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Author Topic: Phase trace  (Read 6978 times)

Johnny Diaz

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Phase trace
« on: October 26, 2011, 08:32:42 pm »

I took another measurement of the top and sub. Does it look like they are in phase? Also, I'm using 1/12 Oct for Phase Smooth and Mag Smooth and 8 for averaging is this ok? The steps that I'm taking to take these measurements is as follows;

1. Click find. Once it finds the delay insert it.
2. Unmute the left top. Take TF. Capture TF and stop.
3. Mute Left top. Leave delay as is. Unmute left sub. Take TF. Capture Tf. Now add delay to one of the speakers and see where the phase shift goes.
4. Perform 1-3 on the right side speakers.

Is this correct so far? Any recommendations?

Johnny
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Paul Tucci

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Re: Phase trace
« Reply #1 on: October 26, 2011, 10:52:01 pm »

Johnny,
Your technique is valid. Capturing a TF of the full range box and storing it gives you a target for the sub. NOT CHANGING the offset delay is critical. You need to look at both boxes from the same perspective in time. By manipulating the arrival time of the sub via its own processor leaves the measurement perspective unchanged. Here's a suggestion though. The area of interest in your example here is below 200Hz ish. Matching the phase traces of the area of interest is always easier if you zoom in and fill your display with the bandwidth of interest. A bigger display will make this process easier.

I've been wanting to customize my dispay, how did you get that pretty orange band on the top?

Tucci
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Johnny Diaz

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Re: Phase trace
« Reply #2 on: October 26, 2011, 11:01:03 pm »

Johnny,
Your technique is valid. Capturing a TF of the full range box and storing it gives you a target for the sub. NOT CHANGING the offset delay is critical. You need to look at both boxes from the same perspective in time. By manipulating the arrival time of the sub via its own processor leaves the measurement perspective unchanged. Here's a suggestion though. The area of interest in your example here is below 200Hz ish. Matching the phase traces of the area of interest is always easier if you zoom in and fill your display with the bandwidth of interest. A bigger display will make this process easier.

I've been wanting to customize my dispay, how did you get that pretty orange band on the top?

Tucci


Paul,

Thanks. Would I zoom in with the Phase smooth?  I'm a newbie with Smaart.  I think you know how to get the pretty orange band:) 

Johnny
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Mac Kerr

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Re: Phase trace
« Reply #3 on: October 26, 2011, 11:10:01 pm »

I've been wanting to customize my dispay, how did you get that pretty orange band on the top?

Tucci

I also like the orange band, but I'm pretty sure it indicates the demo version.

Mac
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Paul Tucci

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Re: Phase trace
« Reply #4 on: October 26, 2011, 11:11:09 pm »

To zoom in...right click and highlight the area you want to fill the display. Make sure to grab enough frequency bandwidth (left / right) and amplitude ( up / down) to see what you need to see.

Tucci
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Timo Beckman

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Re: Phase trace
« Reply #5 on: October 27, 2011, 03:54:30 am »

The method is valid . The only thing i can see is a problem @ about 100Hz .
You can see the jump in the phase trace @ about 100Hz .
What's your x-over point and the filters being used ?
You can see wich speaker needs delay by looking at the angles of the phase trace . If the top has a less steeper angle than the subs the top needs delay and vice versa .
After aligning the angles of the tf sub and top you might find that you need to reverse polarity .
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Adam Black

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Re: Phase trace
« Reply #6 on: October 27, 2011, 09:27:07 am »

how did you get that pretty orange band on the top?

The orange cursor readout area indicates that it's the demo build.
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Johnny Diaz

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Re: Phase trace
« Reply #7 on: October 27, 2011, 12:52:34 pm »

The method is valid . The only thing i can see is a problem @ about 100Hz .
You can see the jump in the phase trace @ about 100Hz .
What's your x-over point and the filters being used ?
You can see wich speaker needs delay by looking at the angles of the phase trace . If the top has a less steeper angle than the subs the top needs delay and vice versa .
After aligning the angles of the tf sub and top you might find that you need to reverse polarity .

Timo,

I have the top's hipass at 45Hz, lopass at 20khz with bw24 slope and the sub's hipass at 45hz, lopass at 88hz with bw24.  I forgot of change the tops hipass to 88hz.  I will do that soon and report back. 

Since I will have the hipass on top's at 80hz should I discard data below 80hz and vice versa?  Also, I have the subs lopass at 88hz bw24 but Smaart is still showing me data in the phase trace well above 88hz like in the 2k-4k region.  How is it getting this data?

Johnny
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Johnny Diaz

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Re: Phase trace
« Reply #8 on: October 27, 2011, 12:53:29 pm »

The orange cursor readout area indicates that it's the demo build.

Yup I have the demo installed.  Saving up to purchase. 
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Timo Beckman

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Re: Phase trace
« Reply #9 on: October 27, 2011, 02:54:17 pm »

Timo,

I have the top's hipass at 45Hz, lopass at 20khz with bw24 slope and the sub's hipass at 45hz, lopass at 88hz with bw24.  I forgot of change the tops hipass to 88hz.  I will do that soon and report back. 

Since I will have the hipass on top's at 80hz should I discard data below 80hz and vice versa?  Also, I have the subs lopass at 88hz bw24 but Smaart is still showing me data in the phase trace well above 88hz like in the 2k-4k region.  How is it getting this data?

Johnny

If you take a look at the frequency response of the top (solo) you should be able to see the roll off of the top (without the high-pass filter) . What you should look for is the point where it drops -6db . A wild gues about 125Hz . If you put a 24 db filter @ that frequency that becomes the low-pass frequency for the sub . The 24db/oct filter @ 125Hz means that at about 63Hz the level has dropped with 24db . If you get the phase traces of them both to overlap at a large area around the x-over point you get addition and more headroom . Because of the level your using on the sub The overlap zone is larger so you need to check from 60 to about 150 Hz .
You can see the bump @ 100Hz in the phase & frequency response wich is a indication that a 180dg phase difference excists between the top and sub at that point .

2nd Watchout using butterworth filters . If you put that filter in to use at 125Hz the -6db point is not at 125Hz but at a different point and the addition of the filter combination at 125Hz is not 0db but a littlebit more . If you want to go for flat reponse and at the frequency you set as the x-over point you need to use Linkwitz rilley 24 db/oct .

You might try with less steeper filters so 12 or 18db/oct but they have there own carracteristics .
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ProSoundWeb Community

Re: Phase trace
« Reply #9 on: October 27, 2011, 02:54:17 pm »


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