Car Audio Explained, Part 19: Glossary and Where His Material Lives (Andy Wehmeyer's Lessons)

4 days ago

26 min read

This is Part 19 of 19 in the series Andy Wehmeyer on Car Audio, Explained for Beginners. Start here · Download the full guide as a PDF

Unofficial guide. Andy Wehmeyer's points are paraphrased from his public forum posts, blog, tuning guides, videos and podcasts, with a link to each source; the plain-English explanations were written for this guide. Not written, reviewed or endorsed by Andy Wehmeyer or Audiofrog.

Glossary

Plain-English definitions of terms used in this guide. The definitions are general background written by the compiler. Where Andy Wehmeyer uses a term in a particular way, a note marked How Andy uses it says so, with a reference to the point where you can read his full view and its sources.

A-pillar: the post on each side of the windshield. Speakers are often mounted in pods there to raise the sound. How Andy uses it: he calls it "a HORRIBLE place for a midrange", though his company's own sales copy promotes an A-pillar system (1.6 #6).

A/D converter (analog-to-digital converter): the part of a DSP that turns the incoming electrical music signal into numbers. If the incoming signal is too strong, it clips. How Andy uses it: he says the DSP's input-sensitivity control has "ONE function": keeping the A/D converter from clipping at maximum volume (4.8 #1).

Acoustic crossover: the point where two speakers actually hand over in the air, as measured with a microphone. It depends on both the crossover filter and the speakers' own responses, so it is often not at the frequency set on the DSP. How Andy uses it: turning the sub up moves the acoustic crossover up and out of phase, which is why he lowers the sub's low-pass as he raises its level (4.2 #6).

Acoustic reciprocity: the principle that a sound path works the same in both directions, so a speaker and a microphone can swap places. How Andy uses it: he "maps" a car by putting a speaker at the driver's head and a microphone at each possible speaker location; this works for sub, midbass and midrange spots, not tweeters (2.3 #13).

Active crossover (active system): a crossover that works on the signal before the amplifiers, usually inside a DSP, with a separate amplifier channel for each speaker. Every setting can be adjusted.

All-pass filter: a filter that shifts the timing (phase) of sound in one frequency band without changing its loudness. How Andy uses it: he describes an all-pass near 250 Hz as a way to improve the image in both front seats at once, where delay helps one seat and hurts the other (1.9 #4, 1.9 #7). He also says some factory systems use all-pass filters in place of delay, and that you should not add delays on top of them (4.14 #2, 4.14 #4).

Amplifier (amp): the unit that makes the music signal strong enough to drive speakers. Its output is rated in watts.

Baffle: the flat panel a speaker is mounted on, which keeps the sound from the front of the cone apart from the sound off its back. How Andy uses it: he says a door midbass needs a sealed baffle, not a box (2.1 #1).

Balance control: the control that shifts sound between the left and right speakers. How Andy uses it: panning it fully left, then fully right, shows the real edges of the stage (1.7 #1).

Bandwidth: the range of frequencies a speaker, filter or system covers.

Biquad: a standard building block of digital filters; one biquad can make one EQ band or one section of a crossover.

Boundary microphone: a microphone mounted flush with a surface, so it does not pick up a reflection from that surface. Andy describes using a 3D-printed one for mapping speaker locations (2.3 #13).

Break-in: the idea that new speakers change as they are played. How Andy uses it: he says the real change is resin in the spider cracking, which matters mainly for subwoofers; mids and tweeters crossed above resonance barely change (5.1 #30).

Cabin gain: the boost a closed car gives to deep bass, rising as frequency falls. How Andy uses it: he calls it the car's "transfer function" (in-car response divided by the woofer's outdoor response) and says it belongs to the car, not the woofer; build the most efficient box you can fit, then EQ (4.1 #1, 4.1 #6).

Center channel (center speaker): a speaker in the middle of the dash meant to anchor centered sounds such as vocals. How Andy uses it: "L+R is not a center"; a real center plays only what left and right share, extracted by an upmixer (1.10 #1, 1.10 #2).

Channel separation: how little of one channel leaks into the other inside a piece of equipment, in dB. How Andy uses it: he says it makes no difference to imaging in a car: at 60 dB of separation, 1 W leaks only a millionth of a watt into the other channel, while each ear already hears the opposite speaker at maybe −6 dB (5.1 #24).

Class-D amplifier: an efficient type of amplifier that switches its output on and off very rapidly; most modern car amps are class-D.

Clipping: what happens when any part of the system is asked for more than it can give: the tops of the sound waves are cut off flat. How Andy uses it: he says clipping, not too little power, is what destroys tweeters, and that DSP and head-unit clipping is the usual culprit (5.1 #26, 4.7 #6).

Coax: short for coaxial cable, a signal cable with one central conductor inside a surrounding shield; also short for a coaxial speaker, with a tweeter mounted in the middle of a woofer. How Andy uses it: he says coax cable suits single-ended amp inputs, and twisted pair suits differential ones (4.10 #5).

Codec: the method used to compress and decompress digital audio for streaming or storage.

Comb filter: a pattern of closely spaced peaks and dips caused when the same sound arrives at two slightly different times (from two speakers, or a speaker and its reflection). On a graph it looks like the teeth of a comb. How Andy uses it: he says "width" from delay tricks is really comb filtering, and that no EQ or delay can fix a reflection's comb (1.7 #2, 1.3 #4).

Cone: the moving part of a woofer or midrange that pushes the air.

Correlated and uncorrelated noise: test noise that is identical in both channels (correlated, also called mono) or different in each channel (uncorrelated). How Andy uses it: he reads phase from mono (correlated) pink noise; his later view is that uncorrelated noise is useless except for upmixers, L−R rears or gaming an RTA (3.8 #7, 3.3 #4).

Cross-car mode: a bass cancellation caused by sound reflecting off the far side of the car. How Andy uses it: he links a 60–80 Hz dip in one midbass to it and says to cross above it to the sub rather than EQ it; he describes every car having one near 70 Hz (4.6 #1).

Crossfiring: aiming each speaker across the car toward the opposite seat. How Andy uses it: he calls crossfired pillar tweeters a "band-aid" (1.5 #6).

Crossover: a filter that splits the music between speakers so each plays only the range it handles well. The "crossover frequency" is where one speaker hands over to the next.

D/A converter (DAC): the part of a DSP that turns numbers back into an electrical signal for the amplifiers. Its output cannot go above 0 dBFS.

Damping factor: a specification describing how firmly an amplifier controls a speaker's motion. How Andy uses it: he says anything above about 10 is enough; a damping factor of 1000 moves Qts only from 0.707 to 0.708 (5.1 #19).

Dash: the dashboard. Many factory systems have speakers in the dash top.

DATS: a commercial test kit for measuring a speaker's impedance and Thiele/Small parameters.

dB (decibel): the unit for differences in level. About 3 dB is clearly noticeable, 6 dB is a big change, and about 10 dB sounds roughly twice as loud. Each 3 dB more output needs about twice the amplifier power.

dB/oct (decibels per octave): the steepness of a filter: how quickly it turns sound down outside its range. A 24 dB/oct filter turns sound down by 24 dB for each octave beyond its corner.

dBFS (decibels relative to full scale): a level in the digital domain, where 0 dBFS is the largest possible digital signal. Anything that would go above it clips.

Deadening (sound deadener): heavy, sticky damping sheets and foam applied to car panels; Dynamat is one brand. How Andy uses it: he uses it to stop rattles and panel movement, done in order: the door trim panel first, then the inner skin (2.2 #1).

Delay (time alignment): holding back one speaker's sound by a few thousandths of a second so it arrives at the listener with the others. How Andy uses it: "Delay doesn't move speakers"; he sets delay from tape-measured distances and centers the image with level, not delay (3.9 #1, 3.9 #3, 3.10 #2).

Differential input: an amplifier input that measures the difference between two signal wires, which helps reject noise. How Andy uses it: he identifies it by measuring hundreds of ohms between the RCA shield and the amp's power ground, and pairs it with twisted-pair cable (4.10 #5).

Directivity: how a speaker's sound output changes with direction: how much it "beams" forward instead of spreading out.

Dispersion: how widely a speaker spreads its sound. How Andy uses it: his rule compares the driver's circumference with the wavelength; below 1 the sound is the same on- and off-axis (1.4 #2).

Distortion: anything added to the sound that was not in the original signal, such as harshness from clipping or buzzes from rattles. How Andy uses it: he says distortion and rattles, not arrival time, give away where bass is coming from (4.2 #2).

DIYMA: DIYMobileAudio, an online car-audio forum where many of his posts appear, under accounts the forum renamed "14642" and "156546".

Driver: a single speaker unit (tweeter, midrange, woofer or subwoofer).

DSP (digital signal processor): a small computer for sound that provides EQ, crossovers, delay and level control for each speaker channel.

DSP amplifier: an amplifier with a DSP built in. How Andy uses it: he says it has no analog gain after its D/A converter, so output lost to EQ cuts cannot be won back (4.8 #9).

Dust cap: the dome in the middle of a woofer's cone. Andy measures delay distances to the center of each dust cap or grille (3.9 #3).

Enclosure: a speaker box. How Andy uses it: he says a pod is an enclosure too, and must be treated as one (2.4 #1).

EQ (equalization): turning particular frequency bands up or down to correct a system's tonal balance.

Excursion: how far a speaker's cone moves in and out. More excursion means more strain and, past a point, more distortion.

F3: the frequency where a speaker's (or box's) bass output has fallen 3 dB. How Andy uses it: he says matching a sub's F3 to the car is "a ridiculous crapshoot" (4.1 #6).

Factory system (OEM system): the audio system a car is built with; OEM means "original equipment manufacturer". Many include their own processing.

Far-side bias: the sound image being pulled toward the speaker on the far side of the car. How Andy uses it: he names it as a result of the off-axis "hole" a big woofer and a small tweeter leave at their crossover in door locations, and says a 3-way reduces it (1.4 #4).

Fc: a speaker's resonance once it is mounted in a sealed box (higher than its Fs).

FFT: Fast Fourier Transform, the math that turns a recorded signal into a frequency graph. Measurement software lets you choose its size (for example 16384 or 32k).

FIR filter: "finite impulse response", a type of digital filter that can change timing and level very precisely but adds processing delay (latency).

Frequency response: a graph or description of how loud a speaker or system plays at each frequency.

Fs: a speaker's free-air resonance, the frequency at which its cone naturally moves most easily. Below it, the speaker works less well and distorts more.

Gain: an amplifier's input control. It matches the amp to the strength of the incoming signal; it does not set power. How Andy uses it: his gain procedure uses a sine wave on the sub amp only and sets the rest by pink noise and RTA (4.8 #4).

Gasket: a soft seal between a speaker and the surface it mounts to, to stop air leaks and rattles.

Ground loop: noise caused by equipment sharing ground connections at different voltages. How Andy uses it: ground loops cause whine, not hiss (4.10 #1).

Group delay: how much a filter or speaker delays different frequencies. How Andy uses it: he calls group delay "less a curse than people think" and says it is overrated in cars.

Haas effect (precedence effect): when the same sound arrives twice close together, we hear a single sound located at the first arrival. How Andy uses it: he says car reflections arrive too early to be heard as echoes, so instead they spread the image and change the tone (5.7 #16).

"Harman curve": a popular target curve for car audio tuning, named after the company Harman. How Andy uses it: he says it began as his own installer curve, which he brought to Harman, where it became the MS-8 curve (3.5 #2).

Harmonics: extra tones at whole-number multiples of a note's frequency (twice, three times…). Distortion adds harmonics. How Andy uses it: his test adds 2nd and 3rd harmonics to a bass track to show that distortion makes bass easy to locate (4.2 #2).

Head unit: the radio or main audio unit in the dash, also called the source.

High-pass filter: a filter that lets frequencies above a chosen point through and turns lower ones down. It keeps deep bass out of small speakers.

Hiss and whine: hiss is a steady "shhh" noise; whine is a pitched noise that often rises and falls with engine speed. How Andy uses it: "Hiss is not a ground loop; loops whine" (4.10 #1).

Hz and kHz: hertz, cycles per second, the unit of frequency (pitch). A kilohertz (kHz) is 1,000 Hz. Hearing spans roughly 20 Hz to 20 kHz.

Imaging: the illusion that each voice or instrument sits at a precise spot in front of you. How Andy uses it: he suggests learning what it is with any matched cheap pair of speakers (5.7 #5).

Impedance: a speaker's electrical resistance to the amplifier's signal, measured in ohms; it varies with frequency.

Impedance sweep: a measurement of impedance across frequency. How Andy uses it: he uses one to check a pod, where a leak shows up as an extra, port-like resonance (2.4 #4).

Impulse response: a measurement of how a system responds over time to a very short click. How Andy uses it: he says its peaks are not true arrival times for subs and midbass, so a tape measure is usually better (3.9 #5).

Inductance: the electrical property of a speaker's voice coil that resists fast changes in current; it affects how a speaker behaves at higher frequencies.

Infinite baffle (IB): mounting a speaker on a large panel with no sealed box behind it, so a large space (such as a trunk or door) acts as its box. "IB-type" drivers are designed for this.

Inverted triangle: How Andy uses it: his picture of stage width, with you at the bottom point and the speakers at the two upper corners; the stage can't be wider than the speakers (1.7 #1).

Kick panel: the panel at the side of the front footwell, a common place for midbass or midrange speakers.

L+R and L−R: the sum of the left and right channels (what they share, mono) and the difference between them (what differs). How Andy uses it: L+R alone is not a center (1.10 #1); his later view is that L−R rear fill sounds "phasy" (1.11 #5).

Latency: the delay processing adds between the input and the output. Long FIR filters add enough to affect hands-free calls.

Level: how loud a channel or speaker is set relative to the others. How Andy uses it: he centers an off-center image with level, never delay (3.10 #2).

LOC (line output converter): a device that turns a speaker-level signal (for example from a factory radio) into a lower, RCA-level signal for an amplifier or DSP.

Logic 7: Harman's processing that spreads stereo across many speakers, used in some factory systems. How Andy uses it: "DO NOT TRY TO SUM" a Logic 7-type car back together (4.15 #4).

Low shelf: an EQ filter that raises or lowers everything below a chosen frequency by a set amount. How Andy uses it: he builds his target's bass lift as a 12 dB/octave low shelf at about 60 Hz (3.5 #1).

Low-pass filter: a filter that lets frequencies below a chosen point through and turns higher ones down. Subwoofers use one.

LR4 (Linkwitz-Riley, 4th order): a common crossover filter type with a 24 dB per octave slope. How Andy uses it: his default sub/midbass crossover is 60 Hz on the sub and 80 Hz on the midbass, both LR4 (4.2 #6).

Matrix: a simple circuit that mixes left and right into sum (L+R) and difference (L−R) signals. How Andy uses it: he says passive L+R/L−R matrices "do not work" for a center (1.10 #1), and he later judged matrix upmixers poor for music (1.12 #6).

Microfarad (µF): the unit used for capacitor size. A series capacitor blocks low frequencies; a smaller value blocks more.

Midbass: the upper-bass and lower-middle range, roughly 80–300 Hz, and the speaker (usually a 6–8 inch woofer in the door) that plays it.

Middler: How Andy uses it: his name for a factory dash speaker aimed at the windshield, which carmakers use as a "poor man's tweeter"; with raked glass its highs reflect to every seat, but it fails with upright glass, as in a Jeep (1.6 #9, 2.3 #9). His praise of it sits beside his criticism of firing mids up at the glass; the conflicts list in "Start here" sets out both (1.6 #23).

Midrange: the middle frequencies, where most of the human voice sits, and the small speaker (about 2–4 inches) that plays them.

Minimum phase: a type of response in which level and timing are tied together, so correcting the level with EQ also corrects the timing. How Andy uses it: box and driver peaks are minimum phase and respond to EQ; reflection dips do not (3.6 #10).

Mono: the same signal in both channels.

MS-8: the JBL MS-8, a car-audio processor with automatic multi-microphone tuning, made by Harman. Andy was its product manager.

Near-field: listening or measuring close to a speaker, where its direct sound dominates the room's reflections. Studio monitors are near-field speakers.

Null: a deep dip in the response where two sounds cancel. How Andy uses it: never significantly boost one with EQ (3.6 #9).

Octave: a doubling of frequency, such as 100 to 200 Hz.

Off-axis and on-axis: on-axis is straight in front of a speaker; off-axis is anywhere to the side, above or below.

Ohm (Ω): the unit of electrical resistance and impedance. Car speakers are commonly 2 or 4 ohms.

Omnidirectional: radiating sound equally in all directions. Speakers are omnidirectional at frequencies whose wavelength is large compared with the driver.

Parametric EQ: an equalizer in which you set each band's center frequency, its boost or cut, and its width (Q).

Passband: the range of frequencies a speaker is meant to play once the crossover has been set.

Passive crossover: a small set of capacitors, coils and resistors between the amplifier and the speakers that splits the sound. Simple, but fixed.

Phase: where a wave is in its cycle, in degrees. Two speakers in phase add up; 180° apart, they cancel. How Andy uses it: the goal is "far from 180°", not 0°; anything within ±90° can be left alone (3.8 #6).

Pink noise: a hiss with equal energy in every octave, used as a test signal because its balance is similar to music's.

Pod: a custom housing for a speaker, often on an A-pillar or dash. How Andy uses it: a pod is an enclosure and must be sized, sealed and gasketed (2.4 #1, 2.4 #3).

Polarity: which speaker wire is plus and which is minus. Reversing it on one speaker makes it move backwards relative to the others.

Port (vented box): a tube or slot in a speaker box that reinforces bass around a chosen tuning frequency. How Andy uses it: he prefers vented sub boxes tuned for minimum excursion, with the in-car peak EQ'd out (4.3 #1).

Power response: a speaker's output averaged over all directions. How Andy uses it: because a car has no reverberant field, he says you mostly hear each speaker's power response (1.3 #1).

Q: for a speaker, a number describing how peaky its bass resonance is (low Q is flatter); for an EQ or filter, how narrow its band is (high Q is narrow). How Andy uses it: he recommends a flat, low-Q midbass in cars (2.1 #9).

Qts and Qtc: Qts is a speaker's total Q in free air; Qtc is its Q once mounted in a sealed box.

Rattle: a buzz from a loose panel, wire or part vibrating with the music. How Andy uses it: he says rattles and distortion give away a sub's location (4.2 #1).

RCA cable: the common signal cable between a source or DSP and an amplifier, named after its plug.

Rear fill: rear speakers played quietly to add space without pulling the sound backwards. How Andy uses it: plain in-phase stereo, high-passed, raised, then delayed until the stage returns to the front (1.11 #4).

Reflection: sound bouncing off a surface such as glass or the dash. How Andy uses it: he predicts reflection dips with a tape measure (1.3 #5).

Resonance: the frequency at which something (a speaker, a panel, a box, a room) vibrates most easily.

Reverberant field: the late, diffuse sound that builds up in a large room after many reflections. How Andy uses it: he says a car has none (1.3 #1).

REW (Room EQ Wizard): free measurement software often used for tuning, usually with a swept tone.

RTA (real-time analyzer): a display that shows the level at each frequency live, usually while pink noise plays. How Andy uses it: from 2018 on, his main tool for production tuning is a live RTA on mono pink noise (3.3 #1).

Sail panel: the small triangular panel at the front corner of a front door window, near the mirror; a common tweeter location.

Sealed box: an airtight speaker box with no port. How Andy uses it: with little space but plenty of power, sealed plus EQ; with no EQ at all, sealed is probably better (4.3 #4, 4.3 #6).

Sensitivity: how loud a speaker plays from a given power, usually in dB at 1 watt, 1 metre. How Andy uses it: a speaker 3 dB more sensitive equals doubling the amplifier (4.7 #3).

Signal-to-noise ratio (SNR): how much louder the music signal is than the background hiss.

Sine wave: a pure single-frequency tone, used for some tests. How Andy uses it: in his gain procedure only the sub amp gets a sine wave, and tweeters never do (4.8 #4).

Single-ended input: an amplifier input that measures its signal against ground. How Andy uses it: he identifies it by measuring near 0 ohms between the RCA shield and the amp's power ground, and pairs it with coax (4.10 #5).

"Smile" curve: an EQ shape with boosted bass and treble and a scooped-out middle, like a smile. How Andy uses it: cutting everything that sometimes annoys you ends in a "smile" curve that sounds bad (5.7 #13).

Smoothing: averaging a measured graph over a band (for example 1/6 octave) so tiny wiggles don't hide the overall shape. How Andy uses it: one mic with 1/6-octave smoothing is good enough for production tuning (3.4 #5).

Spatial average: a measurement averaged from several microphone positions around the listening area. How Andy uses it: he reports that a smoothed single mic was about 90% as accurate (3.4 #5).

Spider: the corrugated fabric ring that holds a speaker's cone centered and acts as a spring. How Andy uses it: break-in is the spider's resin cracking (5.1 #30).

SPL (sound pressure level): how loud a sound actually is in the air, in dB.

SQ (sound quality): car audio aimed at accurate, realistic sound, as opposed to sheer loudness; also the name of competitions judged on it.

Stage (soundstage): the overall picture of where the music seems to be: its width, height and depth. How Andy uses it: the stage can't be wider than your speakers (1.7 #1).

Subwoofer (sub): a large speaker in its own box that plays the deepest bass.

Surround: the flexible rubber or foam ring that joins a cone to the speaker's frame. How Andy uses it: a surround hitting a grille or panel is an installation error (2.1 #19).

Sweep: a test tone that glides from low to high frequency, analyzed by measurement software.

Tape-measure delay: How Andy uses it: setting delays from distances measured with a tape measure from the headrest center (or mic tip) to the center of each speaker's grille or dust cap, keyed to the midrange, then left alone. He converts with ms = inches ÷ 13,584 × 1000 (3.9 #3).

Target curve: the frequency-response shape a tuner aims for. How Andy uses it: his target is about +10 dB below about 60 Hz, flat from about 160 Hz, and −6 dB at 20 kHz, placed on the dips with the peaks cut down to it (3.5 #1, 3.6 #3).

Thiele/Small (T/S) parameters: standard numbers describing a speaker's low-frequency behavior, such as Fs, Qts and Vas, used to design boxes.

Top plate: the steel plate at the front of a speaker's magnet structure, through which the voice coil moves.

Transfer function: a measurement of how one thing changes a signal; in car audio, how the car changes a speaker's output. How Andy uses it: cabin gain is the car's transfer function (4.1 #1).

Trim panel: the inner plastic or fabric panel of a door. How Andy uses it: it is the worst rattle source, so deaden it first (2.2 #1).

Tweeter: a small speaker, usually a dome about 1 inch (25 mm) across, that plays the highest frequencies.

Twisted pair: a cable with two signal wires twisted together, which helps reject noise. How Andy uses it: use it for differential inputs (4.10 #5).

Two-way and three-way: a two-way system splits each side between a woofer and a tweeter; a three-way adds a midrange. How Andy uses it: he says cars need 3-ways (1.4 #4, 1.4 #6).

Upmixer: a processor that spreads two-channel stereo across more channels, such as a center and rear speakers. How Andy uses it: for music he favors upmixers that extract the content left and right share (1.12 #6).

Vas: a speaker's equivalent air volume, a T/S parameter used in box design.

Voice coil: the coil of wire attached to the cone that the amplifier's current flows through; it moves in the magnet's field to drive the cone.

Waveguide: a shallow horn-like shape around a tweeter that controls how it spreads sound. How Andy uses it: he says one big enough to match a 6-inch woofer won't fit in a car (1.4 #6).

Wavelength: the physical length of one cycle of a sound wave; low notes have long waves, high notes short ones. How Andy uses it: a reflection dip falls where the reflected path is half a wavelength longer than the direct one (1.3 #5).

Widebander (wideband speaker): a small full-range speaker meant to play most of the range without a separate tweeter. How Andy uses it: his later view is to aim tweeterless widebanders at the windshield, since on-axis they sound "clinical" (1.8 #4).

Xmax: the distance a speaker cone can travel in one direction while still behaving in a linear (clean) way. How Andy uses it: the cone can travel past Xmax, so leave clearance; keep grilles about 1.25 inches off a woofer's front (2.1 #19).

Appendix A. Where Andy's material lives

Videos, podcasts and livestreams

"Transcribed" = YouTube auto-captions read in full for this research.

1. Title: Old Fashioned Car Audio Podcast (OFCAP) Ep. 19, "Andy Wehmeyer - AudioFrog"; Channel / host: Matt Schaeffer & Gary Bell; Date: Audio Oct 29, 2021 (YouTube Oct 9, 2025); Length: 3:54:13; URL: YouTube · Apple; Best for: Richest single source: power and clipping myths, crossover mistakes, tuning philosophy, choosing a shop, sales, industry economics; Transcribed?: Yes
2. Title: OFCAP Ep. 38, "Andy Wehmeyer Phones Home"; Channel / host: Matt Schaeffer & Gary Bell; Date: Audio May 17, 2023 (YouTube Oct 9, 2025); Length: 1:25:44; URL: YouTube; Best for: Volvo C30 demo build, mounting and deadening, two-seat philosophy, de-tuning for image-haters, contest gaming; Transcribed?: Yes
3. Title: SQOLOGY, "feat. Andy Wehmeyer – Part One"; Channel / host: Benny Z & Company; Date: Audio Nov 27, 2017 (YouTube Sep 25, 2024); Length: 1:03:55; URL: YouTube; Best for: Background, MS-8 origin, MP3 and hi-res, experience vs data, OEM vs aftermarket; Transcribed?: Yes
4. Title: SQOLOGY, "feat. Andy Wehmeyer – Part Two"; Channel / host: Benny Z & Company; Date: Audio Jan 5, 2018 (YouTube Sep 25, 2024); Length: 48:23; URL: YouTube; Best for: Upmixing, two-seat tuning, score sheets, leaving Harman, the Audiofrog name; Transcribed?: Yes
5. Title: "AUDIOFROG | AUDIOPHILES | CONNECTED"; Channel / host: CMA Networks (Ben Woo, Importel); Date: Nov 27, 2023; Length: 1:05:07; URL: YouTube; Best for: Factory upgrade path, class-D and pink-noise power, immersive audio, binaural demos; Transcribed?: Yes
6. Title: "Audiofrog - High Fidelity Car Audio Designed by Experts with Andy Wehmeyer - Importel"; Channel / host: CMA Networks (Ben Woo, Kelly Holly); Date: Mar 24, 2021; Length: 54:45; URL: YouTube; Best for: Product-line rationale, durability and power tests, Bose/Harman dash trap; Transcribed?: Yes
7. Title: "AUDIOFROG | AUDIOPHILE | SHOWCASE" (A-series amp launch); Channel / host: CMA Networks; Date: Oct 29–30, 2022; Length: 1:15:45; URL: YouTube; Best for: Amplifier truths: load-dependent class D, feedback, thermal rollback, FM noise, differential inputs; Transcribed?: Yes
8. Title: "CMA CONNECTED | Audiofrog" (B2); Channel / host: CMA Networks livestream (Ben Woo, Romesh of Importel, dealer Bentley Burchard); Date: Oct 25, 2021; Length: 1:04:09; URL: YouTube; Best for: Premium buyer profile and the name, three kinds of shops, dash "middler" physics, reuse OEM systems, "back off correct", the disco customer; Transcribed?: Yes (round 4)
9. Title: "Andy and Audiofrog !" (B1); Channel / host: Absolute Electronix livestream; Date: Mar 1, 2023 (US evening); Length: 1:13:32; URL: YouTube; Best for: Career story, woofers designed from the car, DSP-amp gain trap, class-D filters, $5 imaging lesson, one-to-one OEM upmix integration, 2023 system-design seminars; Transcribed?: Yes (round 4)
10. Title: "Andy Wehmeyer is live at a Special time 2:00 pm est"; Channel / host: Dean and Fernando's Car Stereo Clips (same stream also on Five Star Car Stereo: bvd8ugEw7iA); Date: Jan 9, 2024; Length: 1:01:29; URL: YouTube; Best for: All-pass filters and the 250 Hz two-seat insight, upmixer history, binaural head; Transcribed?: Yes (the Five Star copy was not re-transcribed)
11. Title: "Andy Wehmeyer talks Up mixing" / "...talks All Pass filters"; Channel / host: Dean and Fernando's Car Stereo Clips; Date: Aug 7 / Aug 6, 2024; Length: 15:29 / 18:50; URL: Up mixing · All Pass; Best for: Excerpts of #10 (all-pass clip unverified); Transcribed?: Covered via #10
12. Title: "Audiofrog Testgear UMI-1"; Channel / host: AudioFrog official channel; Date: Nov 8, 2021; Length: 33:19; URL: YouTube; Best for: Measurement-first REW workflow, mic calibration, measuring from outside, test-CD tracks; Transcribed?: Yes
13. Title: "How to Tune a Cadillac Deville ... PART2 Andy Wehmeyer to the Tune rescue"; Channel / host: 361 VR; Date: Jul 12, 2019; Length: 14:40; URL: YouTube; Best for: Why tune, pink noise, mic arrays; Transcribed?: Yes
14. Title: "Andy Wehmeyer shows his new system at CES 2016"; Channel / host: Ricardo Rangel; Date: Jan 6, 2016; Length: 5:31; URL: YouTube; Best for: Multiseat demo car, real centre speaker; Transcribed?: Yes
15. Title: "How to Handle the 'Cheapest Option' Objection Like a Pro"; Channel / host: Mobile Electronics Association; Date: Oct 14, 2024; Length: 1:04; URL: YouTube; Best for: Price-shopper calls; Transcribed?: Yes
16. Title: "Talking car audio with audiofrog"; Channel / host: carsandcalibres; Date: Mar 7, 2024; Length: 1:16; URL: YouTube; Best for: Host narration only; Transcribed?: Yes (no Andy content)
17. Title: Erin's Audio Corner GS8ND2 review (Andy's written statement on the page); Channel / host: Erin's Audio Corner; Date: Sep 1, 2020; Length: n/a; URL: Page; Best for: What the shallow GS8ND2 is for; Transcribed?: Text read
18. Title: "AUDIOFROG"; Channel / host: Ricardo Rangel (streamed or premiered); Date: about 2020; Length: 15:01; URL: YouTube; Best for: Unknown; Andy's presence unconfirmed; Transcribed?: No (page froze twice)
19. Title: "AUDIOFROG CUSTOM SPEAKER INSTALLATIONS MADE EASY"; Channel / host: AudioFrog official channel; Date: about 2015; Length: 1:58; URL: YouTube; Best for: What comes in the speaker box; Transcribed?: No (page froze twice)
20. Title: "Andy From Audio frog demonstrating how to install GB 25"; Channel / host: Anthonys car audio life; Date: Oct 4, 2022; Length: 2:04; URL: YouTube; Best for: GB25 install (would have to be watched); Transcribed?: No (no captions)
21. Title: "AUDIOFROG DEMO CAR VISITS OUR STORE!"; Channel / host: Absolute Electronix; Date: Aug 3, 2023; Length: 6:03; URL: YouTube; Best for: Volvo demo-car facts (7 amps, 3-way doors, 6"+1" centre); presenter not identifiable as Andy; Transcribed?: Read; not counted as Andy

Not found as recordings: SEMA 2012 "Car Audio Mythbusters" seminar (listing); KnowledgeFest 2015 "Tuning Cars" Parts 1–3 with Larry Frederick (CE Outlook); his two MasterTech Expo 2023 seminars (car mapping; measurements and "audio truthiness"), previewed in #9. A TEDx talk by an "Andy Wehmeyer" (_e0by1vQVx4) is probably a different person. The official channel @audiofrog6034 has only two uploads, so his video teaching lives mostly in guest appearances.

Audiofrog Tech Blog (16 posts by Andy, Dec 2020 – Oct 2021; index)

Is it okay to use the terminal screw to crimp a ferrule? (Dec 15, 2020)
Tech Tip: Digital Audio Basics (Dec 21, 2020)
Pink Noise, White Noise and Why Your Tweeters never get 150 watts (Dec 21, 2020)
To Cap or Not to Cap? Tweeters in systems with active crossovers (Dec 21, 2020)
Time Alignment Part 1 (Dec 21, 2020)
Damping Factor and Why it isn't Much of a Factor (Dec 22, 2020)
Time Alignment Part 2 (Dec 22, 2020)
Time Alignment Part Three: Delays and Crossovers for Tweeters and Mids (Dec 22, 2020)
Crossovers: How They Work and How to Choose Them (Jan 14, 2021)
Measuring Frequency Response: Single Mic or Multi-Mic Average? (Jan 2021)
A Note about Target Curves (Mar 10, 2021; revised Apr 2021)
Are scopes and sine waves useful when setting up DSP? (Mar 24, 2021)
Testgear UMi-1 includes a CD with tracks designed for listening (Apr 14, 2021)
Dispersion and reflection (Jun 14, 2021)
How to test for polarity (Aug 17, 2021; revised May 2023)
Crossover Slopes and Protection for Speakers (Oct 7, 2021; revised Feb 2022)

(He also refers to a "Time Alignment Part 4" on sub/midbass crossover offsets; it is not in the list above and was not read.)

Testgear and other Audiofrog documents

testgear.audiofrog.com: his free tuning guide, "A Straightforward One Seat Tuning Process and Some Notes About Why it Works" (about 65 pages; target-curve import on pp. 37–38), plus tuning-CD files and measurement notes. [Conflict: in 2018 he described his stereo guide as two pages of process followed by about 60 of explanation; the round-1 notes describe about 40 pages of explanation followed by about 20 of process.] His REW tuning document was written for REW 5.19 (DIYMA 2021-07-15); he also posted a Basic Delay Calculator spreadsheet (DIYMA 2018-05-22).
UMI-1v2 tuning kit and the Binaural page; company pages for spec-reading: amplifiers, warranty, GB10OE tweeter sheet. Every Audiofrog sub manual includes sealed and vented box designs (B1 @7:18).
His older "Tuning Cars" PowerPoint/PDF for retail installers (referenced in DIYMA 2016-01-29; not retrieved).

Magazine, press and retailer items

Mobile Electronics: "Tech Today – DSP Tuning Part 3" (Aug 2017); all his columns via the Andy Wehmeyer tag page; Audiofrog items via the Audiofrog tag page. Best for tuning-as-troubleshooting and billing for tuning.
EDUCAR: "What If There's More Than One Seat? Center Channels and Upmixing"; author page.
CE Outlook via Big 5: "The Aftermarket Responds To Autoblog" (Jul 2018). BusinessWorld: "Demystifying good sound" (Mar 2024).
Crutchfield: "How to choose the right Audiofrog components" and "Who is Audiofrog?".
Otomotifnet/GridOto (Indonesian): profile, Oct 2016; Audiofrog U training, Aug 2019.
Erin's Audio Corner reviews relaying his design notes: GB15, GB25.

DIYMobileAudio accounts and their most valuable threads

Both accounts show only anonymized numeric usernames.

"14642" (2008–2016, Harman and early Audiofrog years):
1. "JBL's MS-8 processor!" and the "JBL MS-8 FAQ" compilation: MS-8 logic, industry views, contest stories.
2. "HOW COME NOBODY MAKES A GOOD DSP??" and "Please don't shut this thread" (2016): auto-tune limits, retail tuning process, judging speakers by data.
3. "The more I look at Sinfoni" and "Are break-in periods necessary/ worthwhile?" (2015): reading graphs, QC, break-in.
4. "Time Alignment Via Tape Measure Site..." and "Xover phase shift" (2015).
5. "Definition of 'Sound Quality' inspired by IASCA" and "ultimate consequences of buying online" (2008): contests, OEM vs aftermarket, retail economics.
6. Classic myth threads: "Damping Factor" (2011), "Lossy vs lossless formats" (2013), "Phase coherency: The Holy Grail of Car Audio" (2013), "HRTF" (2016).
7. "Andy is Leaving Harman" (2013).
"156546" (Feb 2017 – Mar 2022, about 810 posts; his first post under this name says it was a new username):
1. "Audiofrog Test Gear" (2017): one-seat tuning in two conditions, spatial vs single-mic averaging, MS-8 internals.
2. "Making stage wider" (2017): balance test, no images outside the triangle.
3. "Five Channel Soundstage" (2017) and "Is Rear Fill (and center channel) helpful or hurtful" (2018): how upmixers really work.
4. "Tuning Tricks" (2018): no tricks, only a process.
5. "RTA/REW- 90 degree or 0 file" and "Time delay measurements…" (2020): mics, averaging, LR4, reflection arithmetic, Harman-curve origin, patents.
6. "Clipping revisited with more evidence" (2020) and "Will too little power damage a speaker?" (2021): tweeter power arithmetic.
7. "Time Alignment revisited. Use technology!" and "Acoustical crossovers and volume" (2021): tape-measure delays, bass-up-front recipe.
8. "Polarity mystery, need some help" (2021): factory all-pass filters.
9. "House Curve – tweeters in A-pillar / woofer in lower doors" and "How to compensate for Comb Filters" (2021): measure-then-listen, target at the dips.
10. "Understanding DSP Output Voltage…" (2021): gain structure.
11. "Time to educate y'all bit depth sampling rate bitrate" (2021): digital audio, vinyl, Bluetooth.
12. "Speaker cone material", "Differential inputs from your headunit" and "Power handling, gimmick or..." (2021).
13. "Audiofrog manufacturer" (2020–21) and "Good Chinese speaker manufacturers on Alibaba" (2022): manufacturing and origin.
14. "Help: when to stop" (2022).
Not covered: his daily tech tips on Facebook, Facebook SQ groups and the Audiofrog web forum.

Appendix B. How this research was done

Forum posts, account "14642" (2008–2016): about 75 member-restricted keyword searches (about 2,200 result posts screened), the member-search pages 1–25 (about 500 posts, Apr 2015–Jun 2016) and the MS-8 FAQ compilation thread; only posts whose markup carried his author ID were used.
Forum posts, account "156546" (Feb 2017–Mar 2022): every post in his member-search listing, about 810 in all (240 + 140 + 40 + 80 posts on the newest pages 1–25, and 240 + 71 on the older-date pages), each author-checked; one post (4829145, Jun 2017) could not be read, and two thread-opening posts lacked a captured author attribute but appear in his member list.
Audiofrog material: all 16 bylined Tech Blog posts, the two tuning PDFs on testgear.audiofrog.com, and unbylined company pages (marked COMPANY, probably his but unsigned).
Video and audio: 16 appearances transcribed from YouTube auto-captions (14 in round 3, plus the CMA Connected 2021 and Absolute Electronix 2023 livestreams in round 4); Erin's Audio Corner text; obvious caption mishearings (e.g., "audio fraud" for Audiofrog) were corrected, and timestamps are approximate.
Articles: Mobile Electronics columns, EDUCAR, CE Outlook/Big 5, BusinessWorld, Crutchfield, Otomotifnet/GridOto, SEMA and CE Outlook listings.
Method: his own words only (host and forum-member statements used only as labelled context); everything paraphrased, quotes under 15 words; [RARE] marks points that contradict or go well beyond common advice; duplicates across years merged, with the dates kept to show consistency or change. Apparent typos were reproduced and flagged in the notes (e.g., "22,500 Hz" for the 44.1 kHz Nyquist limit; Bluetooth "1kbps").
Known gaps, topics: he barely addresses the "Big 3" upgrade (only that it rarely fixes noise and should be crimped), stiffening capacitors (only "not needed, remove it") and A2B digital audio buses (nothing found); whole-system wire-gauge budgets and deadening detail are thin in the 2017–2022 posts.
Known gaps, sources: three clips untranscribed (Appendix A #18–20); his MasterTech 2023 and SEMA/KnowledgeFest seminars not found as recordings; the MEA channel, 12voltnews and podcast apps for 2024–2026 not searched; Facebook not covered; linked Dropbox charts, the old "Tuning Cars" deck and one Mobile Electronics Q&A page not retrieved.

The full series

Download the complete guide as one PDF (351 pages, every point with its explanation).