41 Car Audio Lessons Most People Never Hear
These are the 41 lessons that Peter Steinbacher of Pssound, a UK high-end car audio installer and multiple EMMA sound-quality champion, repeats most in his YouTube videos. Few shops ever explain them. Under each lesson, one link takes you to the moment in the video where he makes the point, and a second goes to our full guide on that topic.
Planning the system
1. Get the speaker locations right before anything else
Peter's order of priorities has stayed the same for years. First decide where the speakers go, then install them in the best way for the job, then tune. Choosing the speakers and the amplifier comes after that, with the amplifier last. He admits some people will disagree, but he still wants a solid, good-quality amplifier from the start, especially in a daily car.
2. Tweeters are the exception: the driver itself matters most
Peter usually says location, installation and tuning beat equipment. Tweeters (the small speakers for high notes) are the exception, because no tuning can add detail the driver never produced. The DSP (digital signal processor, the box that does the tuning) can lift a top end that fades in the cabin, but it cannot restore lost detail. A tweeter can sit in many places without a big change in tonality, so its tone comes down to the quality of the driver.
3. Leave money for installation, not just equipment
The classic budgeting mistake, in Peter's view, is spending nearly everything on gear. With £3–4k to spend, people put £3,900 of £4,000 into equipment and are then surprised that the installation needs more. His advice is to always keep money aside for installation and materials, because the job will not happen without it.
4. Choose a car where the midbass is easy to do
Labour is the most expensive part of a build where Peter works, so he advises being clever about the car you start with. Pick one where the hardest job, the midbass (the speakers that play the punchy lower notes), can be done easily and well. The reason, in his words: "midbass is the killer in every car".
5. No budget for fabrication? His advice is a Mercedes
If there is no budget for fabrication (custom building work), Peter's standing recommendation is a Mercedes with 8-inch drivers up front. Swapping the speakers is about a two-hour job, and the result is one other cars only reach with hard work. BMW is his second choice, and few other cars fit, perhaps the new Mazda with its kick-panel speakers (low in the footwell). He said the same in 2023.
Where the speakers go
6. You cannot fight a bad speaker location
Whatever speakers, DSP or tuner you use, Peter says you cannot fight a bad location. Tuning can tame a peak (a pitch that is too loud). A cancellation (a dip where sound waves arriving by different paths cancel each other) is another matter. In his words, "if you have a cancellation, game over".
7. A simple 2-way leaves a hole in the middle
A 2-way front, meaning a door midbass plus a normal tweeter, is simple, but Peter says it will not give the best result. The door midbass falls apart above roughly 300 Hz (Hz measures pitch, and 1 kHz is 1,000 Hz). That leaves a hard stretch from 300 Hz up to 2 kHz, where most of the musical information sits. He has measured at least 30 cars over two to three years, and most door midbass locations share this gap.
8. Put a wideband speaker where the tweeter usually goes
To keep the front simple, a 2-way or only about 4 amplifier channels, Peter suggests a wideband driver (one that covers the middle and high notes) up high instead of the usual tweeter. It plays from about 200–400 Hz upward. The alternative is asking a low door midbass to reach 2–3 kHz or higher, which is hard and full of compromises. The wideband gives far better detail and a higher stage, meaning the music seems to come from higher up.
9. Do not suffocate the mid speaker behind the trim
A very common builder mistake is building onto the trim and leaving only a small hole for the speaker cable. A 3–4 inch mid (midrange speaker) then breathes into roughly 0.3–0.4 litres. It is suffocated, will not play low and shows a big peak from about 300 to 600 Hz. Peter's fix is to leave the back open so it vents to the side of the dash behind the pillar, though he will not promise that for every driver.
10. Keep each tweeter within about 20 degrees of the listener
Peter's rule of thumb is to keep each tweeter within about 20 degrees of the listener. Then it gives top-end detail without any EQ (turning certain pitches up or down) and blasts the side window less. The aim is to avoid extremes in either direction.
11. Never aim the tweeters at each other
If you aim the tweeters at each other, the driver-side one ends up about 70–80 degrees off-axis (angled away from you) and plays nothing above about 10 kHz. The passenger side is still at about 40–50 degrees. You can never get the driver side back, because boosting its top end with EQ would leave the passenger side with far too much treble to bear.
Getting the bass right
12. A flexing door smears the bass
Even when nothing audibly rattles, a door panel flexes, so sound comes from the whole door, not just the speaker. The bass seems to come from everywhere, and you feel diffused energy down the side of your body. The midbass cannot act as a point source (one single spot the sound comes from). That kills the pinpoint image competitions need, such as a stand-up bass on top of the dash, and the punch in the chest.
13. Test your midbass with the kick-drum challenge
Here is Peter's simple test. Mute every speaker except the midbass, then turn it up with something punchy, such as a live band's kick drum or electronic music with a tight kick. If you hear zero buzz, zero rattle and no flex, and you feel a kick in your chest, the install is good.
14. A rear sub cannot play evenly up to the midbass
Peter says a rear sub cannot play evenly all the way up to the midbass, as many people hope. At your seat it depends on cabin size and distance, and in longer estates and sports wagons it struggles above about 50–55 Hz. The wave reaches you, carries on to the windscreen and comes back, so some pitches add up and some cancel. Most longer cars suffer, and he sees no way around it.
15. A front sub's installation matters more than its driver
A front sub (a subwoofer, the speaker for the deepest bass, placed up front) makes a massive difference however you do it, Peter says. An 8, 10 or, in a huge car, 12 inch driver is a big step up. Driver choice matters, but far less than the installation, so he would never worry much about which driver goes up front. Just make sure it is happy in a small sealed box.
16. Deep bass needs a response that keeps rising
Peter says a flat bass response is not enough, because in a car you would not hear it. Below the sub's crossover (the point where it hands over to the other speakers), the response must keep rising. He wants at least about 3 dB (a unit of level) per octave (a doubling of pitch), with more at 25 Hz and again at 10 Hz. In his view only a true infinite baffle (subs in a sealed wall, with the boot as their box) can do that in a car.
17. Do not just turn the sub up
Peter's advice is not to fix the bass by simply turning up the sub. That moves the effective crossover point and breaks the alignment (how their timing lines up) between the front midbass and the sub. Raising a rear sub also just brings more buzz and more rattle. At full level the problem is obvious because the sub is out of alignment, as he shows listeners.
Installation and power
18. Solid mounting beats an expensive subwoofer
For Peter, mounting comes first. In the Megane every board is bolted to the chassis and the sub enclosure is bolted in too, so moving it moves the whole car and nothing rattles. He says this does more for the sound than buying the best subwoofer on the planet, so focus on it first.
19. Chamfer the back of every ring behind the driver
Peter says to chamfer (cut a sloping edge on) the back of every ring or baffle behind the driver, at about 45 degrees. A baffle is simply the board the speaker is mounted on. Less restriction on the airflow gives much cleaner sound, especially in the midrange, and a more natural tone. He says it is always worth the effort.
20. Deadening is not soundproofing
A common trap is that people say soundproofing but show pictures of deadening. Deadening sheets on the sheet metal or the door card only stop a panel from resonating, which means vibrating and ringing. Peter's point is that they do not absorb noise. They just calm the metal.
21. Put the most deadening on the door's inner skin
The speaker is mounted to the door's inner skin (the inner metal layer), so that skin is the baffle and must be stronger than the outer skin. People under-treat it, then wonder why it still flexes badly. On the VW Caddy it got a full layer of thicker material. Where the inner skin is a plastic door carrier, Peter treats both sides of it, which made a big difference on the Audi A6.
22. A 120 A alternator does not mean 120 A for your audio
The alternator (the generator that charges the battery) is built to feed the car's own consumers, such as aircon, lights and fans, with some headroom left over to charge the battery. So with a 120 A alternator you can realistically use 50–60 A, probably about half. Peter says that is enough for a sound quality system even at full tilt.
23. Fuse every time the cable gets thinner
If a thin cable shorts, the big fuse at the battery, sized for the thick main cable, never sees a problem, and the thin cable melts. So Peter says to fit a fuse every time the wiring gets thinner, rated for the most that thickness can safely take. One fuse at the battery is not enough: fuse from the distribution block (the box that splits the main feed) to each amplifier too. He also notes that fuses that look the same colour are not the same rating.
Tuning
24. Get the car tuned before you change anything
Until a system is tuned, Peter says, you have no idea what is still in it. Most people start thinking about new speakers and amplifiers when all it needs is a proper tuning session. If something sounds wrong, first ask whether it was tuned properly, or at all, because people often blame cheap speakers wrongly.
25. Harsh tweeters are usually untuned tweeters
The cabin and the tweeter's location usually leave too much level at 2–6 kHz, where the ear is most sensitive. People who cannot tune, or do not send the car to someone who can, decide the tweeters are harsh. They sell them and buy others, which behave much the same in the same spot. Peter's summary: "it's not the tweeter, it's the environment", and after EQ the VW Golf's tweeters sounded smooth and natural.
26. EQ the slope too, at least an octave past the crossover
A crossover does not switch a speaker off instantly; the speaker fades out along a slope. Peter says to EQ that slope too, at least an octave past the crossover point. A peak below a tweeter's 3 kHz crossover still plays together with the midrange, and a peak in the mid's slope lands where the tweeter plays.
27. A sub out of phase cancels far above its crossover
Out of phase means the sub pushes while the front speakers pull, so they work against each other. The Golf mk8's sub was crossed at 60 Hz, yet out of phase with the front it cancelled everything from 45 to 120 Hz, an octave above the crossover. Once it was in phase and timed to the front end, it added up smoothly.
28. Rear fill needs a special feed, not plain left and right
Most people patch left to the rear left and right to the rear right. Peter says rear fill (speakers behind you that add ambience) needs a different feed. The left rear gets left plus right with the right polarity-reversed (flipped upside down), and the right rear gets the mirror image. Anything recorded in mono (identical in both channels) cancels, so only the stereo difference plays, adding ambience and room information without touching the front stage.
29. The centre image is not straight in front of you
The centre image always sits midway between your far-left and far-right images, which in a car is not straight ahead. Instruments must separate clearly into left, right and centre, and a mono-recorded singer should sit at the centre of the stage, not in front of the steering wheel. A centre straight ahead only happens at home, with equal distances and angles. In a left-hand-drive car it lands roughly mid-dash at eye level.
Sources, DSP and amplifiers
30. Skip speaker-level integration for music
Speaker-level integration means feeding your system from the speaker wires of the factory head unit (the car's stereo). Peter says there is no point asking how to get the best from it. Even with every trick it sounds OK at best, nothing like Bluetooth streaming, an optical adapter or a phone with a DAC (the chip that turns digital music into sound). He wants a source with a clean, untouched signal.
31. HD Bluetooth can beat wired CarPlay
In the Porsche Boxster, HD Bluetooth (aptX) audibly beat wired CarPlay. Peter says CarPlay modules are built for connectivity, ease of use and functions, not sound quality, and the DAC in that tiny box is poor. He finds aptX good enough, and Pssound streams this way in many cars because it is convenient and needs no extra wires.
32. Buy a DSP with fully parametric EQ
Before you buy a DSP, Peter says, check that it has fully parametric EQ: no fixed EQ points and no limits on where an EQ can go. He stresses this three times. With a peak at 5,728 Hz you must be able to target exactly that point, because fixed points such as 5 kHz or 6.3 kHz cannot fix a problem between them. You also need to set the Q, meaning how wide or narrow the fix is.
33. A semi-active setup is still more than good enough
Peter says semi-active is still more than good enough: a passive crossover (a simple filter box) between mid and tweeter, with the midbass on its own channel. You still control the midbass and time it to the mid, but you lose mid-to-tweeter alignment. There the ear cares more about level than timing, and a good tuner can fix level with the DSP. It works best when mid and tweeter sit close together on a similar vertical axis, as in the Mercedes W213 and the BMW M6.
34. Tweeters and mids need very little amplifier power
Picture a 150 W × 6 amp running a fully active front (every speaker on its own amp channel). Even at full tilt, Peter says, the tweeter and mid take only 10 to 20 watts, the mid perhaps 20–30 W. The midbass takes as much as it can, about 50–100 W, and would give out before taking 150 W. The sub is the speaker that really needs the power.
35. Give the sub its own monoblock amplifier
Peter says multichannel amps never run subs with the same control. Pushed hard, they are not as clean and dynamic as a monoblock (a single-channel amp) with its own power supply, even at the same paper power, such as 240 W. In the Mercedes B-Class, the sub on two channels of the Match amp performed far below the new Helix M1 at 1 Ω, which has about double the headroom the sub needs.
Shops, competitions and myths
36. Always ask the shop for photos of your build
Peter says to ask the shop for documentation, ideally daily updates. A couple of photos or videos should show how the door driver was mounted (screwed to plastic or fixed rigidly to the inner skin), how the deadening was done and where the amps are. He rejects the excuse of no time, since it takes only five minutes at the end of the day. If you never asked and then feel ripped off, he says it is your own fault.
37. Check the absolute basics yourself
A classic bad-shop pattern is selling expensive equipment and never checking that left is left, right is right, and each midbass is on the same side as its tweeter. In the VW Transporter, the previous shop had wired a passive Rockford Fosgate 2-way with the right midbass to the left tweeter and the other way round. Peter found it when he moved the balance to one side and the other side kept playing.
38. Too few people in the world can tune properly
Tuning is the bottleneck everywhere Peter goes. He has found only a few people worldwide, in America, Europe and China, who tune correctly, far too few for the size of the market. In China, he says, every shop should have at least one person who tunes at or near his level. Until every shop tunes at that level, results stay poor, customers stay unhappy and the industry suffers.
39. Do not trust a product just because it won competitions
Peter is sceptical when a new product is called the best because it won competitions. Competition is maybe 1% of the market, and many products did one thing well but had too many problems to live with. His advice is to give such a product five years for its reliability to show.
40. Competition judging hides door-midbass problems
At the judging level of about 80–85 dB, the midbass is not seeing even a watt, so it barely moves the door. Chest and kick bass are not tested, so door midbass escapes notice. The problems only appear when you turn a dynamic system up. Peter heard them straight away in the April Salzburg category winner, which had door midbass plus a front sub, though he said it was not bad.
41. Clipping, not power, is what burns speakers
Peter says a clipped signal (one distorted into a square-looking wave) burns speakers, not power as such. With a square signal a speaker can burn even at very low power. With a clean signal you can send as much power as the excursion (how far the cone can move) can handle. Likewise, a big amp will not fry an infinite baffle sub, because its impedance (the electrical load the amp sees) rises near resonance and the real limit is excursion, not heat.
Those are the 41 lessons Peter returns to most. If one of them matches a problem in your own car, follow its guide link for the longer explanation, and use the full series to find the rest of the topics.
This is an independent, plain-English summary of Peter Steinbacher's public YouTube videos, written by VA3 Car Studio. It is not affiliated with or endorsed by Pssound. The links jump to the moment in each video where he makes the point.
Part of our series: Car audio lessons from Pssound, start here
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