Help with understanding the "Alignment Tool" and what to look out for.

[Exponential]

Well, it's in need of EQ to a good house curve. It is difficult to say if this response is worse than average as I have no way to judge that. There are many more bad rooms than good ones.

Your mic calibration is unusual above 5 kHz for most measurement mics. What mic is this and are you orienting the mic so it that matches the calibration orientation?

Thanks for your honesty...

My mic is a UMIK1. It is placed at the MLP with the mic facing upwards.
It's possibly a reflection off the window?

As you can see, it's not an "ideal" scenario for the perfect response but it's a living room before a listening room. My wife is very clear on that...

 

[Exponential]

Pic of my set up, again heavily compromised with a corner loaded right speaker. Again, constraints of the room I'm afraid.
It explains the 40hz hump as the wall/corner is exciting the mode.

Right hand subwoofer just before my right speaker again, a compromise.

Left subwoofer nearfield to couch in second pic.

These pics may explain a few things?

 

[Exponential]

They are sealed and Downfiring subs BTW

 

[Exponential]

Speaker ports that I filled with high density foam and made a rubbish attempt at colouring it black. The marker ran out of ink quite rapidly..

 

[jtalden]

The mic setup is fine then. I was thinking that some of the high frequency SPL responses may not be accurately represented due to the measurement setup, but your setup is fine. The close distance to the rear wall and window are not ideal, but most of us have room situations that we wish we could change.

I still think that if the EQ comes out well the sound quality will be reasonably good. Getting control of the bass response is big factor in this and taming the higher end to get a more reasonable house curve should be a nice improvement.

 

[Exponential]

The mic setup is fine then. I was thinking that some of the high frequency SPL responses may not be accurately represented due to the measurement setup, but your setup is fine. The close distance to the rear wall and window are not ideal, but most of us have room situations that we wish we could change.

I still think that if the EQ comes out well the sound quality will be reasonably good. Getting control of the bass response is big factor in this and taming the higher end to get a more reasonable house curve should be a nice improvement.

In the middle of a clear out at the house at the moment but once that's done, I'll be straight back onto the measurements so you'll have an update very soon my friend.

 

[Exponential]

@jtalden Just a quick thought. Is it possible (or something that is even considered) to have the mains set to a different delay to each other in order to obtain a better frequency response?
For example: I have a nasty dip at 200hz and 500hz with both mains playing together, can I alter the delay between L main and R main to flatten the response out or does it not work like that?

I tried it once a while back and was surprised at how my mains sounded. In some scenario's it sounded much better but in others it sounded almost robotic and unnatural.

I hope you understand what I mean?

 

[jtalden]

No, we want the L and R mains sound to arrive at the LP at the same time. This retains the intended sound stage imaging. changing the L, R timing will shift the image.

 

[Exponential]

No, we want the L and R mains sound to arrive at the LP at the same time. This retains the intended sound stage imaging. changing the L, R timing will shift the image.

Hi.

Ah right. I had a feeling it wasn't as simple as I thought!

Just so we are clear. Due to the negative delay required on the subs, am I right in thinking that this type of delay can only be input into the STR Preamp and not the minidsp due to the fact that the minidsp will not allow a negative value to be input in the delay section.
I am to input the required delay onto my mains to give the same effect. I have set the listener distance on my mains to 5.52 metres with my subs untouched at zero meters.
This is the equivalent of adding a negative delay of -16.000ms to my subs yes?

When I get a chance to do my measurements, am I doing the same 4 measurements you initially requested?

Also, I've had a play around with my two subs to attempt to align them which I think I did correctly but it left me with a huge peak at 40hz (room mode) can this be EQ'd out at all or am I best leaving the subs alone?

Is this how the phase track at the bottom should look? I have absolutely no idea?

 

[jtalden]

Just so we are clear. Due to the negative delay required on the subs, am I right in thinking that this type of delay can only be input into the STR Preamp and not the minidsp due to the fact that the minidsp will not allow a negative value to be input in the delay section.
I am to input the required delay onto my mains to give the same effect. I have set the listener distance on my mains to 5.52 metres with my subs untouched at zero meters.
This is the equivalent of adding a negative delay of -16.000ms to my subs yes?

Yes!

When I get a chance to do my measurements, am I doing the same 4 measurements you initially requested?

That would be best in this case as we can do the same analysis to see the detail and accuracy of the adjustment compared to the calculated prediction we made. It there is disagreement we have the info needed for another adjustment.

If we were confident that we have done the analysis and adjustment correctly we can just measure the L and R channels. We then use REW A + B / 2 to vector average them in REW. If the SPL sum is the same as the calculated prediction it confirms the adjustment was correctly done. We can also overlay the L and R channel measurements to see how different they are. The only issue in measuring only the L and R channels is that if the measurements vs prediction doesn't agree, we need run the 4 measurements anyway to discover what went wrong and what new adjustment is needed.

Also, I've had a play around with my two subs to attempt to align them which I think I did correctly but it left me with a huge peak at 40hz (room mode) can this be EQ'd out at all or am I best leaving the subs alone?

Yes, the SWs are time aligned closely as shown in the chart. I had noticed that there was a little offset in time originally. I didn't recommend a minor timing change because the overall bass SPL looked very good and there would be no added value in the minor adjustment. You can decide which SW timing you feel is smoother. Any timing change will impact the SWs to mains XO timing so the SW timing is step 1 and the XO timing is step 2. In this case the SW timing change small enough that it is not likely to have any significant impact on the XO timing. I say this from my vague memory of the previous analysis results so it would be best for you to confirm any changes with new measurements.

Is this how the phase track at the bottom should look? I have absolutely no idea?

Yes

 

[Exponential]

@jtalden

Hi. I'm sorry for the huge delay but between birthdays and one of my kids being sick, I've not had chance to measure anything.

Anyway, I've remeasured my speakers with a 100hz x-over with delay applied to my mains of 5.5 metres which equates to the 16.000ms delay you suggested.
I'm unsure if this x-over is ideal though as I've been using it for a while now and there is definitely some "boominess" in places in both movies and music.

What does you knowledge tell you about the results?

 

[jtalden]

@jtalden
I've remeasured my speakers with a 100hz x-over with delay applied to my mains of 5.5 metres which equates to the 16.000ms delay you suggested.
I'm unsure if this x-over is ideal though as I've been using it for a while now and there is definitely some "boominess" in places in both movies and music.

What does you knowledge tell you about the results?

Oops, my mistake. I gave you bad info in Post-35. The timing looks very bad. The distance increase to the mains resulted in more delay shift of the SWs instead of less. I should have advised a 5.5 m increase of the SWs instead of the mains (or reduction of the distance of the mains) in order to reduce the delay time on the SWs. I get confused sometimes when mentally jumping between mains vs SW adjustments and timing delays vs distance settings.

In reviewing this proposed -16 ms SW delay timing option again, I see that the SPL support in the XO range is not as favorable. The group delay is reduced and thus the spectrogram looks more favorable in that regard. This is a popular adjustment to make and often the SPL is very similar. In this case the SPL at the XO is similar, but the SPL is as much as 6 dB down in other XO range frequencies. EQ may be able to address this SPL sag effectively, but I am not as confident that this is likely have much chance to be better than the original timing suggestion. It still is probably the best 2nd choice for timing if you are into experimentation.

 

[Exponential]

HI. Ah ok, I had a feeling it was a bit off but I wasn't sure to be honest. Isn't it funny how you instinctively know it's wrong yet you (meaning ME) will only do anything about it if told to do so!

I've been having a play around and found that a 75hz x-over could be beneficial but only if I have read it right?
It would mean first aligning the two subs then, using that aligned figure, get an average of the two subs (aligned) then adding that to the average of my mains.

Problem is, aligning the two subs involves a negative adjustment which I wouldn't know how to achieve (if at all).

It will be easier to just post the MDAT won't it!

 

[Exponential]

Come to think of it, I aligned the two subs with a negative delay. How would I achieve that in reality?

 

[jtalden]

I've been having a play around and found that a 75hz x-over could be beneficial but only if I have read it right?
It would mean first aligning the two subs then, using that aligned figure, get an average of the two subs (aligned) then adding that to the average of my mains.

Your timing analysis is correct for this 75Hz XO (or is it 80 Hz as the file is labeled) - no matter.
The SPL result and timing is very similar to the 100 Hz XO we chose.
Post-19 100 Hz XO SWs delay = -6.62 ms
Post-38 75 Hz XO SWs delay = -7.29 ms

SPL Comparison: (note that in the 75 Hz XO the SW gain was increased by 2 dB and in the 100 Hz XO it was not)

Phase Comparison:

Step Comparison:

 

[jtalden]

Come to think of it, I aligned the two subs with a negative delay. How would I achieve that in reality?

We are interested in the relative difference between them. If one SW needs a delay less than 0 ms in the MiniDSP, we can instead increase the other SW delay by the that amount.

When several speaker timing, gain or polarity changes are needed for an XO timing adjustment we can make a table to help keep track:
Enter all the the DSP delay settings and all the AVR distance settings that were used when making the measurements into the 1st column of the table. The Adjustments needed that were found from our analysis are entered into the 2nd column and the new settings are calculated in the 3rd column. If any of the those results cannot be set because they fall out of range of the hardware then we use the 4th column to identify the worst offender. That value (say -5.5 ms on SW2 when it is already at 0 ms) is used to instead adjust all the other speaker values +5.5 ms (or the distance equivalent) in the 5th column.

It seem relatively trivial to do mentally and it often it is when only one or 2 speakers need adjustment, but I am never really confident of the adjustments unless I do this when there are hardware limits involved and several speakers being impacted.

 

[Exponential]

Your timing analysis is correct for this 75Hz XO (or is it 80 Hz as the file is labeled) - no matter.
The SPL result and timing is very similar to the 100 Hz XO we chose.
Post-19 100 Hz XO SWs delay = -6.62 ms
Post-38 75 Hz XO SWs delay = -7.29 ms

SPL Comparison: (note that in the 75 Hz XO the SW gain was increased by 2 dB and in the 100 Hz XO it was not)
View attachment 32556

Phase Comparison:
View attachment 32557

Step Comparison:
View attachment 32558

I love how you do this! The way you describe it is like poetry yet when I try, t's like reading the Beano or a Dan Dare comic! (Yes, I'm over 40 and no spring chicken).

Yes, I aimed for a 75hz X-Over as trying for the standard 80hz was proving both difficult and frustrating.
I boosted the subs by 2dB to give me a touch of headroom for EQ purposes as the original measurement dipped quite a bit below 75dB. It gave me the lift in the X-Over region that I thought worked well.
If you disagree then please do say as I would rather follow your expertise than fumble through with my limited knowledge and ideas.

Of course, after manual EQ, I'll have to remeasure to ensure the EQ itself hasn't swayed the phase too much.

How do you feel the 75hz version look across the entire frequency range when compared to the 100hz flavour?
I didn;t expect to see the change across the whole range (in particular, up to 2Khz) so that surprised me as I have always just focussed on the 10-200hz range.

 

[jtalden]

Yes, I aimed for a 75hz X-Over as trying for the standard 80hz was proving both difficult and frustrating.

I just pointed out that the attached file was named 80Hz not 75Hz in case you attached the wrong file by accident. My analysis was based on the data in the file no matter what the XO was actually set to.

I boosted the subs by 2dB to give me a touch of headroom for EQ purposes as the original measurement dipped quite a bit below 75dB. It gave me the lift in the X-Over region that I thought worked well.
If you disagree then please do say as I would rather follow your expertise than fumble through with my limited knowledge and ideas.

The SW gain should be adjusted as needed to best accommodate the house curve we choose. I don't know your target curve so I can't comment on the gain change.
I only pointed it out as it explains why the SPL chart I posted shows more bass output. If we mentally account for the 2 dB gain change then the 2 curves would be very similar in SPL response.

Of course, after manual EQ, I'll have to remeasure to ensure the EQ itself hasn't swayed the phase too much.

I do that to confirm there are no mistakes in overall implementation anyway. I haven't seen a case where where SW XO timing needed readjustment, There is some phase impact of the EQ filters, but it is unlikely to be significant to the XO timing.

How do you feel the 75hz version look across the entire frequency range when compared to the 100hz flavour?

They look very similar to me when accounting for the 2 dB gain difference.

I didn;t expect to see the change across the whole range (in particular, up to 2Khz) so that surprised me as I have always just focussed on the 10-200hz range.

You are correct that only the XO range SPL is affected by timing adjustments. These are different measurements so there can easily be small differences due to setup or room conditions. I didn't see anything that suggested a problem. When I saw these differences away from the XO range it appeared that it represented a difference in smoothing setting prior to the alignment tool summation operation. I think one used no smoothing and the other used 1/48 octave smoothing. This is a trivial impact. Any small shift to the mic position would likely to be larger than this. Other changes as; setup, room, smoothing, etc, can impact anyplace in the measurement range.

 

[Exponential]

@jtalden

Good morning.

I realised last night that I had fudged up my previous measurements as I sent you a batch that were out of date.
Items have moved in my lounge so I needed to remeasure this morning.

My Pre Amp allows "listener position" alterations of between zero and 9 metres for L,R, Sub 1 and Sub 2 so, with the knowledge that I need a negative adjustment to align my subs (in the perspective of phase), I have set the distances for all speakers to exactly half of its range. 4.5 metres for each speaker. I hope that this method is correct as unsure how else I would do it.

I hope you don't mind but I'm going to upload my morning measurements for you to pick apart. If you have neither the time or inclination to look then I completely understand as what I am asking is taking up your personal time.

Having a look myself, after aligning my subs phase, it seems to me that a 75hz x-over could be of benefit but I may be wrong.

 

[jtalden]

I opened the 'Full Range...'.mdat first. From the SPL levels it appears you may be running your 2 SWs as left and right instead of mono. Is this correct? There not enough info in this file to be sure.

 

[Exponential]

I opened the 'Full Range...'.mdat first. From the SPL levels it appears you may be running your 2 SWs as left and right instead of mono. Is this correct? There not enough info in this file to be sure.

Hi.

Yes, that's correct although I'm amazed that you can tell that by just looking at a bunch of measurements!

The reason being is that I have the ability to align them both easier together that way.
Unless my thinking is off?

 

[Exponential]

Because the minidsp doesn't allow a negative value of delay, I thought it best to run them as left/right pair, set all speakers to 4.5 metres which would then allow a negative value of delay.
They are ultimately summed as one though and aren't being used as a stereo pair.

 

[jtalden]

I analyzed the 75Hz file for favorable SPL timing several ways and found no particular improvement to your settings. Your settings closely follow the conventional setup. The settings for the 85 Hz file were similar so I did not even try to improve it. Both these file have a significant SPL sag in the mid to upper bass range. Below are overlay charts of SPL, direct sound phase rotation and step response. The attached file can be used to see the spectrograms and other characteristics. For comparison I included the 100 Hz analysis of Post-17.

My take on this data is still that the earlier 100 Hz XO has a significant advantage of filling in the SPL of the mid and upper bass ranges better prior to EQ. This may, or may not, be a significant difference after EQ. Also that 100 Hz data may have been with different SW locations so I don't know if that is a positive or negative issue for you.

Using your equipment, it is possible to apply the needed delay setting for any of the setups we analyzed. Note that setting all AVR distances to the same distance value will apply 0 ms delay to all of them. So 1 m, 10 m, or 20 m settings for all speakers is still 0 ms for all speakers. The AVR will set the most distant speaker to 0 ms and then time delay the closer speakers as needed to account for the relative distance settings.

Thus when we want more room for reducing SWs delays in the DSP we just increase the distance of the SWs in the AVR without changing any of the main speaker distances. The AVR will then increase the delay on all the main speakers. When we then measure the system again we will find that all the main speakers are now trailing the SWs in time. This is a net reduction in delay of the SWs relative to the mains; just what we need.

I can create the table explained in Post-41 if given the DSP delays and AVR distances used when the REW measurements were taken. That table provides the actually DSP delays and AVR distance settings needed for each speaker rather than just the relative time adjustments needed.

 

[Exponential]

@jtalden

Morning.

It would appear from the measurements I have posted that there is clearly an issue with sag up to 500hz as you've noticed.
When comparing the previous measurements we have shared and analysed, this sag wasn't present.
This would make my measurements void.

The only change I made was to the delay settings in the Pre amp. I set them all to 4.5 meters.
Doing this has obviously had an impact on the output in a negative way.
It pains me to say this but this is all for nothing and I will have to re-do the measurements and set everything to zero.

I'm sorry about this.

I'll re-do them soon as I'm working over the next few days.

Mike.

 

[jtalden]

It would appear from the measurements I have posted that there is clearly an issue with sag up to 500hz as you've noticed.

I was referring to to the 60-160 Hz range where the higher XO (100 vs 75) provides more SPL. This is either because the XO provides more SW coverage in that area where the room makes the mains sag (as I was thinking) or possibly because of some other setup difference that I have lost track of. I also noticed the SPL differences above 160 Hz were significantly more than expected for similar measurement setups. Maybe the mic position was a little different? This difference does not impact the XO timing though so it can be ignored. When EQ is calculated, there will be new measurements with several different mic positions so it is not a concern for that process either. Using the current measurements for timing is probably fine.

When comparing the previous measurements we have shared and analysed, this sag wasn't present.
This would make my measurements void.

I would think the measurements are fine for the XO timing effort at hand.

The only change I made was to the delay settings in the Pre amp. I set them all to 4.5 meters.
Doing this has obviously had an impact on the output in a negative way.
It pains me to say this but this is all for nothing and I will have to re-do the measurements and set everything to zero.

As noted above a distance change of 4.5 m to all speakers in the Pre amp should not have changed the Pre amp delays at all. It should have still set 0 ms delay on all speakers as they are all the same distance away from the LP.

If you are more comfortable remeasuring that is fine. Chose the speaker positions, mic position and XO you want to live with and remeasure. I will again help to confirm your delay settings or provide suggested settings. If given the info on all current settings, I will include the table that provides new equipment settings for any suggested options. I hope we are done investigating different physical setups and XO frequencies as we are not likely to find a major improvement to the 5 or 6 we have already done.

I also forgot to comment about using the SWs in stereo mode rather than mono mode. I support mono mode and had assumed that would be the case as I agree with the majority experts that there is more benefit to it. Bass SPL is likely to be smoother overall in most situations. Many stereo hobbyist strongly prefer stereo mode. Please reconfirm which you intend to use so I can properly create and label any future channel SPL response predictions. All timing recommendations already made are still valid. Only relative gain between the SWs and mains is impacted.