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Old 05-26-2014   #51
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Default Re: First-timers guide to measuring your system

Hanatsu. Thank you. Please Provide a Pay Pal DONATE Link for your time, experience, and effort in putting this together. This information, as presented here in a step-by-step guide, is worth at least as much as the DSPs we use in our systems to make these adjustments and corrections.
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Old 05-26-2014   #52
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Default Re: First-timers guide to measuring your system

So I have just spent about 2 or 3 hours trying to to use REW for time alignment measurements, and I'm completely lost. I've printed out the instructions from the link at the beginning of this thread, but for the life of me I can't figure out how to do this.

I have a Behringer ECM8000, connected with XLR cable to a phantom Power device, and then into the Mic input on my mixer/USB sound card. I know that I have the output from the soundcard playing correctly on my Car stereo because I can hear the test sweeps/shite noise tests. And I know that I have the microphone connected properly because it is detecting and measuring the signals played over the Car stereo. But I can't get the loopback working, or I don't know how to get the loopback working.
I'm kicking myself because I have a degree in physics but I can't figure this out.

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Old 05-26-2014   #53
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Do the soundcard got ASIO support? I might have to return to the T/A issue later to provide an alternitive way to do it without the use of 'loopback'... Thanks for the kind words everyone btw

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Old 05-27-2014   #54
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Default Re: First-timers guide to measuring your system

Quote:
Originally Posted by subterFUSE View Post
So I have just spent about 2 or 3 hours trying to to use REW for time alignment measurements, and I'm completely lost. I've printed out the instructions from the link at the beginning of this thread, but for the life of me I can't figure out how to do this.

I have a Behringer ECM8000, connected with XLR cable to a phantom Power device, and then into the Mic input on my mixer/USB sound card. I know that I have the output from the soundcard playing correctly on my Car stereo because I can hear the test sweeps/shite noise tests. And I know that I have the microphone connected properly because it is detecting and measuring the signals played over the Car stereo. But I can't get the loopback working, or I don't know how to get the loopback working.
I'm kicking myself because I have a degree in physics but I can't figure this out.
You might have to go through and try a bunch of options under the soundcard tab to get things working. You might get a "clipping detected on the reference channel" error, or "signal too low" error because the software thinks it's listening for the sine sweep in that channel and not the reference signal it's getting. I know that the clipping error is OK, as I get it when I'm testing. I've never gotten the "signal too low" error, but that might be fine too if you're still getting reliable impulse readings. This is all assuming you have the capability to use a loopback with the soundcard.

If you can't use a loopback, you can use HolmImpulse. It uses a clocked "stream" that is uninterrupted between measurements. In this way it can't give you absolute impulse, but it can give you comparative impulse between two signals. It's trickier in that the order you measure the speakers in matters, and you can't run any memory-intensive applications while using it or you'll interrupt the stream, but I'll let Hanatsu take care of explaining it, lol.

If it comes down to it you can buy a super inexpensive non-calibrated mic and use it without the external card just for impulse response.

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Originally Posted by Orion525iT View Post
Beyond the technical aspects, there are things with which only the individual can find value, regardless of outcome. There are some things to which the process has more value than the end result .
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Old 05-27-2014   #55
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Default Re: First-timers guide to measuring your system

Quote:
Originally Posted by Hanatsu View Post
Do the soundcard got ASIO support? I might have to return to the T/A issue later to provide an alternitive way to do it without the use of 'loopback'... Thanks for the kind words everyone btw

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Yes, I've got ASIO and I'm using those drivers in the Prefs.

I have the output playing on channel 2 on my mixer/soundcard, which corresponds to soundcard channels 3 & 4.
I'm using the Record output from the mixer that uses RCA cables. The RCA cables go into my Car and plug into the RCA input on my head unit. The microphone is on a stand in the driver seat, with the mic in the approx center of head position. The mic is a Behringer ECM8000, with XLR cable going into a phantom Power device and then into the Mic input on my mixer, which is on channel 1. CH1 = soundcard channels 1 & 2.

In the soundcard routing, I have set mixer channel 3 (SC channels 5 & 6) to receive the Record output. This should effectively be the same thing as running a cable from the Record output back into mixer channel 3. It's just done via the soundcard routing instead of by a cable.

I know that I have the output working correctly because I can hear the signals being generated playing on my Car stereo. I also know that I have the microphone connected and routed properly because it is recording the signals.
The level tests all come back OK.

I just can't tell if I have the loopback working or not. How do I tell if the loopback is working?

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Old 05-27-2014   #56
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Default Re: First-timers guide to measuring your system

Make sure you check the box labeled "Use loopback as timing reference" under the "Analysis" tab. Take a measurement of one Speaker with the mic in one position. Move the mic into the backseat or wherever. Take another measurement of the same Speaker Compare impulse response to see if it has changed in a reasonable way. If you moved the mic 2 feet back, you should get an impulse peak that's about 1.8ms after the first one (2/1100 =0.0018 seconds).

Quote:
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Beyond the technical aspects, there are things with which only the individual can find value, regardless of outcome. There are some things to which the process has more value than the end result .
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Old 05-27-2014   #57
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Default Re: First-timers guide to measuring your system

Thanks for the help. I did have the loopback button selected.

I am actually thinking I might have had it done correctly last night, but just didn't understand how to read the charts.

I'll try again tonight when I get home.

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Old 05-28-2014   #58
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Default Re: First-timers guide to measuring your system

Sorry guys for not updating. I was in a traffic incident yesterday morning, I hurt my foot and left leg pretty bad. There will be a few days before I'm released from hospital, hope you'll have patience heh

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Old 05-28-2014   #59
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Default Re: First-timers guide to measuring your system

moved to the tutorials section annnnnnnnnnnnnnnnnnnddddd...... STICKIED!

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Old 05-28-2014   #60
 
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Default Re: First-timers guide to measuring your system

Quote:
Originally Posted by Hanatsu View Post
Sorry guys for not updating. I was in a traffic incident yesterday morning, I hurt my foot and left leg pretty bad. There will be a few days before I'm released from hospital, hope you'll have patience heh
Take care sire and get well soon.
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Old 05-28-2014   #61
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Default Re: First-timers guide to measuring your system

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Sorry guys for not updating. I was in a traffic incident yesterday morning, I hurt my foot and left leg pretty bad. There will be a few days before I'm released from hospital, hope you'll have patience heh
Wow! Sorry to hear. Hope it's not too bad, and you'll be getting well fast.

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Old 05-28-2014   #62
 
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Default Re: First-timers guide to measuring your system

Hope it is just bumps and bruises. Get well soon and take your time, sorry to hear you got into an accident.
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Old 05-28-2014   #63
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Default Re: First-timers guide to measuring your system

So I am about to go and start getting the equipment hooked up so I can try another go at this with REW.

Wish me luck.

Working in my favor, I already finished half a bottle of Sancerre. The remaining half is still beckoning.

I discovered this morning that my Audison BitOne DRC controller has decided to present an interesting challenge to complicate things for me. (See attachment)

Any suggestions? Perhaps a toothpick and some chewing gum?
Attached Images
File Type: jpg photo.JPG (109.2 KB, 221 views)

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Old 05-28-2014   #64
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Default Re: First-timers guide to measuring your system

Quote:
Originally Posted by subterFUSE View Post
I discovered this morning that my Audison BitOne DRC controller has decided to present an interesting challenge to complicate things for me. (See attachment)

Any suggestions? Perhaps a toothpick and some chewing gum?
Bummer. Shop Vac? Kids dart gun "bullet" with suction cup? LOL!


HANATSU! Hope it isn't too serious. Hang in there and get well!
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Old 05-29-2014   #65
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Default Re: First-timers guide to measuring your system

I think I got REW working this morning, but I'm still not certain. So I took some pics of the measurements I made and hopefully someone here can help?
I just can't tell if I have the loopback reference working properly.

Here are the midbass drivers. I muted all drivers but one at a time and measured. Microphone in drivers seat at center of head position.


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Old 05-29-2014   #66
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Default Re: First-timers guide to measuring your system


Quote:
Originally Posted by Hanatsu View Post
Microphone measurement technique

<snip>

!! AVERAGE THE MEASUREMENTS FROM THESE POINTS AS DESCRIBED IN MY LAST POST !!

Why 5/3 ratio for the left side and 6/2 ratio for the right side?

I believe this is due more "hearing crosstalk" left side, the Speaker is more in front of us and also closer to both ears. The listening tests confirm that this is the "best" way to average (IME).

Pro-tip: Use a battery charger while measuring / tuning. Your battery will thank you
Gary Summers showed me a neat setup he has for his Mercedes. It's basically an array of microphones in an aluminum jig. By using a jig he can insure that the mic is in the same place, every time.

It would be fairly simple to Build a box that could allow one to 'turn on' each mic, one by one, so that you could do your measurements without even getting up to move the mic. Taken a step further, the software itself would do the switching between the array of mics, but I've never seen any software that can do that. (I use the free stuff, Arta and HolmImpulse.)

In principle it would be quite simple to waste the surplus labour of the world by building temples and pyramids, by digging holes and filling them up again, or even by producing vast quantities of goods and then setting fire to them. (Orwell)
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Old 05-29-2014   #67
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Default Re: First-timers guide to measuring your system

Quote:
Originally Posted by subterFUSE View Post
So I have just spent about 2 or 3 hours trying to to use REW for time alignment measurements, and I'm completely lost. I've printed out the instructions from the link at the beginning of this thread, but for the life of me I can't figure out how to do this.

I have a Behringer ECM8000, connected with XLR cable to a phantom Power device, and then into the Mic input on my mixer/USB sound card. I know that I have the output from the soundcard playing correctly on my Car stereo because I can hear the test sweeps/shite noise tests. And I know that I have the microphone connected properly because it is detecting and measuring the signals played over the Car stereo. But I can't get the loopback working, or I don't know how to get the loopback working.
I'm kicking myself because I have a degree in physics but I can't figure this out.
This is Windows right?
Usually the reason that the loopback doesn't work is that stupid Microsoft Windows has the input of the soundcard set to mono. When this happens, one of two things occurs:

1) one channel is muted, so your loopback no worky
2) or the left channel is duplicated to the right channel, so your loopback no worky

Right click on the properties of the Speaker icon in Windows, select input, go to the properties and set it to "44.1khz stereo" (default is mono.)

This same stupid problem screws up measurements in HolmImpulse, Arta, Dayton Woofer Tester, and on and on and on


In principle it would be quite simple to waste the surplus labour of the world by building temples and pyramids, by digging holes and filling them up again, or even by producing vast quantities of goods and then setting fire to them. (Orwell)
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Old 05-29-2014   #68
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Default Re: First-timers guide to measuring your system

Quote:
Originally Posted by subterFUSE View Post
So I am about to go and start getting the equipment hooked up so I can try another go at this with REW.

Wish me luck.

Working in my favor, I already finished half a bottle of Sancerre. The remaining half is still beckoning.

I discovered this morning that my Audison BitOne DRC controller has decided to present an interesting challenge to complicate things for me. (See attachment)

Any suggestions? Perhaps a toothpick and some chewing gum?
Blu Tak.

In principle it would be quite simple to waste the surplus labour of the world by building temples and pyramids, by digging holes and filling them up again, or even by producing vast quantities of goods and then setting fire to them. (Orwell)
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Old 05-29-2014   #69
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Default Re: First-timers guide to measuring your system

Quote:
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Gary Summers showed me a neat setup he has for his Mercedes. It's basically an array of microphones in an aluminum jig. By using a jig he can insure that the mic is in the same place, every time.

It would be fairly simple to Build a box that could allow one to 'turn on' each mic, one by one, so that you could do your measurements without even getting up to move the mic. Taken a step further, the software itself would do the switching between the array of mics, but I've never seen any software that can do that. (I use the free stuff, Arta and HolmImpulse.)
he actually posted a picture of that somewhere... I don't remember where, but I seem to recall him posting it a couple years ago. maybe I'm wrong... wouldn't be the 2nd time.


That said, I don't think that's necessary, really. it's cool. but overkill, IMO. and it sure wouldn't be cheap or easy. the whole reason you're doing it is for accuracy, correct? well, what about accuracy of the mic? you're gonna have to load multiple cal files or have all mics measure exactly the same. that's a whole lotta work for what I feel would be no gain. Just my $.02 on it, though.

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Old 05-29-2014   #70
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Default Re: First-timers guide to measuring your system

Quote:
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he actually posted a picture of that somewhere... I don't remember where, but I seem to recall him posting it a couple years ago. maybe I'm wrong... wouldn't be the 2nd time.


That said, I don't think that's necessary, really. it's cool. but overkill, IMO. and it sure wouldn't be cheap or easy. the whole reason you're doing it is for accuracy, correct? well, what about accuracy of the mic? you're gonna have to load multiple cal files or have all mics measure exactly the same. that's a whole lotta work for what I feel would be no gain. Just my $.02 on it, though.
whoah I couldn't disagree more strongly.
A measurement at a single point in a Car is virtually useless.
There are so many reflections, if you rely on a single data point your measurement is virtually worthless.

When measuring in the car, I use one of two options:

1) measure the system at multiple points and average the measurements (basically what Hanatsu is doing)

or

2) measure the speakers outside of the car


I generally start with option 2, then move to option one once I'm happy with the outside measurement.

As far as accuracy of the mic goes, I think that the dips and peaks caused by the Car swamp any dips and peaks inherent to the mic. If you look at a typical calibration file the adjustments are usually along the lines of about +/- one decibel, whereas a single reflection in a car can create a 20dB dip.


In principle it would be quite simple to waste the surplus labour of the world by building temples and pyramids, by digging holes and filling them up again, or even by producing vast quantities of goods and then setting fire to them. (Orwell)
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Old 05-29-2014   #71
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Default Re: First-timers guide to measuring your system

whoa, yourself there, big fella.

I've been 'preaching' spatial averaging for years now:
Using the RTA for tuning: The importance of spatial averaging

What I'm saying is I don't think there's a legitimate enough benefit in having 6 mics set up at the same time with a duplex switcher for the array on top of having to worry about the calibration of each. Using REW and a high number of averages while sitting in the Car with the mic is my preferred method. And it's extremely accurate as long as the location is in the same area, given the high number of data samples the software is obtaining and averaging on the fly.

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Old 05-29-2014   #72
 
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Default Re: First-timers guide to measuring your system

Quote:
Originally Posted by Hanatsu View Post
Microphone measurement technique

If you look in a manual of an auto-tune DSP or ask 10 different 'experts' I'm sure you get different answers every time. I will present my technique here, in my experience, it has worked best in those systems I've installed. I've sort of 'back engineered' this technique via comprehensive listening tests...

So how do you place your microphone while measuring?

Good question! Sit in the car, hold the microphone as the pictures below describe. Run one sweep in RoomEQ for EACH POINT. 8 sweeps in total for each individual speaker. Hold the microphone still while running the sweep and make sure the microphone doesn't hit your head or anything.

FOR SUBWOOFER MEASUREMENTS, A SINGLE MICROPHONE PLACEMENT IS ENOUGH. PLACE IT IN THE MIDDLE OF THE HEADREST OR IN FRONT OF YOUR HEAD (you don't even need to be in the Car for this one)

- As I said before, measure in a quiet area.
- Measure at moderate/"normal listening" volume ~90dB or so.
- Use hearing protection if you want, the sweep is annoying to listen to.







!! AVERAGE THE MEASUREMENTS FROM THESE POINTS AS DESCRIBED IN MY LAST POST !!

Why 5/3 ratio for the left side and 6/2 ratio for the right side?

I believe this is due more "hearing crosstalk" left side, the Speaker is more in front of us and also closer to both ears. The listening tests confirm that this is the "best" way to average (IME).

Pro-tip: Use a battery charger while measuring / tuning. Your battery will thank you
I take it the 5/3 and 6/2 ratios are for a left hand drive Car and that for a right hand drive car (or passenger seat measurements if you were so inclined) you would reverse these?

As regards spacial averaging, I haven't been able to read through the other thread yet, but would I be right in thinking we might want to repeat the measurements after EQing and determine whether the response (averaged across those same locations) was now more uniform or whether we needed to make further adjustments, and if this were the case it would be beneficial to have a means of using the same locations as we used originally. Whether this needs to be a jig of some kind or multiple microphones is a point worthy of more discussions, although I would be biased towards the simplest (and cheapest) solution and introduce the minimum number of variables by using the same microphone and calibration file throughout, as it introduces less chance of error from using the wrong calibration curve with a given microphone.
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Old 05-29-2014   #73
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Default Re: First-timers guide to measuring your system

Who managed to get Bruce Willis to pose for that diagram pic?

Talk about some serious connections....

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Old 05-29-2014   #74
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Default Re: First-timers guide to measuring your system

Quote:
Originally Posted by Patrick Bateman View Post


This is Windows right?
Usually the reason that the loopback doesn't work is that stupid Microsoft Windows has the input of the soundcard set to mono. When this happens, one of two things occurs:

1) one channel is muted, so your loopback no worky
2) or the left channel is duplicated to the right channel, so your loopback no worky

Right click on the properties of the Speaker icon in Windows, select input, go to the properties and set it to "44.1khz stereo" (default is mono.)

This same stupid problem screws up measurements in HolmImpulse, Arta, Dayton Woofer Tester, and on and on and on

Yes, I'm using Windows because when I tried using my MacBook Pro it seemed that REW doesn't like the CoreAudio drivers. My mixer driver was not showing up as an option in the Preferences. But with my PC, I got the ASIO drivers working just fine.

I will check the Windows mono issue tomorrow, but I'm skeptical about this being the issue.
Besides, REW doesn't actually reference any of the inputs/outputs in stereo. They are all mono references because it only allows one input or output selection at a time. On my mixer, separate Inputs "1 & 2" are the same as channel 1 L/R on my mixer. 3 & 4 = CH2 L/R.
I'm trying to handle the loopback via the USB soundcard's internal routing. Not using a cable because that should be unnecessary with my mixer. (Allen & Heath Xone DB4) I know that the mixer I am using it WAY more advanced that what is needed for REW, but I didn't feel like buying more equipment when this should theoretically work just fine.

Actually, I think I had it working this morning. I just don't really know how to confirm whether or not the loopback is working or not? See my previous post with my midbass measurements. Maybe someone can determine from the pics?

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Last edited by subterFUSE; 05-29-2014 at 08:19 PM..
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Old 05-29-2014   #75
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Default Re: First-timers guide to measuring your system

^^^Are your measurements (on the X axis) in milliseconds or meters? I've never gotten a measurement in the 200's range. Other than that it looks like a normal impulse response. Do you have the driver in blue wired in reverse polarity?

Quote:
Originally Posted by Orion525iT View Post
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