CARA - Room Acoustic Software

We're very much not into doing sales-pitch type posts, but after reading through several threads in this forum, we realized that questions regarding software for room acoustics were frequent enough that if we tried to answer every thread, we'd *really* feel obnoxious!

So... the lesser of two evils

CARA is a comprehensive room acoustic modelling package designed and developed by German physicist: Dr. Ulrich Thomanek. Dr. Thomanek worked with ELAC GmbH for many years and used computer models to bring their loudspeakers to be the number two in Germany.

He started ELAC Technische Software as a spinoff dedicated to his computer programs associated with loudspeaker modelling and room acoustics. CARA 2.0 is the product.

Rather than get into too many details here, I'll send you to where they have lots of information regarding CARA and a walkthrough. The site is in both English and German.

Early last year, Rhintek became the US representative for ETS and CARA. We have a strong background in software development, but are relatively new to the high-end audio industry. Our website is:

Thanks for your time, I'll probably be lurking around here on occasion as it looks like this forum is a good place for me to gain more understanding.

Kristin VanVranken,
Rhintek Incorporated
Personally, I appreciate your post. I am about to completely rebuild my living / listening room and would like to be certain the acoustics are as good as possible. I am currently having dialogue with Owens Corning's Acoustical division, they have acoustic panels that are designed for wide band treatment, that hide under a special decorative cloth. I am told that "flipping" one panels (two treatment sides) makes a significant difference in the room acoustics.

I will go have a look at the site you are suggesting. However, my first concern is how to measure the room, before and after treatment. I doubt I could not afford a microphone precision enough to be as accurate as the software. Is there a way around this?

By the way, I wonder how many remember that Miracord was the engineering behind Preputium ( PE ), Dual and Elac Miracord turntables produced in Germany in the late 60's and on. Often the stickers covering the mechanisms on the bottom could be pealed to reveal the logo. Thanks for reminding me of Dr. Thomanek and his fine company.
Albert, I took a detailed look at the site and I am quite excited by the capabilities of the CARA software. This is by far the most sophisticated modelling software I've seen. I have been quite interested in sophisticated RTA measurement vs "sounds" particularly as per the use of room treatments and DSP. ( I own Sigtech, Dunlavy V's and dCS gear). It is prohibitively expensive to buy all the gear needed for the real time analysis that CARA models. However, you should be able to hire a professional consulting audio engineer for about $100 per hour to do all the sophisticated measurements for you to check the veracity of the model. I've used this approach to check on the accuracy of the Sigtech gear, software modelling speaker of placement and the results of my experiments with room treatments. It takes about four hours to run measurements allowing for tweaking during the session.
I'm going to buy the CARA package but my schedule won't really allow me to commit the time that something this complex really requires for the next few months.
Good luck on your remodel.
Thanks Pls1, If this thread has lost it's momentum by the time you are finished, please start a new one and give us a report. I would consider this of great value.
Will do
I just bought a copy of CARA and have started digging into it. After a bit more exposure I plan to post a review on it.
Rather than post a novel at the end, let's take the serial approach. Here's the first installment of the review as promised.

First a little background for reference. While far from being an engineer, working in the software industry for a couple of decades have provided me with a great deal of experience using computers and applications. I build my own systems (they're faster AND cheaper than off the shelf units), can program a bit and know user interfaces pretty well (sold development tools too long not to), but have never worked extensively with a CAD or drawing package. I'm also reasonably new to high-end audio, so please pardon any mangling the lingo.

My current room is rectangular and setup is pretty straight forward. BUT the room where I'm moving this month is complex to say the least. Describing it is a chore. Picture an L-shaped room. One leg is 19.5'x12' with a 13.5'-10.5' cathedral ceiling peaked in the center. A hallway off one end goes to the rest of the house and there is a small room (with double doors) across from the hallway. This end of the room also has a 7' ceiling that is 3' wide and is where the front door is located. The other part of the L is 10'x9' with an 8' ceiling and the kitchen is off to one side of it. The two sections of the L are also divided by a low hanging 10"x10" beam. There's a plethora of materials with lots of windows, tile, carpet and other surfaces of varying reflective/absorbtive properties. Nice place, but acoustically a tough room.

This room is what prompted the purchase of CARA. By no means am I deluded into thinking anything replaces experience, but getting a solid starting point is the desired result. For a rectangular room the various formulae provide that; this room demanded more.

But enough background. The CARA package appeared two days after it was ordered. Very prompt shipment and delivery by Rhinetek which is worth a lot of Brownie points. I loaded the software and dove right in.

There are two main parts to CARA. A CAD package to design the layout of the room and a calculation module. There is also a graphics playback module that is accessed via the calc module.

Installation was simple. Put the disk in and let it install. Suggestion to new users: The help system comes up upon launching the software. Take the time to go through the information being offered as it will save time in the long run. For those like me, it is possible to bull your way through, but you'll eventually read the same material, so do it up front and save yourself the hassle. For instance, the ceiling height is set with the initial room definition and cannot be changed without starting over!

First up was modeling my current room which is rectangular. Very simple and straight forward. Unfortunately, nothing new was discovered. Apparently all the formulae from Cardas, Hales, etc. are good starting points and all CARA did was reinforce what I already knew (the room is too small).

Once the basic room layout is modeled wall materials are defined and windows, doors, curtains, furniture, etc. are added. CARA supplies a library of materials and furniture, plus an editor allows altering them or adding new ones. Finally, speakers are selected and a listener position is defined. A library of speakers is included and an editor is provided for adding others or editing the existing ones. The speaker library contians mostly European manufacturers products. That's no surprise since the package was written in Germany.

While CARA can be used to analyze an existing set up it is also a good tool for selecting a starting point in a new room. When searching for an optimum position both speakers and listener are defined as regions, not finite positions. For instance, in one model the speakers are at one end of the room, the listener at the other. As laid out the listener region covers half the room and each speaker a quarter. When run CARA will find the best position for each within the defined region. This, of course, takes a little time. Depending on the number of variables used (and there are too many to go into here; suffice to say that everything including relative humidity is included) each model takes from 10-30 minuts to run. The greater the number of iterations the better the information, but the longer the run time. Weights can be applied to each of several measures depending on what the user wants to accomplish. At the end a chart is provided that includes SPL at varying frequencies along with direct sound and first wave front, as well as a static charts outlining the results of the location diagram with similar information plotted. The system also extrapolates a set of "quality numbers" for comparisons. Extrapolated as deviations from the target functions defined before running the simulation, included are frequency response, location, clearness/clarity, weighter average value and total optimizitation reference number, all expressed as percentages.

Once an optimal position is determined the sound fields can be computed and played back in an animated mode. This takes considerably longer (30-45 minutes), but the result is an eye opener. Virtual test tones are played in the room and the results are displayed onscreen. This feature alone has already taught me a lot about how waves set up in a room. Watching the waves rise and fall graphically reinforces why a particualar position may be better than one just a foot way.

So, after running a number of scenarios I am close to deciding how to initially setup the room. Next up will be to tweak and measure the results and compare them to CARA's. So far, my recommendation is that CARA is worth the $50 price of admission. Let's see if that opinion holds.

OK, that's the happy side. Here are the frustrations so far: a) CARA is metric only! I had to convert all measures before plugging them in. Minor, but it's a hassle. That cost them in the useability assessment. b) Whereas CARACALC can be started multiple times so that multiple models can be computed simultaneously, it would often times crash when the computation was halted. If one module crashed the others would continue to run, but only until they were halted. THEN they would crash. Again, kind of frustrating, but no show stopper. The good news is 2-3 models will run on my machine at the same time with no problems. YMMV as my system has 384 megs of fast RAM, though it didn't seem to be a memory issue.

Next installment: Was the setup info valid?
Was the set up info CARA provided valid?

Having modeled the room with reasonable care, including speaker position/toe-in, furniture, wall hangings, etc. CARA was set to determine the optimum speaker position. What was quickly learned was that in this room it was better to put some constraints on the software. Given too much lattitude the outcome was a "speakers-in-the-face" result. But this is a very complex room with angles, peaked ceiling, etc. In a simple, rectangular room the results were predictable as they were very close to those provided by the Cardas method. Being somewhat limited by the usuable space, CARA was run with those limitations considered. The end results are surprisingly good. After considerable tweaking the speakers are now within 1-2 inches from the positions defined by CARA for distance from front, side wall and each other. The model used, BTW, was to optimize for three listening positions side-by-side on a sofa. In this scenario CARA takes an average of the three. The variances may well come from my having made adjustments from the center position only.

Next, the calculation module, CARA Calc, was run to computing the sound fields of the room. The results were quite interesting. When CARA calculates sound fields it is as though virtual test tones ranging from below up to above the audible range (5Hz to 20.48kHz) were being generated within the modeled space. The effects are display in a 3-D animation using color variances to indicate changes in sound pressure in dbs. The animation can be started, stopped, and stepped backwards and forwards via a VCR-style control. This makes it quite easy to visually locate probable problem areas in a room.

Two observations derived from actually listening to my system and room were supported by CARA's sound field calculations. The first, and worst, is a bad bass problem in the left front corner. In CARA this shows up as a large red region. In reality simply putting one's head in the corner quantifies that the problem exists. The other was more telling of CARA's usefulness. A friend noted there was a shifting image in the mid-bass on the right side. The sound field visualization in CARA shows a small peak at exactly that position.

One downside to CARA Calc is the time necessary to run a complex model. My room has 150 visible polygons. This is high and it may be possible with further experience to bring this number down. The maximum reflection for this calculation was set to 5. According to the online documention "The maximum reflection order describes the highest number of reflections from any surface of a sound ray passing from a loudspeaker to the listening place. In a rectangular room, a reflection order of 1 yields 6 possibilities, one reflection for each wall surface. The order 2 yields 18 possibilities. For a realistic result of the sound field calculations a reflection order of at least 10 should be used. Increasing the maximum reflection order increases the calculation time, order 20 may take hours to complete."

Even though my model was run at a low maximum reflection order, the calculations took three days to complete. Thus, this is probably a step best taken when the user is satisfied with the model's completeness unless the number of visible polygons is low. Unfortunately, this limitation (actually a function of the machine as much as the product; mine is an AMD 850 with 384 megs of RAM) also renders CARA less useable for "what if" scenarios such as determining optimum placement of acoustic treatments.

All in all I have found CARA to be an interesting, useful tool. A side benefit is that now, as my system and room set up evolves, I will have a visual record of the changes for comparison.

Two things I would change in CARA are: 1) Add support for inches and feet 2) Make all fields, such as speaker placement, editable so the values can be edited instead of static displays. Dragging icons around works, but for accuracy nothing beats numeric input.

Next up: Long range impressions.
Fpeel, Thanks for the great review. I'm going to call for CARA RIGHT NOW!

Couldn't tell from your post: Were you able to make a model of your funky room?

My system is located along the long wall toward one side of a very large room. Is this something it seem CARA will be able to help? I know you're not tech support, but I'd appreciate a users impression.

Though not previously experienced with any CAD products, I was able to model everything in this room including a couple of odd corners and the two exposed beams on the ceiling. Not the most complete CAD package according to a buddy who would know, but definitely workable with some diligence.
BR>BTW, my system is set up along the 19.5' wall. A neat feature is the ability to do a 3-D walk through of the modeled space. Mine looks alarmingly like my room. Except my speakers aren't blue. ;-0 Which reminds me of a bugaboo in CARA. Be careful when defining the regions in which speakers or listeners can be moved during optimizations. If these overlay a 3-D object (sofa, rack, TV, etc.) the speaker or listener will be raised above that object. To avoid this I always do a 3-D walk through before running any calculations.

Ran the calculations once without realizing this had happened and got great reference numbers. Turns out the speakers and listener were suspended about six feet in the air! Haven't figured out how to make stuff float in the air quite yet...
That last sentence should have reas, "Haven't figured out how to make stuff float in the air in real life yet.... "
Dad gummit, "...should had READ,..." One of these days I'll learn how to prufreed.
Woudl I be correct if I assume that CARA can also be used to make hypothetical changes to a listening room such as a pair of tube traps or that small sink and wet bar that my wife seems to be thirsting for?

The short answer is yes.

To expand on the subject, once a new object is placed in a model using the CAD tool there are three calculation options available, position optimization, sound field calculation and special calculation.

Position optimization would indicate if a new speaker/listener postition would be appropriate (or how well it would work). Sound field calculation could be used to visually compare set ups. These two sets of calculations can take awhile to complete; sometimes on the order of days. Special calculation runs through the basic calculations once and seems to be most useful for quick feedback. It's the "what if" feature in my opinion.

Each of these has a number of user defineable variables available (listed under the general categories of SPL Target Functions, Variational Ranges, Weightings and Parameters) that I won't go into detail on at this time. Hope that's helpful.
Yes that is helpful.

That sounds like fun. Most of the little toys we get for our systems are stuff that we plug in and then listen to. That is certainly fun but this, OH THIS lends itself to ENDLESS tinkering in pursuit of a high science as well as good sound. And to think only $50

Now all I need is a Cray supercomputer...maybe I could get deep blue to come on over....
While i haven't seen my September Stereophile yet, i guess that they talk about this program, maybe even review it. Based on Frank's ( Frap ) comments and what i read on their website, i've ordered their "package deal". This consists of the computer program and a CD of test tones, etc... Since most of my rooms are quite irregular, along with that of my brother's house and my Dad's, this should come in REAL handy once it shows. I know that Doug ( aka Sedond ) also ordered it, so we'll probably start seeing more comments about it here and on other audio forums pretty soon. For the record, they are currently back ordered on these items but do expect them in sometime very soon. Sean
Very interesting posts!!
Please keep us updated with your experiences....mine is an irregular room with open access to other areas. Does the program provide for this as well.
So far I´ve made calculations with easily available tools on the net and good'ol SPL + Excel chart plotting.
Definitely looking for tools like this
I've been using CARA for a couple of months. It works wonderfully and I highly recommend it. I've been able to confirm the results with my Tact RCS.

The only major flaw is that it would take an unrealistically long time (several years) to do an accurate set of calculations for all but an empty rectangular room.

One interesting thing that I've found is that in a model system, I do not end up with anything close to the Cardas placement of speakers even in a room with Cardas' recommended dimensions. This isn't too concerning because my room is no where near perfect.

I noticed an immediate improvement in soundstage and tonal balance when I put my speakers in the weird assymetric places that CARA recommended.
Metaphysics: Several YEARS ??? Thanks for the warning and the laugh : ) I guess i know what to expect now...

I've seen others state that this program is SLOW and can really chew up computing power. My fastest puter is a lowly 350, so it might take more than a FEW years for me....

As to Luis' question, I "think" that CARA can accomodate openings. At least i hope it can. That is one of the main reasons that i'm picking up a copy. The room that my HT system is in has an archway adjoining into what we call the computer room. I have a seperate 2 channel system in the computer room. As if that weren't tough enough to deal with, the computer room has an archway opposite the other opening that leads into the kitchen !!! There is a direct line of site opening from the front of the house all the way through three rooms to the back wall of the kitchen. Talk about "trouble" when it comes to freak acoustics !!! Then again, this might end up helping me due to staggered standing wave patterns ????

Since some of you folks have already been using this system, can you work with speakers that offer 360* of radiation ??? Sean
Sean, Yes; several YEARS for a fully accurate calculation, but it works well overnight (on a 1GHz machine) to give a good approximation.

Yes CARA can accomodate openinings, but it will add to the calculation time unless you treat it as a simple open door, i.e. no reflection or loadin. It can also handle 360 degree speakers.
Have any of you guys ever been to a true high performance discotheque?

Have you been inside the control rooms?

Do you know how they are equalized?

Do you know why they sound so good, even though they are using Technics 1200s with DJ cartridges?

The answers will enlighten them.
Does CARA have a speaker model for Vandersteen 2Ce Signatures?
After some basic modeling of your room and speakers I think it becomes easier to have in room real time measurements made. I used the much simpler RPG software to get some general ideas about speaker placement, room treatments and listening positions. Then I improved on these with in room measurements. You can hire an audio engineer for about $100 per hour anywhere near most large cities to do the measurements for you.
Thanks "Meta" for clarifying the issues. Sounds like this program is REALLY worth the money and FAR more versatile than any of the others. Since your 1 gig puter can do it overnight, my older 200 can probably swing it within 2 - 3 days or so : )

Psychicanimal, what is a GOOD sounding "disco" ??? If you think that nightclubs have "good" sounding audio systems, i can understand why you went with the 1200. I'm not trying to be rude, but there is a BIG difference between what a sound reinforcement type PA system and a home audio system do well. Sean

How about a club with all Bryston amps and five way amplification, for a start?

Do you know of any in Chicago Metro?

I haven't seen anything that outperforms my home turf, yet...
1. CARA can accommodate open doorways.
2. Unlike most other programs, it can handle non-rectangular rooms.
3. Computation can be long but there are strategies for that.
4. Real measurments are, of course, better but that means moving real objects for the measurements.
5. I did not see any models for Vandersteen but you should check the CARA websites or ask Vandersteen for the info to make your own model.
Psychic, you are comparing apples to zucchinis. The atmosphere, acoustics, goals, etc... of a nightclub sound system are VERY different from that of a true "high fidelity" reproduction system. Regardless of the brands used in either, the nightclub will have very poor resolution, lack detail, offer very irregular frequency response ( on purpose ), will not offer any type of soundstage or imaging, etc... whereas a good home system will do all of these with ease. After all, what kind of midrange can you get out of a 12" or 15" JBL woofer in a front loaded horn ??? Sean
Sean, I've been wanting to start a thread on high performance discotheques. There is much to be learned. I learned a lot from one audio salesman who worked for the same company I did back in 1982-83. He was an opera and classical freak, but started his own business setting up incredible high performance discos. His home system consisted of a Linn Sondek w/Monster Alpha, Klyne SK-5A pre, Conrad Johnson tube power amp, Proac super tablettes and a Janis 12" sub. His objective, as he taught me, was to replicate as much as possible that sound in a club. It worked.

To start with, discos are run mono. A good EQ-ing job will be done by EAR with a 31 band EQ, when the club is packed (this guy told me he took acid before doing such a job!) much for overemphasizing frequencies. The curves are very gentle, by the way. The EQ-ing is for flatness, man. The sound will be five way, so you will have tweeters, midranges, mid-bass (~250 Hz, for PUNCH), woofers and subwoofers. Yes, you can get great sound. Liberating the drivers an the amps by doing this on a five way system has an unbelievable effect on sound quality. So much for the schools that teach 'start at the source' or 'start with the speakers'. Has to be experienced for anyone to become a convert.

Are there any ways of actually defining a custom loudspeaker with its actual SPL diagram?
"Are there any ways of actually defining a custom loudspeaker with its actual SPL diagram?"

Inadequate. You need the spatial information as well. You need to know all the dimensions of the speaker (you can measure them), the frequency bands for each driver, the crossover slopes, and the bass loading.
Thanks for the input.

My question was more along the lines of whether or not the SPL diagrams were editable, given that you actually have the measured frequency response of each driver.
Psychic, i have worked doing pro sound reinforcement for a living, sold pro sound gear for a living, recorded and produced a few local bands, etc... As such, i would consider myself QUITE familiar with all of the aspects that you have mentioned.

If you would take SPL measurements in the clubs that you think sound "great", you would find that the first thing that they did was to "neutralize" peaks and dips in the room due to its' specific acoustics. This WILL vary with how crowded the club is. That's why minor adjustments are needed on a night by night basis. Once the room is somewhat "flattened out", they will administer further equilization to achieve the tonal balance that they are seeking to achieve for that specific group of entertainers.

Most "metal" or "hard rock" will get tweeked at about 80 - 120 hz with a slight emphasis between 200 - 400 hz. This adds "weight" and "body". Depending on the venue and sound that the band was looking for, sinking the 1 Khz slider down will make the vocals sound more distant and "heavier". One might also elevate the 2.5 Khz to 4 Khz range, as this would let the guitars cut through with more "bite". If cymbals were weak, you would play with the 8 - 12 Khz range. Moving this will add or subtract "splash" accordingly.

On the other hand, acts with a lot of vocals would not want the same equilization as it would come across as being muddy at the minimum and possibly even sibilant or "spitty" sounding due to the upper mid boost.

Even with all of the EQ'ing that takes place, it is next to impossible to get even sound coverage in most halls. The speaker arrays are normally not well thought out, their dispersion characteristics are not optimized, the acoustics of the room are rather eratic and the density of the crowd varies drastically. As such, trying to go for a "flat response" would be a waste of time and typically result in HORRIBLE sounding performances as it would only be "flat" in a very few spots. Most folks would rather have it be "coloured" but sound pleasant.

All of that is why home audio and pro sound are so different. We know the venue that we'll be listening in, we know the acoustics, we know where the listener will be seated, we know the appr listening levels, etc... Since most of the variables have been removed, we can then attack the problems more completely and precisely with less side effects than if one was working on a much "grander" scale.

The bottom line is that Pro Sound and home audio have very little in common other than they both use electronics to amplify and reproduce the signal. Sean
Albertlu wrote: "My question was more along the lines of whether or not the SPL diagrams were editable, given that
you actually have the measured frequency response of each driver."

CARA does not measure anything; it models based on input data.
Sean, Emilio was unique...his clubs were just amazing. His EQ curves did not look at all like you describe (maybe cause he claimed doing it on acid). EQ was set and covered with plexiglass. Too bad he died at an early age of an inmune defficiency...

Take the message, release the pigeon...
I have a pair of Dunlavy SC-VIs, some very high-end equipment and and a large but complex room.
I got this great accoustic simulation/optimization program CARA 2.0, but even though this program comes with a bunch of speaker models, it has no Dunlavy SC-VI model.

I have created a simple SC-VI model but it is VERY far from the frequency response of the Dunlavy SC-VI. I sent an e-mail to Dunlavy a couple of months ago asking them to make a correct model, but Dunlavy never responded.

Can somebody get Dunlavy to make this simulation model? It should not take much time and would be great given that these speakers are very sensitive to positioning and this great program does speaker position optimization IF you have a good model of the speaker.

Alternatively, does somebody have a CARA 2.0 model for the Dunlavy SC-VI that is close to the correct frenquency response? Please e-mail to


Would I give Cara all the dimensions and positions, and then have it tell me what I get?
Or, would I give Cara all the dimensions and peices of furniture, etc, and then have it tell me where to put things?

I could give Cara a pile of scenarios for what I would try, but I would rather start by rearranging my room to suit what Cara says is best.
Then, to be able to relocate one piece at a time and see what Cara says about that, since, I don't doubt it would give me something unlivable.
Otherwise, it sounds like quite a long haul, where I have to keep inputting arrangements and wait for the best results.
"Would I give Cara all the dimensions and positions, and then have it tell me what I get? Or, would I give Cara all the dimensions and peices of furniture, etc, and then have it tell me where to put things?"

The former. OTOH, you can restrict the pieces, limiting it to speakers and room dimensions/materials and get an optimum placement. Then you can add each piece of furniture, testing for best positioning.

In the long run, an intermediate strategy is preferred where only the essential furniture is included. Then you can study the 3D graphs to see what places are good/bad for the other stuff.

Easy? No but it works better than actually moving furniture and trying to remember if it sounds better or worse.
2 questions and some comments:

1) Does CARA include speaker info for the Dynaduio Contour 2.8 tower?

2) Will the soon to be released 2.1 software version (due the middle of 12/01) be a free upgrade to those that purchase version 2.0?

I use a software based (MLS) impulse response system (ETF5 $150) with a calibrated microphone.

This system provides amazing results (impulse response, frequency response, waterfall charts) for analysis and recording of my changes. It also does so in pseudo-real-time i.e. I can make changes and watch them appear as frequency graphs on the screen 4 seconds later.

CARA sounds like the perfect companion for me.
Does CARA works with Electrostatic speakers?
I have Martin Logan Monolith III.
Thanks alex
Has anyone modeled Paradigm reference studio 60, Studio 20,
Studio CC or PS 1000 sub. The sub's driver is internal and is not exposed with only three open ports. I can not figure out how to specify the type and position of the driver since internal is not an option. Also does anyone know where can I find the impedance information required by CARA. I appreciate any help. Regards