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Discussion Starter #1
Hi Guys, interested in your thoughts on this one....

We know that Audyssey XT32 doesn't always get the sub distance (delay) correct with the mains..

I would suppose when one does the sub distance tweak, most end up adding more to the sub distance than Audyssey finds, would I assume that's correct for most?

e.g. Lets say the L&R speakers are 12' away from the MLP and the subs up front are 11' 6" away from the MLP. XT32 sets the mains at 12' and the subs at 12' 6". Would most find after doing a sub distance check they have to add even more to the distance XT32 set?

OR.
Has anyone in this example ever found they got a better measurement by having less distance/delay to the sub than any actual physical distance. e.g in this case 9'?

Im just trying to understand can a lesser distance for the sub than its actual true distance ever produce a better reading on REW?
 

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Hi Guys, interested in your thoughts on this one....

We know that Audyssey XT32 doesn't always get the sub distance (delay) correct with the mains..

I would suppose when one does the sub distance tweak, most end up adding more to the sub distance than Audyssey finds, would I assume that's correct for most?

e.g. Lets say the L&R speakers are 12' away from the MLP and the subs up front are 11' 6" away from the MLP. XT32 sets the mains at 12' and the subs at 12' 6". Would most find after doing a sub distance check they have to add even more to the distance XT32 set?

OR.
Has anyone in this example ever found they got a better measurement by having less distance/delay to the sub than any actual physical distance. e.g in this case 9'?

Im just trying to understand can a lesser distance for the sub than its actual true distance ever produce a better reading on REW?
More distance vs. less distance depends on numerous factors. Most will agree that the most important is a smooth frequency response transition at crossover between sub and mains. So more or less distance will depend on on what gives you that smoother transition. There are ways to calculate what it should be, but it is far simpler to trial/error find what works best by changing it 1 or 2 feet in one direction then taking a measurement to see if that crossover transition is smoother or worse. You can usually find the best setting in 3 or 4 tries.

Timing: Not as critical, because our response to low frequencies is kinda sluggish anyway. Given the choice, most would probably set the sub distance further away. That way the timing compensation pushes the sub signal earlier, and it might be perceived a "quicker" or "tighter" match with the mains signal.
 

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Discussion Starter #3
More distance vs. less distance depends on numerous factors. Most will agree that the most important is a smooth frequency response transition at crossover between sub and mains. So more or less distance will depend on on what gives you that smoother transition. There are ways to calculate what it should be, but it is far simpler to trial/error find what works best by changing it 1 or 2 feet in one direction then taking a measurement to see if that crossover transition is smoother or worse. You can usually find the best setting in 3 or 4 tries.

Timing: Not as critical, because our response to low frequencies is kinda sluggish anyway. Given the choice, most would probably set the sub distance further away. That way the timing compensation pushes the sub signal earlier, and it might be perceived a "quicker" or "tighter" match with the mains signal.
Thank you so much Wayne for that very comprehensive and clear explanation.

Can you answer this question please?

If the crossover transition is smooth at + or - 1,2,3' (always good) but a dip becomes much less in the minus region say 3' its still ok to go less than more? When I say less I mean approx the same real distance the subs are from the MLP?
 

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Thank you so much Wayne for that very comprehensive and clear explanation.

Can you answer this question please?

If the crossover transition is smooth at + or - 1,2,3' (always good) but a dip becomes much less in the minus region say 3' its still ok to go less than more? When I say less I mean approx the same real distance the subs are from the MLP?
I would say yes. The wavelength of an 80 Hz tone is 14 ft. I am going to make an educated guess (I looked for an online source but could not find one) that at least a full wave, probably more, is required at that frequency before perception of sound occurs. We're really splitting hairs here. I'm sure what you suggest would not be a problem. When you are splitting hairs and have the option to split in the direction that is theoretically better in one way, you do it, why not? But in this case there is a clear benefit in going the other way, although not nearly far enough to warrant concern, and it is not just for theoretical benefit, it is for a measurable and probably audible one. You are on pretty safe ground.
 

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Discussion Starter #5
I would say yes. The wavelength of an 80 Hz tone is 14 ft. I am going to make an educated guess (I looked for an online source but could not find one) that at least a full wave, probably more, is required at that frequency before perception of sound occurs. We're really splitting hairs here. I'm sure what you suggest would not be a problem. When you are splitting hairs and have the option to split in the direction that is theoretically better in one way, you do it, why not? But in this case there is a clear benefit in going the other way, although not nearly far enough to warrant concern, and it is not just for theoretical benefit, it is for a measurable and probably audible one. You are on pretty safe ground.
Thanks for that confirmation Wayne. And yes in my case the sound is way better going less than what XT32 finds, -3'. It not only shows a marked improvement when measuring but also sound in the room seems faster, louder and much more tactile, its a remarkable improvement.

The spl on the measurements also show higher and narrower round where the dip of 60Hz I have is. So all in all it seems like a winner going the opposite way than "normal" for my room.
 

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Good observation also that your sound seems faster with the change in the direction you mentioned. That is probably a perceptual result of having an important portion of your low frequency spectrum better represented and it was before.
 

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I just dug out REW again and fixed a hole I had between about 85 and 100hz. I almost only use my phone for HTS, but I'd like to post the mdat files for someone smarter than me to look at. I didn't get to do any critical listening but bass in general sounds more subtle, and slightly tighter. In my head? I'll try and get to it tomorrow. I changed the setting from 10' to 17'.
Here's the before just for fun.
 

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Discussion Starter #8
I just dug out REW again and fixed a hole I had between about 85 and 100hz. I almost only use my phone for HTS, but I'd like to post the mdat files for someone smarter than me to look at. I didn't get to do any critical listening but bass in general sounds more subtle, and slightly tighter. In my head? I'll try and get to it tomorrow. I changed the setting from 10' to 17'.
Here's the before just for fun.
Is this with L+R mains combined?
 

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Discussion Starter #11
We need to see L alone or L+sub(s) alone, and R alone or R+sub(s) alone. NEVER measure L & R together.Vertical scale should be 45 dB to 105 dB.
So Wayne one should look for the smoothest response at the crossover of L+Subs and then R+Subs?
This then becomes the best sub delay?

Never combined?
 

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So Wayne one should look for the smoothest response at the crossover of L+Subs and then R+Subs? This then becomes the best sub delay? Never combined?
this does make sense since the output of the mains is rarely the same. I didn't think about that much till now. I need to resize too.
 

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We need to see L alone or L+sub(s) alone, and R alone or R+sub(s) alone. NEVER measure L & R together.
Wayne, never say never (lol)! :R Seriously now...

Question 1:
Acknowledging your expertise, can you please elaborate. I thought that L+R+sub(s) was measured because we want combined response to be smoothest, and because that's what we hear most of the time. Are individual CH+sub(s) measured only in the context of setting delays (and not in the context of correcting frequency response)?

Question 2:
Given that we need to measure L+sub(s) and R+sub(s) individually in the context of setting sub delay, are they averaged together to provide a single delay factor? I'm unclear how a single delay control on/for a sub can account for them. Are we talking about setting L-delay, R-delay, and sub-delay together? Man, I have a feeling I'm going to feel silly. :dumbcrazy:
 

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Discussion Starter #15
Wayne, never say never (lol)! :R Seriously now...

Question 1:
Acknowledging your expertise, can you please elaborate. I thought that L+R+sub(s) was measured because we want combined response to be smoothest, and because that's what we hear most of the time. Are individual CH+sub(s) measured only in the context of setting delays (and not in the context of correcting frequency response)?

Question 2:
Given that we need to measure L+sub(s) and R+sub(s) individually in the context of setting sub delay, are they averaged together to provide a single delay factor? I'm unclear how a single delay control on/for a sub can account for them. Are we talking about setting L-delay, R-delay, and sub-delay together? Man, I have a feeling I'm going to feel silly. :dumbcrazy:
I believe this is what is correct, but we need to wait for Wayne.

Measure L+sub(s) and R+sub(s) individually in the context of setting sub delay, then they are averaged together to provide a single delay factor.
 

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OK, ok, maybe not NEVER.

I can see that running all mains and subs together to see how they combine at the sub crossover freq could be of value. However.....

You would not want to vary either the timing or the level of either of the mains even the tiniest bit for the sake of sub crossover smoothness, as the negative consequences on soundstage and imaging would be huge.

For any purpose I can think of above that freq, individual measurements of the mains are a must.

Thanks for keeping me honest.
 

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So Wayne one should look for the smoothest response at the crossover of L+Subs and then R+Subs?
This then becomes the best sub delay?

Never combined?
This is moot as the general practice is that you should be targeting the center speaker, not left/right speaker.
Some may say the center speaker is the most important for movies, but those awesome soundtracks and background musics are all playing on the main left and right, not the center.

So...to all the experts... do you set the sub distance to get the best curve with the center or left/right?
 

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Mark Seaton, of Seaton Sound, recommends using Center Channel for the very reason you gave. My own preference is to use Left and Right, as music is a higher priority for me.

I could be wrong, but I have not seen there to be a real general practice about it, more like a couple of different approaches depending on personal preference. I am open to other viewpoints, however.
 

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Discussion Starter #20
This is moot as the general practice is that you should be targeting the center speaker, not left/right speaker.
Some may say the center speaker is the most important for movies, but those awesome soundtracks and background musics are all playing on the main left and right, not the center.

So...to all the experts... do you set the sub distance to get the best curve with the center or left/right?
Gee I never thought bout it this way!

Im certainly far from any expert, only have one toe in the door....
But since most of the music in movies comes from the L+R I would thing getting those two channels best for bass would be the most important, that's the way Im now doing it.

However I too would love to hear from those who are more into their movies than music listening.
 
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