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post #1 of 7 (permalink) Old 02-24-2013, 02:01 AM Thread Starter
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Advanced Tuning Procedures

So along with my active processing comes learning how to harness what my system is really capable of. I knew it got complicated, but wow.

To tune I picked up a Dayton EMM-6 measurement microphone (comes with calibration file) and a Micport Pro USB interface. Now I can turn any laptop into an advanced Real Time Analysis machine.

There are a lot of software options to choose from though. TrueRTA is a simple to use one that you can use a free version or pay for upgrades to higher resolution versions. I tinkered with it, but decided to tackle the more advanced options.

I'm working with REW right now, which stands for Room EQ Wizard. It's an incredibly powerful tool built to do a heck of a lot more than car audio tasks, but that also means there is more to learn to navigate the software. One of the coolest parts though is that they partnered with the company that makes my sound processor. It can run an Auto EQ function to tune to a curve and export the parametric filters to the sound processor. I haven't gotten this working yet though. Even without that I could still use the software to measure and EQ to a curve manually, then manually enter the results into the DSP.

Alright, those are the tools I'll be using, now I'll make the next post my process I'll be following.



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post #2 of 7 (permalink) Old 02-24-2013, 10:57 AM
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Re: Advanced Tuning Procedures

Wow, cool. This will be fun to read about... Going to move into home theater audio at some point?
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post #3 of 7 (permalink) Old 02-24-2013, 01:38 PM Thread Starter
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Wow, cool. This will be fun to read about... Going to move into home theater audio at some point?
I'm sure I will, but money is a factor. I already have way too many hobbies to fund.
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post #4 of 7 (permalink) Old 02-25-2013, 01:23 AM
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Ah - that's when you just do it for other folks. hehehehe That ends up funding said hobbies.
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post #5 of 7 (permalink) Old 03-03-2013, 06:44 AM Thread Starter
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So I had my original second post all typed out when I started this thread but it was lost in a failed load. That's not all bad though because I'm still researching this part.

For my tuning I'm going to separate the discussion into two parts. One is all about what to do with the EQ power of the DSP, and that is where I still have a lot of questions to figure out.

The other part is using my measurement set up to get all the drivers to work together successfully. I'm going to talk about that part here first.

When I want a response graph of any part of my system I'll be using a pink noise generator and the RTA functions of my software. The first round of this is going to be to get a set of measurements for each driver individually. I'm doing this for the sake of mapping out it's actual response in my environment which at this point I just want to use to get a good idea of ideal crossover points. It should go without saying that for the sake of determining crossover points I need to set my crossovers during testing to points beyond where I'd consider crossing drivers but before limits of the driver that would be problematic.

Once I'm happy with my crossover points I'll probably re test the measurements under these conditions for the drivers just to double check that it's working as intended, but otherwise I'm going to put away the frequency response measurements and graphs for now.

This step is all about time alignment and phase. My specific procedures for how I'll achieve this aren't determined just yet. I'm going to have to stumble through both figuring out the software as well as my process for a while, but I know what my goals are.

I want drivers that are working together to create the same channel of sound to be in phase at the crossover points. I also want everything time aligned so that it's arriving at my ears at the correct time. You can't just set phase before time aligning though because that'll all get blown out of the water the second we touch the TA settings. You need to figure out the TA first and then tweak phase.

In order to make these adjustments I need to be able to measure timing differences, so this is where the pink noise doesn't work. I need some kind of pulse, tone, or even certain music where I can measure the same note coming in from different drivers. I'll have to play with my software a lot more before I know how I'll get those timing measurements. Music is something you could use with some ingenuity if you couldn't generate the signals from the computer you're measuring off of. Think about it this way. You could use a note from a separate driver like a sub as a timing reference to the other drivers, at least in theory I that's how I think you'd do it. Luckily my source unit is my computer anyways so I can directly generate the sounds from my measurement software.

I'll leave it at this point for now. There isn't a lot of debate over what I'm going for here, just getting all the different components of the sound system working together. My only real challenge here is in determining how to measure. We hear with two points on the sides of our heads, so are we TAing so that the L channel hits the L ear at the same time as the R channel hits the R ear? I would think so, but what about phase between left and right? We could end up with something that sounds right individually but when playing both channels together has weird effects. I need to do some more reading up on this but in the end I might just have to start experimenting.



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post #6 of 7 (permalink) Old 03-03-2013, 05:25 PM
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I think that there is a good point for phase timing and fixing it mathematically - but we aren't logic units - we humans are analog - we have feelings, and opinions...

I think you'll find that since we have two ears, and both ears here both channels at slightly different phases and times, that trying to chase it down that way will become problematic. I have the feeling you can use the software to get you close, then sit in the car and decide how much you like it - then drive one option all the way to one end, and test - then the other end of the dial and test, then re-set it to software and see where you like it better.

I have the feeling it will be more akin to measuring for eye-glasses than measuring for cabinets... "Tell me which is better - this one, or this one? 1, or 2? 1, or 2? Now 2, or 3?"
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post #7 of 7 (permalink) Old 03-03-2013, 05:35 PM Thread Starter
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I think that there is a good point for phase timing and fixing it mathematically - but we aren't logic units - we humans are analog - we have feelings, and opinions...

I think you'll find that since we have two ears, and both ears here both channels at slightly different phases and times, that trying to chase it down that way will become problematic. I have the feeling you can use the software to get you close, then sit in the car and decide how much you like it - then drive one option all the way to one end, and test - then the other end of the dial and test, then re-set it to software and see where you like it better.

I have the feeling it will be more akin to measuring for eye-glasses than measuring for cabinets... "Tell me which is better - this one, or this one? 1, or 2? 1, or 2? Now 2, or 3?"
There are scientific answers to these questions, just not answers I have. The question is about how our brain perceives sounds. We can perceive from timing and volume changes when a sound comes from one side, hits that ear first, then arrives at the opposing ear.

From what I understand I can just tune each channel to each ear's location and our brain will take care of the rest. The exception to that will be if the reflections create weird cancellations that would require tweaking the set up.

You are right that there will be a lot of testing like the eye glasses analogy. Such is the nature of tuning. Eventually I'll have a better ear for these things which will help immensly.



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