I know the specifics of this are a lot more complex to calculate properly than I'm describing here, not trying to model a speaker design off the answer - just trying to take my limited understanding one small step forward.
If I have a 3 way passive crossover that's designed to drive 8 ohm speakers and I have an 8 ohm speaker wired to each of the crossover outlets (Low, Mid, High) - under 'normal' use - what load is the amp going to see?
I took a guess at approximately 8 ohms but my best explanation for that answer was pretty garbled!
Thanks 🙂
If I have a 3 way passive crossover that's designed to drive 8 ohm speakers and I have an 8 ohm speaker wired to each of the crossover outlets (Low, Mid, High) - under 'normal' use - what load is the amp going to see?
I took a guess at approximately 8 ohms but my best explanation for that answer was pretty garbled!
Thanks 🙂
I'm aware that impedance can change relative to frequency - let's assume that 'under normal use' means playing music with some bass, mid and treble content.
I'll happily take a nominal value as an answer to the question based on that to get me started.
Thanks.
A well designed crossover for Nominal 8 ohm drivers will have a minimum of 5 or 6 ohms at some frequencies. So it will also be Nominal 8 ohm speaker.
Since most amplifiers put out a set voltage and supply enough current to support the voltage into the load, you typically don't care in a fairly wide range.
As an example, I ran 2 8 ohm nominal drivers in parallel with a class D amp with a 6 ohm minimum spec. The amp didn't care as long as I didn't hit its current limit.
HTH
Since most amplifiers put out a set voltage and supply enough current to support the voltage into the load, you typically don't care in a fairly wide range.
As an example, I ran 2 8 ohm nominal drivers in parallel with a class D amp with a 6 ohm minimum spec. The amp didn't care as long as I didn't hit its current limit.
HTH
Maybe a clearer way of asking that question would have been:
Is the nominal/theoretical/ideal impedance calculated as (8/3)+(8/3)+(8/3) where 3 is the number of crossover bands rather than (8+8+8) or (8/3) or something else.
Always challenging asking a technical question on a subject you don't fully grasp!
Is the nominal/theoretical/ideal impedance calculated as (8/3)+(8/3)+(8/3) where 3 is the number of crossover bands rather than (8+8+8) or (8/3) or something else.
Always challenging asking a technical question on a subject you don't fully grasp!
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None of the above.
The function of an ideal passive crossover is to expose the driver impedance in the passband and infinite everywhere else.
An example:
Woofer has a nominal 16 ohm impedance. Crossover to mid 400 Hz.
Midrange is 6 ohm nominal. Crossover 400 to 2 k Hz.
Tweeter is 8 ohm nominal, 2k Hz up.
The speaker would be considered a 6 ohm nominal speaker.
In the various bands, the amplifier load would be the load of the driver in the passband.
From a math standpoint, Lowest common factor may be the closest I can come to stating it.
HTH
The function of an ideal passive crossover is to expose the driver impedance in the passband and infinite everywhere else.
An example:
Woofer has a nominal 16 ohm impedance. Crossover to mid 400 Hz.
Midrange is 6 ohm nominal. Crossover 400 to 2 k Hz.
Tweeter is 8 ohm nominal, 2k Hz up.
The speaker would be considered a 6 ohm nominal speaker.
In the various bands, the amplifier load would be the load of the driver in the passband.
From a math standpoint, Lowest common factor may be the closest I can come to stating it.
HTH
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Yes, exactly as DougL says.
To put it simply in your scenario, the load at bass frequencies is nominally 8 ohm, the load at mid frequencies is nominally 8 ohm and the load at high frequencies is nominally 8 ohm.
So, the entire audio spectrum sees a nominally 8 ohm load i.e. the system impedance is nominally 8 ohm.
To put it simply in your scenario, the load at bass frequencies is nominally 8 ohm, the load at mid frequencies is nominally 8 ohm and the load at high frequencies is nominally 8 ohm.
So, the entire audio spectrum sees a nominally 8 ohm load i.e. the system impedance is nominally 8 ohm.
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Ah - OK. So, in my example, the nominal speaker impedance would be 8 ohm but that's because no matter what frequency the speaker was outputting - it would be via an 8 ohm driver.
Apologies for having to go round this a few times but can you explain how you got a nominal value of 6 ohm from this 16/6/8 ohm combination?
Thanks - much appreciated.
Apologies for having to go round this a few times but can you explain how you got a nominal value of 6 ohm from this 16/6/8 ohm combination?
Thanks - much appreciated.
Of the 3 drivers in the example, the 6 ohm was the lowest nominal impedance.
Therefore, the speaker nominal was 6 ohms.
Nominal impedance is a way for a non-tech person to get some simplistic idea which tap to use on his tube amp in 1950.
Today its main purpose is to determine id you are going to **** off your class D amp with a 2 ohm nominal car subwoofer.
HTH
Therefore, the speaker nominal was 6 ohms.
Nominal impedance is a way for a non-tech person to get some simplistic idea which tap to use on his tube amp in 1950.
Today its main purpose is to determine id you are going to **** off your class D amp with a 2 ohm nominal car subwoofer.
HTH
Outside the design range of each crossover section, the input impedance of that section
increases considerably, and has little effect on the total, since all the crossover sections
are typically in parallel.
So in the midrange, you mainly see the midrange crossover section's input impedance.
In the highs you mainly see the tweeter section's input impedance. In the lows you see
the woofer section's input impedance. These input impedances may or may not be equal
to the actual driver impedances.
All these sections in parallel make up the speaker system's impedance vs frequency curve.
There may be peaks or valleys in the impedance curve near the transistion points.
Often the nominal rated system impedance is listed as whatever it is around say 400Hz and
ignore the various dips or peaks.
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