Help with understanding Head Unit specs

[Dktalee]

Okay, so im very new to car audio. Infact I just purchased my first head unit. Im rebuilding a 1987 Oldsmobile 442. I wanted an upgraded radio but one that would fit in my dash. I came across a 90’s-00’s Pioneer DEH-P77DH thats 1.5 Din in almost perfect condtion. This is in the specs.

CD receiver with built-in MOSFET45 amplifier (22 watts RMS/45 peak x 4 channels)

While searching for a set of quality 3.5 Dash speakers to hook it into. Though I have read online that 3.5” speakers are almost useless. Im doing the car in factory specs. Now I was looking for speakers and almost all speakers are rated at 80w to 120w are those numbers max? Or can my head unit not supply enough power? What do these ratings mean. I apologize. Im 20 and not familiar with these things. thank you.

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[Popwarhomie 5,000+ posts]

Yeah Max ratings are useless. RMS is all that matters and alot of lower end companies will inflate those numbers as well.

A higher sensitivity rating is what I would look at when needing low power speakers.

 

[Dktalee]

Yeah Max ratings are useless. RMS is all that matters and alot of lower end companies will inflate those numbers as well.

A higher sensitivity rating is what I would look at when needing low power speakers.

Do I need to worry about RMS or Peak power when buying speakers? If I purchase a 25rms speaker will it sound bad if I turn it up with my 25rms Radio? Or if I buy a set of speakers with 50rms will it sound terrible at loud volumes because my headunit isnt supplying it with enough RMS?

 

[marc2112 10+ year member]

They wont sound bad but an amp would get the best out of them and help keep up with your sub(s).

 

[n2audio 5,000+ posts]

Power ratings in general are a very gray area, and the cheaper the equipment the more gray it is.
RMS is all that matters. Quality brands generally rate equipment accurately. Cheap brands -- you get what you pay for, trust the price tag -- not the ratings.
A quality speaker that's rated for ~50w rms is going to work fine with a 20w head unit. It won't blow the doors off by any stretch, but it will produce decent sound at moderate volume. When the HU runs out of power the signal will begin to clip and sound quality will fall.

Take the same speaker and put it on a 50w amplifier -- at low/moderate levels it won't sound much different, but where the 20w HU began to struggle, the amp will begin to shine. The extra power will allow the speaker to continue playing clear at a higher volume. However, it won't sound twice as loud. Mathematically, doubling power yields a 3db increase in sound. It takes about 10x the power to (10dB) for sound to double.