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Old 9th October 2014, 12:57 AM   #1
Sape is offline Sape  Finland
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Default How do you calculate loudspeaker total impedance

Hi

I was wondering how to calculate the total impedance of 3-way loudspeaker?
So, that is the impedance what the amplifier sees.
The drivers are connected in parallel ?
So if you have 3 parallel 8ohm drivers so they would combine total of 2.67 ohms?
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Old 9th October 2014, 01:09 AM   #2
gedlee is offline gedlee  United States
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Put simply yes. But the real impedance is anything but flat, so your simple example is just that, very simplified.
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Old 9th October 2014, 01:28 AM   #3
rayma is offline rayma  United States
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Quote:
Originally Posted by Sape View Post
Hi

I was wondering how to calculate the total impedance of 3-way loudspeaker?
So, that is the impedance what the amplifier sees.
The drivers are connected in parallel ?
So if you have 3 parallel 8ohm drivers so they would combine total of 2.67 ohms?
Don't forget that there are crossover components as well. Check out some Stereophile on-line speaker reviews,
they plot speaker system impedance and phase. Usually, each driver in the speaker system has some crossover
components between it and the amplifier, and the inputs to these driver circuits are all connected in parallel
for the amplifier to drive. Sometimes other ways are used to connect the components, though.

Last edited by rayma; 9th October 2014 at 01:32 AM.
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Old 9th October 2014, 01:51 AM   #4
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In the Beginning, God created Spice, and all was good.

Loudspeakers and crossovers were modeled in Spice before SPL traced based crossover design tools became freely available.

There are a few tutorials on how to use the speaker T/S parameters to create a decent Spice model. You can use LTSPICE with a simple amplifier model to get impedance vs. frequency, phase, even SPL vs. freq with your crossover. Good for early paper design work.... before you take out a mic and measure all of your speakers in the cabinet for detailed SPL data for final simulation.

=====================
Computer-Aided Electroacoustic Design with Spice W. Marshall Leach
users.ece.gatech.edu/mleach/papers/spice_electro.pdf

http://micka.de/org/en/download/spice-tsp_en.pdf
www.micka.de/org/download/spicetsp.asc.zip

Another article on modelling of loudspeaker impedance: ePanorama.net | Audio | Video | Circuits | Electronics Design
Measuring Loudspeaker Driver Parameters

Loudspeakers
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Old 9th October 2014, 02:13 AM   #5
Sonce is offline Sonce  Macedonia
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Quote:
Originally Posted by Sape View Post
Hi
I was wondering how to calculate the total impedance of 3-way loudspeaker?
So, that is the impedance what the amplifier sees.
The drivers are connected in parallel ?
So if you have 3 parallel 8ohm drivers so they would combine total of 2.67 ohms?
3-way loudspeakers means 3 different drivers with high-pass or low-pass (or both - for midrange) filter on each driver, and all combined in parallel (forget for this moment the serial crossover). Total impedance is a bit misleading, because the lowest impedance is what realy is counting (is more important). So, if the mid is 4-ohm and woofer and tweeter are 8-ohm, than the whole loudspeaker should be 4-ohm nominal impedance.
For sure if you put 8-ohm 3 drivers (without filters) in parallel, than you have 2.67-ohm loudspeaker.
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Old 9th October 2014, 02:30 AM   #6
gedlee is offline gedlee  United States
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Quote:
Originally Posted by LineSource View Post
In the Beginning, God created Spice, and all was good.
Thank goodness we have moved on quite a bit from there. Spice never could do a good job of modeling a loudspeaker.
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Old 9th October 2014, 02:44 AM   #7
sreten is online now sreten  United Kingdom
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Quote:
Originally Posted by gedlee View Post
Put simply yes. But the real impedance is anything but flat,
so your simple example is just that, very simplified.
Hi,

Put simply no, not in the slightest. 3 8 ohm drivers
in a 3 way speaker = an 8 ohm speaker, not 2.67.

Doesn't matter whether the x/o is series or parallel.

rgds, sreten.

In reality unless you screw up the x/o the speakers
impedance is determined by the low bass section.
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When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 9th October 2014 at 02:51 AM.
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Old 9th October 2014, 02:48 AM   #8
rayma is offline rayma  United States
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Quote:
Originally Posted by sreten View Post

Put simply no, not in the slightest. 3 8 ohm drivers
in a 3 way speaker = an 8 ohm speaker, not 2.67.
Yes, in practice with a proper crossover this is true, but he didn't understand that there's a crossover network necessary,
so in his terms, he was right.

Last edited by rayma; 9th October 2014 at 02:59 AM.
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Old 9th October 2014, 02:57 AM   #9
sreten is online now sreten  United Kingdom
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Hi,

The OP asked if the drivers are in parallel, no they are not.
So the next question, that means its 2.67 ohms is wrong.

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
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Old 9th October 2014, 03:12 AM   #10
gedlee is offline gedlee  United States
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sreten - Really? you are going to lecture me on how to calculate parallel impedances? You can be a real pip sometimes!
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