Subwoofer phase adjustment

[slartibartfast]

My sub has a 0-180 phase adjustment. Now this might be a daft question but does this have any effect when connecting via the sub out of the WiiM Amp. In this case bass management is handled by the amp and the low pass filter on the sub is bypassed. I suspect the phase adjustment is also bypassed as I read that the phase adjustment is only effective at frequencies close to the LPF setting.

 

[harkpabst]

The phase adjustment 0⁰ or 180⁰ should breather be called "polarity", but unfortunately the term "phase" is all over the place. It's the newly added delay setting that allows for continuous phase adjustment.

Generally the polarity switch always affects the entire output of the subwoofer. This is true formthe sub as well as for the WiiM Home app. However, if you are using WiiM's bass management then the mains are high pass filtered, so for frequencies noticeably lower than the crossover frequency there is no meaningful output from the mains anymore. Nothing that could interfer with the sub's output.

The sub knows nothing about big your amp/pre-amp/receiver provides bass management or not. Consequently, the function of the 180⁰ phase or polarity switch cannot change based on that.

If your sub has a dedicated LFE input or a dedicated LFE configuration setting, the with this input being used or this config being enabled the sub might not be affected by the switch ... or it just might.

You really have to look it up in your sub's manual.

 

[rccarguy]

"However, if you are using WiiM's bass management then the mains are high pass filtered, so for frequencies noticeably lower than the crossover frequency there is no meaningful output from the mains anymore. Nothing that could interfer with the sub's outpu"

Not quite. The crossover isn't a brick wall, either 12 or 24db octave slope for sub and/or speakers (if you have that option) there will be interactions between sub and speakers, cancellation, boosting at various frequencies etc. All depending on speaker and sub location, the delay in your subwoofer, crossover slopes, phase crossover setting, gain etc.

 

[harkpabst]

"However, if you are using WiiM's bass management then the mains are high pass filtered, so for frequencies noticeably lower than the crossover frequency there is no meaningful output from the mains anymore. Nothing that could interfer with the sub's outpu"

Not quite. The crossover isn't a brick wall, either 12 or 24db octave slope for sub and/or speakers (if you have that option) there will be interactions between sub and speakers, cancellation, boosting at various frequencies etc. All depending on speaker and sub location, the delay in your subwoofer, crossover slopes, phase crossover setting, gain etc.

"... for frequencies noticeably lower than the crossover frequency" this doesn't matter. 4th order LR is pretty steep.

I didn't mean to write (yet another) all-encompassing compendium on subwoofers. The point I made (maybe not clearly enough) is that the polarity switch's effect is not limited to the crossover region.

Is that OK with you?

 

[slartibartfast]

The phase adjustment 0⁰ or 180⁰ should breather be called "polarity", but unfortunately the term "phase" is all over the place. It's the newly added delay setting that allows for continuous phase adjustment.

Generally the polarity switch always affects the entire output of the subwoofer. This is true formthe sub as well as for the WiiM Home app. However, if you are using WiiM's bass management then the mains are high pass filtered, so for frequencies noticeably lower than the crossover frequency there is no meaningful output from the mains anymore. Nothing that could interfer with the sub's output.

The sub knows nothing about big your amp/pre-amp/receiver provides bass management or not. Consequently, the function of the 180⁰ phase or polarity switch cannot change based on that.

If your sub has a dedicated LFE input or a dedicated LFE configuration setting, the with this input being used or this config being enabled the sub might not be affected by the switch ... or it just might.

You really have to look it up in your sub's manual.

I am pretty sure now that the continuously variable phase setting between 0 and 180 on the sub is only useful when the sub crossover frequency is determined by the sub itself. When you use bass management you need to use the delay setting as you said.

 

[harkpabst]

... continuously variable phase setting between 0 and 180 on the sub ...

Sorry, I got that wrong. A continuous phase adjustment does deserve the name, but is best left alone when the amp provides its own bass management, indeed.

Since it is not needed, stay on the safe side, leaving it at 0⁰ and adjust everything from within the WiiM Home app.

 

[rccarguy]

Just because you have bass management doesn't mean you should set phase to 0.

AVR's do have distance adjust on the sub woofer, but stereo amps don't. Bass management isn't the same as phase/distance alignment.

If the wiim subwoofer out isn't delayable, or if during the calibration process it pings speakers and sub and then calculates ideal distance for each, then you would need to adjust the subs phase response, ideally with variable phase rather than 0/180 direct switch.

Need to plot responses to see how the three speakers interact, at what frequencies.


I did this on my hifi, a combined full range sweep, with both speakers and sub on, then adjust the subs phase every 15 degrees. You can see the interations.

 

[harkpabst]

Just because you have bass management doesn't mean you should set phase to 0.

AVR's do have distance adjust on the sub woofer, but stereo amps don't. Bass management isn't the same as phase/distance alignment.

If the wiim subwoofer out isn't delayable, or if during the calibration process it pings speakers and sub and then calculates ideal distance for each, then you would need to adjust the subs phase response, ideally with variable phase rather than 0/180 direct switch.

Need to plot responses to see how the three speakers interact, at what frequencies.


I did this on my hifi, a combined full range sweep, with both speakers and sub on, then adjust the subs phase every 15 degrees. You can see the interations.

Sorry, but why are you're not listening?

Nobody said you should not or do not need to compensate for delay.

In WiiM Home this can be done entering a delay in ms for either the sub or the mains. Muchore precise than any old phase dial . So yes, current stereo amps do offer the same functionality as AVRs.

By all means, leave the "phase" switch or the phase dial on your sub at 0⁰ when using the WiiM AMP or the upcoming WiiM Ultra.