1Take Support
Support page for 1Take - Audio Recording App for Musicians
Introduction
I’m the developer of 1Take. I’ve been discussing the “output side” of audio—compressors, LUFS metering—but today I’m cutting into the biggest black box of all: the iPhone’s built-in microphone.
“Why does every iPhone recording sound different?” “Why does Apple claim flat response, yet in practice the highs feel rolled off and lows unnaturally cut?” I’m sharing the technical battle record: the specs Apple hides behind their documentation, the “maze” of mic placement that varies by model, and how 1Take tuned these into “musical instruments.”
1. Apple’s “Flat” Claim vs. Physical Reality
Apple’s developer documentation proudly states that iPhone microphones provide “extremely flat and high-fidelity response.”
“iPhone microphones are designed to provide a flat frequency response…”
But when engineers actually measure them, clear signs of intentional processing appear.
Mystery 1: The “Void” Below 100Hz
iPhone microphones have a powerful high-pass filter (HPF) constantly running at the OS level to eliminate chassis vibration (handling noise) and wind noise. This is the real reason “iPhone recordings sound thin.”
Mystery 2: Processing in the Presence Region
To improve voice call clarity, you may notice phase irregularities around 4kHz-8kHz. This is a side effect of beamforming (directional control) from the multi-function microphone array.
1Take bypasses these through “Measurement Mode,” extracting Apple’s true “raw characteristics” as much as possible.
2. Breaking Free from AGC: The “Meddling” Auto Gain Control
Why doesn’t iPhone have a standard “Input Trim” (sensitivity adjustment)? Because iOS assumes AGC (Auto Gain Control)—automatic adjustment that makes recordings “sound decent regardless of who’s recording.”
For musicians, AGC is the natural enemy that destroys dynamics. It forcibly boosts quiet sounds, increasing noise, and unnaturally clamps loud sounds. Without killing this “gain that moves on its own,” simulating 1176 or LA-2A compression is impossible.
1Take’s Custom Input Trim Implementation
1Take built its own gain stage using internal floating-point arithmetic (Float32), bypassing the OS’s gain adjustment entirely.
We catch the raw signal at the very top of AVAudioEngine and scale it in real-time using vDSP (SIMD-optimized). This enables us to precisely deliver the energy captured by the microphone to the sweet spot where compressors respond most “musically.”
3. The Maze of Mic Placement Across Models
The most frustrating aspect of iPhone development is that the physical mic placement and “which one is the main mic” varies completely between models (Pro / Max / standard) and generations.
The Pro Max “Flip” Problem
Particularly tricky is the behavior when holding the iPhone horizontally (landscape).
Normal video recording: Stereo image swaps according to screen orientation.
1Take’s approach: 1Take constantly monitors the accelerometer and AVAudioSession port information. Whether you rotate iPhone Pro Max left or right, we automatically determine whether to “always use the bottom mic (Lightning/USB-C port side) as the primary axis” or “correctly phase-invert L/R for stereo recording consistency.”
If this were an Android app… I shudder to think. Android devices have wildly varying mic counts, performance, and characteristics per model. Guaranteeing this level of “instrument-grade precision” would likely exceed what a solo developer could handle. It’s precisely because iOS is a “closed universe” that 1Take can control microphones this rigorously.
4. How Input Trim Changes “Music”
“Just boost it after recording” is digital thinking. An engineer’s thinking is: “How hard do I drive the compressor?”
Turning 1Take’s Trim knob is equivalent to raising the input gain on a tube amp.
- Studio (LA-2A style): Push in low for relaxed, gentle leveling.
- Studio+ (1176 style): Push in high to bring out FET’s aggressive saturation.
Deciding this “drive level” yourself before performing—this process is what transforms your iPhone from a “smartphone” into a “recording console.”
Conclusion: Turning the Black Box into Your Partner
The iPhone microphone is an extremely capable “instrument” wrapped in a curtain called the OS.
1Take tears off that curtain and returns the Input Trim handle to you. So you can truly believe in “flat characteristics.” So you can focus purely on “sound” without worrying about model differences.
On your next recording, feel the “weight” transmitted through your fingertips on the Trim knob. Beyond it awaits a world of crystal clarity that Voice Memos could never reach.