The Seemingly-Awful State of Car Amplifiers .... Does it even matter?

[Quinton595]

Heyo,

I feel like I have learned a lot about home audio equipment over the years, in large part thanks to sites like ASR and the kind folk here.

One area where I know very little, however, is the world of Car audio.

The basics make sense to me; it's just a home speaker setup that's shaped a little different, but trying to choose source gear seems much more difficult, because it all seems to be garbage.

I get that ASR has bigger priorities than car audio gear, so there's not a ton of reviews here, but so far, the absolute finest car amplifier Amir has ever tested, the SounDigital SD300.2D -- a limited-edition device made with rare gallium-nitride magic -- manages a SINAD of only 93. A rating that would basically be a fail compared to desktop amps. Same with its other specs; they're not great.

But... it seems no one minds? I mean, when I browse a site like Crutchfield, I see dozens of amplifiers with glowing 5-star reviews. And, at first glance, this makes some sense, because, after all, these are cars we're talking about. They aren't exactly pristine listening rooms -- and that's before you add in all the road noise and engine noise, so a part of me understands that pure transparency might not be that big of a deal for these components.

I tried posing this question to an LLM, in regards to the Fosi CA30, which actually seems to measure respectably, especially considering the price, and it responded interestingly:

The SINAD reframe — and where the CA30 actually lands​

There's a kernel of truth in your observation, but the framing overshoots. It's correct that car amps as a category aren't engineered or marketed around the SINAD figures Topping/SMSL/JDS compete on, and the few that get put on an APx-style bench can land well below desktop numbers. But "they're all awful with 60 dB SINAD" is too broad — and the more useful question is what threshold actually matters in a moving truck.

Here's the part worth internalizing: your resolving standard does not transfer to a vehicle cabin. Road noise in a truck at highway speed is 65–75 dB(A). That's the environmental noise floor every component sits behind. An amp at 0.1% THD+N (≈ 60 dB) is putting its worst-case distortion 60 dB down — already buried — and then the cabin buries it another 30+ dB. Audioholics, who use a stricter bar than most, consider 0.1% the "fidelity firewall" rather than the industry-standard 1%, and want to see at least 80 dB SNR at 1 watt so the noise floor doesn't mask detail at low listening levels. That 80 dB @ 1W figure is the bar that actually matters — not 120 dB. Chasing desktop SINAD in a car is buying HD800S to listen next to a running engine.

The real-world car audio noise problem isn't bench SINAD anyway — it's alternator whine and ground loops, which are install/grounding issues, not amp-spec issues. A clean install with a competently-specced amp is dead quiet; a sloppy install with a 120 dB amp will still whine.

Now, the CA30 specifically — and it's a genuine counterexample to your "60 dB" premise. Fosi's published numbers are ≤200 μV residual noise, THD as low as 0.008%, SNR greater than 100 dB, and a damping factor ≥140. THD+N of 0.008% works out to roughly 82 dB SINAD-equivalent — not desktop territory, but comfortably above your 60 dB floor and well past the audibility threshold in a car. More importantly, it's been independently verified: Williston Audio Labs dyno-tested it and found 99 watts/channel at 4 ohms against its 100W rating, ~149W at 2 ohms, and ~323W bridged against its 320W rating — concluding it did not exaggerate its power ratings, with a very low noise floor and clean playback. That's an honest amp. Fosi AudioFosi Audio

Still, I'd love to hear more about what you guys think, and whether this stuff really matters that much for car audio. Given that so little testing exists for car amplifiers, how does anyone have confidence in their purchase? How do you even decide which amp to buy?

Thank you!

 

[Chrispy]

Why would you rely on a site like Crutchfield for anything except price?

 

[Quinton595]

Why would you rely on a site like Crutchfield for anything except price?

Precisely the reason for my research and post here, good sir.

 

[Chrispy]

Won't find a lot of car audio tested here otoh. The specs are usually greatly exaggerated to start, and you can get more reasonable from there. Personally I use a coupla power amps along with my head unit in my van, one amp for a couple additional speakers, another dedicated to a sub. Decent specs. Nothing exciting but then home audio specs are often over-considered otoh.

 

[sam_adams]

. . . Does it even matter?

No. it doesn't. Carl out front woulda' told you.

 

[TonyJZX]

i think people HERE dont care too much as most people realise car interiors are terrible compromises

you either buy a luxury car and spec it up to a burmester or whatever and enjoy

if you have an older car then you do well to talk to a trusted local professional

to me its a bit of waste of time... i used to spend hours in my car as a systems consultant... my car of choice was largely a car like an american police Chevy Caprice PPV so as long as the audio was clear and you can hear vocals then it was all good... also i tended to favor straight line speed over just about everything else so i listened to the glass pack V8 exhaust in tune with the podcasts i would listen to

now I'm quasi retired and I'm largely in an EV that you cant upgrade for shit and anyway I'm 99% with the old lady and she takes precedence over music (you guys know what i mean)

i keep an eye (or ear) out for good OEM car audio... there's supposed to be some movement in car DSP treatments but really, the stuff i can afford is all like Harmon Karmon, Bose Sony kinda OEM rubbish

 

[Rickysa]

It's all about da bass...da bass

 

[Audiofire]

Power matters for car amplifiers to a given speaker impedance, since already about 0.1% THD or 80 dB SINAD is transparent for actual music. When driving a car with background noise, it hardly makes any difference which amp except power.

 

[formdissolve]

A SINAD of 93 for an amp is actually pretty respectable if you check out the amplifer chart on the site

 

[john61ct]

I am an edge case, as in I want top SQ for critical listening, multi-channel lots of subs

but need direct DC power, at least for the thirsty components, semi-mobile system, often being off-grid

The CA30 is in @amirm testing queue, hopefully soon, I think it will be fine.

So many chip amps are high quality these days 3e A7 for example, just need to get au fait with DCDC conversion, maybe a dedicated battery bank only use the 12V system for recharging.

miniDSP makes 12V powered processors

My point being, no need to limit yourself to "car gear" just to be able to run off DC power.

And also, lots of car gear is actually high SQ - JL Audio, Audiotec Fischer / Helix, Mosconi Audison...

Just because THIS site doesn't focus on it, does NOT mean you can't assemble a FINE system based on the above.

Of course the limitations of "the room" and speaker issues will be the weak links

not to mention the noise factor while in motion

stuff like SINAD pales in comparison

 

[Groove01]

You need to find a car audio forum, plenty of them out there, and plenty of them with very knowledgeable people.

It’s already been said, but there’s a different baseline for car audio specs because of the environment it’s being installed and the head unit’s providing the signals.

IMHO there are plenty of good amps, it’s harder and a lot more $$ to get a really good pre-amp only HU.

i have a closet full of kick ass car amplifiers - lol.

 

[DanielT]

Here’s a tip: I watch this YouTube channel every now and then.
Mainly when he performs tests and measurements on various tweeters, woofers, and so on—many of which are also suitable for home (DIY) hi-fi. He also tests car amplifiers. He has made close to five hundred videos:

RAW-CAt

All about car audio - raw.

m.youtube.com

 

[Rickysa]

My biggest gripe has been trying to find new head units for older cars that don't look like a 70's disco.

 

[EJ3]

I am an edge case, as in I want top SQ for critical listening, multi-channel lots of subs

but need direct DC power, at least for the thirsty components, semi-mobile system, often being off-grid

Us that spend large amount of time off-grid (and [in my case] not connected via cell tower [assume that everyone can stream {or wants to stream}, not something that I do or want to do, even when in the city]) are certainly outliers.
And, there is plenty of good gear available. It's just requires a bit more effort to find the good stuff.
I guess that we are spoiled by this site.
I appreciate that Amirm has spoiled us.

 

[john61ct]

Oh yes I never rely on Internet connectivity for my media, everything is DL opportunistically

For films & shows, store until consumed then delete. My music library is ever growing.

Some games my kids DL are MASSIVE I'm helping them build their own LAN storage.

I do use cloud services for backup space, up to 27TB there...

 

[kemmler3D]

Chasing SINAD for car audio is pretty pointless because the noise floor while you are driving will dwarf any noise coming from the amp. Think about it - in the quietest ride you've ever had, road noise would have to be at least 40dB SPL, and in my (fairly noisy) car I'd expect it's at least 10x that. So in a car, SINAD of 65 is going to be about as good as 90-120 in practice. Either noise level would be inaudible below the road noise.

Distortion is another story, so I would focus on that and ignore noise for the most part... and then it's a matter of whether it delivers power in the way you need it. I think head unit and/or DSP (for EQ) and speaker choice are by far the most important.

 

[EJ3]

Chasing SINAD for car audio is pretty pointless because the noise floor while you are driving will dwarf any noise coming from the amp. Think about it - in the quietest ride you've ever had, road noise would have to be at least 40dB SPL, and in my (fairly noisy) car I'd expect it's at least 10x that. So in a car, SINAD of 65 is going to be about as good as 90-120 in practice. Either noise level would be inaudible below the road noise.

Distortion is another story, so I would focus on that and ignore noise for the most part... and then it's a matter of whether it delivers power in the way you need it. I think head unit and/or DSP (for EQ) and speaker choice are by far the most important.

Of course, you may want better: such as when you are picnicking by a lazy river with the car/truck off but the stereo on. You know: being romantic.
Yes, even when you are married.

 

[kemmler3D]

Of course, you may want better: such as when you are picnicking by a lazy river with the car/truck off but the stereo on. You know: being romantic.
Yes, even when you are married.

Well, sure, but if the noise floor of your car's amplifier is enough to kill the mood I think the amplifier is the least of your worries.

 

[EJ3]

Oh yes I never rely on Internet connectivity for my media, everything is DL opportunistically

For films & shows, store until consumed then delete. My music library is ever growing.

Some games my kids DL are MASSIVE I'm helping them build their own LAN storage.

I do use cloud services for backup space, up to 27TB there...

Nothing leaves my direct control: no cloud, or internet connection for my TV, Stereo or vehicles.
Lap tops & tablets do not have a direct connection with each other or the desktop. (Yes I know that they can, which is also why they are not set up to do that).
The desktop can send to the stereo via Bluetooth.
Only the cell phone can connect to the outside (IF I am within the range of a cell tower). And the phone is not connected to any other devices, so...

 

[EJ3]

Well, sure, but if the noise floor of your car's amplifier is enough to kill the mood I think the amplifier is the least of your worries.

For me, there is no sense in having excess noise. But being able to support good to very good sound, while walking around the property is kinda one of my things. Via my truck, I can listen to/or watch DVD (or Blu Ray) or movies stored digitally, project them on an outdoor screen, etc.
It's just me. Others and what they decide for themselves, well, that is fine.
My wife doesn't give a damn about music, her preference, no matter where we are or what we re doing, is to have no music, just natural sound.
Inside the house or otherwise. (yes, the natural sound of the A/C, the heat is from baseboard hot water [so there is no fan noise and no blowing air, for heat]).