# high/mid/low power ratio



## 02xblazer (Jan 10, 2009)

for u guys running active is the a certain ratio of power you use?


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## kyheng (Jan 31, 2007)

What my guru told me :
2-way front : 1-10-100
3-way front : 1-2-4-8


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## 2500hd06 (Oct 13, 2008)

kyheng said:


> 2-way front : 1-10-100


I'm assuming you mean 1-10-10. If not, that would make for one badass subsection!

Anyone else have an opinion on this? Curious to see what people consider ideal.


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## m3gunner (Aug 6, 2008)

Wow...

So... if we have 50 watts on the tweeters, we'd need 500 on the mids and 5K on the sub?

I'm liking the other ratio better, but I think they both are based on *required* power rather than real power.

Tweeters tend to have relatively low power requirements to deliver a given SPL. Let's assume that the sensitivity of the drivers are as follows:

Tweeter: 90 dB/1 watt
Mid: 85 dB/1 watt
Woofer: 83 dB/1 watt
Sub: 83 dB/1 watt

In this case, to product 100 dB, here is the required power:

Tweeter: 10 watts
Woofer: 50 watts
Sub: 50 watts

The funny part is that if the tweeter is 3 dB more efficient, the ratios are right... except for the 100... that's a lot of power... 

There is a reality check here... no one puts *one* tweeter in his system, so each of the power requirements would be halved.

Of course, YMMV depending on speaker sensitivity and a pile of other variables (cabin gain, anyone?)... but from a purely mathematical basis, these ratios may work.

For me, I'm running about 1:2 between front stage and sub.


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## kyheng (Jan 31, 2007)

^Basicly, if you have a clean 15W to tweeters, it is more enough to fry our ears. 
As that ratio is a general guide for the level matching(which told by my guru), so I just share it out. 
Alot of factor we must consider, where you stated most of it.


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## 02xblazer (Jan 10, 2009)

for now im planning on going passive with 160x2 to a set of ID ctx65cs and 1000.1 to a pair of IDQ15s sealed.. should get plenty loud and do the trick..
just wondering about goin active tho


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## sqguy (Oct 19, 2005)

so by what u guys have stated 120 to my LPG Tw and to my RS52's would be too much power?


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## MarkZ (Dec 5, 2005)

This has been talked about before...

It depends mostly on crossover points and sensitivities. If your tweeters are more sensitive than your mids, then it stands to reason that they'd need less power to get just as loud. Furthermore, if your tweeter's bandwidth is limited to only a couple octaves of high frequencies, then the power content of the musical signal is typically going to be lower than for lower frequencies or more octaves -- so you'll need less power.

IOW, there's no set rule. 

If you want to make a measurement for a very rough estimate, you could do this. Take an mp3 that's typical of what you listen to. Open it up in an audio program like Cool Edit Pro. Filter it and measure either the "peak" power or peak voltages of the filtered waveform. Try it with filters that correspond to your crossover points. So, for example, you'll filter it from 80-3k for your midrange, and you'll filter it from 20-80 for your sub, etc. Take those values and combine them with the sensitivities of your speakers to construct a ratio.

Here, I'll start.

I loaded up a rock song in Cool Edit Pro. Listed below are the peak values for each filter setting (using 4th order butterworth filters). I don't really like using peak voltages, so I've included "max power" values in parenthesis.

SUB (20-80Hz): -8dB (-12dB)
MIDBASS (80Hz-250Hz): -6.5dB (-14dB)
MIDRANGE (250Hz-3.5kHz): -2dB (-12dB)
TWEETER (4kHz-20kHz): -8dB (-18dB)

So this tells us that the periods of maximum power content, for this song, are about equal for sub and midrange, 2dB less for midbass, and 6dB less for tweeter.

So let's pretend your speakers have sensitivities that look like this (at 1w/1m)...

Tweeter: 91dB
Midrange: 89dB
Midbass: 87dB
Sub: 85dB

Let's ignore issues of cabin gain, how far you are to the speaker, etc. Then your ratio would be somewhere in the ballpark of:

Tweeter: 0dB
Midrange: +6dB power content +2dB sensitivity = +8dB
Midbass:+4dB power content +4dB sensitivity = +8dB
Sub: +6dB power content +6dB sensitivity = +12dB

That translates to approximately...
Tweeter: 1 watt
Midrange: 6 watts
Midbass: 6 watts
Sub: 15 watts

Remember, these are just ballpark numbers derived from a single song and assuming you're listening to speakers out in a field on axis and at equal distances from you. I'm just trying to illustrate a point...


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## MarkZ (Dec 5, 2005)

kyheng said:


> ^Basicly, if you have a clean 15W to tweeters, it is more enough to fry our ears.


Very true. 15w continuous into a tweeter will fry your ears and then probably fry the tweeter. But a tweeter can normally handle dynamics of much more than this. 

When we're sizing amplifiers, remember that we're choosing power ratings to avoid clipping the transients. So we only really care about the transients -- the maximum values. We care NOTHING about the average power a speaker will take (which is what we care about when we're talking about frying ears or voice coils...). So you still should have a fairly sizable amp for your tweeters so that it can handle the dynamics without much effort. Unless they're insanely sensitive...


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## Oliver (Jun 25, 2007)

http://www.diymobileaudio.com/forum/diyma-tutorials/18660-abmolech-talks-power-speakers.html


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## 89grand (Nov 23, 2006)

It's hard to say as any absolute fact. For instance I ran a system with Focal 130k's in the front through the passive crossover with an A200 rated at 50 watts each, then ran 2 JL Audio 10W3's off a bridged A600.2 for 600 watts.

Then one day I swapped amps just for fun and ran the Focals off of 150 watts per channel with just 200 total to the two subs. I much preferred it this way, and left it that way. 200 watts was still enough to get the low end I wanted and the additional power really made a huge difference on the mids.


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## kyheng (Jan 31, 2007)

^Yup, you are right... But there should have some guide on the initial stage of tuning, right? That's why there's a general guide come about.....
The best still let our ears do all the talking...


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