Crossover point decision help needed

I decided to add the subwoofers to the existing 2-way speakers. However, I will only apply low-pass filters to the subs and no hi-pass filters to the mains. I believe this design is a 2.5-way system, thus I've posted this thread to the Multi-Way forum.

Anyway, I have two 3.3mH inductors and two 80uF and 390uF capacitor pairs.

From online calculator, I could form two second-order low-pass filter combinations as follows:

A) 3.3mH + 80uF = 300Hz, Bessel alignment
B) 3.3mH + 390uF = 150Hz, Chevbychev alignment (with +3dB at 150Hz)

According to what I've read on the forum, some people believe bass begins to count below 400Hz, thus, option A) be sufficient. However, some individuals believe that the subwoofer should be switched off as low as feasible, therefore option B) may be preferable.

Overall, which choice should I choose?
 
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After I did a research further, I discovered that most 2.5 way speakers have crossover point at around 300-400 Hz, whereas the subwoofer and satellite systems usually have about below 200 Hz crossover.

The question has arisen that which type of system should be considered; 2.5 ways or sub & sat?
 
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I decided to add the subwoofers to the existing 2-way speakers. However, I will only apply low-pass filters to the subs and no hi-pass filters to the mains. I believe this design is a 2.5-way system, thus I've posted this thread to the Multi-Way forum.

Anyway, I have two 3.3mH inductors and two 80uF and 390uF capacitor pairs.

From online calculator, I could form two second-order low-pass filter combinations as follows:

A) 3.3mH + 80uF = 300Hz, Bessel alignment
B) 3.3mH + 390uF = 150Hz, Chevbychev alignment (with +3dB at 150Hz)

According to what I've read on the forum, some people believe bass begins to count below 400Hz, thus, option A) be sufficient. However, some individuals believe that the subwoofer should be switched off as low as feasible, therefore option B) may be preferable.

Overall, which choice should I choose?
Having no high pass to the main speakers, and two subwoofers crossed quite high, 300Hz, may result in excessive upper bass energy, where there is too much overlap.
Typically, if you run main speakers full without high pass, you want to cross subs as low as possible.
Consider high pass for main, it will result in lower distortion in midrange and highs.

https://www.audioadvisor.com/mobile/prodinfo.asp?number=PACX1002
 
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After I did a research further, I discovered that most 2.5 way speakers have crossover point at around 300-400 Hz
Yes, and most of them have two same woofers, the lower one with 1st order cut. Just inductor in series.

whereas the subwoofer and satellite systems usually have about below 200 Hz crossover.
I believe 80-120 Hz is most common for sub&sat systems.

The question has arisen that which type of system should be considered; 2.5 ways or sub & sat?
My vote is for sub&sat. Unfortunately, not easy to implement with pasive XO due interactions with subwoofer driver impedance peak(s).
 
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I'd check the X-over with 3,3mH and 390µF. That will about short your amp. 1Ω at 150Hz (assuming an 8Ω load).
VituixCAD Impedance.png
 
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assume its 4 ohm
coil is too small for 300 and 150 Hz at 8 ohm

but good point the woofer needs to be close to the main Satellite speakers.
at such a high crossover.

it will sum strange with no high pass. either boost or cancel depending on polarity.
maybe Bessel.
even very basic Frequency response and impedance curve data for the 2 ways would help a lot.
and woofer data.

even a basic sim would tell you slightly more accurately what the actual impedance is at 300 or 150 Hz
for the woofer.
 
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As you did not discribe your whole system (speaker, sub and amp) there is no prediction possible other than it will not work well in an objective auditioning.
Anyway, your ears may adapt to it, so it could please you after some time of listening.

The result of 2.5 way without high pass will be pure coincidince, effected by chassis, distance, positioning and room.

A single 80Hz low pass may work in such a set-up, but this needs passive components more expensive than a sub amp with a build in active x-over.
 
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Could anybody assist to simulate the response and impedance curve of the lowpass filter of option A and B for me, please? The sub is 4 Ohms.

I, actually, have a XSim program in my computer. Unfortunately, my computer is currently in the repair shop. I now have only a mobile phone in my hand. Thank you in advance.
 
…I will only apply low-pass filters to the subs and no hi-pass filters to the mains…”
In that case, your filter should depend entirely on the response of the system in its environment. Tinker with the values on your low pass to the subs, while playing music and tones on them, along with the mains. Don’t bother about theoretical alignments. You might come across a filter that works well, but is theoretically bizarre, with a lower cut-off. Phase works like that. There’ll be at least one major room peak/dip you can try to compensate for.