I'm looking to swap out my h/u in my truck and had a couple units in mind. To make a long story short, I'm running 4 5x7" coaxial speakers off the h/u and no amps. This is the whole system. Both headunits I'm looking at have 50Wx4, but one has 14Wx4 RMS and the other, more expensive one has 22Wx4 RMS. Since there is no external amp will I really notice a difference in overall loudness of the two units?

 

Honestly....if thats all your running your not going to be able to hear any difference at all. as long as you have a good set of speakers...i would say 3way speakers and a decent head unit you should be all set. thats my opinion.. because without an amp or anything your not gonna get near the RMS or continuous amount of power your headunit and speakers are rated at.

 

Why would I not get all of the possible power out of my headunit with no amp?

 

RMS and an amp's power got nothing to do with each other bc they are seperate units........i agree 14 and 22 watts isn't mush difference in terms of listening volume. get the cheaper one and use the xtra money for something else.

 

14Wx4 RMS or 22Wx4 RMS is a joke. IMPO
Get an external good Q amp and call it a day period.

 

HUH??? Amplifier power is measured in continuous (RMS) watts and/or peak watts. Obviously amp power and RMS have something to do with each other.

 

just make sure the rms in the head unit and supply your speakers with the rms they require...otherwise your gonna be stressing your h/u....if you cant match the rms wattage then id say just get a small amp to push the speakers

 

Ssshhhh...quit telling the truth. That's so wrong. LOL

OK. What brand HU are you looking at that is producing, actually I should say "Claiming" to produce 50wx4? Most HU amps can produce 50wx4....if you are testing with-in a very narrow window. I.E. 1k Hz test tone with very low span of about 500 Hz. Non inductive nor reactive load (i.e. Steady state or a plain old resistor) and the power is very clean and probably higher then what would normally be seen in a vehicle. Oh yeah. What is the rated THD at this 50wx4? And is it RMS or Peak or PWMO (or what ever that BS spec is)

Also, realise this, all that above means that the testing to say it produces 50w isn't realistic or conducive to what you would experience real world.

Also, the reason why external amps are larger and produce more sound at an equally rated amount is the amps can produce the 20 Khz span effectively, have better cooling to allow for longer listening times and better performance from the transistors themselves, larger and more efficient components especially critical components like power regulation and better/larger capacitors to handle transients in music much better. In other words, the amplifier is made to handle music, not test tones at the rated output.

In reality, you should choose a HU from a reputable company that has the features you need/want and produces about 15-20W of good RMS/AVG power. The difference to your ears between 14 and 22 watts is not all that much. It will not be twice as loud to your ears. It WILL MEASURE twice as loud though. BUT realise that the better/more expensive HU probably has a MUCH better amplifier then the cheaper one. It will sound better.

Related to car engines, it would be like a peaky turbo I-4 motor with no real power under the curve that produces 400 HP. Sure it measures 400 HP, but compared to a 400 HP V-8 NA that makes 400 HP there is a big difference in the actual speed and acceleration available. Power under the curve. Plus think of it like this too. The support around the I-4 Turbo motor allows it to ONLY make the 400 HP on a dyno with a very lean A/F ratio, race gas and alot of cooling down inbetween runs vs. The V-8 with no real cool down, no race gas and it's AF ratio is set-up for street driving.

 

The cheaper and lower wattage h/u is a Pioneer DEH-P5000UB: http://www.crutchfield.com/App/Produ...ures_and_specs

The more expensive one is a Pioneer DEH-P690UB: http://www.onlinecarstereo.com/CarAu...roductID=18335

They both do what I need them to do...one is just newer and a bit more powerful (and more expensive).

Richie77: I have no idea what THD is so I can't answer your question about that.

 

50wx4 Max Power Output
22wx4 RMS Power Output (50Hz to 15000Hz, 5%THD, 4ohm load, both channels driven.

 

please read post #2 smarty. apparently continuous and RMS are two different things and apparently without an amp you dont get your head units full potential......thats what i was commenting on, i sure wish smartass people would read before they correct someone.

 

Oh, I see...reading a single post in a thread here makes you an expert. Especially when that post didn't make much sense. Be careful, newbie, of name calling when you're totally out of your league.

The statement in post #2 should have had parentheses..."you're not going to get near the RMS (continuous) amount of power". RMS is an acronym for Root Mean Square - a method of calculating average power when it varies between positive and negative amounts. Audio power is the product of current that alternates between positive and negative voltage. The RMS power rating is the amount of power that an amp can produce continuously. With direct current you just measure the voltage and current then multiply them together to get power. With alternating current (including audio output), the voltage varies between a positive amount and the equivalent negative amount so you can't just combine the peaks to get the average because they will total zero. In simplified terms, the RMS voltage of a sine wave is the peak voltage multiplied by the Pythagoras constant (the square root of 2...approximately 1.414). The actual calculation is much more complex because audio isn't a perfect sine wave.

The last part of the sentence in post #2 made absolutely no sense so I assumed it was a typo. "because without an amp or anything your [sic] not gonna get near the RMS or continuous amount of power your headunit and speakers are rated at" is meaningless as written. I think what he was trying to say was that without an external amp the small built-in amp of the head unit would not drive the speakers to their full potential. In other words, the speakers are capable of handling more power than the head unit alone can produce.

 

Then there is the Calculus AVG measurement which is more true. RMS is the Algebraic DC equivilant power (peak by 0.707 x Ppeak). AVG is the Calculus derived average power under the curve and it's algebraic equivilant ~ (0.535 x Ppeak) Those are just quick formula's and don't entirely tell the whole truth. Then it's can get a bit more confusing, but I'll save you all from that.

http://www.ac.wwu.edu/~vawter/Physic...-AvePower.html

Some more reading.
http://en.wikipedia.org/wiki/Equal-loudness_contours

Don't be too concerned with the power output from the HU. The amplifiers are marginal at best compared to regular amplifiers. Just pick the desk with the best features you will use with-in the price range you can afford.

 

anybody can cut and paste, lol. yes it was written incoherently. and yes i am...er was MECP certified. i have no trouble understanding RMS.

 

Gee, I'm so glad I spent all that time in college getting a degree in electronics so that I could cut and paste text trying to explain something to someone who already had an important industry certificate.

 

Given the context of this thread, that scares me...

For original poster: what HU models are you looking at? You may want to choose one based on other features/functionality/appearance rather than the output. You'll probably want to upgrade in the future anyway with the addition of an aftermarket amp. Even if not...the difference in sound you would perceive is small between the two units.

 

The cheaper and lower wattage h/u is a Pioneer DEH-P5000UB: http://www.crutchfield.com/App/Produ...ures_and_specs

The more expensive one is a Pioneer DEH-P690UB: http://www.onlinecarstereo.com/CarAu...roductID=18335

I'm with you on this. I think he needs to not be concerned about the power difference between the 2 decks. I can bet money on this: if I did a double-blind test and just made sure the tester knew what he was doing, he'd hear almost no difference between the 2 decks. If he was very very familiar with a single piece of music he might be able to hear a difference in the transients and dynamics, but that would be it.

Until there is a method of rating that incorporates what happens in music more accurately AND becomes accepted as standard, then it's hard to be able to make informed judgments on rated power. Just looking at the specs that are tested for standard today, it's VERY hard to figure out what amp is better then the other.