Klang+Ton Grand Diamond — 2-Way Monitor Loudspeakers
20-second read
The 22 cm problem: rising directivity from ≈2 kHz and breakup modes at higher frequencies, including the region around ≈7.5 kHz. Strategy adopted: attenuate the woofer before that zone rather than trying to EQ-correct a response whose directivity is already narrowing.
≈1.8 kHz crossover: the SIG225-4 progressively increases its directivity toward 2 kHz; the EC30-4 — 30 mm aluminum dome with vapor-deposited ceramic coating, Fs ≈700 Hz Dayton / 684 Hz K+T — presents characteristics compatible with the transition. PUBLISHED Dayton MEASURED K+T DESIGN INFERENCE
Faceted baffle: 25 mm, 22.5° lateral / 45° vertical. Shapes diffraction and contributes to a coherent directivity transition.
Directivity without a step: K+T notes the absence of the usual step found in many 2-way designs of this size; the most evident directivity concentration appears mainly above ≈8 kHz. PUBLISHED MEASUREMENT-GRAPH
Distortion and sensitivity: THD ≲1.5% at 95 dB even in the bass — reading of the K+T graph, not a global specification. 87 dB/2.83 V/1 m; 4 Ω nominal → ≈84 dB/W/m CALCULATED → 112 W in a point-source free-field model at 3 m for 95 dB, not a recommendation. Application reference: 20–30 W baseline, 50–100 W headroom. INFERENCE
0. Executive summary
20-second read
The 22 cm problem: rising directivity from ≈2 kHz and breakup modes at higher frequencies, including the region around ≈7.5 kHz. Strategy adopted: attenuate the woofer before that zone rather than trying to EQ-correct a response whose directivity is already narrowing.
≈1.8 kHz crossover: the SIG225-4 progressively increases its directivity toward 2 kHz; the EC30-4 — 30 mm aluminum dome with vapor-deposited ceramic coating, Fs ≈700 Hz Dayton / 684 Hz K+T — presents characteristics compatible with the transition. PUBLISHED Dayton MEASURED K+T DESIGN INFERENCE
Faceted baffle: 25 mm, 22.5° lateral / 45° vertical. Shapes diffraction and contributes to a coherent directivity transition.
Directivity without a step: K+T notes the absence of the usual step found in many 2-way designs of this size; the most evident directivity concentration appears mainly above ≈8 kHz. PUBLISHED MEASUREMENT-GRAPH
Distortion and sensitivity: THD ≲1.5% at 95 dB even in the bass — reading of the K+T graph, not a global specification. 87 dB/2.83 V/1 m; 4 Ω nominal → ≈84 dB/W/m CALCULATED → 112 W in a point-source free-field model at 3 m for 95 dB, not a recommendation. Application reference: 20–30 W baseline, 50–100 W headroom. INFERENCE
General design thesis
Remove the woofer from the problematic band at the right moment and make its directivity compatible with that of the tweeter in the transition zone. When these conditions are met, a relatively simple passive filter can produce an acoustic response notably more sophisticated than its electrical schematic, considered in isolation, might suggest.
1. Introduction — what the Grand Diamond is
The Grand Diamond is a 2-way project by Klang+Ton + Variant published in Klang+Ton 5/2026. The technical interest is not in exotic materials but in the coordination between transducers, crossover frequency, baffle geometry and off-axis behavior.
Strategy: SIG225-4 → low crossover → EC30-4 with low Fs → faceted baffle.
The baffle is part of the acoustic system that determines the final response.
| Parameter | Value | Evidence |
|---|---|---|
| Configuration | 2-way bass-reflex | PUBLISHED |
| Volume | ≈24–25 L | PUBLISHED |
| Woofer / Tweeter | SIG225-4 22 cm + EC30-4, 30 mm aluminum dome with vapor-deposited ceramic coating | PUBLISHED |
| Impedance / Sensitivity | 4 Ω nominal / 87 dB / 2.83 V / 1 m | PUBLISHED |
| Equivalent sensitivity | ≈84 dB/W/m | CALCULATED |
| Crossover | ≈1.8 kHz acoustic | PUBLISHED K+T |
| Filter / Port / Baffle | 2nd order / Ø50 mm × 12 cm, 20 cm alternative / 25 mm faceted 22.5°/45° | PUBLISHED |
General design thesis: Remove the woofer from the problematic band at the right moment and make its directivity compatible with that of the tweeter in the transition zone. When these conditions are met, a relatively simple passive filter can produce an acoustic response notably more sophisticated than its electrical schematic, considered in isolation, might suggest.
2. Transducers — SIG225-4 + EC30-4
Dayton SIG225-4
The SIG225-4 is a 22 cm woofer with black aluminum cone and cast aluminum chassis. The Dayton datasheet parameters and the measurements performed by K+T on their sample must be kept as separate datasets:
| Parameter | Dayton | K+T |
|---|---|---|
| Fs | 40 Hz | 40.8 Hz |
| Qts | 0.43 | 0.35 |
| Vas | 29.7 L | 26.4 L |
| Sensitivity | 91.4 dB | — |
The parameters measured by K+T are the most pertinent for interpreting the alignment of this sample. The differences relative to the Dayton datasheet are compatible with unit variation and/or measurement method.
Driver sensitivity vs. system sensitivity: The catalog sensitivity of the SIG225-4 alone (≈91.4 dB) is higher than that of the finished system (87 dB). The difference is compatible with the effect of baffle step, the acoustic integration of the system and the losses introduced by the passive filter; it should not be interpreted as a direct comparison of two sensitivities measured under identical conditions. PUBLISHED INFERENCE
Directivity and breakup: As it approaches ≈2 kHz, the SIG225-4 shows a progressive increase in directivity and, at higher frequencies, breakup modes become visible in its individual response, including the region around 7.5 kHz. The design prevents this zone from contributing significantly to the combined response through early attenuation of the woofer. PUBLISHED MEASUREMENT-GRAPH DESIGN INFERENCE
Dayton Epique EC30-4
EC30-4: 30 mm aluminum dome with vapor-deposited ceramic coating. It is not a solid ceramic dome nor a diamond tweeter. 3.6 mm faceplate and honeycomb grille. Fs ≈700 Hz per Dayton / 684 Hz measured by K+T. These are two distinct datasets: manufacturer's datasheet versus measurement of the sample analyzed by Klang+Ton. The copper shorting rings and low inductance are documented by the sources; that these characteristics, together with the low Fs and motor system, contribute to the viability of the ≈1.8 kHz crossover is a DESIGN INFERENCE. PUBLISHED Dayton MEASURED K+T
3. The acoustic problem of this 22 cm 2-way
- Rising directivity toward 2 kHz: the SIG225-4 becomes progressively more directive as it approaches 2 kHz; the off-axis response begins to fall relative to the on-axis response.
- Upper breakup modes, including ≈7.5 kHz: visible in the individual response of the SIG225-4, in a zone the design avoids through early attenuation of the woofer.
- Crossover strategy: the strategy adopted is to attenuate the woofer before that zone, rather than attempting to EQ-correct a response whose directivity is already narrowing and whose upper modes appear later.
- Need for a relatively low crossover: shifting the transition toward ≈1.8 kHz acoustic allows the critical band to be delivered to a transducer whose dispersion characteristics are compatible with the transition.
Project hinge: SIG225-4 → directivity/breakup → 1.8 kHz crossover → EC30-4 → faceted baffle.
4. Crossover + baffle — the acoustic solution
Electrical filter — PUBLISHED K+T:
- Woofer: 2.0 mH + 18 µF
- Tweeter: 8.2 µF + 0.39 mH + 3.9 Ω
Electrical filter ≠ acoustic crossover. The 2.0 mH + 18 µF low-pass and 8.2 µF + 0.39 mH + 3.9 Ω high-pass values should not be interpreted using the resonant frequency of an idealized LC as if that were directly the acoustic crossover frequency. In a real cabinet, the complex impedance of the transducers, voice-coil inductance, electroacoustic response, baffle diffraction and relative phase between both ways come into play. TECHNICAL INFERENCE
Klang+Ton places the acoustic transition at 1,800 Hz and describes a clean and approximately symmetrical sum between both ways. PUBLISHED K+T
Acoustic function of the baffle: the faceted baffle shapes edge diffraction, modifies the axial and angular response and contributes to a coherent directivity transition between both transducers. It is part of the acoustic conditions under which the filter was designed.
Synthesis: SIG225-4 used up to the transition zone, EC30-4 capable of assuming the crossover around 1.8 kHz, attenuation of the woofer before its upper modes and baffle geometry integrated into the acoustic solution. Integration > complexity.
5. Directivity and off-axis response
Angular response nuance: K+T notes that, due to the inverted dome shape of the EC30-4, the off-axis curves sit slightly above the on-axis response in the transition zone, helping to compensate for the rest of the baffle step. PUBLISHED K+T MEASUREMENT-GRAPH
0°–45° curves: K+T notes the absence of the directivity step usual in many 2-way designs of this size. The curves show a progressive angular evolution in the crossover zone, while the most evident directivity concentration appears mainly above about 8 kHz. PUBLISHED MEASUREMENT-GRAPH
Spatial response: The ≈3 kHz on-axis dip decreases off-axis. An electrical correction intended to eliminate exclusively that axial depression does not necessarily improve the integrated spatial response. The priority is a spatially coherent transition, not a flat on-axis line. INFERENCE
6. Enclosure and bass-reflex
24–25 L volume — PUBLISHED. Bass-reflex architecture. Ø50 × 12 cm port as reference for free-standing placement on stands, with 20 cm as an alternative. Modifying the port length changes the tuning frequency and, with it, the extension and distribution of the bass reinforcement; it can also change the enclosure's interaction with the room and walls. There is no "better" length in absolute terms: it depends on placement and the extension goal. INFERENCE
Construction: 25 mm faceted baffle, internal cross bracing and 4× Sonofil without blocking the port passage. PUBLISHED
Faceted oak baffles: active part of the acoustic system. Variant cabinet — commercial information and construction variants at the manufacturer's source, see §12.
Why it is not a geometrically interchangeable box: Keeping only volume + drivers + filter and building a "similar box" does not allow assuming that the response will be preserved. The project depends on the interaction between driver, baffle, acoustic centers, filter and enclosure. INFERENCE — geometric dependency
Fb — CLIO reading: The presence of two impedance maxima and a valley around 40 Hz is compatible with a bass-reflex tuning close to that frequency. VISUAL CLIO ESTIMATE
| Parameter | Visual estimate |
|---|---|
| 1st maximum | ≈23 Ω @ ≈26 Hz |
| 2nd maximum | ≈28 Ω @ ≈67 Hz |
| Valley | ≈6 Ω @ ≈40 Hz |
| Fb | ≈40 Hz — approximate value obtained from reading the impedance valley; it does not constitute a digitization of K+T's original data |
7. Frequency response, impedance and bass
Axial response 400 Hz–10 kHz: Klang+Ton's description qualifies the response as extremely balanced and practically linear on axis.
"Der Frequenzgang ist extrem ausgewogen und verläuft auf Achse nahezu linear."
"The frequency response is extremely balanced and, on axis, runs practically linear." — Klang+Ton. PUBLISHED K+T
Approximate reading of the CLIO graph — 400 Hz–10 kHz
The following table is an approximate reading of the published graph, not a digitization of its data. VISUAL CLIO ESTIMATE
| Band | Approximate reading |
|---|---|
| 400 Hz–2 kHz | approximately within ±1 dB |
| ≈2.5–3.5 kHz | small dip, on the order of −1 to −1.5 dB |
| 4–8 kHz | ripple approximately on the order of ±1.5 dB |
| 8–10 kHz | somewhat greater ripple, on the order of ±2 dB |
Overall summary 400 Hz–10 kHz
- The response remains very balanced.
- Most of the interval remains within an approximate margin on the order of ±1.5–2 dB relative to the reference, with small local deviations.
- No large "mountains" or wide "valleys" are observed in the published axial response.
Approximate variation relative to reference: on the order of ±1.5–2.0 dB between 400 Hz and 10 kHz. VISUAL CLIO ESTIMATE
Bass extension: F3 ≈48 Hz and F6 ≈35 Hz — VISUAL CLIO ESTIMATE. The system does not provide deep infrabass on its own and can be complemented with a subwoofer when the musical program or required level justifies it.
Impedance: nominal 4 Ω — PUBLISHED. Zmin >3.5 Ω — MEASURED K+T.
Optional RC network 56 µF + 8.2 Ω in parallel: optional network intended to smooth the impedance in the midrange. It does not convert a 4 Ω nominal load into an 8 Ω one. PUBLISHED
8. Distortion and temporal behavior
THD ≲1.5% at 95 dB: In the K+T graphs, at 95 dB SPL the THD remains below approximately 1.5% even in the bass region. This is a reading of the graphical measurement, not a global specification. MEASURED K+T MEASUREMENT-GRAPH
CSD / Waterfall: The cumulative spectrogram shows a decay without relevant prolonged resonances in the 1.8 kHz zone. MEASURED K+T MEASUREMENT-GRAPH
9. Sensitivity, power and amplification
87 dB / 2.83 V / 1 m — PUBLISHED.
For a 4 Ω nominal load, 2.83 V corresponds approximately to 2 W:
P = V² / R = 2.83² / 4 ≈ 2.00 WTherefore:
87 − 10 · log₁₀(2) ≈ 84.0 dB/W/m — CALCULATEDCalculation at 3 m / 95 dB:
84 dB/W/m @ 1 m → @ 3 m: 20 · log₁₀(3) ≈ 9.54 dB → 74.5 dB @ 3 m / 1 W For 95 dB: 20.5 dB → 10^(20.5/10) ≈ 112 W in free-field point-source modelThe calculation assumes a 6 dB drop per doubling of distance and does not incorporate room gain or directivity. It does not represent the loudspeaker's rated power nor a Klang+Ton test condition. 112 W is a mathematical result of the model, not a recommendation.
Application reference: 20–30 W / 50–100 W — INFERENCE: as an application reference, at 2.5–3 m a 20–30 W amplifier provides a reasonable baseline for normal listening with moderate headroom, while 50–100 W offer considerably greater dynamic reserve. The room, actual listening distance, the system's spatial response and the target level can substantially modify these figures.
Valve amplifiers and high output impedance: In high output impedance amplifiers, especially low-feedback valves, the output impedance, damping factor and selection of the 4 Ω tap become especially important.
5 W limitation — INFERENCE: with this sensitivity level, at 2.5–3 m a 5 W amplifier provides reduced dynamic headroom if the intention is to reproduce high dynamic range recordings at elevated levels.
10. What the sources and measurements support — and what they do not
What the sources and measurements support
- coherence of the 1.8 kHz acoustic crossover strategy;
- integration between directivity, crossover and faceted baffle as a coherent design strategy;
- Axial response 400 Hz–10 kHz: approximate variation on the order of ±1.5–2 dB relative to reference — VISUAL CLIO ESTIMATE;
- off-axis behavior characterized by the absence of the directivity step noted by K+T, with a more evident directivity concentration mainly above 8 kHz. PUBLISHED MEASUREMENT-GRAPH;
- strong attenuation of the SIG225-4 contribution in the upper zone: Klang+Ton explicitly states that the resonance located around 7.5 kHz is approximately 30 dB below the nominal level of the cabinet. Therefore, the breakup visible in the woofer's individual response does not imply an equivalent contribution in the combined system response. PUBLISHED K+T;
- contained distortion under the published conditions: THD ≲1.5% at 95 dB even in bass. MEASURED K+T MEASUREMENT-GRAPH
What they do not demonstrate
- clean 95 dB at 3 m with any amplifier: 112 W is a point-source free-field mathematical model, not a recommendation;
- sub-bass <30 Hz: F3≈48 Hz / F6≈35 Hz are visual estimates, not deep infrabass;
- universal suitability for amplifiers: 4 Ω nominal demands current; in valve amplifiers with output transformers, the 4 Ω tap, output impedance and damping factor become especially important;
- that a 20 cm port is "better": it modifies Fb and extension, depending on room and placement;
- that any filter modification preserves the original response: the geometry is not interchangeable and the filter operates within the project's integration conditions;
- universal optimization for any room: room, distance and gain modify the power and bass figures;
- that it presents automatic brightness from treble elevation;
- that changing the tweeter resistor necessarily improves the result;
- that it does not need a subwoofer to reproduce the deepest bass.
Evidence summary — types used:
| Claim | Evidence |
|---|---|
| 2-way BR, 24–25 L | PUBLISHED |
| SIG225 + EC30, 30 mm aluminum dome with vapor-deposited ceramic coating | PUBLISHED |
| 4 Ω / 87 dB / 2.83 V | PUBLISHED |
| ≈84 dB/W/m | CALCULATED |
| ≈1.8 kHz crossover | PUBLISHED K+T |
| Greater directivity concentration >≈8 kHz and absence of the step noted by K+T | PUBLISHED / MEASUREMENT-GRAPH |
| THD ≲1.5% at 95 dB even in bass | MEASURED K+T / MEASUREMENT-GRAPH; not a global specification |
| Fb ≈40 Hz / F3≈48 Hz / F6≈35 Hz | VISUAL CLIO ESTIMATE |
| Power 20–30 W baseline / 50–100 W headroom | INFERENCE — application reference, not an objective property |
11. Conclusion
The Grand Diamond shows concretely how, in a 22 cm 2-way, the result can depend less on extending the woofer's response into more octaves than on removing it from the problematic band at the right moment and making its directivity compatible with that of the tweeter in the transition zone. The crossover, the baffle geometry and the transducers themselves form a single acoustic system here.
Adequate selection, a well-chosen crossover frequency and carefully designed baffle geometry make a relatively simple passive produce an acoustic response notably more sophisticated than its electrical schematic, considered in isolation, might suggest.
12. Sources and methodology
Primary sources — proposed order:
- Klang+Ton 5/2026: print edition and e-paper with plans, filter and original measurements.
- K+T review / hifitest: Klang+Ton-Projekt „Grand Diamond" – Lautsprecherbausätze im Test — technical description SIG225-4 / EC30-4, filter 2.0 mH + 18 µF / 8.2 µF + 0.39 mH + 3.9 Ω, CLIO measurements and listening assessment. PUBLISHED K+T
- Official video: Grand Diamond 💎 Die große Schwester der Diamond — presentation 25 L, drivers, faceted cabinet, measurements and listening. PUBLISHED K+T
- Dayton documentation: SIG225-4 and EC30-4 datasheets — Fs, Qts, Vas, sensitivity, tweeter Fs ≈700 Hz. PUBLISHED Dayton
Cabinet / Bausatz — Variant GmbH:
- variant-hifi.com — Gehäuse / Schallwände — manufacturer of the faceted cabinets. Molkereistr. 3, 35039 Marburg, info@variant-hifi.de, +49 (0)6421-483909. PUBLISHED K+T / Variant
- Construction variants: faceted baffle only with rebates, complete MDF kit (≈120 € on Diamond) or plywood. Listed at Alle Gehäusebausätze. PUBLISHED K+T / Variant
- Commercial information and variants at the manufacturer's source — not part of the central acoustic analysis.
Bibliographic note: the hifitest web page shows "8/2026" in one of its metadata fields, but the article itself expressly identifies the test as belonging to Klang+Ton 5/2026, a coincidence also appearing in the Variant product reference. Klang+Ton 5/2026 is adopted as the bibliographic reference for the project.
Nauscopio Scipiorum methodology:
- PUBLISHED — Explicit data in project documentation —Klang+Ton 5/2026— or in manufacturer datasheets.
- MEASURED K+T — Result of measurements performed by Klang+Ton on a specific sample, when the original report reports it precisely.
- PUBLISHED / MEASUREMENT-GRAPH — Data published by K+T whose magnitude or behavior is interpreted from its original graph. It is not a Nauscopio measurement; it is a reading of the graph published by K+T to verify the described behavior.
- VISUAL CLIO ESTIMATE — Approximate reading of published graphs, performed as precisely as possible but without digitizing the measurement. It should not be interpreted as an independent measurement.
- CALCULATED — Arithmetic result derived from previous data, showing the formula used when relevant.
- INFERENCE — Application interpretation for a concrete listening situation. It does not constitute an objective property of the system nor a closed recommendation.
- DESIGN INFERENCE — Interpretation of why certain transducer characteristics contribute to the viability of a concrete design decision. For example: low Fs + robust motor system + low inductance → viability of an ≈1.8 kHz acoustic crossover.
Editorial rule: no visual reading of a graph is converted into a digitized measurement. When the value comes from an approximate reading performed on a graph, it is marked as VISUAL CLIO ESTIMATE. When it is a measurement published by K+T whose magnitude or behavior is interpreted visually, the category MEASURED K+T / MEASUREMENT-GRAPH is retained, as applicable. When it comes from a calculation, the formula is shown. When it comes from an application interpretation, it is marked as INFERENCE.
A graphical reading does not become an independent measurement by the fact of expressing its numerical value. This convention allows distinguishing between K+T's original experimental result, the reading of its graphs, the derived calculations and the technical interpretations made in this report.
