Are watts cumulative?

[Lowrdr 10+ year member]

Hi,

I am putting together a modest system for my boat; I am new to car audio so please bear with me. I hope this is a simple question.

Say for instance your head unit puts out 25w X 4 RMS and your amp puts out 75w X 4 RMS am I getting more like 100w X 4 RMS to the speakers?

Thanks

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[kr15 5,000+ posts]

If you amp is hooked up and running your speakers, you will ONLY get the amps power

 

[Lowrdr 10+ year member]

Simple enough, thanks!

 

[Bettr n' Revrse 5,000+ posts]

Yes ^^^ you dont use both of them

 

[whitedragon551 5,000+ posts]

Yes and no.

In the situation you described they are not. If your strapping two amps though then by definition of cumulative then yes.

 

[Lowrdr 10+ year member]

So if your plan is to incorporate an amp into your system and that is what will determine the output to the speakers does that make the head unit's output less of a consideration or is there still benefit in a higher watt rating feeding your amp? It would seem to me pay the extra on the amps' wattage and not the head units' wattage, thoughts?

Thanks

 

[SicAudio 5,000+ posts]

don't confuse the poor guy WD lol he said he was "new" he has no clue what "strapping" is yet lol

 

[whitedragon551 5,000+ posts]

So if your plan is to incorporate an amp into your system and that is what will determine the output to the speakers does that make the head unit's output less of a consideration or is there still benefit in a higher watt rating feeding your amp? It would seem to me pay the extra on the amps' wattage and not the head units' wattage, thoughts?
Thanks

HU watts are irrelevant. They are only important if you plan to use rear fill and dont want to amp the rear fill or use it for tweeters. I look more at the quality, preout voltage, time alignment, EQ, active capabilities, features in general and SQ.

Since your new just look for a HU that has the features you want. You have ALOT and I mean ALOT of reading to do if you plan on being serious about this.

 

[Lowrdr 10+ year member]

Yes and no.
In the situation you described they are not. If your strapping two amps though then by definition of cumulative then yes.

Understood, thanks.

 

[SicAudio 5,000+ posts]

So if your plan is to incorporate an amp into your system and that is what will determine the output to the speakers does that make the head unit's output less of a consideration or is there still benefit in a higher watt rating feeding your amp? It would seem to me pay the extra on the amps' wattage and not the head units' wattage, thoughts?
Thanks

when using an amplifier the key feature is the RCA voltage. the rms rating of the deck becomes a moot rating when using an amp..

I personally will not use any that are not at least 4 volt RCA...

 

[whitedragon551 5,000+ posts]

when using an amplifier the key feature is the RCA voltage. the rms rating of the deck becomes a moot rating when using an amp..
I personally will not use any that are not at least 4 volt RCA...

I wont either, but its really personal preference. If your amps arent of cheap quality then preout voltage is irrelevant. If anything it may or may not prolong the life of your amp due to lower gain settings and lower noise floor resulting in less heat being produced.

 

[SicAudio 5,000+ posts]

regardless of amp quality, a higher voltage preout is and had been proven to be a cleaner signal.

if it was not they would not have them //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[whitedragon551 5,000+ posts]

regardless of amp quality, a higher voltage preout is and had been proven to be a cleaner signal.
if it was not they would not have them //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Some of the oldest SQ Alpine HU's had a 400mv preout and Id put them up against any 4v, 5v, or 8v HU on the market today. There was a thread awhile back. Im trying to find it.

Heres one of them though, not the one I was looking for:

http://www.caraudio.com/forums/amplifiers/206351-why-gain-setting.html

Does HU preamp voltage matter? This question gets thrown around a lot and all too often, the answer given is “more is better.” Without any other information, this can’t be categorically stated as fact. A lot of the tests that I have seen for HUs with rated 4V outputs found that the HU simply didn’t make its rated voltage without unacceptable levels of distortion (10% in many cases) and/or without the bass or treble levels maxed out and then it only mad ethe rated voltage at the center freq of the boost. A HU with higher pre-out voltage won’t necessarily sound any better or allow a higher output from the amps. The fact is that the max pre-out voltage is only ever seen with the volume at max with a 0dB sine wave. If the volume is less than max or the level of the recording is less than 0dB (pretty much all music is well below that level) then the spec is meaningless. Combine that with the fact that most all amps will make their rated power with as little as 250mV and you can see that this spec isn’t that important. The only real benefit to a higher voltage signal is allowing the amp gain to be set to a lower setting and increasing the ratio of the signal to the inherent noise floor of the system. With good components, this noise floor is inaudible (the S/N spec is cited referenced to 1W, it increases from there) even with the amp gains maxed. HU preamp voltage is pretty much the last thing I look for in a good source unit. Outputs that don’t clip at max volume are much more important, and much harder to come by. For the purposes of being noise free, low output impedance is much more important than the rated voltage (which you’ll never see anyway).

 

[Lowrdr 10+ year member]

Hey, while you're all being so helpful perhaps another trip to the well. I have been doing a lot of reading so that I make somewhat informed decision and I'm afraid it usually raises more questions with me than answers; sigh.

Anyway, one thing I am trying to make sure is that I match the speaker's wattage to the amps' wattage having read that under or over powering these can be harmful. Is there an accepted +/- margin or rule-of-thumb regarding acceptable ranges for safe operation?

and thanks, I do appreciate your time in responding.

 

[whitedragon551 5,000+ posts]

Hey, while you're all being so helpful perhaps another trip to the well. I have been doing a lot of reading so that I make somewhat informed decision and I'm afraid it usually raises more questions with me than answers; sigh.
Anyway, one thing I am trying to make sure is that I match the speaker's wattage to the amps' wattage having read that under or over powering these can be harmful. Is there an accepted +/- margin or rule-of-thumb regarding acceptable ranges for safe operation?

and thanks, I do appreciate your time in responding.

Underpowering a speaker doesnt damage a speaker EVER. Clipping damages speakers.

Clipping (audio) - Wikipedia, the free encyclopedia

I would also strongly suggest you read through this site:

Basic Car Audio Electronics

Section 29 is the section about underpowering and clipping.