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Author Topic: Delay in speaker management  (Read 5062 times)

Too Tall (Curtis H. List)

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Re: Delay in speaker management
« Reply #20 on: December 26, 2007, 03:43:21 pm »

Dick Rees wrote on Mon, 24 December 2007 11:10


Thanks for your response.

Yes, the thought that time alignment would vary within the sound field had occurred to me.  The question we both have is the function of the passive crossover in driver alignment within the cabinet.  

Probably best to go direct to EV on that unless someone else logs in with the answer.

As to phase issues:  How does a typical (if there is "typical") speaker management system handle that?  If it's in the PDF manuals I must be missing it.

As to the 1/3 octave graphic:  My FOH EQ rack is a Klark DN360B along with a Klark DN410 parametric, so the ability to set narrower filters already exists.  I also occasionally use a Sbaine GraphiQ.  I find that I like the analog parametric better for this reason:  You can sweep the filters and tune them by ear in real time whereas with the digital unit I have you must either use the FBX auto filter setting (albeit in "manual" mode) or guesstimate the frequencey, dial it in and then hit "enter" (running off a laptop).

So it looks like the critical issue here is the phase coherency.  How are these adjustments best made?  If I run something like Smaart or Spectrfoo I'll see the results, but how do I make the corrections?

Thanks in advance.

If you use a passive xover odds are there will not be any flat delay for time alignment in the xover design. There are too many problems associated with doing that type of thing.

For time alignment you are usually looking at “flat” delay where the amount of time delay is the same at every frequency. If you have a Driverack you dial up how much digital delay you need to line the baffle mounted woofer to the deeper horn on your compression driver.
This is the same as physically moving the woofer back into the cabinet. Of course if you do that you need to put some kind of wave guide on the woofer so the sound does not bounce back and forth between the side walls.
Before DSP this is how it was done. To this day it is still better to “fix it at the source” when you design a speaker box.

What any xover MUST do is match up the phase response in the xover region.
This is time delay that changes with frequency. This is something that can easily be done with a passive analog or a DSP.

One of the biggest complication is passive xovers are effected by impedance, while active (analog or digital) are not. It makes it easier to design the filter for active.

To wrap up the topic it is possible to create flat delay with passive components. You see this in some old studio monitors like the Westlake coax.
In most cases they do not go through the trouble except for coax drivers and usually not for PA duty.

Too Tall
        Curtis H. List    
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