# RMS calculus



## sethwas (Apr 30, 2002)

So, 
In a previous thread I posted about a 'loudness' dilemma front and rear. 

My fronts are 40W RMS. 
My rears are 50W RMS. 

So, if I were to upgrade to 60W RMS front, would that make the fronts louder (at the same 'volume knob' level and fade level)? Or would it make the rears louder since they have the lower RMS? 

Meaning, if I get the 60W RMS, should I put them in front, or back. (Since, again, the 50W is in back, and the 40W in front). 

In otherwords, does RMS make for the louder speaker, or the design? 

Seth 

P.S. The 50W and 60W RMS speakers are Blaupunkt (2 way, and components respectively). The 40W is a panasonic component set. As stated in the other thread I'm trying to balance speaker power without going the amp route. The volume knob just does loudness, not bass, treble balance - which in my case is off.


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## samo (Apr 30, 2002)

Although the power rating has a fair amount to do with the volume level, sensitivity has a lot to do with it as well. It also matters exactly how much power you're feeding those speakers. My fronts are rated at 120w and the rears at 30w RMS, but on the same 35w, the rears are MUCH louder than the fronts. The rears have a sensitivity of 90dB/W/m and the fronts have a sensitivity of, I believe 85dB/W/m. This small difference adds up to a lot of volume difference since the dB scale is logistic.


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## kbrassfi (Aug 1, 2002)

*front v. rear*

If I'm not mistaking from my experience with Car Audio, positioning also plays a big role, your rear speakers are hitting the rear window, which deflects the sound straight at ear lexel, while the door speakers are down by your feet, and usually shoot straight out, unless you can swivel the center, or have a compnent set. I hope this helps a lot, but also the sensitivity plays a big role, I think every 3 points in sensitivity causes you to need twice as much power, or so I have read in my research online. 

SoloBaric S12L7
4 Infinity reference speakers
2 Lexxon Tweeters
Rockford Fosgate series 1 4600 amp (90 x 4)
american legacy 2000 watt amp

I am also planning on upgrading my amp, and putting my two JL's back in the car with the Solo as well


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## sethwas (Apr 30, 2002)

Hey, 
So I'm pretty clear on the theory now, I guess I should have done this before - here are all the numbers to back up my story - that is: 
I have components in the front and plain two ways in the rear. The components are much sharper (decent [for me] tweets on the A pillar/door sill) but have little low range, depth, and punch. The rears are less audible, but have much more punch and low range. I know it takes more power to drive bass, so thats why I had the RMS theories instead of dB. If I am driving, at a constant volume knob the front tweets and rear bass are on one level, and the rear tweets and front mids/woofers are on another. Aside from mixing and matching... 

Anyway, the speakers are like this: 
Front: RMS 150/40, 90dB/w/m, 30Hz-25kHz 
Rear: RMS 150/50, 89dB/W/m, 60Hz-20kHz 
The rears have this additional info: 
92dB (2.83V/m)/89dB/W/m, and of course the Thiele Small parameters. 

The third set of component speakers is this: 
RMS 180/60, 93dB, 65Hz-22kHz 

I don't mind putting components in the rear. Of these three speaker specs, what is a preferred front rear arrangement. I understand staging is better in the rear, so I would prefer a better speaker up front, and a 'lesser' one in rear. 


Seth 

P.S. I don't know if this means anything, but 'on paper' the current components is a tweeter woofer setup, and the possible third set is a tweeter mid setup. Is it just a lable, or is one speaker actually designed for a lower rating. The frequency specs say that 'its all in a name'.


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## Sethticlees (May 30, 2002)

Try a crossover. This should fix all your problems.

Seth


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## Sethticlees (May 30, 2002)

Ah Crap! I double posted.
That's a first.

Here's a funny link to make up for it.

http://forum.oc-forums.com/vb/showthread.php?s=&threadid=110647


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