Active system time alignment

[paulspencer]

I've been experimenting with time alignment with an active 3 way speaker and DCX. Dome tweeter + 6.5" mid in a sealed box with an angled front baffle sitting on top of a 12" Rythmik sub each side.

Using DCX auto align I get interesting delay settings! Run the routine twice and it does things slightly differently. One time it might invert polarity on a particular channel, the next time it might not, but compensate with delay differently. This is without any other changes.

Here is a typical setting:

Mid and top both delayed by 20 ms (7.8m), both with inverted polarity, then the mid has 718mm and the top 672mm delay.

Another try:

No inverted polarity but the same delay to the mid + top, 300mm to the mid and 338 to the tweeter.

Just curious what kind of settings others are finding.

As I don't fully trust the auto settings, I'm going to measure for myself when I get the time.

Without any delay settings in place, the tweeter needs polarity reversal.

[Paul W]

Haven't used auto-align for several years, but I do remember erratic behavior if the acoustic levels were not high enough. Perhaps crank it up a bit and see if results become more consistent.

[doug20]

Im not sure this helps and I never was succesful with my DCX auto align stuff but I used this site as a reference.

Auto-align for dummies

[Pano]

Yes, read the link Doug provided. It will help.

I've had weird stuff happen, too, but usually it's spot on.

[JamesTRexx]

Originally Posted by Paul W

Haven't used auto-align for several years, but I do remember erratic behavior if the acoustic levels were not high enough. Perhaps crank it up a bit and see if results become more consistent.

I think that just might be it. I've only had slight differences in outcome and always used the auto alignment with enough volume.

I think it's best to run auto once with just polarity, once with only delay, and once with both and then decide which one to use.

[Radugazon]

In the manual, Behringer himself says that Auto-Align works in most of the cases...only ! This is targeting the PA world for fast settings only.

So, the best is to forget this and get familiar with a good (free...) soft, as Arta, that displays clearly impulse and step. Learning this tool is a long curve but you gonna get paid back.

feel free to mail me if you want more details, as how to get this...

[doug20]

Could you provide a "dummies" version on how to use ARTA for figuring out alignment issues?

[Radugazon]

maybe this can help ?

[454Casull]

Were I to do it (never did before), I would do a bit of basic trig and get the hypotenuses of the listening triangles between listening position and each driver, pick a reference, and then subtract horizontal distances from the hypotenuses to yield traveling distance difference and then just divide by c.

Tweak after that, but that should get you pretty close.

My 2 cents

[gainphile]

The easiest way to time align:

- Measure from 1m at the design axis, ideally freespace/outdoor of course
- Reverse the tweeter output/connection
- change the delay until deepest null is observed (pink noise is helpful here but impulse also ok)
- Reverse back the tweeter