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MultiWay Conventional loudspeakers with crossovers 

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15th October 2012, 11:15 PM  #1 
diyAudio Member

What's The Deal With Phase Angle?
Well Fellas (and Ladies)?
What IS the deal with phase angle & why is it so important? 
15th October 2012, 11:20 PM  #2 
diyAudio Member
Join Date: Nov 2003
Location: Brighton UK

Hi,
The real acoustic phase angles or the very different impedance phase angles ? rgds, sreten.
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There is nothing so practical as a really good theory  Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail  Abraham Maslow 
15th October 2012, 11:29 PM  #3 
diyAudio Member

I don't know the difference soooooo both.
In relation to the "Difficulty" of an amplifier to drive. 
15th October 2012, 11:50 PM  #4 
diyAudio Member
Join Date: Apr 2010

Oh, that's what the speaker looks like to the amplifier  that's definitely the electrical or impedance phase angle. Speakers almost never look purely resistive to an amplifier  the impedance, boththe "8 ohms" approximation of the absolute value and the phase angle between the voltage and the current, change with frequency, and can be either inductive or capacitive in different frequency ranges (though I think most of the range is inductive). Resistive is the easiest for the amplifier to drive. The more reactive (inductive or capacitive) the speaker is, the more current the amplifier must provide to get the same output as a frequency where the speaker's impedances is more (nearly) resistive .
Expect Smithcharttype graphs to be posted... 
15th October 2012, 11:54 PM  #5 
diyAudio Member

SO......The steeper the phase the harder it is for the amp to drive?

15th October 2012, 11:59 PM  #6 
diyAudio Member

So, how do amplifiers handle phase reversals in 3rd order crossovers?
Are they "Hard" to handle? 
16th October 2012, 12:20 AM  #7 
diyAudio Member
Join Date: Nov 2003
Location: Brighton UK

Hi,
Difficulty to drive is related to the impedance phase angle, and nothing to do with high order x/o acoustic phase changes. Simply put you want to avoid large phase angles at the same time as low impedance, large phase angles at high impedance don't matter. For a purely resistive 8 ohm load power is dissipated in the load. For a purely reactive 8 ohm load at the same current no power is dissipated in the load and this power is dissipated by the amplifer. The more reactive a given load impedance, the more it thermally stresses the amplifier compare to a purely resistive load. As the thermal stress on amplifier into resistive loads depends on current there are some simple rules of thumb : An amplifier for 8 ohm speakers must be able to drive 4R. An amplifier for 6 ohm speakers must be able to drive 3R. An amplifier for 4 ohm speakers must be able to drive 2R. In all cases for the latter not necessarily continuously. This covers the phase / reactance issues of nearly all speakers. With proper amplifier design and sensible speaker design its no big deal most of the time. However with chipamps and their aggressive protection and in particular current limiting, and their specification chasing, supply design is a big issue. rgds, sreten.
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There is nothing so practical as a really good theory  Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail  Abraham Maslow Last edited by sreten; 16th October 2012 at 12:24 AM. 
16th October 2012, 12:32 AM  #8 
diyAudio Member
Join Date: Apr 2010

No, those diagram show the phases generated by the crossover, or more accurately, the difference between the phase of the input voltage (of the crossover) and the phases of the output voltages at the driver terminals. These determine whether each driver should be connected with "+" polarity or "" polarity to get the proper acoustic phase from the speaker. These have little to do with the phase between the input's voltage and current. That phase also varies with frequency, whether it's a single fullrange driver or a multiway system with a crossover. One design isn't necessarily harder than another for an amplifier to drive, but specific models of speakers are harder than others.
The whole thing is basically AC circuits analysis (one of the fundamental courses in Electrical Engineering), which needs (the mathematical concept of) complex numbers as a prerequisite. 
16th October 2012, 12:46 AM  #9 
diyAudio Member

OK, that being said, how can you predict the Impedance and Acoustic "Phase" of a given loudspeaker in simulation?
I take it Crossover Pro 3 cannot show these aspects of design? 
16th October 2012, 08:56 AM  #10  
diyAudio Member

Quote:
Basically, the phase plot is the derivative (calculus) of the FR plot. You can extract phase with a HibertBode transform applet, but that doesn't mean you can use it in a certain program to your advantage. Some simple calculators or simulators assume perfect resistive loads and flatFR drivers; and offsets, phase, and such are not factored into the box of tools to produce good results. Later, Wolf
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