Room mode calculators

[ncsubum]

From previous posts, i've gathered a few room mode calculators (2 excel type calculators) including:

http://www.harman.com/wp/index.jsp?articleId=131

and i can't find the link for the other one (dangit)

anyway, both have inputs for room dimensions, but nothing about speaker placement (why not? i've read so much preaching about placement, and i've see the huge differences in placement myself, why don't these calculators include that?)

is there any software that considers speaker placement?

Also, that stuff from the Cardas link is such BS

http://www.enjoythemusic.com/magazine/manufacture/0602/cardas.html

...who can actually do that? a room would have to be very large to make it realistic, b/c not everybody can move speakers almost 7 feet into their room, thats crazy. i'll stop there, cause i don't want to make myself sound like too big an idiot.

[dodger]

Hello:

It's easy to calculate room dimensions for proper sound.

Unfortunately with the number of speakers, type: horn, acoustical, etc. it would be difficult to come up with one (1) or Two (2) points regarding placement.

You could fit the dimensions to suit the type of speaker. Experiment on your own and you will most likely find proper placement.

dodger

[artto]

Yes, you are correct about the Cardas link. I went thru this with Colin on another thread. Apparently George Cardas doesnt fully understand what the Golden Mean or Section is all about or how to properly apply it. By the time you get the speakers to positions recommended, the room can become so large that the room modes often have very little influence anyway.

Try this link to Harmon Kardon where acoustician Floyd Toole discusses some of the issues of speaker placement for more conventional speakers (ie: not Klipschorns).

http://www.harman.com/wp/index.jsp?articleId=120

I dont know how technical you are but you might want to take a look at this one too.

http://www.etfacoustic.com/demoroom.all.html

They make acoustical software & this particular link has to do with speaker placement

[formica]

I'd also recommend reading the Harmon white papers... as several documents discus subwoofer (and speaker) placements within the room. It'll give you a great insight of what to expect if you place them in a null or a peak given to you by the room mode calculator.

CARA software is the one which will optimize speaker and listener position in odd (and standard) shaped rooms. You define the area which the software can use to move the speakers and sitting area around... and it'll recommend a spot for each. It was reviewed in Secrets of Home Theater & High Fidelity in 2002.

ETF actually make a RTA (real time analyser) software but it will not make speaker placement recommendations. You can use it with a calibrated mic to see how your room is performing and test several speaker placements... by moving them around the room and re-testing each. Given the magnitude of the low frequency room effects, even with a RS SPL meter (ie: without a calibrated mic) you can still get a reasonable visualisation of your rooms low frequency response.

Later...

Rob

[artto]

CARA.....thats the one I was trying to remember. Thanks Rob

I guess it's a good thing I just got back from the Doc. This sinus/chest cold is killin me. Splitting headache too. Obviously affecting my memory

[formica]

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On 6/8/2004 4:25:51 PM artto wrote:

Obviously affecting my memory

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that must be it...

[ncsubum]

Thanks a lot for the replys, i'll try those out and get back to you...i just hope i can figure them out.

Chris

[ncsubum]

I mentioned something about the Cardas bit on my first post...after reading all the whitepapers on the harman page, the two don't go together at all.

In the white paper "getting the bass right" they show the effects of placing subs (so here i have to assume the same effect would happen w/full range loudspeakers) at the a null point of any axial mode. If the speaker is placed at the null point, then that mode is not activated (in theory).

So using the mode calculator on the harman site, w/my room dimensions ~8x11x20 ignoring the height modes, cause theres not a whole lot i can do regarding placement of the speakers up and down, i have modes at:

Length:

133hz, first null @ 2.25 feet

100hz, first null @ 2.75 feet

66hz, first null @ 4.25 feet

33hz, only null @ 8.25 feet

Width:

205hz, first null @ 1.50 feet

154hz, first null @ 2.75 feet

103hz, first null @ 4.25 feet

51hz, only null @ 5.50 feet

so according to Cardas i i would place my speakers here:

Length placement @ 11*.447 = 4.917 feet

Width placement @ 11*.276 = 3.036 feet

the placment on neither the length or width dimensions match up w/any of the corresponding nulls for any mode for that dimension

my point w/this rambling is that getting false info pisses me off.

somebody new/fairly new to acoustics (like myself) browsing the internet may find that site and really believe that what he says is true. Boo on him. I guess hes a good salesman tho, cause if he can convince people to buy crazy expensive cables, it probably doesn't take much to fool people into thinking he really knows what hes talking about.

Let me know if i'm way off base, i just think its inapropriate to clame its the "only thing you need to place loudspeakers in a rectangular room" with no real proof or measurements or ANYTHING to validate his guesses.

[artto]

Ncsu... youre not way off base, but you cant just ignore the height modes either. We live in a three dimensional space. If you ran sine wave tests on the speakers/room you will find that not only changing listening position as little as an inch or two significantly changes the amplitude at middle & higher frequencies at that location, but that this also applies to the bearing angle (of your head), and the same also applies to your vertical position in the space as well. The same also applies to the speakers location relative to the room & your listening position.

On the other hand that is also one of the reasons Cardas, and the dolts at Absolute Sound who use this method for speaker placement are so off base. And again I must reiterate that using the Golden Mean, even as a guideline to establishing room proportions to maximize (not minimize) mode distribution assumes certain ideal, and certainly simple, conditions, and this applies only up to certain room size/dimensions where the wavelength of the lowest frequencies are substantially longer than any of the room dimensions, which thereafter, the mode distribution becomes so numerous that it is insignificant in terms of affecting frequency response throughout most, if not all of the listening area.

[Colin]

Your point is that Cardas should recommend loudspeaker placement at the null points? Have you tried your loudspeakers 5 out from the front wall and 3 from the sides? How did they sound?

[ncsubum]

The reason i left the height axis off was that I cannon easily change the height of the speakers, I could build a small stand or something of that nature, but its not as easy to do as just moving the speaker in the x and y directions.

Seating position is a separate beast, b/c you would really want to avoid sitting at any one of those nulls or peaks, but somewhere inbetween. Which is sometimes hard to do on the width axis because usually two channel listening forces you sit right in the center of the width axis to get the best imaging. Seating height and distance from the speakers is easy to adjust inbetween the nulls and peaks.

I know you (artto)keep saying that you want to maximize the room modes, but I still don't understand that. I believe i remember that your room only has one seat that you can move and position in your exact sweet spot...where as my room has a loveseat where i usually watch movies and listen to music, and a bed where i occasionally listen to music. Since I am constantly moving throughout my room, would I not want the most even and constant sound throughout, in which case i would have to reduce the number of modes?

Thanks for the responses again, its nice to have someplace to say what i think i have learned and to be corrected. theres so many different sources out there to read which several seem to contradict each other or maybe i don't quite get it. Should i just get the master handbook of acoustics? would that answer all of my questions?

Chris

[artto]

Colin, Im not sure whether youre referring to me or Chris, I suspect its Chris. Youll notice that Chris room is 11x20. The Cardas Golden Section formula is shown using the short wall for the front wall. Placing the speakers in 3 from the side walls leaves only 5 (O.C.) between the speakers or about 4 or less (depending on the cabinet size) in between the speakers. Even the small Klipsch ProMedia on my desktop are 3 apart! Also note that Cardas doesnt even show a recommended listening position. Obviously he doesnt have a clue that the sound will be influenced, not only by the speaker location but by the listening position as well.

To take this one step further, if we use the room lengthwise with the speakers on the long wall, there will be only 6 between the speakers & the rear wall. Also not a good condition as the listening position will be backed up against the rear wall. This will produce bass which is excessively heavy, even oppressive with some recordings and there will be substantial near term reflections from the rear wall which will interfere with imaging & definition unless the rear wall is heavily damped with sound absorption. The heavy amount of sound absorption will further increase the apparent loudness of the bass.

Please dont take this wrong. Im really glad to see that you & many other audiophiles have finally begun to dip your toes into the deep waters of acoustics. I truly am. Unfortunately, most audiophiles are not technically literate. Most are at the point where a little bit of knowledge is dangerous. And people like George Cardas are of no help, other than helping to add to the confusion. He really has no idea what hes talking about. Its unfortunate that hes a contributor to one of your favorite audio websites (to which I understand you are also a contributor). Maybe you can pass my comments on to him. Believe me, if I ever have the opportunity to be in the same room with him I would have no problem first telling him right to his face what complete idiot he is, and then spending as much time as required, free of charge, to explain why. If has any brains, eventually he will be enlightened.

[artto]

Chris, I think getting the Master Handbook of Acoustics will only get you more confused at this point. Youre right, youre not quite getting it yet. Like most people, youre still thinking of this in two-dimensional terms. But dont get discouraged! I didnt learn this stuff by reading through it once or twice either! Keep in mind Ive been at this particular aspect of the hobby (oh how I hate to use that word, lol) for well over 20 years, in the same room. The learning process & planning started years before that. I probably have a bit of an advantage because of my background in architecture and music. AND I STILL MADE A S***LOAD OF MISTAKES along the way! Some of which are still in the process of being corrected.

I realize why you left the height axis off. But you cant do that! What Im saying is that room modes affect how the speaker sounds, especially in the lower frequencies. And that in a simple, essentially closed room, as most domestic rooms are, you must take all three dimensions into account.

Seating position is not really a separate beast. These things are all interrelated. When the room is properly balanced, you will have a very large useable listening area. The smaller the room is, the more difficult this is to achieve. The useable listening area shrinks & shrinks, until there is literally a very small space where everything sounds right. Its not about trying to position the speakers or listening position in between the nulls and peaks. Its about trying to minimize or eliminate those nulls and peaks in the first place. Thats the only way to achieve the best sound from any system. And the room is quite literally part of that system.

In my room I do not have only one seat that I can move around. For the last 20 years there has been large a six piece section sofa in the room. Plenty of sleeping of size for more than one person. It wasnt until relatively recently that I realized it was absorbing bass in precisely the wrong location actually causing more nulls & peaks instead of breaking them up! The sectional is now gone and being replaced by 3 leather swivel recliners. The backs are low enough in the upright position to not cause nearby reflections to the ears. They can be easily repositioned to adjust the listening position to compensate for the differences in recording techniques/mixes. I dont like being tied down to one particular listening spot. In fact, with all the variations there are in recordings, thinking that there is just one and only one optimum position in a room this size would be folly. I will admit though, that the room is getting tuned so well that the number of people in the room dramatically affects the acoustics. Id say that 3 people sitting & two standing behind them is the maximum that is tolerable. And since this is stereo, there will always be only one truly sweet spot.

I think Ive explained why you want to maximize the distribution of modes somewhere in this Topic Area. Do a search or back track. Also, I probably have my discussion on the subject saved. Ill try & find it & re-post it.

[ncsubum]

Its just hard to find good sources of info online. I would like to find a good source w/lots of info that explains things thouroughly and provides proof that what they are saying is true in practice, and not just on paper. like you said, it is more difficult in smaller spaces, and most sources i've found use rooms w/9+foot ceilings, and more than 20feet wide and long. Maybe i'm just asking too much from my room, afterall it is a bedroom, office, 2ch. listening, and home theater room, all in a 8x11x20 space. I didn't mean to get upset about the cardas thing, but for my room its impossible for me to put my speakers that far into my room and still maintain good imaging (they would be like 2 feet infront of me). I should just trade in my car for a pair of khorns, at least that way i wouldn't have to worry about speaker placement. When i buy a house i'm going to have a giant room just for entertainment.

[artto]

Try these. Some, you may have already encountered.

Arthur Noxon, Floyd Toole, Cyril Harris & Alton Everest are all well known acousticians. They can do the math as well as apply it. And they all have the experience to back it up. Jeff Symanski at Auralex has also been very helpful. None of these people are audiophile wannbe acousticians.

Soundwise.org Justin, a Forum member has a download The Papers available in PDF format of the Klipsch Audio Papers, Dope From Hope newsletters & other assorted goodies that I prepared for Forum members last year. It contains some articles on acoustics as well as the renown Bell Labs Experiments On Auditory Perception

http://www.asc-hifi.com/articles/witd.htm

http://www.asc-hifi.com/articles.htm

http://www.asc-studio-acoustics.com/articles/db1191.htm

http://www.classroom-acoustics.com/audiophile-classroom.htm

http://www.acoustics101.com/

http://www.auralexuniversity.com/

http://www.asc-hifi.com/articles/ht1.htm

http://www.asc-hifi.com/articles/ht2.htm

http://www.asc-hifi.com/articles/ht3.htm

http://www.asc-hifi.com/articles/ht4.htm

http://www.asc-hifi.com/articles/ht5.htm

http://www.harman.com/wp/index.jsp?articleId=default

http://www.kuro5hin.org/story/2002/6/9/15027/40923

BTW, youre correct in that youre probably asking too much from your room. Youll never be able to achieve anything near maximum performance in a room of that size and proportions, especially with it being a multi-use room. Even at a larger scale this does not work well. Assembly halls or stadiums do not necessarily make good auditoriums. And great auditoriums do not necessarily fulfill all musical & performing arts purposes equally. Take the Krannert Center for the Performing Arts at the University of Illinois for example. Even here, there are 3 separate, dedicated auditoriums (4 main venues),each with its own special design & purpose.