Understanding Watts in car audio

[MicraMan]

Hi.

I come with a very begginer question, but the info I found it seems confusing to me. This is not about RMS vs PMPO, this is clear to me.

Let's take the Infinity Reference 6532IX as an example. The webpage says it is 180W (I assume RMS). To know the producible watts per speakers, have I to divide 180W per the square root of 2, which gives me 127, and then divide 127 per 2, because the 127 are the watts of the 2 speakers together?

Did I understand it well?

Click to read more...

 

[dragon.breath 10+ year member]

No. 180w is a peak number. Peak wattage numbers are nothing but advertising nonsense. Ignore them. The real numbers for those speakers is 60 watts rms each.
And if any car audio salesman starts talking about square roots and figuring out speaker wattage, get a running start and kick him in the nads as hard as you possibly can.

https://www.sonicelectronix.com/item-174189-Infinity-Reference-6532IX-REF6532IXAM.html

 

[HardofWhoring]

PMPO is more commonly just known as Peak. Peak is nonsense. Peak is if you didn't care about the quality of the sound in any way, and only wanted to play that music for a second, then you would be concerned about peak.

RMS and ohms are all you need to match up. The same ohms, and RMS the same or slightly larger on the amp, are all anyone really needs to know to put together a system.

RMS means root mean square, and it's how they get to that number, (you don't need to understand how, just use the number). To compare it to something, it's like learning a vehicle's tire size, rear end gearing, transmission gears, throttle percentage, air inlet cfm, exhaust, tire type, aerodynamics, etc.. and all you really want to know is what's the MPG.

Speakers and amps are rated in channels. Each speaker is on one channel, unless were talking about subs or components. A set of (those infinity) speakers is two channels. A 4ch amp, is generally two sets. Components are generally one set, but some can be wired individually. Subs have the most combinations, because they are MONO, and you don't care about playing them in stereo / Left to right / like you would need at least 2 channels for. They can be their own channel depending on the amp, or channels can be combined.

 

[skittlesRgood 10+ year member]

Here's a safe rule if they don't list RMS or if you're unsure what number they are listing. Look at the fuse, if the amp has an onboard fuse. Multiply that number by 12 (for 12v, this will also compensate for efficiency loss since you'll actually be running at 14v), then divide by the number of channels.

 

[metalheadjoe 10+ year member]

Hi.

I come with a very begginer question, but the info I found it seems confusing to me. This is not about RMS vs PMPO, this is clear to me.

Let's take the Infinity Reference 6532IX as an example. The webpage says it is 180W (I assume RMS). To know the producible watts per speakers, have I to divide 180W per the square root of 2, which gives me 127, and then divide 127 per 2, because the 127 are the watts of the 2 speakers together?

Did I understand it well?

I don't think you understand it well, and I don't think anyone on this forum (including myself) understands it well. I was taught that rms=.707 x peak. Car audio almost always lists rms as half of peak. I hope someone can give a clear explanation.

No. 180w is a peak number. Peak wattage numbers are nothing but advertising nonsense. Ignore them. The real numbers for those speakers is 60 watts rms each.
And if any car audio salesman starts talking about square roots and figuring out speaker wattage, get a running start and kick him in the nads as hard as you possibly can.

https://www.sonicelectronix.com/item-174189-Infinity-Reference-6532IX-REF6532IXAM.html

Are you saying that if anyone knows more formulas that you, they must be wrong? Tell my why rms voltage is 70% of peak but rms wattage is 50% of peak. OP asked a great question that I have wondered myself, and you replied without answering.

PMPO is more commonly just known as Peak. Peak is nonsense. Peak is if you didn't care about the quality of the sound in any way, and only wanted to play that music for a second, then you would be concerned about peak.

RMS and ohms are all you need to match up. The same ohms, and RMS the same or slightly larger on the amp, are all anyone really needs to know to put together a system.

RMS means root mean square, and it's how they get to that number, (you don't need to understand how, just use the number). To compare it to something, it's like learning a vehicle's tire size, rear end gearing, transmission gears, throttle percentage, air inlet cfm, exhaust, tire type, aerodynamics, etc.. and all you really want to know is what's the MPG.

Speakers and amps are rated in channels. Each speaker is on one channel, unless were talking about subs or components. A set of (those infinity) speakers is two channels. A 4ch amp, is generally two sets. Components are generally one set, but some can be wired individually. Subs have the most combinations, because they are MONO, and you don't care about playing them in stereo / Left to right / like you would need at least 2 channels for. They can be their own channel depending on the amp, or channels can be combined.

I quoted you because my two other responses are relevant to your comment: Tell my why rms voltage is 70% of peak but rms wattage is 50% of peak. OP asked a great question that I have wondered myself, and you replied without answering.

 

[dragon.breath 10+ year member]

Are you saying that if anyone knows more formulas that you, they must be wrong?

Not at all. But when the rms number is already printed on the back of the box. …..

 

[HardofWhoring]

I don't think you understand it well, and I don't think anyone on this forum (including myself) understands it well. I was taught that rms=.707 x peak. Car audio almost always lists rms as half of peak. I hope someone can give a clear explanation.

Are you saying that if anyone knows more formulas that you, they must be wrong? Tell my why rms voltage is 70% of peak but rms wattage is 50% of peak. OP asked a great question that I have wondered myself, and you replied without answering.

I quoted you because my two other responses are relevant to your comment: Tell my why rms voltage is 70% of peak but rms wattage is 50% of peak. OP asked a great question that I have wondered myself, and you replied without answering.

RMS wattage is not 50% of peak. It works out that way pretty often, but that's never guaranteed. Even the OP's example is 60w RMS and 180W peak.

PEAK is the measurement of the max wattage a speaker/amp can play for ONE SECOND with no consideration for THD (actual rating). It's useless, and just an irrelevant number that looks cool on the box.

RMS is the measurement at 14.4v with no more than 1% THD @4 ohms. That is the CEA-2006 rating, and a pretty crappy rating, but it gives plenty of room for everyone to be on the same page. They should also do that rating at .1-.25% THD.

I don't know where you got RMS voltage is 70% of peak. I've never heard that. I know only 14.4v is the standardized rating, but 12V is engine off. 14.4v is 20% more than 12v, and not everyone is running stereos while driving in their vehicle. That's as close as I can get to that. We're pretty far apart on that right now. Maybe something has a different Ohm rating?

The OP's question is nonsense. They got a few things confused and jumbled up. The square root is part of figuring out RMS. Root Mean Square. I know it enough to know I don't need to know it completely. That one still throws me off, but it's more or less the ideal median of how loud a speaker will get based on power input with no more than 1%THD, (usually a lot less than that, and I think they could adjust that number depending on how they wanted to market it). They can go louder with more power than RMS, but it's diminishing return, and you can cause more THD. If you had 15 batteries, and 10 alts, then then go ahead and put more in the speakers. When you are wrestling with will you need to add an extra battery or larger alt for a couple hundred watts, is that really worth it?


Maybe there was another question to keep it going? I'm not a professional, or educated in any way on technical aspects, just someone that learned the basics early on, and kept learning. Had a shop do mine a long time ago, and wanted to go punch em in the face when they "finished". Redid all their crap, and vowed to not ever pay anyone again to do my stereo work.

 

[shredder2]

There's always another way to keep the discussion going... Lol.
Ok folks, consider how 100w rms can fill the house with big sound. Also consider +1500 w in the car vs your 100w home audio system. I think the ground floor of noise is the determining factor unless you overpower the noise and... Voila'... You got car audio pretty much pigeonholed.
Oh we all seek quality, low price and hi power but how much does the things like noise floor and deadining factor in?
Asking for a friend....

 

[hispls 5,000+ posts]

RMS and PEAK in the context of any of this stuff is all marketing ********. RMS is only the statistical method to figure out an average amplitude (distance from zero).

Someone come along and show me one household appliance that says "165V peak" or "120V RMS" on it. Of course you can't because the RMS is implied and is the number you get when you plug in your voltmeter because that is the DC voltage that you would get if you built a rectifier to turn the AC signal with 165V + and - peaks into a DC power supply to do some sort of work for you.

https://www.statisticshowto.com/quadratic-mean/

 

[MicraMan]

Well guys, I just need how to know the RMS of different speakers set I am considering, which is very difficult as most of the speakers I saw they stated something like 120, 150 or 200W, and I don't understand if those watts have to be divided per 2 because they are 2 speakers, or if those watts are PMPO and have to be converted to RMS, or what they are.

No. 180w is a peak number. Peak wattage numbers are nothing but advertising nonsense. Ignore them. The real numbers for those speakers is 60 watts rms each.
And if any car audio salesman starts talking about square roots and figuring out speaker wattage, get a running start and kick him in the nads as hard as you possibly can.

https://www.sonicelectronix.com/item-174189-Infinity-Reference-6532IX-REF6532IXAM.html

Curiously, the RMS watts are the same after applying the maths I propossed in my post. Is this a coincidence?

Here's a safe rule if they don't list RMS or if you're unsure what number they are listing. Look at the fuse, if the amp has an onboard fuse. Multiply that number by 12 (for 12v, this will also compensate for efficiency loss since you'll actually be running at 14v), then divide by the number of channels.

It's good to know this, but I don't have the speakers with me. What I need is to know the RMS of speakers before buying them, and what I ask is the meaning of the high value of between 120 and 200W I see in the name of the speakers. Are they the sumof the RMS of both speakers? are PMPO?

The OP's question is nonsense. They got a few things confused and jumbled up. The square root is part of figuring out RMS. Root Mean Square. I know it enough to know I don't need to know it completely.

Nonsense or not, you are not answering it. You are just saying something I actually said it in my first post: the importance of RMS to know if the speakers fits well or not. I knew that. What I don't know if there is a fast way to know the RMS when all I see are speakers of around 150W, and I don't know if they refer at the sum of both speakers, or to what they refer. Can you answer that, as this was my question?

 

[HardofWhoring]

Ratings are given per speaker/ per channel. Whether you see those ratings in peak or RMS, they are giving you the ratings for each speaker/each channel. For those 6532ix you listed, the matching amp would be 60w @ 4ohms x 2 ch.

 

[MicraMan]

Ratings are given per speaker/ per channel. Whether you see those ratings in peak or RMS, they are giving you the ratings for each speaker/each channel. For those 6532ix you listed, the matching amp would be 60w @ 4ohms x 2 ch.

Ok, so the one's stating 200W are surely talking about PMPO, as those 200W is for each channel.

Well, I still can't know (nor imagine) the RMS without entering into detailed specification, or having to visit the manufacturer webpage, but at least have some more info.

Quick question: in HiFi, the amplifier can match, in most scenarios the impedance of the speakers. Does also works like this in CarAudio when you only rely on the radio? Do I need to search for the exactly same ohms of my radio?

 

[spokey9]

Very few radios are stable below rated impedance...you can go higher but lose power output...

 

[MicraMan]

Very few radios are stable below rated impedance...you can go higher but lose power output...

I am definetly going for the exact ohms my radio says it wants. Looking at the specs ( https://www.indiamart.com/proddetai...er-with-bluetooth-technology-19736891388.html ) it says is 4 ohms/1Khz/16V, so no question with ohms. The question now is what those 1 Khz means. Can someone explain it please?

 

[dragon.breath 10+ year member]

1khz is the frequency of the test tone. The 55 x 4 is a peak number. The rms wattage on most Sony head units is 17 watts per channel.

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