# time alignment - cm vs ms



## joshchrans (Mar 11, 2012)

Lets say we are comparing 2 HU's with time delay. Assuming one shows time alignment in "ms" and the other does in "cm", am I correct in thinking that the closest speaker in the "ms" senario would have the highest "number" on the display, and in the "cm" senario, the farthest speaker would have the highest "number"?

The reason I ask, is I'd like to do the time alignment procedure where I physically reverse the individual speaker polarity, adjust TA for weak or thin sound, correct the speaker polarity, and move on to the next one. IE Sub ---> Pass Midbass ----> Driver Midbass ---> Pass Tweet ---> Driver Tweet. My HU had the "cm" measurement, so this tells me I have to start the procedure with the closest speaker? IE, reverse of the above senario.

I tried simply measuring the distances from my nose in the listening position to each driver, and adjusting the TA setting to that measurement, but this did not create good results.

FYI I am running an active 2 way front + sub


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## Justin Zazzi (May 28, 2012)

joshchrans said:


> Lets say we are comparing 2 HU's with time delay. Assuming one shows time alignment in "ms" and the other does in "cm", am I correct in thinking that the closest speaker in the "ms" senario would have the highest "number" on the display, and in the "cm" senario, the farthest speaker would have the highest "number"?


An interesting guess, but no. It is more likely the measurements are Milliseconds (ms) and Centimeters (cm). One is a measure of time, and the other is distance. The nearest speaker to your ear should have the largest value when using time alignment, and the furthest speaker should have a value of zero. For example a subwoofer in the trunk should have 0.0ms and the left tweeter in an a-pillar should have the largest value if it is the closest (a couple ms or so).



joshchrans said:


> The reason I ask, is I'd like to do the time alignment procedure where I physically reverse the individual speaker polarity, adjust TA for weak or thin sound, correct the speaker polarity, and move on to the next one. IE Sub ---> Pass Midbass ----> Driver Midbass ---> Pass Tweet ---> Driver Tweet. My HU had the "cm" measurement, so this tells me I have to start the procedure with the closest speaker? IE, reverse of the above senario.


Time alignment will be most noticable between the sub and your two midbass drivers assuming they are crossed over at about 1khz or higher. Having these three drivers be time aligned is what you want to accomplish, and setting your subwoofer crossover as high as it will go or off will make this easier when using the method you describe. Start with the subwoofer at a delay of 0.0 (assuming it is the furthest from your head) and slowly add some delay to the others.



joshchrans said:


> I tried simply measuring the distances from my nose in the listening position to each driver, and adjusting the TA setting to that measurement, but this did not create good results.


This is an alternative method to above and will get you close, then you can fine tune using the method above. Keep the subwoofer time delay at zero forever though, and adjust the two midbass driver delays only.

Measure the three distances from the sub and your midbass drivers to your head in centimeters. Then starting with your passenger midbass, subtract it's distance from the sub distance, and use this as the value for Centimeters (cm) for the passenger midbass delay. You want to input the difference in distance using centimeters.

Also to convert between milliseconds and centimeters, you can use these conversions for waves traveling at the speed of sound:
1ms = 34cm
0.1ms = 3.4cm

and
1 inch = 2.54cm

Clear as mud?


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## LBaudio (Jan 9, 2009)

it is just not clear to me who the hell had idea to use cm as the units for TA....time is measured in seconds and not in meters/cm....ahhh,.....still have to wait 4meters to go to the coffee, and after a couple of kilometers I'll go home......

somebody wanted to make everything idiot proof, but it turned out it is more confusing......


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## sqnut (Dec 24, 2009)

To the OP.

Pio's do TA in cm/inches. It's not an issue. Just measure the distances and enter the values. Granted that it won't be your final setting, but it would be fairly close. Basically time alignment is allowing sound from speakers that are at different distances to arrive at your ears together. Or at least to the point where the differences in arrival times is lesser than what your brain can process. In this case, the brain localizes the source of sound as from the front. TA is about getting the sound to start looking and feeling right. Of course it won't sound right and sounds will be jumping around. That's not what TA is about. All you want from TA is the sense that although the speakers are to your side and behind you the sound presentation is from the front. 

Getting it to sound right is a FR issue. Yes, your nearest driver would have the lowest distance value and the highest ms time value.


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## MarkZ (Dec 5, 2005)

LBaudio said:


> it is just not clear to me who the hell had idea to use cm as the units for TA....time is measured in seconds and not in meters/cm....ahhh,.....still have to wait 4meters to go to the coffee, and after a couple of kilometers I'll go home......
> 
> somebody wanted to make everything idiot proof, but it turned out it is more confusing......


How is it confusing? I think it's probably the more useful unit of measurement, considering that MOST people set time alignment with a measuring tape. We're the oddballs doing it other ways.


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## [email protected] (Jun 12, 2008)

I thought to obtain the MS setting, it was a formula that involved a distance measurement.


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## joshchrans (Mar 11, 2012)

I'm still a bit confused. My deck displays ta in cm. why would I set the sub at 0? Is the ta was in ms, I understand why I would. Since its in cm, the sub would have the highest number, being the farthest driver from the listening position. Using this logic, the closest driver would have the smallest number. Makes me think that when I adjust the ta on the sub, it's actually making the adjustment to all other speakers, and not the sub.. Unless its advancing the subs signal and not delaying it. Make sense?


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## tima4h (Jul 17, 2011)

I think it also depends on the head unit, and what processing it does. For my head unit (DRZ9255) you set each speakers distance from your ears, and the head unit processor then calculates their relative distance to point zero (your head). Other units expect the closest to be zero, and others again expect the furthest to be zero. As your unit is a Clarion, it may work the same as mine. when you INCREASE the distance on a speaker, it advances the signal, as the speaker is further away.


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## Justin Zazzi (May 28, 2012)

tima4h thank you for that! I didn't realize Clarions work this way. It's a great feature actually, and saves some headache so you don't have to do conversions and whatnot.

joshchrans it sounds like you should use the absolute distance between your head and each speaker (in centimeters) without any subtraction or other math like I suggested above. That should get you close to where you want to be, then use the pink noise technique you mentioned to dial it in a little more.

good luck!


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## LBaudio (Jan 9, 2009)

MarkZ said:


> How is it confusing? I think it's probably the more useful unit of measurement, considering that MOST people set time alignment with a measuring tape. We're the oddballs doing it other ways.


it is much much easyer to me to imagine Ta in ms....I exacly know how to manage the parameters.......
Measuring type and TA just dont work for me, Im using software and specific tracks to set correct delay for every speaker in system, and this way I also see what is going on with phase (0-180).....the second alternative to seting ta is with pink noise and Dopler effect, but it is not so acurate as first procedure.


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## MarkZ (Dec 5, 2005)

I don't think either procedure is very accurate, personally.  You're using phase to estimate delay. I measure delay directly. THAT'S accurate. I think a tape measure is a good approximation though.


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## Justin Zazzi (May 28, 2012)

MarkZ said:


> I don't think either procedure is very accurate, personally.  You're using phase to estimate delay. I measure delay directly. THAT'S accurate. I think a tape measure is a good approximation though.


Mark I enjoy your posts.

I assume you use a tool to measure the delay between the first direct wave arriving from each channel when playing a chirp? Then you use this to set your time delay on your processor or head unit, right? I don't know of many free tools that do this, but RoomEQ Wizard does (I love that program! and also want to understand more of it)

Do you also mean that you measure or correct phase separately from time delay? (I mean other than switching polarity of the speaker terminals). Further adjustment of absolute phase seems somewhat possible at low frequencies, but at midrange frequencies the wavelengths are so short it would be nearly impossible to get a perfect phase-response, no? Also I'm not sure what tool would be useful to adjust phase vs frequency. Maybe I'm reading too deep between the lines.


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## MarkZ (Dec 5, 2005)

Jazzi said:


> Mark I enjoy your posts.
> 
> I assume you use a tool to measure the delay between the first direct wave arriving from each channel when playing a chirp? Then you use this to set your time delay on your processor or head unit, right? I don't know of many free tools that do this, but RoomEQ Wizard does (I love that program! and also want to understand more of it)


I use my own, but that's cool that RoomEQ Wizard does it. I haven't checked that program out yet.



> Do you also mean that you measure or correct phase separately from time delay? (I mean other than switching polarity of the speaker terminals). Further adjustment of absolute phase seems somewhat possible at low frequencies, but at midrange frequencies the wavelengths are so short it would be nearly impossible to get a perfect phase-response, no? Also I'm not sure what tool would be useful to adjust phase vs frequency. Maybe I'm reading too deep between the lines.


Yeah, I wasn't really talking about correcting for phase... you can let your FR dictate what you need to do there. I was making the comment that this technique of time alignment seems prone to what I guess can be called "false positives". There are certain suboptimal delays where you'll hear cancellation, depending on what the energy content of your test signal is. 

I haven't tried it this way. But you're right, you can only use it at low frequencies.


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## ledvedder (Oct 24, 2012)

Is this correct that Clarion units just use the distance from your head to each speaker? I thought it was that the farthest speaker is 0 cm, and all other speakers are (distance to farthest speaker - distance to the speaker you are setting). Therefore, the speaker closest to you will have the greatest cm setting. Is this the wrong way to do this? This stuff is so confusing.


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## strakele (Mar 2, 2009)

The fact that different companies have T/A done differently in their head units/processors definitely makes things confusing.

But since you basically just have 2 options, why not try both? And then whichever sounds better, there's your answer.

Units that display time delay in milliseconds - it's just that... a higher number is more delay, so the speaker that's closest to you will have the highest delay number in milliseconds.

Units that display time delay in in/cm/some kind of distance - it's USUALLY asking for the difference in distance between the speaker you are delaying and the farthest speaker from you. ALL distances will be relative to the furthest speaker. If your sub is the furthest, and your left tweet is the closest, the sub will have 0cm, and the tweet will have the highest measurement number, since the difference in distance between it and the farthest speaker from you is the greatest.

Some units that use distance, like the P99 and apparently at least some of the Clarion units, make it easier on you by simply asking for the distance between you and all of the speakers, and then doing the calculations for you. I'd guess that your Clarion unit works this way if some of the others do - I can't imagine them using different systems in their products.

But basically, try it both ways. Even with rough measurements, one should sound pretty decent and one should be way off.


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## theoldguy (Nov 17, 2009)

it seems like every unique manufacturer has a method of time delay that differs from one another. My eclipse uses milliseconds that involves a mathematical formula outlined in the users manual. My H701 I believe also uses milliseconds, but the formula is slightly different. I could be remembering wrong, but I believe one of them is distance from the driver and the other is distance from the furthest speaker. Basically it just boils down to conforming to the method of the head unit you currently have.


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## fcarpio (Apr 29, 2008)

No formula needed for ear time alignment.


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## sqnut (Dec 24, 2009)

It's not that tough.

*1. If you are setting TA in ms: * Measure the distance to each driver from your seating position. Set the furthest driver to 0. Now calculate the difference in distance between the furthest driver and the one you want to TA. Eg Near mid 37", sub 74" for a difference of 37".

1 ms = 13.50"
1 ms = 34.3 cm

0.1 ms = 1.35" or 3.43cm. This was mentioned earlier in the thread. Now set each speaker based on this. Done

*2. If you're TA in inches:* 

a. Measure the distance to each driver and enter the value.
b. If for some reason you want to set your sub to 0, then calculate the difference and enter those values.

Over a period of time you will do it by ear, but this is good way to start.


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