alpine’s time correction

Previously posted by Kadetheus:

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i recently bought an alpine cda-9813 hu and i get everything just fine but the time correction. maybe because i haven't had enough time to quite understand it. but i have a ford contour and i was wondering if anyone just off the top of their head had a clue as to what my time correction should be set to for the FL,FR,RL, and RR speakers.

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I have the same HU. 

Differences in speaker placement in the car create shift in sound image.  Time correction tries to balance the time it takes for the sound to come to the listener by delaying the audio signal to the listener. To set these settings for your unit you need to measure the distance of the farthest speaker to your head and the rest of the speakers. I take my Mazda Protege5 as an example.

My farthest speaker (from the speaker to my head) is the FR which is 2.25m.

My Front Left speaker to my head is measured 1.75M.

My Rear Left speaker to my head is about 1.25M

My Rear Right speaker to my head is about 2M.

So my settings for time correction are:

FR = 0

FL = (2.25 -1.75) / 343 x 1000 = 1.457 rounded up to  1.5

RL = ( 2.25. - 1.25 ) /343 x 1000 = 2.915 rounded down to 2.9

RR = ( 2.2.5 - 2.00 ) /343 x 1000 = 0.729 rounded down to  0.7

Hope this example helps.

Theoratically, you should take it into consideration and you should find the shortest distance possible, mind you there are many possibilities sound  coming from a Rear Right speaker mounted on the door, bounching many places and eventualy arriving in your ears.

IMO however, you do not have to do that just measure the distance as if the seats were not there.

Morever the 343 m/s is the sound speed at 20 C only, The sound speed will vary depending on the temperature at which it travels.

That is why a tape measure will be of little use to set the time correction settings in Alpine HU.

Now if you had the Alpine 9815, you could preset and record these time correction settings to 6 preset buttons. That way you could set time correction according to different seasons. The  9813 does not have this feature.

Previously posted by Kadetheus:

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thanks dudes. what the speed of sound at about 95 degrees?

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First  convert Fahrenheit to Celcius:

C = (F-32) * 5 / 9   = (95-32) * 5 / 9 = 35 º C

Once the temperature in Celcius is known we can find sound speed/velocity with this formula:

V = 331.5 + (0.6 T)

Where:  V = velocity (m/s) and  T = air temperature (°C).

Thus, sound velocity at 95 °F or 35°C is:

V = 331.5 + (0.6 * 35 ) = 352.5

Hope this helps.

Just a FYI on Alpines web site there is a i-Personalize link that will allow you to select your head unit and input the distance from each speaker to your selected listening point and it will give you all the time correction settings to input into you head unit. I hope this helps a bit more.