REDCATT

REDCATT · Manufacturing evidence

What 149,098 shipped drivers say about our production consistency

Three years of real end-of-line measurements from two high-volume OEM programs — every shipped unit counted once, published as distributions rather than claims.

Every driver REDCATT ships passes an automated acoustic test before it leaves the line. This page shows what those tests recorded for two OEM products in series production from 2023 to 2026: 149,098 shipped units in total, each counted once by its final test record. The products are REDCATT's own transducer designs, manufactured for OEM customers — anonymized here under the confidentiality those programs require — and the data is untouched: it comes directly from the test-station databases, unit by unit, with serial-number and timestamp traceability.

How the measurement works — read this first

Each production line ends in an in-line acoustic test station: a measurement box of roughly 1.2 × 1.2 m with a microphone about 40 cm from the driver under test. Every unit is placed in the box and measured automatically — DC resistance, impedance curve, resonance frequency, output level, frequency response, distortion, Rub & Buzz, and polarity.

driver microphone ≈ 40 cm ≈ 1.2 m in-line test box on the production line — every unit passes through it
This is not an anechoic chamber — by design. A small box with a close microphone has reflections and boundary effects, so the absolute SPL values and curve shapes here differ significantly from free-field datasheet measurements. That is irrelevant to the question this station answers, because the test is comparative: before production starts, a golden sample — a reference unit validated in the lab — is measured in the same box, and every production unit is compared against it under identical conditions. Acceptance limits are derived from the golden sample's measurement. What you should read from every chart on this page is spread, never absolute values.

Who is in the data: all units that passed the end-of-line test — that is, the units that actually shipped — each counted once, by its final test record. Units that never met the limits are not shipped and are excluded, so these distributions describe what a customer receives; the size of that share is published for each program below as the final acceptance yield, year by year. Test temperature and humidity are recorded with every measurement.

How to read the charts. Histograms show how many units (vertical) measured a given value (horizontal); a tall narrow shape means high consistency. σ ("sigma") is the standard deviation: about two-thirds of all units fall within ±1σ of the mean. Red dashed lines are acceptance limits; the red curve or line is always the golden reference.

Program A — high-frequency compression driver

A REDCATT-designed transducer in series production for an OEM program since 2023-07. Every figure below is computed from the final end-of-line test record of every unit that shipped — each unit counted once.

52,621
shipped units in this dataset
2023-07 – 2026-08
production period
15 / 39
production batches / test-station sessions
±0.18 dB
sensitivity spread (1σ) vs golden sample
98.8%
final acceptance yield, 2026 to date
99.5% of 52,621 units measured within ±0.5 dB of the golden-referenced mean — and >99.99% within ±1 dB. The worst single month in 30 months of production averaged 0.36 dB from the golden sample.

Final acceptance yield, year by year

This table shows, of the units reaching the end-of-line test station, the share that ultimately met every acceptance limit and shipped. A unit that fails is not necessarily scrapped: where the design allows a mechanical adjustment it is re-worked and re-tested, and every unit is counted once, by its final test result. Units that never meet the limits are not shipped. Units rejected at earlier assembly stations never reach this test, so this is the acoustic-test yield, not a total build yield.

YearUnits reaching final testShipped (met every limit)Final yield
20232,3762,12789.5%
202423,21121,30791.8%
202522,24421,69897.5%
2026 (through Aug)7,5797,48998.8%
Whole period55,41052,62195.0%

For this compression driver the typical adjustment is re-shimming the magnetic gap — a normal tuning step, not a defect repair. The 2023–2024 figures reflect the program's ramp-up phase; as the assembly and gap-shimming process matured, the yield rose to 97.5% in 2025 and 98.8% in 2026.

Sensitivity, unit by unit

Each driver's output level is measured and compared with the golden sample on the same station. This chart shows how far each shipped unit landed from its golden reference — 0 dB means "identical to the golden sample". Mean deviation -0.02 dB, spread ±0.18 dB (1σ); every unit fits inside the plotted range. Red dashed lines are the most common acceptance limits.

2,1114,2226,3338,444-1.156–-1.088 dB vs golden: 1 unit-1.088–-1.02 dB vs golden: 1 unit-1.02–-0.952 dB vs golden: 2 units-0.884–-0.816 dB vs golden: 4 units-0.816–-0.748 dB vs golden: 2 units-0.748–-0.68 dB vs golden: 11 units-0.68–-0.612 dB vs golden: 20 units-0.612–-0.544 dB vs golden: 72 units-0.544–-0.476 dB vs golden: 199 units-0.476–-0.408 dB vs golden: 485 units-0.408–-0.34 dB vs golden: 1,046 units-0.34–-0.272 dB vs golden: 2,037 units-0.272–-0.204 dB vs golden: 3,576 units-0.204–-0.136 dB vs golden: 5,646 units-0.136–-0.068 dB vs golden: 7,705 units-0.068–0 dB vs golden: 8,444 units0–0.068 dB vs golden: 7,611 units0.068–0.136 dB vs golden: 6,044 units0.136–0.204 dB vs golden: 4,167 units0.204–0.272 dB vs golden: 2,839 units0.272–0.34 dB vs golden: 1,689 units0.34–0.408 dB vs golden: 692 units0.408–0.476 dB vs golden: 227 units0.476–0.544 dB vs golden: 70 units0.544–0.612 dB vs golden: 28 units0.612–0.68 dB vs golden: 1 unit0.68–0.748 dB vs golden: 1 unit0.816–0.884 dB vs golden: 1 unit-1.632-0.9792-0.32640.32640.97921.632dB vs goldenlower limitupper limitmean

Resonance frequency (fs)

The resonance frequency of every shipped unit, against the most common acceptance window (800–1,300 Hz). Mean 1,077.8 Hz, spread ±59.7 Hz (1σ), i.e. ±5.5% relative. A distribution well inside its window means consistent moving mass and suspension stiffness — the parameters that drift first when a production process is not controlled. Every shipped unit lies inside this window.

1,3042,6083,9125,217851.7–865.8 Hz: 8 units865.8–880 Hz: 10 units880–894.2 Hz: 22 units894.2–908.3 Hz: 58 units908.3–922.5 Hz: 98 units922.5–936.7 Hz: 141 units936.7–950.8 Hz: 245 units950.8–965 Hz: 486 units965–979.2 Hz: 959 units979.2–993.3 Hz: 1,473 units993.3–1,008 Hz: 2,167 units1,008–1,022 Hz: 3,163 units1,022–1,036 Hz: 4,031 units1,036–1,050 Hz: 4,701 units1,050–1,064 Hz: 5,217 units1,064–1,078 Hz: 5,108 units1,078–1,092 Hz: 4,823 units1,092–1,107 Hz: 4,281 units1,107–1,121 Hz: 3,643 units1,121–1,135 Hz: 3,121 units1,135–1,149 Hz: 2,413 units1,149–1,163 Hz: 1,999 units1,163–1,178 Hz: 1,476 units1,178–1,192 Hz: 1,057 units1,192–1,206 Hz: 722 units1,206–1,220 Hz: 500 units1,220–1,234 Hz: 277 units1,234–1,248 Hz: 165 units1,248–1,262 Hz: 106 units1,262–1,277 Hz: 76 units1,277–1,291 Hz: 49 units1,291–1,305 Hz: 26 units7108469821,1181,2541,390Hzlower limitupper limitmean

Voice-coil DC resistance (Re)

Re reflects the winding process itself: wire, layers, tension. Mean 12.840 Ω, spread ±0.368 Ω (1σ). 9 of 52,621 units sit outside the plotted range — accepted under period windows re-derived from the golden sample, wider than the most common one drawn here; no unit shipped outside its own window.

1,0532,1063,1594,21311.04–11.11 Ω: 1 unit11.11–11.18 Ω: 1 unit11.18–11.25 Ω: 1 unit11.25–11.33 Ω: 1 unit11.33–11.4 Ω: 4 units11.4–11.47 Ω: 11 units11.47–11.54 Ω: 6 units11.54–11.62 Ω: 17 units11.62–11.69 Ω: 20 units11.69–11.76 Ω: 42 units11.76–11.83 Ω: 55 units11.83–11.91 Ω: 109 units11.91–11.98 Ω: 169 units11.98–12.05 Ω: 292 units12.05–12.12 Ω: 466 units12.12–12.2 Ω: 767 units12.2–12.27 Ω: 1,071 units12.27–12.34 Ω: 1,482 units12.34–12.41 Ω: 1,944 units12.41–12.49 Ω: 2,359 units12.49–12.56 Ω: 2,865 units12.56–12.63 Ω: 3,247 units12.63–12.7 Ω: 3,776 units12.7–12.77 Ω: 4,058 units12.77–12.85 Ω: 4,213 units12.85–12.92 Ω: 4,125 units12.92–12.99 Ω: 3,821 units12.99–13.06 Ω: 3,502 units13.06–13.14 Ω: 3,167 units13.14–13.21 Ω: 2,661 units13.21–13.28 Ω: 2,282 units13.28–13.35 Ω: 1,742 units13.35–13.43 Ω: 1,350 units13.43–13.5 Ω: 985 units13.5–13.57 Ω: 727 units13.57–13.64 Ω: 471 units13.64–13.72 Ω: 317 units13.72–13.79 Ω: 199 units13.79–13.86 Ω: 129 units13.86–13.93 Ω: 69 units13.93–14.01 Ω: 48 units14.01–14.08 Ω: 22 units14.08–14.15 Ω: 8 units14.15–14.22 Ω: 3 units14.22–14.3 Ω: 1 unit14.3–14.37 Ω: 3 units14.37–14.44 Ω: 3 units11.0411.7312.4313.1213.8214.51Ωlower limitupper limitmean

Month by month, 30 months

The blue line is the monthly average output level of production units; the band around it is ±1σ for that month; the red line is the golden reference itself as re-measured over time. Note the magnified scale: the total range of the monthly means over the whole period is 0.63 dB. The two lines moving together is the point — shared movement comes from the station and its environment, and production tracks the reference through 30 months, seasons, and material lots. Months with fewer than 100 units are left off this chart.

119.6119.9120.2120.5120.82023-07: mean 120.18 dB, σ 0.12, n=2852023-12: mean 120.37 dB, σ 0.19, n=1,7792024-01: mean 120.30 dB, σ 0.22, n=2,0362024-02: mean 120.43 dB, σ 0.19, n=1,9662024-03: mean 120.20 dB, σ 0.12, n=2,2042024-04: mean 120.31 dB, σ 0.12, n=8892024-05: mean 120.41 dB, σ 0.11, n=3,3372024-06: mean 119.95 dB, σ 0.13, n=2,2222024-07: mean 119.93 dB, σ 0.14, n=1,5622024-08: mean 120.14 dB, σ 0.15, n=2,1182024-09: mean 119.83 dB, σ 0.13, n=7032024-11: mean 120.31 dB, σ 0.13, n=2,5162024-12: mean 120.33 dB, σ 0.18, n=1,7542025-01: mean 120.29 dB, σ 0.10, n=1,9072025-02: mean 120.46 dB, σ 0.19, n=1,7392025-03: mean 120.32 dB, σ 0.14, n=1,5252025-04: mean 120.26 dB, σ 0.14, n=9792025-05: mean 120.04 dB, σ 0.14, n=1,7642025-06: mean 119.98 dB, σ 0.15, n=1862025-07: mean 120.05 dB, σ 0.12, n=3,9672025-08: mean 120.22 dB, σ 0.11, n=2,0602025-09: mean 120.04 dB, σ 0.11, n=2,4642025-10: mean 119.98 dB, σ 0.13, n=2,3012025-11: mean 120.28 dB, σ 0.10, n=7502025-12: mean 120.17 dB, σ 0.17, n=2,0562026-03: mean 120.18 dB, σ 0.10, n=1,6732026-05: mean 120.45 dB, σ 0.11, n=1,6652026-06: mean 120.15 dB, σ 0.11, n=1,1932026-07: mean 120.17 dB, σ 0.14, n=1,9182026-08: mean 119.93 dB, σ 0.10, n=1,0362023-072024-022024-052024-082024-122025-032025-062025-092025-122026-06production monthly meangolden reference

The same view for resonance frequency, with the fixed acceptance limits in red — note how much headroom the production spread keeps inside the window.

7408951,0501,2051,360limitlimit2023-07: mean 1,043.7 Hz, σ 48.7, n=2852023-12: mean 1,072.8 Hz, σ 67.2, n=1,7792024-01: mean 1,135.7 Hz, σ 57.0, n=2,0362024-02: mean 1,159.3 Hz, σ 44.9, n=1,9662024-03: mean 1,083.3 Hz, σ 67.0, n=2,2042024-04: mean 1,068.4 Hz, σ 73.6, n=8892024-05: mean 1,072.9 Hz, σ 46.6, n=3,3372024-06: mean 1,069.3 Hz, σ 69.3, n=2,2222024-07: mean 1,066.8 Hz, σ 50.0, n=1,5622024-08: mean 1,056.0 Hz, σ 45.6, n=2,1182024-09: mean 1,080.2 Hz, σ 49.6, n=7032024-11: mean 1,102.1 Hz, σ 64.3, n=2,5162024-12: mean 1,085.8 Hz, σ 58.2, n=1,7542025-01: mean 1,087.7 Hz, σ 53.2, n=1,9072025-02: mean 1,095.3 Hz, σ 60.5, n=1,7392025-03: mean 1,060.3 Hz, σ 59.4, n=1,5252025-04: mean 1,075.2 Hz, σ 76.3, n=9792025-05: mean 1,078.8 Hz, σ 49.7, n=1,7642025-06: mean 1,058.5 Hz, σ 53.2, n=1862025-07: mean 1,077.0 Hz, σ 47.4, n=3,9672025-08: mean 1,056.5 Hz, σ 27.4, n=2,0602025-09: mean 1,019.1 Hz, σ 40.3, n=2,4642025-10: mean 1,077.5 Hz, σ 41.5, n=2,3012025-11: mean 1,143.9 Hz, σ 60.5, n=7502025-12: mean 1,080.1 Hz, σ 55.4, n=2,0562026-03: mean 1,078.9 Hz, σ 40.5, n=1,6732026-05: mean 1,057.4 Hz, σ 39.8, n=1,6652026-06: mean 1,051.8 Hz, σ 32.5, n=1,1932026-07: mean 1,065.4 Hz, σ 47.5, n=1,9182026-08: mean 1,037.3 Hz, σ 37.0, n=1,0362023-072024-022024-052024-082024-122025-032025-062025-092025-122026-06production monthly mean

150 drivers against one golden sample

The blue band shows where the frequency responses of 150 production units from one batch fall: the darker band holds the middle half of all drivers, the lighter band 90% of them. The red line is the golden reference they were tested against — it runs through the middle of the band because production and reference are, in practice, the same. Through the working band the unit-to-unit spread is about ±0.26 dB (1σ), widening toward the very top of the range where cone/diaphragm break-up makes every driver's response most individual — normal physics, not process variation. Remember from "How the measurement works": the curve shape belongs to the 1.2 m test box and the 40 cm microphone, not the driver's free-field response — read the band's tightness, not the shape.

951031111201281k2k5k10kfrequency, Hz (log)shaded: where 90% of drivers fall (darker: the middle 50%)golden reference sampledB

The engineer's view of the same data — every one of the 150 units drawn individually, golden reference in red:

89991091181281k2k5k10kfrequency, Hz (log)production units (each thin line is one driver)golden reference sampledB

Program B — low-frequency woofer

A REDCATT-designed transducer in series production for an OEM program since 2023-08. Every figure below is computed from the final end-of-line test record of every unit that shipped — each unit counted once.

96,477
shipped units in this dataset
2023-08 – 2026-08
production period
14 / 60
production batches / test-station sessions
±0.21 dB
sensitivity spread (1σ) vs golden sample
99.5%
final acceptance yield, 2026 to date
98.4% of 96,235 units measured within ±0.5 dB of the golden-referenced mean — and >99.99% within ±1 dB. The worst single month in 34 months of production averaged 0.34 dB from the golden sample.

Final acceptance yield, year by year

This table shows, of the units reaching the end-of-line test station, the share that ultimately met every acceptance limit and shipped. A unit that fails is not necessarily scrapped: where the design allows a mechanical adjustment it is re-worked and re-tested, and every unit is counted once, by its final test result. Units that never meet the limits are not shipped. Units rejected at earlier assembly stations never reach this test, so this is the acoustic-test yield, not a total build yield.

YearUnits reaching final testShipped (met every limit)Final yield
202313,37413,28499.3%
202428,77928,36598.6%
202524,12523,87499.0%
2026 (through Aug)31,11130,95499.5%
Whole period97,38996,47799.1%

Sensitivity, unit by unit

Each driver's output level is measured and compared with the golden sample on the same station. This chart shows how far each shipped unit landed from its golden reference — 0 dB means "identical to the golden sample". Mean deviation +0.09 dB, spread ±0.21 dB (1σ); every unit fits inside the plotted range. 242 early units lack a stored reference value and are not part of this comparison. Red dashed lines are the most common acceptance limits.

4,8669,73214,59819,465-1.02–-0.9067 dB vs golden: 3 units-0.9067–-0.7933 dB vs golden: 7 units-0.7933–-0.68 dB vs golden: 54 units-0.68–-0.5667 dB vs golden: 138 units-0.5667–-0.4533 dB vs golden: 375 units-0.4533–-0.34 dB vs golden: 1,333 units-0.34–-0.2267 dB vs golden: 3,919 units-0.2267–-0.1133 dB vs golden: 9,577 units-0.1133–0 dB vs golden: 16,367 units0–0.1133 dB vs golden: 19,465 units0.1133–0.2267 dB vs golden: 18,987 units0.2267–0.34 dB vs golden: 14,842 units0.34–0.4533 dB vs golden: 7,754 units0.4533–0.5667 dB vs golden: 2,572 units0.5667–0.68 dB vs golden: 655 units0.68–0.7933 dB vs golden: 128 units0.7933–0.9067 dB vs golden: 44 units0.9067–1.02 dB vs golden: 15 units-2.72-1.632-0.5440.5441.6322.72dB vs goldenlower limitupper limitmean

Resonance frequency (fs)

The resonance frequency of every shipped unit, against the most common acceptance window (56–76 Hz). Mean 64.1 Hz, spread ±2.45 Hz (1σ), i.e. ±3.8% relative. A distribution well inside its window means consistent moving mass and suspension stiffness — the parameters that drift first when a production process is not controlled. Acceptance windows are re-derived from the golden sample's measurement per production period; 4 units from an early run were accepted under a slightly different window and sit outside the lines drawn here — no unit shipped outside its own window.

2,0824,1646,2468,32854.1–54.67 Hz: 1 unit55.23–55.8 Hz: 3 units55.8–56.37 Hz: 9 units56.37–56.93 Hz: 32 units56.93–57.5 Hz: 60 units57.5–58.07 Hz: 150 units58.07–58.63 Hz: 331 units58.63–59.2 Hz: 622 units59.2–59.77 Hz: 1,137 units59.77–60.33 Hz: 2,206 units60.33–60.9 Hz: 3,486 units60.9–61.47 Hz: 5,177 units61.47–62.03 Hz: 6,783 units62.03–62.6 Hz: 7,830 units62.6–63.17 Hz: 8,197 units63.17–63.73 Hz: 8,328 units63.73–64.3 Hz: 8,261 units64.3–64.87 Hz: 8,192 units64.87–65.43 Hz: 7,759 units65.43–66 Hz: 7,128 units66–66.57 Hz: 6,053 units66.57–67.13 Hz: 4,766 units67.13–67.7 Hz: 3,346 units67.7–68.27 Hz: 2,088 units68.27–68.83 Hz: 1,316 units68.83–69.4 Hz: 891 units69.4–69.97 Hz: 642 units69.97–70.53 Hz: 513 units70.53–71.1 Hz: 335 units71.1–71.67 Hz: 308 units71.67–72.23 Hz: 208 units72.23–72.8 Hz: 152 units72.8–73.37 Hz: 96 units73.37–73.93 Hz: 38 units73.93–74.5 Hz: 17 units74.5–75.07 Hz: 5 units75.07–75.63 Hz: 7 units75.63–76.2 Hz: 4 units52.457.8463.2868.7274.1679.6Hzlower limitupper limitmean

Voice-coil DC resistance (Re)

Re reflects the winding process itself: wire, layers, tension. Mean 2.021 Ω, spread ±0.087 Ω (1σ). The two visible groups are separated in time, not mixed production: units in the slightly higher group were built during 2024–2025, and 2026 production is back at the original value. Both groups sit well inside the acceptance limits. 621 of 96,477 units sit outside the plotted range — accepted under period windows re-derived from the golden sample, wider than the most common one drawn here; no unit shipped outside its own window.

1,9843,9695,9547,9391.785–1.796 Ω: 1 unit1.796–1.807 Ω: 1 unit1.807–1.819 Ω: 5 units1.819–1.83 Ω: 22 units1.83–1.841 Ω: 56 units1.841–1.853 Ω: 90 units1.853–1.864 Ω: 295 units1.864–1.875 Ω: 619 units1.875–1.887 Ω: 716 units1.887–1.898 Ω: 897 units1.898–1.909 Ω: 1,185 units1.909–1.921 Ω: 1,758 units1.921–1.932 Ω: 2,553 units1.932–1.943 Ω: 3,488 units1.943–1.955 Ω: 5,666 units1.955–1.966 Ω: 6,603 units1.966–1.977 Ω: 7,597 units1.977–1.989 Ω: 7,939 units1.989–2 Ω: 7,581 units2–2.011 Ω: 7,419 units2.011–2.023 Ω: 7,255 units2.023–2.034 Ω: 6,182 units2.034–2.045 Ω: 4,649 units2.045–2.057 Ω: 3,413 units2.057–2.068 Ω: 2,347 units2.068–2.079 Ω: 1,547 units2.079–2.091 Ω: 901 units2.091–2.102 Ω: 675 units2.102–2.113 Ω: 565 units2.113–2.125 Ω: 799 units2.125–2.136 Ω: 1,058 units2.136–2.147 Ω: 892 units2.147–2.159 Ω: 820 units2.159–2.17 Ω: 789 units2.17–2.181 Ω: 941 units2.181–2.193 Ω: 1,291 units2.193–2.204 Ω: 1,230 units2.204–2.215 Ω: 1,240 units2.215–2.227 Ω: 1,311 units2.227–2.238 Ω: 1,354 units2.238–2.249 Ω: 1,083 units2.249–2.261 Ω: 643 units2.261–2.272 Ω: 380 units1.7281.8371.9462.0542.1632.272Ωlower limitupper limitmean

Month by month, 34 months

The blue line is the monthly average output level of production units; the band around it is ±1σ for that month; the red line is the golden reference itself as re-measured over time. Note the magnified scale: the total range of the monthly means over the whole period is 0.91 dB. The two lines moving together is the point — shared movement comes from the station and its environment, and production tracks the reference through 34 months, seasons, and material lots. Months with fewer than 100 units are left off this chart.

117.6118.0118.4118.9119.32023-08: mean 118.07 dB, σ 0.18, n=2,2532023-09: mean 117.98 dB, σ 0.15, n=2,0192023-10: mean 118.11 dB, σ 0.13, n=3,3862023-12: mean 118.13 dB, σ 0.14, n=5,6262024-01: mean 118.08 dB, σ 0.12, n=8192024-02: mean 118.44 dB, σ 0.21, n=1,4272024-03: mean 118.29 dB, σ 0.18, n=2,6882024-04: mean 118.36 dB, σ 0.17, n=2,9292024-05: mean 118.66 dB, σ 0.24, n=4,6792024-06: mean 118.35 dB, σ 0.23, n=3,2232024-07: mean 118.00 dB, σ 0.15, n=2,4332024-08: mean 118.15 dB, σ 0.17, n=2,3382024-09: mean 118.35 dB, σ 0.15, n=2,7252024-10: mean 118.30 dB, σ 0.13, n=2,2572024-12: mean 118.37 dB, σ 0.15, n=2,8422025-01: mean 118.05 dB, σ 0.16, n=1,8312025-03: mean 118.64 dB, σ 0.28, n=2,7752025-04: mean 118.85 dB, σ 0.27, n=1,3502025-05: mean 118.34 dB, σ 0.15, n=3,2052025-06: mean 118.62 dB, σ 0.15, n=2,5422025-07: mean 118.35 dB, σ 0.12, n=1,7932025-08: mean 118.38 dB, σ 0.11, n=3,3932025-09: mean 118.52 dB, σ 0.12, n=2,0552025-10: mean 118.34 dB, σ 0.16, n=8082025-11: mean 118.24 dB, σ 0.18, n=3,1192025-12: mean 118.60 dB, σ 0.13, n=1,0032026-01: mean 118.57 dB, σ 0.17, n=4,3302026-02: mean 118.37 dB, σ 0.14, n=8622026-03: mean 118.42 dB, σ 0.17, n=3,6882026-04: mean 118.20 dB, σ 0.15, n=3,1932026-05: mean 118.33 dB, σ 0.17, n=4,8372026-06: mean 118.14 dB, σ 0.24, n=1,8722026-07: mean 118.15 dB, σ 0.16, n=4,5142026-08: mean 117.94 dB, σ 0.22, n=7,6582023-082024-012024-052024-092025-032025-072025-112026-032026-07production monthly meangolden reference

The same view for resonance frequency, with the fixed acceptance limits in red — note how much headroom the production spread keeps inside the window.

53.659.866.072.278.4limitlimit2023-08: mean 62.69 Hz, σ 1.48, n=2,2532023-09: mean 62.71 Hz, σ 1.38, n=2,0192023-10: mean 63.32 Hz, σ 1.24, n=3,3862023-12: mean 62.06 Hz, σ 1.63, n=5,6262024-01: mean 66.22 Hz, σ 4.11, n=8192024-02: mean 64.60 Hz, σ 1.58, n=1,4272024-03: mean 61.07 Hz, σ 2.06, n=2,6882024-04: mean 62.77 Hz, σ 1.96, n=2,9292024-05: mean 64.69 Hz, σ 2.35, n=4,6792024-06: mean 63.83 Hz, σ 2.20, n=3,2232024-07: mean 65.90 Hz, σ 1.66, n=2,4332024-08: mean 63.65 Hz, σ 1.65, n=2,3382024-09: mean 63.86 Hz, σ 1.98, n=2,7252024-10: mean 63.21 Hz, σ 1.30, n=2,2572024-12: mean 66.21 Hz, σ 1.71, n=2,8422025-01: mean 65.70 Hz, σ 1.45, n=1,8312025-03: mean 65.09 Hz, σ 1.28, n=2,7752025-04: mean 63.30 Hz, σ 1.51, n=1,3502025-05: mean 63.25 Hz, σ 1.75, n=3,2052025-06: mean 62.06 Hz, σ 1.78, n=2,5422025-07: mean 60.77 Hz, σ 1.22, n=1,7932025-08: mean 61.69 Hz, σ 1.12, n=3,3932025-09: mean 62.69 Hz, σ 1.37, n=2,0552025-10: mean 64.02 Hz, σ 1.20, n=8082025-11: mean 63.47 Hz, σ 2.04, n=3,1192025-12: mean 65.85 Hz, σ 1.50, n=1,0032026-01: mean 68.87 Hz, σ 2.03, n=4,3302026-02: mean 66.09 Hz, σ 2.28, n=8622026-03: mean 65.95 Hz, σ 1.29, n=3,6882026-04: mean 64.53 Hz, σ 1.09, n=3,1932026-05: mean 63.50 Hz, σ 1.04, n=4,8372026-06: mean 65.85 Hz, σ 0.98, n=1,8722026-07: mean 65.83 Hz, σ 1.30, n=4,5142026-08: mean 64.63 Hz, σ 2.03, n=7,6582023-082024-012024-052024-092025-032025-072025-112026-032026-07production monthly mean

150 drivers against one golden sample

The blue band shows where the frequency responses of 150 production units from one batch fall: the darker band holds the middle half of all drivers, the lighter band 90% of them. The red line is the golden reference they were tested against — it runs through the middle of the band because production and reference are, in practice, the same. Through the working band the unit-to-unit spread is about ±0.25 dB (1σ), widening toward the very top of the range where cone/diaphragm break-up makes every driver's response most individual — normal physics, not process variation. Remember from "How the measurement works": the curve shape belongs to the 1.2 m test box and the 40 cm microphone, not the driver's free-field response — read the band's tightness, not the shape.

110113117121124501002005001k2kfrequency, Hz (log)shaded: where 90% of drivers fall (darker: the middle 50%)golden reference sampledB

The engineer's view of the same data — every one of the 150 units drawn individually, golden reference in red:

108112116121125501002005001k2kfrequency, Hz (log)production units (each thin line is one driver)golden reference sampledB

Questions this data usually raises

Why do the response curves look different from a datasheet?
Datasheet curves are measured free-field in an anechoic environment. These are measured in a 1.2 m in-line test box with the microphone at 40 cm, where reflections shape the curve. The station measures every unit the same way and compares against the golden sample measured in the same box — so the spread between curves is meaningful, while the curve shape itself is a property of the box.
What exactly is a golden sample?
A reference unit of the product, validated in the laboratory, kept at the line, and measured on the same station. Production acceptance limits are derived from its measurement, and it is re-measured over time. That is why the red reference line in the monthly charts moves slightly: the golden sample itself reads a little differently as the station's environment changes — and production moving together with it is exactly what those charts are there to show.
Why show only units that passed? And how many is that?
The distributions describe the population a customer receives, so they cover shipped units only. The count is published in each program's "Final acceptance yield" table above: over the whole period, 95–99% of units reaching the end-of-line test ultimately met every limit, and the current-year figures are 98.8% and 99.5%. Units may be tested more than once — a failing compression driver is typically re-tuned in the magnetic gap (shim washers) and re-tested, a normal mechanical tuning step — so every statistic on this page counts each unit once, by its final test record; mixing retest records into a shipped-product statistic would overstate variation.
Why are there more test-station sessions than batches?
A production batch is often tested across several station sessions: a session is opened whenever the line starts a test run, so line changeovers, multi-day batches and re-test passes each add a session. Batches count what was ordered and built; sessions count how the station recorded the work.
Are these all the units, or a sample?
All of them. The scalar statistics (sensitivity, fs, Re) cover every shipped unit in the period, with two small exceptions each chart states in place: a fraction of a percent of records lack a stored value for a given quantity (for example, the sensitivity comparison skips units with no stored golden-reference value), and the monthly charts leave off months with fewer than 100 units. Only the curve-overlay charts use a sample of the stored curves, and say so in their caption.
Can this be verified?
Yes. Every value traces to a per-unit test record with serial number and timestamp in the production test-station database. Qualified OEM customers can review project-specific records, control plans, and acceptance criteria under NDA — and factory visits are welcome.