# Start Measure



## MysticDan (Nov 13, 2011)

Hey mates,
sorry for this nb thread, but i never try to do a measure. Now its time to do.
For this measure i will use a pair of speakers near-field, my interface and ECM8000. 
My question is i need to use the pair or only one speakers for measure? if i need to two speakers, i just to calibrate the right and the left output?
And for the calibration, i just do the loopback of the input when i will input the ECM8000 and the output that i will plug my speaker?

I am following the tutorial of GIK.But at 1:55min of the video, he dont use the jacks that he will plug the speakers.
This is confusing me.
Regards,


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

If you’re measuring full-range speakers, you want to measure each individually. Not sure I understand your question about the sound card calibration. Basically, you loop the soundcard’s input and output.

Regards, 
Wayne


----------



## MysticDan (Nov 13, 2011)

Thanks for the reply Wayne. Its not a full range speakers, its a KRK RP Series. So i need measure with the pair? Or only i need one ?
My doubt about calibration is what jack i need to use. Look http://futuremusic.com/news/images/MOTU_UltraLite-mk3.jpg
This is the picture of my interface. I will loop back with the L or R mainout in this picture, or anyout that has 1,2,3,4,5,6,7,8 like in the top of picture?
And the input, i will use the Mic/Inst input that i will plug my ECM or input jack that has 3,4,5,6,7,8?
I hope was clear


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

Since its subwoofers, measure both with the mic placed at the listening position. However, separate measurements can be revealing as well.

As long as it’s not the SPDIF, it doesn’t matter which input/output, but typically you want to calibrate the ones you intend to use. 

Regards, 
Wayne


----------



## MysticDan (Nov 13, 2011)

Thanks Wayne.
I dont use subwoofer. Then just calibrate the left output with my input (loopback) and only use the left speakers?
the right speaker I will not go calibrate and not will use it?

Or i need create a calibrate file for the left side, measure and then create another calibration file with the right side and measure again and for exemple analysis the waterfall of the right side and the waterfall for the left side?
Thats my doubt
I hope was clear
Regards,


----------



## Jef Bardsley (Jul 16, 2012)

You're creating a calibration file for the _interface_. You only need to do it once, unless you change your interface. Ideally, you'd use a splitter from one side of your interface to your amps, hence you only need to calibrate one side of the interface. If instead, you're using the interface in mono, my guess would be the two sides of its output track closely enough for a calibration file of one side to work.


Hope that helps,
Jef


----------



## MysticDan (Nov 13, 2011)

jef thanks for the reply,
so i need something like this this for measure? : http://www.stagebeat.co.uk/sites/stagebeatv8.008/productimages/322x322f/8237.jpg ?


----------



## Jef Bardsley (Jul 16, 2012)

That's an "insert" cable, also called a "send/return" cable. It's meant to be plugged in to a stereo jack (the send/return on most mixers), and looking at the manual for your unit you have mono output jacks. Long, split mono cables are hard to find, so I'd recommend using a single long cable and a splitter like this:

http://www.samash.com/p/Hosa_YPP106%20Mono%2014%20Splitter_-49974517


Be sure to assign "disk tracks" your outputs!


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

No, that’s a headphone splitter. You aren’t using the headphone output (at least I hope not). You need one of these, depending on what connector your speakers require.



















Regards, 
Wayne


----------



## Jef Bardsley (Jul 16, 2012)

Wayne A. Pflughaupt said:


> No, that’s a headphone splitter.


Uhm, only if your headphones have mono female 1/4" jacks. :innocent:
(Which they might, mine have banana plugs!)


Turns out I was wrong, however. I missed the mention of the KRKs, and it looks like the MOTU *does* have balanced outs. So, you want to use the regular 1/4" stereo cables I assume you normally use, and put the MOTU in mono, if possible.


----------



## MysticDan (Nov 13, 2011)

Im glad for the replys
Im so sorry for my noobness oK? but im steal confusing a bit.
I will make a summary of what I think I understand.
My KRK has TRS/TS, XLR and RCA Jacks.
First, i create a calibration file with loopback cable(TSXTS). Just using my left output and my mic input.
Then, i will plug the left speakers(KRK) in the left output with my TRSxTRS cable(keep the right speakers off/unplugged) and will plug the ECM in the mic input.
And finally, do the measure.

After analysis the left speaker graphics (frequency,waterfall....), i do the same with the right speaker(without create a another calibration file -> use the same)?

Conclusion, 
In this way, i will have two waterfall graphics for the same position. One for the left side and one for the right side.

So, what the point of i missed?

I much appreciate mates,
Bests,


----------



## Jef Bardsley (Jul 16, 2012)

I think you've got it!

Right, use the same calibration file.

As I mentioned above, be sure the outputs on the MOTU are set to monitor 'tape' rather than 'mic'.

And, if you want to do a plot of both speakers at once, you might be able to daisy-chain them with an RCA cord.


----------



## Harry M (Jun 3, 2012)

Measuring with two speakers at a time can introduce comb filtering effects into your measurement. Measure with both speakers, one at a time and then together.

Instructions from REW also state:
"Note that some resonances which are very pronounced when measuring a speaker alone do not appear if a pair of speakers (e.g. Left and Right) are run together - this is because the positioning of the speakers in the room can prevent some resonances being excited (in particular, the odd order width modes will not be excited by content which is the same on Left and Right speakers if they are symmetrically placed across the width). Such resonances can often be left uncorrected, to identify them compare measurements from individual channels with those made with two channels driven at the same time (achieved on AV32R DP or AV192R by setting the Repeat Sig. entry in the TMREQ filter menu to Yes and selecting the channel which is to repeat the test signal, or on other processors by connecting both left and right soundcard outputs to the selected AV processor input or using a Y lead to drive two inputs at once)."


----------



## MysticDan (Nov 13, 2011)

Thanks jef and harry for the reply.
what you mean when said "MOTU are set to monitor 'tape' rather than 'mic' " ?
I found this thread that the guy post the right/left/stereo graphcs (look : http://www.hometheatershack.com/forums/rew-forum/55768-help-needed-interpreting-my-graphs.html)

So, this stereo graphcs is made by use one cable splitter (TS/TRS plug in the left output interface and in the other end of the cable splitte/two RCA/TS/TRS that i will plug one in the left speaker and one in the right speaker) OR i will use 2 cables, one coneecting the left output interface with the left speaker and another cable to connecting the right output with the right speaker.

"Measuring with two speakers at a time can introduce comb filtering effects into your measurement. Measure with both speakers, one at a time and then together."

Harry you said : "Measuring with two speakers at a time can introduce comb filtering effects into your measurement. Measure with both speakers, one at a time and then together."

If measuring with two speakers at a time can introduce comb filtering, why after to measure both one at a time i need to measure together?


----------



## Harry M (Jun 3, 2012)

It's useful to use both speakers together to see what, if any, differences there are in the room response. Comb filtering is not a given, just a possibility.


----------



## Jef Bardsley (Jul 16, 2012)

MysticDan said:


> Thanks jef and harry for the reply.


You're welcome. I used to be able to say, "It's just my job.", but I retired from the music store where I worked. lddude:



MysticDan said:


> what you mean when said "MOTU are set to monitor 'tape' rather than 'mic' " ?


I expect the default setting of the MOTU will be for the outputs to be connected to the mic/line inputs, so you can monitor mic placement. When used for measuring your speakers, this will give you feedback - the squealing PA kind, not the helpful kind. What you want is for the outputs to be patched to the input from the USB, so they send the sweep from REW to the speakers. This is likely to be labeled "tape". _This is important_, as feedback squeal can hurt your ears and fry your tweeters, so keep the speaker volume down until you're sure you've got it right.



MysticDan said:


> So, this stereo graphcs is made by use one cable splitter (TS/TRS plug in the left output interface and in the other end of the cable splitte/two RCA/TS/TRS that i will plug one in the left speaker and one in the right speaker) OR i will use 2 cables, one coneecting the left output interface with the left speaker and another cable to connecting the right output with the right speaker.


Since I worked in a music store, I'm pretty familiar with HOSA and other patch cable suppliers, and I'm quite sure you won't find the split cable you need. I'm also trying to avoid having you purchase stuff you'll only use occasionally (I'd say "once" but I'm betting you'll move or replace your speakers at some point :R). So...

Once you're sure your MOTU outputs are connected to REW, play a continuous signal (the SPL meter is handy). Try one speaker with the left output, then switch the cable to the right output. If you hear the signal, that's it - just connect your speakers as you normally would and you'll be able to measure both at the same time.

If there's no signal on the right output, then you either need to get a splitter to send the left output to both your speaker cables, or run a cable to just the left speaker, and connect the right speaker to the left speaker (daisy-chain). 

The assumption behind daisy-chaining them is that the inputs are all connected together in parallel. (I'm basing this on the fact there are no switches on the inputs, and I'm basing that on the manual for the new KRKs.) My guess is, you might have a long RCA cord lying around. If not, you might also use a "gender-bender" with a regular mic cable. That is, a connector that changes one end of the cable from female to male XLR. Gender-benders aren't often useful, so if you have to buy something, I'd go with the RCA cable. 


HTH,
Jef


----------



## MysticDan (Nov 13, 2011)

> You're welcome. I used to be able to say, "It's just my job.", but I retired from the music store where I worked.


thanks so much jef for the answers and for your patience with me 



> I expect the default setting of the MOTU will be for the outputs to be connected to the mic/line inputs, so you can monitor mic placement. When used for measuring your speakers, this will give you feedback - the squealing PA kind, not the helpful kind. What you want is for the outputs to be patched to the input from the USB, so they send the sweep from REW to the speakers. This is likely to be labeled "tape". This is important, as feedback squeal can hurt your ears and fry your tweeters, so keep the speaker volume down until you're sure you've got it right.


Man im so sorry again, in this part i cannot understand everything :crying:, and when i said hurt my ears and fry my tweeters its was so strong for me :heehee:
When you said measure my speakers its like measure my room?
If u can explain again this paragraph i'd very grateful. Especially when you spoke to hurt my ears and fry my tweeters. 
Thanks again


----------



## Jef Bardsley (Jul 16, 2012)

Well, I've just spent over 1/2 an hour scrolling through the manual for the MOTU, and while it's mentioned you _can_ do it, I can't find a description of _how_ you do it. It's probably so obvious.... :duh:

I'd try asking on motunation.com, and what you want to ask is, "How do I set my main outputs to monitor a recording on my computer?"

You see, the test signals from REW will be sent out the USB connection in the same way a DAW program would send out a recording. _This_ is what you want to send to your monitors. 

In all my reading, I did find that I was right, and the default behavior of the Ultralite MkIII is to use your speakers as "studio monitors", and that's _not_ what you want because that means listening to the microphones in the studio. But when measuring, your mic will be in the control room, and that's why it will feed back.

Hoping this makes more sense,
Jef


----------



## MysticDan (Nov 13, 2011)

Very thanks i will do.
I thought t in the REW, the signal was recorded by the microphone was not played again. So its not causing the loopback. 
anyway, thanks again, and i will try to create a thread in motunation.


----------



## Barleywater (Dec 11, 2011)

sound card loopback calibration: Highly recommend REW beta with ASIO

connect an output to an input. In this case with UltraLike mk3 numerous options are possible. Since ultimately using microphone for measurement the input choices are narrowed to microphone inputs. On the interface these are combo jacks that accept XLR or TRS. Typically TRS is Hi-Z and so not what you want, thus TRS to XLR male cable is what you need for loopback measurement/interface calibration. Phantom power off for loopback, though output should be designed to handle this common accident.

Interface has its own mixer application and standalone capability. Doubtless the mixer app. on the computer is easier to use than learning (at least initially) the mixers front panel controls on the interface.

Input monitoring must be found and turned off. Located somewhere in mixer application, such as muting all inputs on buss mixes. While on mixes, no splitter cable is needed with such a fine interface with its own mixer. Which ever output is selected in REW for loopback can be routed to any of the other outputs with the mixer features. It's a little daunting at first, and easy to lose track of what's coming from where, and where it's going too. And just so many buttons, knobs, and sliders, settings that aren't even real.:yikes: 

The loopback calibration is almost more important in revealing input monitoring issues so they may be resolved, than in providing correction to SPL display for extremely low/high frequencies.

In this vein, a recent thread: *Problem of calibration at 96kHz sampling rate. Bug?* using Motu 896 MkIII at 96kHz sample rate looks suspiciously like input monitoring issue. I believe UltraLite and 896 most likely share a lot in common, and it would be nice to see loopback results at 96kHz posted for the UltraLite. It could be beneficial in resolving AndreaT's problem, or in figuring out who's problem it really is.

Thanks.

Andrew


----------



## MysticDan (Nov 13, 2011)

Hi Barleywater. thanks for the reply.
Of course i will try this. I'll try and come back later to talk about the results in both samples rate.
But in measurement, what is the difference of using different sample rate?


----------



## Barleywater (Dec 11, 2011)

Sample rate determines upper frequency limit that can be measured. Theory places the maximum frequency at ½ the sampling frequency. Reality of anti aliasing filter (brick wall filter) reduces this somewhat, so for 48kHz sample rate upper limit is a bit less than 24kHz sound, and double that for 96kHz sample rate. From here the subject rapidly gets onto slippery slope: Limits of human hearing, transient response perceptions, gets ridiculous debates going real fast. Noise shaping allows shifting of noise in sensitive ranges of human hearing to areas of less sensitivity. So noise shaping may be applied to high sample rate session, mix and mastering, but much of this seams defeated by virtually any additional processing, and this includes playback. Why do high sample rate recording? Jury is still out in my opinion. This said, much engineering has gone into high sample rate gear, and if the gear allows it, at least it should work correctly.

Allowing ultra sonic content into lots of hardware can wreak havoc. Then there is intermodulation effects: Two closely spaced frequencies in conjunction with device non linearity result in a frequency that is the difference of the two input frequencies. This can put a lot of stress on an otherwise great tweeter and make it sound bad.

It will be nice to see your 96kHz sample rate loopback results.

Thanks for the interest.

Andrew


----------



## MysticDan (Nov 13, 2011)

Hey andrew, let me know one thing
this cable XLR x TRS is a simple cable or i need to use any resistor or something like that?


----------



## Barleywater (Dec 11, 2011)

TRS x XLR male is standard issue.

Andrew


----------



## MysticDan (Nov 13, 2011)

Thanks andrew,
Why in this tutorial (http://www.hometheatershack.com/roomeq/wizardhelpv5/help_en-GB/html/calsoundcard.html ) not talk about for the turning off the input monitoring?


----------



## JohnM (Apr 11, 2006)

MysticDan said:


> Why in this tutorial (http://www.hometheatershack.com/roomeq/wizardhelpv5/help_en-GB/html/calsoundcard.html ) not talk about for the turning off the input monitoring?


It's in step 5.


----------



## MysticDan (Nov 13, 2011)

came the day. I do the process today and try the first calibration and measurement.
Before i do, let me just make one last question.
Is there any risk that I do something wrong and damage my interface
or change a default setting?
I say this because this interface use it for recording and mixing. And for my budget, this interface is expensive. Should I buy a simple as a Behringer UCA202 just to make the measurement, or can I do in my motu without any problem / concern?
im so sorry for this noob question, but I've had a problem with an interface and could not identify the cause. I am afraid to damage it and have the same headache.
thanks so much and sorry again


----------



## Jef Bardsley (Jul 16, 2012)

No, I don't think there's any risk to your interface.


----------

