What would happen to the overall response of 4 ohm speaker through a crossover designed for an 8 ohm load?
I think I know the answer but I would appreciate it if someone could independently confirm this.
Also, I have no experience with crossovers but is it correct that, when using a crossover, a 4 ohm source impedance uses 4 ohm speakers?
This is because, unlike when you connect two 8 ohm speakers in parallel to present a 4 ohm load, the crossover impedance changes with frequency such that the load at any frequency will average 4 ohms. Correct?
I think I know the answer but I would appreciate it if someone could independently confirm this.
Also, I have no experience with crossovers but is it correct that, when using a crossover, a 4 ohm source impedance uses 4 ohm speakers?
This is because, unlike when you connect two 8 ohm speakers in parallel to present a 4 ohm load, the crossover impedance changes with frequency such that the load at any frequency will average 4 ohms. Correct?
One thing to keep in mind is that driver impedance is not constant over the frequency range of a driver. It's why some speakers kill amps at certain frequencies. You might want to check that graph for the two speakers.
The bigger issue is that unless it's the same speaker (just with a different base impedance), a crossover designed for one driver will probably not work very well with another. Especially if it was carefully tuned for that other driver's characteristics.
Why don't you elaborate then?
Because I'm testing you guys to see if you know anything about crossovers.
If it's a simple 1st order the woofer frequency will double and the tweeter will be halved so you'll have an overlap.
Tweeter will be doubled too. As the capacitor works into a lower impedance, the cutoff frequency goes up.
The crossover frequency is based on the ratio of the capacitive or inductive reactance relative to the speaker impedance at the crossover. If the speaker impedance changes, then the Ration changes and correspondingly the crossover point changes.
We can work this out simply by using at basic on-line crossover calculator -
Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)
Using a simple First Order filter, we calculate the values for a crossover at 1000hz with 8 ohm drivers -
C1 = 19.875 uF
L1 = 1.234 mH
Now we change the driver impedance to 4 ohms and determine what frequency gives us the same component values.
FC1 = 2000hz (19.875uF)
FL1 = 500hz (1.234 mH)
So, the High Frequency shift UP by an octave, and the Low Frequency shifts DOWN by an octave, leaving a 1500hz gap in the middle.
Given the question you are asking, one can only assume you have either an Off-The-Shelf crossover or you have something you've scavenged from another speakers. This is a waste of time.
The components necessary for a basic crossover are not that expensive, and there are many crossover calculators on-line. As well as available software to design and model crossovers.
Further, if you design your own, you can determine the impedance of your specific drivers at the crossover frequency, and use that value in your crossover calculations for more accurate results.
Dayton off-the-shelf crossovers have a jumper on them so you can select 4 ohm or 8 ohms, but it is a little sketchy how that can possibly work without have double components on the board.
Better to build your own even if you use very basic generic designs.
Steve/bluewizard
We can work this out simply by using at basic on-line crossover calculator -
Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)
Using a simple First Order filter, we calculate the values for a crossover at 1000hz with 8 ohm drivers -
C1 = 19.875 uF
L1 = 1.234 mH
Now we change the driver impedance to 4 ohms and determine what frequency gives us the same component values.
FC1 = 2000hz (19.875uF)
FL1 = 500hz (1.234 mH)
So, the High Frequency shift UP by an octave, and the Low Frequency shifts DOWN by an octave, leaving a 1500hz gap in the middle.
Given the question you are asking, one can only assume you have either an Off-The-Shelf crossover or you have something you've scavenged from another speakers. This is a waste of time.
The components necessary for a basic crossover are not that expensive, and there are many crossover calculators on-line. As well as available software to design and model crossovers.
Further, if you design your own, you can determine the impedance of your specific drivers at the crossover frequency, and use that value in your crossover calculations for more accurate results.
Dayton off-the-shelf crossovers have a jumper on them so you can select 4 ohm or 8 ohms, but it is a little sketchy how that can possibly work without have double components on the board.
Better to build your own even if you use very basic generic designs.
Steve/bluewizard
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It is not about what you intended, it is about the design intent of the original 8 ohm crossover. It was intended to do something, which it will no longer do if you change the load impedance.
Now, if you have some special or unique intent then you need to make that specific intent clear to all.
Steve/bluewizard
So when you say "overlap" that means the overall response will actually dip because the overlapping frequencies cancel out right?
Ok, so here's the final test question (you might say it's a "loaded" question):
If the amp source impedance is 4 ohms and the two speakers are 4 ohms and there's some overlap in in the crossover because it's designed for 8 ohms and I blast the amp with a sine wave at the crossover frequency, will it burn up the amp?
Ok, so here's the final test question (you might say it's a "loaded" question):
If the amp source impedance is 4 ohms and the two speakers are 4 ohms and there's some overlap in in the crossover because it's designed for 8 ohms and I blast the amp with a sine wave at the crossover frequency, will it burn up the amp?
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