Rational Acoustics



prapol
April 18th, 2013, 06:52 AM
Dear all

Just wonder I try to measure between Sub and fullrange. The Transfer Function I use can get direct sound from fullrange but can not get direct sound from Sub. how can I do or where can I set something else. thank you very much indeed.

Prapol

Harry Brill Jr.
April 19th, 2013, 04:03 AM
Measure full range. Find and insert delay. Capture trace. Mute full range. Turn on sub. Adjust sub delay in processor until phase trace angle where sub overlaps full range is the same. If the angle is the same and the phase trace overlap you are done. If they won't overlap, invert polarity of subs and adjust delay of dsp for sub until the phase trace does overlap the phase of the full range.

prapol
April 19th, 2013, 04:35 AM
Measure full range. Find and insert delay. Capture trace. Mute full range. Turn on sub. Adjust sub delay in processor until phase trace angle where sub overlaps full range is the same. If the angle is the same and the phase trace overlap you are done. If they won't overlap, invert polarity of subs and adjust delay of dsp for sub until the phase trace does overlap the phase of the full range.

Dear Harry

I use Transfer function and i can find fullrange time and capture trace but for SUB i can not find time. Do i have set somthing else.

Timo Beckman
April 19th, 2013, 02:39 PM
You won't find the time on the sub because it's stretched in time due to the wave length/period of the sub .
Smaart in most cases will not find a peak because there is not enough data in the sub region to synchronize on .

You have to synchronize on the full range and then use the same time you have on that to measure the sub .
After that you have to phase align the sub to the mid high's via delay and get the phase trace angle of the sub to match the trace angle of the full range trace in the x-over zone .
It's the same awnser as harry gave you by the way

Harry Brill Jr.
April 19th, 2013, 03:16 PM
Dear Harry

I use Transfer function and i can find fullrange time and capture trace but for SUB i can not find time. Do i have set somthing else.


I don't recall anywhere in my posting telling you to "FIND" the sub time! Read again what I said. Once you have captured the Full Range Trace you do not touch the time in Smaart again. Leave it alone. Adjust the delay time setting in your sub's DSP output until the phase trace has the same angle.....uhg, I feel like I said this already in the other post....

Harry Brill Jr.
April 19th, 2013, 03:30 PM
[/QUOTE]684 Try this! I created this document several years ago. It's taken from an old forum post. The original traces were attached to the post. I opened them and took snap shots. Unfortunately this was not the old post I was looking for but it does contain much of the information. There was quite a long thread where I learned to phase align subs 2-3 years before I learned how to read the phase trace which was not until hosting a class in early 2003. It really doesn't matter how long you've been using it. If you have never taken a class you are cheating yourself.

prapol
April 24th, 2013, 11:28 AM
Dear Harry

Thank you very much indeed for your kindness.

Prapol

Harry Brill Jr.
May 9th, 2013, 12:15 PM
http://www.rationalacoustics.com/forums/images/icons/icon1.png Re: multiple measurment
This is best kept on the forum because you will get answers with different points of view. When you MOVE your mic, you should reset the delay time IN SMAART. THis is the delay on the REFERENCE channel. You should time your subs where you want them to be in time. For me this is where the most people are. You cannot have them timed perfectly in every seat. It's impossible. The closest you can come is if your subs and mains are all together very close to each other. The mic location for timing my subs is usually about 2/3rds of the way into the audience. I'm trying to please "most" of the people. I place the mic on the floor for this measurement. It helps clean up the phase trace which is affected by the reflection from the floor. If you put your mic on the floor, there is no reflection at low frequencies.

http://www.rationalacoustics.com/forums/concept9/misc/quote_icon.png Originally Posted by prapol
Dear Harry

First of all I have to apologize if I disturb you. If I want to measure multiple point of PA system lets say :

1 I measure 25 meter away from the PA ( L ) got delay time and do align with Sub by capture trace in transfer function
2 If I move the mic to FOH let say 35 meter away from PA ( L ) do I have to redo a delay time again or keep the previous delay I measure at 1st time. Thank you very much indeed for your kindness.

Best wishes

Prapol







Harry Brill Jr.
proaudioguy "at" tigeraudioinc.com

Timo Beckman
August 5th, 2013, 01:50 AM
@prapol
I have to correct myself . It's possible for smaart to synchronize on a sub .
It's via the Impulse response option within smaart7 .
699

Within the ir settings bar on the right side of the screen choose a large FFT size so 32K/682ms or higher and 16 (or more) averages .
Get your self a cup of coffee and when you're back smaart will give you a time on where to find the sub you are measuring (so this takes some time:-).
copy the time from the ir measurement manually in to the transfer screen .

You can see the the phase/frequency response of the sub but it's not going to help you to align it to the tops (not if you do not know how to interpret the data) .
For that you have to synchronize on the tops and match the phase trace of the subs with the tops as described in the earlier posts .
You can however use it for something like a end fired sub array/csa/gradient or what ever kind of sub array you can think of .
The advantage (if there is any) when using this trick is that the phase trace of the sub is much more horizontal (instead of going down under a angle) and aligning a 2nd (or more) sub is easier this way . If the phase trace is above the first sub measured increase delay if it's below the first trace decrease delay via your system processor .

These are some traces i took from a sub array using smaart
700
These traces were taken from a set of lab horns . On top of the 4 lab horns there were 2 USB horns at a different freq span (also a smaller horn)
701
The trace you see added was taken with smaart being synchronized at the 4 Lab horns .
The USB sub needs polarity inversion to get near the lab horn and maybe i also used a bit of delay to get it to match with lab horns
702
And here's the sum of all 6 subs
703
And here's a picture of this set-up
http://timobeckmangeluid.files.wordpress.com/2013/06/4xlabhorns-2x-usbs-2xturbo-toppen.jpg

Michael Häck
August 5th, 2013, 02:43 PM
Hey Timo,

when you press the P (for Peak) behind the 37.62 in your case, the time will copy and drop in TF mode!

copy the time from the ir measurement manually in to the transfer screen .

Timo Beckman
August 6th, 2013, 03:50 AM
Again thanks

merlijnv
August 6th, 2013, 05:30 AM
Meyer Sound's webinar on impulse response by Mauricio "Magu" Ramirez, is IMO by far the best explanation why impulse response isn't suitable for subwoofers. You can find it in the webinar archive on their website. Impulse response will get you in the ballpark but so will a laser distance meter.

merlijnv
August 6th, 2013, 05:39 AM
When in doubt, I strongly recommend to take a measurement of the subwoofer up close. I place the microphone ONAX practically against the grill. This will provide you with a reflection free phase trace. Now you know what look for in the far field, where reflections will make it harder to read the phase trace.

Timo Beckman
August 6th, 2013, 09:05 AM
I always take a trace of what ever speaker i have to tune or what ever system needs tuning to hopefully find it back in the far field .

I was told many times that smaart had "some problems" synchronizing on a sub woofer while with sim3 you can do this with some different settings in the delay finder menu .
With smaart i changed the settings within the ir menu to semi match the settings within sim3 when doing this kind of measurement and it worked .
Just a small difference in the time from smaart compared to sim3 (ranging from 0.2ms to 0.02ms(1 sample so that might have something to do with the USB driven sound card)).

Wether it useful or not doesn't matter to me . I can do tunings without using this option available or with . Depends on the situation at hand .
On some larger sub array's it might definitely come in handy to verify all subs (polarity/level) . In the end you'll still have to synchronize on the system as a whole tot get the alignment between subs and the rest of the system .

Dr. J
January 25th, 2014, 02:11 AM
http://www.rationalacoustics.com/forums/images/icons/icon1.png Re: multiple measurment
This is best kept on the forum because you will get answers with different points of view. When you MOVE your mic, you should reset the delay time IN SMAART. THis is the delay on the REFERENCE channel. You should time your subs where you want them to be in time. For me this is where the most people are. You cannot have them timed perfectly in every seat. It's impossible. The closest you can come is if your subs and mains are all together very close to each other. The mic location for timing my subs is usually about 2/3rds of the way into the audience. I'm trying to please "most" of the people. I place the mic on the floor for this measurement. It helps clean up the phase trace which is affected by the reflection from the floor. If you put your mic on the floor, there is no reflection at low frequencies.






Harry Brill Jr.
proaudioguy "at" tigeraudioinc.com


Harry - I know this post is old but when you say you lay the mic on the floor do you mean Half plane where you literally lay it flat on the ground facing the speakers or ground plane? Thank you!

Dan Currie
January 25th, 2014, 04:21 PM
Harry - I know this post is old but when you say you lay the mic on the floor do you mean Half plane where you literally lay it flat on the ground facing the speakers or ground plane? Thank you!

I'd assume ground plane. It gets rid of the ground bounce. That's what I use fwiw

Dr. J
January 26th, 2014, 12:39 PM
I'd assume ground plane. It gets rid of the ground bounce. That's what I use fwiw

That's what I was thinking but some just lay it down for some reason. If it is ground plane.... Can you use a table top in an area where a lot of people gather and use that surface ( because it is more at upper body height) that the floor?

PrestonSoper
January 30th, 2014, 05:45 PM
That's what I was thinking but some just lay it down for some reason. If it is ground plane.... Can you use a table top in an area where a lot of people gather and use that surface ( because it is more at upper body height) that the floor?

FWIW: I use a 3' x 3" insert from one of our road cases for gp measurements in measurement zones where a normal gp measurement is not possible.

Here is a link to an application guide by Crown for PZM microphones that may be of interest. (Pages 10-13)
http://www.crownaudio.com/media/pdf/mics/127089.pdf

Dr. J
February 1st, 2014, 05:27 PM
FWIW: I use a 3' x 3" insert from one of our road cases for gp measurements in measurement zones where a normal gp measurement is not possible.

Here is a link to an application guide by Crown for PZM microphones that may be of interest. (Pages 10-13)
http://www.crownaudio.com/media/pdf/mics/127089.pdf

Thank You Preston!