Ohmic Audio

🔧 INSTALLER LEVEL: Advanced Integration Strategies

Multi-Source Switching and Priority

Professional installations handle multiple sources gracefully, not awkwardly.

Signal priority hierarchy:

For most driver workflows, priority should be:

  1. Phone call (HFP) — always highest priority
  2. Navigation audio (CarPlay / AA)
  3. Streaming audio (CarPlay / AA)
  4. Physical media (USB)
  5. Radio
Flowchart showing source priority in a car system with phone calls at the top, then navigation prompts, streaming audio, USB media, and radio, plus notes about ducking and resume behavior.
Good source switching feels invisible. Calls should always win, navigation should duck lower-priority audio instead of clobbering it, and the system should cleanly restore the previous source when the interrupt ends.

Head units with automatic ducking will reduce music volume when navigation speaks, then restore. Lesser units just switch — music stops, navigation plays, silence, music resumes. If your head unit does this, consider a DSP with audio mixing capability to blend navigation audio over music instead.

Simultaneous audio mixing:

Some DSPs (miniDSP, AudioControl) have multiple stereo inputs with mixing. Connect: - Input 1: Head unit preamp (music) - Input 2: Navigation/alert audio from phone - Output: Sum with navigation at -10 dB relative to music

Result: Music plays; navigation announcement mixes in at reduced level; music never stops. This is the professional approach.

USB Audio Quality

USB audio from phone to head unit is often the best wired connection quality, but it's misunderstood.

What USB actually transmits:

When you plug in via USB, the head unit requests the phone's digital audio stream directly. No DAC on the phone — digital audio transfers to the head unit's DAC.

Quality depends on: - Head unit's internal DAC quality - Head unit's power supply noise (affects DAC) - USB cable quality (shielding matters for longer runs) - Audio format of the file on the phone

Audio formats and quality:

Format Type Quality Head Unit Support
MP3 Lossy 128–320 kbps Universal
AAC (.m4a) Lossy 128–256 kbps Near-universal
FLAC Lossless CD or better Most quality head units
ALAC (.m4a) Lossless (Apple) CD or better Apple-focused units
WAV Uncompressed CD quality Wide support
DSD (.dsf) High-res 1-bit, high rate Few units support
MQA Lossy/lossless Tidal Masters Rare in car audio

Practical recommendation:

For most listeners: AAC at 256 kbps or MP3 at 320 kbps is indistinguishable from lossless in a car environment. Buy a premium Tidal or Apple Music subscription for lossless if you have excellent hearing in an exceptional car audio environment; otherwise 256 kbps AAC is sufficient.

For high-end SQ builds: FLAC stored on USB drive, played through premium head unit. Avoids any streaming compression.

Streaming Services: Audio Quality Comparison

Comparison board showing common music services by practical in-car quality tier, codec path, offline support, and best-fit use case rather than fake precision scores.
Use the service chart as a system-planning aid. In higher-end installs, the useful question is not just “which app is best,” but whether the transport path and head unit can actually preserve the benefit you are paying for.
Service Max Quality Codec Car Notes
Spotify Free 128 kbps Ogg Vorbis Not recommended
Spotify Premium 320 kbps Ogg Vorbis Adequate
Apple Music 256 kbps AAC + Lossless AAC / ALAC Excellent for iPhone
Tidal HiFi 1411 kbps FLAC Best lossless streaming
Tidal HiFi Plus 9216 kbps MQA MQA Overkill for most
Amazon Music HD 850–3730 kbps FLAC Excellent
YouTube Music 256 kbps AAC Good

In car audio context:

Lossless streaming (Tidal, Apple Lossless) is genuinely worth having if you have a high-quality system. The difference between Spotify 320 kbps and Tidal FLAC is subtle on most systems but audible on a well-tuned 3-way active system in a quiet environment.

Tidal via CarPlay or Android Auto does pass lossless audio through — it's not re-encoded at the phone. The bottleneck is the head unit's DAC.