Time Alignment in Car via Impulse Response - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 51 Old 09-09-14, 11:41 AM
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Re: Time Alignment in Car via Impulse Response

Both channels drivers need to be the same. The 2 MR the same and the 2 TWs the same polarity. The relative polarity can be reversed for MRs Vs the TWs though. Just select the setting that gives the best SPL response. There may not be much advantage either way in this case however - just guessing.

I don't think you will learn much from the phase chart due to the various reflections. Moving the window range slightly make the phase tracking look very different. There is no clear way that I found to suggesting one setting is correct or even clearly better than the other. I would rely in the SPL chart to decide.
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post #12 of 51 Old 09-09-14, 08:24 PM Thread Starter
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Re: Time Alignment in Car via Impulse Response

Just spent an hour listening to the system after applying the delays from my latest measurements. I can happily report that we have achieved the best imaging my system has presented yet. Many thanks!

I did not have to invert any of the drivers' polarity. I tried inverting the left midbass, but that killed the center image.

I did invert the subwoofer by 180 degrees, and then delayed it by about 3 ms. The bass is now well anchored in the front of the soundstage.


Here are some new measurements after the delays were applied. The impulses line up almost exactly as predicted before.
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Time Alignment in Car via Impulse Response-ir-delays.jpg  

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post #13 of 51 Old 09-10-14, 05:04 AM
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Re: Time Alignment in Car via Impulse Response

Good Job!
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post #14 of 51 Old 09-11-14, 12:35 PM
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Re: Time Alignment in Car via Impulse Response

If that was mine I'd swap the phase of the 2 MB elements or the others (either would work) to get everyone moving the same way (Positive or Negative) out of the gate. May not be noticeable due to the difference in the impulse waveforms but I'd be inclined to try anyway.

Just my $.02

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post #15 of 51 Old 09-11-14, 06:06 PM Thread Starter
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Re: Time Alignment in Car via Impulse Response

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If that was mine I'd swap the phase of the 2 MB elements or the others (either would work) to get everyone moving the same way (Positive or Negative) out of the gate. May not be noticeable due to the difference in the impulse waveforms but I'd be inclined to try anyway.

Just my $.02

GCG
OK, I'll give that a try after the weekend.
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post #16 of 51 Old 09-22-14, 03:20 AM Thread Starter
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Re: Time Alignment in Car via Impulse Response

Quote:
GCG wrote: View Post
If that was mine I'd swap the phase of the 2 MB elements or the others (either would work) to get everyone moving the same way (Positive or Negative) out of the gate. May not be noticeable due to the difference in the impulse waveforms but I'd be inclined to try anyway.

Just my $.02

GCG
Thanks for the tip. You were correct. I measured my response, and then inverted the phase on the horns and measured again. I got better SPL support through the crossover range with the inverted horns.
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post #17 of 51 Old 09-22-14, 03:24 AM Thread Starter
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Re: Time Alignment in Car via Impulse Response

I have another question about this topic...


When recording a measurement for the impulse response in order to determine time alignment, should we use a full range sweep? Or is it ok to limit the sweep range to an area closer to crossover point?

For example, if my midbass and horns are crossed over at 800 Hz, is it ok to sweep from 400 Hz - 1600 Hz?
Or is 20 Hz - 20,000 Hz still preferred?
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post #18 of 51 Old 09-22-14, 07:52 AM
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Re: Time Alignment in Car via Impulse Response

Yes, a narrower range should work as well.
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post #19 of 51 Old 09-28-14, 05:24 PM Thread Starter
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Re: Time Alignment in Car via Impulse Response

Should IR measurements for time alignment be done before or after EQ and X-over are set?

I was trying another go at this today but I couldn't get very good IR measurements. I had done my EQ and X-over settings first this time. Previously, the measurements for time alignment were done first before EQ and X-over.
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post #20 of 51 Old 09-28-14, 08:42 PM
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Re: Time Alignment in Car via Impulse Response

The XO changes the delay. EQ around the XO range impacts the delay a little also.

I'd suggest; set the desired XO filters, adjust the driver levels, adjust the delay, and then EQ.
It's a good Idea to confirm the delay is still good after EQ.

For additional delay adjustment after the initial setup just leave the EQ on.

That's my approach. It's the end result that counts so order is not required.
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