Using a sledgehammer to crack a nut? Why we calibrate a budget ECM8000 on a €50,000 reference chain.
When you open the original PDF calibration certificates of our ECM8000 microphones, the Audio Precision (APx555) logo immediately catches your eye. If you are an audio engineer or experienced acoustician yourself, you will rightly ask: Why would anyone measure a basic electret capsule with nearly 30 dB(A) self-noise on the world's most expensive and precise audio analyzer—and even let customers pick individual serial number curves before buying, when REW or Akulap mathematically compensates the frequency response via the calibration file anyway?
The honest answer is: Because our APx555 and Class-1 reference chain are already powered on every day on our lab bench for our own R&D work—and because uncompromising measurement engineering is what we love.
What pre-purchase curve selection actually gives you (and what it doesn't):
1. Mathematical Compensation vs. Physics
As soon as you load our supplied .cal file into REW, Akulap, or WinAudioMLS, any on-axis frequency response deviation is mathematically compensated. For standard room acoustics measurements, our regularly calibrated ECM8000 is completely sufficient.
2. No "Russian Roulette" with Capsule Quality
Anyone looking at our real CSV curves in the selector immediately sees how widely modern production batches vary. By selecting your curve upfront, you 100% eliminate "Monday morning lemons" (e.g., severe low-end roll-off) before buying.
3. Use Without a Calibration File
If you use the measurement microphone on a digital mixing console, hardware DSP, or live PA rig that cannot import .cal correction files, a factory-linear "Golden Sample" (Grade A) is worth its weight in gold.
Complete Signal Flow: Our Simultaneous 2-Channel Calibration Chain per IEC 61094-5
Instead of measuring the reference and the DUT sequentially in an open room (error-prone substitution method), our test bench forms a closed, simultaneous two-channel real-time loop. Click any station to open its dedicated deep-dive dossier:
| Signal Chain Stage | Hardware Component | Role in Test Setup | Key Technical Specs | Your Practical Benefit |
|---|---|---|---|---|
| 01. Generator & Dual Analyzer | Audio Precision APx555 → | Generates the ultra-pure stimulus signal and captures Reference (Ch A) and DUT (Ch B) phase-synchronously in real time. | -150 dB THD+N, 1 MHz bandwidth, 2 parallel ADCs, APx AutoCal | Zero electrical measurement error: No soundcard inaccuracies, 100% reproducible PDF test certificates. |
| 02. Acoustic Coupler | Spectra SQ-4.2 Pressure Chamber → | Completely isolates room acoustics and couples both 1/2" microphone heads simultaneously to the exact same symmetric pressure field. | IEC 61094-5 compliant, 31.5 Hz – 20 kHz, 94 to 134 dB SPL, < 3% THD | Over 60 dB SNR margin: Completely immune to room reflections, comb filtering, or ambient lab noise. |
| 03. Reference Standard (Ch A) | G.R.A.S. 40AE 1/2" → | Provides the incorruptible acoustic ground truth inside the chamber throughout the entire sweep as a real-time reference. | Traceable Class-1 standard (IEC 61094-4), exact 54.94 mV/Pa, metal diaphragm | Zero drift from swapping mics: Temperature, barometric pressure, or driver fluctuations cancel out (B minus A). |
| 04. Acoustic Calibrator | Brüel & Kjær 4231 → | Provides the PTB/DAkkS-traceable acoustic sound pressure reference to verify absolute chain gain prior to measurement. | IEC 60942 Class 1, exact 94.0 dB SPL (1 Pa) ± 0.2 dB @ 1,000 Hz | True absolute sensitivity (mV/Pa & dBV offset) for accurate SPL measurements in Akulap & REW. |
| 05. Device Under Test / DUT (Ch B) | Behringer ECM8000 → | Thanks to its 12.7 mm (1/2") outer body, it fits without any reduction adapter mechanically and acoustically symmetrically opposite the G.R.A.S. 40AE. | 1/4" capsule in 1/2" body, ~28–30 dB(A) self-noise, 100 frequency points | Individual .cal file & selection: Turns a widely varying mass-market mic into a predictable measurement tool. |
Honest Engineering Verdict: Can a calibrated ECM8000 replace a €2,000 Class-1 reference microphone?
A clear no. Online forums often perpetuate the myth that a cheap electret microphone becomes identical to a high-end reference microphone once calibrated. As a measurement laboratory that works daily with €2,000-class Class-1 reference chains for official acoustic expert reports, ISO/IEC standard compliance (IEC 61672 Class 1), and industrial R&D, we draw a clear physical line here. A calibration file only corrects the linear on-axis amplitude frequency response at the time of testing:
| Physical Parameter | Calibrated Behringer ECM8000 | Class-1 Reference System (~€2,000) |
|---|---|---|
| Self-Noise (Noise Floor) | approx. 28–30 dB(A) – blind in quiet rooms or low-level noise assessments. | 6.5 to 15 dB(A) – resolves the finest acoustic details down below the threshold of human hearing. |
| Max SPL & Distortion (THD) | Capsule and internal FET circuit distort early at high sound pressure levels. | Distortion-free up to >140 dB SPL (essential for near-field speaker, PA, or industrial testing). |
| Temperature & Long-Term Stability | Polymer diaphragm reacts to temperature, humidity, and aging over time. | Metal diaphragm (e.g., titanium/nickel), artificially aged, drift-free and calibration-stable for years. |
| Off-Axis Directivity | Combining a 1/4" capsule with a wider 1/2" housing body causes noticeable edge diffraction and beaming above ~5 kHz. | Precision-machined free-field or diffuse-field geometry with strictly standardized omnidirectional polar response. |
Practical Decision Guide: When is the ECM8000 enough—and when do you need Class 1?
| Your Intended Application | Calibrated ECM8000 | Class-1 Reference Chain (~€2,000) | Why the Difference Matters |
|---|---|---|---|
| Home Theater, Studio Tuning & Subwoofer (REW / Akulap) | ✅ Ideal Choice | Overkill | At normal test levels (75–90 dB SPL), our .cal file mathematically compensates the on-axis response with complete accuracy. |
| Live PA, Digital Consoles & DSP without .cal Import | ✅ Selected "Golden Sample" (Grade A) | Optional | By picking the flattest serial number upfront in our curve selector, you measure linearly even without software correction. |
| Quiet Noise Floor Analysis (< 35 dB SPL) & Ultra-Low-Noise | ❌ Unsuitable (~30 dB(A) self-noise) | ✅ Strictly Required (6.5–15 dB(A)) | The electret capsule's own thermal noise masks quiet acoustic sources—no calibration file can fix a buried signal. |
| Legal Acoustic Reports, DIN/ISO Testing & Industry | ❌ Not Permitted | ✅ Mandatory Standard (IEC 61672 Class 1) | Requires long-term stable metal diaphragms, certified polar response, >140 dB SPL handling, and traceable metrological compliance. |
Standard Included Report (€0) vs. Signed Factory Calibration Certificate (+€50)
The physical measurement on our Audio Precision APx555 is 100% identical for every microphone leaving our lab—there is no two-tier measurement accuracy! With the €50.00 upgrade, you receive the formal, personally signed test and quality management document for your records (e.g., ISO 9001 audits, test equipment monitoring, or client verification).
| Aspect | Standard Delivery (€0 Surcharge) | Signed Factory Calibration Certificate (+€50 Upgrade) |
|---|---|---|
| Acoustic Measurement | Simultaneous 2-channel measurement (APx555 + Spectra SQ-4.2 + G.R.A.S. 40AE) | Exact same measurement—no two-tier metrology! |
| Digital Calibration Data | .cal / .txt file + digital APx555 measurement report (PDF) | .cal / .txt file + digital APx555 report + printed original |
| Signed Declaration of Conformity | ❌ No | ✅ Yes, personally signed by Dr.-Ing. Frank Jordan confirming compliance with DIN EN / IEC 61672-1 tolerance limits |
| Documented Traceability Proof | ❌ No | ✅ Yes, complete documentation of the PTB/DAkkS-traceable reference chain (G.R.A.S. 40AE, B&K 4231, APx555) for ISO 9001 audits |
| Legal Status (Lab vs. Accredited Body) | Factory measurement | ISO-compliant factory calibration certificate (not an ISO/IEC 17025 accredited calibration body, yet metrologically superior to many standard test benches thanks to our €50,000+ APx555 setup) |
Original Certificates of our Lab Reference Chain (Live Access)
Unbroken documentation of our primary standard B&K 4231 (DAkkS-calibrated at SPEKTRA Dresden on 2026-11-04) and our official statement of metrological traceability for your ISO 9001 audits.