Loopback Method Trying To Get It

Trdat

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Is the correct file? I was expecting 3 measurements, not 9.

Yes it is the correct file. Apologize, I just have taken multiple measurements just a habit to ensure there is consistency between the measurments.

If you want I can just upload the file with TW, MW and TW/MW together?
 

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Which 3 do you want me to use?
 

jtalden

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Okay, I will work on this later today.
 

jtalden

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Trdat,
For the analysis I first confirmed that a vector summation of TW and MW agreed with your measurement of TW+MW. It was very close (not shown). There was no need for me to adjust the timing of the MW to find the current relative timing. I then noticed that loopback timing was active for these measurements. Did you get the cable/adaptors you needed? If channel 2 loopback was not connected, let me know.

I then lowered the SPL of the TW by 8.0 dB to better match to level of the MW. We can adjust the driver levels and it will not impact the timing analysis, so it was not necessary for this analysis, but the charts look more reasonable when the SPL follows a typical house curve. I also shifted all 3 measurement impulses the same amount to set them nearer to 0 ms so that the phase is more easily read. You can use the alignment tool to do this instead when doing the analysis. I just prefer to do it manually. The chart below shows the XO range is 1.2-5.0 kHz for a 25 dB SPL drop so that is the primary range we are interested in for phase tracking and SPL support.
57126


The current timing is reasonably close to the best timing, but a small adjustment can be made to improve it. The chart below shows that the TW and MW phase crosses at about 5 kHz instead of nearer to the 2.2 kHz acoustic XO frequency.
57127


The chart below shows that an alignment tool adjustment of -0.06 ms in MW delay timing provides a little better phase tracking. The improvement in SPL support is only about 1 dB better so it's not very significant. If the Hypex can make a fine adjustment however you could increase the delay in the TW by 0.06 ms since you can't reduce the delay on the MW as you already have it set at 0ms.
57128


Just FYI, the chart below shows the closest phase tracking is achieved by inverting the MW and delaying it 0.12 ms. This does not provide any significant improvement to the SPL. If the L and R mains have the same drivers, then you should keep all the MW polarities the same.
57129


The chart below shows the impact on SPL of the 3 timing situations. All 3 look favorable.
57130
 

Trdat

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JtAlden,

Yes, I did use loopback. And it seemed to work 100%. Actually, once I chose ASIO it made a whole heap more sense, I was trying to work out your intructions when Java was enabled, I had no idea ASIO had to be enabled at the time of your explanation. So the input outputs were simple enough.

I will read through this thouroughly and get back to you tonight(my tonight). Really appreciate the response.
 

Trdat

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Unfortunately Audio Nirvana will be offline this weekend but I have copied this page to practise and get back to you on Monday, I appreciate your effort.

I did give it a go, but my results were a little different possibly because I didn't shift the measurement impulses manually. Can you tell me how to do that? All I did was place the cursor on the crossover point and align automatically which gave me .08ms rather than your .06. I can see you can play around with it to make it better.

Also, you have different crossover points in some of the posts above if I am reading correctly. Is that because you played around with the crossover to see what the best result could be? But the final result is for 2200hz crossover right?

So essentially we are looking for a decent SPL with the best phase tracking in the bottom graph, I got the hang of it but i will keep analysing it.

My last question is regarding the next step, adding biquads. Do I use the 1/48 smoothing and the averaged response to figure out where the biquads go is that the jist of it? Such as the last graph you posted. Its just there is a a lot of bumps and dips, where do I start? Just the basic concept can push me towards the right direction so I can think about it while I am working on the delays.

Once I am confident I will try the woofer with the MW delay myself. But will send to you for confirmation.

And yes, my drivers for left and right are the same but it has a passive crossover.
 

jtalden

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I did give it a go, but my results were a little different possibly because I didn't shift the measurement impulses manually. Can you tell me how to do that? All I did was place the cursor on the crossover point and align automatically which gave me .08ms rather than your .06. I can see you can play around with it to make it better.
As mentioned, the relative level of the 2 drivers will change the appearance of the XO range and thus the apparent or acoustic XO frequency. If you did not make the same -8 dB TW SPL level adjustment the XO range appearance will be different. You will find that the choice of the cursor placement within in the XO range can make a difference in the timing suggestion of the alignment tool. The -0.08 ms suggestion is perfectly fine. The difference between -0.06 and -0.08 ms is not really significant. The SPL support is still good, and the phase crossed very near the XO frequency.

For fine tuning, I like to watch the SPL support across the XO range as minor manual changes are made to the timing and pick the timing that looks to provide the best overall SPL support. We could just type in different numbers into the box, but that isn't efficient. To manually do this more easily we can click on the location spot (little button) within the MW timing slider. There will be no indication of any change after this is done unless you miss the button a little and the timing changes. If that happens it doesn't matter the following feature still becomes activated. We can now change the timing in 0.01ms steps using the left and right arrow keys on the keyboard.
Also, you have different crossover points in some of the posts above if I am reading correctly. Is that because you played around with the crossover to see what the best result could be? But the final result is for 2200hz crossover right?
I am not changing your choice of the electrical XO frequency. I don't know what that is. I am just identifying your XO as a practical matter by looking at the effective or acoustic XO that results. The center of the range appears to me about 2.1-2.3 kHz now that the TW level was reduced. The acoustical center often differs a little from the electrical center.
My last question is regarding the next step, adding biquads. Do I use the 1/48 smoothing and the averaged response to figure out where the biquads go is that the jist of it? Such as the last graph you posted. Its just there is a a lot of bumps and dips, where do I start? Just the basic concept can push me towards the right direction so I can think about it while I am working on the delays.
The XO frequency and filter slopes are per your discretion. If you make a change from the current settings that will impact the timing to some extent so I would not make a change without a good reason. The EQ methodology you choose is also your choice. I thought you were going to use Audiolense for that.
 

Trdat

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I did add 8db gain.

When you say the phased crossed near the XO frequency is that what we are looking for in the bottom graph?

Also, how do I get my phase graph to look like yours, below mine looks very confusing while yours has only got a few lines matching up?

We could just type in different numbers into the box, but that isn't efficient. To manually do this more easily we can click on the location spot (little button) within the MW timing slider. There will be no indication of any change after this is done unless you miss the button a little and the timing changes. If that happens it doesn't matter the following feature still becomes activated. We can now change the timing in 0.01ms steps using the left and right arrow keys on the keyboard.

I did this, getting the hang of it. I think I still need to learn exactly what is going on in the bottom graph but at least now I get an idea, plus the automatic correction gives you a fair idea.

By the way both my tweeter and MW in my passive left/right are inverted polarity. So, I can invert the MW polarity and use .13 delay. I tried that and did notice a much better phase tracking but with worse of SPL. So then what we would do if this option is chosen is to biquad the SPL right?

Of course, I am also guessing that both options of delays need cross checking with a measurement to ensure the frequency repsonse is what REW is showing after delay and possibly inversion is set.

The XO will stay the same and I am fully aware that it will effect the timing.

No, unfortunately I can't use Audiolense for my DSP as this centre speaker is connected to a Home Theatre amp plus there is a delay when watching TV with Audiolense. I have to add the biquads through the Hypex filter and that is my next step, I am still not sure if its worth the effort to learn VituixCad it probably is but all in good time.

I think I mentioned that Audyssey can give me a half decent frequency correction till I learn how to perfrom biquads. I know how to use Biquads just want to get an idea a simple way to choose what Frequency area needs a correction. Hence why I thought maybe a 1/48 smoothing as per your alignment tool might be a good starting point?

My last question is going to be when I measure the woofer with the MW its not going to be exactly the same place is that going to be okay? Maybe I should have measured all 3 at the same time but its to late now so as long as the woofer and MW is measured from same place would that work?

Thanks again. Apologize for so many questions but I think my questions will calm down after this.

1669484294625.png
 

jtalden

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I did add 8db gain.
I suggest doing that using; REW All SPL tab/Controls/Measurement action/"SPL offset"/"Add offset to data". The levels will then appear correctly in the alignment tool.
When you say the phased crossed near the XO frequency is that what we are looking for in the bottom graph?
Yes, that is one consideration. The other is close phase tracking. Your measurements have no room effects in the XO range so there are no other concerns in this particular case. The SPL support is more important than the exact phase crossing point.
Also, how do I get my phase graph to look like yours, below mine looks very confusing while yours has only got a few lines matching up?
We could have used REW impulse tab controls/"estimate IR delay"/"shift and update timing offset" following the TW measurement and before the MW measurement. The TW will be moved to near 0 ms and all the measurements made following that will also be moved the same amount.

Since we didn't do that, we can use REW Overlays window/Impulse tab/Controls/"Set t=0 at cursor" after we have placed the cursor near the initial peak of the TW. Be sure that all measurements are selected that you want to move. In the chart below the cursor was place near the peak of the TW. All 3 measurements will be shifted -1.861 ms to 0 ms when we select "Set t=0 at cursor". That is what I did.

Impulse overlay.jpg


By the way both my tweeter and MW in my passive left/right are inverted polarity. So, I can invert the MW polarity and use .13 delay. I tried that and did notice a much better phase tracking but with worse of SPL.
I would set L, R, C speaker drivers the same. Thus, C should have TW and MW set inverted as well. If the same or similar XO filter settings are used for all 3 front speakers, then they will be well matched for phase response and group delay.
So then what we would do if this option is chosen is to biquad the SPL right?
I don't understand this question.
Of course, I am also guessing that both options of delays need cross checking with a measurement to ensure the frequency repsonse is what REW is showing after delay and possibly inversion is set.
Yes. it's always best to assure no mistakes were made.
No, unfortunately I can't use Audiolense for my DSP as this centre speaker is connected to a Home Theatre amp plus there is a delay when watching TV with Audiolense. I have to add the biquads through the Hypex filter and that is my next step, I am still not sure if its worth the effort to learn VituixCad it probably is but all in good time.

I think I mentioned that Audyssey can give me a half decent frequency correction till I learn how to perfrom biquads. I know how to use Biquads just want to get an idea a simple way to choose what Frequency area needs a correction. Hence why I thought maybe a 1/48 smoothing as per your alignment tool might be a good starting point?
There's usually help available here for EQ support using REW. This help with the XO delay is enough work for me, so I suggest you start another thread for EQ support when you're ready. The smoothing is somewhat dependent on what process is used. 48 dB/octave is okay for SW frequencies but is to too coarse for midrange PEQ.
My last question is going to be when I measure the woofer with the MW its not going to be exactly the same place is that going to be okay? Maybe I should have measured all 3 at the same time but its to late now so as long as the woofer and MW is measured from same place would that work?
I suggest the mic placement is as explained previously if you want to optimize the centering of the direct sound lobe. Place the mic on the listening axis from LP to the midpoint between the MW and Woofer. The 1 m distance from the baffle is fine. Mic placement is not very critical for a Mw to W XO as the wavelengths are long enough that the central lobe is much larger.

Regarding your chart:
The SPL support in the XO range is poor because the MW delay is set at 0.08 rather than -0.08 ms. Your charts should be the same as the ones I posted.
 

Trdat

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Regarding Biquads I will open a new thread to get the basics down pat. The above is great, and I also have been looking through all the other threads they all tie in together and reinforce what I have learnt. I think all I need to do is read more about the phase matching and I will understand better exactly what is going on in the bottom graph.

But, If you can just help me with the woofer and MW timing as well I would have half the job done. Actually, more than half the job.

I attempted it myself, but REW gave 1.18 delay on the MW not sure if that is normal? I have added the mdat files if you don't mind taking a quick look it would be appreaciated. No need for a thourough explanation.

The questions that come to mind is...

Do we add the delay to the MW?
And do we subtract the TW delay from the MW delay or no need for that? I ask cause wouldn't a delay between MW and Woofer offset the MW as it was 0 sec originally...?

And if we have an AVR how do we do the timing between the main speaker and sub. I've seen the other threads I understand how to do it what I mean is if the AVR is set by distance how do we input the sec of delay into the AVR. Usually, the AVR does it automatically but if we want to perfect it is there a way?
 

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  • Centre Speaker same miczipalignemnt.zip
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jtalden

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Are both XO filters active and set correctly in this data? There is more SPL overlap than I would expect.
 

Trdat

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Are both XO filters active and set correctly in this data? There is more SPL overlap than I would expect.

It should be but looking at it maybe they were disengaged for some reason. Let me measure again and send it just to make sure. The preset was changed perhaps I accidently used a preset with nothing on it.

I measured again, this one for sure the crossovers are in the DSP preset.
 

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jtalden

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It should be but looking at it maybe they were disengaged for some reason. Let me measure again and send it just to make sure. The preset was changed perhaps I accidently used a preset with nothing on it.

I measured again, this one for sure the crossovers are in the DSP preset.
I compared the 2 files and confirmed they have the same XO settings. I will use Post-36 data for the analysis. This time I will eliminate some of my normal manual steps and mainly use the REW alignment tool. It should be easier for you to understand. The detailed analysis is now in process.
 

jtalden

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If you can just help me with the woofer and MW timing as well I would have half the job done.

I attempted it myself, but REW gave 1.18 delay on the MW not sure if that is normal?
No, I find a -0.47 ms delay change on the W (or a +0.47 ms change on MW+TW combination) provides the best timing with the driver polarities as posted.

My original analysis analysis however found that better tracking was achieved with the W inverted.
The following is the detailed step-by-step process I used for the analysis.

Steps:
  1. Did some personal housekeeping; renamed the 2 files (short and sweet), moved the woofer below the MW [I like to put the higher frequency drivers above the lower ones.]
  2. Select All SPL tab and set 1/48 smoothing
  3. Open alignment tool and place the W in the lower position
  4. Open IR window panel
  5. Set FDW to 5-cycles and apply to all
  6. Reset frequency and SPL ranges to better see the range of interest
  7. Place the cursor near the SPL crossing of the MW and W (about 600 Hz)
  8. Select "Level phase at cursor"
  9. Notice that phase of the 2 drivers is about 180° offset from each other. Invert W such that the phase tracks more closely
  10. Select "Align phase at cursor" [The 1st chart below shows the result at this juncture - excellent phase tracking and SPL support]
  11. Remove the FDW from both measurements and confirm that the SPL and phase is still favorable.
  12. Select "Aligned Copy" of the W and then "Aligned sum" [The second chart below shows the final result.]
Results:
The most favorable timing for this configuration is to invert the W and increase its delay by 0.16 ms with respect to the MW+TW combination. My mdat file is attached. If this puts the W driver polarity of the C different from the L and R mains, I do not recommend this setting. The 3 channels should all share the same polarities of their 3 drivers. So, if the posted polarity relationship is correct, the -0.47 W delay change noted above is the correct one to use.
The questions that come to mind is...
Do we add the delay to the MW?
And do we subtract the TW delay from the MW delay or no need for that? I ask cause wouldn't a delay between MW and Woofer offset the MW as it was 0 sec originally...?
These should be cleared up now. If not then provide more detail.
And if we have an AVR how do we do the timing between the main speaker and sub. I've seen the other threads I understand how to do it what I mean is if the AVR is set by distance how do we input the sec of delay into the AVR. Usually, the AVR does it automatically but if we want to perfect it is there a way?
If you run Audyssey it will set the delay. If you need to set it manually or confirm/correct the Audyssey setting you can do this analysis again to determine if a W distance change is needed.
1 ms delay = -0.345 m (-1.32 ft.) distance, i.e., an increase of delay time is achieved with a decrease of distance setting in an AVR.

AT 5cycle FDW.jpg


AT without FDW.jpg
 

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