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[Johnny Diaz]

Hello,

My name is Johnny and I'm been an avid lurker here on psw for sometime.  Have learned alot from reading threads and study hall.  I'm new to the sound reinforcement world.  I have downloaded and installed Smaart 7.  Im using a Mac along with the first USBPre and a Rane TTM57SL mixer.  The mixer has balanced xlr left + right outputs.  My question is on the hookup. 

I have two Mackie Powered speakers connected to the mixers xlr outputs.  From what I understand I'm supposed to use a y cable to split the signal on the mixers out to get a reference signal and connect that to the USBPre.  If I do this don't I lose the signal on that output by half?  The measurement signal goes from the USBPre to the USBPre.     

Thanks for your help

[Rob Spence]

As a lurker you must have seen the mods require real names.

[Johnny Diaz]

As a lurker you must have seen the mods require real names.

Sorry about that.

[Jay Barracato]

Hello,

My name is Johnny and I'm been an avid lurker here on psw for sometime.  Have learned alot from reading threads and study hall.  I'm new to the sound reinforcement world.  I have downloaded and installed Smaart 7.  Im using a Mac along with the first USBPre and a Rane TTM57SL mixer.  The mixer has balanced xlr left + right outputs.  My question is on the hookup. 

I have two Mackie Powered speakers connected to the mixers xlr outputs.  From what I understand I'm supposed to use a y cable to split the signal on the mixers out to get a reference signal and connect that to the USBPre.  If I do this don't I lose the signal on that output by half?  The measurement signal goes from the USBPre to the USBPre.     

Thanks for your help

The powered speakers probably have a full range output on the back which is basically a split. you could pull your reference signal off of there.

Another option would be when you are measuring a single box use one side (L) for the reference and the other side R to drive the speaker.

[Johnny Diaz]

The powered speakers probably have a full range output on the back which is basically a split. you could pull your reference signal off of there.

Another option would be when you are measuring a single box use one side (L) for the reference and the other side R to drive the speaker.

"Another option would be when you are measuring a single box use one side (L) for the reference and the other side R to drive the speaker."

If I were to do this wouldn't it affect the phase. From what I understand the Phase trace shows us how well 2 speakers sum up. If I use one output for reference I wouldn't get an accurate reading since only one speaker would be connected.  I'm using the system in stereo.

[Arthur Skudra]

Hello,

My name is Johnny and I'm been an avid lurker here on psw for sometime.  Have learned alot from reading threads and study hall.  I'm new to the sound reinforcement world.  I have downloaded and installed Smaart 7.  Im using a Mac along with the first USBPre and a Rane TTM57SL mixer.  The mixer has balanced xlr left + right outputs.  My question is on the hookup. 

I have two Mackie Powered speakers connected to the mixers xlr outputs.  From what I understand I'm supposed to use a y cable to split the signal on the mixers out to get a reference signal and connect that to the USBPre.  If I do this don't I lose the signal on that output by half?  The measurement signal goes from the USBPre to the USBPre.     

Thanks for your help

I recommend you review the documentation that is available online at www.rationalacoustics.com, in particular, this multi page document:
http://www.rationalacoustics.com/pages/Measurement_Rigs

It really doesn't matter where you split the signal, whether at the output or input of the console, but you need to be careful in taking a mixing console output lest an eq is inserted somewhere in the path that influences your reference channel.  My preference is to use a simple RCA "Y" cable to take the RCA output from the USBPre, and feed that into input #2 on the USBPre.  Then plug a measurement mic into input #1 and measure away.

I highly recommend you attend a Smaart class.  Anyone can get a squiggly line to show up on your computer screen, but knowing how to interpret the data (or even knowing whether it's valid) is a completely different story.

[Johnny Diaz]

I recommend you review the documentation that is available online at www.rationalacoustics.com, in particular, this multi page document:
http://www.rationalacoustics.com/pages/Measurement_Rigs

It really doesn't matter where you split the signal, whether at the output or input of the console, but you need to be careful in taking a mixing console output lest an eq is inserted somewhere in the path that influences your reference channel.  My preference is to use a simple RCA "Y" cable to take the RCA output from the USBPre, and feed that into input #2 on the USBPre.  Then plug a measurement mic into input #1 and measure away.

I highly recommend you attend a Smaart class.  Anyone can get a squiggly line to show up on your computer screen, but knowing how to interpret the data (or even knowing whether it's valid) is a completely different story.

"My preference is to use a simple RCA "Y" cable to take the RCA output from the USBPre, and feed that into input #2 on the USBPre.  Then plug a measurement mic into input #1 and measure away."

If I were to do this how would it compare the signal coming out of the mixer?

"I highly recommend you attend a Smaart class.  Anyone can get a squiggly line to show up on your computer screen, but knowing how to interpret the data (or even knowing whether it's valid) is a completely different story."

I would love to take a class but funds wont allow me.  I'm saving up to buy the smaart program.

[Arthur Skudra]

"My preference is to use a simple RCA "Y" cable to take the RCA output from the USBPre, and feed that into input #2 on the USBPre.  Then plug a measurement mic into input #1 and measure away."

If I were to do this how would it compare the signal coming out of the mixer?

"I highly recommend you attend a Smaart class.  Anyone can get a squiggly line to show up on your computer screen, but knowing how to interpret the data (or even knowing whether it's valid) is a completely different story."

I would love to take a class but funds wont allow me.  I'm saving up to buy the smaart program.

You need a reference and a measurement channel.  Your reference channel is the un-eq'd signal.  In other words, it needs to the pure, unadulterated test signal you're using to measure the system with, hence the "Y" cable directly on the output of your signal generator.  Your measurement channel is whatever you're measuring the *change* happening to the system under test.  This could be the output of the mixer, eq, or a mic setup in a room.

[Johnny Diaz]

You need a reference and a measurement channel.  Your reference channel is the un-eq'd signal.  In other words, it needs to the pure, unadulterated test signal you're using to measure the system with, hence the "Y" cable directly on the output of your signal generator.  Your measurement channel is whatever you're measuring the *change* happening to the system under test.  This could be the output of the mixer, eq, or a mic setup in a room.

Ok so I want to compare the signal coming out of mixer to the signal from the measurement mic.  Would I use a y cable from the output of the mixer? 

[Ben Malone]

I have two Mackie Powered speakers connected to the mixers xlr outputs.  From what I understand I'm supposed to use a y cable to split the signal on the mixers out to get a reference signal and connect that to the USBPre.  If I do this don't I lose the signal on that output by half?  The measurement signal goes from the USBPre to the USBPre.     

Thanks for your help

The quick answer to your original question is no, you will not lose half the signal by splitting one of the mixer's outputs.

[Arthur Skudra]

Ok so I want to compare the signal coming out of mixer to the signal from the measurement mic.  Would I use a y cable from the output of the mixer?

Yes.  As long as the point where you "y" the output of the mixer is prior to the system eq.  And no, splitting an output does not reduce the level.

[Rob Spence]

Also, in order to determine where to take the reference signal you need to define what you want to measure.
Many PA systems have a speaker processor or DSP after the mixer and before the amps. In these systems it is common to want to measure what the "speakers" are doing to the sound. Speakers, in this case is the speaker cabs, the amps and the DSP. Based on what you see, you make changes in the DSP.
In your case where the speakers are powered and contain a DSP as well you need to determine what you want to measure since you can't make changes in the DSP.
 If I were in your position, and I have been, then I would want to take my reference before my system EQ (typically at Graphic EQ) so I could make EQ changes based on my measurements.
A Y cable is a fine way to get the signal. It doesn't split half each way... Both paths will get the whole signal.

[Nicolas Lowman]

Hi Johnny,

If you are serious about this stuff, get the book "Sound Systems: Design and Optimization, Second Edition: Modern Techniques and Tools for Sound System Design and Alignment" by the one and only Bob McCarthy. You will have lots of questions and there are many answers in the book. It is highly recommended.


Nicolas

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