# Another time alignment how does this look thread



## cadet (Dec 28, 2016)

Attempting to perform t/a using a UMIK-1 & Rew. I've read probably a 100 post & spent hours researching the how's & why's. While they were extremely helpful, I'm still left a little unsure about the timing of my tweeters. So I'm attaching my file & if any one would be kind enough to take a quick glance & see if everything looks acoustically lined up per the measurements I'e achieved, I would appreciate it very much. And for a quick glance I'll attach some pics as well.


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## jtalden (Mar 12, 2009)

I've not seen measurements like this for time alignment. Possibly there is a method, but I can't imagine how it can be done from this data. It does suggest there is no gross timing error from the positions of the impulses.

You swept 1000-1001 Hz for the MR and 3000-3001 Hz for the TW. Normally the sweeps are full range, or at a minimum the width of the XO range for both drivers. 

There is a method discussed here long ago with a narrow range sweeps centered on the acoustic XO frequency, but I have too little experience with it to be sure it will work well in all situations.

The file is labeled as 'Truck' so it may be impossible to align MR to TW using my normal method. If you want me to attempt to check your settings new measurements would be needed. I can provide detailed measurement requirements if you identify the drivers and XO's employed.


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## cadet (Dec 28, 2016)

jtalden said:


> I've not seen measurements like this for time alignment. Possibly there is a method, but I can't imagine how it can be done from this data. It does suggest there is no gross timing error from the positions of the impulses.
> 
> You swept 1000-1001 Hz for the MR and 3000-3001 Hz for the TW. Normally the sweeps are full range, or at a minimum the width of the XO range for both drivers.
> 
> ...


The thread I ended up following for T/A is: http://www.diymobileaudio.com/forum...g-impulse-response-ta-using-rew-umik-1-a.html 

I'm attempting to align JBL components for my setup in my vehicle. There a set of 6.5" woofers located in the door panel & a 1" tweeter located in the dash. I can either run a HDMI to my headunit & send signals out that way or run rca's to my MiniDsp C-DSP. If you could provide any details I'd greatly appreciate any feedback eager to learn & if someone like yourself is willing to help. I'm all ears.


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## JohnM (Apr 11, 2006)

Unusual approach. For making relative measurements on graphs in REW hold down the Ctrl key then click and drag the right mouse button.


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## jtalden (Mar 12, 2009)

Thanks for the link. I just gave it a quick scan. The logic of this method is still not entirely clear to me. It would seem to align the timing of the MR and TW at 2 different frequencies (1000 and 3000) rather than at the acoustic XO frequency. If those 2 frequencies are chosen the middle of bandpass range of each driver I thinking the timing result may be pretty accurate. I cannot be sure how close it is. In any case, it does provide a way to assure the delays are close to the correct timing. 

My normal method has not been very effective in several auto applications due to the strong early reflections so it may not be much use here. A fallback is to get a reasonably close alignment as you have done already and then either just except it or possibly see if it can be fine tuned.

> If you want me to try confirm it is good as is, or suggest an adjustment:
Sweep each of the 4 drivers individually using full range sweeps (minimum sweep range is XO frequency ±2 octaves) with REW acoustic timing activated. Leave your current XO and delay timing in place. 
[So, if your XO is set to 2k, set the sweep to a minimum of 500-8000 Hz.]
Sweep:
L-W (left Woofer)
R-W
L-T
R-T

I can work from that info if you post the mdat file.​> You can confirm timing yourself with this same set of measurements along with the 2 additional ones:
L-W + L-T (left channel)
R-W + R-T

For each channel use the REW SPL overlay chart to confirm that the gap in the rolloff of the W and T (XO range) is well filled by the W + T trace.
If it isn't then increase the delay of the W in small increments (~0.03 ms for a 2K XO) and remeasure W + T. Do that for 7 increments (8 different W delays) and chose the delay that provide the best SPL fill in the XO range. It is best to chose a W delay that is the same value for both channels so there may be an compromise W delay choice needed between the 2 channels.​
Below is an example of an overlay chart showing good SPL fill in each of the 3 XO ranges:


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## cadet (Dec 28, 2016)

Perfect! Thanks for your response. I'll get back out & take some more measurements. I see what you're getting at. The method described in that thread generated anomalies when attempting to measure as well. I would get different readings almost every-other measurement requiring to take several measurements & eventually you would see a pattern. 
There is also this articl published my MiniDSP, this method was unsuccessful for me as well. https://www.minidsp.com/applications/auto-eq-with-rew/measuring-time-delay
I think if a loopback was used it would work, but as an acoustical reference is being use it produced results that were inconsistent, just like mentioned above.


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## jtalden (Mar 12, 2009)

That's a concern... I must have missed that bit. This is a problem for my normal analysis method.

The first requirement is that we should be able to remeasure a driver several times in a given setup and get the same impulse location on the chart. So, if the impulse position is moving position in repeated measurements it is a problem. You should have selected one of the 2 tweeters for the reference. If a driver's impulse moves using that reference then try using the other tweeter for the reference. If neither tweeter is stable as the reference then it is a problem for any of the common timing methods.

Can you show me several repeated measurements of the better tweeter for stability using it both as the reference and as the measurement driver? Your 'several measurements to see a pattern' method may work if there is only occasional outliers. If you have sorted through all this and are satisfied with your ability to selecting 'good' measurements for the timing analysis then we can just use those good measurements.

If we think it is too random then possibly only a loopback cable and XLR mic setup will work.

> Now thinking of the trial and error process that was the second bullet in Post-5: 
That process will still work just fine so long as you feel the initial delay timing you have found is good. If those starting points (delays set) are good as shown in the final chart in Post-1 then the 8 increment process can be done with out even using the acoustic timing. We are just offsetting a known time increment from a known good starting point and checking the impact on SPL. The best XO range SPL fill is the best answer. Acoustic timing on, or off, is not an issue in this method.


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## cadet (Dec 28, 2016)

@jtalden
I'm attaching my mdat file. I took measurements in the following order.
FRT as ref
FRM
FLM
FLT
I then ran a pass with the FRT+FRM & FLT+FLM.
*Note:* All t/a settings remained(the t/a settings I came up with using the method I posted to)
All X-over remained in place, I have the TWT's & MID's crossed at 3,000.
Please see if you can work some magic. I still have some level balancing & eq to do, but I want to get my x-overs & t/a done first.


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## jtalden (Mar 12, 2009)

I analyzed this 3 kHz XO data:
> I noted that the timing is not the same as the initial charts you posted, but the difference is relatively small and probably the result of a slightly different mic position. Thinking through this, I presume that in many, if not most all, car/truck situations the midrange and tweeters are separated from each other by a significant distance. They are also often separated both vertically and horizontally and the left vs right channel geometry is very different. In this situation it takes only a small mic position difference to have a significant impact on 3 kHz XO timing. [This shows my lack of experience in car/truck setups as I am now just thinking through the impact of all this.]
> My normal timing method is completely unsuitable for this situation. The strong early reflections of the tweeter overwhelms its direct sound.
> I did adjust timing using a couple of different approaches and checked the impact on the SPL. Of course a minor SPL improvement is possible at the exact XO frequency when the timing is corrected for that exact mic location, but the improvement is not uniform over the XO range and is not likely to impact the sound quality. 

So my analysis is:
> Your current timing is very good in setting the basic sound arrival time for the 4 drivers at the mic location. 
> It is not helpful to fine tune the timing further due to the basic geometric considerations: 
1. The 2 ear locations are significantly different from the mic locations regarding timing. 
2. It takes only very small head position change to significantly change the effective timing.​
I thus conclude that I cannot suggest an alternate timing that is likely to provide a significant improvement to the current timing.


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## cadet (Dec 28, 2016)

Thanks jtalden! The centering of the image does sound pretty good. I think what I'm gonna get back out today, do some level matching & adjusting x-overs to see if I'm ready to start eq'ing. Thanks for all your help!


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## oliverlim (Jan 1, 2017)

Hi jaltan,

Could you help me look at my left and right tweeter measurements? I am trying to see if REW can help me TA my car 3 way active. I will do a full set if that is required. But just want to make sure that my tweeter measurement is correct.

Thanks!


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## jtalden (Mar 12, 2009)

I understand correctly you are only asking if the 2 tweeters are delayed properly for sound to arrive at the mic location at the same time?

If so:
> Acoustic timing is on as it should be so this data can be used.
> You have measured 1000-1001 Hz.
[This seems a strange method and frequency for tweeters. This is below the XO frequency for most tweeters and the sweep range is too narrow.]
We can try to use this data anyway:
> For tweeter to tweeter timing alignment (2 identical drivers in different channels) we can just look at either the Impulse chart or the ETC chart.
> For car timing situation the ETC overlay is probably the easier chart to use. 

So looking at the ETC chart:
It appears the ETC of L-TW is leading the R-TW by about 2.8 ms.








Shifting a copy of the L-TW by -2.8 ms (an additional delay) results in better alignment of the peak energy from the 2 TWs.








> The issues here are:

This is at 1000 Hz and we don't know what is happening at any other frequency. The arrival at another frequency can vary greatly in this type of situation.
The TW peak energy arrival is influenced by all the bouncing around of the sound that occurs in a typical car application. This may be as good or better then using the Impulse to align speakers in a car application.
It would be more common/logical/traditional to align the initial rise of the 2 impulses instead of the 2 ETC's. Doing it that way the needed L-TW delay would be 3.1 ms.
Looking at the Impulse chart the polarity of the 2 tweeters appears to be reversed. That is; we would need to invert one of the TWs to agree with the polarity of the other one. The problem is again that this may only be the case at this one frequency. The other frequencies may provide a different story. The ETC chart is no help in polarity determination as it is always plotted as an absolute value.
Suggestions:

If the polarity is wired correctly then that is the best indicator. This data is too narrow to really determine polarity with any confidence. The polarity reverses at different frequencies due to reflected sound in the car.
If the geometry (difference in measured distances from the Mic to the 2 TW's supports a 2.8-3.1 ms change to the L-TW your delay settings then this is an appropriate adjustment. If not, the measured distance difference is the better method. Your notes seem to indicate the R-TW speaker is currently delayed 1.46 ms which seems backward to me. If the R-TW is reset to 0 and L-TW is delayed the 1.46 ms then that is a difference of 2.92 ms or about the same range as my recommended adjustment. Possibly you just delayed the wrong TW?

If you want to confirm the delay setting it is better to measure as:
> Acoustic timing on.
> XO set on.
> Sweep set full range (or a minimum of XO frequency to 18k Hz).
> For timing analysis it is helpful to have a reasonably smooth frequency response. It is thus helpful to do some rough EQ work on the TW response if it is currently very irregular.


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## oliverlim (Jan 1, 2017)

Thanks jtalden!

I will try to do a full measurement of Tweeters/Mids/Woofers later. I guess part of the confusion could be that you are thinking this is a LHD car. Its a Right Hand Drive car. So the right tweeter would be delayed more then the left. 

I will try to capture all the data with the reference timing on. I seem to be having issues getting it to run once I enable the option. It seems to hang after reaching 19% or I get a waiting for reference signal prompt. So I was hoping that I get a sense of how good or bad my TA is by just capturing the signal without timing reference since the plots seems rather consistent. In the meantime, thanks again.



jtalden said:


> [/LIST]
> [/INDENT]
> Suggestions:
> 
> ...


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## oliverlim (Jan 1, 2017)

Not sure why. I just cant seem to get the reference timing to work. it just hangs at 19%. So I just measured my 3 way active in sequence of LW RW LM RM LT RT in my RHD car. I inverted both my tweeters just to see if it made a difference compared to yesterdays tweeter only measurement. 

I am looking at my graphs now to see if it made any difference at my crossover of 3.5k


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## jtalden (Mar 12, 2009)

Confused? Me? Hmm, RHD... I'll try turning around to face the other direction and see if that helps me make any better sense of this. :R

2.5 ms + 3ms would then seem to be too much. Maybe you drive a large mobile home... 

More seriously, I agree there appears to be a problem with the acoustic timing. I will look at he new data to see if it helps us in any way. It may take a couple off day as I am tied up with other matters at the moment.

If you can't get repeatable measurements using either TW for the reference, then there may not be much we can do beyond setting the delay to the measured difference. I would expect that to be a good setting for a car application.


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## Phillips (Aug 12, 2011)

Hi I am trying to use the Acoustic timing.

Do I leave the "Acoustic Timing" selected in the preferences for all measurements when trying to time align speakers?

Thank you


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## JohnM (Apr 11, 2006)

Yes


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## oliverlim (Jan 1, 2017)

I am still not getting if I am using this function correctly. Please let me know if I am getting this right.

After connecting my headphone/output from my notebook via a 3.5mm to 3,5mm input on my car, I will start REW.

1. Go to Preferences > Analysis. Choose "Acoustic Timing Reference" from the drop down menu

2. Go to Preferences > Soundcard for the "Output Device" choose my soundcard in the drop down menu.

3. For the "Output" choose speaker. The drop down box that contains "Left" "Right" or "Both". I choose both. Is this correct?

4. Make sure Mic is recognized. Close Preferences

Now go to Measurement, and this is where I am also not sure what I should be doing. I can mute any of my 3 way active speakers. The furthers speaker is my left mid (RHD car) but I understand the reference speaker should be a tweeter. So Left tweeter should be the best reference. 

So in the measurement, I should use 5k to 12k as the sweep? Speaker output as both and reference speaker as Left. I then mute all except both my tweeter and click on wait for reference speaker?

After this, whats my next step? How do I align say my right mid to the left tweeter and what sweep frequency should I use? I see some instructions which as that we disable all crossovers on the DSP. Is this neccessary?

Thanks!


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## jtalden (Mar 12, 2009)

> The Reference channel can be either channel L or R. 
That channel TW has to be active - not muted. This same TW is used as reference for all measurements no matter which measurement channel or driver is being measured. Pick the TW that provides repeatable results as the reference TW. Either one should work in most cases. Assume We select L-TW for discussing below. 

> The measurement channel contains the driver(s) we are measuring.

So, when are measuring the L-TW:
Reference = Left
Measurement = Left

So when are measuring the R-TW:
Reference = Left
Measurement = Right

There is never a reason to select 'Both' channel as 'measurement' when doing time alignment work. We would get the both TW's measured together if we did that in this example.


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## jtalden (Mar 12, 2009)

oliverlim said:


> After this, whats my next step? How do I align say my right mid to the left tweeter and what sweep frequency should I use? I see some instructions which as that we disable all crossovers on the DSP. Is this neccessary?


> All XO's should always be active or any measurements are useless. Also, the drivers may be damaged. [XO's impact the timing alignment.]
> I just sweep full range for all measurements. I know of no advantage to reducing the range.
> To time align the L-TW to the L-MR switch the reference the R-TW:
Reference channel = Right 
Measurement Channel = Left
> Measure L-TW (mute the left MR and W)
> Measure L-MR (mute the left W and TW)

If one of the TWs is not repeatable as the reference then it is a little harder. We can cover that if needed.


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## oliverlim (Jan 1, 2017)

jtalden said:


> > All XO's should always be active or any measurements are useless. Also, the drivers may be damaged. [XO's impact the timing alignment.]
> > I just sweep full range for all measurements. I know of no advantage to reducing the range.
> > To time align the L-TW to the L-MR still assuming switch the reference the R-TW:
> Reference channel = Right
> ...


Thanks! this is very clear now. Just a couple of questions.

Full range sweep means? 20-20K. The default in my case always seems to be 5k to 12k?

If I set LT as my reference. it means I can only "TA" my right tweeter, mids and woofer to it. So once I have done that, I will use RT as my reference and do left mids and woofer to TA against my RT.

Did I understand this right?:wave:


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## jtalden (Mar 12, 2009)

Yes, that's right. If you are checking timing between 2 drivers within a channel, use the other channel TW for the reference. Otherwise the measurement TW would also play along with the W and MR during their measurements.

I don't know what you mean by your 'default' sweep range. We set the range to whatever makes sense for the experiment. I use a 20-20k range for timing studies as that is the working range of the speaker drivers I use. 'Full range' is full range of the channel capability, not full range of the REW sweep capabilities. If the woofer is flat down to 40 Hz and the TW flat to 18 kHz Then a reasonable range is maybe 20-20k. It is not recommended to set 2-24k range for example. The woofer may not be happy with that and we don't care what happens above 20k, it out of our hearing range. 

When using full range sweeps we don't have to decide what setting range is needed for this or that XO timing evaluation. It saves time and reduces the mistakes.


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## jtalden (Mar 12, 2009)

I just took quick look at the last data:
> The TW impulse looks good in both channels so probably either TW will work fine as the reference.
> Without confidence in the timing reference there is no timing recommendation possible using this data.
> The current chosen sweep ranges are too narrow to cover the entire XO ranges. Please simplify and use full range measurements for all measurements.
> The SPL test level is higher than necessary. The same results will be found with SPL levels averaging roughly 75dB.


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## oliverlim (Jan 1, 2017)

jtalden said:


> I don't know what you mean by your 'default' sweep range. We set the range to whatever makes sense for the experiment. I use a 20-20k range for timing studies as that is the working range of the speaker drivers I use. 'Full range' is full range of the channel capability, not full range of the REW sweep capabilities. If the woofer is flat down to 40 Hz and the TW flat to 18 kHz Then a reasonable range is maybe 20-20k. It is not recommended to set 2-24k range for example. The woofer may not be happy with that and we don't care what happens above 20k, it out of our hearing range.
> 
> When using full range sweeps we don't have to decide what setting range is needed for this or that XO timing evaluation. It saves time and reduces the mistakes.



As I will be muting the drivers that I am not testing for TA, I would gather that the full sweep would then be in my case, be say 20hz to 300hz for my woofer (250hz lr24 crossover), 200-4K for my mid (lp 250hz lr24 and hp 3.5K lr24) and 3K to 20K for my tweeters (hp 3.5K lr24), Just a slight overlap at the crossover point. 

Is this right?


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## oliverlim (Jan 1, 2017)

Got the reference timing working. It seems like using mt LT as reference, my right Tweeter and mid are around 0.06-0.08ms faster then my RT which should be within margins of error. RW is 5-6ms slower. But I think I cant do much about that.

However, if I take my RT as reference, and compare it to my left mid, it is off by 2.5ms I forgot to take my right tweeter measurement. But I am almost sure my left TMW are quite in alignment when I was checking using another tool TDA.

Let me know if I am measuring and reading this right. I will redo another measurement tomorrow. Thanks!


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## jtalden (Mar 12, 2009)

oliverlim said:


> As I will be muting the drivers that I am not testing for TA, I would gather that the full sweep would then be in my case, be say 20hz to 300hz for my woofer (250hz lr24 crossover), 200-4K for my mid (lp 250hz lr24 and hp 3.5K lr24) and 3K to 20K for my tweeters (hp 3.5K lr24), Just a slight overlap at the crossover point.
> 
> Is this right?


No.
The sweep ranges you set are not wide enough. Per Post 22, full range is 20-20k for *all measurements.* The unmuted driver is protected by the XOs and will only play the range that is normally passed to them by the XOs. This is the same as when playing music through them. We are just muting the drivers we don't want to play.


*Again, be sure the XO's are active otherwise the TW may be damaged with the low frequency part of the sweep.*


Let's start over from the beginning with first steps. 
Step 1. Confirm that both TW's can be used for the reference signal.
> Reference channel = Left
> Measurement channel = left
> All XO's = active
> Mute all drivers except the L-TW
> REW Acoustic timing = On
> Set REW sweep = 20-20k
> Measure 
> Measure again 5 more times


You can confirm that the 6 measured Impulses of the L-TW all fall directly on top of each other. If there is a problem with that post the overlay impulse chart showing the problem. Be sure to use maximum zoom on the X axis.


Do the same for the R-TW:
> Reference channel = Right
> Measurement channel = Right
> All XO's = active
> Mute all drivers except the R-TW
> REW Acoustic timing = On
> Set REW sweep = 20-20k
> Measure 

> Measure again 5 more times


You can confirm that the 6 measured Impulses of the R-TW all fall directly on top of each other. If there is a problem with that post the overlay impulse chart showing the problem. Be sure to use maximum zoom on the X axis.


If the 2 charts show the impulses are on top of each other then both TWs are good to use for timing. I will detail step 2.


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## jtalden (Mar 12, 2009)

oliverlim said:


> Got the reference timing working. It seems like using mt LT as reference, my right Tweeter and mid are around 0.06-0.08ms faster then my RT which should be within margins of error. RW is 5-6ms slower. But I think I cant do much about that.
> 
> However, if I take my RT as reference, and compare it to my left mid, it is off by 2.5ms I forgot to take my right tweeter measurement. But I am almost sure my left TMW are quite in alignment when I was checking using another tool TDA.
> 
> Let me know if I am measuring and reading this right. I will redo another measurement tomorrow. Thanks!


> What is an mt LT? It has to be a Tweeter for the reference channel.
> How do you know the reference is repeatable? I do not really understand your comments. Let's just start over from the beginning to be sure we are doing this right.
Please follow Post 26 instructions to confirm the repeatability of the 2 TW when use as a reference.
Post the 2 overlay impulse charts, one showing the 6 L-TW impulses and one showing the 6 R-TW impulses.
I will then detail the next steps.


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## oliverlim (Jan 1, 2017)

jtalden said:


> > What is an mt LT? It has to be a Tweeter for the reference channel.
> > How do you know the reference is repeatable? I do not really understand your comments. Let's just start over from the beginning to be sure we are doing this right.
> Please follow Post 26 instructions to confirm the repeatability of the 2 TW when use as a reference.
> Post the 2 overlay impulse charts, one showing the 6 L-TW impulses and one showing the 6 R-TW impulses.
> I will then detail the next steps.


Did 6 times left reference left test tweeter, and 6 times right reference right test tweeter. And then 13 is left reference right tweeter test and 14 is right reference and left tweeter test. 

File too big so using a drop box link instead.

https://dl.dropboxusercontent.com/u/7076338/13 MAr 2017 Tweeter Reference 12 times.mdat


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## jtalden (Mar 12, 2009)

Well Done!
> Either TW works well as the timing reference.
> The delay that is current set between the L and R channels is very good.
> See charts below.

L-TW Impulse repeatability is excellent:








R-TW Impulse repeatability is excellent:








Current delay difference between the L and R channels is excellent (~0.19 ms or ~7 mm).








SPL chart is relatively normal with the exception that the noise level in the lower frequencies is maybe 10dB higher than I would have expected. There is an additional noise disturbance in the 35 Hz range that may be the result of an external noise or possibly it is a noise source within the measuring system. It is very unlikely to be an actual output of the TW. The general downward slope from the low to high frequencies of the noise level is common to many measuring systems. The output through the TW operating range is normal.








Step 2: Confirm delays between the drivers. 
I will detail this next.


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## jtalden (Mar 12, 2009)

Step 2.
General setup for all Step 2 testing:
> Protect/save/record all current driver delay settings so that delay adjustments calculated from this experimentation can be made to them.
[I will need all these current delay settings in order to confirm the analysis and provide the adjustments needed.]
> All XO's = Active
> REW acoustic timing = On 
> All sweeps = 20-20k Hz

Step 2.1. Determine driver delay adjustments needed for Left Channel
> Reference Channel = Right channel
> Measurement channel = Left channel
> Mute all drivers except R-TW and L-TW
> Measure (label as L-TW)
> Mute all drivers except R-TW and L-MR
> Measure (label as L-MR)
> Mute all drivers except R-TW and L-W
> Measure (label as L-W)
> Save and Post these 3 measurements as an mdat file for analysis.

Step 2.2. Determine driver delay adjustments needed for Right Channel
> Reference Channel = Left channel
> Measurement channel = Right channel
> Mute all drivers except L-TW and R-TW
> Measure (label as R-TW)
> Mute all drivers except L-TW and R-MR
> Measure (label as R-MR)
> Mute all drivers except L-TW and R-W
> Measure (label as R-W)
> Save and Post these 3 measurements as an mdat file for analysis.

[Step 3. will set the new calculate delays based on Step 2 and then remeasure using the Step 2 series measurement plan to confirm the final settings. This concludes the XO timing phase of the setup.]

Questions?


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## oliverlim (Jan 1, 2017)

Step 2.1

It seems like the left mid is around 2.5ms slower and the left woofer is around 6ms slower then the right tweeter and left tweeter. 

However, If you look at the group delay for the left channel as a whole, it seems like the FR phase is really good and smooth. So should I disregard the phase response smoothness or just concentrate on the timing.

Thanks! You have been a great help in helping me understand TA and improving my sound.





jtalden said:


> Step 2.
> General setup for all Step 2 testing:
> > Protect/save/record all current driver delay settings so that delay adjustments calculated from this experimentation can be made to them.
> [I will need all these current delay settings in order to confirm the analysis and provide the adjustments needed.]
> ...


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## jtalden (Mar 12, 2009)

I intended that Step 2 be completed in it's entirety before analysis. In this car application I expect that a compromise L Vs R timing alignment may be needed due the disparate geometry. That can't be evaluated though until both channels data are available. I did an analysis of the left channel anyway to determine the best driver timing. This left channel timing may need to be changed a little when the right channel data is available. Without the current driver delays that I requested I can only offer the adjustments needed from the current settings. Since we are only adding delay in this case, this shouldn't be a point of confusion.

*Recommended Delay Adjustments:*

L-TW = *None* [retain current delay and polarity setting]
L-MR = *+0.12 ms, Invert *[increase the delay and invert the polarity]
L-W = *+0.60 ms* [increase the delay and retain the current polarity]

These recommended changes provides the best phase tracking and SPL support possible for this setup.

*Comments:*
The current TW/MR XO is timed very well. It is the 2nd best timing alignment and would perform as well for SPL support and phase tracking. The MR impulse is leading the TW impulse however by approximately 1/2 wavelength. The recommended alignment is the more conventional alignment with the initial rise of the impulse of both the TW and MR being close to the same time. To do that the MR was inverted and delayed by approximately 1/2 wavelength. 

The current MR/W XO timing is also very good; almost ideal. However the relative polarity between the 2 drivers is wrong so they are working against each other causing a significant dip in the SPL response. The recommended setting has the correct relative polarity between the 2 drivers due to the MR being reversed. The delay adjustment on the L-W was already good, but the minor recommended change makes it a little better.

*Selected charts:*

SPL support in the 2 XO ranges.








Comparison of the current SPL response to the recommended settings.








Note, the L-W SPL level was reduced in this analysis for clarity. The phase tracking and effective SPL support will be retained no matter the final driver levels chosen.


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## oliverlim (Jan 1, 2017)

Ok.The whole Step 2. I made some TA adjustment to the Left Mid as per your earlier mail. But ran out of delay for my Left Woofer. I believe then instead of adding .6ms to my left woofer, I should just add .6ms delay to all my other 5 drivers?

This is currently my TA for my 3 way active. Right Hand Drive so driver in on the Right side. 

L-T = 0.67ms
L-M = 0.42ms
L-W = 0ms

R-T = 2.17ms
R-M = 1.67ms
R-W = 0.83ms

I seem to get a worse Group Delay with more spikes with the inverted Mids as you suggested. Could you let me know how you deduced from my measurements that my mids or earlier Tweeter was inverted?


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## jtalden (Mar 12, 2009)

oliverlim said:


> I made some TA adjustment to the Left Mid as per your earlier mail. But ran out of delay for my Left Woofer. I believe then instead of adding .6ms to my left woofer, I should just add .6ms delay to all my other 5 drivers?


No, we would reduce the delay on the other 5 drivers.



> This is currently my TA for my 3 way active.


Thanks for the new current delay settings. I will use these for this analysis.



> Right Hand Drive so driver in on the Right side.


I find it hard to reach over there to operate the steering wheel and peddles. :bigsmile:



> I seem to get a worse Group Delay with more spikes with the inverted Mids as you suggested.


Reversing the polarity of a driver will have no impact on group delay or the number of spikes in its bandpass range. It just shifts the phase by 180°. The driver delay changes will impact the group delay.



> Could you let me know how you deduced from my measurements that my mids or earlier Tweeter was inverted?


By 'invert' in this context I am referring to inverting the current polarity of the Mids from the current polarity. It would have been more clear if I used; 'reverse'. The absolute polarities the drivers that works best to integrate the speaker is depended primarily on the XO filter settings employed. All professionally aligned speakers make this decision based on modeling or measurement of the system. It is very common to have drivers in the same speaker wired with opposite polarities.

The decision as to the best relative driver polarity to use for M vs T XO for instance is based on the phase relationship of the 2 drivers through the XO range. We want the 2 drivers to work together as well as possible at each frequency within the XO range. That provides the best SPL support and the most stable sound lobe at those frequencies (see wiki 'acoustic lobing'). This is best determined by analyzing the phase tracking through the XO range. We want the phase to track as closely as possible through that range. Reversing the phase of one of the drivers and adjusting the relative delay between them are the controlling factors in optimizing phase tracking. 

*This link* shows an example of phase tracking being optimized through the XO range. Your phase tracking will be more confusing to analyze due to all the reflections. I normally post an example of the final alignment after the analysis is completed. The impact on SPL support is an indirect indicator of the phase tracking and an easier chart to understand and hence I provided the 2 charts in Post-32.


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## jtalden (Mar 12, 2009)

I completed the analysis.
The following table shows the adjustments to the current delay settings or both channels. The last column represents the new delay settings.








Right channel SPL support:








Right channel TW and MR phase tracking in the XO range.








The prior left channel charts shown in Post-32 are still valid. 
Like the other car applications I have seen, the heavy reflections make this type of analysis more difficult. In this case I was still able to identify the best timing alignment for the overall system. Given proper EQ to an appropriate house curve this timing should work very well.


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## oliverlim (Jan 1, 2017)

jtalden said:


> I completed the analysis.
> The following table shows the adjustments to the current delay settings or both channels. The last column represents the new delay settings.
> View attachment 138754
> 
> ...



Thanks jtalden! You have been a great help! Imaging did seem to improve up a notch. But the biggest improvement seem to be the bass which is a little more upfront/infront nearer the bonnet then below the dash. I will run the measurements again next week after I install my APL1 for FIR EQ and upload the results here. 

:T:T


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## oliverlim (Jan 1, 2017)

I redid my measurement after eqing and doing a house curve. I reversed my mid compared to my previous measurement to remove a big dip at 250hz. Please let me know if my phase/delay/TA can be improved.

Thanks!


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## jtalden (Mar 12, 2009)

The basic timing looks very good. MR-W XO timing is very good and the MR-TW XO timing is reasonably good also. Small deviation from these settings are not likely to impact the sound quality significantly. Even major changes are not likely to impact the SPL measurements significantly due to the nature of the environment. It is good however to have all the more direct sound arriving an the same time and this timing does that.

Now, you can finishing up the EQ / house curve.

Enjoy!


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## oliverlim (Jan 1, 2017)

jtalden said:


> The basic timing looks very good. MR-W XO timing is very good and the MR-TW XO timing is reasonably good also. Small deviation from these settings are not likely to impact the sound quality significantly. Even major changes are not likely to impact the SPL measurements significantly due to the nature of the environment. It is good however to have all the more direct sound arriving an the same time and this timing does that.
> 
> Now, you can finishing up the EQ / house curve.
> 
> Enjoy!



I am back again. I redid my whole system with new speakers/dsp and amps. Still a 3 way active system in a right hand drive car.

Appreciate any suggestions on my XO settings and TA. Currently I have set the crossovers at 200hz/2.5Khz. I am actually thinking of lowering the mid/woofer crossover to 150hz as there seems to be some strange phase issue around 220-250hz?. Slope is LR24. The noise around 50-60hz is my diesel engine running. I am not able to switch off my engine or my amps/dsp will also auto switch off.


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## oliverlim (Jan 1, 2017)

I will attempt to read the measurements and see if I get the adjustments correct.

Looking at my LT as reference, my RT is -0.10ms so it faster then my LT. Add 0.10ms to the right Tweeter.
For RM it is 0.29ms slower. So add -0.29ms to my RM
For RW, it is 2.94ms slower. So add -2.94ms to the RW.

I am a little confused what to do with the Left side drivers using the RT as reference.


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## jtalden (Mar 12, 2009)

LT Channel

MR-TW XO: is now timed ideally.
W-MR XO: W delay should be increased by 1.44ms to improve the phase tracking and SPL support.

































I will analyze the RT later.


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## jtalden (Mar 12, 2009)

RT Channel [Left Measurement Channel]

MR-TW XO: MR delay should be increased by 0.33ms to improve the phase tracking and SPL support.
W-MR XO: W delay should be increased by 3.09ms to improve the phase tracking and SPL support.

























With the above changes to driver delays, the drivers will hand off smoothly in the XO range. 

The next step is to correctly time the sound arrival of each channel at the LP. To do that, pick either channel as the reference channel. Let's assume your choose the left channel as the reference.
So:
Left channel = Reference
Mic at LP

Measure Right channel
Measure Left channel

View the Impulse overlay chart. If the 2 IRs start at the same time then the delay between channels is correct. If they are offset then adjust the delay of one channel as needed. You can either adjust all 3 drives in one of the channels or adjust an overall channel delay if your have that option in your DSP.


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## oliverlim (Jan 1, 2017)

Thanks a lot jtalden!

I will give it a test and report back. But could I ask how you get the chart for the xo where u calculate the delay difference? 

I spend an hour playing with the overlay, playing with smoothing options, playing wrap and unwrap phase and I could not get anything close to what you have which showed the difference so clearly. It usually shows solid and dotted lines. The impulse chart is especially chaotic.

Also if I do change crossovers and/or volume levels of the individual Drivers, would it change the timings like if I move mid and woofer crossover from 200 to say 150 for both Drivers? 

Thanks again!


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## jtalden (Mar 12, 2009)

oliverlim said:


> ... how you get the chart for the xo where u calculate the delay difference?
> 
> I spend an hour playing with the overlay, playing with smoothing options, playing wrap and unwrap phase and I could not get anything close to what you have which showed the difference so clearly. It usually shows solid and dotted lines. The impulse chart is especially chaotic.


See *Here* for very general tips. Each situation may require different settings however. Car applications are usually very difficult and often impossible to analyze using this method. The LT (right channel) was unusually easy for an car application. The RT (left channel) was very difficult and that is why I did not post the phase tracking charts for that channel. They would look pretty chaotic to most people and be very difficult to explain. This analysis process is much better suited for home setups and XOs above the modal range. In a room, with the mic at 1m from the baffle for closely spaced drivers, the direct sound phase traces are well defined with a wide variety of settings.

I recommend using another simpler method to determine delays for car applications. There are other common methods, but I have no real experience with them. Those with car experience may have suggestions for a method that is simpler and still effective for that application.



> Also if I do change crossovers and/or volume levels of the individual Drivers, would it change the timings like if I move mid and woofer crossover from 200 to say 150 for both Drivers?


The relative volume level of the drivers will not impact the delay timing. EQ filters in the XO range has some impact to phase, but modest filters would not likely have a significant impact. The change in XO frequency may be significant particularly in the modal frequency range. I have no way to know how just significant it may be in this case. It would be easy enough for you to determine that. Just make the change and run the same set of measurements of the individual drivers. Also measure each channel with all drivers active and create the same SPL overlay chart that I posted above. If there is still good SPL support in the XO ranges then all is good. If the SPL support disappears then there may be a better timing. There is no assurance that different timing will help however as the modes/reflections at that XO frequency range may be more problematic.


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## oliverlim (Jan 1, 2017)

I made the timing adjustments and remeasured the individual drivers. I tried the full left and full right measurement but the IR is just too chaotic to understand. I forgot to save that measurement though.

Could you help me check if my TA is now good other then the left and right full channel TA? Thanks again!

I tried using holmimpulse and it does seem easier to see the IR. It showed 11cm difference. But I think I made the adjustment in the wrong direction. Will recheck and move it back 11cm and a additional 11cm in the other direction which sounds about right when I listened to some vocals. 

I tried playing with the phase overlays again. I thought phase only goes to +-180 or 360 degrees? I seem to see that it goes to over 700-900 on mine.

https://drive.google.com/open?id=1QGB9RZpaYjn06JKMVF3rhJOBte6ZH12o


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## jtalden (Mar 12, 2009)

Something went wrong here.
The timing (IR locations) do not agree with my analysis. The relative IR locations should be the same as in my analysis.

Is the mic close to the same location that was used for my analysis? [A small difference probably explains the small timing error I see in the upper XOs. That timing error is small and easily due to a mic location change. The lower XO appears wrong as well and it should not be as sensitive to a small mic position difference.]
Did you make the changes I suggested to your previous settings? [My recommendations were for adjustments to current settings not absolute settings.]
Am I still mixed up on the measurement channel verses reference channel as I was before? [I finally thought I had properly followed your method of labeling measurements.]
Did you make the changes in the correct direction using ms?

I think we already confirmed that the acoustic timing is working properly and "wait for timing reference' is applied. 

Try to get the full channel measurements working and confirm if there is SPL support in the lower XO range.

If you are sure there are no errors in this recent data and the previous data was in error, I suppose I can analyze this new data to determine new delay changes for the lower XOs.


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## oliverlim (Jan 1, 2017)

Hmm. Only thing I changed in REW was to calibrate the SPL levels. I also made the changes the the timing on a per driver level as per your recommendations. I did need to recalculate the levels as my LW was already at zero so needed to make changes to all the other 5 drivers instead. The position is almost exactly the same as my seat is in a memory and I use a velcro strap around the head rest so the position of the mic cant have been so different. Let me do another 6 test and upload it so that you can have a quick look at both this current and the next data to see if it has yet any changes. 

Here is some more data.

My previous TA settings before applying your recommendations. all in ms

LT - 2.75
LM - 2.17
LW - 0

RT - 4.17
RM - 3.83
RW - 1.58


After applying your recommendations

LT - 1.31
LM - 0.73
LW - 0

RT - 2.73
RM - 2.72
RW - 3.23

I hope I did not misunderstand your recommendations and applied it wrongly.


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## jtalden (Mar 12, 2009)

There is a issue with the delays. I put together the following table to check the delays and found different values. Does this table look correct to you? 

The delays I recommended for the testing (for Post 45) are shown in the next-to-last column. The numbers actually used are shown in the last column.


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## oliverlim (Jan 1, 2017)

You are right ! I did make a mess
Of the TA adjustments. I did not take
Into account of that your adjustments changed the nearest speaker from the LW to the LM. Do my adjustment was a mess. Which explained the staging mess I heard. I tried out your recommendation and the staging is definitely in place now. Tonality also sounds better. I will post up the new measurements later when I get a change to setup my test gear! U rock!


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## oliverlim (Jan 1, 2017)

Sorry Jtalden. I think I have have made some mistake in switching the DSP to mute the correct drivers in my last measurement.

The latest TA has centered the image as i think the tweeter/mids are pretty close. The woofer seems to be off. I tested 3-4 times on each tweeter measurement to ensure they are reliable. Each of the drivers, I also test a couple of times to see if the next measurement was close and I looked at the DSP to ensure I muted the correct one. This is the latest measurement after using your latest 2nd last column values. I also did one each of full left and right channel with the opposite tweeter as reference.


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## jtalden (Mar 12, 2009)

I calculated the delay changes needed in this last set of measurements to get the best compromise alignment .

LT = 0 (ref)
LM = +0.07 ms
LW = -0.55 ms

RT = 0 (ref)
RM = 0
RW = 0

With the asymmetric LP location and irregular driver spacing of the Left vs the Right side there are significant tradeoffs. This application is cleaner than most however. The actual SPL support in the XO ranges is not much improved from other settings.

The last delay timing effort is to measure using these new settings the full Left channel vs the full Right channel. The same Reference channel must be used for both measurements.

For instance:

Measure Left channel using left channel as reference
Measure Right channel using left channel as reference

From this we can determine is any delay adjustment is needed to center the staging.

Per my analysis, the calculated response for the 2 channels both separately and together (with ideal timing) is attached.

View attachment jta L vs R Calc.mdat


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## oliverlim (Jan 1, 2017)

Does my TA calculation look correct?


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## jtalden (Mar 12, 2009)

Yes


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## oliverlim (Jan 1, 2017)

Did the Full left and Full Right with reference as requested. 

Hopefully everything is in order.


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## jtalden (Mar 12, 2009)

It looks like the Left Channel Reference measurements provided a better Reference than the right so I use the those 2 measurements for the analysis.

To achieve the ideal Left Vs Right timing the Right should be delayed and additional 0.016 ms. That is very close, about 0.2 inches so you already have it dialed in correctly.

Below shows how I determined that. 

The L, R impulse locations as found:








Impulse locations after manually offsetting (delaying) the right Impulse by 0.016ms:








The resulting phase tracking of the Left and Right channels with the 0.016ms delay:


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