Welcome, Guest
Username: Password: Remember me
NOTE: This is a "Community" forum. Please be mindful that community members are here to help as part of a community effort. We therefore appreciate your effort in keeping this forum a happy place!

If you have a specific issue (e.g. hardware, failure) and want help from our support team, please use our tech support portal (Support menu - > Contact Us).
Thanks a lot of your help in making a better community.

TOPIC:

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 2 weeks ago #59194

  • CarlosdelJunco
  • CarlosdelJunco's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 62
  • Thank you received: 4
Hi alsouza,

Just taking first sweeps - totally psyched!  Which timing reference do you turn on the "loopback" or "acoustic"?

thanks, Carlos

Please Log in or Create an account to join the conversation.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 2 weeks ago #59200

  • altsouza
  • altsouza's Avatar
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 42
  • Thank you received: 11
First you have to connect the Shd to the laptop. The shd is a sound card, so you don't need a external soud card.
In measure page in Rew there is a option to turn on the time reference.
 
The following user(s) said Thank You: CarlosdelJunco

Please Log in or Create an account to join the conversation.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 2 weeks ago #59201

  • CarlosdelJunco
  • CarlosdelJunco's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 62
  • Thank you received: 4
I'd already got everything hooked up and properly connected, thanks.

And then done test sweeps with no timing reference just to make sure things work.

Going to to measurements on the sub first. You had said to make sure timing reference is on...but, which one is better to use "loopback" or "acoustic"? Just googling this now but not yet come up with a clear answer...

Please Log in or Create an account to join the conversation.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 2 weeks ago #59202

  • Ultrasonic
  • Ultrasonic's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
  • Posts: 2280
  • Thank you received: 463
You need to use an acoustic timing reference.
The following user(s) said Thank You: CarlosdelJunco

Please Log in or Create an account to join the conversation.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 2 weeks ago #59204

  • CarlosdelJunco
  • CarlosdelJunco's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 62
  • Thank you received: 4
Thanks for chiming in Ultrasonic.

I did just read the section in the REW manual about using the acoustic timing reference setting...so much to learn!

Ok, going to get my feet wet and learn as I go.

Please Log in or Create an account to join the conversation.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 2 weeks ago #59208

  • CarlosdelJunco
  • CarlosdelJunco's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 62
  • Thank you received: 4
Hi Ultrasonic, Two steps forward and one back...I'm guessing when just testing for the sub, I don't turn on the acoustic timing reference?

If I do (and have leave alone "Timing offset" and "Ref level trim" in the next two boxes below), I get a message on the progress bar of the sweep (even though the sweep has finished) saying "waiting for timing reference". And then it does not generate a graph.

Should I be worried that my reading (even with 1/6 smoothing)

Please Log in or Create an account to join the conversation.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 2 weeks ago #59209

  • CarlosdelJunco
  • CarlosdelJunco's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 62
  • Thank you received: 4
I hit send too soon. 

Should I be concerned that my reading show a huge dip at 80Hz  even at 1/6 smoothing (where I want to put the Crossover at eventually)?

To be clear my SHD minidsp settings have all PEQ and Xover off. Doing sweeps from 20 to 300Hz

Please Log in or Create an account to join the conversation.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 1 week ago #59213

  • Ultrasonic
  • Ultrasonic's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
  • Posts: 2280
  • Thank you received: 463

Should I be concerned that my reading show a huge dip at 80Hz  even at 1/6 smoothing (where I want to put the Crossover at eventually)?

Concerned in the sense of it potentially influencing what you do, yes. You want to be making measurements of each speaker and your subwoofer separately and assessing things from there. Placement of your subwoofer, main speakers and listening position will all affect what the measured responses are, so consideration of moving these to improve things should be step one. Noting that the main speaker positions also obviously affect the sound higher up the frequency range so don't only consider bass performance for these.

I use a 48 dB/octave LR crossover at 110 Hz to my subwoofer in large part due to a dip in the response for my main speakers around the 80-90 Hz region that I don't have with my sub where it is positioned.
The following user(s) said Thank You: CarlosdelJunco

Please Log in or Create an account to join the conversation.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 1 week ago #59219

  • CarlosdelJunco
  • CarlosdelJunco's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 62
  • Thank you received: 4
thanks Ultrasonic,

Makes sense what you say regarding raising the crossover. In this case I may also bite the bullet and invest in a second sub to help overall and with the added bonus to get true stereo in the low end!

What about the acoustic timing reference issue I'd pointed out earlier on the measurements panel of REW when measuring my sub? If I do select it (and leave alone "Timing offset" and "Ref level trim" in the next two boxes below?), I get a message on the progress bar when  doing a sweep (even though the sweep has audibly finished) saying "waiting for timing reference". And then it does not generate a graph. Do i need to adjust the "Timing offset" and/or Ref level trim" first to a certain value for it to generate a graph? 

It seems everyone has a slightly different method of doing things on Youtube. The miniDSP website's "how to" Application pages seem only to give the absolute bare minimum of information on specifics of doing measurements. I've been reading "Getting Started  with REW: A Step by Step Guide Rev 6.2, June 23, 2021" which is helping explain things without being totally overwhelming that the regular REW online Help manual can be for a novice.

It's so frustrating that I'm not able to share URL links in this forum as I get flagged as "spam" and the post won't take. I've brought this up with miniDSP tech support and they simply say not to post links. But everyone else is able to do so!  Grrrrr....  
Attachments:

Please Log in or Create an account to join the conversation.

Last edit: by CarlosdelJunco. Reason: Posted too many copies of GIF

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 1 week ago #59220

  • entripy
  • entripy's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
  • Posts: 387
  • Thank you received: 130
The minidsp howto seems bare minimum because that's pretty much all you have to do. I never read the REW manual.

They key thing is to have one full range speaker as the acoustic timing reference when measuring each of the speakers. REW will then do its thing, draw graphs which were wierd for subs but come up with very correct time delays. You have to keep changing the SHD plugin routing matrix to ensure sound only comes out of the acoustic timing reference speaker and the speaker under test.

All you need is the time delays for each speaker, the one used for the acoustic timing reference should be close to zero for fairly obvious reasons. The full range speaker you didn't use for the acoustic timing reference should also be close to zero assuming a central mic position. A sub behind the main speakers will then have a positive delay relative to the main speakers. That means you need to enter this delay difference amount into the SHD Plugin channels for the main speakers to time align them with the sub. So if your sub is delayed 1.7ms relative to your main speakers delay your main speaker channels by 1.7ms. All you need is that one number.

It gets a little more complcated with a second sub behind the listening position of course.
 
The following user(s) said Thank You: CarlosdelJunco

Please Log in or Create an account to join the conversation.

Last edit: by entripy. Reason: fix typo

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 1 week ago #59221

  • CarlosdelJunco
  • CarlosdelJunco's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 62
  • Thank you received: 4
Thanks Entripy,

I do like to understand how things work, so actually don't mind reading key parts of the manual.

From my reading so far, regarding using the acoustic timing reference, and starting with my left speaker as the timing reference I only do one sweep for each speaker yes to correctly time align? From the manual I've just been reading with my highlights.

Also, to be totally clear, as a first step, all I'm trying to do is get optimal time aligned communication between left, right speakers and the sub - BEFORE using Dirac Live measurements, yes?

I.E. I don't want to be using Auto EQ feature in REW to help flatten sub response before using Dirac Live...or I do want to be using Auto EQ before using  Dirac Live?

And, I am also guessing I could do everything (and more with REW) but that Dirac Live simplifies things?

 I've also read a good article that "phase alignment" with subs (using impulse response) is questionable at best since the wave lengths are so long in the extreme low. Totally fascinating read. I've highlighted the key takeaways. (SEE ATTACHED SCREENSHOTS AND PDF)


 
Attachments:

Please Log in or Create an account to join the conversation.

Last edit: by CarlosdelJunco.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 1 week ago #59223

  • entripy
  • entripy's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
  • Posts: 387
  • Thank you received: 130
Yes, you need to do time alignment, set Xovers etc. before Dirac Live. Dirac Live should be the very last thing done.

And yes, one sweep for each speaker is all that's needed.

Dirac Live doesn't just simplify things, it has far better algorithms.

Whilst its true that the bass wavelengths can be very long and a few milliseconds of time aligment error shouldn't affect phase much unfortunately in practice it sounds awful if you don't integrate subs and mains accurately. You also can't measure the distance between the subs and mains and calculate the time difference using the speed of sound because the effective acoustic centre of the sub may be somewhere surprising. I tried guessing the delay and calculating it but didn't get an acceptable result until I used REW to actually measure it so all this complex setup stuff is most definitely worthwhile.
The following user(s) said Thank You: Ultrasonic, CarlosdelJunco

Please Log in or Create an account to join the conversation.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 1 week ago #59224

  • CarlosdelJunco
  • CarlosdelJunco's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 62
  • Thank you received: 4
Entripy (and Ultrasonic) firstly thanks so much for your generous input for us newbies! I've become completely obsessed in understanding how thing s work "under the hood"!

That said, i also tend to over complicate things. I'd added one edit to my last post, and I think Entripy you had already responded (again, thank you!), you had already responded. Here it is again:

In getting things properly aligned between mains and sub first do I also wanting to be using Auto EQ feature in REW to help flatten sub response before using Dirac Live?

Please Log in or Create an account to join the conversation.

Last edit: by CarlosdelJunco.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 1 week ago #59226

  • entripy
  • entripy's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
  • Posts: 387
  • Thank you received: 130
No don't use REW Auto-EQ. Dirac Live will do it much better once the speakers are all time-aligned.
The following user(s) said Thank You: CarlosdelJunco

Please Log in or Create an account to join the conversation.

Time alignment method for sub integration for stereo speakers with SHD and REW? 9 months 1 week ago #59230

  • CarlosdelJunco
  • CarlosdelJunco's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 62
  • Thank you received: 4
Thanks again entripy,

My measurements with Left speaker timing reference:

L =        .0045 ms (which i know is essentially "0")
R =      -.1068 ms
Sub =  1.641ms

Does this look right? (see photo attachment of SHD minidsp plugin) Ie, should I just ignore the small difference of the Right speaker's negative value "-.1068 ms" or adjust values somewhat? Because of my room set up, the right speaker is a few cms farther forward from the back wall for better stereo imaging and balance.

 
Attachments:

Please Log in or Create an account to join the conversation.

Moderators: devteam