New room, sub integration, xo, delay and second sub to come, help with alignment tool

[FargateOne]

@jtalden I tried to follow the steps explained in others threads to find how you arrived to JA1 settings (or ja3 btw). In #27 you said that you spent a day to find them. I believe you!.
I found the 1ms difference between the 2 sub timing in JA5, I found the 6ms difference common to JA 1 and JA3. But I would never found to add 10ms to both (approx) and reverse the polarity of 1 sub.

 

[jtalden]

I just saw that the low bass was suppressed when the 2 SWs were the same polarity due to the phase differential there. I reversed the polarity of one the SWs to help that. With them opposite polarities there is the potential for SPL problems in the mid bass, but that looked okay in this case so this became a viable option.

Of course what works in the room for the LP is unique to that position given the current SW positions. The bass distribution in the other parts of the room will be different, but I couldn't say if it is likely to be better or worse for SPL variability.

If you compare the options, I would be interested to know if you hear differences and which you prefer.

 

[FargateOne]

(...)
If you compare the options, I would be interested to know if you hear differences and which you prefer.

I spent one month with JA3 and changed for ja1 2 days ago. The difference, to the better, was noticeable. The sound of the low and medium frequencies seems more homogeneous.

 

[FargateOne]

I just saw that the low bass was suppressed when the 2 SWs were the same polarity due to the phase differential there. I reversed the polarity of one the SWs to help that. With them opposite polarities there is the potential for SPL problems in the mid bass, but that looked okay in this case so this became a viable option.
(...)

Th polarity inversed I understand but I wouldn't find to add 10ms to both subs after adjusting the sub together with a 6ms delay.

 

[jtalden]

The table in Post-38 is apparently correct. The proof is in your measurements with these setting in Post-44. Below is a screen shot of the REW alignment tool setting and attached is the working file that was used.

I am unsure why you didn't find the ja5 alignment. Possibly you focused on an alignment were there is more of a crossing phase situation with the woofers being delayed by 1 wavelength. It is best to find the closest phase tracking between the SWs and the mains. The SPL will be similar with the delayed SWs setting, but the SWs direct sound will arrive 1 cycle later than the mains.

 

[FargateOne]

Thanks for the working file. I see what I missed. In my amateur mind, I thought it wasn't possible to find a new delay with the aligned sum of the 2 subs.

But what intrigued me most is how you could have considered that adding -11ms would give the better phase alignment found. If I had figured it out on my own, I would have stopped looking after aligning the 2 subs together with the ... and a delay of -6ms, I could not suspect that an additional delay could have a better result. I guess that's where your experience comes in, which you can't buy on Amazon!

Translated with www.DeepL.com/Translator (free version)

 

[jtalden]

Below is the comparison of the -11 ms delay change vs a -6 ms delay change with the 2 SW inverted. Both are resonable settings. The phase tracking is shown here is for the -6 ms case. I looks good through the main part of the XO range and only departs near the XO extreme frequencies. It is a little more of a crossing phase situation as compared to the -11ms setting shown in Post-55. The result being the SPL support in the 140 Hz range where the -6 ms setting (black trace) shows less SPL support due to the greater phase deviation.

I also check to assure that the relative position of the L+R impulse and the SWs impulse are reasonably aligned. In an Ideal LR24 XO alignment the initial rise of the 2 impulses would occur at the same time. The chart below shows t=0 set near the L+R impulse position and the -6 ms setting SWs impulse rise starting at about +1 ms and the -11 ms setting starting at about -4 ms. It is rare to actually achieve an acoustic ideal LR24 XO without a lot of effort so it is normal for the most favorable timing for phase tracking and SPL support to deviate one way or the other. In this case the -6 ms setting is close to the ideal impulse positioning. The -11 setting provides better phase tracking and slightly better SPL support as a result. So the reason for my selection of the -11 setting was just the improved SPL support around 140 Hz. It is just as resonable to select the -6 ms setting when providing appropriate EQ. There may, or may not, be an impact to your sense of sound quality between these to options.

 

[FargateOne]

@jtalden I have a question about inverting polrity for one sub. Whether I change the polarity of the left or right sub should make no difference to the favorable timing of the 2 subs, right? So if I feel that the sound is different it is purely imaginary, no?

 

[jtalden]

It's not the same.
To illustrate, below I used the measurement of your 2 Subs summed together. Red is with sub1 inverted and green is with sub2 inverted.

SPL is identical

Impulse and step response is reversed

Phase is 180° offset

Thus, to achieve favorable phase tracking in the XO range with the mains, the delay timing will need to be different (corresponding to about 1/2 wavelength of the XO frequency). If the delay timing is adjusted favorably in each situation the net impact on main channel SPL measurements is negligible. The channel responses will be only slightly different in: XO phase tracking, overall phase rotation and group delay. If the timing is not changed then the expected SPL null at the XO results. This is all closely analogous to comparing the case with both SWs having positive vs negative polarities.

In my limited experience, the sound quality can be impacted and that is why I often ask people to let me know if they also find a significant difference and which they prefer.

If you tried this, did you adjust the XO delay timing appropriately? If so, did you hear a difference.

 

[FargateOne]

(..)

In my limited experience, the sound quality can be impacted and that is why I often ask people to let me know if they also find a significant difference and which they prefer.

If you tried this, did you adjust the XO delay timing appropriately? If so, did you hear a difference.

I haven't forgot you but the Minister of Internal Public Works ordered the renovation of the laundry room which forced us to pause the opportunities to play with our knick-knacks (as she called it...!) When I tried it I didn't change anything but the polarity.
Now that the work has just been accepted, I expect to be able to get down to real business soon!