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Discussion Starter #1
I am trying to 'optimize' the performance of my main speakers by phase aligning the drivers. System is actively crossed as follows.
Top end is an Oris horn with Tang Band 8" driver crossed at 204hz using L/R 24db xover, covering 204hz-20kHz.
Next is 15" woofer open baffle crossed from 102hz-204hz using L/R 24db xover.
Bottom end is an actively controlled subwoofer 20hz-102hz using L/R 24db xover.

My goal is to wring out the very last bit of performance by phase aligning the Oris and 15" woofer, which are located very close, one on top of the other.
Questions are:
Where should I place the mic for proper testing? Near speakers, or at LP?
I am assuming I run the sweeps with the appropriate xovers in place. If so, does each driver get the sweep run from 20hz-20khz?

In playing with this, I noticed that if I truncate the sweep around the xover region, the time delay changes for the drivers.

Hopefully the questions aren't confusing.
 

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There have been some good older threads on this, e.g. https://www.hometheatershack.com/forums/rew-forum/60600-tutorial-good-time-alignement-group-delay-phase.html and https://www.hometheatershack.com/forums/rew-forum/65840-impulse-aligned-vs-phase-aligned.html

The group delay plot can be helpful in aligning drivers.

Measure full range, or at least well beyond the range of the driver, otherwise the reduced range of the sweep creates an artificial truncation of the response which is akin to having a very sharp low pass filter cascaded with the system, with its corresponding phase shift and group delay.
 

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Discussion Starter #3

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If you are measuring individual drivers distance isn't that critical, as long as it is the same for all. If measuring with both drivers active would want to be far enough away for them to integrate properly, but 1m is common.
 

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Discussion Starter #5

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Hi Rudy,
When I did my system I measured all drivers at 1 meter first to know what the speakers are doing, then I measured from the LP to see what the room was doing to the sound.
 

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Hi Rudy,
Yes:
  • For drivers mounted on the same baffle a 0.05-1.5 m mic distance from the baffle is a good choice. Since your speakers look pretty large I suggest something in the range of 1-1.5 m would be best. The height of the mic should be on, or close to, the line of sight from the LP to the horn to this case. [A mic positioned at the LP can work, but room effects can sometimes make the job more confusing.] If the SW is near the main speaker being measured, then the same mic location can be used for the SW timing as well. For a SW placed well away from the main, it is required to place the mic at the LP for the main to SW timing. We can just deal with the additional difficulty in analysis.

  • All 3 XO's must be active for each individual driver measurement.

  • Use the same full range sweep for each driver measurement. Full range means the range that the overall system is designed to handle. Do not push the low end or top end higher than the speaker system is designed to handle. 20-20k would be good for your setup.
There are various ways to determine the delay timing needed between the driver pairs. I can provide support for the method I use.
 
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