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Delays and limitors

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Aidanphillips145 View Drop Down
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    Posted: 05 October 2018 at 1:28pm
Excuse me if these questions are pretty newbie, Ive just ordered some mt121's to be built to go on top of my 2x mogale super scoops loaded with void v1000 and my 2x hd15 loaded with fane 15xb. I've been trying to read up in many places and search this forum so thought I would make a post instead, how do I set the delays to time allign my system using a berry ultradrive? Is there an equation or something that I need to follow, I think it's something to do with the horn lengths.
Next question, I believe I have my limitors set but after a party we i did a week ago my pro line was clipping ever so slightly, so I kept bringing the out put gain down till there was no clipping (down to about -12db) does this sound about right? The bass was there just not as much as it has been in previous party's. Quite a difficulty stopping eager dj's that justvwant to crank all the gains up on the mixer, any help would be greatly appreciated. Thanks
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 05 October 2018 at 2:02pm
Hi Aidan, welcome to the forum :)

To set delays, the best technique for a beginner is the test tone and phase flip method.

The point of setting delays is to make sure that where one driver takes over from another at the acoustic crossover point, they are both perfectly in phase. When this is true, the two drivers' outputs will sum perfectly and the level of that crossover frequency will increase when they are both turned on. You can see then, that if they are perfectly *out* of phase (180 degrees out), they will *cancel* perfectly, and when they are both turned on the level of the crossover frequency will decrease. This is easier to hear than the level increase. Digital crossovers have polarity-flip functions (=180 degree phase flip). So, you make use of that.

So, you start by establishing the basic polarity relationship between the two drivers you are trying to align. Play a test tone at the crossover frequency you have set in the crossover, through both drivers, at about the same acoustic level. Is it louder with one driver out of phase, or louder with them both in phase? That becomes your starting point. Set the polarity flips for the loudest tone.

Then, find the acoustic crossover point. Set the crossover and amp levels to approximately what they will be when you're running the rig. Now sweep the test tone up and down while alternately muting each driver. Find the frequency where they both seem to be playing approximately the same level. This is the acoustic crossover point.

Now, make an educated guess about which driver will need to have delay applied. It is normally the one on the shortest horn - so, in your case, the 15" of the HD15, and then the 12" of the MT121, and then the tweeter. The scoop won't need any delay. 

With the acoustic crossover tone playing, reverse the phase of this driver from where it was in step 1. The tone should decrease in loudness. Now, activate and start winding on delay. The tone should continue to decrease in loudness. At some point it will reach a minimum and start getting louder again. Wind back until you get to the quietest point. Take your time to find the sweet spot where it almost disappears completely.

Now flip the phase back to where it was in step 1. The tone should become very loud. You have successfully time-aligned the two drivers.

Repeat from step 1 for the 12" to the 15", but leave the 15" polarity set where it is. Same for the tweeter to the 12". 

Hope this helps :) oh and the limiters won't stop a Proline from clipping unless you wind them all the way down to -22dBFS. The limiter range isn't much use, you might want to use inline -10dB pads between DCX and amps to allow more adjustment of it.
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Aidanphillips145 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aidanphillips145 Quote  Post ReplyReply Direct Link To This Post Posted: 05 October 2018 at 2:14pm
Awesome thanks man, I'll give this ago once there up and running. Cheers 👍
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 05 October 2018 at 2:48pm
Originally posted by studio45 studio45 wrote:

Hi Aidan, welcome to the forum :)

To set delays, the best technique for a beginner is the test tone and phase flip method.

The point of setting delays is to make sure that where one driver takes over from another at the acoustic crossover point, they are both perfectly in phase. When this is true, the two drivers' outputs will sum perfectly and the level of that crossover frequency will increase when they are both turned on. You can see then, that if they are perfectly *out* of phase (180 degrees out), they will *cancel* perfectly, and when they are both turned on the level of the crossover frequency will decrease. This is easier to hear than the level increase. Digital crossovers have polarity-flip functions (=180 degree phase flip). So, you make use of that.

So, you start by establishing the basic polarity relationship between the two drivers you are trying to align. Play a test tone at the crossover frequency you have set in the crossover, through both drivers, at about the same acoustic level. Is it louder with one driver out of phase, or louder with them both in phase? That becomes your starting point. Set the polarity flips for the loudest tone.

Then, find the acoustic crossover point. Set the crossover and amp levels to approximately what they will be when you're running the rig. Now sweep the test tone up and down while alternately muting each driver. Find the frequency where they both seem to be playing approximately the same level. This is the acoustic crossover point.

Now, make an educated guess about which driver will need to have delay applied. It is normally the one on the shortest horn - so, in your case, the 15" of the HD15, and then the 12" of the MT121, and then the tweeter. The scoop won't need any delay. 

With the acoustic crossover tone playing, reverse the phase of this driver from where it was in step 1. The tone should decrease in loudness. Now, activate and start winding on delay. The tone should continue to decrease in loudness. At some point it will reach a minimum and start getting louder again. Wind back until you get to the quietest point. Take your time to find the sweet spot where it almost disappears completely.

Now flip the phase back to where it was in step 1. The tone should become very loud. You have successfully time-aligned the two drivers.

Repeat from step 1 for the 12" to the 15", but leave the 15" polarity set where it is. Same for the tweeter to the 12". 

Hope this helps :) oh and the limiters won't stop a Proline from clipping unless you wind them all the way down to -22dBFS. The limiter range isn't much use, you might want to use inline -10dB pads between DCX and amps to allow more adjustment of it.


if the delay is more than one wavelength of the crossover frequency it is possible to get the speakers in phase but still out of time. there is an auto-delay setting on an ultradrive which SOMETIMES give sensible results. also you can set the ultradrive to work in distance rather than time to make it easier. the delays should roughly correspond to the path length differences.
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toastyghost View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 06 October 2018 at 5:32pm
Yep, you can be a lap behind and that's really, really bad. Also you're flipping POLARITY not phase.

And use Bink's warbles, not a sine wave. How much music is just a single sine wave?

Shortest horn is also WRONG. It's not about horn length. It's about frequency vs group delay.

Edited by toastyghost - 06 October 2018 at 5:32pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pasi Quote  Post ReplyReply Direct Link To This Post Posted: 07 October 2018 at 8:40am
Originally posted by toastyghost toastyghost wrote:

Yep, you can be a lap behind and that's really, really bad. Also you're flipping POLARITY not phase.

And use Bink's warbles, not a sine wave. How much music is just a single sine wave?

Shortest horn is also WRONG. It's not about horn length. It's about frequency vs group delay.


I'm so proud of you. Young one has learned so much over these years. Kids. They grow up so fast nowadays :)

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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 09 October 2018 at 9:31pm
Originally posted by toastyghost toastyghost wrote:

Yep, you can be a lap behind and that's really, really bad. Also you're flipping POLARITY not phase.

That's true, but application of common sense should tell you if the delay you're applying is unreasonably large. For example if you are trying to line up a HD15 to a Super and end up applying several metres worth of delay to the HD15, you would realise your mistake and start again. With any two other cabs, you might think to try delaying the other one, in case your assumption about which one would need delay was wrong (see below)

Originally posted by toastyghost toastyghost wrote:

And use Bink's warbles, not a sine wave. How much music is just a single sine wave?

I've genuinely never heard of a Bink's warble and would probably have thought it was a species of small bird. Educate me?

Originally posted by toastyghost toastyghost wrote:

Shortest horn is also WRONG. It's not about horn length. It's about frequency vs group delay.

In the context of a purely horn-loaded system such as the OP described, assuming a shorter horn will require delay to line up with a longer horn is not WRONG. Sure it won't end up being delayed *exactly* to the difference in horn length, because of group delay (and of course the HD15 has more of that because of its bandpass nature). But it's a perfectly sensible assumption to start from. If the OP had described a mixed reflex/horn system or was using ported horns, then the situation would not be as clear-cut.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 10 October 2018 at 5:05pm
Originally posted by studio45 studio45 wrote:

Originally posted by toastyghost toastyghost wrote:

And use Bink's warbles, not a sine wave. How much music is just a single sine wave?

I've genuinely never heard of a Bink's warble and would probably have thought it was a species of small bird. Educate me?

Michael "Bink" Knowles was an active poster on the original LAB in the 1990's & early 2000's.
He was very generous in putting together a set of test tracks on a CD for PA optimisation that he distributed for free - remembering that this was before the days when everyone and their dog had a computer in their pocket.
Several of the tracks were sweeps that covered about half an octave either side of several of the typical sub-top crossover points, to be used exactly as Toasty is saying - it's better to hear what's going on either side of the crossover than only at that one exact frequency.

Herewith the three warbles that were on the CD:

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