ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2]  All   Go Down

Author Topic: Smaart procedure for aligning subs and tops  (Read 93600 times)

Merlijn van Veen

  • Moderator
  • Sr. Member
  • *****
  • Offline Offline
  • Posts: 309
    • www.merlijnvanveen.nl
Re: Smaart procedure for aligning subs and tops
« Reply #10 on: January 08, 2015, 04:21:37 pm »

Hi Everybody,


First I'd like to compliment Mark for his good idea and I'm sure that with combined effort a solid protocol can be devised.

Simultaneously I feel that such an elusive subject could benefit from some clear graphics so I gave it a try. The images attached where created with the greatest effort within the confinement of my Macbook OS using plug-ins. They're free from noise and exhibit realistic phase behavior.

I'd like to start by saying that I'm not a great fan of using the auto delay locator for finding the subwoofer IR. Under controlled circumstances it might work but in practice there's often to much background noise, poor SNR and insufficient data for the analyzer to work with. When using band limited products like subwoofers, less than 1% of the data sent is returned. Only after maximum zoom the IR becomes visible and is clearly stretched over time by acoustical-mechanical design and the phase shift introduced by electronic filters. The main speaker on the other hand has less than 1% of its bandwidth cut and 99% or more of the data sent, is returned for the analyzer to work with resulting in a solid IR.

Check the MS webinar on IR for a better understanding.

http://meyersound.adobeconnect.com/p9o4ms85n0y/

The IR can be used very much to get you into the ballpark but so does a laser distance finder or tape measure. I use the IR but set it manually to where the waveform starts to deviate (take shape) from the zero line. And yes in order to be able to see it I'll have to zoom in maximally.

Like mentioned before, what matters is that the phase slopes of both speakers match and I strongly recommend with as little phase shift as possible. Definitively less than 120 cause this will gain you nothing and neither will you lose anything. IMHO 90 is also not an option cause you'll only gain +3 dB and waste half of your amp's electrical power. 60 is better but try and go for 30 or less and achieve maximum efficiency.

The speaker with the steepest slope at the XO frequency is late to the party. Apply delay to the speaker with the gentle slope. Once you have matched slopes with equal tangents but not necessarily overlapping traces, a 180 phase shift might be visible for all frequencies of interest throughout the XO region which can be solved by reversing the polarity of one of both speakers.

If you don't like the diagonal phase slopes to work with, you can manipulate the phase response plot by playing incrementally with the delay locator setting to "flatten" the portion you're interested in as illustrated in figure 6. Just make sure once you settle on a certain delay locator time to leave it alone. This will be your frame of reference to find the relative amount of time difference.


Regards,


Merlijn

Peter Vetters

  • Newbie
  • *
  • Offline Offline
  • Posts: 6
Re: Smaart procedure for aligning subs and tops
« Reply #11 on: January 08, 2015, 04:30:43 pm »

Right click and "draw" a box (mouse) over the area you want to zoom into.

Thanks Ivan, this helps me further! For me, it is not exactly as you describe, I'm a Mac user you know, and that's probably the reason I didn't find it myself. For Mac you must push "Ctrl" during drawing "the zoom box".  ;)
Logged

PiotrSkotnicki

  • Newbie
  • *
  • Offline Offline
  • Posts: 1
Re: Smaart procedure for aligning subs and tops
« Reply #12 on: February 03, 2015, 09:34:51 am »

Hi to all,

Here is Bob McCarthy's take on the question: https://bobmccarthy.wordpress.com/2010/02/08/phase-alignment-of-subs-why-i-dont-use-the-impulse-response/

Regards, Piotr.
Logged

ProSoundWeb Community

Re: Smaart procedure for aligning subs and tops
« Reply #12 on: February 03, 2015, 09:34:51 am »


Pages: 1 [2]  All   Go Up
 



Page created in 0.1 seconds with 25 queries.