What’s the most important factor for a good car sound system?

Opinions? Facts?

I’m no audio expert, but I like listening to music while I drive, and assume there are several key factors, including:
Overall quietness of the car;
Having speakers near ear level;
Speaker quality.
And maybe bass response (subwoofer)?
Number of speakers?

What factors matter the most?

This.
I hate speakers down at the bottom of the door near my feet. (unfortunately, I only buy compact cars-- and that’s where they put 'em)

Imaging. You should be able to close your eyes, look ahead and picture the band on a stage across the dash. Oh, but don’t try closing your eyes while while driving.

Speakers in a good car audio are placed to maximize the benefit of where they are placed. Lower doors are a good place for bass speakers. Cross firing tweeter and midrange speakers in doors or the A-pillar provide stage width. A center channel speaker anchors the lead vocals to the center of the hood.

An audio amplifier or head unit can use digital signal processing to maximize the sound pressure level at the at each passengers head. This is common in all factory installed systems, but higher level trim gets higher quality components.

After market systems can sound much better than factory because they don’t have the packaging constraints and are custom adapted to the individual buyer.

My guesses are that ear-level speakers and low overall car noise are most important factors (but, again, I know very little about car audio).

In the old days I would start my car, turn on the sound system, and the music would blast out at an unholy volume, because that was the level I was using while driving on the highway. It would make you realize the huge amount of ambient noise the music was fighting with while you drove.

I’ve never tried a simple upgrade of my door or rear deck speakers — my intuition is that it wouldn’t make a major difference, beyond a possible increase in volume. I already worry about the volume level of vehicular audio.

An AMG built v8 and exhaust.

Not a helpful answer, but…low price. (My hearing isn’t so good, so “high quality” sound is just a waste of money.)

For me, it’s most important that when the “On/Off” control is placed in the “Off” position, it functions as designed.

Many modern car audio systems come with a built in feature that seeks to automatically adjust the volume in line with ambient noise, addressing the issue you describe. If that is a big issue, you may just need to turn that setting on. I have noticed that some systems work better than others, though, so it may not be the only problem.

Jeez — that seems arbitrary.

These days most of my music listening is in cars (or checking certain songs out on Youtube). Occasionally I’ll listen to music files while doing work on my desktop computer, but I can’t write or do other demanding work while listening to tunes.

I’ve never thought about speaker location. I’d think the most important thing would be speaker quality. It doesn’t matter where they’re positioned or how many you have if they sound like garbage.
After that, I think I’d say a subwoofer. It doesn’t have to be anything special. I don’t need my windows to rattle or the people in nearby cars to feel it, but if we can put some of the low end on it’s own channel, we can invest in main speakers that do a better job with the mid and high range.

This is, of course, assuming we have a decent head unit and/or amplifier and a ‘nominal’ number of speakers. If you have one speaker in each front door and a $50 head unit from radio shack, you might run into problems no matter how good everything else is.

I suppose quietness of the car makes sense as well. Most of my cars have been compact/cheapish cars and, while it’s partially just due to my hearing, I have to turn the radio way up if I’m on a ‘loud’ road, like concrete freeways at 70+ mph.

TLDR: IMO, good speakers would be the most important thing.

You can have the best speakers available that will fit in your car but they can still sound like crap if the system isn’t tuned/EQ’d to take advantage of them or they are in a bad location. That’s where the head unit/amplifier comes in, a good one will have the ability to tune the sound for the shape of the car and the person who defines that tuning determines how good it is.

I’ve seen decent audio systems with cheap speakers sound as good as premium level factory system. But in general the lower grade 4 speakers in the door system are utter crap and are only there for people who A) don’t give a damn about sound quality or B) for people who are going to take the cheap ass system out and go to aftermarket shop and put something decent in its place.

Not much you can do about road/cabin noise unless you want to add sound deadener or use advanced technology Noise Cancellation techniques that isn’t available yet for aftermarket applications. Some systems just boost the volume dependent on how fast you are going, but there are issues with this like open windows and perception of certain frequency ranges being perceived as boosting more than others.

primarily, thd … secondary, audio-equalization (parametric, graphic, etc.) … and, if possible, gutt the vehicle’s interior and install sound-deadening materials. everything else will be an extension of these parameters. as for brand-name product … i’ve stuck with alpine for the past 40+ years.

I’m the farthest thing in the world from an audiophile. For me, the most important factors are ease of use. My current vehicle has steering wheel media controls, easy bluetooth connectivity, and Android Auto when I want extra features.

The “big upgrade” in my last vehicle’s sound system was an auxiliary input jack for my phone, so all this stuff still feels like I’m living in the future.

When I sold car audio equipment the biggest improvement in sound could be had with more watts per channel, or as stated above, lower THD (total harmonic distortion). Stock radios are notoriously under-powered and people would often complain that the sound would distort when they turned up the volume. A good head unit with a decent amount of power or a separate amplifier makes all the difference. From there better quality speakers make an improvement and adding a subwoofer (even a single 8") can really fill out the sound.

Quality speakers with big magnets and plenty of power to drive them. A nice EQ helps to tailor the sound to your preference.

are after market car audio systems still big sellers? Most new cars now have a nice system that most people are happy with.

This would have been our departed friend jz’s thread to rule over. I take note of the lose to the board by his absence.

First I agree with having quality speakers but have to point out that you can make better high quality speakers with smaller rare earth Neodymium magnets. Better being that you can pack more punch into a smaller package. Unless you like speakers bulging out of you doors or looking like eyeballs coming out of your A-Pillars there is no inherent advantage to using bigger ferrite magnets.

Aftermarket sound systems are still a thing as their are many levels of cars that just get cheap audio systems put in by the manufactures. I’ve driven many a rental car with low grade audio systems that sounded fine when I first started driving them but after an hour they actually hurt my ears and gave me a headache due to the lack of tuning the system properly and high distortion.

And people love to customize their cars and audio is one where you can really express yourself. As an individual you can decide that you can put that huge bass box in you vehicle and sacrifice cargo capacity, as an OEM maker of audio systems I cannot.

Power (or wattage) is a different animal and from my viewpoint should not be used to judge an audio system because the equations can be manipulated to achieve high wattage without delivering a significant level of sound level performance. I’ve seen many high 1200 watt systems that did not sound as good as a 300 watt system that was properly designed. Many times the extra wattage just makes the amp run hotter. It’s more of a marketing gimmick for many sellers of sound systems.