# Port Timing



## Lumen (May 17, 2014)

Both my mains and the sub are ported. I remember reading a while back that ported speakers disrupt relative timing between speakers and subs. Is this true and if so, can it be easily taken care of with external delays provided by a miniDSP or equivalent?


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## jtalden (Mar 12, 2009)

Ported speakers just have a different SPL and phase response (different rolloff rates). 
Ported or not, the objective is just to create close phase tracking between the SW and mains.

If the best timing alignment results in the phase crossing at the acoustic XO rather than tracking closely throughout the entire XO range it is possible to fine tune it by changing the SPL/phase rolloff rate of one of drivers:
> Plugging the mains ports will change the rolloff rate from 24 to 12 dB. 
> Changing the relative filter settings (as from LR24/LR24 to LR24/But18) for the LPF and HPF XO filters may be an option.
> Changing the relative XO filter frequencies (HPF vs LPF settings) also has some effect.
> Possibly some the Phase control dials on some SWs will shift phase rate of the rolloff through the XO range. Others may just be adjusting the overall SW delay. I don't have any SW's with those controls to test.

It all depends on the setup controls available to the hobbyist. Most people don't have many, if any, options. Fine tuning like that is very complicated and time consuming. It's the playground of dedicated tweakers. It is very unlikely to be detectable in sound quality. 

Just pick the best phase tracking for the XO settings you choose. There are better way to spend one's time.


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## DqMcClain (Sep 16, 2015)

jtalden said:


> Ported speakers just have a different SPL and phase response (different rolloff rates).
> Ported or not, the objective is just to create close phase tracking between the SW and mains.
> 
> If the best timing alignment results in the phase crossing at the acoustic XO rather than tracking closely throughout the entire XO range it is possible to fine tune it by changing the SPL/phase rolloff rate of one of drivers:
> ...


Yeah... you can spend a lifetime on this problem, and only hear the most minute of improvements. The big question is how dissatisfied you are with your current sound... if you're pretty happy at the moment, I wouldn't recommend going down that rabbit hole. Everything suggested above is spot-on, but also easier said than done in a lot of cases.


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## Gdaddy (Oct 29, 2016)

Lumen said:


> Both my mains and the sub are ported. I remember reading a while back that ported speakers disrupt relative timing between speakers and subs. Is this true and if so, can it be easily taken care of with external delays provided by a miniDSP or equivalent?


I read the following article and his explanation made a lot of sense about this very topic.

It seemed worth the effort to give it a try and ended up following his advice for my 'music only' system. I'm amazed at how much better/clearer and how the sound is 'louder' on lower volume setting. Well worth the effort and I highly recommend it.

All my ports are sealed and my mains are crossed over @ 80hz as directed. I am using sub drivers designed for a sealed cabinet. (NHT)

BTW... an important part of the set up was using the subwoofer location in figure Fig 7. 'An asymmetrical layout.' 











This made a huge difference in my small 13' x 15' room. I can actually balance the bass at the listening position by using the volume control on the two subwoofers. Very cool idea. I run the sub closest to the sofa at a low crossover and slightly lower volume so it's not detectable in the least. Both subs are firing aimed away from the listening position at the wall to cut down any localization. The bass is very tight and it really does "fatten up the base". So now the system plays louder on less volume. Helped with nulls also.

_"A ported sub for home use is even more wrong than ported mains. Now you would be attempting to acoustically add together in the room at least SIX low frequency sources with differing phase and frequency slope conditions: the LF drivers in your two mains, their ports, the sub driver, and its port." _


http://www.soundoctor.com/whitepapers/subs.htm


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## jtalden (Mar 12, 2009)

Gdaddy said:


> _"A ported sub for home use is even more wrong than ported mains. Now you would be attempting to acoustically add together in the room at least SIX low frequency sources with differing phase and frequency slope conditions: the LF drivers in your two mains, their ports, the sub driver, and its port." _
> 
> 
> http://www.soundoctor.com/whitepapers/subs.htm


This quote and some other comments in the linked article reflects a partial misunderstanding of the SW to mains XO setup issues in my opinion: 
> I see no technical argument for a clear preference of a ported Vs sealed SW. They have slightly different advantages/disadvantages so for a given situation one may be a little better choice than the other. Pointing to 1 or 2 advantages/disadvantages without context to how it helps or hurts a particular situation is not helpful.
> We also cannot predict if ported Vs sealed mains will work more ideally for phase tracking in a given situation. It is the overall system acoustic XO characteristics that is main factor. This is a function of the room and SW placement as well as the electrical XO settings (including the important delay setting). 
> The typical small listening room is often the primary actor in the success of the setup. Only careful measurements will determined the best setup from the various options available. Most often, due primarily to room acoustics of a given setup, it is a matter of choosing a compromise XO setting between several less than ideal solutions.


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## Lumen (May 17, 2014)

jtalden said:


> Ported speakers just have a different SPL and phase response (different rolloff rates).
> Ported or not, the objective is just to create close phase tracking between the SW and mains.
> 
> If the best timing alignment results in the phase crossing at the acoustic XO rather than tracking closely throughout the entire XO range it is possible to fine tune it by changing the SPL/phase rolloff rate of one of drivers:
> ...


Many thanks for your detailed response, and for saving me from a thousand deaths! Not being a dyed-in-the-wool tweaker, and having a processor with limited setup controls, I'm more than happy to take your advice to "settle" for phase tracking. Now to see if I understand correctly. Phase tracking uses FR measurements to verify a sub's phase control is set to provide good SPL support through the crossover region. Phase plot analysis is not needed, correct? 




DqMcClain said:


> Yeah... you can spend a lifetime on this problem, and only hear the most minute of improvements. The big question is how dissatisfied you are with your current sound... if you're pretty happy at the moment, I wouldn't recommend going down that rabbit hole. Everything suggested above is spot-on, but also easier said than done in a lot of cases.


Appreciate the confirmation! My OCD wouldn't stay under wraps very long under those conditions. To answer your question: I'm very dissatisfied right now. I'm in the early stages of renovating my HT room, and thought I had fine-tuned my speaker locations - until I brought in some room treatments, that is. I'll try starting over by introducing them individually. I was hoping to save some measurement time, but I now realize there are no shortcuts to doing it right (adding treatment without good reason can do more harm than good).


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## jtalden (Mar 12, 2009)

Lumen said:


> Now to see if I understand correctly. Phase tracking uses FR measurements to verify a sub's phase control is set to provide good SPL support through the crossover region. Phase plot analysis is not needed, correct?


Yes, that is one method that provides good results.
> Set delays appropriate for the distances to speakers
> Increase the delay on the SW by 4.00 ms.
> Sweep (or RTA) measure SW+Lmain+Rmain 8 times reducing the SW delay by about 1.00 ms for each successive measurement. 
> Choose the SW delay setting that provides the best XO range SPL support. 

If you prefer that I confirm the settings I would need an mdat file:
> Acoustic timing activated on Left channel
> XO and delay settings activated
> Mic at LP
> Sweep:

FL
FR
SW (redirected bass from right or left channel, not an LFE channel)

REW analysis of those 3 measurements allows me to do essentially the same thing while also being mindful of the phase tracking.


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## willis7469 (Jan 31, 2014)

Gdaddy said:


> _"A ported sub for home use is even more wrong than ported mains. Now you would be attempting to acoustically add together in the room at least SIX low frequency sources with differing phase and frequency slope conditions: the LF drivers in your two mains, their ports, the sub driver, and its port." _
> 
> 
> 
> ...



I completely agree with JT on this.


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## Lumen (May 17, 2014)

jtalden said:


> This quote and some other comments in the linked article reflects a partial misunderstanding of the SW to mains XO setup issues in my opinion:
> > I see no technical argument for a clear preference of a ported Vs sealed SW. They have slightly different advantages/disadvantages so for a given situation one may be a little better choice than the other. Pointing to 1 or 2 advantages/disadvantages without context to how it helps or hurts a particular situation is not helpful.
> > We also cannot predict if ported Vs sealed mains will work more ideally for phase tracking in a given situation. *It is the overall system acoustic XO characteristics that is main factor. This is a function of the room and SW placement as well as the electrical XO settings (including the important delay setting).*
> > The typical small listening room is often the primary actor in the success of the setup. Only careful measurements will determined the best setup from the various options available. Most often, due primarily to room acoustics of a given setup, it is a matter of choosing a compromise XO setting between several less than ideal solutions.





willis7469 said:


> I completely agree with JT on this.


The word "guru" comes to mind.


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## Lumen (May 17, 2014)

jtalden said:


> Yes, that is one method that provides good results.
> > Set delays appropriate for the distances to speakers
> > Increase the delay on the SW by 4.00 ms.
> > Sweep (or RTA) measure SW+Lmain+Rmain 8 times reducing the SW delay by about 1.00 ms for each successive measurement.
> ...


Certainly a generous offer that's hard to refuse! How do you find the time?!

To try and provide robust data the first time, I have a few more questions:
Delay can be converted to distance if multiplied by 1.125ft/msec, correct?
Speaker distance is measured from LP to baffle (single plane for all distances). How do you measure from LP to sub, line-of-sight to the driver's center?
Should I specify a 12 or 24dB/octave subwoofer LPF slope? Or does that warrant one set of measurements for each scenario?


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## jtalden (Mar 12, 2009)

1. Yes
2. If I am doing the analysis just use the on-floor distances to the baffles. The distances are theoretically measured as line of sight LP to the baffle at driver height. The floor distances are plenty good enough as it's the relative distances to the mains that is more important than the absolute distances. The SW distance is the one that may change distance anyway so the starting distance is not a big concern. It's just good to know that it was approximately correct to start with. Otherwise a big needed distance change would make me think I made a calculation mistake.
3. If the SW LPF is the only change (the mains stay the same slope) then just measure the SW with each setting and if there is a significant difference we can chose the setting that provides the better results. The total measurements is then 4 rather than 3.
> Lmain
> Rmain
> SW12
> SW24

Please advise the XO settings and distance settings used. That can be done right in the REW notes for each measurement. Please set the sweep so it extends well past the XO range. I normally just sweep full range.


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## Lumen (May 17, 2014)

Okay jtalden, thanks! I should be able to make measurements soon.


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## Lumen (May 17, 2014)

Well, maybe not so soon. :R
I was unable to acquire a full set of measurements with the acoustic timing reference. And I'm not so sure the ones I did take are valid.

*REW Configured for ASIO / HDMI connection*:
AVR is recognized and active
Only 2 channels appear in the OUTPUT selector instead of 6 as shown in Windows Manage Audio Devices
Scarlett 2i2 input (mic) is recognized but IDLE <---- SHOWSTOPPER

*REW Configured for JAVA / RCA connections*:
Both channels properly appear in the I/O selectors of the PREFERENCES window.
Either channel is able to be selected as an acoustic timing reference of the MEASUREMENTS window.
Short-burst timing signal is heard before full-range test signal
Test signal plays through L+R+SUB <---- SHOWSTOPPER

Now this is where I fell on my face... how do you measure ONLY the right channel with the left channel assigned as an acoustic reference? Output-1 (left) of my 2i2 soundcard is connected to both analog inputs of my AVR through a Y-splitter. So when the AVR is in stereo mode for this measurement, both channels (and the sub) play the full-range test signal. The only way I can see to silence the left channel is to unplug its RCA connection after the timing signal is generated. There must be a better way! Is the solution to use the same speaker for timing as measuring? How then does that work for the sub, which needs the L/R inputs connected to receive summed-to-mono bass below the xover?

Aside from manipulating AVR inputs as shown below (lifted from the REW101 Guide), additional speaker combinations can be created by disconnecting power amp inputs:


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## Lumen (May 17, 2014)

Never mind... got the ASIO/HDMI config working ...woohoo!


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## jtalden (Mar 12, 2009)

I didn't read carefully all your posts regarding the 2i2 but be advised I never got ASIO4ALL to work consistently with that unit. It only was stable using the Focusrite ASIO driver. That doesn't let you use the HDMI though if I understand correctly. I just use a loopback cable for timing and send the analog signal to the driver using an analog cable. That may be a real pain if you cannot easily mute/unplug the other drivers so they don't play. 


So hopefully ASIO4ALL will be stable for you. 


I am not following closely as I have no power at home; 665,000 homes impacted. I'm working at a library now. They say it may be several days for some customers get back up. I'm hoping they get me some power sooner than that though.


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## Lumen (May 17, 2014)

I'm so sorry. I hadn't heard. Take care of you and yours! 

Sent from my iPhone using Tapatalk


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## willis7469 (Jan 31, 2014)

Sorry JT. Didn't hear about anything over that way. Over here in Mn we've had some crazy winds. Up to 60mph I heard. I hope you come out ok.


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## Lumen (May 17, 2014)

willis7469 said:


> I hope you come out ok.


Absolutely +1. And thank you for the heads-up on the Focusrite driver. Now stop it and get some rest!


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## Lumen (May 17, 2014)

jtalden said:


> I'm hoping they get me some power sooner than that though.


It was good to hear you were in the first half!



jtalden said:


> ....
> 2. If I am doing the analysis just use the on-floor distances to the baffles. The distances are theoretically measured as line of sight LP to the baffle at driver height. The floor distances are plenty good enough as it's the relative distances to the mains that is more important than the absolute distances. The SW distance is the one that may change distance anyway so the starting distance is not a big concern. It's just good to know that it was approximately correct to start with. Otherwise a big needed distance change would make me think I made a calculation mistake.
> 3. If the SW LPF is the only change (the mains stay the same slope) then just measure the SW with each setting and if there is a significant difference we can chose the setting that provides the better results. The total measurements is then 4 rather than 3.
> > Lmain
> ...


Here's my first stab at the data you asked for. The measurements are for the room after acoustic treatments. I have measurements for the baseline and intermediate steps if you'd like to see any of those. Please let me know if there's anything I should have done differently.
View attachment Room Layout 4A (12dBpo 5xTraps).mdat

View attachment Room Layout 4A (24dBpo 5xTraps).mdat


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## jtalden (Mar 12, 2009)

Lou,
There is a problem with this data. The IR positions are inconsistent. I am still trying to fully understand what may have gone wrong. There appears to be some problem with the loopback timing setup. We need to assure loopback timing is working properly before we try again.

Per the info panel in REW:
> The Mic is plugged into the left channel

Given that case:
> The TRS/TRS (or TS/TS) loopback cable should be connected to the 2i2 right output to right input.
> The Timing Channel should be set to 'Right' in REW. 
> The measurement channel should be set to 'left' and the left output of the 2i2 is connected to the receivers left CD/Aux/DVD/etc (not multichannel) input for measuring the left main and to the right input for measuring the right main. [there are various ways to do this differently depending on the equipment being used. I didn't go back and try see what equipment you have or how it is configured.
> The music mode should be 'Stereo' for evaluation of the 2 front channels.

The info panel in REW shows:
> The timing channel set to 'left'. That is the mic position! Possibly that is the only problem? 
> The output/measurement channel is set to 'both'. I am not sure if that would explain the issue. I would always use 'left' in this case. 

Please consider what may be wrong and correct it. To provide more specific help I would need all your setup information.

You should remeasure the left and right mains alone several times and confirm to yourself that the IR location and shape is repeatable for each main channel and that the left and right channel IR locations are very close to each other when the mic is carefully centered and the distances/delays are for each channel are set identically.

Once we confirm the measuring setup then we can then trust the 4 measurements that I need for my analysis. You can compare my recommendation to the results you obtained using trial and error with the SW phase control. That method can probably work just fine, but I have no experience with it.


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## Lumen (May 17, 2014)

jtalden said:


> Lou,
> There is a problem with this data. The IR positions are inconsistent. I am still trying to fully understand what may have gone wrong.


Ha-hah, just like software - my measurements always need debug! After measuring all FR, I first click on a single graph to the left and then the IMPULSE button in the upper right. Next I click on LIMITS and GENERATE MINIMUM PHASE (taking defaults). I can scroll around to find the trace, but the only way I can really come up with anything resembling what I've seen in the guides and here on the site is to enter a t=0 OFFSET equal to the delay in msec shown in that particular measurement's notes section. I may not have done that for every measurement that needed it.



jtalden said:


> There appears to be some problem with the loopback timing setup. We need to assure loopback timing is working properly before we try again. Per the info panel in REW:
> > The Mic is plugged into the left channel
> 
> Given that case:
> ...



Yes. CH01 IN = Mic.
Yes. Loopback cable connected between CH02 IN and CH02 OUT.
No. AFAIK, the timing Channel can only be selected when using HDMI. The MEASUREMENTS PANEL allowed me to specify whether no timing ref is used, a loopback timing ref is used, or an acoustic timing ref is used. But for JAVA with hardwired connections, REW does not offer a selection for left or right timing channel.
Yes. I set the measurement channel to LEFT using the INPUT selector in PREFERENCES.
L ONLY: 2i2 CH01 OUT to Left Analog IN only / Mode=Stereo / Sub=Off.
R ONLY: 2i2 CH01 OUT to Right Analog IN only / Mode=Stereo / Sub=Off.
C ONLY: 2i2 CH01 OUT to Left Analog IN only / Disconnect AVR center out & right out / Connect AVR left out to amp center in / Mode=Stereo / Sub=Off.
SUB ONLY: 2i2 CH01 OUT to Left & Right Analog IN / Turn off power amp / Mode=Stereo / Sub=On.
C+SUB: Same as C ONLY, except turn sub on.
L+R+SUB: 2i2 CH01 OUT to Left & Right Analog IN / Disconnect AVR center out / Mode=Stereo / Sub=On




jtalden said:


> The info panel in REW shows:
> > The timing channel set to 'left'. That is the mic position! Possibly that is the only problem?
> > The output/measurement channel is set to 'both'. I am not sure if that would explain the issue. I would always use 'left' in this case.


After taking new measurements exercising the new settings noted above, the info panel still shows the timing is being taken from LINE OUT = LEFT. I'm assuming that LEFT = CH01 for the 2i2. This happened even after changing OUTPUT in the MEASUREMENT PANEL from BOTH to LEFT. I will retry the measurements with OUTPUT set to RIGHT to see if that fixes the issue before I ask you to reanalyze.



jtalden said:


> Please consider what may be wrong and correct it. To provide more specific help I would need all your setup information.


Your help is much appreciated. You shouldn't have to hold my hand with every aspect of setup, but I may not even be aware that's where the problem lies. I'd like to try your suggestions and then revisit the issue. I should have another mdat file tomorrow.



jtalden said:


> You should remeasure the left and right mains alone several times and confirm to yourself that the IR location and shape is repeatable for each main channel and that the left and right channel IR locations are very close to each other when the mic is carefully centered and the distances/delays are for each channel are set identically.
> 
> Once we confirm the measuring setup then we can then trust the 4 measurements that I need for my analysis. You can compare my recommendation to the results you obtained using trial and error with the SW phase control. That method can probably work just fine, but I have no experience with it.


Boy do you ever have confidence in me! I really have no clue what I'm doing when generating IR data. Can you tell me if I should be offsetting t=0 per the delay specified in the notes section? That's the only way I've even been able to find the trace! I'll try the procedure you mention above. Who knows, I may make you proud!


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## jtalden (Mar 12, 2009)

Lumen said:


> After measuring all FR, I first click on a single graph to the left and then the IMPULSE button in the upper right. Next I click on LIMITS and GENERATE MINIMUM PHASE (taking defaults). I can scroll around to find the trace, but the only way I can really come up with anything resembling what I've seen in the guides and here on the site is to enter a t=0 OFFSET equal to the delay in msec shown in that particular measurement's notes section. I may not have done that for every measurement that needed it.


You don't need to do any changes to the 4 measurements after taking them. Most things like 'calc minimum phase' won't hurt anything, but for the analysis I am doing, it is important not to offset the IRs from their original positions. The whole idea with loopback timing is that the IR's will be placed in time relative to the loopback timing signal. That allows us to do an analysis that is based on the relative arrival time of the sounds of the different speakers. To see the relative locations of the IRs just scroll the IR overlay chart to the 55-70 ms range.

The chart below for the 24 dB data shows the arrival time of the left and right main IRs in the data you provided. The left main sound arrived at about 65 ms and the right main at about 60 ms. This is a difference of about 5 ms suggesting there is about a 5 foot difference in the distance to the mic. If the mic was exactly centered the 2 IR's would be located at the same time. If the mic was off center an inch or so the IR's would be offset only maybe 0.02 ms or so. 

For the analysis I do need to shift them all back near 0 ms, but they are all shifted the same exact distance so that the relative timing relationship between them is unchanged. Now reviewing this data again, the 24 dB data contains the only obvious problem. The left and right channel IR positions in the SW12 dB data looks fine. That data may be good to use. To be safe you may want to take the 4-5 measurements I need again (L, R, C?, SW12, SW24). Feel free to include the center main also and I will include that in the analysis as well. I can and will analysis the current SW12 dB and make a recommendation on it alone if you like. I also could also pull in the SW24 measurement into this analysis, but the location of the SW24 vs SW12 is questionable also so that may confuse the analysis. Let me know if you want me to try to use this data or if you intend to measure again.









Regarding the setup info you provided:
I didn't see any obvious problem with your Java settings or connections. I don't regularly use Java though so I am not as familiar with it. It should work fine though. I use the 2i2 with the Focusrite ASIO driver. I suspect the problem is with the IR offset you made to one/some of measurements and not on the settings and connections.


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## Lumen (May 17, 2014)

jtalden said:


> You don't need to do any changes to the 4 measurements after taking them. Most things like 'calc minimum phase' won't hurt anything, but for the analysis I am doing, it is important not to offset the IRs from their original positions. The whole idea with loopback timing is that the IR's will be placed in time relative to the loopback timing signal. That allows us to do an analysis that is based on the relative arrival time of the sounds of the different speakers. To see the relative locations of the IRs just scroll the IR overlay chart to the 55-70 ms range.


This makes so much more sense now. Thanks for the clarification!



jtalden said:


> The chart below for the 24 dB data shows the arrival time of the left and right main IRs in the data you provided. The left main sound arrived at about 65 ms and the right main at about 60 ms. This is a difference of about 5 ms suggesting there is about a 5 foot difference in the distance to the mic. If the mic was exactly centered the 2 IR's would be located at the same time. If the mic was off center an inch or so the IR's would be offset only maybe 0.02 ms or so.


A 5 foot difference is certainly suspect when actual distance is the same within an inch! I'm at a loss to explain the discrepancy.



jtalden said:


> For the analysis I do need to shift them all back near 0 ms, but they are all shifted the same exact distance so that the relative timing relationship between them is unchanged. Now reviewing this data again, the 24 dB data contains the only obvious problem. The left and right channel IR positions in the SW12 dB data looks fine. That data may be good to use. To be safe you may want to take the 4-5 measurements I need again (L, R, C?, SW12, SW24). Feel free to include the center main also and I will include that in the analysis as well. I can and will analysis the current SW12 dB and make a recommendation on it alone if you like. I also could also pull in the SW24 measurement into this analysis, but the location of the SW24 vs SW12 is questionable also so that may confuse the analysis. Let me know if you want me to try to use this data or if you intend to measure again.


Please run an analysis on the existing SW12 set. The set representing the 24dB/octave slope is of little use to me, because the steeper slope does not provide better support through the crossover region (80Hz).




jtalden said:


> Regarding the setup info you provided:
> I didn't see any obvious problem with your Java settings or connections. I don't regularly use Java though so I am not as familiar with it. It should work fine though. I use the 2i2 with the Focusrite ASIO driver. I suspect the problem is with the IR offset you made to one/some of measurements and not on the settings and connections.


What exactly do you mean by, "use the 2i2 with the Focusrite ASIO driver"? REW only offers ASIO4ALL and JAVA. How do I select the Focusrite ASIO driver?


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## jtalden (Mar 12, 2009)

I will do the SW12 analysis today.

Just continue to use the Java driver. I think you have it working okay. Hopefully using the loopback cable several measurements were made on the same speaker and it was confirmed all the impulses fell at the identical time on the impulse chart. As long as there is timing repeatability, and it's possible to route the signal to the measurement speaker, that is all that is needed.


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## jtalden (Mar 12, 2009)

Lou,
I reviewed the data you provided for SW12:
> The measurements there were not what I need for my normal phase tracking analysis so that method couldn't be used.
> The data there does follow a good trial and error method. One I mentioned in the 4th bullet of Post-2. That is; using the phase control on the SW to see which setting best supports and smooths the SPL response. From the data we find that the last measurement was the best setting. That setting is not labeled, but the sequence before it would suggest that it is with the phase control set to 180°. The setting of 135° (next to last measurement) is almost identical. Either of these 2 settings looks very good for SPL support.

We could get new measurement that fit my requirements for my normal phase tracking analysis, but that is not likely to result in any significant improvement to either of these 2 options.

I suggest you use the settings of the final measurement in that series. It works very well for the left and right channel. Try it for the center channel to assure it works well there also. If it does not, do not change the SW settings. Just adjust the distance of the center main ±1, 2, 3 ft and choose the distance that provides the best SPL response. It will probably look good at the current setting.


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## Lumen (May 17, 2014)

jtalden said:


> To be safe you may want to take the 4-5 measurements I need again (L, R, C?, SW12, SW24). Feel free to include the center main also and I will include that in the analysis as well.


Sorry, I did not mean to cause extra work for you. I got carried away following general measurement instructions in the REW101 Guide instead of your own. I could certainly use any recommendation you can offer for the center, so if it's not too much trouble, please include it. TIA!


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## jtalden (Mar 12, 2009)

I did cover the center channel issue in the last paragraph in Post-25. It requires you to do the same kind of test you did on left and right, but instead of the SW phase control (leave that at 180°), change the center channel distance to find the best setting for SPL.


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## Lumen (May 17, 2014)

jtalden said:


> Lou,
> I reviewed the data you provided for SW12:
> > The measurements there were not what I need for my normal phase tracking analysis so that method couldn't be used.
> > The data there does follow a good trial and error method. One I mentioned in the 4th bullet of Post-2. That is; using the phase control on the SW to see which setting best supports and smooths the SPL response. From the data we find that the last measurement was the best setting. That setting is not labeled, but the sequence before it would suggest that it is with the phase control set to 180°. The setting of 135° (next to last measurement) is almost identical. Either of these 2 settings looks very good for SPL support.
> ...


Thank you once again for your time and attention to detail. I'm disappointed in myself for not supplying what you needed. I'm also disappointed we couldn't take this exercise to completion. I was hoping to learn more about IR graphs, but I feel like I've failed to grasp the basics as demonstrated by others in similar threads. Part of the issue may be my lack of a clear-cut goal, which was initially vague but later morphed into timing adjustment between mains and sub. If we stop now, my take-away would be that timing adjustments are a tweaker's playing field which offer (for most) a relatively small subjective return-on-investment. I would also include that satisfactory results can be obtained through the phase tracking method, and/or by manipulating distance settings. To my credit, however, I did learn quite a bit about ASIO4ALL and some nuances of the measurement process. All valuable lessons to carry forward!



jtalden said:


> I suggest you use the settings of the final measurement in that series. It works very well for the left and right channel. Try it for the center channel to assure it works well there also. If it does not, do not change the SW settings. Just adjust the distance of the center main ±1, 2, 3 ft and choose the distance that provides the best SPL response. It will probably look good at the current setting.


Perfect - exactly the advice I was looking for! This information is golden to me, so thanks for sharing! I sincerely appreciate your effort surrounding these issues, and hope to learn more from you in the future.


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## jtalden (Mar 12, 2009)

Glad I could help.


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