ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 2 3 [4] 5   Go Down

Author Topic: Phase align subs to mains  (Read 4099 times)

Ryan Hammond

  • Newbie
  • *
  • Offline Offline
  • Posts: 16
Re: Phase align subs to mains
« Reply #30 on: March 02, 2014, 05:49:14 pm »

Wow... it all makes sense, but I never gave it a second thought... I just assumed that they were in phase... we've all heard the obvious phase issues with mains, but it never occurred to me that the subs and mains could be off. This is why I have only been concerned with polarity and not the phase relationship to mains. Our subs have always been very close to the mains. ... it all "sounds" in line throughout the venue.

« Last Edit: March 02, 2014, 05:52:30 pm by Ryan Hammond »
Logged

Mac Kerr

  • Old enough to know better
  • Administrator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3428
  • Audio Plumber
Re: Phase align subs to mains
« Reply #31 on: March 02, 2014, 05:54:11 pm »

Wow... it all makes sense, but I never gave it a second thought... I just assumed that they were in phase... we've all heard the obvious phase issues with mains, but it never occurred to me that the subs and mains could be off. This is why I have only been concerned with polarity and not the phase relationship to mains.

No, they will still need to be phase aligned, but the alignment will work over most of the coverage area. The phase of the signal coming out of a speaker is affected by crossover design, box design, driver selection, and electronic treatment. The idea is to use the electronic treatment to correct the errors induced by all the other influences.

Mac
Logged

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3567
  • Atlanta GA
Re: Phase align subs to mains
« Reply #32 on: March 02, 2014, 06:03:09 pm »

If your mains and subs are very close together, the area of good phase match will be much larger, and it won't matter much where you measure, pick good seats.

Mac
Like where the guy that writes your check sits------------------------
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3567
  • Atlanta GA
Re: Phase align subs to mains
« Reply #33 on: March 02, 2014, 06:13:11 pm »

. Our subs have always been very close to the mains. ... it all "sounds" in line throughout the venue.
But simply "being physically close" DOES NOT mean that they are in phase.

What Mac was saying was that if the subs and the mains are close together-then the relative distances between the two will be the same over a wide area.

If the subs are on the floor and the mains flown-almost everywhere you move you will end up with a different delay time-hence the need for the "good seats".

When the subs and tops are properly aligned-there will be more impact-clarity etc to the music.

AND REALLY IMPORTANT-that MAY MEAN that they are out of POLARITY!!!!!!!

This if often the case.  Other times it is not-it really depends on the particular cabinets used-the processing that is on them (crossover filter types/slopes/freq etc).  They all have an effect on the actual arrival time.  Steeper slopes cause more "delay".

Hence the reason audiophiles like first order filters-because of the gentle slopes and it is much easier to align different passbands with gentle slopes.  But the gentle slopes don't offer much protection to the drivers-so it is a trade off.

It really does not matter what the polarity is-it is the PHASE RELATIONSHIP that you are interested in.  And different cabinet combinations will have different relationships.

Just the simple action of putting a low pass filter on the subs will throw their "arrival time" off-even if they are sitting right next to the mains.

And if you are using horn loaded subs-there will be additional delay inside the cabinet.

To be honest I never worry about whether the subs are in polarity with the mains-it is simply the phase that is most important.

And with the phase trace you can VERY QUICKLY tell if they are out of polarity-much faster than with a "clicker" or "polarity checker".
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Jay Barracato

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1325
  • Solomons, MD
Re: Phase align subs to mains
« Reply #34 on: March 02, 2014, 06:14:10 pm »

Measurements can give you answers, but you have to know what questions you are asking.

The best measurement system can only suggest the results of choices you have made. Experience tells you what those choices might be.

I think negative information is also important. A lot of times you will hear experienced system techs talking about things that can't be fixed by alignment or eq. If you find yourself working in a circle and redoing over and over what you already changed, odds are you have stumbled against something that can't be fixed. Also, another piece of negative information is that you must be able to get consistent measurements before you can make consistent predictions based on the measurements.

Beware on anything with the word "wizard" in its name. It is the antithesis of effective measurement/testing.

Sent from my DROID RAZR HD using Tapatalk

Logged
Jay Barracato

Ryan Hammond

  • Newbie
  • *
  • Offline Offline
  • Posts: 16
Re: Phase align subs to mains
« Reply #35 on: March 03, 2014, 09:27:14 pm »

No, they will still need to be phase aligned, but the alignment will work over most of the coverage area. The phase of the signal coming out of a speaker is affected by crossover design, box design, driver selection, and electronic treatment. The idea is to use the electronic treatment to correct the errors induced by all the other influences.

Mac

Well, to be honest, I've never had to mess with it. ... and I'm glad I never had to; however, I have checked the polarity of our subwoofers just to try out the app. As for phase, it's never been an issue; although our system is an install with custom DriveRack settings.
« Last Edit: March 03, 2014, 09:39:59 pm by Ryan Hammond »
Logged

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3567
  • Atlanta GA
Re: Phase align subs to mains
« Reply #36 on: March 03, 2014, 09:43:31 pm »

Measurements can give you answers, but you have to know what questions you are asking.

The best measurement system can only suggest the results of choices you have made. Experience tells you what those choices might be.


And the exact same thing goes for prediction programs. 

They only show you the RESULT of your "design".  They do not show or tell you what to put in.

It is your EXPERIENCE AND KNOWLEDGE that determines what might or might not work.

There is no replacement for experience.
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Cailen Waddell

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 455
Re: Phase align subs to mains
« Reply #37 on: March 04, 2014, 08:51:33 am »

So...  Maybe my last question, when working with a system that is L/R with a mono center ground stack sub cluster, would you run pink through the whole system or just left and the subs then right and the subs.  In my head, if the subs are equidistant from the left and right, it would seem to be that if the relationship between left and sub is correct the relationship between right and sub is correct?

I am also assuming that this is a proper l/r system where each side fully covers the audience. Which maybe leads to a second question - in a stereo system, there is inherently a lot of phase interaction between sides due to spacing - yes?  Do you try to fix that or just accept that it is a disadvantage of stereo versus a mono center cluster....

I'll add that this is mostly an academic interest for me.  I know enough to know I don't know enough to do this, and with our installs especially, it's better to let  people who are good at this due system tuning. That said, playing around with our portable B right better understand the concepts is something I might do...
Logged

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 12946
  • Wichita, Kansas USA
Re: Phase align subs to mains
« Reply #38 on: March 04, 2014, 10:06:22 am »

So...  Maybe my last question, when working with a system that is L/R with a mono center ground stack sub cluster, would you run pink through the whole system or just left and the subs then right and the subs.  In my head, if the subs are equidistant from the left and right, it would seem to be that if the relationship between left and sub is correct the relationship between right and sub is correct?

I am also assuming that this is a proper l/r system where each side fully covers the audience. Which maybe leads to a second question - in a stereo system, there is inherently a lot of phase interaction between sides due to spacing - yes?  Do you try to fix that or just accept that it is a disadvantage of stereo versus a mono center cluster....

I'll add that this is mostly an academic interest for me.  I know enough to know I don't know enough to do this, and with our installs especially, it's better to let  people who are good at this due system tuning. That said, playing around with our portable B right better understand the concepts is something I might do...

You want the fewest variables in each individual measurement, so you'd start by using just the Left or Right and the subs.  Decide which seat in the house is the alignment point, put your measurement mic there (ground plane, or at least a big, flat surface like a console lid, sheet of plywood or even a couple of banquet tables laid over the seats).  I start with an impulse response measurement for the tops, and then the bottoms.  This is to show if the tops or subs are "leading" in time.  You can use Smaart's Delay Finder, but I like to look at the IR and coherency trace to see if there is anything funny going on (reflections, ground bounce, etc) that might confuse the DF.  Once I'm confident that the pass bands are relatively close I'll move to the phase alignment.

If your install is symmetrical then you can *presume* L/R to be the same, but I think it prudent to prove it to be so.

With a multiple loudspeaker system there will be time issues because every audience member occupies a different place relative to the loudspeakers.  You accept this and move on, unless there is a problem with a mono source (like the pastor's mic).  Such issues will not be eletronically corrected without creating new issues in other parts of the room, and likely indicate flaws in the basic design concept.

Set up a small rig and experiment.  Seriously.  It's the only way you'll get to understand both measurement and alignment.  After you make a couple hundred invalid measurements and recognize them on the screen, you'll begin to move much more quickly.  Trust me, I made hundreds of stupid mistakes while learning measurement; fortunately my ears told me to ignore the pretty picture on the computer...
Logged
Chewing through your wimpy dreams
They eat without a sound,
Digesting England by the pound.

Jay Barracato

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1325
  • Solomons, MD
Re: Phase align subs to mains
« Reply #39 on: March 04, 2014, 03:42:26 pm »

Or take measurements of systems you already know are aligned/ that you like the sound of. After a while you will start to recognize what good sound likes.

When I first started measuring on a regular basis, I know I probably amused some system techs by approving the system based on playback and then setting up to take a measurement. I was looking for the attributes I liked.

Sent from my DROID RAZR HD using Tapatalk

Logged
Jay Barracato
Pages: 1 2 3 [4] 5   Go Up
 


Page created in 0.095 seconds with 23 queries.