Checking the audysee distances with REW is different. Which is correct?

[matt burton]

Hi All. I'm checking the after-cal distances with REW and find that most channels, except the surround rear L and R and the surround L, are off with the impulse response. The SUB is well off when checked with REW.
Denon Avr 4520 with audysee XT32

1) asio output 7.1 hdmi with surround Back Right (closest to mic) as the timing reference. (which seems to make NO DIFFERENCE)
2) all sweeps including the sub are 15-10K Hz
3) the sub physical distance is 3.8m and the audysee gives 4.77m which seems about right given a bit of processing delay(REL storm 5 LFE connection)
4) all REW sweeps with audysee sound correction off.


The gains appeared to be pretty good, maybe added 0.5db to a couple of channels when checking the receiver test tones with the REW mic, but the timing via impulse response seems way off.

When I do sub sweeps with 15-500Hz, the impulse response gives a closer estimated IR delay, but still about 0.4m off. with the 15-10K sweep the sub appears to have an estimated delay of 0.59m.

Which do I trust - that audysee sets the correct distances or not?
Other thoughts?

 

[John Mulcahy]

Sub looks like it is delayed a little more than it needs to be, the other channels are reasonably close but could be tweaked a little. Don't think REL subs usually have much in the way of processing so wouldn't expect additional delay from that.

 

[jtalden]

This looks pretty good overall. The SW SPL response looks very good. It's hard to be sure how you set up and measured the system. What was the AVR XO setting? Your L, R mains appear to be set to 'large' or they possibly included the SW. You may want to set them 'small' with a 80-100 Hz. That should even out the bass response and mitigate the 60 Hz SPL dip in the L channel. The room effects in the L and R channels from 90-150 Hz will continue to result in SPL sag and roughness in that area, but adjusting the SW distance/timing may help that a little.
Whatever your chosen XO frequency, if you post an mdat with 3 measurements as:
Setup - (as before)

• Acoustic timing active
• 15-10k Hz measurement sweeps

Measure -

1. L (set 'small' and SW off)
2. R (set 'small' and SW off)
3. SW (alone; measured using the L channel, but the with the L main speaker disconnected. This is necessary as we need to see the redirected bass response, not the LFE response.)

We can then use the REW alignment tool to confirm if the SW distance setting is favorable. It will also calculate the overall frequency response change that will result if a more favorable distance/timing setting is found.

 

[matt burton]

Sub looks like it is delayed a little more than it needs to be, the other channels are reasonably close but could be tweaked a little. Don't think REL subs usually have much in the way of processing so wouldn't expect additional delay from that.

yes, so adding a little bit of distance would seem to be correct? (delaying all other channels)

 

[matt burton]

This looks pretty good overall. The SW SPL response looks very good. It's hard to be sure how you set up and measured the system. What was the AVR XO setting? Your L, R mains appear to be set to 'large' or they possibly included the SW. You may want to set them 'small' with a 80-100 Hz. That should even out the bass response and mitigate the 60 Hz SPL dip in the L channel. The room effects in the L and R channels from 90-150 Hz will continue to result in SPL sag and roughness in that area, but adjusting the SW distance/timing may help that a little.
Whatever your chosen XO frequency, if you post an mdat with 3 measurements as:
Setup - (as before)

• Acoustic timing active
• 15-10k Hz measurement sweeps

Measure -

1. L (set 'small' and SW off)
2. R (set 'small' and SW off)
3. SW (alone; measured using the L channel, but the with the L main speaker disconnected. This is necessary as we need to see the redirected bass response, not the LFE response.)

We can then use the REW alignment tool to confirm if the SW distance setting is favorable. It will also calculate the overall frequency response change that will result if a more favorable distance/timing setting is found.

THanks I will do this today. Yes the L R are always set to Large, as they are 804 D3's and have a sizeable power amp attached. (plus they are usually hi level to the REL but for the purposes of this excercise I have left that unconnected for now).

Any thoughts on why most of the channels apart fro the sub issue, are about 200-300mm out?

 

[matt burton]

Also why is the sweep length frequency completely altering the LFE response impulse calculation? (from about .6m to 0.38m)

 

[matt burton]

Well this is weird. Today everything seems to be well lined up to each other (using the original audysee sub distance). The alignment tool is almost identical to the real scenario.

 

[jtalden]

With very capable main speakers like the 804's there is no reason not to run them as large if you like. I checked the SPL with the current timing in Post 1 vs SW setup changes I would recommend. The change in SW settings for this result were:

• Invert the polarity of the SW
• increase the SW distance by 0.35 m.

L+R+SW Current timing vs Changed SW Settings [The SW level is the same in both cases. It apparent level change is the result of the SW being out of phase through most of the bass range vs being in phase with the changed settings. The actual level used should be adjusted to your preference.]

L+SW vs R+SW to show the channel differences with the changed SW settings.

Channel Delays:
The 3 fronts are timed to each other very well. The timing of the surrounds is reasonably good also and their timing is not as critical anyway. The SLBack is delayed 400 mm as you noted, but I would expect that movie material music is sometimes mixed such that the surround sounds are delayed by a much greater amount than that to add a sense of spaciousness. There is nothing wrong with timing them closer if you like. I time the surrounds closely in my system though I don't really think it is necessary. Upmixed stereo music spaciousness may be improved with an additional 50-80 ms delay added in the surround channels. I think some people do that. I don't know if the digital upmixers already do that for us or not. This is not my area of expertise.

 

[matt burton]

Have you used the results from today (post 7 and not post 1) as the timing between each day seems to be changing!

 

[jtalden]

Also why is the sweep length frequency completely altering the LFE response impulse calculation? (from about .6m to 0.38m)

I don't understand the question.

 

[jtalden]

Have you used the results from today (post 7 and not post 1) as the timing between each day seems to be changing!

I used post 1 as that is one option for your situation. I will look at the new data and try to understand what is changing.

 

[jtalden]

Also why is the sweep length frequency completely altering the LFE response impulse calculation? (from about .6m to 0.38m)

The XO impacts the SPL range and resulting impulse. So when REW reports the impulse offset I will be appropriately different. That is why it is best to measure the SW with the XO active as that is how it will be used when the Mains are set to small.

 

[matt burton]

I can't even replicate your curves....

 

[matt burton]

The XO impacts the SPL range and resulting impulse. So when REW reports the impulse offset I will be appropriately different. That is why it is best to measure the SW with the XO active as that is how it will be used when the Mains are set to small.

Got it. Surprisingly the LFE and sub from L are identical (almost) in timing today.

 

[jtalden]

I can't even replicate your curves....

I did the following:

1. Vector averaged L and Right mains using trace arithmetic (A + B) / 2.
2. In the alignment tool I selected that L, R average and the Sub.
3. Then found that a settings of:

• SW -10 dB [Done to offset of the SW level down since the LFE channel was used to measure it instead of the main channel. The level doesn't really matter as can be adjusted to taste later as you mentioned])
• SW -1 ms
• SW inverted

I will analyze the post 7 data tomorrow.

 

[jtalden]

I just analyzed the Post-7 data. As you already determined, the XO timing (SW distance settings) is correct as-is. No setup changes will be helpful using this XO frequency.