Ok, so this is in reference to a car audio coaxial speaker. I'm replacing the original factory 3.5" dash "paper cone tweeter" (8 ohm with 3.3uf electrolytic cap soldered onto the actual speaker wiring harness plug attached to the speaker's basket) with a new 3.5" coaxial (plastic woofer/dome tweeter) that uses the exact same basket as the original speaker. The little plastic clip is on the new speaker's basket to hold the electrolytic cap, but there is no cap, and there is a little strip of bare wire soldered across where the cap would be. BUT, peeking into the coaxial you can barely see a flat/round (ceramic?) capacitor wired to the tweeter on the coaxial speaker.
Now, my question is, if I want to block low bass from going to the new 3.5" coaxial's plastic woofer by inserting a "bass blocker" on the positive lead of the unit at the wiring harness plug, what if any interaction would there be with the flat/round (ceramic?) cap wired to the coaxial's tweeter?
I had read somewhere where someone had said "if you put 2 capacitors in series, the smaller value cap will determine the characteristics of the filter." That blew my mind and now has me questioning my plan to use the bass blocker. I'm not using any type of electronic crossovers at the radio/amp. The speaker is receiving a full range signal.
Now, my question is, if I want to block low bass from going to the new 3.5" coaxial's plastic woofer by inserting a "bass blocker" on the positive lead of the unit at the wiring harness plug, what if any interaction would there be with the flat/round (ceramic?) cap wired to the coaxial's tweeter?
I had read somewhere where someone had said "if you put 2 capacitors in series, the smaller value cap will determine the characteristics of the filter." That blew my mind and now has me questioning my plan to use the bass blocker. I'm not using any type of electronic crossovers at the radio/amp. The speaker is receiving a full range signal.
Sounds like a thermistor, from your description. Probably not. If you use a bass blocker you might bypass it with your crossover cap if you can bypass what is built in already.
Thanks, but I'm not sure I understand your second sentence at all.
And I looked up thermistor and I don't know why they would incorporate a device that changes it's resistance based on temperature on a speaker.
I'll have to pull the speakers to get a better look but as I recall they looked like this... https://www.hobbytronics.co.za/content/images/thumbs/0001465.jpeg
It is probably a small ceramic capacitor on the tweeter.
If the tweeter cap is 1uf and the bass blocker cap is 100uf, the effective size of the tweeter cap is going to be 0.99uf. Don't even worry about it.
If the tweeter cap is 1uf and the bass blocker cap is 100uf, the effective size of the tweeter cap is going to be 0.99uf. Don't even worry about it.
Thanks! My bass blocker was gong to be 200uf.
How do I determine if the tweeter is connected in series or in parallel with the woofer?
Thanks!
The tweeter and the woofer are almost always wired in parallel.
If they were in series, then the 1uf cap would stop all bass frequencies from flowing in the circuit and the woofer would have no bass or even midrange.
To confirm that they are in parallel.
The -terminal of the woofer will be connected to the -terminal of the tweeter. The + input to the drive unit assembly will have one lead going to the + woofer terminal and another lead going into the 1uf cap.
If they were in series, then the 1uf cap would stop all bass frequencies from flowing in the circuit and the woofer would have no bass or even midrange.
To confirm that they are in parallel.
The -terminal of the woofer will be connected to the -terminal of the tweeter. The + input to the drive unit assembly will have one lead going to the + woofer terminal and another lead going into the 1uf cap.
Just a 200 uf cap on your speaker will not actually do much. There needs to be a shunting element between the cap and driver, like a 15 - 22 ohm resistor. The basic crossover charts do not account for the resonant peak at low frequencies.
No, but they are less effective than they could be because they assume that the loudspeaker connected to them is a constant Xohm resistor at all frequencies. An actual driver is definitely not a constant resistance.
See link below.
Series Notch Filter Designer / Calculator Help
Look at the first and second graphs. Ignore the black curve in the first graph. It is incorrect and should not be there.
The second graph shows a typical response curve of driver with its low frequency resonant peak. At the frequency of this resonant peak, the bass blocker (cap) is not a very effective filter due to the increased impedance of the driver at this frequency. The red and blue curves show the expected versus actual response from the filter.
If you put a resistor in parallel with the woofer terminals, this will reduce the peak impedance at the resonant frequency. This will make the filter more effective. It is also going to lower the impedance of the system and decrease its efficiency.
See link below.
Series Notch Filter Designer / Calculator Help
Look at the first and second graphs. Ignore the black curve in the first graph. It is incorrect and should not be there.
The second graph shows a typical response curve of driver with its low frequency resonant peak. At the frequency of this resonant peak, the bass blocker (cap) is not a very effective filter due to the increased impedance of the driver at this frequency. The red and blue curves show the expected versus actual response from the filter.
If you put a resistor in parallel with the woofer terminals, this will reduce the peak impedance at the resonant frequency. This will make the filter more effective. It is also going to lower the impedance of the system and decrease its efficiency.
Yes. I get all that and I appreciate that. My response to that guy was sort of tongue in cheek in regards to the statement that... "a 200 uf cap on your speaker will not actually do much".
Here's an interesting video on the subject... YouTube
His bass blockers seem to be doing a LOT with his 3.5's according to his meters!
I'm using the 199uf audiopipe ones he shows in the box. Their cuttoff begins at 200hz on 4ohms, 6db/octave. I'm just looking to keep the 3.5's from "blowing" at high volumes with very low bass notes.
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