# Time Alignment Help?



## h5tuu (Nov 26, 2011)

Hi all,

I've recently built a pair of DIY subs and I'm hoping to integrate them into my system to the best of my ability using REW.

I've used the impulse response overlays in REW to time align all the main speakers. How do these look?

Could someone please take a look at my .mdat file to see how I would be best integrating the subs?

For reference I've set the bass management crossover to 100hz, also all settings in my processor relating to the sub are currently set to 0. I also have no EQ applied to any of these measurements, I'm hoping to get the time domain sorted before adding any form of EQ to the system.

I do not have Audyssey so I believe this is the best route......

Link to my .mdat file: https://www.dropbox.com/s/ja9j0ov9ok3j270/HTS%20NO%20EQ.mdat

If anyone would like to see some measurements I've not included please let me know.

Thanks in advance.


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## h5tuu (Nov 26, 2011)

A couple of screengrabs, hopefully help a little..

Impulse response overlay of all main spears, no subs.










Subs.










Both subs and mains.


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## jtalden (Mar 12, 2009)

Good setup for timing!

> The mains are well timed.
> The SW's are well timed to each other.
> The SWs are well timed to the mains. It is very near a conventional alignment. 
> The best timing I found was with the SW's delayed about 2 ms more(distance about 2 ft less). The SPL difference is very small as this is a minor adjustment at 100 Hz. Anyplace in this range is about as good as it will get.

Also:
You may want to look at other SW positions if you haven't already. The SPL is very peaked at 46 Hz and this may smooth out a little with different positioning, or it may not. As it is now, it looks like the SW level needs to reduced and EQ applied to better smooth the low end.

Just an aside: 
There is no issue with doing a rough EQ to smooth the SWs a little in the final position before making the final timing and level adjustments. The EQ can then be fine tuned again or redone again without impacting the timing.


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## h5tuu (Nov 26, 2011)

Many thanks for the reply.

It sounds like I'm off to a reasonable start .

When you say delay the SW by 2ms, this would mean the peak of the mains and also the SW would align at around the same point?

Due to the room layout the subs are not able to move, I also get the same response across the whole listening position.

Once I've nailed this I will jump into EQ and post up my results.

One quick question, is it possible to examine and predict the correct time delay for the SW using group delay? I believe you can but always seem to get very varied results.


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## h5tuu (Nov 26, 2011)

I figured a picture paints a thousand words, which of the following would it be?

Green = 0ms
Red = +2ms
Dark Green = -2ms


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## jtalden (Mar 12, 2009)

h5tuu said:


> When you say delay the SW by 2ms, this would mean the peak of the mains and also the SW would align at around the same point?


The dark green is the SWs delayed by 2 ms. The impulse is later in time. Anything between your "0ms" and your "-2ms" will be just fine.



> Due to the room layout the subs are not able to move, I also get the same response across the whole listening position.


Okay.



> Once I've nailed this I will jump into EQ and post up my results.


Great - I'm interested.



> One quick question, is it possible to examine and predict the correct time delay for the SW using group delay? I believe you can but always seem to get very varied results.


I find it difficult to use GD because the room modes create a lot of variation in the chart. With smoothing and windowing I can usually work it out, but basically that is probably because I already know the answer from the setup using phase. I think it may vary a lot depending on the room; mine is not too accommodating.


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## h5tuu (Nov 26, 2011)

Thanks .

A quick one on phase....

A screencapture of the FL, the SW at my '0' and the SW at my '-2'.

I've shifted the impulse response near to 0 (shifted all measurements by 33ms) so I get a better idea of what I'm looking at,










Now a shot of the phase,










To me it looks like the SW at 'my 0' tracks the FL better through the crossover range.

Please could you explain how I would best interpret this reading? And also why the -2 may be a better option?

Many thanks.


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## jtalden (Mar 12, 2009)

I found it very difficult to read the phase of your FL and SW's. Depending on the smoothing and windowing used we can easily pick different settings. The 2 ms difference in the values we found is not very significant. I indicated we are fine anyplace in the that range and maybe even a little wider.

I looked a the phase of all 3 fronts to decide the general trend of the main speakers and then tried to match the phase of the SWs to that average as well as possible. It was difficult to do in this case due to some conflicting room modes of the mains Vs the SWs.

I made my final choice of "best" alignment by looking a the smoothed SPL of the FL+SWs as shown below. Yellow is "0ms"and Green is "-2ms". There appeared to be slightly better SPL support at "-2ms".

Had I also looked at the FR+SWs and CC+SWs maybe I would have come to a different setting?


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## h5tuu (Nov 26, 2011)

Thanks again for another great reply. 

I sure see what your saying, I hope to add some EQ this evening and will be posting a fresh .mdat file with the results...

Hopefully this shouldn't alter the timings to much, I do know the EQ does add around 30ms of system delay to all channels though so may need some minor tweaks. 

I may also target a lower (80hz) crossover, it depends how my subs cope on a full range sweep. 

Stuart


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## h5tuu (Nov 26, 2011)

Right then . 

I've added some EQ to the mix,

Link to the new .mdat file,

https://www.dropbox.com/s/fadvx1k41yz36f1/HTS EQ.mdat

It looks to me like the timing has adjusted slightly? The system delay is now visible but the SW impulse looks quite a bit different? I obviously haven't got the mic in the 'exact' same spot but it's pretty close....

Opinions please?

Thanks .


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## h5tuu (Nov 26, 2011)

Without wanting to sound like I'm dominating the thread lddude:.

I've just done some more testing, I decided to give laser188139's band limited impulse plot method a go.

So I did a measurement from 97hz to 103hz (crossing to the SW at 100hz) on both the FL and also the SW set to '0'.

This is the outcome,










Looks almost bang on?

So I decided to generate the frequency response in REW and also run a full sweep (0 to 20KHZ) to see how the results compared, this is what they look like. REW is the purple and the actual measurement is the dark green.

REW does a pretty good job of generating frequency response graphs .










Finally a screengrab of the FL + SW (again 100hz crossover) to see the full scale result.










I currently have the subs calibrated 6db hot but looking at these results it may be a little to much? Guess more listening is required .

In the mean time if anyone has any suggestions for me to try, please fire away.


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## jtalden (Mar 12, 2009)

I checked out the new data and it looks very good. I tried a couple of quick changes and your timing looked better. Well done.

The narrow IR test appeared to work very well and confirmed the timing.

The measurement Vs Calculation also looks pretty good. I usually get even closer agreement than you did. Maybe your mic moved a little or maybe this is just the difference in our rooms.

You seem to have this whole process well in hand now. 

I agree your SW SPL level looks too high. Actually it looks very high to me, but that is a matter of taste. You might want to setup a custom house curve and match the EQ to that. Then as you decide to change EQ you can establish a new house curve as desired and adjust the EQ accordingly. That way it is possible to back up to an old setting without too much trouble.

I have had 21 different house curves before I finally settled on my current favorite. Below is an example file. You can use a text editor to change the values to suit your needs. I actually created all mine in Excel and chart them. It makes it easier editing changes and it shows the graphic comparisons. You can load your file as a house curve and also load it into the measurement area if you want to overlay it with several measurements. It will come in at 0 dB, but then just offset it to match the level of your actual measurements.

View attachment jtaHouseCurve21.txt


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## h5tuu (Nov 26, 2011)

Thanks very much for another great reply .

I need to work on the levels and also EQ slightly, I also need to do the main thing... Have a listen.

As far as EQ goes I'm aiming for a similar response to the Harman Synthesis curve I've seen recommended. It also suits my ears.










And where I'm at now,










Shouldn't be a huge amount of work, hoping I get time to work on this later on today.


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