{ Renewed 2-7-2020 } Talk about phase adjustment of Subwoofer 1+1= ?

yrneh

Before the topic . First we need to remember how a speaker or a subwoofer producing sound : Sound is produced by the action of movement ( Push and pull ) of speaker unit (喇叭單元).

What is same phase ( 0 deg. Between speakers *note) of sound produced between speakers : The movement of push or pull action of speaker unit in an instant moment between two or more of speakers are the same. That same phase action will increase the volume of sound produced ( correct phase ).
E.g. front speaker doing push action, and subwoofer is doing push action also. That means same phase between them. ( correct phase )
Something like (+1) + (+1) = 2


What is opposite ( 180 deg. Between speakers * note ) phase of sound produced between speakers : When one speaker unit moving “push” but another speaker unit “pull” . In that instant moment , that opposite movement cause the volume of sound eliminated抵消 by each other ( wrong phase).
E.g. front speaker doing push action, but subwoofer is doing pull action. That means wong phase between them.
Something like (+1) + (-1) = 0

(* note : 0 deg or 180 deg is a relative value between two speaker, which does not means your subwoofer to be setup on 0 deg.)


Why active power subwoofer need phase correction for adjustment : Because the delivery time from signal processing ,power production from your AV Amp to your front speaker may different to the time delivery of power amp inside your subwoofer . That time different equal to phase different. So we need to adjust it by turning the phase correction on your subwoofer . The phase correction means time correction = delaying the subwoofer in oder to match up the phase of front speaker .


How to setup ( correct ) the phase of your subwoofer : ( In my own opinion)
1, Disable or lower the Crossover frequency of front speaker from the setup manual of AV Amp. And higher the Crossover frequency on back panel of subwoofer.
( Because we can only observe the overlapped frequency sound produced from front speaker and subwoofer on this physical practice . Because enable crossover setting will cut off the signal of overlapped frequency, that will fail the observation )
2, Play a low frequency sound (heavy bass +- 40 to 120 Hz) from your player . ( e.g. phone app < subwoofer test tones >  )
3, Adjust subwoofer volume level similar to front speaker volume.
4, Adjust the Phase switch on your subwoofer (Note 2 *) until the largest volume of bass have heard .

If you find the largest volume production phase angle , means that you got the correct phase now, finally you figure out 1+1=2 right now , a little bit far away from the day of your kindergarten graduation , congratulation!


Note 2* Your can also adjust the phase from the setup manual of some AV Amp by step of every 1 deg. if your subwoofer have not enough detail of adjustment .eg only 0 & 180 deg. My Denon AVR-6400H have that function.




For Denon user : To disable crossover just select LEF + Main on the bass setup at AV Amp, and set Large to the front speaker

ekek

Good technical sharing!

BTW, why subwoofer signal must faster than front speakers as it is default to delay the subwoofer from 0 to 180 only.

yrneh

ekek 發表於 2020-6-29 15:57
Good technical sharing!

BTW, why subwoofer signal must faster than front speakers as it is ...

Because nobody can catch the future signal, before we create the time machine .
So we can only choose delay the signal to match the phase

By the way , I don't mean subwoofer signal must faster than front speakers. It may be later than the front speaker. But subwoofer adjustment can only go further delay. in order to synchronize the phase , it should go to the next cycle. That only my physical imagination. Please correct me if I getting wrong.

ekek

yrneh 發表於 2020-6-29 16:16
Because nobody can catch the future signal, before we create the time machine .
So we can ...

IC, thank you.
I think no one can sense the delay of 1Hz of sound between subwoofer and front speakers.
So the main purpose is to set to in phase of subwoofer and front speakers.

yrneh

ekek 發表於 2020-6-29 16:25
IC, thank you.
I think no one can sense the delay of 1Hz of sound between subwoofer and front spea ...

Agree

yrneh

Phone apps for tuning subwoofer phase

Introduce some free phone apps for your subwoofer tuning, hope you enjoy that

1, App name < subwoofer test tone  >, the apps produce continuous frequency signal ( can be adjusted between 20-99HZ ) . Connect you phone to your AV Amp with bluetooth , advise you to play the freuuency between 60-100Hz ( because that the overlapping frequency between front speaker and subwoofer )

2, use another phone to install < Sound level meter >, use that app to find out the large volume ( correct phase ) of your subwoofer.