Regarding multi-sub alignment, sub to main alignment and EQ set up

[Niklasmagnus]

Hi,
Just want to get a few things clear regarding multi-sub alignment, sub to main alignment and EQ set up.

I been using REW a few time and know the software I believe quite good, but don’t always know how to set up measurements or how to do the analyses. Just did some playing around a few hours since I added the fourth sub (middle right in series with middle left) with 1 point (MLP) measuring to set the subs alignment and test eq. I have added the mdat file for the session, “Measures.zip”. I run 2 subs in series per channel, total 4 subs.
I have tried and delay of middle subs compared to the corner subs by checking SPL sum over the bass area, and 2,4 ms delay looked best in my opinion. But this I still only measured from one point, MLP. Mdat: “mic 77cm Set delay 4 subs minidasp.mdat”.
Also tested different XO, and I think 150Hz looks best.
Added near filed measurement from each sub and reference: “SUB 3 cm.mdat”

Question 1
Correct to do multi-sub alignment from one measuring point, MLP? Or must I take multiple around MLP or even around my 3 seat sofa, and average. but how step by step?
If okey from one point, what do you think about the result of chanel 2 delayed 2,4 ms?

Question 2
Correct to do main Right (or left) – subs alignment from one measuring point, MLP? Or must I take multiple around MLP or even around my 3 sit sofa, and average, but how step by step?
If okey from one point, what do you think about the result of subs delayed 3.12m to main (R at 3,45m in AVR)? Measurement “Sub1-4XO150 2,4//3,95*” in “Measures.mdat”.

Question 3
What is minimum measuring points for EQ the sub? And since I´m using Marantz SR7009 I can do some eq on LCR also but then I need FDW cycles to get correct results? How many cycles? This feature is new to me.

Thanks
Niklas

 

[jtalden]

You did well!
The 150 Hz XO looks fine and is better than 250 Hz. Most try to stay below 100 Hz. It very much depends on the equipment, room and setup though.
Mic only at MLP usually works about the same as using multiple positions for timing the SWs to Mains handoff.

• Measurement 14, "L+Ss*XO150 2,4/3,95" Left, channel looks good for SPL support and delay timing.
• Measurement 15, "R+Ss*XO150 2,4/3,95" Right channel looks good for SPL support and delay timing.
• Measurement 16, "R&L+Ss*XO150 2,4/3,95" Both channels looks good for SPL support and delay timing.

Measurement 19, "R+SsXO150 2,4/3,12" is okay and looks good for SPL support, but not for delay timing. There may, or may not, be a sound quality difference with it. I would favor the above timings unless you prefer the sound quality of this one.

Regarding EQ, it is better to average several mic positions in the listening area in my opinion. A tight pattern can be used for a MLP focused setup. A broader pattern is better if several seats are given priority. I suggest at least 5 positions for EQ. A moving mic method is my first choice, but it takes time to learn how to set it up and do it properly. A simple average of 5 - 9 positions is much easier if the object is to get the job done and get up and running. I don't use FDW for EQ work when using average measurements in the listening area. FDW has more value during the delay timing work.

 

[Niklasmagnus]

Thanks for the input. Don´t know if you notice that the measurements with "*" in the naming, the subs are inverted compared to the main channels. Any feedback regarding that?

Will test some more with your recommendation.

 

[jtalden]

Yes, I noticed the inverted SW trials. I tend to look for close phase tracking of the direct sound from SWs and mains throughout the XO range as the preferred target. This is the popular target for most XO timing work. Since the acoustic filters shapes do not closely follow the electrical XO filter settings, it is best to just choose the SW polarity that provides the closest phase tracking rather than choosing a commonly recommended polarity for the electrical XO filter chosen. That is what you found and I recommended above.

I do think the SPL support is the more important issue for bass range XOs. It is not clear that the direct sound phase tracking is always the best case due to strong room effects at the MLP. One can often find other delay settings have similar SPL support through that range using the opposite SW polarity. Choose the setting that sounds best to you. Try to stay reasonably close to the timing of the direct sound tracking target however. A shallow phase crossing situation in the XO range is not normally a problem.

This was a lot of data to work through and try to make sense of. It is not in the form I normally use that thus it was time consuming to understand. I was fortunate that I was able to pull out enough info to support my normal analysis method. Repeating this for these choices of XO and room positioning will only result in the same recommendation. You were able to use the new REW alignment tool to find a couple of good delay settings so it is likely that you can do that again yourself. If you do have another XO frequency and/or room positioning setup that you want me to look at, I can do one more analysis if you provide only the specific measurements that I would specify.

 

[Niklasmagnus]

Thanks so much for all the help. I understand it takes time to do analyses, and extra long time when I haven´t measured according to you method/ standard. As I have all 4 subs on front wall now I will test a few more things according to your input. and also check what the seat to seat bass response looks like, but if I cant get good result I need to test moving two subs to back corner. So I was wondering if you have posted the normal method you are using for which measurement to run and how to work step by step with the analyse?

BR// Niklas

 

[jtalden]

Once a new setup is finalized impacting a mic, SW, or mains position change and/or a crossover setting change, I will do another analysis. You can then use my recommendations to confirm your own findings of a favorable delay timing for that setup. Any change to the 4 SW positions requires the SW delays to be adjusted accordingly just as you did before. The delay of the SW group to the main speakers is then ready to be determined. There are 3 needed measurements.

Measurement Setup:

• AVR XO active
• Full range sweeps
• REW acoustic timing activated
• Mic at MLP

Measurements:

1. L (alone - no SWs)
2. R (alone - no SWs)
3. SWs (all 4 together) [Measure this using the L channel with the left main speaker disabled thus the redirected bass is measured]

Be sure you know or record all the AVR/MiniDSP distance/delay settings used for these measurements. My recommendations will be adjustments from those settings. You can leave any SW or mains EQ active if you have made those settings.

I will provide 1 or 2 delay recommendations, resulting charts and answer any questions you have.

 

[Niklasmagnus]

Jtalden,
Regarding placing one sub at each corner and using high (150hz) XO for the front sub. Is it possible to add a Lowpass on the back subs so they don’t get locatable and still get good phase integration?

 

[jtalden]

I can't predict what might be possible as I have only addressed SW setups using a narrow methodology. My experience is with SWs set mono rather than L, R. First the delay timing between the SWs is set such that sound from each SW arrives at the LP at the same time. The delay timing to mains can be done before, after, or during the EQ determination. There are simpler and more sophisticated methods that others use with good results so there is nothing magic about my approach.

I would not expect that well behaved SWs that are distributed front-to-back, side-to-side or any combination in the room would be localizable even with a 150 Hz XO. Any abnormal port chuffing, or leakage of higher frequencies is likely to be problem however. I have never tried XOs this high, but would not be afraid to do so if there is a good reason.

When all SWs are not the same, or setup to cover different bandwidth as you proposed, it is difficult to predict the result. The phase response will be very different so the issue is whether the 2 sets of subs will interfere in a way that causes a problem. There is no problem if the 4 can be blended together favorably.

 

[Niklasmagnus]

Hi Jtalden,

I have moved two subs to the back corners, one sub per corner now, instead of 4 in the front, but I´m struggling to get god time alignment. Might be so I need more delay for the rear subs then my minidsp 2x4 bal, 7.5 ms can handle. Can you find a way to get them aligned?

To took the next step with rear subs maximum delayed, 7,5ms, and start playing around with XO, but I cannot find any good combination using the time alignment tool.

 

[jtalden]

I reviewed the data. As you indicated with the current room setup it would require more delay for the rear SWs to time align closely with the front SWs. I found that another 11 ms would be needed to do that. That said, the current setting has SPL no nulls below the one at 126 Hz and probably can be EQed to a smooth result. From the SPL standpoint, the current alignment is as favorable as one that has better time alignment.

I also found, as you did, that this SW setup did not blend particularly well with the mains at any of the XO frequencies. The 60Hz XO looked to have the best prospects. My sense is that you are able to use the alignment tool to investigate the possibilities. If you do want me to confirm the specific timing I would chose for 1 or 2 of the XO possibilities, I can do that. If you don't like one of the possible alignments with this setup, the option is to change the room setup; move the LP forward, find SW or mains locations that work better together.

A MiniDSP or other box that allows aligning the SWs delay may well result a shift in the phase rotation of the combined SWs. This may, or may not, improve the phase tracking to the mains. I wouldn't expect this to be an easy solution to the situation however.

 

[Niklasmagnus]

Sorry but I don´t understand your analyze. I guess you mean 18.5 ms inverted to get positive summation up to ~108 Hz?
But you write that with 7,5 ms there is no nulls under 126 Hz, but the SPL drop at 110Hz is not that a null?

You mean that the 7.5 ms are better then 18.5 ms due to more same timing on the IR?

Is have seen you used FDW a few times in other post, but I don´t fully understand that yet. Is it something I need to apply with the alignment work?

7,5 ms


18.5ms


18.5 ms inverted


EDIT: To get the 18.5 ms delay I need to buy the 2x4 HD version. Would you say its a good idea?

 

[jtalden]

Sorry but I don´t understand your analyze.

The confusion is probably mine. I am juggling too much right now.

I guess you mean 18.5 ms inverted to get positive summation up to ~108 Hz?

I understood that the current delay on measurement 4 was already the maximum 7.5 ms the above changes are in addition to this. I used measurement 7 and 4 in the alignment tool and found it would take roughly 11 ms additional delay (18.5 ms total) on measurement 4 to reach one favorable SPL alignment. That was most favorable alignment I found and represented the maximum delay that we would consider using. There were others found that about as good with less delay, but still required more delay more than the current 7.5 ms limit.

I just now found another favorable alignment reducing the delay on measurement 4 by 6 ms (1.5 ms total delay).

But you write that with 7,5 ms there is no nulls under 126 Hz, but the SPL drop at 110Hz is not that a null?

I looked at measurement 1 in "Corner subs and 4 front subs.mdat" and took that to be the current timing of the 4 subs. I did not know what that timing was however. It is different from what would result from combining Measurement 4 and 7 so what does that measurement represent?

You mean that the 7.5 ms are better then 18.5 ms due to more same timing on the IR?

??, with the current 7.5 limit that is represented in measurement 4 vs 7, we either use the most favorable timing within that limit or another box is needed with this setup. I think I pointing out that we can go either way.

Is have seen you used FDW a few times in other post, but I don´t fully understand that yet. Is it something I need to apply with the alignment work?

I haven't been using FDW on your data as aligning the direct sound timing results is poor SPL because the room modes are very active with this setup. We are better off finding an alignment using no FDW.

EDIT: To get the 18.5 ms delay I need to buy the 2x4 HD version. Would you say its a good idea?

Since we now identified a timing that will work favorably for SPL on the SWs we may as well just use that one.

If you agree to move forward using the 1.5 ms delay on the rear SWs please measure the 4 SWs individually and all together with that setting. If it confirms what we expect, we can then do the measurements in Post-6 using the 60 Hz XO. That is the one that shows the most likelihood of success.

 

[jtalden]

Below is the SPL chart. Measurement 10 is ~18.5 ms delay and measurement 13 is the 1.5 ms delay differential.

 

[Niklasmagnus]

The confusion is probably mine. I am juggling too much right now.



I understood that the current delay on measurement 4 was already the maximum 7.5 ms the above changes are in addition to this. I used measurement 7 and 4 in the alignment tool and found it would take roughly 11 ms additional delay (18.5 ms total) on measurement 4 to reach one favorable SPL alignment. That was most favorable alignment I found and represented the maximum delay that we would consider using. There were others found that about as good with less delay, but still required more delay more than the current 7.5 ms limit.

I just now found another favorable alignment reducing the delay on measurement 4 by 6 ms (1.5 ms total delay).

Sorry, I was not clear about the measurement. In file:
1. are the old subwoofer setup with all 4 sub in front of the room. Just as a reference for comparison.
2. individual sub Rear Left, no delay
3. individual sub Rear Right, no delay
4. Sub group Rear Left and Right, no delay
5. individual sub Front Right no delay
6. individual sub Front Left, no delay
7. Sub group Fornt Right and Left, no delay

So there are no initial delay, 7,5 ms, on any of the measurements 2-7. Meaning the added/ reduced values you found are from 0.

I looked at measurement 1 in "Corner subs and 4 front subs.mdat" and took that to be the current timing of the 4 subs. I did not know what that timing was however. It is different from what would result from combining Measurement 4 and 7 so what does that measurement represent?

Number 1 are the old subwoofer setup with all 4 sub in front of the room. Just as a reference for comparison.
The one from the first post in this thread. Sorry for the confusion.

??, with the current 7.5 limit that is represented in measurement 4 vs 7, we either use the most favorable timing within that limit or another box is needed with this setup. I think I pointing out that we can go either way.




I haven't been using FDW on your data as aligning the direct sound timing results is poor SPL because the room modes are very active with this setup. We are better off finding an alignment using no FDW.



Since we now identified a timing that will work favorably for SPL on the SWs we may as well just use that one.

If you agree to move forward using the 1.5 ms delay on the rear SWs please measure the 4 SWs individually and all together with that setting. If it confirms what we expect, we can then do the measurements in Post-6 using the 60 Hz XO. That is the one that shows the most likelihood of success.

So with the box I have today my only option is to test the -6ms on rear sub group. But looking at the Aligned sum it is reduced in SPL output compared to "Sub RL+R XO250" and "Sub FL+R XO250" in the region <40 hz and around 80 hz. Would you say it acceptable? I would love to get a boost in the lower with a few db.


Before I order a new minidsp I will try this and also try with the old setup, 4 subs in front of room, and check the seat to seat response.
I found a video on youtube showing the MMM (moving mic measuring) and will try it so get fast and bigger volume result.
Link: moving mic measuring

Below is the SPL chart. Measurement 10 is ~18.5 ms delay and measurement 13 is the 1.5 ms delay differential.
View attachment 28739

I have added your aligned sums with the setup I was running with 4 subs in front (measurements, no simulation).
Which is best in your opinion?

 

[jtalden]

So with the box I have today my only option is to test the -6ms on rear sub group. But looking at the Aligned sum it is reduced in SPL output compared to "Sub RL+R XO250" and "Sub FL+R XO250" in the region <40 hz and around 80 hz. Would you say it acceptable? I would love to get a boost in the lower with a few db.

Before I order a new minidsp I will try this and also try with the old setup, 4 subs in front of room, and check the seat to seat response.

The 4 subs up front look to be the better option.

I found a video on youtube showing the MMM (moving mic measuring) and will try it so get fast and bigger volume result.
Link: moving mic measuring

https://www.youtube.com/watch?v=6RiuwqzjqlQ

Great video! This is the method I use. I find this method to work best for EQ for all the reasons they listed. Be sure to use the correct settings in REW RTA controls. We don't need 2 people as we don't need to be moving the mic before starting the measurement. Any static when touching the mic will boost the low bass with my XLR mic.

I have added your aligned sums with the setup I was running with 4 subs in front (measurements, no simulation).
Which is best in your opinion?

I would need the measurements detailed in post-6 to make any comments on SW to mains timing.

 

[Niklasmagnus]

I would need the measurements detailed in post-6 to make any comments on SW to mains timing.

Sure will take new measurements, when done with the four corners. They are not so easy to move, 12" in ~100L box.

I was also taking new measurements on the set up with subs in all the four corners and with different crossover. I didn't know that the phase response will be change when changing the XO in AVR, so cannot make conclusion on just the 250 crossover. I still need to measure the L/R at the different XO before its possible to make something out of it. But the new Phase alignment for specific frequency feature that was added in last beta is great, will give a got start point in timing for the overall. Great =)
(I hope we can get a alignment button for maximum SPL for a frequency interval in future)

 

[jtalden]

I have never seen anyone suggesting a 250 Hz XO for a SW is a good idea. The standard XO is 80 Hz and 80±20 Hz is not an issue. It would be a very unusual situation where a setting greater than 120 Hz would be advantageous.
The REW alignment tool can be used to time the delays for a group of SWs and then also to time align the SW group to the FL, FR mains. For those wanting to try various SW group setup options and then various XO options, it is worth it to spend the time to learn how to use the alignment tool. It is working very well. It's best to practice on an easy case. It can get confusing learning how to read the ones that have a lot of room disturbance in the XO range. Post-6 lists the measurements needed to time the delay of the SWs to the mains. The XO must be active for good accuracy. I suggest using REW to average left and right mains using REW trace arithmetic (A + B) / 2. and use that in the top position of the tool. The SWs go in the lower position and are the ones that are adjusted to phase match in the XO range. The cursor must be placed near the center of the XO range as the calculation uses that frequency reference.
Note that, we are looking for favorable SPL support through the XO range. If we achieve that then EQ will be effective and thus timing alignments with small SPL differences (2-3 dB for example) are not any concern. We mostly just want avoid large dips. Avoiding a large dip in one (or even both channels) is not possible in some setups however.

 

[Niklasmagnus]

Hi, so after struggling a bit with the alignment tool do think i start to get a good feeling about it. But still, i´m not 100%. Would be great to compare my finding with yours.
Since I have two subwoofer groups: 2 pcs in front corners (one group) and 2 pcs in the rear corners (one group) I have remeasured the response with different XO (60, 80, 90, 100) but also added the measurement of the main LR for same XO.
My Minidsp can maximum add 7,5 ms in delay between the sub groups.
When I have tested the alignment tool I think +7,5 ms on the rear subs will do the best job for XO60-90. Cannot find any good setting for XO100.
Could you give it a new try and also if possible to integrate the mains. I have already time align the LR and also created and new sum, (A + B) / 2.

Naming in files (had to slip in two due to file size):
Sub RL+R = are the rear group
Sub FL+R = are the front group
L = main L
R = main R


If we can find the best settings I can check the seat to seat and try to apply some EQ. Depending to end result I will do same measurement with all subs on front wall under the mains. And maybe I can found a better setup for MLP and also seat to seat.

(Regarding the XO250. This was a misunderstanding . I though that if I just measure the subs with XO250 I will cover all other XO also, I did not know that when changing the XO the phase response will also change. So no one have suggested to use XO250.)

 

[jtalden]

Did something change in the setup? I already analyzed the 2 front/2 rear sub positions and suggest a delay of 1.5 ms for the rear SWs.

If you agree to move forward using the 1.5 ms delay on the rear SWs please measure the 4 SWs individually and all together with that setting. If it confirms what we expect, we can then do the measurements in Post-6 using the 60 Hz XO. That is the one that shows the most likelihood of success.

Step 1: Create a SWgroup that works well together
Maybe I wasn't clear that once the SWgroup timing is decided and confirmed then it is treated as group, i.e., like a single sub. For this step the SWs could be measured using the LFE channel. It could optionally be measured using the FL (or FR) channel with the XO set to a higher value than you expect to actually use. Any setting >120 Hz is a good choice. Your measurements using 250 Hz were appropriate.

Before moving on to SWs vs mains timing it is wise to measure using the targeted 1.5 ms on the rear SWs to confirm there is no error in my recommendation, or in your settings, hence the quote above.

If instead you wanted a second option for timing of the SW, that is now possible as we have 6 ms of unused delay to investigate. You can use the alignment tool for this, or I can find another timing option using this data. The SPL support difference between favorable alignments is usually small so any nulls or sags are not likely to be removed.

Status: Confirming measurements needed, or direction to find another optional SWgroup alignment using this data.​

Step 2: Determine a favorable delay timing between the SWgroup and the mains
Step 1 must be completed first.
For SWs to mains timing then only 3 measurements are needed for each XO setting being considered (see Post-6).

Status: Pending completion of Step 1​

Note:
I will do a maximum of 2 more Step 1 analyses, and a maximum of 4 more Step 2 analyses. So if you want my input on the front setup again plan your requests accordingly.

 

[FargateOne]

Great video! This is the method I use. I find this method to work best for EQ for all the reasons they listed. Be sure to use the correct settings in REW RTA controls. We don't need 2 people as we don't need to be moving the mic before starting the measurement. Any static when touching the mic will boost the low bass with my XLR mic.

Hi,
may I interupt your interesting discussion with a technical question about the best method to do that (or should I begin a new thread?). Watching the video it seems to the amateur in me that the mic movements are too fast. I follwe the following method:

Room correction with REW using PEQ

Measure speaker response

Set RTA > Averages > forever


Hold the mic at the main listening position at ear height with the tip pointing either up or down. Click "Reset averaging" and start moving the mic slowly through the listening area at a speed not faster than about 10cm (4 inches) per second. Try to cover as many different points as possible within the listening area. The area should cover a volume of about 60cm (2ft) or wider around the main listening position to avoid over-optimization by EQ later on. After about 60 averages click save.

 

[jtalden]

If you start an MMM discussion thread then others will be able to find it. I will comment there.

 

[Niklasmagnus]

If you agree to move forward using the 1.5 ms delay on the rear SWs please measure the 4 SWs individually and all together with that setting. If it confirms what we expect, we can then do the measurements in Post-6 using the 60 Hz XO. That is the one that shows the most likelihood of success.

Did something change in the setup? I already analyzed the 2 front/2 rear sub positions and suggest a delay of 1.5 ms for the rear SWs.







Step 1: Create a SWgroup that works well together

Maybe I wasn't clear that once the SWgroup timing is decided and confirmed then it is treated as group, i.e., like a single sub. For this step the SWs could be measured using the LFE channel. It could optionally be measured using the FL (or FR) channel with the XO set to a higher value than you expect to actually use. Any setting >120 Hz is a good choice. Your measurements using 250 Hz were appropriate.



Before moving on to SWs vs mains timing it is wise to measure using the targeted 1.5 ms on the rear SWs to confirm there is no error in my recommendation, or in your settings, hence the quote above.



If instead you wanted a second option for timing of the SW, that is now possible as we have 6 ms of unused delay to investigate. You can use the alignment tool for this, or I can find another timing option using this data. The SPL support difference between favorable alignments is usually small so any nulls or sags are not likely to be removed.



Status: Confirming measurements needed, or direction to find another optional SWgroup alignment using this data.



Step 2: Determine a favorable delay timing between the SWgroup and the mains

Step 1 must be completed first.

For SWs to mains timing then only 3 measurements are needed for each XO setting being considered (see Post-6).



Status: Pending completion of Step 1



Note:

I will do a maximum of 2 more Step 1 analyses, and a maximum of 4 more Step 2 analyses. So if you want my input on the front setup again plan your requests accordingly.

Hi, no nothing changed. Its only due to my confusion but I have tested to compare a few graphs now I and start to understand. Sorry.
Attached are the measurements (with XO250 and XO60) of 4 SWs individually and all together with with de delay -6 ms on Rear sub group => meaning 6 ms on the front sub group since its not possible to add negative delay in minidsp.
(Your result of 1,5ms delay of rear subs are due to you though that there was an initial delay already in the measurement you received of 7.5ms > 7,5-6= 1,5. But since there was no pre-delay, your finding are -6ms of rear subs or 6 ms delay on the front subs.)


It was not clear if you wanted the measurements for XO250 or XO60 so I have attached them both.

Now all subs are playing at same SPL level individually, since they are gain match. Do you think they should be level match at MLP instead so the rear subs are not adding more SPL in MLP? If so they should be reduced 4,1 db each.

 

[FargateOne]

If you start an MMM discussion thread then others will be able to find it. I will comment there.

OK I'll do. I think it could be interesting

 

[jtalden]

You are correct. The delay of the rear SWs we calculated was indeed 6 ms. That eliminates any other timing options for this SW setup using the current MiniDSP. I'm glad you caught that.
Either set of measurements (80 or 250 Hz XO) will work for Step 1. The 250 Hz is better in this case. That is what we used previously so a direct comparison of calculated vs measured can be made.

The SPL chart below shows the comparison. I have plotted 3 traces. Trace 5 is the your measurement of the SWgroup. Trace 6 is the vector summation of the 4 individual SWs. These 2 traces overlay each other as expected. Trace 7 is the imported 6 ms calculation from Post-13. I differs only slightly and I suspect that is due to minor mic position or other change in the measuring session. Thus all is as expected and we are done with Step 1 for this SWgroup setup.
We can now do Step 2 per Post-6. I recommend an XO at 60, 70 or 80 Hz. It has more chance in helping to mitigate the influence of the dip at 125 Hz will thus have less influence on the overall SPL. You choice can be influenced by how strong the SPL of the mains looks in that region.

 

[Niklasmagnus]

So I have attached measurements according to post #6, but both for 60 and 80 hz. AVR don´t have an crossover at 70. I was looking at the SPL at 125 hz region for the mains with the two XOs but it only differ 1 db in output so no clear choosing due to that, the reason why i attached them both.