feat: configurable band count and frequency range for legacy graphic EQ

- Add Bands/Min Hz/Max Hz controls to legacy EQ section
- Dynamic frequency generation with log spacing and auto-scaling Q
- Import/export handles variable band counts, Q optional for shelves
- Custom presets interpolate across different band counts
- Update legacy EQ tutorial for new controls

index.html

@@ -4174,6 +4174,54 @@
                                             ×
                                         </button>
 
+                                        <div
+                                            class="eq-howto-tab legacy"
+                                            id="eq-howto-legacy"
+                                            style="display: none"
+                                        >
+                                            <h4>Legacy EQ - Graphic Equalizer</h4>
+                                            <ol>
+                                                <li>
+                                                    Set the <b>number of bands</b> (3-32) and
+                                                    <b>frequency range</b> (Min/Max Hz) at the top to
+                                                    customize the equalizer layout.
+                                                </li>
+                                                <li>
+                                                    <b>Drag the sliders</b> to boost or cut each frequency
+                                                    band. Bands are spaced logarithmically across your range.
+                                                </li>
+                                                <li>
+                                                    Pick a <b>preset</b> (Bass Boost, Rock, Vocal, etc.) as a
+                                                    starting point - presets auto-scale to your band count.
+                                                </li>
+                                                <li>
+                                                    Adjust the <b>preamp</b> slider to raise or lower the overall
+                                                    level - reduce it if you hear distortion from large boosts.
+                                                </li>
+                                                <li>
+                                                    <b>Save</b> your own custom presets with a name so you can
+                                                    recall them later.
+                                                </li>
+                                                <li>
+                                                    <b>Export</b> saves the EQ in EqualizerAPO text format.
+                                                    <b>Export APO</b> saves a GraphicEQ config line you can paste
+                                                    directly into Equalizer APO's config.txt.
+                                                </li>
+                                                <li>
+                                                    <b>Import</b> loads EQ settings from EqualizerAPO text files
+                                                    or simple frequency/gain CSV files - points are mapped to
+                                                    your current bands automatically.
+                                                </li>
+                                                <li>
+                                                    Click <b>Reset</b> to flatten all bands back to 0 dB.
+                                                </li>
+                                            </ol>
+                                            <p class="eq-howto-tip">
+                                                Tip: Cut problem frequencies rather than boosting others - it
+                                                sounds cleaner and avoids clipping.
+                                            </p>
+                                        </div>
+
                                         <div class="eq-howto-tab autoeq" id="eq-howto-autoeq">
                                             <h4>AutoEQ - Headphone Correction</h4>
                                             <ol>
@@ -4297,6 +4345,35 @@
 
                                     <!-- Legacy 16-Band Graphic EQ (visible in legacy mode) -->
                                     <div class="graphic-eq-section" id="graphic-eq-section" style="display: none">
+                                        <div class="graphic-eq-config-row">
+                                            <label>Bands</label>
+                                            <input
+                                                type="number"
+                                                id="legacy-geq-band-count"
+                                                min="3"
+                                                max="32"
+                                                value="16"
+                                                class="geq-config-input"
+                                            />
+                                            <label>Min Hz</label>
+                                            <input
+                                                type="number"
+                                                id="legacy-geq-freq-min"
+                                                min="10"
+                                                max="96000"
+                                                value="25"
+                                                class="geq-config-input"
+                                            />
+                                            <label>Max Hz</label>
+                                            <input
+                                                type="number"
+                                                id="legacy-geq-freq-max"
+                                                min="10"
+                                                max="96000"
+                                                value="20000"
+                                                class="geq-config-input"
+                                            />
+                                        </div>
                                         <div class="graphic-eq-preset-row">
                                             <label for="legacy-graphic-eq-preset-select" class="graphic-eq-preset-label"
                                                 >Preset</label

js/audio-context.js

@@ -148,13 +148,15 @@ class AudioContextManager {
         // Callbacks for audio graph changes (for visualizers like Butterchurn)
         this._graphChangeCallbacks = [];
 
-        // --- Graphic EQ (16-band, separate chain) ---
+        // --- Graphic EQ (configurable bands, separate chain) ---
         this.geqFilters = [];
         this.geqPreampNode = null;
         this.geqOutputNode = null;
         this.isGraphicEQEnabled = equalizerSettings.isGraphicEqEnabled();
-        this.geqFrequencies = [25, 40, 63, 100, 160, 250, 400, 630, 1000, 1600, 2500, 4000, 6300, 10000, 16000, 20000];
+        this.geqBandCount = equalizerSettings.getGraphicEqBandCount();
-        this.geqGains = equalizerSettings.getGraphicEqGains();
+        this.geqFreqRange = equalizerSettings.getGraphicEqFreqRange();
+        this.geqFrequencies = generateFrequencies(this.geqBandCount, this.geqFreqRange.min, this.geqFreqRange.max);
+        this.geqGains = equalizerSettings.getGraphicEqGains(this.geqBandCount);
         this.geqPreamp = equalizerSettings.getGraphicEqPreamp();
 
         // Load saved settings
@@ -1090,11 +1092,12 @@ class AudioContextManager {
         this.geqOutputNode = this.audioContext.createGain();
         this.geqOutputNode.gain.value = 1;
 
+        const geqQ = 2.5 * Math.sqrt(16 / this.geqBandCount);
         this.geqFilters = this.geqFrequencies.map((freq, i) => {
             const filter = this.audioContext.createBiquadFilter();
             filter.type = 'peaking';
             filter.frequency.value = freq;
-            filter.Q.value = 2.5; // constant Q for 16-band
+            filter.Q.value = geqQ;
             filter.gain.value = this.geqGains[i] || 0;
             return filter;
         });
@@ -1136,7 +1139,7 @@ class AudioContextManager {
     }
 
     setGraphicEqBandGain(bandIndex, gainDb) {
-        if (bandIndex < 0 || bandIndex >= 16) return;
+        if (bandIndex < 0 || bandIndex >= this.geqBandCount) return;
         this.geqGains[bandIndex] = Math.max(-30, Math.min(30, gainDb));
         if (this.geqFilters[bandIndex] && this.audioContext) {
             const now = this.audioContext.currentTime;
@@ -1149,7 +1152,7 @@ class AudioContextManager {
         if (!Array.isArray(gains)) return;
         const now = this.audioContext?.currentTime || 0;
         gains.forEach((g, i) => {
-            if (i >= 16) return;
+            if (i >= this.geqBandCount) return;
             this.geqGains[i] = Math.max(-30, Math.min(30, g));
             if (this.geqFilters[i]) {
                 this.geqFilters[i].gain.setTargetAtTime(this.geqGains[i], now, 0.01);
@@ -1158,6 +1161,51 @@ class AudioContextManager {
         equalizerSettings.setGraphicEqGains([...this.geqGains]);
     }
 
+    setGraphicEqBandCount(count) {
+        const newCount = Math.max(3, Math.min(32, parseInt(count, 10) || 16));
+        if (newCount === this.geqBandCount) return;
+
+        const oldGains = this.geqGains;
+        this.geqBandCount = newCount;
+        this.geqFrequencies = generateFrequencies(newCount, this.geqFreqRange.min, this.geqFreqRange.max);
+        this.geqGains = equalizerSettings._interpolateGains(oldGains, newCount);
+
+        equalizerSettings.setGraphicEqBandCount(newCount);
+        equalizerSettings.setGraphicEqGains(this.geqGains);
+
+        if (this.isInitialized && this.audioContext) {
+            this._destroyGraphicEQ();
+            this._createGraphicEQ();
+            this._connectGraph();
+        }
+    }
+
+    setGraphicEqFreqRange(minFreq, maxFreq) {
+        const newMin = Math.max(10, Math.min(96000, parseInt(minFreq, 10) || 25));
+        const newMax = Math.max(10, Math.min(96000, parseInt(maxFreq, 10) || 20000));
+        if (newMin >= newMax) return;
+        if (newMin === this.geqFreqRange.min && newMax === this.geqFreqRange.max) return;
+
+        this.geqFreqRange = { min: newMin, max: newMax };
+        this.geqFrequencies = generateFrequencies(this.geqBandCount, newMin, newMax);
+
+        equalizerSettings.setGraphicEqFreqRange(newMin, newMax);
+
+        if (this.isInitialized && this.audioContext) {
+            this._destroyGraphicEQ();
+            this._createGraphicEQ();
+            this._connectGraph();
+        }
+    }
+
+    getGraphicEqFrequencies() {
+        return this.geqFrequencies;
+    }
+
+    getGraphicEqBandCount() {
+        return this.geqBandCount;
+    }
+
     setGraphicEqPreamp(db) {
         this.geqPreamp = Math.max(-20, Math.min(20, parseFloat(db) || 0));
         if (this.geqPreampNode && this.audioContext) {

js/settings.js

@@ -1236,26 +1236,29 @@ export async function initializeSettings(scrobbler, player, api, ui) {
     }
 
     // ========================================
-    // 16-Band Graphic Equalizer (Legacy EQ mode)
+    // Graphic Equalizer (Legacy EQ mode) - Configurable Bands
     // ========================================
-    const GEQ_LABELS = [
+    let geqBandCount = equalizerSettings.getGraphicEqBandCount();
-        '25',
+    let geqFreqRange = equalizerSettings.getGraphicEqFreqRange();
-        '40',
+
-        '63',
+    const formatGeqFreq = (freq) => {
-        '100',
+        if (freq >= 10000) return (freq / 1000).toFixed(0) + 'K';
-        '160',
+        if (freq >= 1000) return (freq / 1000).toFixed(freq % 1000 === 0 ? 0 : 1) + 'K';
-        '250',
+        return freq.toString();
-        '400',
+    };
-        '630',
+
-        '1K',
+    const generateGeqFrequencies = (count, min, max) => {
-        '1.6K',
+        const freqs = [];
-        '2.5K',
+        for (let i = 0; i < count; i++) {
-        '4K',
+            const t = i / (count - 1);
-        '6.3K',
+            freqs.push(Math.round(min * Math.pow(max / min, t)));
-        '10K',
+        }
-        '16K',
+        return freqs;
-        '20K',
+    };
-    ];
+
+    let GEQ_FREQUENCIES = generateGeqFrequencies(geqBandCount, geqFreqRange.min, geqFreqRange.max);
+    let GEQ_LABELS = GEQ_FREQUENCIES.map(formatGeqFreq);
+
     const geqBandsContainer = document.getElementById('graphic-eq-bands');
     const geqPreampSlider = document.getElementById('graphic-eq-preamp-slider');
     const geqPreampValue = document.getElementById('graphic-eq-preamp-value');
@@ -1268,11 +1271,15 @@ export async function initializeSettings(scrobbler, player, api, ui) {
     const legacyGeqPresetSelect = document.getElementById('legacy-graphic-eq-preset-select');
     const legacyGeqResetBtn = document.getElementById('legacy-graphic-eq-reset-btn');
 
+    const geqBandCountInput = document.getElementById('legacy-geq-band-count');
+    const geqFreqMinInput = document.getElementById('legacy-geq-freq-min');
+    const geqFreqMaxInput = document.getElementById('legacy-geq-freq-max');
+
     const geqPreampSliders = [geqPreampSlider, legacyGeqPreampSlider].filter(Boolean);
     const geqPreampValues = [geqPreampValue, legacyGeqPreampValue].filter(Boolean);
     const geqPresetSelects = [geqPresetSelect, legacyGeqPresetSelect].filter(Boolean);
 
-    let geqGains = equalizerSettings.getGraphicEqGains() || new Array(16).fill(0);
+    let geqGains = equalizerSettings.getGraphicEqGains(geqBandCount) || new Array(geqBandCount).fill(0);
     let geqPreamp = equalizerSettings.getGraphicEqPreamp() || 0;
     const geqRange = equalizerSettings.getRange();
 
@@ -1288,7 +1295,7 @@ export async function initializeSettings(scrobbler, player, api, ui) {
         });
     };
 
-    // Build 16 vertical slider bands into a container
+    // Build vertical slider bands into a container
     const buildGeqBands = (container, idPrefix) => {
         if (!container) return;
         container.innerHTML = '';
@@ -1359,7 +1366,7 @@ export async function initializeSettings(scrobbler, player, api, ui) {
         select.addEventListener('change', () => {
             const key = select.value;
             if (!key) return;
-            const presets = getPresetsForBandCount(16);
+            const presets = getPresetsForBandCount(geqBandCount);
             const preset = presets[key];
             if (!preset) return;
             geqGains = [...preset.gains];
@@ -1375,7 +1382,7 @@ export async function initializeSettings(scrobbler, player, api, ui) {
     // Wire up reset buttons
     [geqResetBtn, legacyGeqResetBtn].filter(Boolean).forEach((btn) => {
         btn.addEventListener('click', () => {
-            geqGains = new Array(16).fill(0);
+            geqGains = new Array(geqBandCount).fill(0);
             equalizerSettings.setGraphicEqGains(geqGains);
             audioContextManager.setGraphicEqAllGains(geqGains);
             geqSyncAllSliders();
@@ -1383,6 +1390,49 @@ export async function initializeSettings(scrobbler, player, api, ui) {
         });
     });
 
+    // Band count and frequency range controls
+    const rebuildGeq = () => {
+        GEQ_FREQUENCIES = generateGeqFrequencies(geqBandCount, geqFreqRange.min, geqFreqRange.max);
+        GEQ_LABELS = GEQ_FREQUENCIES.map(formatGeqFreq);
+        buildGeqBands(geqBandsContainer, 'geq');
+        buildGeqBands(legacyGeqBandsContainer, 'legacy-geq');
+        geqSyncAllSliders();
+    };
+
+    if (geqBandCountInput) {
+        geqBandCountInput.value = geqBandCount;
+        geqBandCountInput.addEventListener('change', () => {
+            const newCount = Math.max(3, Math.min(32, parseInt(geqBandCountInput.value, 10) || 16));
+            geqBandCountInput.value = newCount;
+            if (newCount === geqBandCount) return;
+            geqGains = equalizerSettings._interpolateGains(geqGains, newCount);
+            geqBandCount = newCount;
+            audioContextManager.setGraphicEqBandCount(newCount);
+            rebuildGeq();
+            geqPresetSelects.forEach((s) => (s.value = ''));
+        });
+    }
+
+    if (geqFreqMinInput && geqFreqMaxInput) {
+        geqFreqMinInput.value = geqFreqRange.min;
+        geqFreqMaxInput.value = geqFreqRange.max;
+
+        const handleFreqRangeChange = () => {
+            const newMin = Math.max(10, Math.min(96000, parseInt(geqFreqMinInput.value, 10) || 25));
+            const newMax = Math.max(10, Math.min(96000, parseInt(geqFreqMaxInput.value, 10) || 20000));
+            geqFreqMinInput.value = newMin;
+            geqFreqMaxInput.value = newMax;
+            if (newMin >= newMax) return;
+            if (newMin === geqFreqRange.min && newMax === geqFreqRange.max) return;
+            geqFreqRange = { min: newMin, max: newMax };
+            audioContextManager.setGraphicEqFreqRange(newMin, newMax);
+            rebuildGeq();
+        };
+
+        geqFreqMinInput.addEventListener('change', handleFreqRangeChange);
+        geqFreqMaxInput.addEventListener('change', handleFreqRangeChange);
+    }
+
     // Legacy EQ Import / Export
     const parseGeqLabelFrequency = (label) => {
         const normalized = String(label).trim().toLowerCase().replace(/\s+/g, '');
@@ -1395,7 +1445,6 @@ export async function initializeSettings(scrobbler, player, api, ui) {
         }
         return Number.parseFloat(withoutHz);
     };
-    const GEQ_FREQUENCIES = GEQ_LABELS.map((label) => parseGeqLabelFrequency(label));
     const legacyGeqExportBtn = document.getElementById('legacy-geq-export-btn');
     const legacyGeqExportCsvBtn = document.getElementById('legacy-geq-export-csv-btn');
     const legacyGeqImportBtn = document.getElementById('legacy-geq-import-btn');
@@ -1405,7 +1454,8 @@ export async function initializeSettings(scrobbler, player, api, ui) {
         legacyGeqExportBtn.addEventListener('click', () => {
             const lines = [`Preamp: ${geqPreamp.toFixed(1)} dB`];
             GEQ_FREQUENCIES.forEach((freq, i) => {
-                lines.push(`Filter ${i + 1}: ON PK Fc ${freq} Hz Gain ${geqGains[i].toFixed(1)} dB Q 1.41`);
+                const q = (2.5 * Math.sqrt(16 / geqBandCount)).toFixed(2);
+                lines.push(`Filter ${i + 1}: ON PK Fc ${freq} Hz Gain ${geqGains[i].toFixed(1)} dB Q ${q}`);
             });
             const blob = new Blob([lines.join('\n')], { type: 'text/plain' });
             const url = URL.createObjectURL(blob);
@@ -1484,7 +1534,7 @@ export async function initializeSettings(scrobbler, player, api, ui) {
                     // Sort by frequency
                     validPoints.sort((a, b) => a.freq - b.freq);
 
-                    // Map imported points to the 16 GEQ bands using nearest-frequency matching
+                    // Map imported points to the GEQ bands using nearest-frequency matching
                     const newGains = GEQ_FREQUENCIES.map((targetFreq) => {
                         // Find the closest imported point by log-frequency distance
                         let closest = validPoints[0];
@@ -1608,11 +1658,14 @@ export async function initializeSettings(scrobbler, player, api, ui) {
             const customPresets = getLegacyGeqCustomPresets();
             if (customPresets[key]) {
                 const gains = customPresets[key]?.gains;
-                if (!Array.isArray(gains) || gains.length !== GEQ_FREQUENCIES.length) {
+                if (!Array.isArray(gains) || gains.length === 0) {
                     updateDeleteBtnVisibility();
                     return;
                 }
-                geqGains = gains.map((g) => {
+                const adjusted = gains.length !== geqBandCount
+                    ? equalizerSettings._interpolateGains(gains, geqBandCount)
+                    : gains;
+                geqGains = adjusted.map((g) => {
                     const n = Number(g);
                     return Number.isFinite(n)
                         ? Math.max(parseFloat(geqRange.min), Math.min(parseFloat(geqRange.max), n))
@@ -3812,6 +3865,7 @@ export async function initializeSettings(scrobbler, player, api, ui) {
         const hp = document.getElementById('eq-howto-panel');
         if (hp && hp.style.display !== 'none') {
             const tabs = {
+                legacy: document.getElementById('eq-howto-legacy'),
                 autoeq: document.getElementById('eq-howto-autoeq'),
                 parametric: document.getElementById('eq-howto-parametric'),
                 speaker: document.getElementById('eq-howto-speaker'),
@@ -3834,6 +3888,7 @@ export async function initializeSettings(scrobbler, player, api, ui) {
     const howtoPanel = document.getElementById('eq-howto-panel');
     const howtoClose = document.getElementById('eq-howto-close');
     const howtoTabs = {
+        legacy: document.getElementById('eq-howto-legacy'),
         autoeq: document.getElementById('eq-howto-autoeq'),
         parametric: document.getElementById('eq-howto-parametric'),
         speaker: document.getElementById('eq-howto-speaker'),

js/storage.js

@@ -1700,10 +1700,12 @@ export const equalizerSettings = {
         localStorage.removeItem(this.AUTOEQ_LAST_HEADPHONE_KEY);
     },
 
-    // --- Graphic EQ (16-band) separate storage ---
+    // --- Graphic EQ separate storage ---
     GEQ_ENABLED_KEY: 'graphic-eq-enabled',
     GEQ_GAINS_KEY: 'graphic-eq-gains',
     GEQ_PREAMP_KEY: 'graphic-eq-preamp',
+    GEQ_BAND_COUNT_KEY: 'graphic-eq-band-count',
+    GEQ_FREQ_RANGE_KEY: 'graphic-eq-freq-range',
 
     isGraphicEqEnabled() {
         try {
@@ -1721,19 +1723,59 @@ export const equalizerSettings = {
         }
     },
 
-    getGraphicEqGains() {
+    getGraphicEqBandCount() {
+        try {
+            const val = localStorage.getItem(this.GEQ_BAND_COUNT_KEY);
+            if (val !== null) {
+                const num = parseInt(val, 10);
+                if (num >= 3 && num <= 32) return num;
+            }
+        } catch { /* ignore */ }
+        return 16;
+    },
+
+    setGraphicEqBandCount(count) {
+        try {
+            localStorage.setItem(this.GEQ_BAND_COUNT_KEY, String(count));
+        } catch { /* ignore */ }
+    },
+
+    getGraphicEqFreqRange() {
+        try {
+            const stored = localStorage.getItem(this.GEQ_FREQ_RANGE_KEY);
+            if (stored) {
+                const parsed = JSON.parse(stored);
+                if (parsed && Number.isFinite(parsed.min) && Number.isFinite(parsed.max)) {
+                    return parsed;
+                }
+            }
+        } catch { /* ignore */ }
+        return { min: 25, max: 20000 };
+    },
+
+    setGraphicEqFreqRange(min, max) {
+        try {
+            localStorage.setItem(this.GEQ_FREQ_RANGE_KEY, JSON.stringify({ min, max }));
+        } catch { /* ignore */ }
+    },
+
+    getGraphicEqGains(bandCount) {
         try {
             const stored = localStorage.getItem(this.GEQ_GAINS_KEY);
             if (stored) {
                 const parsed = JSON.parse(stored);
-                if (Array.isArray(parsed) && parsed.length === 16) {
+                const expectedCount = bandCount || this.getGraphicEqBandCount();
+                if (Array.isArray(parsed) && parsed.length === expectedCount) {
                     return parsed.map((v) => (Number.isFinite(v) ? v : 0));
                 }
+                if (Array.isArray(parsed) && parsed.length > 0) {
+                    return this._interpolateGains(parsed, expectedCount);
+                }
             }
         } catch {
             /* ignore */
         }
-        return new Array(16).fill(0);
+        return new Array(bandCount || this.getGraphicEqBandCount()).fill(0);
     },
 
     setGraphicEqGains(gains) {

styles.css

@@ -7902,6 +7902,29 @@ body:has(#side-panel.active) #close-fullscreen-cover-btn {
     gap: var(--spacing-md);
 }
 
+.graphic-eq-config-row {
+    display: flex;
+    align-items: center;
+    gap: var(--spacing-sm);
+    flex-wrap: wrap;
+}
+
+.graphic-eq-config-row label {
+    font-size: 0.8rem;
+    font-weight: 600;
+    color: var(--foreground);
+}
+
+.geq-config-input {
+    width: 70px;
+    padding: 4px 6px;
+    border: 1px solid var(--border-color, #444);
+    border-radius: 4px;
+    background: var(--bg-secondary, #222);
+    color: inherit;
+    font-size: 0.85rem;
+}
+
 .graphic-eq-preset-row {
     display: flex;
     align-items: center;