# REW hardware.....Bang for the buck



## j.burtt (Jan 30, 2009)

I am going to be embarking on a couple of speaker projects and decided on REW as a measurement tool. I have no equipment yet, so I'm looking for a recommendation on a mic and a preamp for my Windows 7/64 usb2 & 3 laptop. I think I will need a usb preamp because my laptop only has a single headphone/mic jack. Accuracy and reliability at a reasonable price is my #1 goal. 

I'm computer savvy and have used RTA's in the past, but never on a pc based system.

Any feedback on hardware or links to any threads to beginners setup and getting started would be greatly appreciated.

Thx,

James


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## Kal Rubinson (Aug 3, 2006)

j.burtt said:


> I am going to be embarking on a couple of speaker projects and decided on REW as a measurement tool. I have no equipment yet, so I'm looking for a recommendation on a mic and a preamp for my Windows 7/64 usb2 & 3 laptop. I think I will need a usb preamp because my laptop only has a single headphone/mic jack. Accuracy and reliability at a reasonable price is my #1 goal.


Since your laptop has USB 2/3, you can get a USB mic (like the UMIK-1) and not need a preamp.


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## j.burtt (Jan 30, 2009)

From what I've read, I thought I needed to use a preamp since the single jack on my laptop does both input and output.


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## EarlK (Jan 1, 2010)

j.burtt said:


> From what I've read, I thought I needed to use a preamp since the single jack on my laptop does both input and output.


One can still get REW to output it's audio through the computers "multi-jack", while ( simultaneously ) using the UMIK-1 as the input into REW .

FYI ( slightly more complicated ), one can also use ( simultaneous with the UMIK-1 ) a simple usb based soundcard ( such as the  *Behringer UCA-222*  ) for output from REW ( as long as the card uses Window's generic usb driver ) . I've tested this setup ( on my old laptop running XP ) using the UMIK-1 & the UCA-222 together ( using *ASIO4ALL*  ) .

The *UMIK-1* mic is recommended because it is simple to use ( plus inexpensive ) . There's an growing user base ( for these mics ), making it pretty wide-spread ( & this means there's an ever expanding web-based user group, that can act as your virtual "help file" ) .



:sn:


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## j.burtt (Jan 30, 2009)

EarlK said:


> One can still get REW to output it's audio through the computers "multi-jack", while ( simultaneously ) using the UMIK-1 as the input into REW .
> 
> FYI ( slightly more complicated ), one can also use ( simultaneous with the UMIK-1 ) a simple usb based soundcard ( such as the  *Behringer UCA-222*  ) for output from REW ( as long as the card uses Window's generic usb driver ) . I've tested this setup ( on my old laptop running XP ) using the UMIK-1 & the UCA-222 together ( using *ASIO4ALL*  ) .
> 
> ...


That's great, I've always been a fan of K.I.S.S., and the UMIK-1 fits the simple part. 

I saw a chart somewhere that showed I needed an output to get signal to my stereo's preamp, an input for the SPL meter and an input for the measurement mic.

What SPL meter do you recommend? My understanding of it's use is to establish a SPL baseline for the measurement mic, right? Once you store this reference do you still need to use the SPL meter?


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## Kal Rubinson (Aug 3, 2006)

j.burtt said:


> That's great, I've always been a fan of K.I.S.S., and the UMIK-1 fits the simple part.


Agreed.



> I saw a chart somewhere that showed I needed an output to get signal to my stereo's preamp, an input for the SPL meter and an input for the measurement mic.


Nope. You need an input for the mic (USB) and an output for the stereo system (headphone jack) and you do not need the SPL meter if the mic's calibration comes with sensitivity info.



> What SPL meter do you recommend? My understanding of it's use is to establish a SPL baseline for the measurement mic, right? Once you store this reference do you still need to use the SPL meter?


See above.


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## j.burtt (Jan 30, 2009)

:TT


Kal Rubinson said:


> Agreed.
> 
> Nope. You need an input for the mic (USB) and an output for the stereo system (headphone jack) and you do not need the SPL meter if the mic's calibration comes with sensitivity info.
> 
> See above.


That leaves me assuming the Umik-1 has the proper sensitivity info built into the latest release of REW.


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## j.burtt (Jan 30, 2009)

Actually in it's calibration file, haha. At least I think I'm right.


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## j.burtt (Jan 30, 2009)

Just purchased the UMIK-1 from Cross Spectrum. Now, I need to figure out what else I will need. 

Maybe a mic stand???? 

How long of a cable does it come with?


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## EarlK (Jan 1, 2010)

j.burtt said:


> Just purchased the UMIK-1 from Cross Spectrum. Now, I need to figure out what else I will need.
> 
> Maybe a mic stand????
> 
> How long of a cable does it come with?


It appears to me that maybe you've rushed into this purchase without completing your homework/research .

For instance, if you're intending on putting together a hardware system that can collect the necessary data for crossover design ( & hand it off to a sophisticated network modeling program ), then the UMIK-1 is not the unit to get . You need a 2-chnl soundcard ( for that ) because you'll need to dedicate one as a timing channel .

Instead, you'll need something like the calibrated Dayton EMM-6 mic // coupled with a 2-chnl preamp Soundcard ( such as the *Focusrite 2i2* or  T*ascam US-122mkII*  ) .

:sn:


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## j.burtt (Jan 30, 2009)

EarlK said:


> It appears to me that maybe you've rushed into this purchase without completing your homework/research .
> 
> For instance, if you're intending on putting together a hardware system that can collect the necessary data for crossover design ( & hand it off to a sophisticated network modeling program ), then the UMIK-1 is not the unit to get . You need a 2-chnl soundcard ( for that ) because you'll need to dedicate one as a timing channel .
> 
> ...


Thanks EarlK. 

Just sent CS a message to change my order to the Dayton EMM-6 Premium Plus. Hopefully they haven't shipped it yet. You are exactly right, my first project will be setting up midrange and high frequency horns on my 105db Frazier Super Texan bass horns.

Any preference on which of the 2 sound cards?


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## EarlK (Jan 1, 2010)

Both of those soundcards are nice solid units ( the 122 is the more "weighty" of the two ) . Both are well built, giving a nice feeling of "quality", when turning a knob for instance .

The Tascam is a bit cheaper, while the Focusrite has better input metering ( actually, like most cards in this price range, the Tascam has no input metering ) . 

I do own both ( well actually, I have the Tascam US-144, to be a bit more exact, which I got it for it's midi capability ) . 

I guess I will give the edge to the Focusrite simply because of the input metering . ( It's very easy to see when a person should back-off the input gain > due to the metering turning red ) .

:sn:


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## j.burtt (Jan 30, 2009)

If I remember correctly the midi function is necessary to use the auto eq programming in Minidsp???


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## EarlK (Jan 1, 2010)

j.burtt said:


> If I remember correctly the midi function is necessary to use the auto eq programming in Minidsp???


No, it's useful if a person wants to Auto-Configure the PEQ filters found within some of the Behringer EQ units ( that REW specifically supports ) .

Install REW , open the EQ window , then click on top right tab to see exactly which Behringer models are supported .
- FYI, you'll see a bunch of EQ's listed from other manufacturers, but they don't have midi connectivity .

:sn:


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## j.burtt (Jan 30, 2009)

Thanks for the help EarlK. Hope you're around when it comes time to fire it up and test some drivers. 

I got a shipping notification from Herb @ Cross Spectrum on the EMM-6 Premium Plus. Should have it in a couple of days.

I just ordered the Focusrite 2i2 from BH Photo too.


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## hifiaudio2 (Jun 25, 2014)

If I can piggyback on this discussion of bang for the buck REW hardware, it seems that I went for the "simple" setup and bought a USB UMM-6 mic and successfully got REW up and running / measuring with my HDMI / USB laptop. BUT... what I did not understand when I purchased this mic is that this type of setup will not let me use loopback to set delays and also objectively align the subs to the mains. So what hardware do I need for this? I assume the UMIK-1 and some external soundcard? Or a mic preamp too? All of the above? Thanks for all help!


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## EarlK (Jan 1, 2010)

hifiaudio2 said:


> If I can piggyback on this discussion of bang for the buck REW hardware, it seems that I went for the "simple" setup and bought a USB UMM-6 mic and successfully got REW up and running / measuring with my HDMI / USB laptop. BUT... what I did not understand when I purchased this mic is that this type of setup will not let me use loopback to set delays and also objectively align the subs to the mains. So what hardware do I need for this? I assume the UMIK-1 and some external soundcard? Or a mic preamp too? All of the above? Thanks for all help!



Either SoundCard ( SC ) mentioned previously will suffice . 

Both of those soundcards have builtin mic pre-amps & can deliver 48V phantom power ( needed for all test mics ) .

One then needs a mic such as the  *EMM-6 from CSL*  .


Since you've already jumped the gun once ( so before spending more $$ ), I suggest that you read a whack of threads on the subject of aligning subs with mains ( use this forums search engine to find them ) .

Also, look for what ( HTS member )"*jtalden*" has to say about alignments ( I consider him the site expert on this subject ) .
- I believe that in the past he's stated that achieving _acceptable_ ( sub to mains ) alignment doesn't dictate a two channel soundcard ( though all the following examples do employ a timing channel ).

Simply using the RTA window ( while playing back PN Pink Noise from the generator ) & then turning the "phase knob" on a powered sub ( while watching for the best "combining" in the crossover region ), is good enough for many .

Here's  *A thread*  ( that obviously used a timing channel ) .

And  *Another* 

 *One More !* 

 *A Favourite !* 

* Last One !* 

:sn:


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## hifiaudio2 (Jun 25, 2014)

Thanks for the links. I am working through them. Although at this point I think I am more confused that when I started. Lots of them start of making me think they are going to simply say "click these settings and take this measurement" but by the end of the instructions I don't even know what I am trying to measure. Ugh.

Some of them get into time alignment of drivers within a cabinet so that may be where I get a little off. I just want to align my subs with each other, set objectively proper distances for my main speakers, and then time align the single sub channel (the sum of the 4 subs) to the center channel speaker.


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## jtalden (Mar 12, 2009)

hifiaudio2 said:


> I just want to align my subs with each other, set objectively proper distances for my main speakers, and then time align the single sub channel (the sum of the 4 subs) to the center channel speaker.


Half the battle is knowing what you want to do! With 4 subs there are likely several good approaches to achieve smooth bass response. My experience is with time aligning the SW so they are: 
1. Working together
2. Time aligned as a group to best match the main speakers. 

I think of these as 2 separate tasks. I suggest you address one at a time.

How #1 is approached is very dependent on the equipment used to adjust delays and how much work/learning you want to do. If you want some help or direction from me, please provide some background on your equipment and setup.

You also mentioned aligning the mains as well. That is also possible in a very technical and obsessive way, but it is perfectly adequate to just set the mains timing per the measured distance unless there is reason that the electrical delay is different between them as maybe in some HTPC setups using FIR filters?


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## hifiaudio2 (Jun 25, 2014)

jtalden said:


> Half the battle is knowing what you want to do! With 4 subs there are likely several good approaches to achieve smooth bass response. My experience is with time aligning the SW so they are:
> 1. Working together
> 2. Time aligned as a group to best match the main speakers.
> 
> ...


Thank you very much for the offer. 
Here is the pertinent equipment:

Three Seaton Catalyst 12c mains, Four Seaton Submersive F2 subwoofers, Triad Bronze L/C/R surrounds, Marantz AV8801 (not using Audyssey), Emotiva UPA-2, UPA-200, 

Xilica XP-2040 for sub EQ

I have attached a diagram of my room with sub locations (not changeable).

Regarding electrical delay, my LCR speakers and all subs have a DSP crossover in them so their distances will differ from measured. The surround are not active surrounds so they can be measured.

If it is useful here is also an MDAT file. The small description in the left box for each measurement corresponds to which sub it is and how much delay is added in the Xilica. I.e "right 9.75ms" is the right side sub with 9.75ms of delay.

Thanks again!


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## jtalden (Mar 12, 2009)

I've been looking over your measurements.
Step 1 (SW cooperation). Q's:
> No XO appears to be active - correct?
> What XO freq are you planning to use? Will it be implemented in the pre/pro?
> Were all these measurements taken at the LP through the pre/pro LFE channel?
> Can you provide some rough idea of how the delays were decided. If not by measurements, and without loopback active, then how?

Are you just looking for recommended delays, or looking to understand how I came to the recommendation.


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## hifiaudio2 (Jun 25, 2014)

That is with a crossover active. 80hz. I just now looked at the measurements I posted and realized that they arent the last I took, just the last I saved I guess. I think when I did those measurements I just had the overall subwoofer channel gain too high. I have since lowered it so that the level below the crossover region matches what it is around 100hz. I had thought I saved them after lowering that gain, sorry about that. 

I have been planning on keeping using 80hz in the processor. My speakers will easily play just as loud as I want down to the 50hz range or so if that is a suggestion.

Measurements at the LP using "output 3" in REW which gives the center channel plus the bass managed sub

I came to the current delays by measuring the center channel and sub together with a sine sweep and looking for the best response with an emphasis on overall reinforcement/SPL and as smooth of a curve as I could get around the 80hz point. That was based on the reading I did from a document about setting the sub delay as an "audyssey tweak". 

I would love to get both suggestions and an explanation of what to do, why, etc. I read and read and think I have a handle on something, but then come across posts that make me question that I have the faintest clue what I am doing! 

Thanks a ton for your time!


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## jtalden (Mar 12, 2009)

80Hz for XO in pre/pro is normally very good. I would leave it that way for now. 

Was the CC active also? This would then be a SWx+CC measurement set, or was it disconnected so it is a SWx set only? I ask because there is almost no rolloff from the 80Hz XO up to 400Hz!

Don't remeasure yet. I want to review this data a little more and then I will provide some settings to use for the next round.

I need to know the measured distances; LP to each SW and also to FL, FR, CC (±2 in. is great if possible). Don't worry if the error is a little larger than that.

Did you notice the distortion. It's very low >50Hz, but is very high <30Hz? . Unless the SPL was much higher than shown on the chart I would not have expected that. The Seaton site was down so I could not find any info on the SW response. I would expect they are more capable than that. I'm wondering if something is wrong with the measuring setup. I don't see any other evidence problems and it is not an issue for our current objective.


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## hifiaudio2 (Jun 25, 2014)

Yep the center was active. 

I will try to get some physical distance measurements by tomorrow. Some will be measured and then guestimated for the final bit because the subs are behind wall fabric and the LCRs are being the screen that I cannot move on my own. 

Regarding the distortion... before doing these I gain matched everything using the SPL meter portion of REW. I ended up setting pretty high gains in the Xilica instead of doing that in the AVR to match the sub level to the mains. I think this made something in the Xilica clip. Yeah the Seatons can play cleanly to 10 hz and below. In fact on an earlier measurement I took with them before I messed around with the gains in the Xilica I had forgotten that the LFE only channel when set to output in REW would be 10dB hotter. I ended up with a measured 99dB at 12hz. They didnt even break a sweat. I just need to go back into the Xilica and lower those gains and do all of that matching in the AVR. It also could have been an issue with the computer outputting the sound over HDMI, since even after doing those gains in the Xilica I listened to a bunch of music that night pretty loud and with plenty of bass and never heard the distorting sound that I heard with these measurements.


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## jtalden (Mar 12, 2009)

That makes sense.


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## hifiaudio2 (Jun 25, 2014)

Left wall sub: 9'6"
Right wall sub: 9'3"
Back wall sub: 13'
Front wall (in baffle) sub 14'
Center (in baffle): 13'4"
Right (in baffle): 14'2"'
Left (in baffle): 14'2"

Again any of these could vary 2-4" from what I listed, as I am measuring alone and also guesstimating for how much space between the fabric or screen that the speakers are behind. 
Also all of these speakers have DSP inside them so the electrical delay will be different.


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## jtalden (Mar 12, 2009)

Thanks, the dims are fine.
I am assuming the SW amp delays are similar to each other. Normally digital amps add maybe about 1ms delay from what I have seen reported. This is trivial when aligning SWs. We are really only interested in the distance differences not the absolute values for SW timing anyway. If the amp delays are equal for each of the 4 SWs then they will have no effect.

If you are okay to start from scratch for Step 1 then: 
It will take 5 new SW measurements under the following conditions:
> Your current signal routing is fine (channel 3 CC)
> Pre/pro CC distance as currently set. (The distance chosen does not matter for this purpose)
> Disable the CC speaker so only the SWs are measured (we'll then see the impact of the 80 Hz XO setting)
> Measurement sweep range = 5-400 Hz
> Mic at LP
> Set Xilica SW delays to: [based on the difference in distances]
SWf = 0.0ms
SWb = 0.9ms 
SWl = 4.0ms
SWr = 4.2ms
> Adjust the pre/pro level so SWf (front SW) measurement is approx. 75dB then use the same setting for the other 4 measurements. Do not readjust the level. Each SPL trace may be at a different level. the Hopefully the 4 SWs are not too different in SPL from one another as we want them all contributing relatively equally to the total. The "SWs" measurement (4 together) will definitely be much higher. That is something we want to see.

[I will not be able to compare the relative merits of the current SW delay settings using the data already provided. If we want to see that difference it will also be necessary to include a "SWs-orig" measurement (4 SWs together using the original Xilica delay settings). That would be a sixth measurement.]


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## hifiaudio2 (Jun 25, 2014)

Sorry I didnt get to this last night... I should be able to tonight. Thanks again for your help!


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## hifiaudio2 (Jun 25, 2014)

Ok here are the measurements. Hopefully I did what you asked. From what I can tell below about 80 hz the response is very good even unsmoothed on the summed sub response. 

Still no idea what is going on with the distortion. It must be something in the laptop HDMI signal. This didnt happen my first few times taking measurements a week or so ago, so I don't know what is going on. No positive gains are set on any channel in the Xilica now, nor even on the sub channel on the Marantz. And obviously the SPL levels are way below any clipping for the hardware. Oh well. 

Looking forward to your feedback.


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## hifiaudio2 (Jun 25, 2014)

added one more .mdat with hotter sub channel so 20hz matches peak at ~115hz


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## jtalden (Mar 12, 2009)

hifiaudio2 said:


> Looking forward to your feedback.


Distortion:
We are now all envious. :TT With an SPL of about 75dB, there is only about 3% THD in the lowest range, 10-20Hz. As shown below, with the cursor placed at 20Hz note that the chart legend reports the %THD and also the harmonic levels for that cursor position. Even though the chart shows a rise there, the actual level of distortion is very low. Much of the reported distortion at that very low freq is likely due to the noise floor which is typically pretty high at those low freqs. So, even if the SPL was significantly raised I would expect the distortion to stay very low. You have lots of LF capacity! I hope you like explosions. 









SW cooperation and timing:
We are now all envious - again. The power of 4 demonstrates its value. 
The 4 SW are now working well together and the distribution of SWs results in a smoothing of the SPL.

Shown Below, the SPL level of SWl is maybe 5db lower than the other 3 SW. I think that is good as it's response shape is likely to disrupt the smoothness of the summation if it were to be raised up 5dB. There is lots of LF capacity so you do not need to increase the level of that SW.









Shown Below the SWs measurement is about 12 dB above the simple average of the 4 SW. This is the amout expected for full cooperation of 4 SW. Above the XO the cooperation is not as ideal still very very good. There are no adjustments to be made.









The First step is concluded. The SW delay settings in the Xilica for the SWs are good and should not be changed in any future work. The SW level on the SW amps should also not be changed. You may want to record where they are set. 

I will now think about the next step unless you have questions on this one.


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## hifiaudio2 (Jun 25, 2014)

Awesome, thanks! So I should leave the sub level in the AVR at flat, which is where all measurements except the last one were took, or leave it at +3.5 which is that last separate .mdat file?

And yeah .. i cant even change the level of the sub amps themselves. I can't get to those subs... 

That is another reason I got the Xilica... so that I could change the gain on the subs without being able to physically get to them.


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## jtalden (Mar 12, 2009)

My comments were directed to the individual SW levels. Do not change them. The group of 4 together may need adjustment to match the mains. Again the first step was getting the SW to work together and confirming that. That is completed. 

You can apply some EQ to the SWs in the Xilica input EQ section to do a little more smoothing if you like. The EQ should impact all SW boxes the same. EQ is not really needed as the results are very good as is. If you do some touch up, just keep in mind Wayne Pflughaupt advice regarding good EQ practices. Avoid High Q filters. Just add any shaping that you desire. Be sure to read about House Curves. I would leave the house curve flat for now and adjust it to taste as needed after the mains are well integrated. It is likely that you will prefer some downward slope for music especially. It's a big subject with no correct answer. It is a very personal thing.

Level changes for the SWs as a group is fine. That is a group adjustment for leveling to the mains. I would tend to think in terms of adjustment to the levels of the main to match the SWs as the mains probably are all slightly different.


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## jtalden (Mar 12, 2009)

Step 2: (adjust the SW to mains distance/delays)
Let's start with the just the CC to SWs since that is what you have used for Step 1.

Q's:
> I assume the only delays in your setup are the distance settings in the pre/pro (ignoring any delay in speaker amps). Correct?
> What were the current distance setting for the CC and the SW in the pre/pro. (those used for the above measurements)? The SPL support in the XO range looks very good, but we should determine if we are at the conventional phase alignment as opposed to one of the other good alignments.

Take 3 new measurements:
1. SWs
2. CC
3. SWs+CC (both active)

Test Conditions:
> The small +3.5dB SWs level adjustment from above that was applied to match the CC level is good to use. We want the SWs and CC SPL levels to match reasonably well for this step.
> If you applied any EQ to the SWs that is okay to leave active, but let me know what the filter settings are in that case. 
> No EQ should be applied to the CC itself.
> Your current signal routing is fine (channel 3 CC)
> Pre/pro SW distance set to 14' 0". (the measured distance)
> Pre/pro CC distance set to 13' 4". (the measured distance)
> Measurement sweep range = 5-20,000 Hz (for all 3 measurements)
> Mic at LP
> 80 Hz XO active in pre/pro
> Individual SW delays in Xilica left as we determined in Step 1.
> Adjust the pre/pro level so SWs (4 SW together) measurement is around 75dB then use the same volume setting for the other 2 measurements. Do not readjust the levels in the 3 measurements as I need to see how well matched they are.

From these measurements we will be able to determine how to adjust the SW distance setting to find the conventional alignment. That is the one that provides the best XO SPL support and the best phase tracking.


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## hifiaudio2 (Jun 25, 2014)

Correct the only delays are the pre/pro distance settings. And no EQ applied to anything yet. Distance settings were 15.7 ft for CC ( this is what audyssey originally came up with I believe to take the Catalyst dsp delay into account) 

0.0 for sw.

I will make those changes and take some measurements in the morning.


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## hifiaudio2 (Jun 25, 2014)

Here are the new measurements.


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## jtalden (Mar 12, 2009)

Okay - The bad news.
I have conflicting recommendations depending on the interpretation of the measured results. Much of this is just because of the limited information we have available so far (measurements). 

There appears to be a room mode null for the CC speaker near 80Hz. This mode is not present in the SWs response. This is could be accounted for with adjusted SWs timing, but I suspect that the new timing would cause problems with the FL and FR that would be much more audible.

The path forward is speculative until I see more data.

4 more measurements are needed:
1. FL
2. SWs+FL
3. FR
4. SWs+FR

Conditions/Setup:
> Use the same setup and conditions as for the CC above. Be sure and use the measured FL and FR speakers distances into the pre/pro (14' 2").

Also - One Extra Measurement:
After the 4 above are done, I also would like one additional near field measurement. 
> Put this measurement in a different .mdat file. 
> Place the mic at approx 3ft directly in front of one the 3 front speakers. [Use the CC if it is set vertically. Use one of the others if the CC is set horizontally.]
> The mic height should be set close to the center of the speaker (TW height). 
> Mute the SWs and just measure the one main speaker.
> The pre/pro volume should be adjusted down so the measurement level is around 70-75dB
> The other conditions are as before.

The purpose of this additional measurement is to let me see the phase response of a main speaker with much less room influence. This will help me properly interpret the phase tracking at the LP measurement position.


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## hifiaudio2 (Jun 25, 2014)

Here are the new measurements. I didnt do that final measurement for you yet because I wanted to ask and make sure you didnt need any more measurements from the MLP. I haven't touched the mic since starting this process so it would not move even an inch and cloud any measurements. Getting that nearfield measurements means I have to move it. 

One error I did realize I have made and have not corrected yet, I measured things like 14'2" but when I put it in the AVR that became 14.2 feet, which is not the same since that ".2" is just a % of another whole and not 2". If I want that to be more accurate I will have to go back and make the conversion. Of course so far the measurements have shown better when using the distances AUdyssey originally calculated taking the DSP in the speakers into account. 

So I will go ahead and make that nearfield measurement if you think you have what you need for now from the MLP. I know we may have to go back to those anyway but I just figured I should get all I can before moving the mic.


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## jtalden (Mar 12, 2009)

The small distance discrepancy you mentioned is not a real concern as the XO is at 80Hz where the wavelength is much larger than that small error. 

I think it is fine that the mic is moved now. The near field measurement may help in finding the correct distance setting.

The initial measured distance data above is used to allow me identify a good starting positions of the IRs for the analysis. These are not the final distance settings. We will indeed need to run a new set of measurements to confirm the final calculated distance settings will work as the calculation predicts. It will be good enough to just take note of the present mic position and replace it reasonably close to that same position. The SPL will vary somewhat, but there will be no significant impact to the distance settings. 

I offset the initial SW IR as needed so that the calculated A + B (SWs+main) agrees with the measurement of SWs+main. That connects the measured distances to IR positions. That becomes the initial reference IR alignment. Then additional SWs IR offsets can be made to find the best phase tracking condition. The IR offset needed to find that point from the initial reference IR alignment determines how much SWs distance change is needed to achieve that new alignment.

A quick look at the new FL and FR data shows the measurements went well. Tomorrow I do the analysis to determine the timing/distance that I would recommend. It will take several hours.

Audyssey usually does a good job of assigning distances in my experience. Without loopback timing the process I use is difficult and thus errors can be made. The next confirmation measurements will show if my calculation was correct. It will be interesting to compare the resulting calculated distances to the Audyssey distances. The best case is if the calculated distances agree with those Audyssey assigned and thus there is high confidence in the settings. In the past we have been able to identify the tradeoffs associated with any discrepancies that are found. I have only used this method a few times however. If all goes as planned we will be able to optimize the phase tracking.

If you prefer to just move forward using the Audyssey distances that's fine. That would save you the final round of confirmation testing. I will still do the analysis to see what distances I would have recommend and show you the calculated results.


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## jtalden (Mar 12, 2009)

hifiaudio2,
If it is not too much trouble please take a 1m near field measurement of each of the 3 front main speakers. Instead of just one of them. The new data suggest that there may be a polarity issues with the FL TW. It appears to be reversed from the CC and FR TWs. The near field measurements will confirm if this is really the case.


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## hifiaudio2 (Jun 25, 2014)

I will get these new measurements done ASAP either today or tonight. Thanks for all of you time.


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## hifiaudio2 (Jun 25, 2014)

Here are the nearfield measurements. Again, since the speakers are behind the screen, I cant be 100% that I am directly in front of and at the height of the coaxial mid / tweeter. But it should be very close. I should be 2.5 - 3 ft in from of them from where I put the mic.

The right speaker has a drastic high frequency rolloff. Need to figure out whats going on there, too.


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## jtalden (Mar 12, 2009)

The polarity appear to be correct as phase tracks very well up to about 3kHz. It is not too bad above that until about 15kHz. Above that, the SPL and phase of the FR deviates markedly from the other two speakers.









Possibly this result is just due to a close reflective object? Having no experience with these speakers or your setup I am not in a good position to guess at the cause. 

Either way, it will not affect the proposed 80Hz XO timing so it is a separate issue. I will provide a recommendation on distances today or tomorrow.


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## hifiaudio2 (Jun 25, 2014)

Ok thanks. I will shoot this graph over to Mark Seaton and get his input on the phase.


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## jtalden (Mar 12, 2009)

The graph will not do him much good for analysis by itself. You will need to offer him the REW file so he can do his own settings and review the other graphs as well.


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## jtalden (Mar 12, 2009)

*Speaker Distance process without REW loopback timing:*
This is a very difficult process to explain clearly. I have decided to provide the distance recommendations and some informative comments and graphs. It will not fully explain the process, but I will try to answer any questions.

*Distance Recommendations:*
The best phase tracking in the XO range is obtained by changing the SW distance setting in the pre/pro by +8.1ft and also inverting the SWs polarity relative to the mains. The initial SWs distance setting was 14.0ft. The new distance should now be 22.1ft. To invert the 4 SWs there probably is a control to do that in the Xilica on the input channel used. The measured distances and polarities for the mains remain unchanged.

*Process Results and Notes:*
The Phase tracking in the XO range and the resulting SPL charts will then look like this:

































Note that the phase tracking is very good for the FL and FR mains, but the CC phase rotates 360° in the middle of the XO range. That puts an SPL null at 70Hz where the CC is 180° out of phase with the SWs. This is the voice channel for movies so the impact will probably be negligible. Many of us have a null someplace in this range and it is better in the CC than the FL or FR in my opinion. Not many voices go that low.

The shift needed for the SWs was determined by measuring the amount of offset required in the SWs IR to achieve close phase tracking. Shown below is the measurement of the final SWs IR shift: 









One SWs IR represents the experimentally determining initial SWs IR location. It is only position that will provide the original measured SWs+CC SPL result. The other SWs IR location is the one that provided the closest phase tracking. We can also see that it was necessary to invert the SWs IR. The process uses REW's arithmetic operations to see the SPL and phase of the calculated SWs+CC after each trial IR shift is made.

*Next Steps:*
It would be a good idea to confirm that these settings actually result in the predicted charts. If I made no mistakes in the process, they will. You would need to measure again from the LP using all same conditions as before except for the new SWs distance and new SWs polarity. There would be 7 new measurements. We would be able to confirm the distance settings are correct by looking at the SPL chart for XO range SPL support as in the 3 charts above. The Phase charts in the 3 SWs+main will also track similarly to the 3 above.

Questions?


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## hifiaudio2 (Jun 25, 2014)

It looks like the polarity adjustments only had a positive effect for the right channel.

I took measurements with positive and negative polarity for all three channels with the sub, and then separate measurements for the three channels along and the subs alone in case you needed those again. I wasnt quite sure which 7 measurements you meant. Hopefully I covered the scenarios you need.

Had an issue with the uploader taking this larger file so here it is in a Dropbox link:

https://www.dropbox.com/s/t2trro3mheo5hmk/sw distance 22.1 ft and polarity adjustments.mdat


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## jtalden (Mar 12, 2009)

hifiaudio2 said:


> I wasnt quite sure which 7 measurements you meant.


The 7 needed measurements were included. These measurements confirmed the recommended distances settings are optimized for phase tracking. This is not shown here, but the results are the same as the calculated results predicted in Post 46. The SPL charts shown below used this measured data and it also matches well to the calculated SPL prediction in Post 46.



























> It looks like the polarity adjustments only had a positive effect for the right channel.


I am not sure what the comparison is. If we are comparing SPL support now to SPL measurements that were initially found using the RTA method then the FR and FL would be expected to be very similar. They cannot be worse as their phase tracking is now optimized. The CC would be worse as there is now a 70Hz null due to the room mode. There is still slight SPL support in the XO range surrounding the null, but the unavoidable null is the dominate feature.

The null is unavoidable because I applied a constraint to our setup (possibly undisclosed).
> Main speaker distances to be set such that the sound from all 3 front mains arrive at the LP at the same time. [We set the distances of the mains to the measured distances to achieve that.]

We could have found a distance setting that removed the null in the SWs+CC, but would have resulted in a null in the SWs+FL and SWs+FR. If we removed the constraint then we could have set the mains such that there was good support for all 3 front speakers. That setting would require the CC channel sound to arrive about 20ms before the other channels. That may not be a sound quality issue for most movies since it is in the CC voice channel; I don't know. I would expect to be a significant problem with music material that uses the CC.


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## hifiaudio2 (Jun 25, 2014)

Ok thanks. So based on that you are saying we have found the correct settings for the distances? What about the distances of the mains vs the surrounds? Since we are no longer taking the DSP delay into account, wont this create an incorrect delay for the mains by only using their physical delay and not electrical while my surrounds have no DSP and are also using the physical distance for delays?


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## hifiaudio2 (Jun 25, 2014)

Oh and based on what you see in the measured results should I leave my subs at negative polarity?


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## jtalden (Mar 12, 2009)

hifiaudio2 said:


> Ok thanks. So based on that you are saying we have found the correct settings for the distances?


Yes.

[There are other good alignments, but this one best meets the main objectives.]



> What about the distances of the mains vs the surrounds? Since we are no longer taking the DSP delay into account, wont this create an incorrect delay for the mains by only using their physical delay and not electrical while my surrounds have no DSP and are also using the physical distance for delays?


I suggest the measured distances be used. I would expect that the sound quality impact of the surrounds is minimal compared to the fronts.

[Since there is no speaker amp DSP you could subtract 1ft if you want as a good guess as to the impact of no DSP. A 1 ft error is not a major error however even on the front mains. Also, unless the Surround speakers are identical to the mains this guess is very suspect as the XO and speaker delays be different. That is, the speaker will have different phase rotation. Then it becomes a tradeoff as to what freq range to align; the SW XO handoff, the 1k-4k midrange where the ear is most sensitive, or possibly the TW arrival. These are questions that we don't know the answer to, and if we knew the answer, we would need the REW Loopback Timing feature active to find the needed delays.]


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## hifiaudio2 (Jun 25, 2014)

Ok cool. Thanks again.. a ton.. for all of your help!


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## jtalden (Mar 12, 2009)

hifiaudio2 said:


> Oh and based on what you see in the measured results should I leave my subs at negative polarity?


Yes, Otherwise as you recent measurements show:
> The SPL support in the XO range is worse.
> The direct sound from the SWs (vs the W in the mains) will track 180° offset through the XO range. As a result, those speakers will work against each other throughout that range. The phase will quickly rotate 180° at the 70Hz acoustic XO freq.

You questioned the SWs+FR so below are some charts and the resulting difference phase and SPL for SWs with the original polarity vs inverted polarity:

Below with SWs inverted, the SWs+FR (darker blue-green) phase and the individual SWs and FR phase tracks closely through the XO range:









Below with SWs original polarity, the SWs+FR (yellow) phase jumps between the SWs and FR phase traces that are spaced at about 180° apart throughout the XO range:









Below the SPL difference in the XO range is shown. The SWs+FR trace using the inverted SWs (darker blue-green) stays above the SWs+FR trace using the original SWs polarity (yellow).


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## hifiaudio2 (Jun 25, 2014)

Just wanted to say thanks again. The room sounds terrific now.. Bass attack and decay seems very natural. You were a big help!


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## jtalden (Mar 12, 2009)

Thanks.
It's good to hear (so to speak). :sn:


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## FargateOne (Mar 3, 2015)

jtalden said:


> Thanks.
> It's good to hear (so to speak). :sn:


WOW! I do not understand the half that I read but your dedication is impressive!


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