# XTZ Room Analyzer or Dayton Omnimic



## randyc1 (Jul 20, 2011)

Hey Guys ! I'm looking for a room analyzer and was wondering which i should choose . I am a begginer so i would like something simple and accurate . Thanks


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## Kal Rubinson (Aug 3, 2006)

What do you want to measure?


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## SAC (Dec 3, 2009)

Start out with RoomEQWizard.

Especially as you state that you are a beginner, if and when you outgrow its capabilities or need additional features, you might then consider products like ARTA or EASERA (and I would seriously suggest downloading their manuals for use as additional tutorial resources).

ARTA is a 'best buy' and EASERA is a comprehensive package that integrates well with other more specialized industry standard analysis and design components - albeit at a much higher cost of entry.

Short of making the jump to those professional products, REW is hard to beat for the capabilities and its cost - free! The products you mention not only cost more, but do not provide as comprehensive a list of features as REW. Plus you have the benefit of online support here on this forum.


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## randyc1 (Jul 20, 2011)

Kal Rubinson said:


> What do you want to measure?


Just wanted to measure in room response of my current 5.1 system


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## randyc1 (Jul 20, 2011)

SAC said:


> Start out with RoomEQWizard.
> 
> Especially as you state that you are a beginner, if and when you outgrow its capabilities or need additional features, you might then consider products like ARTA or EASERA (and I would seriously suggest downloading their manuals for use as additional tutorial resources).
> 
> ...


I've read so many posts of people having a hard time with REW , sound card and RS meter.
People using OmniMic said they could get in room FR measurements within minutes ??


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## Kal Rubinson (Aug 3, 2006)

randyc1 said:


> Just wanted to measure in room response of my current 5.1 system





randyc1 said:


> I've read so many posts of people having a hard time with REW , sound card and RS meter.
> People using OmniMic said they could get in room FR measurements within minutes ??


That is exactly why I asked. You can get FR measurements equally rapidly with either XTZ or Omnimic. There is more generous guidance with XTZ but OmniMic can do more if you know what to do and can interpret the help files. Why don't you download the help/docs and see if they are revealing to you?


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## SAC (Dec 3, 2009)

OK, I'll play devil's advocate for a few minutes - don't panic...:laugh:

So you are willing to pay $300 for just a frequency response and a fancy SPL meter? Are you kidding me?
And it doesn't even offer time domain measurements!
And you actually have a practical use for an oscilloscope and higher order distortion components?

As far a problems, remember that you are on a support site. This is a place where people who do not understand the basic hardware configuration, functionality of the tools or what the measurements mean come for help. Your concern is like going to the emergency room and drawing the conclusion that since many injured people go there that all of the population must be experiencing the same problems!!

But the vast majority of folks don't need to come here!

And the compatibility problems you are worried about are* not* limited to REW. They are common to many PC and Mac based IO systems (especially as the Mac is nothing but a PC in terms of hardware - literally - as it is the latest incarnation of the Intel Roadmap.)

And since I am on a roll, why stop there...:laugh:

Many are preoccupied with calibrating a mic. But don't dare ask them why they are preoccupied with this, as they are not measuring anything against some ideal standard, nor do any of their measurements require calibration such as do Noise Level Analysis (NLA) studies that are to be entered into evidence in court hearings!

Quite frankly, mic measurements are relative for most measurements. And mic calibration is a relatively easy thing to do - especially if you start with a quality mic - for which most have supplied calibration files! But instead many start with the cheapest mic they can find and expect to make it world class by calibrating it - hardly the smartest strategy.

And SPL levels? They are relative for all practical purposes! But then some will buy a RS SPL meter and simply assume the RS SPL meter to be calibrated reference standard and to be more calibrated than other sources? Really?? :rofl:Its amazing how many are appeased by assumptions and appearances! 

The irony is that the ONLY calibration that is necessary is that of a simple hardware propagation delay/latency physical loopback or file in order to account for the time delay of the signal through the associated hardware for when making time based measurements. And most folks (preoccupied with mic calibration) ironically totally ignore this procedure!

OK, now that I have had a bit of fun ( and I hope no one is too offended if I hit a bit close!)...the point is that REW is exceptionally easy to use! If you are trying to use odd Firewire devices on a Mac, you may have trouble, as Apple's support there is amazingly limited. Likewise with some of the various Firewire chipsets and hybrid USB/Firewire adapters - this issue is common throughout the _entire computer based data acquisition industry_ - and a fault of some of the hardware manufacturers - certainly not REW!

So what's the answer? Simple. Perform a bit of due diligence and investigate interfaces/pre-amps that work/do not work without problems - and there are MANY that work! Do this BEFORE you sink money into the platform! And then spend a bit of time to familiarize yourself with the tools and also with what information the various measurements provide as well as how to interpret the various measurements. There IS a learning curve. But it is not difficult! And in learning this, you will learn ALLOT about the science of acoustics the will enhance your understanding and your awareness of how to use and apply the insight provided by the tools which will then increase your productivity!

Oh, and one last thing... To invest in a measurement and analysis platform and to not get the various significant time domain tools, is in my opinion a waste of money! As the single most significant advancement in the field of acoustics in the past 40 years has been the advent of time domain measurements and the information/insight they provide! And if you are not aware of this now, PLEASE take the time to discover the significance and practical utility that they provide! You will NOT regret the effort!

The fact is, REW may be the best 'deal' in acoustical measurement software available today. There are larger and more expensive packages, but few provide the wealth of practical options and utility at such a tremendous value! John has indeed provided folks with a tremendous service!

Don't let the fact that you have discovered a source of product support scare you away from the MANY very happy users of the tools! And at the very least, give it a try - THEN, if it doesn't do what you need, then consider spending allot more money - and still facing the_* same*_ compatibility issues with IO hardware and IO drivers, pre-amps and PC/MAC platforms!

(Oh, and while becoming familiar with the measurements, also become aware of the distinction between large and small acoustical spaces and the acoustical principles that characterize each - perhaps the biggest significance being that RT (reverberation) calculations are not of use in a small acoustical space! For more info see _Sound System Engineering_, Davis and Davis, 2nd ed. or Davis and Patronis, 3rd ed.))

Also, if you PM me with you email address, I will send a chapter featuring an overview of many of the measurement tools, including time domain measurements...

Edit:
In comparing the various platforms, one significant feature jumps out. REW includes time domain response views (impulse response and envelope time curve (ETC), where many others do not. And for acoustics this is IMPORTANT. Thus, as compared to the frequency response which simply shows you a derivative non-causal lumped-together result of the interaction (superposition) of many discrete direct and indirect signals (often simply referred to, however inaccurately, as ‘reflections’); by using time domain response tools such as the envelope time curve or ETC, the time domain allows you to see all of the specific direct and indirect specular (focused) signals , and to determine each one’s gain, arrival time, direction, persistence, etc. such that one can then effectively address each discrete signal individually with respect to the others via the use of varying treatment options in order to effectively remediate issues and to ultimately tailor a quality listening space. A complex way to say that we can see each ‘reflection’, identify problems, and correct them in a way no other perspective allows.

It is specifically this 'new' ability to see the detail of the behavior of sound that allows us to specifically 'treat' a room' (and much more). Thus, by analyzing the behavior, one can surgically treat the problem causing specular signals and effectively tune a room so that the signals work together in a constructive manner, rather than causing problems. And this level of detail IS necessary, as the notion of simply applying a bunch of absorbers and maybe going further and simply adding some diffusors is NOT the solution! Treatment must be surgically targeted to solving specific problems - not simply eliminated 'reflections'!!!! Just as a surgeon does not simply remove a bunch of organs in the hopes of solving an illness, one does not indiscriminately just add room treatments thinking that this will solve a problem! But let's face reality - as this is what far too many do! Thus, the power of these tools is that you can now - with a bit of awareness of acoustic response models (the results you want) and knowledge of just how the treatments function - surgically solve the real problems, without causing more or simply moving the problems around!

This feature is critical to both speaker analysis, speaker alignment (both in terms of loudspeaker component drivers and crossovers) AND with regards to the signal alignment of multiple loudspeakers, as well as to analyzing speaker-room interactions that define small room acoustical behavior. 

I realize that some are thinking - what is he saying? I understand. I apologize for much of this being stated in a somewhat less than casual manner - but I also tried to make the descriptions sufficiently accurate without simply resorting to techno-term shorthand should one wish to delve deeper into the subject. Instead the seemingly complex adjectives and adverbs are meant to reasonably qualify the descriptions so that they provide a reasonable behaviorally based description that one might otherwise need to read several chapters to obtain (especially as we lack clarifying illustrations here!) - after which one could instead simply use a few techno-babble terms assuming you already understand the implied qualification! Hopefully, for those willing to dissect the descriptions, this will provide you with a 'Cliff's Notes' version that might help point you in the proper direction for further investigation. Otherwise, _if_ you care and the descriptions are too confusing, don't panic! PM me and I will be glad to explain things at whatever level you are comfortable and/or recommend specific resources for further investigation.


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## phreak (Aug 16, 2010)

Once again... I read, I laugh, I learn


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## randyc1 (Jul 20, 2011)

SAC said:


> OK, I'll play devil's advocate for a few minutes - don't panic...:laugh:
> 
> So you are willing to pay $300 for just a frequency response and a fancy SPL meter? Are you kidding me?
> And it doesn't even offer time domain measurements!
> ...


 WOW!, that was intense for a beginner, but thank you for taking the time !!

OK , so Omnimic you say is not the tool for me. if I understood correctly "Time Domain Correction" is one of the most important aspects in multi speaker calibration ? I have allready downloaded REW 5.0,.. I know I need a SPL meter,..a sound card , cables. My computer is about 5 yrs old and has Vista. Would it be possible for a list of exactly what i need ( name brand ,model )

A little history before we begin. Like i said i'm a begginer. For now I have a simple system : 6 year old Yammy rx-v 657 , KEF 2005.2 speaker kit . My plan was to slowly upgrade my system piece by piece. I wanted to start with basic measuring tools and learn how to use them,..and see what was going on with the system I have now. I simply want to upgrade to a mid priced level system, and do some IMPORTANT BASIC Calibrations ,( NOT become a Sound Engineer, LOL ) to get the most out of the system ! It seem like some people Fiddle and Tweak more than they actually use there systems for movies amd music !!

I was looking at buying a ONKYO TX NR 3008 with Mult EQ TX32 ,,any thoughts ??


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## Nyal Mellor (Feb 24, 2011)

Room EQ Wizard is an excellent tool which has a large number of good features. However for a complete beginner I would strongly advise going with one of the integrated hardware / software packages. Yes they are more feature limited but they are a lot quicker to use, especially for a complete beginner.

I wrote a blog article a while back comparing REQ v4 to XTZ - I don't have enough posts to add the link here but if you type in room eq wizard vs xtz in google it'll be the top result.

Disclaimer: I am retailing XTZ Room Analyzer.


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## SAC (Dec 3, 2009)

From the website for XTZ Room Analyzer:
* USB-Microphone with built in sound card 
* Easy-to-use software (Windows XP/Vista/Win 7) - Requires no computer experience 
* Cables and connectors for computer included
* 3D Spectrum analysis - Time, frequency and level
* RT60 decay time measurement
* SPL Frequency response 20-20 kHz in different time windows 
* Advanced features - Finds room modes/nodes and calculates ( using advanced algorithms), then suggests acoustically optimum countermeasures.
* High resolution room analysis - (Room Analyzer)
* High resolution measurement in the bass region 16-250 Hz (Room Analyzer)
* Frequency response mearurement - RTA (Real Time Analyzer) 20-20kHz 

Plenty of waterfall tools for analyzing room modes. In fact, both Omnimic and XTZ are great packages for any Flatlanders who simply eschew the more productive time domain tools.

And some tools useful for analyzing large acoustical spaces - when you move on to designing auditoriums and such. One such Large Acoustical Space tool is the RTxx calculations. The problem is that RTxx calculations are of limited to no value in a small acoustical space where no statistically reverberant soundfield exists (at least not at frequencies we care about, and even at those high frequencies, the level of the reverberant soundfield is lost below the ambient noise floor!)

The problem is that both Omnimic and XTZ completely lack tools for analyzing and addressing the critical region above the modal frequencies from ~300 Hz on up* where the behavior is dominated by specular ('focused') reflections. 
(*to about 10kHz, above which we don't worry too much as the wavelengths become so short and the energy content so low that the energy is mitigated by almost any surface it encounters...)

As both are represented as 'all the tools necessary for one to analyze an audio installation', I am always rather fascinated by what are often assumed to be appropriate tools adequate for the analysis of a small acoustical space. 

In a small acoustical space, the room behavior is dominated by room modes below the Schroeder critical frequency (which for simplicity sake we will state is) in the region of ~300 Hz, and above the Schroeder critical frequency behavior is defined by specular reflections that are resolvable into discrete pathways characterized by both direction and gain. (Specular energy is UNLIKE a reverberant soundfield and various Sabine based statistical formulas are invalid in these spaces. Calculations such as those for RTxx and mean free path are inappropriate as they do not meet the requirements assumed by the calculations. A reverberant field is defined as a statistically well-mixed soundfield. What that means is that the sound field is so statistically randomized that the signal's arrival is equally probable from _all directions_ _simultaneously_. Thus it makes no sense to try to resolve such a soundfield into directional characteristics.

Instead we use tools such as the Envelop Time Curve (ETC) capable of resolving the specular energy arrival into characteristics such as direction and gain and subsequently use such information determine the specific placement of treatment material only in finite areas in order to effectively control a specific problematic energy return without rendering the space too dead. And these tools also allow us to measure the quality of such treatment in spatial and temporal respects - in other words, to see if any reflection from the boundary is focused or diffused.

Thus in a small acoustical space, one requires tools adequate for the job. And the Envelope Time Curve provides that precise functionality enabling resolving direct and indirect discrete energy pathways and their points of incidence with boundaries.

Neither the Omnimic package nor the XTZ package provides the necessary time domain tools. So for ~$300 you have nice RTA and waterfall capabilities, in addition to a few tools that are of little use in a small acoustical space. OK, and to be fair, you do get a pretty nifty box...

Put your money into a package that exceeds the capabilities of both of those pricier packages with truly useful measurements! And considering that RoomEQWizard is free, its hard to beat a free tool whose capabilities significantly exceed those of the two more expensive packages. 

In fact, if you simply want to pay money for a package that includes extensive time domain tools, consider ARTA. It actually provides a few additional advanced and useful tools if you outgrow REW, which can be had for literally 1/2 the price of the niftily packaged, but underwhelmingly equipped Omnimic and XTZ packages. After all, if you are going to pay money, you deserve to get increased functionality and not simply less utility in a nifty box.

Bottomline:
Both Omnimic and XTZ are fine for analyzing room modes. 
But both Omnimic nor XTZ are blind with regards to specular energy behavior above the modal frequencies. Thus they are NOT adequate for analyzing the behavior of a small acoustical space and using this information to effectively treat the room with an appropriate application of absorption, reflection(redirection) or diffusion.

Room EQ Wizard provides tools and the necessary functionality to measure and analyze both the modal response as well as the specular reflections - at a price hat is hard to beat!


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## test4echo101 (Jul 27, 2011)

Good post Sac, once again!
I agree, REW is free and does much more while leaving you the extra cash to invest in quality mics and cables/Sound Cards and maybe even some DIY room treatments!

Test,


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## SAC (Dec 3, 2009)

OK, I will attempt a bit of sardonic humor in the hopes of trying to allay the fears of a few who may be a bit scared of trying REW! (Don't worry, its ALL meant with a grin! ...albeit a slightly sardonic one!!!)

What advantage pray tell is there in spending near $300 for a canned package that does not do all of the measurements necessary simply because one cannot take the time to configure an input and an output cable plus a simple loopback cable?

You still have to do the internal configuration of the IO in software!!!!

And $300 is a reasonable price for eliminating 1 of the 3 necessary cables??? I realize you don't need the loopback calibration cable for a tool that cannot even do time domain based ETC responses, but I hardly see how that is an advantage!

...Or for not much more, hire a professional who will show up with professional tools and do ALL the measurements for you!

To cite an analogy that apparently some will just love: I know where you can buy pants_ really _cheap too. They won't fit you and they cost ALLOT, but hey, the process of buying them is _really_ simple! :rofl:

And if you persist, I can tell you where they have stuff that you have absolutely no use for, but as they are on sale , how can you resist buying several!?!?

If one is looking for the kind of simplicity suggested in exchange for a critical limitation in measurement capabilities, I might suggest getting rid of your computer altogether! Heaven forbid one decide to connect a printer, or a scanner! :unbelievable::dontknow:

Or, tell you what, if this is SO daunting, PM me and for $300 plus the cost of the interconnects and transportation expenses, I will connect it for you.

You'll pardon me, but buying something 'on sale' (which in this case costs $300 MORE than the alternative and does MUCH less) simply because it is supposedly "easier" to connect (despite STILL having to connect 2 of the 3 cables!!!) where you still end up with a severely restricted measurement capability that FAILS to do any time domain tests necessary to analyze any of the direct or indirect signals that dominate the small acoustical space is not much of a deal! And despite some being confused, an incomplete solution, priced at $300 is no deal at all!

I persist in thinking that the average person CAN do this. And no, I am not selling anything! But I am trying to further empower folks if they are willing to endure an hour or two of minor confusion or of taking the time to read the *Room EQ Wizard (REW) Information Index - Links* including the REW Connection and Cabling Basics......[*PLEASE READ*] that are plainly labeled as "*PLEASE READ*"! Hmmmm...I wonder if that means they want us to read them????? Let me do some further research and get back to you....


And after one spends $300, you still can't make all of the measurements necessary to tune a room or to analyze a speaker. What a deal! I'll take 2!!! :rofl:

Folks, yes a few are initially confused. That's not uncommon when dealing with something new and about which one is unfamiliar. But the average person can easily overcome this. And there is help if you need it. Besides, after you connect everything, you are still going to have to learn what the tools do and for what they are appropriate! So, go with the best of breed product relative to cost. REW trumps the capabilities of either of the pricier Omnimic or XTZ products. And just think of the other worthwhile things on which you could find to spend $300! (...And if you have trouble with _that_, PM me, and I will lend a hand for free!) :laugh:


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## test4echo101 (Jul 27, 2011)

SAC said:


> Folks, yes a few are initially confused.


Yep...:neener: But only for a little while

If I can do IT! Anyone can. 

I think a lot of the problem is that some think that "Any" measurement tool can solve a problem in their HT or Music room. The more expensive the better, right?
NO!
They can't, none of them. 
They can only show you whats wrong and whats needed. No matter what the expense.
As REW does it for free (Or a modest donation :T) then why bother with the other stuff that doesn't do anywhere near as much to pinpoint where it is you need to spend money. 
A BFD, Room treatments, diffusers, reflection points......etc can all be solved by REW. 

Those nice graphics in the other offerings are nice but no more useful than REW has.

Test,


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## Nyal Mellor (Feb 24, 2011)

SAC you make good points. 

XTZ does not include an ETC which as you rightly say is a key measurement in room acoustics. BUT (and it is a critical but) it is a lot easier to get up and running with one of the integrated packages than REW. I agree that REW is more powerful but there is a steeper learning curve. I actually use the v5 of REW as my main go to acoustic measurement tool when I am out at someone's house performing an acoustical diagnosis. It is a great product however it is most definitely not plug and play. ARTA is even less so.

If you are completely new to acoustical measurements and don't want to spend the time figuring out how to use the software and determining which sound card and mic to buy then XTZ or Omnimic is the best solution IMO. Most people's room issues are low frequency related and very difficult to identify and resolve without high resolution time domain measurements (which XTZ includes via a spectogram). It is possible to get away with not having an ETC since visually with the aid of a mirror you can tell where the reflection points are in any room. And nearly all rooms that we use for audio or home theater will need treatment at these mirror points. I agree it is not ideal and I have requested from XTZ on a number of times to include an ETC but there is a very usable workaround.

I actually find XTZ easier to use for dialing in EQ as well since it offers a unique 'stimulus EQ' mode which allows you to create filters in the XTZ software and remeasure with those in the chain thus you can go quicker than if you had to download them to your external EQ box each time as you would have to do with REW.


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## SAC (Dec 3, 2009)

Nyal Mellor said:


> If you are completely new to acoustical measurements and don't want to spend the time figuring out how to use the software and determining which sound card and mic to buy then XTZ or Omnimic is the best solution IMO. Most people's room issues are low frequency related and very difficult to identify and resolve without high resolution time domain measurements (which XTZ includes via a spectogram). It is possible to get away with not having an ETC since visually with the aid of a mirror you can tell where the reflection points are in any room. And nearly all rooms that we use for audio or home theater will need treatment at these mirror points. I agree it is not ideal and I have requested from XTZ on a number of times to include an ETC but there is a very usable workaround.
> 
> I actually find XTZ easier to use for dialing in EQ as well since it offers a unique 'stimulus EQ' mode which allows you to create filters in the XTZ software and remeasure with those in the chain thus you can go quicker than if you had to download them to your external EQ box each time as you would have to do with REW.


(BTW, as a preface, I respect_ everyone's _ability and right to make a choice - and even to be incorrect!!:sarcastic: I just don't want anyone to spend to much and end up limiting your choices and capabilities in areas that are VERY important acoustically!)


If you "don't want to spend the time figuring out how to use the software" SAVE YOUR MONEY! NO program is going to do what is necessary for you to move from setting up the device, measuring, determining what is or is not a problem, and then solving it for you! 

The best solution for this person is to buy Audyssey, push a button, and sit content in the belief that all of the problems have been solved and that all is well with the universe! ...Or spend your money hiring a qualified technician.

And for such a person for whom figuring out how to program the channels in their TV's tuner or how to plug in 1 additional jumper is out of reach, how is one going got determine the need, create and properly employ "filters in the XTZ software"?

None of the platforms eliminated the need to become familiar with the underlying acoustical fundamentals. That is NOT the point of this discussion.


Still , the larger issue comes down to folks supposedly having difficulty connecting 3 interconnects (a mic input cable, a loopback cable, and an output cable connecting the output to a receiver) for a cost of $300 and lacking fundamental capabilities!

The literal difference for which you pay $300: the loopback cable. …Gasp! 
And significant lost REAL functionality!

You still have to connect an input cable, and you still have to connect an output cable to the DUT. And heaven knows how difficult that loopback cable is!

And the difference between the connections for other platforms such as ARTA is NOT substantially different other than some may use USB, Firewire , Ethernet or a parallel interface. Interconnects are TRIVIAL! They all have an input and an output. Big deal. The only additional differences are the user interface and the additional features and tools! Now don’t get me wrong, ARTA’s interface is NOT difficult. It simply offers you myriad additional options. Thus you have still more choices and capabilities. ...options about which it is incumbent upon one to become familiar. 

But in fairness, ARTA also offers one of the best user/tutorial manuals available – one which I would recommend ANYONE dealing with this issue download and read. These principles are directly applicable to any of the platforms. But the platform you are using may not have all the features covered. 

And like it or not, at some point one is going to actually need to familiarize themselves with the tools or they will be useless – regardless of how simplistic is the difference in connecting 2 instead of 3 cables. If you are not, stop reading and go back and reread the first several paragraphs and find another use for you moiney.

And regarding the ETC workaround…the proverbial mirror… I wish that was of a real practical value.

The mirror technique was originally used by Don Davis ~ 40+ years ago to explain the concept of early arriving specular reflections when explaining the concept of the ETC in TEF. But that is where the utility ENDS! For GOOD reason!

Here is why.
The mirror theoretically can be used (in concept – as you must literally FIND them all yourself! MANUALLY) to determine every possible indirect path from speaker to listening position! That’s great, but there are several serious problems with this concept that far outweigh its literal inconvenience!

First, all indirect signals are NOT detrimental! And AFTER you spend much time with the help of another person to locate all of the possible pathways, and then IF you block ALL POSSIBLE indirect signals, you end up with a dead room. Not a better room… a dead room. As you have not surgically addressed only the anomalous real signals, you have treated all possible indirect signals. You have solved little. and Instead you have substituted one problem for another. Congratulations. And it only cost you $300 and the friendship of the former friend who just wasted a day of their life. What a deal! 

And after your having heard it said several times that with a mirror that you are able to identify ALL indirect signal pathways, I LIED.

A mirror will not indicate the existence of, nor identify, ANY diffractive sources. And diffractive sources are particularly destructive early indirect energy signals that typically arise due to speaker design and mounting issues.

Thus, with a mirror you can see potential problem pathways, but you cannot tell if any energy even traverse the pathway (as you have no information about the spatial dispersion of your speakers), nor of the gain or arrival times. And without a bit more information, you will literally create as many problems as you will solve – and still miss a few important problems! All for $300 and the saving of dealing with one simple interconnect taking at least 5 seconds to install properly. (Of course, for about the same price you could order an EASERA Gateway interface made by PreSonus with an internal loopback configuration and avoid dealing with the dreaded loopback cable!)

So, at best the result with a mirror is a severely over damped room that utterly misses identifying destructive diffractive sources of indirect energy. And you still have no idea what the real behavior, problems or solutions to the room are. But hey, you were very busy and as a result it is only natural to believe that the time was well spent. Belief is a powerful tool!

So after all that work, one will wonder why they even bothered! But you can relax and be glad that you spent $300 and didn’t get all the very useful tools that are necessary to analyze and treat a small acoustical space just so that you did not have to tackle the dreaded loopback jumper – as after all, the $300 you spent does not even include that capability!

But hey, you didn’t have to deal with that infinitely complex loopback cable that extends from the output of one channel back into the input of the same channel. Pretty complicated… A bullet dodged!



So, here is why 40 years ago, when they used the mirror to illustrate the concept of a reflection, they did not choose to fore go the advantages of the ETC response (which then cost more than ~$30,000 in gear to accomplish) even though the mirror cost substantially less.

With the ETC, we can not only identify ALL ACTUAL indirect paths, we can determine which indirect energy pathways are actually problems. So as while some have gotten a simplistic notion that indirect energy is ‘evil’, only CERTAIN indirect signals are destructive. ALL REFLECTIONS are NOT evil! And you do NOT want to eliminate all indirect energy! If you are at this point in your understanding, you need to do a bit more research – starting with _Sound System Engineering_ by Davis and Davis (2nd ed) or Davis and Patronis (3rd ed). (And in the process discover where Everest sourced much of his information!) 

Additionally, the ETC will clearly show ALL diffractive energy sources as well. Important sources the mirror CANNOT reveal.

The ETC allows you to determine precisely which energy pathways are real and detrimental. No chasing ghosts or ASSUMED evil energy pathways. Instead you surgically identify the precise pathways of specific isolated indirect energy that causes a problem, as well as the precise locations of boundary incidence and diffractive sources and resolve them by appropriate treatment. You quickly identify and fix the specific PROBLEMS. You do NOT create a detrimental overly damped dead space.

Additionally, I have yet to see a mirror used to define and tailor a later arriving laterally arriving exponentially decaying diffuse soundfield. … In other words, the proper reason that some employ diffusion. The ETC also permits you to identify and treat later arriving reflections such that a diffuse energy field is created, along with allowing you to optimally tailor the character of the diffuse energy field. 

A mirror is useless for that, unless you simply feel the need to fard (look it up). 

(BTW, if some are interested in learning more about this specular behavior and how the tools are used to specifically identify behavior and how to use such information to effectively treat the issues, we can certainly do that.)

So the net difference?:

You are out $300, you lack sufficient tools to properly treat anything above the modal range that extends only to about 200 Hz, as you lack the ability to properly treat the CRITICAL range of specular behavior from ~300 Hz to ~10,000 Hz that literally controls imaging, localization, tonality and intelligibility. 

And what do you gain? You don’t have to deal with a SIMPLE (but apparently very scary and intimidating) loopback connection that literally connects the output of one sound channel to the input of the same channel! 

I would go so far as to state (humorously, folks!) that if the interconnects are an_ insurmountable _problem, that they should not be trusted to be alone with such a device (or for that matter, pointed objects, shoelaces, belts, silverware, rocks, water, or any other objects or materials that might potentially be used in a harmful manner) as they may seriously harm themselves. But they MIGHT be safe if only provided with small quantities of Jello. 

_*But yes, the price you pay for ANY measurement platform is the need to familiarize oneself with the basic concepts and learn HOW to properly apply the tools to identify and address the fundamental problem issues. There is NO getting around that unless you hire someone to do it for you! PERIOD.*_


So here’s an offer.

If someone feels SO intimidated by that loopback jumper, or for that matter, by how to connect any of the 3 cables, (of which the amazingly limited $300 alternative platforms requires only 2 that you must still figure out!!!), and you actually TRY to solve the issue and you are unable to obtain help here on the forum, then PM me. We can interactively chat or speak by voice on YM or Skype and I will personally offer to help you sort out the incredibly complex(sic) cabling and adapter dilemma with which you are faced. 

It’s not difficult. It’s simply a matter of identifying the nature of the jacks at the endpoints, and figuring out the transitions necessary to get you to the proper connection format. In fact, that offer stands regardless of the platform used, as long as it is REW, Fuzmeasure, ARTA, EASERA, TEF, PRAXIS, etc., as they are all fundamentally the same.

And we can also explore and explain additional ways to use the additional capabilities provided by the ETC. Just for the fun of it.

And think, as I will have saved you $300 (just to avoid inserting the two ends of a simple loopback interconnection), I suspect that you will feel SO grateful that you will demand to gleefully give me only $150 as a token of you undying gratitude– a savings of ½ the money you saved! What a deal! . (And lest anyone not recognize the wry sardonic humor, the reference to gratuities is mentioned humorously!)

And after all is said and done, you will have a truly capable and functional measurement platform that has a few additional capabilities of which you are not yet aware. 

…Not simply an overpriced fancy RTA and a mirror that you probably already have (along with the capabilities you lack and about which you still have no clue) – without the need to spend $300!

So, if you are smarter than the difference of a single jumper, REW offers significant greater REAL functional advantages for SUBSTANTIALLY less money. But_ neither_ platform excuses you from the responsibility of familiarizing yourself with the basics of what _*tools*_ properly indicate and there interpretation.


I can’t help but think of the significance of the message expressed in Devo’s _Freedom of Choice_.





Have fun kids...


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## Nyal Mellor (Feb 24, 2011)

I can see I'm never going to convince you of the benefit of one of the simpler tools!

For me it is quite simple. It is a matter of how long it takes you to get up and running and start taking measurements. For a lot of people time is money.

For REW you have to:
- register with HT shack to DL the software (ok not a big deal, I am just being methodical)
- install Java
- install REW
- figure out which of the 100s of soundcards to buy
- figure out which mic to buy
- order mic from company A 
- order soundcard from company B
- figure out which cables you need
- order them from company A, B or maybe even a new company C
- take delivery of all said items
- figure out how to connect them all together (not a big deal)
- grapple with setting the trim levels for the inputs on the soundcard (and this can take a while to find the optimum spot)
- calibrate the SPL using an external SPL meter
- NOW I am ready

For XTZ or Omnimic:
- buy the integrated hardware and software package from company
- install the software
- plug everything in
- NOW I am ready

And $300 vs 0 for REW is not really a fair comparison, most of us do not have mics and soundcards sitting around. $300 vs say $150 or $200 would be fair.

On the subject of the value of ETC. In my belief the vast majority of times the first reflections from the ceiling, floor, walls are the reflections that cause degradation in timbre, imaging, soundstage etc. These can be simply found with a mirror, you do not need an ETC. In some cases and in rooms with complex shapes (e.g. pitched ceilings), speakers in encasements, etc an ETC is useful.

SAC you obviously know your stuff but I am a firm believer in matching the tool to the person and their level of understanding. Yes you can give a graphic function solving calculator to a 10 year old but maybe they are better served with a simple arithmetic calculator.

If people are interested in learning about acoustics I suggest buying Toole's Sound Reproduction book NOT Davis and Patronis or even Everest. Davis and Patronis is not written in an easy to read way and is full of math. Toole manages to explain the key points and I am pretty sure he only includes one piece of math in the whole book. Everest has good content but really it is more a general intro to acoustics, not one laser targeted on small rooms with music reproducing equipment in them.


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## SAC (Dec 3, 2009)

Let's just make it simpler.

Per your prescription, and as a mirror *cannot* distinguish between real and imagined reflections, let alone if they are subsantial:

Why do you need a mirror? Since you are going to deaden any reflective path to the sides and above regardless of whether they are real or detrimental: _simply cover the walls and ceiling of the room room between speaker and listener with absorption. And the back wall as well. _*

And why do you need a $300 waterfall response? A waterfall response provides no actionable information pertinent to the application of velocity based porous corner traps. So why do you even bother with the formality of looking at a frequency response or a waterfall? Its not like you are going to the trouble to design or place pressure based tuned resonant absorbers. Such information matters little to velocity based porous corner absorbers absorbers. So you simply employ as many velocity based porous corner bass traps as you can.

You're literally done.

Welcome to your dead room.

And as no actionable necessary information is provided by with either Omnimic nor XTZ, no measurements whatsoever are required to accomplish what we just described. 
You literally do NOT need these platforms if this is all one is doing. 
But then, if this describes you, you probably can't be bothered to read this anyway!
Save your money! And you don't even have to expend the energy to open your checkbook. 

Yes, buy Toole's book. Learn that averaged frequency response measurements in conjunction with EQ results in what he considers to be an optimal listening environment.

And as this prescription will yield little in terms of any actual understanding of either acoustics or psycho-acoustics, there is no need to learn anything about the foundation for, nor the meaning and interpretation of, measurements. As while Toole frequently alludes to the utility and power of TEF, SMAART, and other time capable platforms, he makes almost no meaningful substantive references to their use. And as a result, you will certainly won't have to worry about being subjected to learning any actionable measurement skills them Toole.

So for those folks for whom hooking an extra cable is too complex (and who therefore apparently got their kid sister to wire their 'rad' home theater complex), and yet who hasn't a clue as to what any of the measurements even mean, let alone how to actively employ or interpret them, and even less interest in expending the effort learning about such issues, I can certainly understand how actual texts and measurement platforms able to determine actual causal behavior, as well as even an 'easy to use' $300 measurement platform that provides little actionable information, would serve little purpose except to make manufacturers and their distributors some money. But then again, I am sure that those folks have long ago stopped reading any of this. 

(And I am still very curious as to just why one must obtain an SPL meter for calibrating relative gain levels?:rubeyes: Save your money folks! Nor has anyone explained why someone so confounded by simple interconnects and setting is using a PC based anything rather than a Mac? )


But if you are serious enough to (heaven forbid!) seek to understand what you are doing, and wish to subsequently be able to produce and interpret actionable data yourself, and to then treat and provide proof of performance verification that your actions were effective - AND if you seek any other acoustic response model in addition to a "dead room", then for THOSE folks, forgo the expensive ~$300 package that does nothing necessary, and download REW which offers a tremendous value for the cost of a mic and IO interface. 

And for the record, _Sound System Engineering_ does indeed present, explain and provide actionable information about both frequency and time based concepts and measurements, it also provides additionable foundational reference information regarding simple foundational _algebraic _mathematical foundations for concepts. But* NO WHERE* (except perhaps in the 3rd ed. Patronis' chapter of DSP processing which is_ by definition_ mathematical!), is the MATH required to completely understand the concepts presented. The difference between Toole and Davis is (aside from the fact that Don is literally the individual who did more to introduce the world to both the proper use of EQ and to time based measurements than any other) , quite simply, if you slowly walk through the Davis TEXTBOOK, after reading, you will, unlike after reading Toole, have sufficient actionable information and understanding to actually DO things. 


And unless you are dealing with the Mac and its Firewire interface, or using either either platform and one of the INDUSTRY WIDE problematic dual USB/Firewire adapters - (whose problems will effect Omnimic and XTZ in exactly the same manner!!!), selecting an omni mic and an I/O mic pre-amp is as simple as it gets. Pick one of each!

So, we have beaten this up about as much as can be done.

Have fun.:bigsmile:


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## Nyal Mellor (Feb 24, 2011)

I just don't agree with the core of what you are saying which is that the only worthwhile acoustics analysis program is one that is of the capability of a REW or ARTA.

If we divide up the frequency spectrum into below 250Hz and above 250Hz what we see in most rooms is that it is the room mode related bass problems that are the major issue. These manifest themselves as peaks and dips in frequency response and ringing in the time domain.

Low frequency analysis tools such as averaged frequency response and spectrogram allow people to test different positions of speakers and listener WITHOUT even needing to install any acoustic treatment. They can get improvements in sound quality by doing that and without needing to understand any of the science behind it. Just look at the graphs and find the best position. If average joe can get an improvement in sound quality without having to read Davis and Patronis then for me it is worthwhile. And furthermore, for most people, it is only one position in the room they care about therefore EQ is a perfectly viable solution to combating room mode resonances.

In this simple model of room acoustics we do not 'treat the whole room between speakers and listener'. It is enough to simply place absorptive panels or preferably combination absorber / diffusor panels such as RPG BAD or Primacoustic Flexifuser at the main points of specular reflection on the ceiling, side walls and the wall behind the listening couch. 

I would never say that this is the ultimate 'acoustically treated room'. Far from it. I agree with you that to get to the next level you really need to start going deep into the acoustic measurements. But for some people all they want is 'level 1'. If there are sound quality benefits to be had from simply finding the best position for loudspeaker and listener, putting up some simple acoustic panels at the main reflection points and dialing in some parametric EQ then that is a worthwhile outcome. And I maintain that a simple package is the right tool for the end user who wants a level 1 result.

When you step up to the next level (let's call it level 2) then it pays to start looking much more indepth at how energy decays in the soundfield. And you are right on with stating the fact that this is very important. I totally agree. And a tool like REW or ARTA is perfect for this next level of user.

On the subject of the Toole book you must have missed about 7 chapters where it covered in great depth all of the psychoacoustic research and how it relates to how we perceive sound...


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## Archaea (Jun 5, 2011)

A few friends and I ended up trying REW. For what it's worth I found the omnimic to be more user friendly, easier to quickly get running, and perfectly worth the money I paid for it. A friend of mine who uses REW rarely pulls out the gear because of the setup tasks involved. By comparison I use my omnimic frequently - and do take it with me when I go to friends houses and so forth to quickly and easily measure their FR. The cd based audio tracks are easy to employee in any system.

To be frank the REW experience isn't free. The software is - the calibrated mic, the SPL meter, and the time taken to learn a more complicated (arguably more capable) software is not free.

By contrast I handed my omnimic to a friend who hasn't ever used this type of equipment before and he had his setup working in minutes taking measurements even without my guidance. After using omnimic the same friend tried REW because he said he was too cheap to buy the omnimic and it took him 2 nights to get REW setup.

Price aside - perhaps the difference can be summed up by the comparison of a digital SLR camera and a nice quality point and shoot.
You are going to have fans on both sides. The SLR camera may have more capabilities -but the point and shoot may get used more and meets most requirements.


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## eyesandears (Apr 25, 2012)

I am new to room analysis also and by no means an authority but I thought I would give you my recent experience with OmniMic V2. I can't comment on XTZ but had 5 days to intensively "trial" the OmniMic V2 (factory mic calibration file) in a dedicated room. I was using it with a Dell Inspiron laptop with Vista/32.

I agree, for very little initial knowledge the system was simple to get working quickly. Basically plug and play. 
I realized quickly that the system was limited in it's capabilities at least for the measurements I had hoped to make. There were a number of simple things like setting graph plot scales and limits that are very cumbersome or not possible at all. I can give some details if anyone is interested let me know.
I also had quite a few software "glitches" causing lock up and requiring restarting the program. Perhaps that was something me or the computer to blame. 

For just one example, I am very interested in the waterfall plots and low frequency response for evaluation of room modes, placing acoustical treatments and subwoofer adjustments. I began to be suspect that the data was not accurate when I could get absolutely no reverb peaks beyond 100 mS at all below 500 Hz no matter how I set up the system or changed the software setting intervals (literally spent hours trying to show demonstrate these). Perhaps there is an easy explanation for this but I don't know. I know I did a good job designing my room but it had no acoustic treatments yet and I'm sure it ain't that good. :unbelievable: I think the OmniMic was doing OK job from 500 Hz ~ 10 KHz. I was able to identify some first reflection peaks. There was also a sharp falloff of FR above 10K that I couldn't explain. Of course I didn't have any other equipment to compare it to side by side so I realize that most of this info is anecdotal. I am in the process of rechecking these all things with REW and a new setup and will of course report back here in the next few weeks.

The OmniMic V2 system is a fabulous idea and has great potential but IMHO the software (3.10) interface still needs a lot of work and that was my biggest complaint. I wondered if most of the issues I had were software related and perhaps could be refined or enhanced with future software releases (if the hardware is up to it). I decided there were enough issues that it would be along time before I would be happy with that system. 
I downloaded ETF and REW and did a lot of reading of the user manuals and so I decided to return the OmniMic and go the route of REW and a few extra connections for the additional capabilities. I guess I was always a "separates" kinda audiophile guy anyway! :R I am just beginning to use REW and can't comment on too many specifics about it but I can already see that the user interface (for me) is a whole lot more friendly and appears much more capable software than OmniMic's. (And with HTS here you certainly can't beat the support!)

:dontknow:Well, that's my two cents....YMMV


Cheers!


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## Doctor X (Apr 3, 2007)

So the real question in my mind is whether 1/6 octave or 1/12 octave resolution at the low end is all that is necessary for measuring frequency response abnormalities. I believe REW measures higher than 1/48 octave, but is it necessary for evaluating a room? I am not talking about applying EQ to the system and I think we can all agree that the more info you see, the better the result will be as the Q of the filter matches the resonance more precisely.

Omnimic and XTZ seem like nice programs, but again, is the limited resolution a hindrance for acoustical analysis (taking EQ out of the equation)?


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## Doctor X (Apr 3, 2007)

Anyone?


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## Kal Rubinson (Aug 3, 2006)

Vaughan100 said:


> Anyone?


As has been said many times, it depends on what you are measuring for. What are you going to do with those measurements?


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## Doctor X (Apr 3, 2007)

Sorry for the delay. Just want to measure frequency response, check before and after adding acoustic treatment, tweaking the system etc. I'm not sure how accurate the mic is on XTZ or Omnimic. I imagine it's better than using a standard Radio Shack meter?


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

Any frequency analysis program worth its salt that comes with its own calibrated mic. If they are doing things correctly, they should be performing specific calibration for every mic they send out, as this post explains. Perhaps XTZ can verify this for you.

Regards, 
Wayne


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