# Sub distance tweaking



## RapalloAV (Aug 5, 2009)

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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## AudiocRaver (Jun 6, 2012)

RapalloAV said:


> 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..
> 
> ...


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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## RapalloAV (Aug 5, 2009)

AudiocRaver said:


> 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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## AudiocRaver (Jun 6, 2012)

RapalloAV said:


> 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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## RapalloAV (Aug 5, 2009)

AudiocRaver said:


> 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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## AudiocRaver (Jun 6, 2012)

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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## willis7469 (Jan 31, 2014)

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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## RapalloAV (Aug 5, 2009)

willis7469 said:


> 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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## willis7469 (Jan 31, 2014)

RapalloAV said:


> Is this with L+R mains combined?


 yes. Mains plus 3 subs.


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## AudiocRaver (Jun 6, 2012)

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.


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## RapalloAV (Aug 5, 2009)

AudiocRaver said:


> 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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## willis7469 (Jan 31, 2014)

RapalloAV said:


> 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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## Lumen (May 17, 2014)

AudiocRaver said:


> 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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## Medi0gre (Oct 30, 2012)

Im glad you asked!


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## RapalloAV (Aug 5, 2009)

Lumen said:


> 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)?
> ...


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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## AudiocRaver (Jun 6, 2012)

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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## Lumen (May 17, 2014)

Thank you, kind sir! :sn:


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## Skylinestar (Oct 19, 2010)

RapalloAV said:


> 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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## AudiocRaver (Jun 6, 2012)

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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## RapalloAV (Aug 5, 2009)

Skylinestar said:


> 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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## willis7469 (Jan 31, 2014)

RapalloAV said:


> 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.


 that's my thinking too, as is Wayne's I believe. My thinking is if you make it good for music, movies will have to follow suit.


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## AudiocRaver (Jun 6, 2012)

That is my viewpoint and approach. It works well for both music and movies. Center Channel is higher priority for dialogue, and dialogue does not reach down to the sub crossover point. Of course, anything can be mixed to the center channel, and 5.1 music mixes can end up with anything on any channel, but 90% of the time it is the L & R Mains that are carrying the music load and seem to benefit the most from a smooth sub crossover.


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## Mark Seaton (Jun 22, 2006)

Skylinestar said:


> 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?





AudiocRaver said:


> 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.


Hi Wayne,

Both approaches can work just fine. My preference for starting with the center is that you have a single speaker to deal with and aren't battling L/R asymmetries in the room. Usually at this point you've already done a first pass of distance settings, so you can anchor everything relative to the center.

While we tend to think of voices being higher in range, deeper male voices like a Morgan Freeman or James Earl Jones have some components affected by the subwoofer range. The plosives sounds or stop consonants like p, t, and k are the sounds most obviously affected by the lower frequency balance and crossover region. If you play with the crossover smoothness and adjusting the subwoofer level +/- a few dB with the same scene, you can notice changes in the quality of these sounds. These sounds subjectively punctuate dialog and help greatly with dialog intelligibility. When too strong or resonant these sounds will muddy the dialog and create a noise you have to listen through rather than helping with intelligibility. 

You can do some searching on the STI measurement (Speech Transmission Index) which quantifies intelligibility. The important take away is that time and magnitude modulation of octave bands extending from 125-8kHz are the most important. One octave around 125Hz extends to about 88Hz, and is not a hard cut off. For most home theaters we are in the upper ranges and very fine delineations of the STI measurement, but some rooms certainly fall short 500Hz and below due to acoustics and speaker interaction.

Point being, for me, subtle balance differences around the crossover greatly impact the subjective dialog quality and character. For this reason when calibrating I start with the center channel and determine a small range of acceptable and preferred performance. I then move to the left/right and see how these settings work out so I know what compromises I'm making to the center channel. I usually make a choice and give a quick listen in stereo and then go back to the center can insure I am still happy with the balance and voicing. Of course in systems where 2ch music is a very high priority, I give more weight to the L/R channels, but still start with the center channel since dialog intelligibility is such an important aspect I want to know what compromises I am making.

Many ways to skin the cat.


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## AudiocRaver (Jun 6, 2012)

Mark, thank you for responding in such detail. I know of no one who has more experience with this than you. Your perspective on the matter is greatly appreciated.


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## RapalloAV (Aug 5, 2009)

Mark Seaton said:


> Hi Wayne,
> 
> Both approaches can work just fine. My preference for starting with the center is that you have a single speaker to deal with and aren't battling L/R asymmetries in the room. Usually at this point you've already done a first pass of distance settings, so you can anchor everything relative to the center.
> 
> ...


This is very interesting to read Mark, thank you for your comments.
I would really like to try just the centre channel only but I cant get just centre anymore with the new AVRs that removed PLXII. I use XTZ and still can only get L& R channels separately. We need PLXII to play just centre channel but there is no way I can do it on my new pre pro Marantz AV8802. Is there anyway you or anyone else can give me a way to test just centre channel, most important since its the most important speaker in a HT setup.

Thanks in advance....

Just had a thought, I can get combined L+C+R is this any good?


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## Skylinestar (Oct 19, 2010)

RapalloAV said:


> This is very interesting to read Mark, thank you for your comments.
> I would really like to try just the centre channel only but I cant get just centre anymore with the new AVRs that removed PLXII. I use XTZ and still can only get L& R channels separately. We need PLXII to play just centre channel but there is no way I can do it on my new pre pro Marantz AV8802. Is there anyway you or anyone else can give me a way to test just centre channel, most important since its the most important speaker in a HT setup.
> 
> Thanks in advance....
> ...


By common sense, the DSU should mix the common L/R sound to the center.
Are you using REW (with asio4all) via HDMI output to your AV8802? If yes, you can test each channel.


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## RapalloAV (Aug 5, 2009)

Skylinestar said:


> By common sense, the DSU should mix the common L/R sound to the center.
> Are you using REW (with asio4all) via HDMI output to your AV8802? If yes, you can test each channel.


As I mentioned in my post I use XTZ, there is no way to get just Centre channel since the 8802 doesn't have PLXII.


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## AudiocRaver (Jun 6, 2012)

I do not know your complete configuration, so this is partially guesswork.

Sounds like you are going into your AVR via analog, not HDMI. You can use a RCA-F to dual RCA-M adapter to take the test signal and apply it to L and R inputs simultaneously. If the AVR is set with Center Channel ON, any Stereo or Surround mode that I can think of will send that signal to Center Channel ONLY.


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## RapalloAV (Aug 5, 2009)

AudiocRaver said:


> I do not know your complete configuration, so this is partially guesswork.
> 
> Sounds like you are going into your AVR via analog, not HDMI. You can use a RCA-F to dual RCA-M adapter to take the test signal and apply it to L and R inputs simultaneously. If the AVR is set with Center Channel ON, any Stereo or Surround mode that I can think of will send that signal to Center Channel ONLY.


I am using L+R RCA in puts on the front panel of the 8802, then to an RCA Y splitter into the PC with XTZ loaded. Without PLXII I cant get just the centre channel alone to measure it. My old AVR had PLXII and I was able to separate just the centre channel.

I use Stereo out of the 8802 for measuring. All I can get is L+R or L+R+C combined, no way can I get centre channel only, I just wish I could find a way. In the menu I can turn off the centre channel, but you cant turn off L+R and just leave the centre ON.

Its very difficult on the new models that don't have PLXII.


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## willis7469 (Jan 31, 2014)

If you can get LRC. Why not unhook L and R an sweep then?


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## Todd Anderson (Jul 24, 2009)

Great thread... I think I'll be measuring and tweaking today! ;-)


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## RapalloAV (Aug 5, 2009)

willis7469 said:


> If you can get LRC. Why not unhook L and R an sweep then?


What do you mean?


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## AudiocRaver (Jun 6, 2012)

Disconnect the L & R speaker cables so only the center channel is connected to the AVR, just when you are ready to take Center channel measurements., . It is a bit of a pain, but should do the trick.


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## RapalloAV (Aug 5, 2009)

AudiocRaver said:


> Disconnect the L & R speaker cables so only the center channel is connected to the AVR, just when you are ready to take Center channel measurements., . It is a bit of a pain, but should do the trick.


Ok now I get it. It is a mammoth as I cant get to the speakers as they are behind a AT screen. To get to the rear of the 8802 is also a biggie as I have to pull out the rack, but that's doable. Shame I had the rack out yesterday, would have been great to do it then. :sneeky:

Anyway good idea, next time I have to remove the rack at least I now have a method for measuring just the centre channel.onder:

So under Marks method of just measuring centre channel only for mains/sub integration its very simple...
Change sub distance until you get the smoothest response at the crossover, is that correct?


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## AudiocRaver (Jun 6, 2012)

Yep, you got it.

Note for future tweaking. Accessibility is a good quality in equipment, connections, etc my PC lies on its side on top of a desktop so I can have it open and be inside it in seconds. But that's me. A little bit of accessibility can be really nice even with an AVR and speaker connections. Nothing is permanent. Ever.


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## willis7469 (Jan 31, 2014)

AudiocRaver said:


> Disconnect the L & R speaker cables so only the center channel is connected to the AVR, just when you are ready to take Center channel measurements., . It is a bit of a pain, but should do the trick.


 yep. That's what I meant.


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