# choosing tweeters and mid range drivers



## malefacter (Jul 17, 2011)

how do you guys go about deciding on your tweeter and mid range power handling in other words lets say we have a woofer that's 300 wats RMS do you figure that the tweeter wold need 10% or 30 wats ?


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## GranteedEV (Aug 8, 2010)

One way of knowing this is to take *your* favorite music, and watch its visualized response on a program like foobar2000.Is the bass a good 10db louder than the midrange? Is the midrange 20db louder than the HF? What will be the passband of each driver? What is the size of the room? How far do you sit? 

There's plenty factors at play in driver selection. Frequency response, impedance/sensitivity (for passive speakers at least), off axis response, suitability for a given waveguide, cone breakup, excursion, IMD, and yes, thermal compression.

I'm gonna be honest with you. If you're picking drivers based on "watts", I suspect you're probably not ready for designing a crossover...


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## malefacter (Jul 17, 2011)

instead of insulting me by telling me i don't know what im doing why don't you explain how you go about it? i dident ask about crossovers and im not just going by power handling but you woldent want to pare up a 5 wat tweeter with a 1000 wat woofer with similar spl


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## GranteedEV (Aug 8, 2010)

Sorry, I didn't mean to offend you. I just got the impression that you were approaching this the wrong way and I hoped to help guide you towards taking it nice and slow and help improve your understanding wherever I can.

As I said, power handling is a function of frequency. If your tweeter is crossed at 6khz, for example, and your woofer is crossed at 300hz, then you might be fine using a 1000w woofer and a 5w tweeter, as most high frequencies are extremely low in level, being mostly overtones/harmonics of lower fundamental frequencies.

As for my "process", I guess first I would decide on a general "driver size". That is, what kind of dispersion pattern do I want my speak to follow, and how evenly? An 8 inch driver might give me excellent power handling, but its dispersion mate it well to a 1" tweeter? The tweeter might thermally handle plenty of power, but does it have the surface area/excursion to cross over low enough to match the dispersion of the woofer? Do You want to use a waveguide on the tweeter by any chance?

Next I would consider cone resonances in my passband. I don't want a midrange that's breaking up in a frequency range where I expect it to contribute; likewise with tweeters and woofers of course.

This is about where power handling would come into play again. Do the passbands I chose for the drivers based on their breakup stress the drivers at the levels I listen to, with the content I generally listen to, in the room I will be in? Obviously electronic music won't have the same power handling as jazz, which won't have the same power handling as a movie. I think you really need proven measured drivers that can deal with compression and excursion grracefully - manufacturer power spec just doesn't cut it.

In considering drivers, you need to consider your crossover. Will it be active or passive? Are you willing to spend half your budget on a complex passive crossover or would you rather spend that money on drivers that behave better?


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## maxserg (Dec 11, 2008)

And to add...

Efficiency of the woofer compared to the other components.

You should match as close as possible the efficiency of any driver you choose. It easies up the choice of the components. Even if you go to the active route, I wouldn't personnally like to match a 97db/W/meter woofer to a 85db/W/meter mid and a 88db/W/meter tweeter. Those component do not have to go into power compression. It could work ok for balancing the sound at low to medium level but the lowest efficient component could easisy go into power compression so dynamics would shift in some frequencies compared to the others.

Sorry for my englishlddude:


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## GranteedEV (Aug 8, 2010)

maxserg said:


> Efficiency of the woofer compared to the other components.


I'm not the biggest believer in this, although it does make passive speaker design MUCH easier. if I recall correctly, Dennis Murphy used around 14db of attenuation on the RAAL tweeter on the soundscape to match the sensitivity of the woofer. As a general rule though, As you go up in frequency, your sensitivity should go up. You don't want to passively attenuate at bass frequencies as much as at tweeter frequencies. And I generally remove 3db or so from a speaker's sensitivity rating to account for baffle step compensation.



> Even if you go to the active route, I wouldn't personnally like to match a 97db/W/meter woofer to a 85db/W/meter mid and a 88db/W/meter tweeter. Those component do not have to go into power compression. It could work ok for balancing the sound at low to medium level but the lowest efficient component could easisy go into power compression so dynamics would shift in some frequencies compared to the others.


What is power compression, though - thermal limitations - I wonder how valid they in real world, home usage. Are we talking about electric guitars for 3 hours, or a hard drum hit every few seconds?


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## robbo266317 (Sep 22, 2008)

I wouldn't worry overly about matching driver sensitivity as generally the woofer has the lowest sensitivity followed by the mid and tweeters usually have the highest. A simple resistive circuit can be used to match the levels in passive designs and if you go active it's even easier.

A bigger consideration is the overlap range of the drivers to ensure they interact well together. (As well as the other factors mentioned in the preceding posts)

The things that you need to consider are:-

What is your total budget.
Do you want to go passive or active in the crossover. (If you go active do you have the amps available)
Have you any specific drivers in mind? 
Do you want two way or three way?

Cheers,
Bill.


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