CARA - anyone use it?

If so, did you find it useful and is it worth shelling out £50 for?

 

Rob

I have this and I would say itus useful depening on the space you have to play with.

For a start, it is an appriximation tool, not an exact calcualtor. What I mean by this is that you have to model the room and define the materials for the surfaces and also the furniture. Based on these it works out the absorptive and (I guess therfore reflective) qualities if the surfaces and works out where to best position speakers with respect to the listening position.

However, if you have a small room and limited options in terms of where to place the speakers or listener then what the software recommends may not be feasible as it may mean putting the listener in the middle of the room

 

I doesn't do L-shaped rooms IIRC so I make do with the correction software built in to a Velodyne DD range sub.

 

You can model any shape of room you want Steve. If you are prepared to put in the time (as Kmac points out), then Cara will give you real guidence which can prove invaluable in maximising your system's potential. You can give the program a blank canvass to arrange the system for maximum performance, or limit it to living room friendly layouts. Either way, it can prove enlightening and is a useful tool if you are considering treatments.

The time involved is in accurately modelling your living room and furnishings. The more time spent the more impressive the results. It amazes me that people think twice about spending £50 on it when they seem happy enough to keep dropping larger sums on other solutions.

 

Steve have you just got the shareware version? The difference between this and the full program is not small... the shareware is completely defeatured, and not a lot of use.

 

Thanks chaps, I'll give it a go.

 

It seems I shouldn't rely on memory but look again -thanks folks. I already have some room treatment, but the main drawback currently is some decent bass traps, which are rather expensive to ship here, partly hence the DD15.

I have a question for you users of the full version: could I use the graph shown on the DD display to check whether I have modelled sufficiently well in CARA? I would have thought so.

 

Rob - I can entirely recommend Cara as a tool worth having. I've used it for about 4yrs now and not just at home - have used it to investigate proposals as part of the day job with useful results.

The key to getting the most out of Cara is not to get too retentive about the level of detail you feed in. You can get very quick but effective results at the bass end of the spectrum by just modelling the room boundaries and speakers closely; tuern the reflection iterations down to 3 (not standard '5') and you're away.

After that you'll find that there's a steep point of diminishing returns in adding furniture detail. If its less than 1m in any dimension, you can leave it out without significantly altering the results, because the differences will only show up > 500Hz - where the ambient field becomes entirely dominated by material and finish. Similarly, when trying 'positional optimisation' set the calculation bandwidth as 800Hz - 1khz (rather than 20Khz default), because otherwise Cara will try to force flattest-to-20Khz in the model - which is 1) slow and 2) plainly ridiculous when you consider the inevitable divergence between modelled finishes/speakers/assumptions and the Real Thing.

The only downsides of Cara revolve around the lack of an integrated environment (you have a very basic cad modeller which produces a file you have to open separately in the acoustic modeller, which can make design iterations a bit tedious) - but you can add /define any finish you like based on its absorption spectrum, model pretty much any speaker and room. For £50 it is brilliant.

PS. odd shapes no problem at all. If you can't work out what you need, simply add blocks floor-ceiling in in your wall material to subtract volume from a bounding rectangle...

HTH. I've been meaning to write a how-to for ages - a job for chrimbo break perhaps.

 

Some great tips there, thanks! If anyone happens to know these specifics, it would save me re-checking the download. Can it model the following objects:

• cement-rendered wall (chimney-breast)
• drywall (plasterboard cover over timber frame)
• wainscoting part-way up drywall
• pine plank ceiling
• laminate flooring
• large sheets of eggbox-type foam (currently used at first reflection points)
• windows of arbitrary dimensions
• filled bookshelves of arbitrary dimensions

In addition to normal furnishings like rugs, sofas, curtains, etc., which I take for granted. Maybe I should include extensive racks of amplifiers, sources, etc

 

cement-rendered wall (chimney-breast)

Yes - you just create and indent in the inside wall of the room

drywall (plasterboard cover over timber frame)

Yes -you can select this material from the materials section afetr you have defined the wall

wainscoting part-way up drywall

I've no idea what wainscoting is

pine plank ceiling

As before you can define the material thec eiling is made of


laminate flooring

Yes, selectable from a list

large sheets of eggbox-type foam (currently used at first reflection points)

Not sure about this one, will need to check

windows of arbitrary dimensions

Yes doable

filled bookshelves of arbitrary dimensions

Bookshelf of arbitary dimension - yes. Not sure how you would denote it is full though. Need to check

 

Yes, you can do all of those though you may need to define your own materials. That sounds daunting, but actually it's quite straightforward with the materials editor. Search for approriate absorption coefficients of materials on the web and use them to define a new/modified version of an existing material.

You can apply finishes separately to backgrounds, or just build such things as two separate stacked 'blocks' (eg your wainscoting example).

(edit - eg for a full bookshelf - drag a new block to the appropiate size and shape/height above floor. Click on it and define the top, front and sides as 'full bookshelf' material. Easy!)

 

Thanks, that's progress! The eggbox stuff is only really effective for 1st reflections, so I could leave it out for bass-modelling purposes. Wainscoting is stuff like this to about chest height on all walls, in distressed pine

​

 

You could add this (wainscoting) as a material covering part of the wall.

As felix has pointed out it is quite a flexible programme and if you spend the time you can do pretty much anything.
There are a few things that are slightly tricky e.g. not sure how you would do a flat roof with a raised glass section in the middle

It does require the investment of some time though but as people have pointed out it can be well worth the effort.

Since you are creating a virtual replica of your room, the calucations are theorical and the quality of the output will of course depend on the quality/accuracy of the inputs. Hence I find felix's tips very useful as it does mean you can "shortcut" certain things withput affecting the quality of the output.

The other thing I would say is I would have though some measuring equipment to measure the freq response in the room would also be useful as it would be empircal as oppsoed to Cara's theoretical. If anyone can recommend some cheap measuring equipment and software I would be grateful e.g. something like ETF Accoustic or the ARC system.

 

I am considering buying this program -My current system that used to be a joy to me sounds appalling in my modified Garage.

Approx how many hours effort would you think it would be to learn the program, model a basic setup and get some results
20 hrs
100hrs
or More

I used to be a draftsman - And have used 3d cad as a full time job for many years.



tahnks
Andy

 

Less than 20 hrs. Leaning the program is not hard and there is a good online tutorial. I would say you could get good results in less than 8 hours.

With your past experience of CAD I'd say even less for you.

 

Well..its anecdotal...but

When I first got my H2s (3+yrs ago) I spent a weeks tugging them around the room in small amounts until I got the in-room bass-end balance (of what they do) about right to my ears. Then I modelled them in Cara. For the limited parameters I chose (straight ahead/no toe, symmetric w.r.t side walls, below 1Khz) one of the optimal positions came within +/-20mm of where each actually lives. I was pleasantly surprised by the coincidence.


edit for clarity - I did measure a bass sweep to see how the curves compared but the mic I had at the time was very duff and I didn't believe the results (too smooth). I must re-run the experiment.
These days I'd do the model first..!

 

Thanks Kmax - I have Just ordered CARA 2.2 - 75 euros
Andy

 

Martin, Mike, Kenan and all, thanks for the info.

I'll also be ordering it, though I'm a little concerned that I'll end up with the speakers dangling from the ceiling and me listening while standing on my head

 

Rob when I see you this weekend I could do a quick measurement of the room since I will bring my soundcard anyway. Then when you get Cara up and running you can compare the results.

I'm not too sure what Cara does thats worth the money though? I mean.. in a normal room you are limited to a certian placement area for both speakers and listening positon right? So you can calculate the modal behaviour in a free mode calc and work out best positioning. For the specular frequencies, you know already to treat first refletions. If you want to work out the RT60 curve you can do that on a bit of paper pretty simply (probably faster than learning CAD if you have never used it before).

What does Cara give you that isn't mentioned above? Is it just convenience?

 

It offers loads more.

For example - you can choose what your walls are made with, covered with, where the windows are, curtains, carpets, rugs, tv, sofa, chairs, bookcases, dressers etc - and all of this information is used in the calculation of optimal speaker and listener position.

That's without going into the more indepth features and functions it has.

I'm suprised you haven't got a copy Tenson - you can even use CARA to help determine the ideal type and placement of room treatments within the model, and plot the room both before and afterwards.