# Tweeter Power vs Woofer Power



## ajsmcs (Jan 26, 2015)

I've done a lot of searching trying to find this answer, both on this forum and elsewhere, and I haven't found anything I've been satisfied with. I'm sure there's probably a million threads I missed, but at this point its easier to just ask.

It seems that, intuitively, a tweeter would require less power than a woofer to achieve the same SPL because a tweeter has a lot less moving mass than a woofer. More mass=more power to move. Its also moving a larger volume of air, which again takes more power.

The same goes between a woofer and a subwoofer. Subwoofer = much larger moving mass moving much more air = much more power. (although there's also the added fact that the sub-bass region actually needs more power in general just to be audible.

I guess the part I really don't understand is the correlation between audio frequency and electrical power. In other words, do the lower frequencies actually contain more energy than the higher frequencies?

Take for example a passive component set. Let's use the JBL P660-C as an example. (Mainly because I'm getting a set of those in the mail on monday)

You get the following:
*Frequency Response* 45Hz–23kHz
*Sensitivity([email protected])* 94dB
*Power Handling (Peak) * 270W
*Power Handling (RMS) * 90W`
*Nominal Impedance* 2 ohms

You run a set of those using the passive crossover at 90W, while playing full spectrum pink noise. Would the woofer and tweeter each receive 45W? In other words, half of the signal?

Or would it be more like 60W/30W split? 

Obviously the only thing doing any splitting would be the passive crossover, which is just a filter.

There are some things of which I know a great deal, others not so much. This is one of the latter.


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## Huckleberry Sound (Jan 17, 2009)

No they won't get the same amount of power. If I am using the term correct there are resisters that puts the brakes on some of that power. Dont hold me to the term. The split could be all over the place, just depends on what you are using.

One of the main limitations to passive networks is the amount of power you can put them there. Some are at 100 watts or etc. So make sure you don't apply too much power through it, you could burn up the xover.


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## Alrojoca (Oct 5, 2012)

Great Set and choice by the way!

It's a very hard question to answer, maybe only JBL has the answer.

What I know is since tweeters need less power the midwoofers will get the most of the power.

In this case since I knew this looking at these components, the tweeters are 6 ohms nominal, the midwoofers are 2 ohms. Logic tells me the midbass will be getting most of the power, the tweeters being 94 plus db SPL I doubt Jbl would be sending 45 watts to them .


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## ajsmcs (Jan 26, 2015)

Thanks! I picked those after a combination of forum recommendations and research, and I'm really psyched to get them, get them installed, and break them in. 

Main reason I asked is because I've just swapped my whole setup (save for the headunit), and will be running active through a MiniDSP and 4ch amp.

I'm new to both active crossovers _and_ DSPs, so it will be a bit of adventure.

I guess my biggest question is: how do I set gains for a tweeter?

Woofer is easy. Use rated RMS power to calculate voltage, run 1000Hz sine, measure output voltage with DMM, adjust gain until it matches value calculated. Hook speakers back up. Adjust rest of the way with your ears.

I guess part of it is that I can't find any information on just the tweeter, like rated continuous power handling.

Where do you find information about it's impedance?


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## ajsmcs (Jan 26, 2015)

I had my old setup high passed at 80Hz, and that seems to be the sweet spot for my subwoofer's LPF.


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## Alrojoca (Oct 5, 2012)

60 watts is the power handling,
JBL P26t 1" Power Series Edge-Driven Dome Tweeters


And you will find out using a DSP you most likely will need to lower the output level for these on the DSP.

Wish you should have told us from the beginning you were not going to use the passives, and bi amp these.  

I hope this helps, active can be a different story with the power handling 

I would set it to 45-50 W just in case since there is no load cap coil protection just pre amplified power sent to them, you can also simply use the passives just for the tweeters, and cross them a bit higher with the DSP, you may find smoother sound through the passives, it's worth a try and decide what sounds better to your ears.


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## ajsmcs (Jan 26, 2015)

That's a good thought keeping the passives hooked up for the tweeters. :thumbsup:


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## cajunner (Apr 13, 2007)

it's a common misconception that hooking up one speaker on a two speaker crossover, such as comes with component sets, is safe and used interchangeably with using a capacitor to protect from 'DSP poppage' and occasional missteps with the crossover settings...

but the reality is that crossovers depend on both drivers being in circuit to create their various frequency response modifications, and taking out the mid/woofer will possibly create a low-impedance condition that could damage an amplifier and the crossover too...


I'm not saying every crossover has a circuit that won't work with just a tweeter or just a midrange not hooked up, I'm saying the possibility exists so as a practice and general guideline, do not connect a passive crossover to just one of the two speakers!


but do what you want, right...


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## Alrojoca (Oct 5, 2012)

Mmmm, maybe, maybe not. Since mine had a bi ampable passive, It would not be and issue.


From what I understand, the passive crossover taking simply 2 leads or one input, pos and neg going in the passive xover, they connect in parallel inside, the parallel connection will generate a lower impedance load, by eliminating one driver, the impedance may increase and actually be safer for the amplifier.

What I would do when I get the speakers, grab a DMM and measure the mid bass impedance, maybe even post it here, if its 1.8 ohms or higher I would see no issues not using the passive for the midwoofers. 


An amplifier driving some tweeters even if the tweeters present a 1 ohm load, in my opinion it is still safe since not too much power will be used to drive the tweeters assuming the gains are set with clean power and not clipped power. I have known of head units connected to 2 ohm tweeters with just a single 1st order cap and no issues known so far.



I remember measuring measuring resistance from the amp speaker leads through the passive and the midwoofer connected on the door and the difference was like 0.3-.4 ohms higher compared to measuring it right from the driver speaker terminals. Measuring tweeter impedance is another story or not quite possible. Maybe you can get a reading taken just from the passive crossover just to see what it is.

One thing we know these tweeters are 6 ohms nominal 

One thing I do agree about is , manufacturers build the drivers to work with the passives, they are not raw drivers and YMMV, bi amping active vs passive. Sometimes there is no sound benefit just a difference in SQ that many simply justify better by going active over passive. The benefit of active is just extra slopes, output levels better TA etc. Those are good reasons to have better flexibility to improved stage, balanced sound and EQ with 16 bands per channel. Of course active will sound better, the question is without any of those audio settings and comparing passive sound versus active even bi amping with the DSP, will I hear a huge difference? 
I went through this with my system, and I tend to prefer the smoothness and less fatiguing sound from the passives, I can keep tuning and trying, maybe I will match it eventually but with only 9 eq bands all the way across and not per individual channel, maybe I will not. I tend to be more sensitive to tweeter's sound but that is just my own issue even using very laid back non harsh tweeters.


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## gstokes (Apr 20, 2014)

ajsmcs said:


> It seems that, intuitively, a tweeter would require less power than a woofer to achieve the same SPL because a tweeter has a lot less moving mass than a woofer. More mass=more power to move. Its also moving a larger volume of air, which again takes more power.
> 
> The same goes between a woofer and a subwoofer. Subwoofer = much larger moving mass moving much more air = much more power. (although there's also the added fact that the sub-bass region actually needs more power in general just to be audible.
> 
> I guess the part I really don't understand is the correlation between audio frequency and electrical power. In other words, do the lower frequencies actually contain more energy than the higher frequencies?


It's got nothing to do with Mass..

There is more spectral energy at lower frequencies than there is at higher frequencies and the frequency is inversely proportional with the spectral energy in the signal, as the frequency decreases the spectral energy increases, as the frequency increases the spectral energy decreases..

Look at a sinewave on an oscilloscope, at low frequencies the sine wave is stretched out with lots of space between the peaks and wide valleys, lot's of spectral energy is able to fill the larger valleys between the peaks but as the frequency increases there is less space between the peaks and the valley becomes smaller and less spectral energy will fit, think of spectral energy as water filling those valleys, as the frequency increases water gets pushed out of the valley, as the frequency decreases the valley between the peaks becomes wider and more water is able to flow into the valley, that's the simplest explanation i can offer you, it's get real deep real quick but now you have a clue to the theory involved..


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## ndm (Jul 5, 2007)

Sooooo....in my simple mind I thought to myself....

Why dont you test the AC voltage on the input and output side of of the crossover. So just set the voltage on the amp output to lets say 17 volts. Verify it with a meter. Next test it at the output of the xover. This way you will know the ratio of the voltage dividing network in the xover

Of course it would only work if you have the passive available.


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## gijoe (Mar 25, 2008)

Just to add something, if you put 90 watts into a passive crossover, both the mid and tweet could potentially receive 90 watts. It's frequency dependent, basically, the 90 watts is full range, and when you split it to different speakers each speaker could receive 90 watts across their bandwidth. Now, tweeters don't generally require as much power to achieve the same perceived volume, so there are usually resistors to attenuate the signal, but the signal does not split into two 45 watt channels. 

Something else to consider is Equal Loudness curves. Do to our hearing, we need lower frequencies to be louder in order to perceive them as the same volume as a higher frequency. This is one reason why you need more power on woofers, yes they have more mass and need more power to move, but they also need to be playing a higher SPL in order to be heard as being the same volume as the high stuff. Here is a link to Fletcher Munson curves:
http://en.wikipedia.org/wiki/Fletcher–Munson_curves


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## gstokes (Apr 20, 2014)

Look at a sinewave on an oscilloscope, at low frequencies the sine wave is stretched out with lots of space between the peaks and wide valleys, as the frequency increases the valleys become narrower and there is less space between the peaks
Now think of water as the spectral energy trying to flow into those valleys, at low frequencies lot's of water is able to fill the wide valleys between the peak, lot's of spectral energy there.
As the frequency increases there is less space between the peaks and the valley becomes narrower, not as much will fit into the valleys, less spectral energy there.
As the frequency decreases again the valley becomes wider and more water is able to flow into it, increased Spectral Energy..
It gets real deep real quick but that's the simplest explanation i can offer you, now you have a clue to the theory involved..

Rewritten with permission from me


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## ajsmcs (Jan 26, 2015)

That's an interesting analogy that makes a bit of sense to me.

As far as each receiving the full 90 watts but at different frequencies:
I had thought about that. But the more I thought about it the less it made sense. 

I'm a numbers guy. As a rule, I don't accept any explanation- no matter how logical- unless I can reconcile it with numbers.

So I called up my PhD EE friend/coworker and asked him the following: _You output 90Wrms pink noise through the JBL P660C's above. How much of that power does that woofer and tweeter each see?_

His answer: "It's complicated, but the woofer will see the majority of that power."


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## Alrojoca (Oct 5, 2012)

:laugh::laugh::thumbsup:

I'm a numbers person too, the thing is sometimes,
Art, a phenomenon or an invention defeat science and we should just accept it.


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## sirbOOm (Jan 24, 2013)

Go to almost the bottom of the page and play with the output signal level change infographic. That pretty much gives you the right idea of how these work - they split power vs. frequency. Someone mentioned earlier that a passive crossover splits frequency, not necessarily power. What was being said as a whole was more or less accurate, at least how it's been explained to me at various times. Passive crossovers regulate frequency output to a specific speaker by in effect cutting power outside of the passband to that specific speaker. The 100 watts you send to a crossover gets split by frequency to each speaker, as designed. Within the assigned passband, a speaker (not taking into account unintentional net power consumption associated with a passive matrix) can get up to 100 watts of power. Tweeters are attenuated, it's just that the signal heading to the tweeter is getting attenuated by resistance (more than likely). So, in the end (again, not taking into account the power consumption of any passive network) the woofer in theory (but not in reality) can get 100 watts of frequencies from 0 to 3,000 at a 24 db curve and the tweeter might get just 50 watts due to attenuation on 3,000 to 20,000 Hz all from the same 100 watt signal from the amplifier (not a 130 watt signal).

Happy to be wrong. And either way don't care if I am because active is the way to be.


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## Jepalan (Jun 27, 2013)

I am not an expert in these manners, but I like to logic my way through things like this. So, this answer is just me "thinking out loud", so take it with a grain of salt, please.

The P660 has a crossover point of 3000 Hz between the woof & tweet. So off the bat, the passive crossover is going to send ~ 6 octaves of music energy to the woofer (46 Hz to 3KHz) and 3 octaves (3KHz to 24KHz) to the tweeter. 

So if the input signal has equal energy per octave (i.e. pink noise), we already know twice as much power will be directed to the woofer versus the tweeter by the passive crossover in all situations.

Now the next thing to think of is how power is distributed versus frequency in typical music content material.

Here is an excerpt from "Introduction to Live Sound Reinforcement: The Science, the Art, and the Practice"...

_"…the equal power split of music material is around 300Hz. Furthermore, energy content of typical music program material decreases at a rate of 3dB per octave above 1 KHz. This means that less power is required to amplify the high frequencies than the low frequencies. For example: suppose 100 W is required for content below 1 KHz. At 16 KHz, the requirements would be -12dB, or only about 7 W."
_


So, you can probably draw your own conclusions from those two perspectives above, but it sure seems to me like the tweets will require *significantly* less power.


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## ajsmcs (Jan 26, 2015)

Jepalan: That is literally the exact information I've been looking for, both regarding pink noise, and- especially- regarding actual music.

You have answered all of my questions.


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## gstokes (Apr 20, 2014)

sirbOOm said:


> Go to almost the bottom of the page and play with the output signal level change infographic. That pretty much gives you the right idea of how these work - they split power vs. frequency..
> Happy to be wrong. And either way don't care if I am because active is the way to be.


Looks like my analogy was pretty close and I totally agree with you about running full-active, it just doesn't get any better than that


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## Alrojoca (Oct 5, 2012)

Active should be cleaner since it is pre amplified filtering, Passive is post amplification but it also depends on the quality and design of the passive crossover. 

The word active crossover means more than just pre amplified filtering, it means more flexibility, slopes, band passing, and individual EQ per channel and more effective Time alignment available using Sound processors for a better sound experience.


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## gstokes (Apr 20, 2014)

When running passive all the amplifier can see is the load impedance of the crossover.. 

When running active the amplifier see's the load impedance of the loudspeaker itself..


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## Jepalan (Jun 27, 2013)

gstokes said:


> When running passive all the amplifier can see is the load impedance of the crossover..
> 
> When running active the amplifier see's the load impedance of the loudspeaker itself..


I'm not sure exactly what the significance of these statements are, but technically when running passive, the amplifier sees the *combined* impedance of the crossover network *and* the attached drivers.


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## Jepalan (Jun 27, 2013)

gijoe said:


> Just to add something, if you put 90 watts into a passive crossover, both the mid and tweet could potentially receive 90 watts. It's frequency dependent, basically, the 90 watts is full range, and when you split it to different speakers each speaker could receive 90 watts across their bandwidth. Now, tweeters don't generally require as much power to achieve the same perceived volume, so there are usually resistors to attenuate the signal, but the signal does not split into two 45 watt channels.


gijoe - do you have any references expanding on your explanation? I ask, because my research and intuition tell me that things are exactly the opposite of what you describe here. i.e. if you have a full bandwidth (20Hz to 20KHz) pink noise signal (equal energy per octave), then the crossover will split that energy between the woofer and tweeter. In the example I already posted (~3K crossover point), the tweeter would receive half as much power as the woofer. I am not confident in my knowledge here and am looking to learn, so would like to read more on your perspective.


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## Jepalan (Jun 27, 2013)

ajsmcs said:


> Jepalan: That is literally the exact information I've been looking for, both regarding pink noise, and- especially- regarding actual music.
> You have answered all of my questions.


ajsmcs - here is an even better reference that I stole (unapologetically) from another recent thread on active driver power reqs...

Passive Crossover Network Design


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## gstokes (Apr 20, 2014)

Jepalan said:


> I'm not sure exactly what the significance of these statements are, but technically when running passive, the amplifier sees the *combined* impedance of the crossover network *and* the attached drivers.


Thank-you for clarifying that, I have this bad habit of typing a sentence in my mind but there is a loose connection somewhere between my mind and my fingers, there could be several words missing from the sentence but when I read it back to myself all the words are there..


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## gijoe (Mar 25, 2008)

Jepalan said:


> gijoe - do you have any references expanding on your explanation? I ask, because my research and intuition tell me that things are exactly the opposite of what you describe here. i.e. if you have a full bandwidth (20Hz to 20KHz) pink noise signal (equal energy per octave), then the crossover will split that energy between the woofer and tweeter. In the example I already posted (~3K crossover point), the tweeter would receive half as much power as the woofer. I am not confident in my knowledge here and am looking to learn, so would like to read more on your perspective.


I'll see what I can dig up for you. This topic comes up pretty rarely, but I know several years ago I found something that was convincing. Granted, I know more now than I did then, so it would be good for me to revisit the concept. The only thing that consumes any real power is the resistors in the crossover, and the drivers themselves. The caps and inductors do not consume any power (except for the negligible amount their resistance consumes). Assuming there is no resistor to attenuate the tweeter, each driver would be able to use all of the power within the bandwidth that the crossover creates. If we use the 90 watt example, the crossover gets 90 watts 20Hz-20kHz, if you split that between two drivers, each driver still has 90 watts, just not full range. 

I'll come back later, hopefully with some real information to provide.


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## Jepalan (Jun 27, 2013)

gijoe said:


> I'll see what I can dig up for you. This topic comes up pretty rarely, but I know several years ago I found something that was convincing. Granted, I know more now than I did then, so it would be good for me to revisit the concept. The only thing that consumes any real power is the resistors in the crossover, and the drivers themselves. The caps and inductors do not consume any power (except for the negligible amount their resistance consumes). Assuming there is no resistor to attenuate the tweeter, each driver would be able to use all of the power within the bandwidth that the crossover creates. If we use the 90 watt example, the crossover gets 90 watts 20Hz-20kHz, if you split that between two drivers, each driver still has 90 watts, just not full range.
> 
> I'll come back later, hopefully with some real information to provide.


Thanks. Just thinking out loud again (and probably not using correct terminology) - I suspect that the difference lies in the strict definition of power within this context. I was using the concept of total spectral power in my discussion, where you are using amplifier power as measured at a single frequency. In that case, both concepts are correct. In your case, if we take max RMS voltage output as the constant then the amp can generate the same continuous average power putting out a 50 Hz test signal as putting out a 1 KHz or 16 KHz signal. Whereas if we are talking about pink noise, the power is spread across the entire spectrum and is a sum across frequencies.


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## gijoe (Mar 25, 2008)

Here is a link to a post about this topic, I'm still looking for an original source to explain this properly, but hopefully this helps explain things better than I've done so far.

Essentially, the crossover splits frequencies, not power. Ohms law dictates how much power each driver gets, so although in most situations the mid and tweet will not get the same power (even before attenuation of the tweeter) they potentially could if the impedance (AC resistance) is the same. 
Guide To Crossovers


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## gijoe (Mar 25, 2008)

An interesting quote I found on wikipedia that is a bit off topic, but interesting non-the-less.

"Crossover design expert Siegfried Linkwitz said of them that "the only excuse for passive crossovers is their low cost. Their behavior changes with the signal level dependent dynamics of the drivers. They block the power amplifier from taking maximum control over the voice coil motion. They are a waste of time, if accuracy of reproduction is the goal."

If one of the leading minds in crossover design says that passive crossovers are "a waste of time" there might be something to that.


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## gstokes (Apr 20, 2014)

gijoe said:


> Here is a link to a post about this topic, I'm still looking for an original source to explain this properly, but hopefully this helps explain things better than I've done so far.
> 
> Essentially, the crossover splits frequencies, not power. Ohms law dictates how much power each driver gets, so although in most situations the mid and tweet will not get the same power (even before attenuation of the tweeter) they potentially could if the impedance (AC resistance) is the same.
> Guide To Crossovers


Precisely, the wattage/power the crossover receives only dictates the wattage rating of the individual components in the crossover, the design of the crossover itself is entirely frequency based..


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## gijoe (Mar 25, 2008)

It gets complicated because each driver will have different impedance at different frequencies, it's always changing. If you had two drivers, set the crossover to split the signal, and those drivers somehow were still the same impedance, then each driver would get the full power (less losses) that went into the crossover. The power is not split by the crossover at all, so theoretically you could put 90 watts into the crossover and each driver could receive 90 watts simultaneously across their bandwidth (again, less losses). In the real world this won't happen because of the different impedances and dynamic nature of music (also the fact that most passive crossovers have resistors to attenuate the tweeter), but it is very possible that the power that each driver consumes sums to more power than the input. Don't get confused though, no new power is created, so summing the power at each driver wouldn't be accurate, but it is certainly possible that if you fed a crossover 90 watts, the mid could consume 70 watts and the tweeter could consume 30 watts.

I hope I didn't make this even more confusing. Someone with more knowledge could probably explain in a more simplified way.


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## Jepalan (Jun 27, 2013)

gijoe said:


> Guide To Crossovers


Interesting. I really think there is a fatal flaw in the author's explanation. He states "Let's pretend theoretically that we are running a 70 watt @ 4ohm amp full range. That amp (theoretically) puts out 70 watts at all frequencies at 4ohms, correct?"

The problem is that the amp doesn't put out 70 watts at all freqs, it puts out 70 W *total* that is spread out across all freqs (20 to 20KHz). IN other words, the sum of the power across all freqs is 70 watts. 

If an amp is putting 70 watts into a passive crossover from 20 to 20KHz, I guarantee each driver is receiving less than 70 watts. A passive device does not make power.


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## gijoe (Mar 25, 2008)

Jepalan said:


> Interesting. I really think there is a fatal flaw in the author's explanation. He states "Let's pretend theoretically that we are running a 70 watt @ 4ohm amp full range. That amp (theoretically) puts out 70 watts at all frequencies at 4ohms, correct?"
> 
> The problem is that the amp doesn't put out 70 watts at all freqs, it puts out 70 W *total* that is spread out across all freqs (20 to 20KHz). IN other words, the sum of the power across all freqs is 70 watts.
> 
> If an amp is putting 70 watts into a passive crossover from 20 to 20KHz, I guarantee each driver is receiving less than 70 watts. A passive device does not make power.


If the amp is putting out 70 watts from 20Hz-20kHz and the impedance is the same for both drivers in the network then yes, each driver will get 70 watts across it's specific bandwidth. No power has to be made, the frequency just gets split. If it's 70 watts full range you can split it up into any specific bandwidths and each will still be 70 watts.


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## gstokes (Apr 20, 2014)

Frequency and Spectral Energy are Inversely Proportional..

The higher the frequency a driver has to reproduce = the less energy that it requires to reproduce that frequency..

The lower the frequency a driver has to reproduce = the more energy it needs to reproduce that frequency..

It's like the light "ting" of a cymbal vs the heavy "BOOM" of the kick drum..

It doesn't take a lot of energy to reproduce that light "ting" from the cymbal but it requires a great deal of energy to reproduce that heavy "BOOM" from the kick drum..


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## gstokes (Apr 20, 2014)

gijoe said:


> If the amp is putting out 70 watts from 20Hz-20kHz and the impedance is the same for both drivers in the network then yes, each driver will get 70 watts across it's specific bandwidth. No power has to be made, the frequency just gets split. If it's 70 watts full range you can split it up into any specific bandwidths and each will still be 70 watts.


Precisely, all the crossover does is divide the frequency..


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## gijoe (Mar 25, 2008)

gstokes said:


> The amplifier doesn't push power into a driver, the driver draws energy from the amplifier based on what frequency it has to reproduce..


I was actually sitting here thinking I should add a comment just like this to help clarify and when I came back to the thread I saw that you took care of it. Good work.


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## gckless (Oct 11, 2012)

gstokes said:


> Precisely, all the crossover does is divide the frequency, it's up to each individual driver to determine how much energy it needs to reproduce that frequency..
> 
> The amplifier doesn't push power into a driver, the driver draws energy from the amplifier based on what frequency it has to reproduce..





gstokes said:


> Let's say we have a monoblock amplifier with 75 Wrms rating at whatever ohm..
> If we place a subwoofer on that channel and then play a track containing nothing but heavy bass, every time the bass hits the subwoofer will "draw" 75 Wrms from the amplifier..
> 
> Now let's take that same 75 Wrms channel and place a tweeter on it then play a track containing nothing but the light ting of a cymbal, it may only draw 10 Wrms from the amplifier even though there is the "potential" for it to draw 75 Wrms..


This would be an incorrect way of thinking. A driver does not draw anything, it is sent power based on a number of factors about the amp including power available and input voltage. 

Think of it this way: if a driver was the one drawing power (and therefore controlling how much power it receives) we would never blow any drivers ever.


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## Beckerson1 (Jul 3, 2012)

gckless said:


> This would be an incorrect way of thinking. A driver does not draw anything, it is sent power based on a number of factors about the amp including power available and input voltage.
> 
> Think of it this way: if a driver was the one drawing power (and therefore controlling how much power it receives) we would never blow any drivers ever.


Agreed 

A speaker is passive. It won't replicate sound unless acted upon. It needs a driving force. You can say the amp is this force but all the amp is there for is to boost the signal from your source unit. It increases power. 

Think of it as a water based system such as the old flour mills which used a water source to turn a wheel which in turn moved the grinding stones. Those stones won't move on there own unless acted upon. Newtons first law


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## ajsmcs (Jan 26, 2015)

Jepalan, I think what gijoe said has merit, but not in _all_ circumstances. 

As we said before, 90W of pink noise will result in the power split you mentioned before, since those 90W are spread over 20,000Hz worth of bandwidth.

But if you send those passive components 90W worth of pure 200Hz sine wave, only the woofer will see that power, and (theoretically assuming ideal components w/no losses) it will see all 90W worth.

Just the same, if you sent the those components 90W of 10,000Hz sine (can you say "painful?") it should also receive the full 90W.

I think a decent analogy is as follows:

You have a seesaw with an offset fulcrum and a 150lb box of bricks. If spread 50lbs worth across one arm, and 100lbs worth across the other, the seesaw is balanced, AND seeing a net 150lb load. This would be our pink noise.

But if you take the same 150lb box and put it just on the shorter end, the seesaw is no longer balanced, BUT the net load is still the same.

EDIT: I did not see there was a second page of comments until after posting this, so apologies if I'm repeating things.


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## ajsmcs (Jan 26, 2015)

Another thing: got my components in the mail yesterday, and was happy to find that the tweeter's power ratings were conveniently written on the back.  60W rms.

Now the question is- what do I do for tweeter protection? Just an inline cap? What's a good value to use?


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## gstokes (Apr 20, 2014)

ajsmcs said:


> Another thing: got my components in the mail yesterday, and was happy to find that the tweeter's power ratings were conveniently written on the back.  60W rms.
> 
> Now the question is- what do I do for tweeter protection? Just an inline cap? What's a good value to use?


depends on the frequency range of the tweeter, where do want to set the low pass cutoff..
Car Audio - Speaker Crossover Chart and Capacitance vs. Frequency Calculator(High-pass)


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## gstokes (Apr 20, 2014)

gckless said:


> This would be an incorrect way of thinking. A driver does not draw anything, it is sent power based on a number of factors about the amp including power available and input voltage.
> 
> Think of it this way: if a driver was the one drawing power (and therefore controlling how much power it receives) we would never blow any drivers ever.


excellent point and thank-you for the correction..


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## ajsmcs (Jan 26, 2015)

According to the interwebz, FR of the tweeter is 2500Hz - 23 kHz. 

Since my actual crossover will taken care of electronically, should I pick a value a fair amount lower than where I will be theoretically crossing it? Like, 1000Hz, for example?

My thought is that that way it won't have as much of an influence on the range of frequencies it would be outputting normally, but if some sort of glitch were to occur it would still prevent the the tweeter from seeing damagingly low frequencies.


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## gstokes (Apr 20, 2014)

ajsmcs said:


> According to the interwebz, FR of the tweeter is 2500Hz - 23 kHz.
> 
> Since my actual crossover will taken care of electronically, should I pick a value a fair amount lower than where I will be theoretically crossing it? Like, 1000Hz, for example?
> 
> My thought is that that way it won't have as much of an influence on the range of frequencies it would be outputting normally, but if some sort of glitch were to occur it would still prevent the the tweeter from seeing damagingly low frequencies.


If you're running them off a passive crossover why do you need as 1st order high pass filter, the crossover already has the tweeter wired to a high pass network BUT if the low pass cutoff point on the crossovers high pass filter is lower than 2.5kHz then you could run into trouble..
What passive crossover are you using ?

To answer your question a 15uF capacitor will block everything from 2.65kHz under so your tweeter would have an effective frequency response of 2.65kHz - 23kHz..


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## Alrojoca (Oct 5, 2012)

ajsmcs said:


> According to the interwebz, FR of the tweeter is 2500Hz - 23 kHz.
> 
> Since my actual crossover will taken care of electronically, should I pick a value a fair amount lower than where I will be theoretically crossing it? Like, 1000Hz, for example?
> 
> My thought is that that way it won't have as much of an influence on the range of frequencies it would be outputting normally, but if some sort of glitch were to occur it would still prevent the the tweeter from seeing damagingly low frequencies.


You mean higher? If you go below 2500 HZ you may blow it, stay above and work your way up, a 12 db slope works in most cases, just because the crossing point is 2500 , does not mean that it will not sound better at 2700hz or higher, some overlapping with the midbass may sound better in some cases also

On mine the xover point is 2000 HZ, they sounded better at above 2400hz to me.


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## ajsmcs (Jan 26, 2015)

So what frequency should I use to determine the protection cap, then? 2500?

Mind you I'm not talking about the active crossover setting, I'm talking about the *protection capacitor*.


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## Jepalan (Jun 27, 2013)

gijoe said:


> If the amp is putting out 70 watts from 20Hz-20kHz and the impedance is the same for both drivers in the network then yes, each driver will get 70 watts across it's specific bandwidth. No power has to be made, the frequency just gets split. If it's 70 watts full range you can split it up into any specific bandwidths and each will still be 70 watts.


I respectfully disagree. But I still think it is just a matter of semantics.

Example:

An amp is supplied 12 VDC @ 5.83 amps on it's power inputs (12 x 5.83 = 70W)
If the amp is 100% efficient it can put out 70 W *TOTAL* on it's output. There is only 70 W power available at it's input. The amp does not make power. No more than 70 W is available at its output.
With normal music (or pink noise), that 70 W will be spread across the audio spectrum. Some will go to the sub and some will go to the tweets and some will be lost due to passive crossover insertion losses. 
In every case, the sub will get less than 70W, the tweets will get less than 70 W and the sum of power between sub, tweets & losses = 70 W.

HOWEVER:

In the case where the amp is putting out a single 50 Hz tone, that tone might be ~70 W, but then all other drivers get 0 and the sum is still 70.
Also, the amp *could* put a single ~70 W 16KHz tone to the tweets while putting 0 into the other drivers.
In no case can this amp put 70 W to the sub while simultaneously putting 70 W to the tweets.

I think this last part is the point you are making^^


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## stevemk07 (Jan 3, 2012)

gstokes said:


> To answer your question a 15uF capacitor will *block everything from 2.65kHz under* so your tweeter would have an effective frequency response of 2.65kHz - 23kHz..


This is not correct.

Even if you could predict the crossover frequency of a 15uF capacitor inline with a tweeter having an nominal impedance of 4 ohms you would only be attenuating the signal just above that frequency and below it, not blocking everything below it. So the tweeter would still be receiving power for frequencies below the crossover point.

If you have a crossover network which is designed to work with your drivers then you do not need to worry about it. If you want to use an inline cap to protect the tweeter the general rule of thumb is to set the 1st order filter frequency (inline capacitor) at least 2.5 octaves above the resonant frequency (Fs) of the driver.... most of the time the Fs is somewhere around 1KHz... Assuming a 1KHz Fs, you would want your cutoff frequency to be at or above 6KHz (2.5 octaves above the Fs). The reason for this is a first order high-pass filter only attenuates the signal 6dB one octave below the cutoff frequency. In our example this would be at 500Hz. Theoretically, your tweeter would still be seeing power for signals in the lower ranges but at lower amplitude. With a first order filter the attenuation is not that much which is why they recommend setting at 2.5 octaves or more above the Fs.

In my vehicle I have the Morel MDT12 8 ohm tweeters. Spec sheet says they have an Fs of 1KHz. I am using a 1.5uF capacitor in conjunction with 5.5 ohms of resistance (in order to blend the tweeters with the mids) giving me a theoretical filter frequency of around 7800Hz. Works nicely giving me the smooth and clear sound I was after.


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## Alrojoca (Oct 5, 2012)

Using the passive, you can set the DSP x point lower, and it still can change the sound, since the slope increases using a DSP with a passive, better or worse is subjective, and depends on the passive and your own preference

For active, not passive and just getting a cap for protection, 1 octave below the X point, 1000hz below the x point value cap would do


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## Jepalan (Jun 27, 2013)

stevemk07 said:


> This is not correct.
> Even if you could predict the crossover frequency of a 15uF capacitor inline with a tweeter having an nominal impedance of 4 ohms you would only be attenuating the signal just above that frequency and below it, not blocking everything below it. So the tweeter would still be receiving power for frequencies below the crossover point.


Hmm. Not sure I agree. An in-line capacitor is a simple concept used all the time to block bass frequencies going to a tweeter. It is called a "bass blocker". Many run-of-the-mill factory systems use this in lieu of a full crossover network. So do coaxial speakers. 

The crossover point is very predictable via a simple equation (using nominal impedance the errors should be small).

Here is the equation and a list of cap values for difference tweeter impedances:

Car Audio - Speaker Crossover Chart and Capacitance vs. Frequency Calculator(High-pass)


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## stevemk07 (Jan 3, 2012)

Jepalan said:


> Hmm. Not sure I agree. An in-line capacitor is a simple concept used all the time to block bass frequencies going to a tweeter. It is called a "bass blocker". Many run-of-the-mill factory systems use this in lieu of a full crossover network. So do coaxial speakers.
> 
> The crossover point is very predictable via a simple equation (using nominal impedance the errors should be small).
> 
> ...


I am surprised you disagree as you had some of the best information in the thread thus far. As stated earlier the impedance rise and drops with frequency but also is quite unpredictable unless you are actually measuring it with test equipment at various frequencies. The guides are guides, nothing more. The calculators may get you close but the only way to be sure is to measure the characteristics of the actual driver in question. 

I know there are others around who understand and can explain all this much better than me. I just wanted to correct the potentially catastrophic information which was posted about a 1st order filter blocking "everything" below the filter frequency.

Most stand-alone crossover networks use 2nd order filters which attenuate frequencies at twice the rate of the 1st order filter. They also cause twice the shift in phase. Bass-blocker is just a layman's term for a 1st order high-pass filter. I suggest everyone just do some reading rather than continue posting misinformation on this thread.


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## Jepalan (Jun 27, 2013)

stevemk07 said:


> I am surprised you disagree as you had some of the best information in the thread thus far. As stated earlier the impedance rise and drops with frequency but also is quite unpredictable unless you are actually measuring it with test equipment at various frequencies. The guides are guides, nothing more. The calculators may get you close but the only way to be sure is to measure the characteristics of the actual driver in question.
> 
> I know there are others around who understand and can explain all this much better than me. I just wanted to correct the potentially catastrophic information which was posted about a 1st order filter blocking "everything" below the filter frequency.
> 
> Most stand-alone crossover networks use 2nd order filters which attenuate frequencies at twice the rate of the 1st order filter. They also cause twice the shift in phase. Bass-blocker is just a layman's term for a 1st order high-pass filter. I suggest everyone just do some reading rather than continue posting misinformation on this thread.


Yes, I agree. Sorry - didn't mean to put you on the defensive. I guess what I meant to say was that using a capacitor as extra protection for a tweeter when running active is a perfectly valid application and the accuracy of the calculations are good enough since you are placing the protection point well below the "real" crossover point you will be controlling precisely via the amp, DSP, or HU.


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## ajsmcs (Jan 26, 2015)

I believe the crossover in my component set is 4th order.

And yes, I understand that a xover just attenuates everything below the crossover point, it doesn't block it entirely. Higher order crossover = steeper attenuation slope.

So, here are my issues:

1.) I'm not even finished installing all of my new equipment. I don't want to install the tweeters until I have some sort of protection circuit in place.

2.) I am very new to the flexibility provided by the MiniDSP, and have barely scratched the surface in learning about adjusting crossover points. Like, I have no idea what sort of effect raising or lowering the crossover will have on the sound (other than the obvious...). My only experience resembling that is playing with the HPF/LPF for fronts/sub on my head unit. That I have a pretty good handle on. But for woofers/tweeters? I'm clueless.

Right now I have it set at the factory crossover point: 3000Hz. That's about as far as I've gotten into that particular realm of tuning.

*So if I don't know where I'll be crossing them over, how, then, do I determine a "protection cap frequency?"* (Yes, I know caps are measured in farads. I say it this way to distinguish from "crossover frequency")


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## gijoe (Mar 25, 2008)

Jepalan said:


> I respectfully disagree. But I still think it is just a matter of semantics.
> 
> Example:
> 
> ...


I really want to figure this out, my circuits knowledge isn't as advanced as others here, yet, and honestly I'm not sure how to evaluate circuits based on audio signals. I can analyze a circuit with a simple sine wave of a specific frequency, but that's a bit different. 

I admit that I may be wrong, since I haven't found any good information to support this yet, but I'm sure it's out there. 

Hopefully someone with more knowledge of crossover design can chime in.


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## Jepalan (Jun 27, 2013)

ajsmcs said:


> *So if I don't know where I'll be crossing them over, how, then, do I determine a "protection cap frequency?"* (Yes, I know caps are measured in farads. I say it this way to distinguish from "crossover frequency")


I had a similar question not too long ago. 
Does this help?
http://www.diymobileaudio.com/forum/general-car-audio-discussion/170890-rule-thumb-active-tweeter-protection.html


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## ajsmcs (Jan 26, 2015)

So now I'm really damn confused. 

Which frequency should I base my cap on? 

1000Hz or 6000Hz?


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## Jepalan (Jun 27, 2013)

gijoe said:


> I really want to figure this out, my circuits knowledge isn't as advanced as others here, yet, and honestly I'm not sure how to evaluate circuits based on audio signals. I can analyze a circuit with a simple sine wave of a specific frequency, but that's a bit different.
> 
> I admit that I may be wrong, since I haven't found any good information to support this yet, but I'm sure it's out there.
> 
> Hopefully someone with more knowledge of crossover design can chime in.


I think we are both right. Seriously. There is only a small wording issue I have with the article and what you posted. The difference in perspective is whether you are considering all of the amp power going into a single tone, or whether you are thinking about pink noise & normal music as sources. Your point is that an amplifier *could* put all it's energy into the tweeter or the woofer if the signal was a single tone at a given frequency, so you have to size drivers accordingly. My point is that when the input signal is broad spectrum (music or noise) the passive crossover *does* split the amp power between highs and lows.


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## ajsmcs (Jan 26, 2015)

Yes, yes it does!

Tweeter has 6ohm impedance, so a 20uF cap would result in a cutoff frequency of 1325, which seems pretty reasonable to me.

Damn... $5 per seems a bit steep for just a cap, though.


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## Jepalan (Jun 27, 2013)

ajsmcs said:


> So now I'm really damn confused.
> Which frequency should I base my cap on?
> 1000Hz or 6000Hz?


Assuming you are going to use an active setup (tweeter on its own amp channel), then your HPF will be set either by your amp, DSP, or HU.

The cap is just for catastrophic protection (i.e. accidentally disabling filters on your HU and blasting full spectrum power at the tweet = pop)

SO - you want the crossover for the cap to be *lower* than the lowest final freq you intend to set your amp/DSP/HU HPF at. 

1 KHz sounds good to me.


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## ajsmcs (Jan 26, 2015)

Wait nevermind that guy just recommended way oversized versions. I can be fairly certain my tweeters will never see 250V.


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## Jepalan (Jun 27, 2013)

ajsmcs said:


> Yes, yes it does!
> 
> Tweeter has 6ohm impedance, so a 20uF cap would result in a cutoff frequency of 1325, which seems pretty reasonable to me.
> 
> Damn... $5 per seems a bit steep for just a cap, though.


Yes, 20uF sounds reasonable in your situation. I doubt you will be crossing anywhere near 1325 with your final HPF setting. If you are using the tweet from the P660C I think you wan to run it higher than 2000 to avoid distortion. Probably 2500-ish


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## ajsmcs (Jan 26, 2015)

Yeah, thats exactly what made most sense to me from the get go. :thumbsup:


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## Jepalan (Jun 27, 2013)

Yep. And 250V does seem overkill. Conservative calculation: assume you hit the tweet with a 60 W RMS sine wave, then V RMS = sqrt(60x6) = 18.9 V RMS = 26.7 Vpeak

Seems 50V would be plenty.

Here is a rule of thumb: Typically, 50-volt capacitors can handle up to 70 RMS Watts, 100v can handle 200w and 250v up to 300w.

From this site: Building Custom Crossovers


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## ajsmcs (Jan 26, 2015)

Thanks for the link. What's a good source for those?


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## Jepalan (Jun 27, 2013)

Google 
I get most of my components free from work, or as free-samples via our purchasing dept.


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## thehatedguy (May 4, 2007)

I would not expect the real world results if using a real driver that has real impedance to match those text book idea passive results.

Those results from those calculators do not take into account the natural roll off of the speaker nor the impedance changes- they are based on flat line FR and a flat resistance, neither of which is what you have in real life (though some speakers are purely resistive, 99% are not).


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## stevemk07 (Jan 3, 2012)

In my limited experience ERSE caps are a great value. The metallized polypropylene or polyester should work fine. I am using the polyester and the sound seems to be very clear and uncompromised.

So yes for this application as a last resort protection for your tweets the higher value caps mentioned above should suffice. My recommendation would a slightly lower value though which should not have any real negative impact on your final sound but provide better protection. Sorry if I confused anyone.


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## Jepalan (Jun 27, 2013)

thehatedguy said:


> I would not expect the real world results if using a real driver that has real impedance to match those text book idea passive results.
> 
> Those results from those calculators do not take into account the natural roll off of the speaker nor the impedance changes- they are based on flat line FR and a flat resistance, neither of which is what you have in real life (though some speakers are purely resistive, 99% are not).


I understand, appreciate and agree with your statement, but I don't understand how to *apply* this information to the topic at hand - is there an alternate method for selecting capacitor values for tweeter protection in an active setup that you can suggest? Or are you saying the OP should not try and use a capacitor for tweeter protection?


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## Alrojoca (Oct 5, 2012)

Solen and Dayton are some other good polypropylene caps, and I would not settle for less than polypropylene, they are not cheap, over $10 each and good luck trying to find some being less than 250 V. Expect a C battery size or bigger than that, on those values and voltage. 


Good topic, I posted a similar thread and one guy with 2 ohm tweeters was using a 70 uf cap, that's bigger than a soda can


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## ajsmcs (Jan 26, 2015)

...I need to talk to some of my EE friends around Center...

I think supply raiding is in order...

Failing that, I guess I'll just have to suck it up and buy them online...


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## gstokes (Apr 20, 2014)

stevemk07 said:


> In my limited experience ERSE caps are a great value. The metallized polypropylene or polyester should work fine. I am using the polyester and the sound seems to be very clear and uncompromised.


x 2, high quality components..
Audio Grade Capacitors | ERSE

Always use metallized polypropylene film (MPPF) capacitors..


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## ajsmcs (Jan 26, 2015)

..would mica or tantalum capacitors work? XD


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## ajsmcs (Jan 26, 2015)

The stuff we have is all ultra-high-grade, with very tight tolerances. I've got a buddy that works with airborne RF equipment who's looking into his stores for me. :thumbsup:


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## gstokes (Apr 20, 2014)

ajsmcs said:


> ..would mica or tantalum capacitors work? XD


Sure but the audio will suffer audible signal degradation..


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## ajsmcs (Jan 26, 2015)

Whelp. They're ordered. It's weird that no-one carries these sorts of caps in sizes that aren't gigantic.


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## Patrick Bateman (Sep 11, 2006)

Alrojoca said:


> Active should be cleaner since it is pre amplified filtering, Passive is post amplification but it also depends on the quality and design of the passive crossover.
> 
> The word active crossover means more than just pre amplified filtering, it means more flexibility, slopes, band passing, and individual EQ per channel and more effective Time alignment available using Sound processors for a better sound experience.


 groan


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## Patrick Bateman (Sep 11, 2006)

ajsmcs said:


> I've done a lot of searching trying to find this answer, both on this forum and elsewhere, and I haven't found anything I've been satisfied with. I'm sure there's probably a million threads I missed, but at this point its easier to just ask.
> 
> It seems that, intuitively, a tweeter would require less power than a woofer to achieve the same SPL because a tweeter has a lot less moving mass than a woofer. More mass=more power to move. Its also moving a larger volume of air, which again takes more power.
> 
> ...


I've generally found that tweeters need about 1/10th or even 1/100th of the power that the woofer gets.

For instance, if I have 100 watts going to my woofers, I'm looking at 1-10 watts for my tweeters.

Mass has something to do with it, but it's mostly enclosure size.

In the 1980s and 90s we were using a lot of gear that was "truly" designed for home audio and pro audio. In that era, *subwoofer boxes were very large.* The efficiencies of woofers were in the high 80s and tweeters were in the low 90s. *In that scenario, you might give your woofer forty watts and your tweeter ten watts.*

Then we discovered isobaric mounting, and Kicker created solobaric (which was basically a woofer that had parameters similar to an isobaric pair.)

Fast forward twenty years, and the efficiency of tweeters is basically unchanged, *but the efficiency of woofers is dramatically lower.* It's not unusual to see systems where the woofer has an efficiency of 81dB and the tweeter has an efficiency of 91dB.

By the way, manufactures "cheat" these ratings constantly. For instance, the spec sheet of a woofer with dual 2ohm coils will say that the woofer has an efficiency of 90dB.

*But that's cheating.*

If they'd spec'd the same woofer using the same voltage as the tweeter, it's efficiency would actually be 81dB, not 90dB.



TLDR - yeah, you need way less power for a tweeter. 1-10 watts will get the job done.


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## I800C0LLECT (Jan 26, 2009)

Really glad I found this thread. Not that I cared to really research...but this has been my practice/assumption for quite a while.

A lot of people over-think whether XXXXXX can/can't supply enough power for a tweeter. The common argument has been whether to run tweets off HU power for the sake of K.I.S.S. 

Thanks for chiming in too Patrick. I always feel better about my assumptions when you post since you always bring great facts and rationale to the table. But before that even, sirbOOm & Jepalan, great links and feedback to the Op. Really glad we still have so much great input from members around here


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## SWRocket (Jul 23, 2010)

Great thread, I learned alot.
I wish someone made an amp that instead of delivering 50W per channel into 4 channels, delivered 80W into each of two channels and another 20W into each of the other two channels.


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## I800C0LLECT (Jan 26, 2009)

Here you go... I think there's another recent amp floating around too. I think it's a Kenwood

JL Audio 500/5 (jl5005) 500 watts, 5-Channel Amplifier


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## SWRocket (Jul 23, 2010)

Nice, I don't know how I missed it.
but it's discontinued 
So close, but yet so far. I may look for one on ebay


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