REDCATT

REDCATT · Manufacturing evidence

What 168,941 shipped drivers say about our production consistency

Three years of real end-of-line measurements from two high-volume OEM programs — every unit, every test record, 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 manufactured continuously from 2023 to 2026: 168,941 shipped units in total. 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. Units that failed and were repaired or scrapped are excluded, so these distributions describe what a customer receives. 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 manufactured continuously for an OEM program since 2023-07. Every figure below is computed from the individual end-of-line test record of every unit that shipped.

67,752
shipped units in this dataset
2023-07 – 2026-08
production period
15 / 40
production batches / test-station sessions
±0.19 dB
sensitivity spread (1σ) vs golden sample
99.1% of all 67,752 units measured within ±0.5 dB of the golden-referenced mean — and 100% within ±1 dB. The worst single month in 31 months of production averaged 0.34 dB from the golden sample.

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 -0.04 dB, spread ±0.19 dB (1σ); every unit fits inside the plotted range. Red dashed lines are the acceptance limits.

2,6135,2267,83910,453-1.156–-1.088 dB vs golden: 1 units-1.088–-1.02 dB vs golden: 2 units-1.02–-0.952 dB vs golden: 3 units-0.884–-0.816 dB vs golden: 6 units-0.816–-0.748 dB vs golden: 32 units-0.748–-0.68 dB vs golden: 54 units-0.68–-0.612 dB vs golden: 108 units-0.612–-0.544 dB vs golden: 247 units-0.544–-0.476 dB vs golden: 481 units-0.476–-0.408 dB vs golden: 992 units-0.408–-0.34 dB vs golden: 1,880 units-0.34–-0.272 dB vs golden: 3,268 units-0.272–-0.204 dB vs golden: 5,083 units-0.204–-0.136 dB vs golden: 7,413 units-0.136–-0.068 dB vs golden: 9,716 units-0.068–-2.22e-16 dB vs golden: 10,453 units-2.22e-16–0.068 dB vs golden: 9,388 units0.068–0.136 dB vs golden: 7,343 units0.136–0.204 dB vs golden: 5,008 units0.204–0.272 dB vs golden: 3,223 units0.272–0.34 dB vs golden: 1,912 units0.34–0.408 dB vs golden: 767 units0.408–0.476 dB vs golden: 260 units0.476–0.544 dB vs golden: 78 units0.544–0.612 dB vs golden: 30 units0.612–0.68 dB vs golden: 1 units0.68–0.748 dB vs golden: 2 units0.816–0.884 dB vs golden: 1 units-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 fixed acceptance window (800–1,300 Hz). Mean 1,074.9 Hz, spread ±63.9 Hz (1σ), i.e. ±5.9% 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.

1,5823,1644,7466,329795–809.2 Hz: 3 units809.2–823.3 Hz: 3 units823.3–837.5 Hz: 4 units837.5–851.7 Hz: 3 units851.7–865.8 Hz: 29 units865.8–880 Hz: 39 units880–894.2 Hz: 67 units894.2–908.3 Hz: 146 units908.3–922.5 Hz: 222 units922.5–936.7 Hz: 374 units936.7–950.8 Hz: 595 units950.8–965 Hz: 1,054 units965–979.2 Hz: 1,607 units979.2–993.3 Hz: 2,166 units993.3–1008 Hz: 2,917 units1008–1022 Hz: 4,034 units1022–1036 Hz: 4,935 units1036–1050 Hz: 5,818 units1050–1064 Hz: 6,329 units1064–1078 Hz: 6,187 units1078–1092 Hz: 5,891 units1092–1107 Hz: 5,310 units1107–1121 Hz: 4,545 units1121–1135 Hz: 3,901 units1135–1149 Hz: 3,112 units1149–1163 Hz: 2,508 units1163–1178 Hz: 1,904 units1178–1192 Hz: 1,387 units1192–1206 Hz: 939 units1206–1220 Hz: 649 units1220–1234 Hz: 390 units1234–1248 Hz: 247 units1248–1262 Hz: 172 units1262–1277 Hz: 120 units1277–1291 Hz: 93 units1291–1305 Hz: 52 units7108469821,1181,2541,390Hzlower limitupper limitmean

Voice-coil DC resistance (Re)

Re reflects the winding process itself: wire, layers, tension. Mean 12.838 Ω, spread ±0.370 Ω (1σ).

1,2872,5743,8615,14811–11.07 Ω: 1 units11.14–11.21 Ω: 1 units11.21–11.28 Ω: 1 units11.28–11.35 Ω: 2 units11.35–11.42 Ω: 4 units11.42–11.49 Ω: 12 units11.49–11.56 Ω: 12 units11.56–11.63 Ω: 22 units11.63–11.7 Ω: 31 units11.7–11.77 Ω: 59 units11.77–11.84 Ω: 75 units11.84–11.91 Ω: 147 units11.91–11.98 Ω: 220 units11.98–12.05 Ω: 396 units12.05–12.12 Ω: 596 units12.12–12.19 Ω: 964 units12.19–12.26 Ω: 1,335 units12.26–12.33 Ω: 1,852 units12.33–12.4 Ω: 2,415 units12.4–12.47 Ω: 2,885 units12.47–12.54 Ω: 3,488 units12.54–12.61 Ω: 3,967 units12.61–12.68 Ω: 4,677 units12.68–12.75 Ω: 4,934 units12.75–12.82 Ω: 5,148 units12.82–12.9 Ω: 5,117 units12.9–12.97 Ω: 4,887 units12.97–13.04 Ω: 4,453 units13.04–13.11 Ω: 4,139 units13.11–13.18 Ω: 3,640 units13.18–13.25 Ω: 3,090 units13.25–13.32 Ω: 2,483 units13.32–13.39 Ω: 1,941 units13.39–13.46 Ω: 1,497 units13.46–13.53 Ω: 1,103 units13.53–13.6 Ω: 778 units13.6–13.67 Ω: 485 units13.67–13.74 Ω: 348 units13.74–13.81 Ω: 231 units13.81–13.88 Ω: 145 units13.88–13.95 Ω: 75 units13.95–14.02 Ω: 41 units14.02–14.09 Ω: 23 units10.7211.3912.0712.7413.4214.09Ωlower limitupper limitmean

Month by month, 31 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 31 months, seasons, and material lots.

119.6119.9120.2120.5120.72023-07: mean 120.19 dB, σ 0.13, n=5852023-12: mean 120.32 dB, σ 0.21, n=2,5042024-01: mean 120.27 dB, σ 0.26, n=2,6532024-02: mean 120.43 dB, σ 0.19, n=2,6942024-03: mean 120.20 dB, σ 0.12, n=2,2562024-04: mean 120.30 dB, σ 0.15, n=1,1242024-05: mean 120.40 dB, σ 0.11, n=3,8612024-06: mean 119.90 dB, σ 0.16, n=3,5642024-07: mean 119.87 dB, σ 0.16, n=2,3492024-08: mean 120.09 dB, σ 0.18, n=2,6962024-09: mean 119.82 dB, σ 0.13, n=8822024-11: mean 120.31 dB, σ 0.14, n=2,9482024-12: mean 120.31 dB, σ 0.19, n=2,9662025-01: mean 120.29 dB, σ 0.10, n=2,1372025-02: mean 120.45 dB, σ 0.18, n=2,2462025-03: mean 120.30 dB, σ 0.15, n=1,9752025-04: mean 120.26 dB, σ 0.14, n=9962025-05: mean 120.03 dB, σ 0.14, n=2,1412025-06: mean 119.96 dB, σ 0.15, n=3492025-07: mean 120.03 dB, σ 0.12, n=4,5882025-08: mean 120.22 dB, σ 0.11, n=2,0992025-09: mean 120.04 dB, σ 0.11, n=2,7542025-10: mean 119.96 dB, σ 0.14, n=2,7082025-11: mean 120.24 dB, σ 0.14, n=1,0922025-12: mean 120.18 dB, σ 0.16, n=2,9202026-03: mean 120.18 dB, σ 0.10, n=1,7322026-04: mean 120.37 dB, σ 0.13, n=1682026-05: mean 120.38 dB, σ 0.16, n=2,5432026-06: mean 120.16 dB, σ 0.14, n=2,3812026-07: mean 120.13 dB, σ 0.16, n=2,4562026-08: mean 119.91 dB, σ 0.13, n=1,3102023-072024-022024-052024-082024-122025-032025-062025-092025-122026-052026-08production 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 1,043.4 Hz, σ 50.8, n=5852023-12: mean 1,074.6 Hz, σ 69.7, n=2,5042024-01: mean 1,127.5 Hz, σ 59.8, n=2,6532024-02: mean 1,157.1 Hz, σ 48.4, n=2,6942024-03: mean 1,082.9 Hz, σ 67.0, n=2,2562024-04: mean 1,068.1 Hz, σ 75.4, n=1,1242024-05: mean 1,072.8 Hz, σ 48.9, n=3,8612024-06: mean 1,061.7 Hz, σ 74.0, n=3,5642024-07: mean 1,070.7 Hz, σ 55.5, n=2,3492024-08: mean 1,057.8 Hz, σ 57.3, n=2,6962024-09: mean 1,075.9 Hz, σ 50.1, n=8822024-11: mean 1,094.8 Hz, σ 73.2, n=2,9482024-12: mean 1,085.9 Hz, σ 61.0, n=2,9662025-01: mean 1,090.5 Hz, σ 56.2, n=2,1372025-02: mean 1,091.8 Hz, σ 65.0, n=2,2462025-03: mean 1,049.0 Hz, σ 69.6, n=1,9752025-04: mean 1,075.0 Hz, σ 76.0, n=9962025-05: mean 1,075.0 Hz, σ 53.8, n=2,1412025-06: mean 1,048.5 Hz, σ 65.3, n=3492025-07: mean 1,077.0 Hz, σ 51.1, n=4,5882025-08: mean 1,056.4 Hz, σ 27.7, n=2,0992025-09: mean 1,022.6 Hz, σ 44.4, n=2,7542025-10: mean 1,071.6 Hz, σ 46.1, n=2,7082025-11: mean 1,125.0 Hz, σ 68.9, n=1,0922025-12: mean 1,082.1 Hz, σ 60.7, n=2,9202026-03: mean 1,078.8 Hz, σ 41.4, n=1,7322026-04: mean 1,090.5 Hz, σ 60.4, n=1682026-05: mean 1,049.9 Hz, σ 48.1, n=2,5432026-06: mean 1,031.0 Hz, σ 51.2, n=2,3812026-07: mean 1,059.8 Hz, σ 52.1, n=2,4562026-08: mean 1,039.1 Hz, σ 37.6, n=1,3102023-072024-022024-052024-082024-122025-032025-062025-092025-122026-052026-08production 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 ±0.27 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.

951031121201281k2k5k10kfrequency, 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:

911001101191281k2k5k10kfrequency, Hz (log)production units (each thin line is one driver)golden reference sampledB

Program B — low-frequency woofer

A REDCATT-designed transducer manufactured continuously for an OEM program since 2023-08. Every figure below is computed from the individual end-of-line test record of every unit that shipped.

101,189
shipped units in this dataset
2023-08 – 2026-08
production period
14 / 61
production batches / test-station sessions
±0.21 dB
sensitivity spread (1σ) vs golden sample
98.4% of all 101,189 units measured within ±0.5 dB of the golden-referenced mean — and 100% within ±1 dB. The worst single month in 34 months of production averaged 0.34 dB from the golden sample.

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. Red dashed lines are the acceptance limits.

5,15410,30815,46220,616-1.247–-1.133 dB vs golden: 1 units-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: 56 units-0.68–-0.5667 dB vs golden: 145 units-0.5667–-0.4533 dB vs golden: 412 units-0.4533–-0.34 dB vs golden: 1,427 units-0.34–-0.2267 dB vs golden: 4,165 units-0.2267–-0.1133 dB vs golden: 10,150 units-0.1133–0 dB vs golden: 17,297 units0–0.1133 dB vs golden: 20,616 units0.1133–0.2267 dB vs golden: 19,741 units0.2267–0.34 dB vs golden: 15,352 units0.34–0.4533 dB vs golden: 8,052 units0.4533–0.5667 dB vs golden: 2,650 units0.5667–0.68 dB vs golden: 674 units0.68–0.7933 dB vs golden: 131 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 fixed acceptance window (56–76 Hz). Mean 64.1 Hz, spread ±2.5 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.

2,1814,3626,5438,72554.1–54.67 Hz: 1 units55.23–55.8 Hz: 4 units55.8–56.37 Hz: 9 units56.37–56.93 Hz: 34 units56.93–57.5 Hz: 64 units57.5–58.07 Hz: 160 units58.07–58.63 Hz: 361 units58.63–59.2 Hz: 697 units59.2–59.77 Hz: 1,207 units59.77–60.33 Hz: 2,312 units60.33–60.9 Hz: 3,712 units60.9–61.47 Hz: 5,501 units61.47–62.03 Hz: 7,194 units62.03–62.6 Hz: 8,299 units62.6–63.17 Hz: 8,652 units63.17–63.73 Hz: 8,725 units63.73–64.3 Hz: 8,644 units64.3–64.87 Hz: 8,589 units64.87–65.43 Hz: 8,127 units65.43–66 Hz: 7,413 units66–66.57 Hz: 6,266 units66.57–67.13 Hz: 4,921 units67.13–67.7 Hz: 3,462 units67.7–68.27 Hz: 2,144 units68.27–68.83 Hz: 1,363 units68.83–69.4 Hz: 910 units69.4–69.97 Hz: 653 units69.97–70.53 Hz: 526 units70.53–71.1 Hz: 347 units71.1–71.67 Hz: 319 units71.67–72.23 Hz: 212 units72.23–72.8 Hz: 159 units72.8–73.37 Hz: 104 units73.37–73.93 Hz: 51 units73.93–74.5 Hz: 21 units74.5–75.07 Hz: 12 units75.07–75.63 Hz: 9 units75.63–76.2 Hz: 5 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).

2,0994,1996,2988,3981.785–1.796 Ω: 1 units1.796–1.807 Ω: 1 units1.807–1.819 Ω: 5 units1.819–1.83 Ω: 22 units1.83–1.841 Ω: 57 units1.841–1.853 Ω: 90 units1.853–1.864 Ω: 300 units1.864–1.875 Ω: 633 units1.875–1.887 Ω: 729 units1.887–1.898 Ω: 925 units1.898–1.909 Ω: 1,214 units1.909–1.921 Ω: 1,805 units1.921–1.932 Ω: 2,627 units1.932–1.943 Ω: 3,662 units1.943–1.955 Ω: 5,952 units1.955–1.966 Ω: 7,072 units1.966–1.977 Ω: 8,131 units1.977–1.989 Ω: 8,398 units1.989–2 Ω: 7,991 units2–2.011 Ω: 7,830 units2.011–2.023 Ω: 7,598 units2.023–2.034 Ω: 6,433 units2.034–2.045 Ω: 4,835 units2.045–2.057 Ω: 3,547 units2.057–2.068 Ω: 2,405 units2.068–2.079 Ω: 1,592 units2.079–2.091 Ω: 931 units2.091–2.102 Ω: 700 units2.102–2.113 Ω: 587 units2.113–2.125 Ω: 824 units2.125–2.136 Ω: 1,096 units2.136–2.147 Ω: 927 units2.147–2.159 Ω: 848 units2.159–2.17 Ω: 823 units2.17–2.181 Ω: 986 units2.181–2.193 Ω: 1,346 units2.193–2.204 Ω: 1,298 units2.204–2.215 Ω: 1,319 units2.215–2.227 Ω: 1,377 units2.227–2.238 Ω: 1,417 units2.238–2.249 Ω: 1,117 units2.249–2.261 Ω: 669 units2.261–2.272 Ω: 404 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 0.92 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.

117.5118.0118.4118.9119.32023-08: mean 118.07 dB, σ 0.18, n=2,4722023-09: mean 117.98 dB, σ 0.15, n=2,0582023-10: mean 118.11 dB, σ 0.13, n=3,5112023-12: mean 118.14 dB, σ 0.15, n=6,0892024-01: mean 118.09 dB, σ 0.12, n=1,4492024-02: mean 118.44 dB, σ 0.21, n=1,5072024-03: mean 118.28 dB, σ 0.18, n=2,9442024-04: mean 118.36 dB, σ 0.17, n=3,0452024-05: mean 118.66 dB, σ 0.24, n=4,7612024-06: mean 118.35 dB, σ 0.23, n=3,3362024-07: mean 118.00 dB, σ 0.15, n=2,5172024-08: mean 118.15 dB, σ 0.18, n=2,3712024-09: mean 118.35 dB, σ 0.15, n=3,1612024-10: mean 118.30 dB, σ 0.13, n=2,2922024-12: mean 118.37 dB, σ 0.15, n=2,8892025-01: mean 118.05 dB, σ 0.16, n=1,8892025-03: mean 118.64 dB, σ 0.28, n=2,9182025-04: mean 118.86 dB, σ 0.28, n=1,4042025-05: mean 118.34 dB, σ 0.15, n=3,3632025-06: mean 118.62 dB, σ 0.15, n=2,6622025-07: mean 118.35 dB, σ 0.12, n=1,8392025-08: mean 118.38 dB, σ 0.11, n=3,5322025-09: mean 118.51 dB, σ 0.13, n=2,1192025-10: mean 118.33 dB, σ 0.17, n=8422025-11: mean 118.24 dB, σ 0.18, n=3,2312025-12: mean 118.60 dB, σ 0.13, n=1,0312026-01: mean 118.57 dB, σ 0.18, n=4,4282026-02: mean 118.37 dB, σ 0.14, n=8852026-03: mean 118.40 dB, σ 0.18, n=4,1112026-04: mean 118.20 dB, σ 0.15, n=3,2792026-05: mean 118.33 dB, σ 0.17, n=4,9392026-06: mean 118.15 dB, σ 0.24, n=1,9302026-07: mean 118.15 dB, σ 0.16, n=4,6442026-08: mean 117.94 dB, σ 0.22, n=7,7362023-082024-012024-052024-092025-032025-072025-112026-032026-07production 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 1.49, n=2,4722023-09: mean 62.71 Hz, σ 1.39, n=2,0582023-10: mean 63.32 Hz, σ 1.24, n=3,5112023-12: mean 62.13 Hz, σ 1.82, n=6,0892024-01: mean 64.47 Hz, σ 3.95, n=1,4492024-02: mean 64.60 Hz, σ 1.64, n=1,5072024-03: mean 61.17 Hz, σ 2.05, n=2,9442024-04: mean 62.73 Hz, σ 1.97, n=3,0452024-05: mean 64.67 Hz, σ 2.36, n=4,7612024-06: mean 63.81 Hz, σ 2.22, n=3,3362024-07: mean 65.86 Hz, σ 1.71, n=2,5172024-08: mean 63.64 Hz, σ 1.66, n=2,3712024-09: mean 63.99 Hz, σ 1.99, n=3,1612024-10: mean 63.21 Hz, σ 1.31, n=2,2922024-12: mean 66.21 Hz, σ 1.71, n=2,8892025-01: mean 65.71 Hz, σ 1.47, n=1,8892025-03: mean 65.07 Hz, σ 1.28, n=2,9182025-04: mean 63.28 Hz, σ 1.52, n=1,4042025-05: mean 63.26 Hz, σ 1.75, n=3,3632025-06: mean 62.06 Hz, σ 1.78, n=2,6622025-07: mean 60.77 Hz, σ 1.24, n=1,8392025-08: mean 61.68 Hz, σ 1.13, n=3,5322025-09: mean 62.70 Hz, σ 1.38, n=2,1192025-10: mean 64.04 Hz, σ 1.23, n=8422025-11: mean 63.46 Hz, σ 2.03, n=3,2312025-12: mean 65.85 Hz, σ 1.50, n=1,0312026-01: mean 68.86 Hz, σ 2.04, n=4,4282026-02: mean 66.07 Hz, σ 2.28, n=8852026-03: mean 65.86 Hz, σ 1.31, n=4,1112026-04: mean 64.53 Hz, σ 1.09, n=3,2792026-05: mean 63.50 Hz, σ 1.04, n=4,9392026-06: mean 65.85 Hz, σ 0.99, n=1,9302026-07: mean 65.83 Hz, σ 1.31, n=4,6442026-08: mean 64.64 Hz, σ 2.03, n=7,7362023-082024-012024-052024-092025-032025-072025-112026-032026-07production 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 — which is why the red reference line in the monthly charts is itself flat.
Why show only units that passed?
Because that is the population a customer receives. Units failing any check are pulled from the flow for rework or scrap and are not part of shipped product. (Their records exist too — the test station keeps everything — but mixing retests and rework loops 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. 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.