Which phase is better

[Darek K]

We have two similar SPLs (especially below 100Hz).
Green this is real mesurment, main + EQ+ crossover 100Hz/24dB, sub+EQ + croosover 100Hz/24dB, put into minidsp
Red this is REW's prediction A+B (main+sub without and crossover) and than to EQ and return as "Generate mesurment as predicted".

Assuming red is not predicted but real mesurment, which phase is better ?

 

[ppataki]

You need to use the Unwrap Phase option then use Overlays --> Phase to put them on top of each other
Make sure that they are aligned (push the +360, -360 buttons until they are leveled at 0 degree)

 

[Keith_W]

Please read this thread.

There are too many uncertainties in your post, starting with whether you have taken the measurements correctly. Also, putting measurements side by side like that makes it very difficult to compare. It is better to post the MDAT. But ultimately, "better phase" does not matter because it is secondary to the frequency response.

 

[Darek K]

Thank you.
The topic of acoustics is still new to me, and I have a feeling it will remain so forever (if only for linguistic reasons). Although... after many, maany years of dabbling in photography, I can say I'm a pretty good amateur photographer.

I'm not even sure "dabbling" is the right word here.
I hope to be a better friend.
Darek

 

[DVDdoug]

The main speaker and subwoofer should be in-phase at the crossover frequency (where both speakers are operating). Otherwise the soundwaves will cancel each other and you'll get a dip in frequency response. The absolute polarity isn't important.

Due to the speed of sound, distance makes a delay and a related phase shift so if the subwoofer is closer or farther than the main speakers that can also make them out-of-phase, depending on the wavelength. 100Hz has a wavelength of about 10 feet, so 5-feet is half a wavelength, or 180 degrees. At 10 feet, that's 360 degrees and they are back in phase.



Here's an experiment for you... If you have regular passive speakers, try reversing the +/- connections on one speaker. (That's not as easy if you have powered/active speakers). Without the subwoofer and the speakers operating in opposite polarity the bass will be mostly canceled and you'll hear some other "phase weirdness". If you reverse the connections to both speakers so they are operating in-phase with each other everything will be normal again.

The topic of acoustics is still new to me, and I have a feeling it will remain so forever.

You can learn a lot but it's specialized physics. I'm not sure if you can get a college degree in acoustics but if you were studying architecture you could probably take an advanced acoustics course and specialize in architectural acoustics.

 

[Darek K]

There are certain traps that lurk for the beginning audio-sound-phile.
One of these traps is jumping "right into the thick of it."
For me, it was the YouTube videos from OCA. Now I understand that they weren't for me, but for someone advanced in the field of loudspeakers and acoustics.
I saw individual trees instead of the entire forest. I saw phases and delays instead of just the overall effect – frequency response.

I am not sure "right into the thick of it." it is proper for this situation but maybe it should be "just in the middle of the matter". This is Google translation.
Polish idioms are "jump into the deep water" or "like a plum in a compote"