Aligning Main speakers with sub

[Wull]

Hi.

Would anyone be kind enough to look at my REW sweeps to determine what delay I should use to align my front speakers with my sub response. Both are presently set to 0

 

[jtalden]

There is almost a 2 ms delay between the L and R speaker measurements. This is significant. Was the mic that far off center? Are your acoustic timing measurements of the speakers repeatable? I suggest this issue should be corrected before SW delay timing is chosen.

 

[Wull]

The measurements taken are not central to the mains. Decided on a different approach this time. My couch is central to the room but where I sit is to one side (the right).. This position also give me the best bass response.

The Mic is still in place from these measurements. I will adjust the main speakers and resend later.

Thanks

 

[Wull]

New measurements taken.

 

[jtalden]

The following timings result in favorable SPL support through the XO range.
80 Hz: Reduce the SW delay by 32.5 ms.
100 Hz: Reduce the SW delay by 31 ms.
120 Hz: Reduce the SW delay by 30 ms.

The chart below shows the impact of the 3 settings.

 

[Wull]

Cheers jtalden. Attached are the results using your SW delays provided. Looks promising.

I intend to run my processors EQ at the weekend (it does not provide speaker distances) this may help the final result? I shall report back.

 

[jtalden]

Something went wrong with these results. I may have made a mistake in the suggested timing. I'm not sure what to do.
Is the REW acoustic timing working correctly for you? The expected SPL support did not occur and the timing appears much closer, but is still different than expected.
Has your older thread setup changed? I either need to look back and read through the old thread to recall the equipment and background of your setup, or maybe you can summarize it again. I just opened one old mdat there at random and the SWs impulse trace looked much more conventional. This SW impulse measurement suggested possibly multiple SWs with a with significant divergent timing. Because of the very smooth SPL result and wide overlap in the XO range, I went ahead and provided a timing that should have worked well for SPL.

I could just redo the timing again using this latest mdat if you think they are good measurements. Please advise.

 

[Wull]

My setup is pretty much the same. The only things changed are I’ve added a further minidsp HD, also taken measurements from a MLP that provide a better LFE. I’ve used MSO to optimize my subs this time, this is probably why there is a large XO range.

 

[jtalden]

Okay, that helps. It appears MSO may have created some pretty large differences relative timing between the 4 SWs that resulted in excellent SPL smoothness. The impact on the phase is pretty chaotic however. Phase is normally not an issue for sound quality, but it does make my normal approach SWs to mains timing alignment almost useless however. I will just look at the Post-6 data and see if another SWs delay adjustment will get back to the targeted alignment.

 

[jtalden]

The attached charts and mdat are the result of changing the SWs delay timing +6.54 ms (more delay). The current relative polarity of the Subs and Jan 28 measurements is correct. There was only the one set of measurements for sub and mains. The other measurements were subs+mains. I hope this was the XO you decided to use. There is plenty of SPL support across the XO range so EQ in this range should be no problem.
Please disregard my previous comment about the MSO subs phase. It is not nearly as bad as I remembered from yesterday. In the XO range it is reasonably normal and was no problem for the REW alignment tool. The unusual sub impulse shape and resulting step response led me to expect there would be a bigger problem using the tool. There should be no issues with this alignment.

 

[Wull]

I hope I've done this correctly. 80Hz XO I added a further 6.54ms delay (I cannot reduce the sub delay so I increased the mains speakers) The left speaker is now 39.04ms and the right speaker 40.06ms.

Attached results

 

[jtalden]

Looks good.

 

[Wull]

Hi jtalden. Would you mind having a look at my latest REW measurements to see what XO would suit please. These are a fresh set of MSO results. Instead of combining my 'front of room IB manifold' with 'rear of room IB manifold' & '2 x DIY ported subs' (this equates to 4 subs), I sealed the ports on the 2 x DIY subs and combined their response as one (now 3 subs). This combination/result has given me more headroom to play with. The sub's amplifier gains are more equal. Also the time delay between subs has shortened quite considerably. A 80Hz XO is what I am hoping to use.

I will then run my processor EQ to see which works out best.

 

[jtalden]

Sealed Subs:
Reduce Delay on SWs 16 ms and invert there polarity. This is the conventional timing. An another favorable option is reduce the SWs delay by 22 ms and retain the current polarity.

 

[jtalden]

Sealed Subs.2:
Reduce Delay on SWs 21.74 ms.

 

[Wull]

Thank you so much. 'Sealed subs. 2' appears to give me the better result, and is the one I will stick with. I have run my processor EQ. With this enabled the L & R channels combined produce a nasty null around 70-80Hz. however your delay really helps with this (not so much with sealed subs).