# Abmolech talks power to speakers!!



## Oliver (Jun 25, 2007)

Abmolech, excerpt about power, power as it relates to speakers 

The reason for so many watts is to allow for dynamic range. If your listening to 80 dB at 1 kHz (not unusual in a moving car) then you require around 86 watts at 80 Hz. 
So 1 watts without allowing dynamic range.

0 dB increase = same power, therefore 1 watt 
3 dB increase = 2 x power, therefore 2 watts 
10 dB increase = 10 x power, therefore 10 watts 
20 dB increase = 100 x power, therefore 100 watts 
30 dB increase = 1000 x power, therefore 1000 watts 
40 dB increase = 10,000 x power, therefore 10,000 watts. 


Therefore if your music has only 20 dB dynamic range you require only 100 watts. (Assuming you box volume is not too small)

At this point, if you have 6.5 " mid bass, your running out of xmax (103 dB requires about 10 mm, with a proper baffle 109 dB @ 80 Hz) 

If you have an 8" mid bass your 112 dB or 118 dB with a baffle at 10 mm xmax, requiring requiring about 400 watts to get there (26 dB increase) 

Point
There is no free lunch

Remember I have not allowed for loss..
Power compression AKA heat, which will drive these figures considerably higher.
Loss by using a small box volume
Passive crossovers (about 3- 6 dB loss)
EQ boosting of frequencies (3 dB boost requires twice the wattage)

If you complain your drivers are more efficient than 86 dB at 1 watt, your fooled by marketing, because as soon as you start using the driver heat induces resistance, and your efficiency plummets. (Remember 95 % of the energy is lost to heat in a driver, as soon as you start using any real loudness level, power compression is going to take its toll)

350 watts in my opinion is about right for a 6.5 driver.


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## npdang (Jul 29, 2005)

Let me add to this. Most 6.5" drivers you see will quite easily fail both thermally and mechanically with a continuous 100w power. Depending on both the length of time driven, and the frequency. 

Dynamic range is great, but bear in mind some if not many people can't hear a difference between a compressed/clipped dynamic peak and one that isn't because it's such a brief period of time. Also, many amps are capable of significantly higher burst levels than their cont. power rating. And lastly, music is generally so compressed these days you don't need an amp capable of such a wide dynamic range.

Imho, you can certainly do fine with 50-75 wpc amp on your fronstage... provided your drivers arent buried in the car, you have loud environmental noise, or you have hearing damage/grossly inefficient drivers.


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## thechris (Jun 26, 2005)

0.1W = -10dB
0.01W = -20dB
0.001W = -30dB

so long as the amp can play signals lower then one watt, i'd say it'd have a pretty high dynamic range! 

I think you are looking for "crest factor", or ratio of peak to average. (where "rms" power is average power).

increases to headroom typically mean large decreases in efficiency.


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## Guest (Aug 25, 2007)

thechris said:


> 0.1W = -10dB
> 0.01W = -20dB
> 0.001W = -30dB
> 
> ...


agreed ... it seems to me that the original post is confusing _crest factor_ with _dynamic range_  two very, VERY different things. Crest factor, as stated correctly in _this_ post, is the ratio of peak-to-average power.

By the way ... we all know that the term "rms power" is meaningless, right?  

The terms "rms voltage" and "rms current" do, however, have real meaning. They are used in the calculation of _average_ ... NOT _rms_ ... power


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## Abmolech (Nov 2, 2006)

Dynamic range defines the range of a system ability to respond to a signal of amplitudes and measure accurately. Accurate measurement of a signal depends on the dynamic range and the overall level of the data acquisition system. The overall level setting may be thought of as determining the largest signal that can be measured. 

This clearly depends on the present gain setting. That is, the overall level is related to the gain. Clearly if the overall level is too small (gain too high) then the signal will be clipped and we will have poor quality data. The dynamic range then sets the given overall level, what is the smallest signal we can measure accurately whilst simultaneously measuring the large signal. 

For example, suppose we have an artificial signal which consists of a sine wave at a large amplitude A for the first half and that this is followed by a sine wave with a small amplitude a for the second half. We will set the gain (the overall level) to allow the best measurement of the A sine wave. The dynamic range tells us how small a may be so we can also measure that without changing settings. (Actually what we have is three signals, the two sine waves (A + a) plus the noise generated by the measurement system. This noise is always present. Whilst it has little apparent effect on A it clearly sets how small a may be) 

Dynamic range therefore = 20 log * (RMS of the noise level)/RMS of the maximum input (All in decibels) 

Dynamic range measurement is therefore carried out at a specific gain setting. (Usually at a gain of 1) Often RMS based overall levels are preferred, typically the ratio between the peak of a signal and the RMS level. Thus, crest factor specifies the dynamic range of a true RMS instrument. The setting of the overall level (the gain) determines the maximum signal input level and the dynamic range specifies the amplitude range of the signals we measure. 

The measurement system you proposed is for measuring loudness levels on a recording, the one I am using is loudness level on playback (IE a power amplifier gain setting)


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## MiniVanMan (Jun 28, 2005)

werewolf said:


> The terms "rms voltage" and "rms current" do, however, have real meaning. They are used in the calculation of _average_ ... NOT _rms_ ... power


You know, I am soooooo glad you said that. For the longest time, I thought I was missing something. I learned electronics through military training, so my grasp is very practical application, unlike college where it's gone into in much more depth. So, having never heard the term RMS power, I just thought it was left out of the curriculum the military taught me. :blush:


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## Guest (Aug 27, 2007)

MiniVanMan said:


> You know, I am soooooo glad you said that. For the longest time, I thought I was missing something. I learned electronics through military training, so my grasp is very practical application, unlike college where it's gone into in much more depth. So, having never heard the term RMS power, I just thought it was left out of the curriculum the military taught me. :blush:


LOL!

Nope ... sadly, the term "rms power" is completely made-up by some amplifier marketing department ...

It's _average_ power we're interested in ... it's _average_ power that heats up resistors. The "rms" quantities of voltage and current are so-defined, in order to make calculations of _average power_ easy.


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## demon2091tb (May 30, 2005)

Hic just wanted to say your doing a great job at adding to and making the tutorial section alot more in depth and i appreciate it myself.


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## kimokalihi (May 27, 2007)

So when I'm buying and amp and I want to know what the average power rating is, what do I look for? Instead of RMS. Continuous rated power? Nominal?


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## Oliver (Jun 25, 2007)

Thanx demon2091tb  

Np, thanks for the insight !

I just love it when someone learns something, and the "brains" we have here just put me in total awe.

So, I'm always looking for some way to get them to illuminate the darkness we all seem to wander around in  

Thank You very much Werewolf !

Thank you very much Abmolech for your insights !


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## MarkZ (Dec 5, 2005)

kimokalihi said:


> So when I'm buying and amp and I want to know what the average power rating is, what do I look for? Instead of RMS. Continuous rated power? Nominal?


It goes by a variety of names. Even though it's an incorrect term, many audio manufacturers still insist on calling it "RMS power". Whenever you see "RMS power", consider it average power, because if you actually calculated the RMS power it would have no useful meaning. If I was a sneaky manufacturer, I'd call it RMS power but truly give the RMS power rating, which is higher than the average power for the same amp. 

What's even worse than "RMS power" is "peak power". There's no way of telling what the hell they mean by that. Sometimes they're referring to reserve power. Sometimes they merely double the average power rating and say that's "peak power", which would reflect the power content of a square wave, not including losses. Others claim that the "peak power" is merely the product of the peak voltage and peak current of a wave, but since power is a time rate of energy, you can't really do that computation and have it give you anything useful. For those of you who are calculus-savvy, it would describe your integration time window approaching zero.

Manufacturers should just start rating amps by their rail voltage at different impedances like the Zed amps do. Call it "voltage swing" or something. Then all that nonsense goes out the window.


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## cvjoint (Mar 10, 2006)

I would be very interested to learn about the correlation between wattage and frequency. Take for example a dual 6 inch setup where one driver is used as a midrange and one plays midbass. Is the midrange driver now more efficient at 200hz up then if it played a wider range...say 80hz up? Why do tweeters only see 10w when matched with a woofer while on the frequncy response sheet is just a bit more sensitive? And lastly can we get a tree list like the first post with corresponding levels :blush:


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## durwood (Mar 7, 2007)

MarkZ said:


> Others claim that the "peak power" is merely the product of the peak voltage and peak current of a wave, but since power is a time rate of energy, you can't really do that computation and have it give you anything useful. For those of you who are calculus-savvy, it would describe your integration time window approaching zero.


Exactly, or you could just call it area under the curve.
http://www.mathwords.com/a/area_under_a_curve.htm

It gets very complex when you no longer have a simple wave form like a sine wave test tone and are talking about dynamic music.



cvjoint said:


> And lastly can we get a tree list like the first post with corresponding levels :blush:


*Disclaimer:*
I'm attaching this as a guideline, but there so many other things that affect these numbers, wave guides, baffles, distance of you from the driver, equal loudness curves, cabin gain, other losses/gains, excursion, etc...

This only looks at it from power vs sensitivity standpoint (and sensitivity might be measured at a frequency the dirver is not even used at). It does not mean a speaker can actually play that loud if it runs out of excursion, you exceed thermal limitations fo a speaker or other factors I have listed.

Two threads that talk about some limting factors such as excursion
http://www.diymobileaudio.com/forum/showthread.php?t=9094
http://www.diymobileaudio.com/forum/showthread.php?t=17889


Pick a desired level for each speaker say 100db, and see how much power it would take for it to play that loud.


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## cvjoint (Mar 10, 2006)

Allright, so let me see if I get this right. The key word here seems to be displacement, lower frequencies need more...therefore more power to reach that kind of excursion. 

Other than subwoofers the FR graphs don't seem to be upward sloping. Why does a mid have the same sensitivity at 300hz and at 2khz?


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## Oliver (Jun 25, 2007)

cvjoint said:


> I would be very interested to learn about the correlation between wattage and frequency. Take for example a dual 6 inch setup where one driver is used as a midrange and one plays midbass. Is the midrange driver now more efficient at 200hz up then if it played a wider range...say 80hz up? Why do tweeters only see 10w when matched with a woofer while on the frequncy response sheet is just a bit more sensitive? And lastly can we get a tree list like the first post with corresponding levels :blush:


CVjoint, The sensitivity of a speaker is how the speaker is designed, horns are very sensitive, subwoofers can be very insensitive.

If you ask less of a speaker, [ raise the bottom end up that you are asking it to reproduce ], it will play the higher frequencies with less power required and do it with a renewed vigor, [ it will sound better ].

Tweeters produce shorter wavelengths and require less energy to do so, their xmax is much lower than a subwoofers because their frequency is much shorter in length than the notes reproduced by a sub.


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## npdang (Jul 29, 2005)

cvjoint said:


> I would be very interested to learn about the correlation between wattage and frequency. Take for example a dual 6 inch setup where one driver is used as a midrange and one plays midbass. Is the midrange driver now more efficient at 200hz up then if it played a wider range...say 80hz up? Why do tweeters only see 10w when matched with a woofer while on the frequncy response sheet is just a bit more sensitive? And lastly can we get a tree list like the first post with corresponding levels :blush:


You're confusing two separate things, loudspeaker sensitivity and input signal.

If you're reproducing a bass guitar, why should the tweeters be seeing much, if any power regardless of their rated sensitivity? Most music in general simply doesn't have a lot of high amplitude, high frequency content (think fletcher munson). 

We also don't want to hear everything at equal loudness, we just want the speaker to reproduce what's on the recording and not exagerate or under emphasize any frequencies.


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## Kenny Bania (Aug 1, 2007)

Does the CEA2006 Standard help us out at all in terms of cross-referencing amp power?


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## Oliver (Jun 25, 2007)

Kenny Bania said:


> Does the CEA2006 Standard help us out at all in terms of cross-referencing amp power?


Yes, it allows you to compare apples to apples  

The amplifiers of yesteryear were built to different standards, they had to be strong and sound good doing it/price not an issue!

Today, the amps have to be cheap, have to be cheap, have to be cheap!!, and 2006 compliant


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## 8675309 (Jan 8, 2007)

Great post


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## 2DEEP2 (Jul 9, 2007)

Hic said:


> Yes, it allows you to compare apples to apples
> 
> The amplifiers of yesteryear were built to different standards, they had to be strong and sound good doing it/price not an issue!
> 
> Today, the amps have to be cheap, have to be cheap, have to be cheap!!, and 2006 compliant



 LOL 

Somebody slap him, he must run on windows


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## cvjoint (Mar 10, 2006)

npdang said:


> You're confusing two separate things, loudspeaker sensitivity and input signal.
> 
> If you're reproducing a bass guitar, why should the tweeters be seeing much, if any power regardless of their rated sensitivity? Most music in general simply doesn't have a lot of high amplitude, high frequency content (think fletcher munson).
> 
> We also don't want to hear everything at equal loudness, we just want the speaker to reproduce what's on the recording and not exagerate or under emphasize any frequencies.


So tweeters only see a small fraction of the overall power because of the low tweeter content and nothing else correct? Just to get sensitivity out of the way: let's assume a tweeter is 90 db sensitive and the mid is 87db. I would not need 50w for the tweeter to match the 100w amp the mid uses because I can simply turn the gain up on the tweeter amp without issues of amplifier clipping due to low content in that frequency band.


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## chad (Jun 30, 2005)

cvjoint said:


> So tweeters only see a small fraction of the overall power because of the low tweeter content and nothing else correct? Just to get sensitivity out of the way: let's assume a tweeter is 90 db sensitive and the mid is 87db. I would not need 50w for the tweeter to match the 100w amp the mid uses because I can simply turn the gain up on the tweeter amp without issues of amplifier clipping due to low content in that frequency band.


Correct, the power content of HF information is rather low.


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## Oliver (Jun 25, 2007)

good info .... bump !


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## benny (Apr 7, 2008)

Threads like this brought me here! Wish I had more to add.


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## Oliver (Jun 25, 2007)

bumpage ^^6


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## Oliver (Jun 25, 2007)

bump for the people who have joined in the last 30 seconds


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## qstarin (Mar 25, 2009)

Second time I've read this due to a bump. Both times I've found new info I didn't previously know.


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## falkenbd (Aug 16, 2008)

instead of bumping every few weeks why don't we make a thread that has links to all of the threads like this and then get that thread made into a sticky?


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## qstarin (Mar 25, 2009)

Like this one?

http://www.diymobileaudio.com/forum/diyma-tutorials/37931-important-technical-threads-list.html


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## falkenbd (Aug 16, 2008)

qstarin said:


> Like this one?
> 
> http://www.diymobileaudio.com/forum/diyma-tutorials/37931-important-technical-threads-list.html


exactly, I refer to that thread all the time. Maybe it should be made a sticky?


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## qstarin (Mar 25, 2009)

that one is a sticky. Actually, its the only sticky in the tutorials section.


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## rexxxlo (Apr 14, 2009)

good stuff here i wish i could sort through all the rest of the net and posts like this one im making to get this good type of stuff


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## methmurda (Jan 28, 2008)

Although some of this made my head hurt. This info is very helpful, dont have anything to contribute to this type of thread yet, but the more I learn from you guys the better my understanding on this whole sq thing is really about.


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## Oliver (Jun 25, 2007)

To The Top


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## huckorris (Sep 2, 2009)

I really wish more manufacturers would give a FR graph. It's nice to have to supplement ear tuning. Most people on here have drivers that include FR's, but really, how hard is it to throw a graph in the box? I'm disappointed with Cadence for that, and not providing a real spec sheet. I wish I at least had the Qts. so I could better accommodate their install. I guess you get what you pay for ($80). That's just about my biggest objective gripe about my txc-6k's.

I really like how CDT states the power handling @ what HP setting..


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## PR1M3R (Oct 16, 2009)

Nice read. I have read this twice now, and will have to read a few more times. But I am learning!!

Up for my fellow nooblet's


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## emilimo701 (Aug 1, 2010)

a$$hole said:


> 0 dB increase = same power, therefore 1 watt
> 3 dB increase = *2 x power, therefore 2 watts *
> 10 dB increase = 10 x power, therefore 10 watts
> 20 dB increase = 100 x power, therefore 100 watts
> ...


correction, 3 dB increase = ~1.995 x power, therefore ~1.995 watts :smart:


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## TREETOP (Feb 11, 2009)

emilimo701 said:


> correction, 3 dB increase = ~1.995 x power, therefore ~1.995 watts :smart:


Yeah, we call that "2" here in this place we call "real life".


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## emilimo701 (Aug 1, 2010)

TREETOP said:


> Yeah, we call that "2" here in this place we call "real life".


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## slade1274 (Mar 25, 2008)

emilimo701 said:


> correction, 3 dB increase = ~1.995 x power, therefore ~1.995 watts :smart:





TREETOP said:


> Yeah, we call that "2" here in this place we call "real life".





emilimo701 said:


>







Bumping an ancient post to bolster your count to give a .005 correction is more cause for the


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## Oliver (Jun 25, 2007)

emilimo701 said:


>


I've got something to sell to you


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## emilimo701 (Aug 1, 2010)

a$$hole said:


> I've got something to sell to you


ooh! what!


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## cvjoint (Mar 10, 2006)

I think the first post of this thread hits at the heart of car audio's difficulty. Most esque guys stress so much on where their tweeters and mids lie when in fact, to get good sound one first needs to address the issue of weak midbass. 

If you must absolutely have good midbass in a door look no lower than a 10". Run the numbers on this, once you factor in actual sensitivity of your speaker in the midbass range, how little power you give it, and how hot it gets, it quickly becomes puny output. Then you should think about what range road noise comes in at...you guessed it. Test road noise c weighted or no weight, not A weight. 

Of course you don't actually need to have midbass in the doors, you could just run the sub LP higher. The trunk provides plenty of room to work with and to build a solid baffle. Human appendages know as ears have a hard time localizing frequencies in the midbass region, certainly bellow 200hz. But then it's not esque, one must stick a puny sub in the passenger's foot well to hold the esque title.

*I guess I forgot to mention how the BL curve is not flat up to the xmax point, how the voltage can drop under load, and just how much material there is in the midbass region.


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## corcraft (Nov 16, 2010)

Bump!!!! Just what I needed to read- I was about to waste a 200w amp on my tweeters because I'm using 200w on my mids and they're the same sensitivity..... I spent countless hours searching for why a tweeter with the same sensitivity didn't need the same power..... Finally found the answer!


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## adrenalinejunkie (Oct 17, 2010)

Bump for a good read.


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