Car audio question

I’m looking to upgrade the speakers in my 18 crosstrek. It’s a 6 speaker (2 dash tweeters, 4 door speakers) system driven off the headunit and the sound is pretty abysmal. A factory Rockford fosgate system is available for $350 but it’s only a small amp and front door speakers. I’m hoping to save a little money and just replace the door speakers with a quality set of aftermarkets. I do not want to install an amp. I’ve done that route and I’m not interested in doing it for this car.

The speakers I’m looking at:

https://www.amazon.com/gp/aw/d/B01E8OZ1KM/ref=ox_sc_act_image_1?smid=A36FHUSDHDORFF&psc=1

3ohm, 93db sensitivity 

Now for my questions:

Will replacing the factory 4ohm speakers with the infinity’s above give me better sound? I’m hoping for better lows and less mud at reasonable listening levels. 

Will I have to crank up the volume a significant amount to be able to hear anything? This might be a deal breaker and is my biggest worry. I haven’t found much specific info that helps except for one reddit poster who said the headunit couldn’t drive his speakers unless cranked way up. It’s good info but it’s hard to know what people expect as far as volume. I don’t blast music much as I value my hearing. 

I don’t care much about sound in the back seats so I plan to leave those alone. But what about the dash tweeters? They’re 8ohm and in a 3.5” mount. Some replace them with 3.5” 2 way speakers, some put in tweeters, some leave them alone. I’m pretty sure I can balance the door speakers by adjusting the fade but I think the tweeters will be way too loud with those settings.

Learn me with your knowledge and experience  

3ohm is kinda weird.

Really, what determines your sound output of a similarly sized speaker should be sensitivity so I would see if you can find the specs on the stock speakers. That may be easier said than done however.

That makes sense. I’ll see what I can find. 

Does a speakers volume relative to another only dependent on sensitivity? Assuming equal input voltage. 

Not to make a canoe out of this, but have you tried asking audio companies like crutchfeild? My guess is they know these answers and I’ve found their pricing to be pretty competitive given the expertise .....

Not a canoe. 

I haven’t called crutchfield but In searching I did come across some info from them. I was hoping for some hands on experience from someone here. 

spandak said:

That makes sense. I’ll see what I can find. 

Does a speakers volume relative to another only dependent on sensitivity? Assuming equal input voltage. 

That's exactly what sensitivity is meant to represent. Are you open to the idea of changing out your head unit?

In reply to SEADave :

No the headunit must stay. I want the OEM look and interface  

Numbers are your guide.

Your factory head unit puts out 15w at best, and it will attenuate the extreme frequencies at high levels.  The reason is that an in-dash head unit lacks the real estate and heat-shedding ability to be effective at higher outputs.  To make the same dB of 50hz, it takes roughly 10 times the watts as it does at 10,000hz.  The reason is the physical mass of the speaker and forcing it to move at 50hz.  The woofer is very heavy compared to the tweeter.

If you want to keep the factory head unit and don't wish to add an amp, you're simultaneously in luck and screwed.  The speakers that will sound best are likely the less expensive ones, but you are limited by wattage.  It takes wattage to make bass.

Avoid the 3-way speakers.  That is just wasting wattage by splitting it up between high-mid and high frequencies.  Keep it simple.  A good 2-way is fine.  No need to split your wattage through so many drivers.

Here's the thing to look for.  You don't need big magnets or large max wattage.  You need efficiency.  93db/w is a good efficiency, but with a 300w max it makes me think there are big magnets.  That is to say, they might be lying about one or the other spec.  My guess is they are lying about the 300w max, but that is just speculation.  The concept of "max" wattage is also a marketing trick.  Always look at RMS watts.

Match a factory head unit with the most efficient and simplest driver you can.  You won't have much luck improving bass without more wattage, but you can maximize the mids and highs with a good driver.  My suggestion would be THESE

One thing to consider is they've had some innovation in the amplifier category lately and there are these tiny but reasonably powerful amps that will fit almost anywhere. Maybe Crutchfield or the like has a wiring harness for your car where you could wire up something plug and play (no cut wires) to add an amp to your system and then you could get better speakers too.

Here are some of the small amps:

https://www.crutchfield.com/S-DMvGD9J2rdb/cpg/Mini-Amplifiers.html

Sorry you need an amp. Something like this. RD400/4 would be perfect for that car at around 250$. Pickup some speakers int he 100-120$ a set range that fit and go front and rear with them and it will blow you away.

http://www.jlaudio.com/car-audio-amplifiers-rd

My go-to bang for buck speaker right now is the Rockford Fosgate line.  If you keep the HU only, stick with their Prime line.  If you do a small amp, jump up to the Punch series.  If you dive deeper in the rabbit hole with a bigger amp, go with the Power series.

MB Quart, JL, CDT, and Polk's dB speakers are also ones I have used with great success.

I just got THESE for my truck and they will be run off a 2x80w amp.  My last truck had THESE and they really blew my mind with just 60w going to each one.

I know I keep linking to woofersetc's website, but that is mostly because their site is really easy to navigate.  I can't say enough good about Crutchfield, but the woofersetc link might save you $10.