Time Alignment Tool Question

[Shimei]

Hi,
In my 2.2 channel system my mains are high passed at 15hz. They are full range - Tekton Ulfberhts.
And the subs are bandpassed. Highpass 15hz and lowpass 120hz - Tekton 4-10s.

Can I even use the Alignment tool w/ no timing reference? I currently use a USB from my laptop into an SMSL M400 and then the analog L and R signals are inputted into a Minidsp 2x4hd where the two channel input signal is output to 4 channels > LR and two subwoofers.

If not then I guess my question has been answered. If so, then my question is when using the time alignment tool to integrate the summed mains to summed subwoofers what should I set the cursor at?
Right now I'm trying 100hz and little confused. After inputting the delay into my Minidsp 2x4hd and rerun the time alignment tool it then kicks another delay. Shouldn't it verify or confirm a zero delay?

I'm not understanding why such a big delay for the subwoofers is being recommended when my subs are near so close to the mains. Here's a picture of the system. There's one 4-10 outside of each main:

 

[Shimei]

I'll take new measurements tomorrow. Figured out how to use the timing reference in my 2.2 channel system using USB. I can utilize the "routing" tab in the Minidsp 2x4hd to use the L speaker for the reference and R channel for the other 3 speakers one at a time.

 

[sm52]

Can I even use the Alignment tool w/ no timing reference?

If you want to match the subwoofers with each other and with the main speakers, a timing reference is needed. Read the thread https://www.avnirvana.com/threads/n...-understands-a-tittle-german.8730/#post-66869

 

[Shimei]

If you want to match the subwoofers with each other and with the main speakers, a timing reference is needed. Read the thread https://www.avnirvana.com/threads/n...-understands-a-tittle-german.8730/#post-66869

Appreciate your help. This morning I used a timing reference. Here's final setup. I used a Harman house curve on the mains but decided not to use house or filters on the subs. I had replaced the stock softdome high frequency tweeter in the Tektons with Be tweeters and they obviously needed taming down. The slope as is my guess is probably the SMSL M400's filter which can't be turned off. The subs had to be gained down -8db at this point but the system pegs my DB meter at 130spl.

 

[jtalden]

These measurements will not work for determining the XO delay timing of the setup. We must use REW acoustic timing instead of loopback timing when using a UMIK-1 mic. A chirp will be heard from the tweeter of the reference speaker just prior to the full sweep from the measurement speaker.

I suggest these 6 new measurements for this situation.

Setup

• Mic position at LP (centered between left and right speakers)
• Leave your current preferred EQ and level settings active. [Changes can still be made later and it will not effect this delay timing.]
• Set all the MiniDSP delays to 0 ms.
• REW measurement range 20-22k Hz for all 6 measurements (don't limit subs to 300 Hz)
• Select REW acoustic timing
• Set REW reference channel to left.

Measure

1. Right speaker (alone)
2. Right Sub (alone)
3. Right Channel (speaker and sub together)

• Now set REW reference channel to right.

1. Left speaker (alone)
2. Left Sub (alone)
3. Left Channel (speaker and sub together)

These 6 measurements will allow the correct delay timing to be determined for all 4 speakers.

 

[Shimei]

These measurements will not work for determining the XO delay timing of the setup. We must use REW acoustic timing instead of loopback timing when using a UMIK-1 mic. A chirp will be heard from the tweeter of the reference speaker just prior to the full sweep from the measurement speaker.

I suggest these 6 new measurements for this situation.

Setup

• Mic position at LP (centered between left and right speakers)
• Leave your current preferred EQ and level settings active. [Changes can still be made later and it will not effect this delay timing.]
• Set all the MiniDSP delays to 0 ms.
• REW measurement range 20-22k Hz for all 6 measurements (don't limit subs to 300 Hz)
• Select REW acoustic timing
• Set REW reference channel to left.

Measure

1. Right speaker (alone)
2. Right Sub (alone)
3. Right Channel (speaker and sub together)

• Now set REW reference channel to right.

1. Left speaker (alone)
2. Left Sub (alone)
3. Left Channel (speaker and sub together)

These 6 measurements will allow the correct delay timing to be determined for all 4 speakers.

I really appreciate the help. I heard the chirp before each test. Here are the results, 6 measurements and no filters at this time.
My mains are high passed 15 hz and above.
Subs are bandpassed, high passed 15 hz and low passed 120 hz.
What is the recommended cursor placement in the alignment tool?
Anymore further assistance is much appreciated! I'm totally confused by the recommended positive or negative delays

 

[jtalden]

I really appreciate the help. I heard the chirp before each test. Here are the results, 6 measurements and no filters at this time.

Does this mean you are intending to to apply XO filters? I was assuming you intended to only use these current settings thus allowing the mains and subs to both cover the low bass.
If you intend to add a XO from subs to mains then it is necessary to apply it when taking the measurements. An XO filter changes the delay timing needed. I am not advocating for any particular choice. I just need to understand your intensions for the analysis.

Also -

• Are you intending to run mono or stereo with the SWs?
• This attached REW file will not download for me. The first 2 were fine.

 

[Shimei]

Yes, the crossovers were active in the measurements. And yes, both mains and subs cover low bass. The mains in the output tabs of the minidsp are 15 hz highpass 24db slope. The subwoofers are 15 hz highpass 24db slope and 120 hz lowpass 24 db slope.
Intending mono subwoofers. Each L and R channel in the input routing tab send a signal to both subwoofers.
Lemme try uploading again:

 

[Shimei]

And just curious,
I see in each measurement the ability to click "info" and the system delay information which is different for each measurement. Just curious if these delays could be inputted for L and R as well as LS and RS? I mean, with the positive and negative delays I haven't a clue whether each delay could be entered into the minidsp for the speaker measured.

 

[jtalden]

Yes, the crossovers were active in the measurements. And yes, both mains and subs cover low bass. The mains in the output tabs of the minidsp are 15 hz highpass 24db slope. The subwoofers are 15 hz highpass 24db slope and 120 hz lowpass 24 db slope.
Intending mono subwoofers. Each L and R channel in the input routing tab send a signal to both subwoofers.
Lemme try uploading again:

Thank for the clarification. The measurements look good. This data is just what is needed. [I just tried the previous post-6 file again and it also now downloads for me.]

And just curious,
I see in each measurement the ability to click "info" and the system delay information which is different for each measurement. Just curious if these delays could be inputted for L and R as well as LS and RS? I mean, with the positive and negative delays I haven't a clue whether each delay could be entered into the minidsp for the speaker measured.

I use the REW Alignment Tool (AT) for the analysis. It does not use the REW system delays that are reported. There are numerous other ways to determine the delays needed that also find favorable delay settings. I have tried a couple of them, but find the REW AT method more reliable. It better helps understanding what changes or tradeoffs are more favorable in difficult room setups.

Step 1 is set the delay timing favorably for the 2 SWs.
Step 2 is set the delay timing favorably for the XO handoff.

There are numerous REW operations involved particularly in Step 2 of the process. The operations can change depending on the system and the measurements so a simple step by step process is difficult to provide. I suggest this thread to get some idea of the process.

I will thus do the analysis, report my findings and then answer any questions you may have.

 

[Shimei]

I will thus do the analysis, report my findings and then answer any questions you may have.

Just for orientation purposes when looking at the front sound stage from the main listening position the L is the left side. Don't know if it matters but to help w/ visual understanding of the measurements. Of course the Left side from the MLP looking at the front sound stage there's a corner which obviously has boosted low end bass response.

There are numerous REW operations involved particularly in Step 2 of the process. The operations can change depending on the system and the measurements so a simple step by step process is difficult to provide. I suggest this thread to get some idea of the process.

Looking forward to your results. I think the best way for me to learn REW and the proper way of aligning things is to use the exact same measurements and try to replicate your results.

Lastly, while looking at the frequency response of the overall system if I may ask you for your recommendation of house curve? Since the measurements were taken I applied a 10db+ house curve from Harman Research to the mains. The only way I could compensate for the Right side main's dip in low response was to lower the target curve so low that there's a dramatic reduction in overall spl. However, both mains and subs follow the 10+db house curve most closely. I'll put this configuration in slot 1 in the Minidsp. And I'm thinking to utilize slot 2 in the Minidsp for maximum spl.

I have read the thread you recommended. Though I'm reading it the "trace arithmetic" is a foreign language to me at the moment.

I very much appreciate your time and help @jtalden. Without peeps such as yourself this hobby might be much more frustrating.

Thank you,
Shim

 

[jtalden]

Step 1 - SWs delay timing and gain change:

The LS delay timing was increased by 2.5 ms from the current setting. This setting results in about a 3.4 ms total offset timing of the 2 SWs. This small offset results in a smoother SPL that is better shaped to compliment the RM and LM in step 2. The gain of both SWs was also reduced by 8 dB. The the black sum trace in the first chart thus is shown at -8 dB compared to the 2 measured SWs in green. This gain reduction was done to better match to the RM and LM levels for the step 2 analysis. Any further SW gains adjustments made to adjust the bass level to your preferred level can be made so long as the same change is made to each individual SW. Any change to the relative gains of the 2 SWs or to this 2.5 ms increase in delay of the LS will significantly impact the frequency response throughout the bass range. EQ can of course be applied to address the SPL shape without causing any problems.

Step 2 results to follow.

 

[jtalden]

Step 2 - XO delay timing:
The delay timing change for the XO is to increase the delay on the RM and LM by 15 ms.

The chart below shows the resulting SPL of the right channel vs left channel. The bass range is still very high even with the 8 dB reduction applied to the SWs. A further reduction to their gain is probably needed. Adjust that gain level again as needed in order to prepare for EQ to your preferred house curve.

Analysis Process Steps
The RM, LM average (blue) was created using REW trace arithmetic.

Create the mono response of the system, i.e., the summation the average of the RM and LM with the Sum of the 2 SWs.

Create the right channel response by summing the RM with the SWs.

Create the left channel response by summing the RM with the SWs.

Summary of the recommended changes:

• Both SW gain reduced by at least 8 dB.
• Delay the left SW by and additional 2.5 ms
• Increase the delay of the right and left mains by 15 ms.

 

[Shimei]

@jtalden Thank you so very very much!!!

I used the +10 Harman Research house curve for LR and SL as well as SR on the Minidsp's output channels. There was a big dip 4000hz to 20000hz when the entire system was measured. I then created a filter from 4000hz to 20000hz and put the filter in the input channels of the Minidsp.

I can't believe how much effort and help you have contributed. Much thanks!!!