# tutorial for good Time Alignement, Group Delay and Phase



## THX-UltraII

For the last few weeks I have learned a lot on this forum about 'subwoofer distance tweaking' and 'timing alignement'. Kudos goes to Jtalden (john) for this!! I have made a simple 'tutorial' for myself (and others) I would like to share. Of course I m open for improvement and maybe there are things that are not correct in the tutorial so please let me know. Together we know more!


*1.*
The first things that you need to do is set the perfect *time alignement* for all your main speakers (FR, FL, CC, SR and SL) . You can do this with a quite simple process. For this process you will need REW and a calibrated mic. (like the Cross Spectrum Calibrated ECM8000). Also, for the entire measuring process you need to set up REW for loopback timing reference (check REW help file how to do this).

*a. *
First thing that you need to do is set a reference distance for all main channels. You can let Audyssey do this or tape measure your speakers (remember to measure to the exact LP at ear height).
*b.*
After this you will have to check the IR peaks for all the main channels (not the subwoofer yet!) in REW by doing measurements with REW for all 5 main speakers separate. (If you measured correct the IR peaks will fall close to each other already). You can take you center channel as reference' and fine tune the distance settings of your FR, FL, SR and SL until the IR peaks fall the closest to each other (depeding on the limitations of the distance increments in your AVR it will likely not be possible to let them fall 100% (0ms) on top of each other but look for the best result. 
*c.*
First make a measurement of the CC+SUB with the distance Auddysey (or tape measured) measured for your subwoofer. Look at the IR overlay in REW. The subwoofer and CC IR peaks will be pretty close to each other already. Change the subwoofer distance untill the IR peaks in the REW overlay panel fall as close on top of each other as possible. 

Do this procedure for the rest of your main speakers also and write down all the 5 subwoofer distances where the IR peaks of the main channels+subwoofer fall on top off each other best. We will need them later.

It should look something like this if you did it right:










You now have all 5 main channels perfectly time aligned. Remeber that from this point on you DO NOT change the distance settings of your main speakers at all anymore!

The problem is that we still dont know how the phase acts at this moment. We do know that with this good time alignement we now have the Group Deplay will be at it s best.

*3.*
Next we are going to see how the phase acts per main channel+subwoofer. You can follow the instructions in the .doc in post 1 of this thread for this but in short:
*a.*
First make a measurement with the distances you found with the IR time alignement process you did in step 2. Look at the SPL overlay in REW. Change the subwoofer distance untill the SPL overlay graph in the Xover range looks best (highest SPL output with least dips).
*b.*
Compare this distance with the distance you measured before (with the perfect time alignement). If they are close to each other you are lucky and can take the average of both of them. It is also possible (like in my setup) that there a quite a big difference between them. You will then have to make a choice what you want: take the time aligned measurement length (so you will have perfect time alignment and Group Delay) or take the subwoofer distance which results in an good phase (you sacrifice time alignement and Group Delay).
*c.*
Do this for all main channels+subwoofer seprate too.


I think that if you want a compromise between time alignemet, group delay and phase for you total 5.1 speakers set you will have to average all subwoofer distances you found in step 2 and step 3 (this will be the average of 10 distances if you did everything correct).


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## Barleywater

Addendum: Preferences and soundcard need to be set up for loopback timing reference.


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## chinni123

THX-UltraII said:


> For the last few weeks I have learned a lot on this forum about 'subwoofer distance tweaking' and 'timing alignement'. Kudos goes to Jtalden (john) for this!! I have made a simple 'tutorial' for myself (and others) I would like to share. Of course I m open for improvement and maybe there are things that are not correct in the tutorial so please let me know. Together we know more!


Thanks for taking time to provide all the steps. I am still digesting. If you don't mind can you post with .mdat of final resulat as attachment. It will help to look at the graphs as base line.


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## THX-UltraII

Barleywater said:


> Addendum: Preferences and soundcard need to be set up for loopback timing reference.


thxz. Edited first post.


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## THX-UltraII

chinni123 said:


> Thanks for taking time to provide all the steps. I am still digesting. If you don't mind can you post with .mdat of final resulat as attachment. It will help to look at the graphs as base line.


I bought a new processor and need to re-measure everything. I ll post graphs and .mdats as soon as possible


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## THX-UltraII

Despite that I made this tutorial I still have some some questions myself too about this.

I did some new measurements last night with my new processor (Onkyo TX-NR876 with Audyssey MultEQ XT). I measured all my speakers with Audyssey and after this checked the IR peaks with REW for the 5 main speakers (FR, FL, CC, SR and SL). The IR peaks fall pretty close to each other so there s no need to adjust this any further (this assumes that Audyssey does a good job for setting the delays). After this I started measuring all the separate main speakers+subwoofer. I m already 'stuck' with my second measurement. To be more specific:

I first measured the FR+SUB with REW with the distances that Audyssey measured. There where some big dips at the XO frequency range. Like I said in my 'tutorial' a few posts back you only want to adjust the subwoofer distance to maintain proper time alignement for all 5 main speakers (FR, FL, CC, SR and SL). So I adjusted the subwoofer distance to a point where the SPL output in the OX range was best (highest SPL and least dips). I had to change the subwoofer distance from 3.60m (what Audyssey measured) to 6.15m to get the best SPL in the XO range (this proves that the Audyssey measurement is not utilized to determine or check the integration of the speakers at the critical crossover frequency. Audyssey focuses on response and time domain correction for each speaker in isolation; it does not measure the combined response of the subwoofer and main speakers together). With the subwoofer @6.15m my FR+SUB measurement gives me a pretty nice/flat SPL response.

Next thing I did was measuring the next main channel. The order of doing all the main speakers does not matter; I chose the CC. As expected the CC showed a pretty bad SPL response at the XO range with the 3.60m subwoofer distance that Audyssey measured (I had my subwoofer distance set back on it s default 3.60m that Audyssey measured). I was hopinh that a [email protected] measurement would give me the best SPL reponse. Of course this 6.15m was already much better than the [email protected] but I noticed that there was room for further improvement in the CC+SUB SPL response. With some trail and error measurements I finally found the best subwoofer distance setting for the CC+SUB which is 7.05m. This is a pretty big difference with the best subwoofer distance for the FR+SUB which is 6.15m. Before going further with measuring the FL+SUB, SR+SUB and SL+SUB I want to know what will I need to do with this information. I checked the [email protected] (best CC+SUB distance) but the SPL response is much worse then [email protected] 
With this information I can draw a few different conclusions/possibilities which I like to discuss with the REW guru's here (Barleywater, JohnM, Jtalden etc ):

*1.*
IF my speakers where only the FR, CC and SUB in my system (this is only theoretically to make it easier to explain) the best thing I could do is choose 6.60m (average of 7.05m and 6.15m) for the subwoofer distance to achieve the best compromise.
*2.*
IF my speakers where only the FR, CC and SUB in my system (this is only theoretically to make it easier to explain) the best thing I could do is choose 7.05m for the subwoofer distance because a correct phase between the CC and SUB is most important for movies to get the best dialog sound representation.
*3.*
IF my speakers where only the FR, CC and SUB in my system (this is only theoretically to make it easier to explain) the best thing I could do is choose 6.15m for the subwoofer distance because a correct phase between the SR and SUB is most important for movies to get the best overall movie sound representation.
*4.*
In orde to achieve the best SPL response for both SR+SUB and CC+SUB I could stick with a fixed subwoofer distance of 6.15m, choose the default FR distance that Audyssey set (which results in best SPL for FR+SUB) and CHANGE the distance setting of the CC (so leave the subwoofer distance @6.15m). This would mean that I m changing the distances of the main speakers after the Audyssey calibration. This would mean the best SPL response for both FR+SUB and CC+SUB but losing time alignment between FR and CC. 
EDIT: The big question with this method is how much time difference in ms is reasonable. Someone said that max. 5ms is reasonable. 5ms is approx. 171.5cm (assuming the speed of sound is 343 m/s) so this would mean there is quite some room to adjust all the main speaker distances. But others say that you don t want to change the distances for the main speakers at all......

What are the best things to do...... :scratch::scratch:


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## Barleywater

For all the science, and all the engineering, in the end much of the sound stage remains an illusion within the mind. Sound mixing and engineering is human driven, and occurs in diversity of studio setups, all involving human interpretations. Compromise must happen at every step of the way. In the end, if most music and soundtracks you listen to bring enjoyment, that's all that really matters. It is really still about the message, not the messenger.

In perfect surround sound set up all speakers are exact same distance from single sweet spot listening position. If sub is only element off of circle, and is crossed at frequency below that for room's single mode behavior (pressurization only mode), then a single delay setting works. As more speakers diverge from circle, and sound at frequencies with directional characteristics are involved, then one perfect solution does not exist, but many possible partial (compromise) solutions do. 

Don't let knowledge of real physics destroy enjoyment in listening.

Since primary focus in movies is concentrating on screen, and for most music focus is concentrated on grouped performers being watched, setup should be focused on front speakers. As long as front speaker direct sound arrives several milliseconds before first reflections, and arrives before correlated sounds from other speakers (rears, sides), the mind will assign direction of sound based on cues from front speakers and sound appears in front. Once this is achieved, gross defects in low frequency behavior are addressed with phasing and delay tweaks (with lots of compromise), room treatment, (typically compromise in added expense, and potential aesthetic impact), and finally equalization, for which various limits (compromise) also exist, but has greatest flexibility in quickly controlling perceptions about listening space and controlling perceived defects of particularly disturbing source material.

Sometimes reading is more enjoyable than watching and listening. :bigsmile:

Regards,

Andrew


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## THX-UltraII

thxz for your reply Andrew. I know I should enjoy it but would you please give your (technical) opinion and reaction on my 4 conclusions? That s the last thing I m asking from you :R


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## jtalden

THX-UltraII said:


> What are the best things to do...... :scratch::scratch:


Whatever you want! 
You are laboring under the idea that there is a “best” alignment.

As I have stated there are several good solutions and those are not the same for all situations or people. You now have a reasonably good understanding and are starting to see this.

Regarding timing alignment choices: 
Do the choices affect the sound; are they important? 
I find more difference than I would expect, but 90% of my experience is with significantly higher order XO filters than the AVR provides. Possibly I would not find the difference using only the standard AVR SW XO filters. This is why I suggested you check it out for yourself and pick the one you prefer. Based only on my limited experience I suspect that most would to prefer (in order):
1. Reduce the SW delay by 1/2 WL. [by moving the SW distance to a larger number and inverting the SW polarity.] 
2. Initial rise of SW and main IRs aligned. [SW and MR drivers must be the same polarity. This will provide a smoothly changing GD and phase through the XO handoff.]
3. Increase the SW delay by 1/2 WL. [by moving the SW distance to a smaller number number and inverting the SW polarity.] 

Regarding “1.”, the reduced SW delay will flatten the GD in the lower freqs and bring the GD more in line with the high frequencies. The tradeoff is that GD and phase in the XO range is no longer smoothly changing. The phase at the XO point will still be the same, but the SW phase will be crossing the main phase at an angle making the phase at surrounding frequencies diverging. I am not sure that others will hear the difference or have the same impression of which is better. Most of my setups use significantly higher slope XO filters than the conventional AVR handoff. That may make a significant difference in the audibility of the differences. My SW delay is currently reduced a full WL because with the steep XO filters, that is what is needed to bring the GD in line through the entire frequency range except for the narrow XO region.

Regarding SPL EQ concerns:
[Assuming acoustic treatments speaker and LP locations have been fixed.]
> The most important aspect of the 20-200 range is a smooth SPL response and that should be the overwhelming criteria. 
> If the phase is unfavorable at some point in the XO range it is less effective to EQ a dip at that point.
> It’s fine to EQ as needed within reason. Very larger EQ magnitudes are best avoided for various reasons.

Now let’s take your situation as an example:
> Audyssey aligned the main speaker IR distances effectively as expected. 
> It appears Audyssey aligned the SW IR to the mains to approach alignment “2.” but did not provide you a warning to reverse the polarity.
[Your “2.” continuous handoff would be achieved by inverting the polarity of the SW (or the 5 mains). 
Note that, your MR drivers are inverted relative to the TW and SW and therefore in an anechoic environment the polarity is 180 deg out of phase when the IRs are aligned as Audyssey provided. In a room, the room modes play havoc anyway, so you never know the situation until you measure.]
> There was a significant dip in the SPL response from 50-90 Hz for the SW+FR main speaker. This dip did not center itself at the XO freq of 80 Hz. Again this is the effect of room modes. The dip was large enough that EQ boost and cuts would likely be larger than desired. [Maybe not, but we didn’t try.]
> With some adjustment to the timing/phase we aligned the phase near 65 Hz instead of the 80 Hz XO setting and were able to reduce the dip prior to EQ. Since now it is in phase there, it will also respond better to EQ.
> Looking at your other main speakers you found that there are different timing decisions that would be made for each speaker. 

That brings us back to your initial question about what timing to select. The short answer is:
First choose which overall alignment range you want to use; either 1, 2 or 3. Then adjust as little as possible from that alignment to compromise for the SPL differences between the other main channels. Keep in mind that if the EQ is effective in smoothing the response in through the XO with reasonable boosts and cuts then that timing is good. 

Again:
Any timing where EQ can be effectively implemented to is okay. I see lots of SPL curves on this forum that suggest that the timing adjustment is unfortunate. Yours would have been one of those if you had accepted the AVR’s automated setting.


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## THX-UltraII

I ll come back on your extensive reply tomorrow John. Here s a lot of interesting new measurements I did tonight:


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## THX-UltraII

and the last one and a link to the .mdat file:

http://www.sendspace.com/file/4kstmp


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## jtalden

THX-UltraII said:


> *4.*
> In orde to achieve the best SPL response for both SR+SUB and CC+SUB I could stick with a fixed subwoofer distance of 6.15m, choose the default FR distance that Audyssey set (which results in best SPL for FR+SUB) and CHANGE the distance setting of the CC (so leave the subwoofer distance @6.15m). This would mean that I m changing the distances of the main speakers after the Audyssey calibration. This would mean the best SPL response for both FR+SUB and CC+SUB but losing time alignement between FR and CC.
> EDIT: The big question with this method is how much time difference in ms is reasonable. Someone said that max. 5ms is reasonable. 5ms is approx. 171.5cm (assuming the speed of sound is 343 m/s) so this would mean there is quite some room to adjust all the main speaker distances. But others say that you don t want to change the distances for the main speakers at all......


This is a bad idea. To retain a good stereo image and low comb filtering the FR and FL IRs need to well aligned. I am sure this is true for 5.1 program as well.

By the way, 5 ms is about 1720 mm not 172 mm. So 5 ms is way to large a distance error to tolerate. Possibly 0.5 ms was intended and that would work for SW timing error, but again not recommended for the mains.


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## THX-UltraII

jtalden said:


> This is a bad idea. To retain a good stereo image and low comb filtering the FR and FL IRs need to well aligned. I am sure this is true for 5.1 program as well.
> 
> By the way, 5 ms is about 1720 mm not 172 mm. So 5 ms is way to large a distance error to tolerate. Possibly 0.5 ms was intended and that would work for SW timing error, but again not recommended for the mains.


Check my post again: I was saying the same: 5ms is 1.72cm. 

So you are saying that 0.5ms (17.5cm = approx. one increment in my Onkyo AVR) is the maximum change one want to make for the main speakers?


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## THX-UltraII

The measurements I did last night (posts #10 and #11) gave me some interesting information to think about and which raises new questions:

- When looking at Graph 3+5 (pic9 in post#10 or check the .mdat I posted) you can clearly see that curve3 is better than curve5. Curve3 is what Audyssey measured and curve6 is also what Audyssey measured but with the subwoofer distance changed to 6.15m. Although Audyssey is not utilized to determine or check the integration of the speakers he got it right on spot with curve3. I tried the subwoofer @distance settings 3.45 (-15) and 3.75 (+15) but 3.60 gives the best SPL. I think that it is most optimal not by accidence: my subwoofer stands next to my FL speaker which was measured here.
*But *.....we you look at Graph 4+6, which are measurements without Audessey (pic10 in post#10 or check the .mdat I posted) curve6 is the better one. So now the sub @6.15m is the better one :scratch:
What going on here John?


- My next questions concern some Audyssey specific questions:
When you look at the first 2 pictures in post#10 you see the FL with and without Audyssey. Besides the peak at 115Hz is looks to me that the no-audyssey curve (pic2) is much flatter then the curve with audyssey. Especially the [email protected] is the one I don t understand why Audyssey did this. And what about the roll-off from 7-20Khz which is done by Audyssey?


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## Barleywater

To get better understanding of Audyssey you should run it, and then measure line outs from AVR. 
Audyssey is room correction software. It is calculating speaker distances, but also generating correction EQ that is not simply several bands of parametric EQ such as REW EQ. Additionally Audyssey is correcting for target that is likely THX curve, not flat.

At some point you've got do do some critical and extended listening to music and movie sound tracks using the various different strategies you've come up with, as well the Audyssey corrected system.


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## jtalden

THX-UltraII said:


> Check my post again: I was saying the same: 5ms is 1.72cm.
> 
> So you are saying that 0.5ms (17.5cm = approx. one increment in my Onkyo AVR) is the maximum change one want to make for the main speakers?


Sorry - about my erronous and confusing post. I'll try again.

Re. Manual EQ starting point:
> A 5 ms (1.75 m or 144 deg at 80 Hz) timing error for the SW to mains is way too much in my opinion. Possibly that is because I see no need to set it that far off. Why would we want to do that? I would expect it to lead to a large dip in the XO range and then tax the ability to EQ that region. The larger the EQ magnitude the larger the reduction in headroom as Wayne has often pointed out.
> A 0.5 ms (175 mm) is okay for the SW to Mains and would not expect it to be an issue.
> A 0.5 ms (175 mm) is also okay for the mains timing error. My recommendation has been to adjust it as closely as the AVR allows. We are not likely to always sit with our head exactly at the mic LP position anyway. I have seen more than a few people who indicate they are are very sensitive to any shift in head position. They are apparently are very sensitive the HF comb filtering.


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## THX-UltraII

jtalden said:


> Sorry - about my erronous and confusing post. I'll try again.
> 
> Re. Manual EQ starting point:
> > A 5 ms (1.75 m or 144 deg at 80 Hz) timing error for the SW to mains is way too much in my opinion. Possibly that is because I see no need to set it that far off. Why would we want to do that? I would expect it to lead to a large dip in the XO range and then tax the ability to EQ that region. The larger the EQ magnitude the larger the reduction in headroom as Wayne has often pointed out.
> > A 0.5 ms (175 mm) is okay for the SW to Mains and would not expect it to be an issue.
> > A 0.5 ms (175 mm) is also okay for the mains timing error. My recommendation has been to adjust it as closely as the AVR allows. We are not likely to always sit with our head exactly at the mic LP position anyway. I have seen more than a few people who indicate they are are very sensitive to any shift in head position. They are apparently are very sensitive the HF comb filtering.


I forgot because our other thread has become so long so how do I check the subwoofer/main timing? I know how to do it with the main speakers (IR peak as close as possible to each other but the subwoofer does not have a IR peak like a main speaker does.

EDIT:
let s take this measurement: does this mean that the sub has a delay of approx 25!! ms? Or am I not reading it correct?


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## jtalden

THX-UltraII said:


> The measurements I did last night (posts #10 and #11) gave me some interesting information to think about and which raises new questions:
> 
> - When looking at Graph 3+5 (pic9 in post#10 or check the .mdat I posted) you can clearly see that curve3 is better than curve5. Curve3 is what Audyssey measured and curve6 is also what Audyssey measured but with the subwoofer distance changed to 6.15m. Although Audyssey is not utilized to determine or check the integration of the speakers he got it right on spot with curve3. I tried the subwoofer @distance settings 3.45 (-15) and 3.75 (+15) but 3.60 gives the best SPL. I think that it is most optimal not by accidence: my subwoofer stands next to my FL speaker which was measured here.
> *But *.....we you look at Graph 4+6, which are measurements without Audessey (pic10 in post#10 or check the .mdat I posted) curve6 is the better one. So now the sub @6.15m is the better one :scratch:
> What going on here John?


If Audyssey; sets the IR timing, then calculates the expected response, and then calculates EQs to adjust that calculated response to their target SPL curve, we would expect the resulting SPL to follow their target curve. It did very well in this case. If we then change the SW-main timing 1/2 WL without inverting the SW polarity we should expect that the SPL will be adversely affected – it was. 

Audyssey found one solution to time the SW-main handoff and then EQed the SPL accordingly. That is not the only solution or necessarily the “best” one. When we did it manually we chose an alternate SW-main timing that would ease the EQ burden we were planning to do manually. That is another solution. It is not necessarily the “best” either. 

If you want to manually EQ on top of Audyssey then it would be better to leave the SW timing the same as Audyssey set. Audyssey has already EQ to address the SPL for those settings.

You may still be able to evaluate the alternate SW-main timing however if you like. I’m referring to the one where there the SW distance is increased 1/2 WL and the polarity is also reversed. I think it should work out okay, but it is not completely clear to me that the Audyssey EQ will be compatible with that. You would need to measure to confirm the SPL response is still similar. 



> - My next questions concern some Audyssey specific questions:
> When you look at the first 2 pictures in post#10 you see the FL with and without Audyssey. Besides the peak at 115Hz is looks to me that the no-audyssey curve (pic2) is much flatter then the curve with audyssey. Especially the [email protected] is the one I don t understand why Audyssey did this. And what about the roll-off from 7-20Khz which is done by Audyssey?


Audyssey has properly EQ to their target curve. The 3 dB dip at 2k and the roll-off is part of the target. Check out the Audyssey website and the Audyssey forum. Also look up info here and elsewhere regarding "X curve" and "House Curves".


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## THX-UltraII

thxz John, completely understand your reply! (YES!!!!! )

Can you also come back on my post #17 involving IR timing of sub+main channel?


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## jtalden

THX-UltraII said:


> I forgot because our other thread has become so long so how do I check the subwoofer/main timing? I know how to do it with the main speakers (IR peak as close as possible to each other but the subwoofer does not have a IR peak like a main speaker does.
> 
> EDIT:
> let s take this measurement: does this mean that the sub has a delay of approx 25!! ms? Or am I not reading it correct?


You are not reading it correctly. Also, your first post is not clear to me and some of that is related to your question here. In the first post you have us first align all the main channels in 1,a and 1,b. That’s Okay. From there on it gets confusing to me.

So I will to try to clarify some of my intent and you can rewrite the first post if you like.

After 1,a and 1,b:
> Tape measure the SW distance and enter it into the AVR if the AVR has not already assigned a similar distance. 

> Choose a main speaker to align the SW with. (I suggested either FR or FL and in your work you first used the FR. You now recommend the CC. That’s fine – We can use the CC. 

> Sweep measure the SW and look at the IR overlay of the SW and the CC. The initial rise of the SW and CC IR traces should be reasonably aligned. The idealized starting point is shown as Per Post 140 Fig3a in the other thread and is shown again below. This is just the starting point however and a 1 or 2 ms discrepancy is not important as we are just making sure that we are in a reasonable range to start to optimize the timing. This starting alignment can be just per the tape measurements. 









> We expect to able to find 3 good SW timings/distances that will provide good SPL fill and provide a good setting to use for the EQ setup. We only need to only actually find and optimize the one are actually interested in using. 

> We will expect to find the “reference setting” for SW distance near the starting point and the other two 1/2 WL away in each direction. We need to know that whatever the SW polarity is needed for the reference setting it will the opposite polarity that is needed to find the other two.

> To find one of the settings adjust the SW distance in approximately 0.5 m increments in either direction and at each increment measure and look at the SPL of the SW+CC reference channel. If we find maximum SPL fill at, or close to the starting distance, maybe 1 or 2 increments away, we have found the “reference setting”

> If we don’t get maximum SPL fill close to the starting point and instead find maximum SPL fill several increments away (approximately 1/2 WL in both directions) that is an indication that the first “reference alignment” was not found because the SW (or all the mains) would need the polarity reversed to find that one. Either way, we now have a rough idea where all 3 of these timing alignments are located. 

> We know the “reference alignment” is the one that provides the smoothest/continuous phase and GD handoff throughout the XO range. We also know the one with the SW distance increased 1/2 WL will tend to reduce the overall phase rotation and GD. We also know all of these 3 will provide good SPL fill and it will be relatively easy to EQ thus retaining as much of the headroom as possible.

> We can now choose the alignment we want to actually use and then set the SW polarity and timing/distance for it. We can just use the 0.5 m increments or fine tune it with smaller increments – whatever the AVR will allow. You will find that fine tuning it has no big impact on the result and is not really needed. 

> After finding the solution for the SW+CC the only thing needed is to confirm that this same SW timing works for the FL and FR. This is done just by looking at the SW+FL and SW+FR SPL traces to assure they have no major issues regarding SPL dips that will make EQ difficult. [There is no need to fine tune the SW distances for those channels.] 

> If there is an issue with the FL or FR when using the SW setting we found for the CC we can experiment to determine if there is a better SW setting to meet the needs of those channels. It is not unusual or problematic to find and use a compromise setting. It not always necessary either. In the end we just want the SW EQ to work reasonably well with them. 

I hope this helps.

Also:
If you are updating the first post I think it is worthwhile to include upfront comments that it is much easier to align the SW-main timing/distance using the RTA feature and doing it real time. This method is not the easiest way to get good results. There is significant work here and most people are not looking for that. I only mentioned this method as an option for those that want a better understanding of what is going on. It also provides some confidence in the alignment as it provides some understanding of the tradeoffs.


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## THX-UltraII

Thanks for your clarification John. Before I ll update my first post:
Am I correct that I can also do the following after my steps 1a and 1b(just asking to see if I understand now):

1. Take the 'Audyssey measurement' (which will correspond with tape measuring) for the subwoofer distance.
2. Check the IR peaks of the CC and SUB and note it.
3. Check the SPL curve of the Xover range and note it.
4. Set the subwoofer distance so that the initial peaks of the CC+SUB fall within max. 0.5ms from each other.
5. Check and make sure that with the SPL of the Xover range does not differ too much from the one note in step3.


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## jtalden

THX-UltraII said:


> 1. Take the 'Audyssey measurement' (which will correspond with tape measuring) for the subwoofer distance.


I’m not sure I understand the question. Steps 1a and 1b are either AVR automated distances or tape measured distances for the initial speaker distance starting points. I was assuming AVR automated EQ systems would then be turned off and not used after that.

The process was written up for those that want to manually EQ. It was not written with the intent of using an automated EQ process. It was only an observation that, if the speaker distances were automatically set by the AVR automated system, then the values are probably a good starting point for the manual process process. The idea here was to adjust the distances manually using the IR for the main speakers and then use the process here for the SW-main timing. There are other manual processes that can be used for SW-main timing also. It was only an observation that Audyssey settings are probably a good starting point at least for the mains and some may want to start with those numbers rather than using a tape measure. 



> 2. Check the IR peaks of the CC and SUB and note it.


Yes, adjust the SW distance if needed to bring the initial IR rise near CC IR rise. They should be okay already with the distance settings above. Note that it is not the "peak" of the SW and main IR’s that are being aligned; it's the "initial rise" of the IRs as per the graph Fig3a as shown in Post 20. The SW IR "peaks" may be delayed significantly.



> 3. Check the SPL curve of the Xover range and note it.


Yes, but adjust the SW distance as needed to maximize the SPL. I just suggested doing this using a convenient distance increment.



> 4. Set the subwoofer distance so that the initial peaks of the CC+SUB fall within max. 0.5ms from each other.


?? No. We have now adjusted the CC+SW to the maximum SPL fill. If the IR are still aligned within 2-3 ms of the starting position then we have found the "reference alignment". If the IRs are now offset from the initial by more than that we have located the +1/2 WL or the -1/2 WL alignment. If you didn’t find the alignment you wanted to target (Reference alignment/+1/2 WL/-1/2 WL) then make the needed adjustment to find the one you want.



> 5. Check and make sure that with the SPL of the Xover range does not differ too much from the one note in step3.


?? No, time now to just confirm that that same timing for the CC+SW also works okay for the SPL of the other front mains.

--------------------

Sorry I couldn’t really follow your write-up very well. That doesn’t necessarily mean it is all wrong. Understanding someone else’s directions is often difficult for me. I have trouble writing up and following my own processes sometimes. I did my best in posts 140 and 193 of the other thread: 
http://www.hometheatershack.com/forums/rew-forum/59784-first-measurement-14.html

If you don’t understand the Fig3a, b, c, d charts in Post 140 then there is still work to do to have a full understanding. 

They Show: 
> Fig3a is the Audyssey Starting point for SW-FR distances. [It is close to the distances needed for the “Reference Alignment”, but note that a minor distance adjustment was made and the SW needed to be inverted to find that “Reference Alignment”.]
> Fig3b is the “-1/2 WL alignment” 
> Fig3c is the “+1/2 WL alignment” 
> Fig3d is the “Reference Alignment”


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## THX-UltraII

I think I m missing something here. I thought you said in an earlier posting that the max. difference for time alignement is approx. 0.5ms. So the goal is ALWAYS to have to initial peaks of the CC and SUB to be max 0.5 ms correct? That why I wrote point 4 in post #21.


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## jtalden

THX-UltraII said:


> I think I m missing something here. I thought you said in an earlier posting that the max. difference for time alignement is approx. 0.5ms. So the goal is ALWAYS to have to initial peaks of the CC and SUB to be max 0.5 ms correct? That why I wrote point 4 in post #21.


Regarding Initial SW-CC timing:
I just reread Post 16 and see how badly I confused this issue - again. It is still very misleading even though I was trying to clarify it. I never should have said the initial starting point should be that close. A physical tape measurement should be a fine initial starting point. I must have mixed up the initial IR setting recommendation with final tuning recommendations. Even if I was thinking of the final adjustment, 0.5 ms is closer than necessary for good results for the SW-CC timing. [I may have mixed up that I recommended increments of 0.5 *m* as reasonable search increments sizes and that is also okay for the final alignment, not 0.5 *ms*.]

> For the initial starting point we just want to be in the ballpark to reduce the search time. We want the IRs to roughly resemble Fig3a so that we expect to find the actual Reference Alignment close by. Then we know where the other 2 alignments are likely to be. 

> Once we have identified the regions of 3 alignments we can then start to fine tune to the one we have chosen for our target alignment. [The initial settings are no longer of interest to us.]


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## THX-UltraII

I think that I understand you but here s my point:

I HAVE to do the Audyssey measurement first because only the auto-audyssey calibration process does a subwoofer equalization. I have to say that Audyssey (XT version which I have) does a perfect job in EQ-ing the subwoofer curve (check the 7th and 8th picture in post #10 of this thread, pic7 is the subwoofer without Audyssey and pic8 is after auto-audyssey calibration). Also the equalization of all the 5 main speakers is nicely done by Audyssey so also here it is not needed to do a manual EQ-ing. It is even not possible to do a manual EQ-ing of the 5 main speakers because when you do this you lose the subwoofers Audyssey EQ. I have also confirmed that the time alignement for all the 5 main speakers is correctly done by Audyssey. All the rest of my AVR settings are done also 100% perfect now (speakers settings, XO freq. etc).

So the ONLY thing that I must make changes to is the SUBWOOFER DISTANCE. I already checked what happens when I change the subwoofer distance from its Audyssey measurement 3.60m bother all other values other then 3.60m (including a small difference like 3.45m and 3.75m) does give a LESS smoother SPL curve then picture3 in post#10.

So I THINK! (not sure) that I m just using to best possible settings with the settings that Audyssey found. I just need your confirmation on this.


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## jtalden

Okay, it sounds like you are all set.
You have used REW to measure the SPL of the Audyssey XT results and confirmed that Audyssey did its job in all respects to meet the Audyssey House curve. You are all set with that setup. Enjoy!

--------------

We also now know there is also another SW distance setting that should result in a very similar SPL response, but result in less GD for the SW frequencies. We would expect to find that distance approximately at 5.8 m. That is; 3.6 m that Audyssey set + 2.2 m that is 1/2 WL at your 80 Hz XO setting. We also know that it’s necessary invert the SW polarity (or the polarity of all the main speakers for that alignment). 

[To clarify or possibly confuse a little: Audyssey did not select the same SW-Main timing that we would have selected if we intended to manually EQ the system. Therefore Audyssey did not start with as favorable SPL reinforcement in the XO range. It did however account for that in the EQ settings it calculated and applied. We expect to find similar XO conditions at 1/2 WL increments so the Audyssey EQ should still work there as well. In your particular case, since EQ is reinforcing a dip from 40-90 Hz, you may find the similar SPL response at a little larger SW distance setting, maybe as much as 6.2 m? REW would allow you to find and fine tune that alignment as needed.]

Again, if the alternate alignment is evaluated, I don’t know if you would hear a difference, or if you did hear a difference, which alignment you would prefer. It doesn’t seem too subtle to me, but I am using steeper XO filters which makes my GD difference greater than your will be.

If you do try the comparison, I would be interested to learn what your experience is.


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## THX-UltraII

> You have used REW to measure the SPL of the Audyssey XT results and confirmed that Audyssey did its job in all respects to meet the Audyssey House curve.


The only thing that still 'bothers' me is the Audyssey curve. My Onkyo TX-SR876 does not allow me to manually pick the Audyssey Reference (with roll-off at higher frequencies) or the Audyssey Flat curve. By default the Audyssey Reference curve is selected. The only way to get the Flat curve work is to select a THX mode. But I don t want to select a THX mode because THX applies processing that might not do any good to the measurements I did (see also http://www.hometheatershack.com/forums/audio-processing/60667-thx-listening-modes.html). So I m stuck with the Audyssey Reference curve with roll-off. ''So, what s the problem with that? The Audyssey Reference curve IS meant for movies and that is what I do''. Well, I ve read that the Audyssey Reference curve has a roll-off because 'normal/not acoustically treated living room' tend to produce too harsh high frequencies. But when someone DOES have a treated HT room (mine is really top-notch treated) the Audyssey Flat curve is recommended. So what s smart to do? Sell my Onkyo and look for a AVR where I CAN select the Audyssey Reference or Flat curve manually after the auto-calibration or just live with Audyssey Reference or even live with THX mode and get the Flat curve this way?



> We also now know there is also another SW distance setting that should result in a very similar SPL response, but result in less GD for the SW frequencies. We would expect to find that distance approximately at 5.8 m. That is; 3.6 m that Audyssey set + 2.2 m that is 1/2 WL at your 80 Hz XO setting. We also know that it’s necessary invert the SW polarity (or the polarity of all the main speakers for that alignment).
> 
> [To clarify or possibly confuse a little: Audyssey did not select the same SW-Main timing that we would have selected if we intended to manually EQ the system. Therefore Audyssey did not start with as favorable SPL reinforcement in the XO range. It did however account for that in the EQ settings it calculated and applied. We expect to find similar XO conditions at 1/2 WL increments so the Audyssey EQ should still work there as well. In your particular case, since EQ is reinforcing a dip from 40-90 Hz, you may find the similar SPL response at a little larger SW distance setting, maybe as much as 6.2 m? REW would allow you to find and fine tune that alignment as needed.]
> 
> Again, if the alternate alignment is evaluated, I don’t know if you would hear a difference, or if you did hear a difference, which alignment you would prefer. It doesn’t seem too subtle to me, but I am using steeper XO filters which makes my GD difference greater than your will be.
> 
> If you do try the comparison, I would be interested to learn what your experience is


I do want to compare it. Also to keep learning and to see what it does. So what I do is:
Set the Subwoofer AVR distance to somewhere between 5.8 and 6.2m (check this with REW which gives the best SPL in the XO range) while having my speaker wires switched (because I cannot change the subwoofer polarity). After this compare this with the 'original Audyssey' curve and see if the SPL curves are identical. If so, listen and see what the difference in sound is.


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## jtalden

> The house curve that sounds best to you in your room with your speakers and source material is very much a personal issue. 

> Your receiver probably allows you to adjust the tone controls on top of Audyssey and you probably have mid, bass and treble tone control for each set of speakers. That may provide the means to adjust the Audyssey HF rolloff and determine if the Audyssey curve is right for you. Use REW to measure the impact of the changes.

> Don't expect the other alignment to result in the "identical" SPL. It should be close enough however that the differences are insignificant.


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## THX-UltraII

> > Your receiver probably allows you to adjust the tone controls on top of Audyssey and you probably have mid, bass and treble tone control for each set of speakers. That may provide the means to adjust the Audyssey HF rolloff and determine if the Audyssey curve is right for you. Use REW to measure the impact of the changes.


Good suggestion. I only have Bass and Treble tone control. From the Onkyo TX-SR876 manual:

_*Tone Control Settings*You can adjust the tone (bass and treble) of the front, center, surround, and surr back speakers individually.
*Bass*You can boost or cut low-frequency sounds from –10 dB to +10 dB in 1 dB steps.
*Treble*You can boost or cut high-frequency sounds from –10 dB to +10 dB in 1 dB steps._

Of course I can never get a FLAT response with this method (like Audyssey FLAT does) because the roll-off will still be there...... 



> > Don't expect the other alignment to result in the "identical" SPL. It should be close enough however that the differences are insignificant.


ok, I ll post results.


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