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Author Topic: DSP setup  (Read 15675 times)

Merlijn van Veen

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Re: DSP setup
« Reply #60 on: March 17, 2016, 01:32:56 pm »


So you have to ask yourself-What do I want to accomplish with THIS particular measurement?

+1

The analyzer doesn't lie, you just have to ask the right question.


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Nathan Riddle

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Re: DSP setup
« Reply #61 on: March 17, 2016, 01:51:08 pm »

+1

The analyzer doesn't lie, you just have to ask the right question.


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So given that I dont care about anything other than 40-200hz did I do things right?

I think my results say I do. The LF extension down to 30hz I wasn't super concerned with because I know if I throw 35hz sine wave it's going to shake the 'room' regardless of what trace I'm currently getting. And I don't care about the HF because the srx sounds fine by itself. Just wanted to get xover region working well and to my ears...they do.
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Scott Carneval

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Re: DSP setup
« Reply #62 on: March 17, 2016, 04:42:38 pm »

So given that I dont care about anything other than 40-200hz did I do things right?

I think my results say I do. The LF extension down to 30hz I wasn't super concerned with because I know if I throw 35hz sine wave it's going to shake the 'room' regardless of what trace I'm currently getting. And I don't care about the HF because the srx sounds fine by itself. Just wanted to get xover region working well and to my ears...they do.

If it sounds better, then hopefully you got it aligned properly through the crossover region. If you can do the measurement again, and capture a trace of the top and then a trace of the sub separately, then lay them on top of each other, we can tell a lot more.

When you said the mic was out of the pattern of the top, I had this vision of the two speakers being really far apart and the mic was over by the sub, which would have rendered any 'alignment' useless except at that position. But it looks like you did things properly. At 35' away from the speaker there's no way that mic was out of the pattern of the horn just by being on the ground. And the horn doesn't extend to 400hz, and even if it did it would not have pattern control that low, so I'm not sure why your magnitude trace had a big hole in it. 

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Ivan Beaver

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Re: DSP setup
« Reply #63 on: March 17, 2016, 05:25:24 pm »

+1

The analyzer doesn't lie, you just have to ask the right question.


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Exactly.  It WILL give the correct answer-for the mic position and parameters entered.

If you don't enter the correct parameters it will not give an ACCURATE answer-but it will be "correct".
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Nathan Riddle

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Re: DSP setup
« Reply #64 on: March 21, 2016, 11:54:03 pm »

So at my event I was able to re-measure. Though it was indoors not outdoors.

Have at it. i have no idea why the 181 needed 43ms of delay... perhaps dsp?

Event was a huge success. I was super pleased with the SRX & TH118; loved the limiter settings you suggested Ivan, really helped keep things safe as I had a stand in sound guy who loved to run things into clipping on the output of the board (QU24) (totally unnecessary, I thought it was too loud most of the time; and we asked him to lower the volume a bit and he did...for a little while....ugh) , but the SRX/TH118 happily limited and said 'whatever.'
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Tim McCulloch

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Re: DSP setup
« Reply #65 on: March 22, 2016, 02:21:49 am »

I think you need to zoom in on the Impulse Response.

With the delay being much greater than you anticipated, why do you think the result is correct?
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Ivan Beaver

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Re: DSP setup
« Reply #66 on: March 22, 2016, 06:58:55 am »

So at my event I was able to re-measure. Though it was indoors not outdoors.

Have at it. i have no idea why the 181 needed 43ms of delay... perhaps dsp?

Event was a huge success. I was super pleased with the SRX & TH118; loved the limiter settings you suggested Ivan, really helped keep things safe as I had a stand in sound guy who loved to run things into clipping on the output of the board (QU24) (totally unnecessary, I thought it was too loud most of the time; and we asked him to lower the volume a bit and he did...for a little while....ugh) , but the SRX/TH118 happily limited and said 'whatever.'
I know you were mostly interested in the sub response, but putting a mic in a pressure zone on carpet is worthless for the top end.

It needs to be on a large (2x2 minimum) area that is hard.

Glass works well.

If you are not going to do that, then just lay it on the ground for the sub alignment, and don't worry about getting a HF ground plane.
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Nathan Riddle

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Re: DSP setup
« Reply #67 on: March 22, 2016, 10:27:20 am »

With the delay being much greater than you anticipated, why do you think the result is correct?

No phase wrapping was my largest indicator. I don't know what to look for, but that seemed logical. Additionally, any other delay setting (I changed it excessively) ended up with lots of phase wrapping.

I know you were mostly interested in the sub response, but putting a mic in a pressure zone on carpet is worthless for the top end.

It needs to be on a large (2x2 minimum) area that is hard.

Glass works well.

If you are not going to do that, then just lay it on the ground for the sub alignment, and don't worry about getting a HF ground plane.

Oh, well that makes sense. I was primarily going along to this guide as far as the ground plane measurement:
http://www2.dbxpro.com/forum/viewtopic.php?f=60&t=2908

I thought the position would matter for bass frequencies as well and I didn't think about the carpet as not being a hard plane since it is that super thin on top of concrete carpet, but hf's are so small...duh should have occurred to me.


For those curious.
I know the stack is slightly strange, but I did it for a few reasons (in no particular order):

To obtain more height for the SRX and maintaining coupling between the SRX/TH118 for xover region.
To experiment with the BR18/TH18 phase matching combinations.
To experiment with directivity of the subs/mains.
To see about the tactile vibrations through the floor and how it impacts recognized

I knew there was enough rig for the gig (~300 middle schoolers) [perhaps not with the way the guy mixed...  :-\ ] so I wasn't concerned with extracting every last db out of the system.

Overall I was super pleased with the setup. Mains were kept off of walls; subs were more focused in the middle alley where people would be instead of walls/stage. Slightly less volume where the mix position was which could have contributed to running things hotter, but it was loud and full nearly everywhere in the room ~(70'W x 150'L).
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Ivan Beaver

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Re: DSP setup
« Reply #68 on: March 24, 2016, 07:48:37 am »


I thought the position would matter for bass frequencies as well and I didn't think about the carpet as not being a hard plane since it is that super thin on top of concrete carpet, but hf's are so small...duh should have occurred to me.



It is not a matter of a hard plane or not-but rather a matter of the size of the wavelength of interest (highest freq) vs the size of the reflective distance.

At low freq you have a lot more "freedom", but at high freq millimeters count.

There is a REASON that Crown and other PZM type mic manufacturers put the element so close to the reflective boundary.  And that is to catch the HF well.

With everything audio (especially speakers and mics) you have think in terms of freq, and ask yourself "At what freq".

All sorts of answers will change when you ask yourself that question.  Such as "what is the coverage pattern",
"How loud is it",  "how well do the cabinets array" and so forth.

You will get DIFFERENT answers to the SAME question, when you change the freq part of it.

But that only matters if you want a REAL answer ;) and not some general BS answer
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Ivan Beaver
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Re: DSP setup
« Reply #68 on: March 24, 2016, 07:48:37 am »


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