I'm building a sub and sat system. There is a 2-way system for the sat and is succesfully built. The sub is got from car subwoofer. It has a built-in passive low-pass crossover where crossing point is at 120 Hz. For the first time listening without additional sub to sat crossover, it gave me satisfied but for a long time listening I'm thinking to build the high-pass crossover for the sat. Currently, I have the stocked components: 3.5mH and 5.6mH inductors, 68uF and 220uF capacitors. I know that it's not correct to build crossovers without basing on driver's specific data or measurement, but this project needn't to be perfect, just a system for a pc set up for game playing or listening to music in some times. From online calculator, it yields 4 combinations with different crossover points and Q as follows:
3.5mH + 68uF --> 326 Hz, Q = 1.12
3.5mH + 220uF --> 181 Hz, Q = 2.01
5.6mH + 68uF --> 258 Hz, Q = 0.88
5.6mH + 220uF --> 143 Hz, Q = 1.59
I'd like to ask for your opinion which one would you choose among these combinations?
3.5mH + 68uF --> 326 Hz, Q = 1.12
3.5mH + 220uF --> 181 Hz, Q = 2.01
5.6mH + 68uF --> 258 Hz, Q = 0.88
5.6mH + 220uF --> 143 Hz, Q = 1.59
I'd like to ask for your opinion which one would you choose among these combinations?
Choose the one that sounds best. Without measurements, it's shot in the dark to guess which is the best.
Hmm... Both crossover points have to be the same, unless you deal with the phase difference in some other way (wich you easily can by moving the centerbass around) and the drop in output is compensated in some way (for example a room response bump). So the 143 Hz alternative is the best one. On the other hand, most crossovers have a lower Q, 0.5 to 0.7 (high Q give a rise around the crossover frequency) so the Q = 0.88 is to prefer... A simulation in LTspice is nice, you can put up both filters and look at the responses in the same graph.
Or just build one and listen, then build another if you want to. Soldering is fun.
Or just build one and listen, then build another if you want to. Soldering is fun.
We can't derive the final acoustical Q (that's what matters) from the electrical Q of the filters only.
I found the schematic of a passive subwoofer; Canton Plus C. It was labeled 120Hz crossover frequency. For its high-pass section, it consists of a 200uF cap and a 3.5mH inductor. Putting them in an online calculator, the result showed 190Hz crossover point and Q = 0.96. Unfortunately, this was designed for 4-ohm sat speakers (the Canton Plus S). My sat was rated at 8 ohms. So, it might a good idea that should my sat crossed at around 200Hz with Q approx. 1 (Chebychev alignment). There were much related to my choices. This made me confused.
Please, forget the online calculators, those are works only if the driver impedance and frequency responses are straight flat, but with realworld electrodynamic drivers, these responses are more like a roller coaster and we don't even considered in the room response, which is pretty significant at the lower end of the spectrum.
Sometimes discussions sound arm-chair, like nobody has actually tried to reliably hear differences in Q (hint: impossible in one lifetime).... or if your circuit parts get scrambled during a hurricane, betcha you won't come back to the same settings.
Today, there is one sure and smart way. Borrow or buy (as cheap as the copper for a crossover) a DSP. Fool with the crossover parameters till you have the best sound you can dial-in. Takes little time. Then if you have already bought crossover components, sell them on eBay and use the DSP (or try to replicate the DSP electric output to the drivers).
B.
Today, there is one sure and smart way. Borrow or buy (as cheap as the copper for a crossover) a DSP. Fool with the crossover parameters till you have the best sound you can dial-in. Takes little time. Then if you have already bought crossover components, sell them on eBay and use the DSP (or try to replicate the DSP electric output to the drivers).
B.
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Ok, I’ll leave the online calculators there for a real-life. Yet, let’s talk about the fact of ‘Q’. It’s interesting that whether differences in Q can be heard. I tried to go with an extreme case, set Q as a very high value (sorry, this time the calculator is needed to help), such as Q=3. When Q is high, the frequency response at crossover point becomes rise or goes overshoot. Seem as it’s boosted. So, can’t we hear the boosting on the frequency response? Or is it really boosted in the real world?
If the bump of a high Q filter is at the same frequency where the driver's acoustical response (without the filter) have a dip, then you can have a lower final acoustical Q than the filter Q may suggests alone, because the filter Q and the driver's acoustical Q equalizes each other.
Yes you can hear the elevated response so yes, it's really elevated in the real world.
I'm not sure why you'd want or need to elevate the response at the crossover frequency in this case. I'd think that you'd be looking to elevate the response below the crossover frequency more akin to a lower shelf. Doing what you propose at the crossover frequency will undoubtedly mess with the lower midrange in a negative way ie. voices here will be overbearing.
I'm not sure why you'd want or need to elevate the response at the crossover frequency in this case. I'd think that you'd be looking to elevate the response below the crossover frequency more akin to a lower shelf. Doing what you propose at the crossover frequency will undoubtedly mess with the lower midrange in a negative way ie. voices here will be overbearing.
Whether you can hear Q depends on what the result looks like after you correct the speaker, (but not when you compensate the room or the cabinet externally).
Resonance to fix resonance, or ringing to advantage
Resonance to fix resonance, or ringing to advantage
Finally, I ended up with 5.6mH + 82uF providing 235Hz cut-off; Q = 0.97. Now, there's an issue about the phase. I'm reluctant to wire the sub reverse or non-reverse polarity. For the example of Canton Plus C, it is reversed-polarity on the sub. But, some other brands regret to reverse the polarity. Both of them have the same circuit topology. Could anyone please help to suggest about any ideas on this matter?
That's not the best thing to worry about. If reverse sounds better then it's a start.
You also have the rate of phase change to consider. You might end up flipping some of those component values as well as polarity looking for an improvement.
Then the room positioning. All else depends on it so don't leave it until last.
You also have the rate of phase change to consider. You might end up flipping some of those component values as well as polarity looking for an improvement.
Then the room positioning. All else depends on it so don't leave it until last.
+1 for AllenB. Only way to choose polarity is to test with a DPDT switch once in the room. But then, if polarity is just a coin-toss*, why calculate all the rest so accurately?
BTW, just for laughs, try re-calculating your XO but this time with the very wide tolerances of your coil and electrochemical capacitor, at tops and bottoms of their tolerance ranges.
Need I say again, best way is with a DSP and the reverse engineer the XO to produce the same drive to the speakers.
B.
*I've done the sub polarity test a lot of times - my subs are never too close to my large ESL panels. Funny, no way to guess and often a matter of taste which compromise plot is best. But a REW and a mic (even a laptop mic) will help you decide quickly. Hint: takes about a half-second to switch polarity with my Behringer DSP.
I'd tried again on trial and error to reverse and not reverse the sub polarity. This is just to share to anyone who is in the same situation with me. It provided audibly different results. With non-reversed polarity, I can hear there was a gap between sub and sat. The voice seemed to be thin in lower range and clear in upper range. While, reveresed polarity provided full and thick voice, perhaps continuous transition from bass to mid. Indeed, I like them both. Yet, I'm thinking it would be better if there was a 90 degrees phase-shift option since both of these performings only established 0 or 180 degrees phase shift.
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It's not the phase causing the heavy sound. It's the response. However the phase is contributing the response.
You could try changing your crossover. You could try changing your room positioning.
[sometimes phase runs in and out from low to high frequency because the slope is different between bands]
You could try changing your crossover. You could try changing your room positioning.
[sometimes phase runs in and out from low to high frequency because the slope is different between bands]
By "response" I think you are talking about the signal level.
But of course it is both or even mostly "the phase". That's because the problem is one of polarity (AKA phase) changing the sound in the absence of any level change of the signal to the speakers.
All those elaborate arguments at this forum about precise adjustment of XOs (and deep, deep thoughts about Zobel corrections) are near meaningless when we are talking of stand-alone sub cabs or two or three of 'em in a room. Beyond the basic division of frequencies, just an empirical mix and match.
At sub wavelengths, say 20 feet, phase matters a lot as the two drivers work together across the XO region - which can be a substantial part of the band for a sub that is handling just a two 8aves or so.
(But other than speakers summing into a room at low frequencies, I believe fussing about phase management and coherence is a misapplication of physics theory to human perception.)
B.
But of course it is both or even mostly "the phase". That's because the problem is one of polarity (AKA phase) changing the sound in the absence of any level change of the signal to the speakers.
All those elaborate arguments at this forum about precise adjustment of XOs (and deep, deep thoughts about Zobel corrections) are near meaningless when we are talking of stand-alone sub cabs or two or three of 'em in a room. Beyond the basic division of frequencies, just an empirical mix and match.
At sub wavelengths, say 20 feet, phase matters a lot as the two drivers work together across the XO region - which can be a substantial part of the band for a sub that is handling just a two 8aves or so.
(But other than speakers summing into a room at low frequencies, I believe fussing about phase management and coherence is a misapplication of physics theory to human perception.)
B.
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A decent crossover design implies, at the least, similar/complimentary phase tracking through the crossover region. I would have thought that is a given around here. The posters question regarded differences in Q factor. That, of course, will effect response .. all other criteria being equal.