep (or load_measurement_files) → analyze_response → room_mode_analysis with your room dimensions → auto_eq → compare_measurements on the predicted result.

Architecture

src/rew/       the only layer that talks to REW
  codec.ts       base64 big-endian float32 <-> arrays (REW's wire format)
  types.ts       Zod schemas — raw JSON is parsed once at this boundary
  client.ts      HTTP client; enables REW blocking mode once for long commands
src/analysis/  pure functions, no I/O, no mocks needed to test
  spectrum.ts    median-baseline peak/null detection, band stats, decimation
  room-modes.ts  rectangular-room modes, Schroeder frequency, correlation
src/tools/     MCP tools as data: one ToolDef type, one registration loop

Two properties worth knowing:

• Everything REW computes stays REW's job. RT60, averaging, EQ matching are invoked via the API, never reimplemented — the numbers you get through this server match what the REW GUI shows.
• Long commands use REW's blocking mode, enabled once per session. A sweep or EQ match returns when it finishes (client timeout 180 s). Note the blocking setting persists in REW across restarts.

Development

pnpm install
pnpm test        # unit suite (mocked HTTP) + live suite that self-skips without REW
pnpm build
pnpm typecheck

With REW running (-api), the live integration tests in src/rew/live.integration.test.ts activate automatically.

Credits

Design informed by two earlier REW MCP servers: koltyj/REW-mcp (analysis depth, typed client patterns) and KevinMeinon/rew-mcp-server (API coverage philosophy and field-tested REW payload shapes, plus its excellent REW API reference doc). REW itself is © John Mulcahy.

License

MIT