# ACTIVE: tweeter power vs mid woofer pwr?



## corcraft (Nov 16, 2010)

OK, I have searched, researched, called and emailed audiophiles, manufactures and engineers on this question and I have gotten basically 2 different answers but with multiple different reasonings. 

To get this out of the way lets say that the 6.5" midwoofer and the dome tweeter have the same rated sensitivity @ 1w/1m, and are the same distance away from the listener with the same impedance.

Would they need the same power to play at the same level? I have gotten yes because they are the same sensitivity and I have gotten no for multiple reasons but here are 2.

1) you can use less amp power on the tweeter because you can turn the gains up with no clipping due to the low content in the tweeter frequencies.- this doesn't sound right to me. A tweeter clips the same as a woofer with incorrect gain settings right?

2) A tweeter only uses a small amout of the power that you put to them because of the low tweeter content. A 100w tweeter cannot actually handle 100w. I have seen waves and graphs on this and I understand this explanation but....... Does the tweeter still need the 100w amp to get the right amount of power that it needs to keep up with a 100w mid with the same sensitivity?


So the question still is- Does a tweeter and woofer with the same sensitivity need the same amp power to play at the same level? Why or why not?


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## Bayboy (Dec 29, 2010)

100 watts going to any tweeter is going to be loud and overbearing. It makes since about matching wattage, but are you really planning to have your highs that loud? Personally I think you could get away with 50 or less, better yet another tweeter with less power handling.


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## skittlesRgood (Oct 11, 2010)

i wont take a crack at the theories but i took my 3way comp set and made it active. mid range and midbass are on 150w each and the tweeter is on 50w. it sounds great.


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## corcraft (Nov 16, 2010)

Bayboy- would not the mids be as loud as the tweeter w/ the same sensitivity?

Skittles- what's the sensitivity of your mid? Most mids are allot less sensitive than the tweeters so they require less power- every 3db is half or double depending how you look at it. 87db with 100w equals 90db with 50w. 

Now that being said some still say that tweeters need less pwr even w/ the same sensitivity and some say that the need the same. Y or y not?


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## Jmirage (Nov 23, 2010)

I need to look at the sensitivities of my mid vs. tweet, but I am running 250 to the mid and 80 to the tweet on each side. I o-scoped them so my gains are at max without clipping. To balance them, I pulled 7db from the tweeters. I will report back after researching the sensitivity.

Great thread by the way.


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## schmiddr2 (Aug 10, 2009)

This thread might have some info. http://www.diymobileaudio.com/forum/no-question-dumb-forum/87169-75w-active-200w-passive.html


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## corcraft (Nov 16, 2010)

Thanks schmiddr, I posted my question there too b4 I started this thread, lol, I'm watching it too.


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## Jmirage (Nov 23, 2010)

Quote:

Keep in mind, though, that while the loudspeaker system itself is more efficient, if you try to express the efficiency and/or output capability difference in a fixed ratio, you'll fail. It gets a little tricky because the efficiency differences, and subsequently output differences, are dependent upon the efficiency of each driver in the passive design, the nature of compensation in the crossover, the individual drivers' response curves, the signal spectrum, the power supply configuration for the active speaker, the nature of the crossover division in the active system.


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## Bayboy (Dec 29, 2010)

Out of curiosity what speakers you have with similar sensitivity & wattage ratings? With the discussion on the other thread going in the same direction, you really don't have much choice if you want to try feeding both the same unless you want to spend extra on another amp. Either run a 100x 4 amp or if you're trying to apply even more power to the mids then buy an extra amp or switch to a 6 channel.

I have enough in my arsenal to do the separate amp deal but I'd like all matching series for aesthetics. Right now that would be a 50x2 to finish the deal. I may make it happen just to ease the compulsion, but honestly don't think it's necessary.


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## Sarthos (Oct 29, 2010)

It's a long explanation that I don't exactly feel like covering this late at night, too tired... basically no, you can get away with a lot less power on your tweets than on your mids... I'll explain it the best I can here though... if you want a better explanation PM me or something, I'll explain better through like an IM type thing.

To play the same power at the same level, yes they would need equal amps. But you don't need to do that...sorta.

Imagine that you get an RTA and play some pink noise. Pretend you have a 200x2 amp for your mids and a 75x2 amp for your tweeters. Now, tune equalizer with with RTA and playing 40 watts per channel. The gain on the amp for the tweeter will be set higher than the gain on the amp for the mids, but that shouldn't be a problem. At this point, if you turned the stereo up to 100 watts/channel you would clip your tweeter amp. So don't do that.

Now, get rid of the pink noise and play music. What you will see is that when you turn the music up until the mids are receiving 100 watts each, the tweeters probably aren't receiving a full 30 watts each. When you turn it up to 200 watts, your tweeters will be getting less than 60 watts each. So the tweeters won't be clipping. 

Am I making any sense? Basically your tweeters never play the same level as your mids. So if you have the stereo such that they play equal levels on pink noise and perfectly replay the sound, they will never clip on music... I'm rambling, I hate big long typing stuff.


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## kyheng (Jan 31, 2007)

10-20W of clean power to your tweeter are good enough to fry your ears....


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## Sarthos (Oct 29, 2010)

Does anyone know of a good spectrum analyzing program? That's actually the best way to tell what the midbass wattage to treble wattage is..


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## t3sn4f2 (Jan 3, 2007)

BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 1


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## corcraft (Nov 16, 2010)

Bayboy, the speakers that I'm using are the same sensitivity (91db) but not necessarily the same wattage rating. I have 5 matching (2 4ch & 3 2ch) amps and a ms8 and I trying to make sure that I run them the best way to not waste allot of power like on the tweeters- if I over pwr the tweeters I would be wasting pwr there and if I under power them I would be wasting pwr on the mids by having to turn the mid gains down. My amps are 2 75x4 and 3 150x2. I'm putting 2 of the 2ch on subs and the rest is what I'm trying to get worked out. I will prob do a 2ch to the doors, a 4ch to the tweeters and cc, let the ms8 do the rears and leave an amp out. There's so many ways that I could do it but it looks like this way should work out the best. I was going to bridge a 4ch to the doors and run a 2ch to the tweeters but I don't think I'll be needing that much pwr and ild rather keep it at 4ohm.

Sarthos, that makes allot of sense! It goes along with what I had wrote up top on the 1) but it made sense out of it. I planned on setting my gains by the mini amp or piezo method but from what you explained I think I'll set the mid by 1 of these methods at 0db and just bring the tweeter amp up to match by ear then let the ms8 do the rest. Which after I get the gains set ill have to turn them down to match the rears and back up again affter the setup is complete. Does this make sense or would u do it a different way?


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## vlaoo (Oct 31, 2012)

This is a late reply, but I just want to say that higher frequencies need less power to make the SPL. When you input signal through an amplifier, higher frequencies put less strain on the amp, so the amp isn't putting out as much power as when it sees low frequencies. So, you get different power output levels with different frequencies. Lets say you have a 10,000Hz signal. You put it through a tweeter and you register 10 watts. Then you put that signal through a 15 inch woofer and you get... 0 watts. So in short, the higher the frequency, the less power it is needed to produce a desired SPL. It's just physics. For example, the hi-hat on a drum kit produces the highest frequencies but it's smaller compared to the bass drum and it only needs a tap with a drum stick to be heard, while you need a pedal and your foot to produce audible bass notes with the bass drum. Low freq. need to move a lot of air to produce high SPL. Speakers' SPL is usually measured by feeding them with 1 watt of power and the appropriate freq. and the noise is measured with a microphone positioned 1 meter away from the speaker. So for a good speaker system, you need your different freq. speakers to sound equally loud with the same amount of power. So you see, you set your amp at a certain level, but each of your two speakers gets different power, provided you've installed a filter (otherwise the low freqs. would destroy the tweeter), and yet they both sound equally loud. Magic


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## 04silverz (May 28, 2008)

I love when threads have good links posted in them. Provides me lots of free reading material when I'm on break at work


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