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).
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).