[bpape]

It can be a reasonable approximation.  However, if you build the treatments and set up the room expecting to have a peak or null at a certain place and then do the measurements and find out that your issues are at completely different places and caused by different combinations of dimensions, then you've spent a lot of time and money potentially for nothing.  Realistically, if you stay with the basics, you'll still have a nice improvement just not as good as it could have been.

Again (hate to go back to reality), the time you do the measurements IMO is before you do any treatments.  You move the seating and speakers to get the best response, best imaging, etc. in your situation.  THEN you look at what's left, identify what's causing it, and deal with it.

Bryan

[tonyptony]

Again (hate to go back to reality), the time you do the measurements IMO is before you do any treatments.  You move the seating and speakers to get the best response, best imaging, etc. in your situation.  THEN you look at what's left, identify what's causing it, and deal with it.

I agree completely with this. My thought was a tool could help in that understanding, and then possibly help in determining which treatments would be most effective for the assessed problems after taking care of placement. OTOH, with something like TrueRTA out there I suppose one could just measure the response characteristic in real time.

[bpape]

Exactly.  Now you're talking about actual measurements instead of prediction.  As Ethan is so fond of saying - empirical evidence trumps theory every time.  And he's exactly right.

Bryan

[brj]

I believe that the technology exists to accurately model the acoustics of an audio system in an arbitrary room of arbitrary construction - it just isn't feasible for even the most insanely expensive room or system.

To do it really right you'd probably need the level of modeling and analysis tools used to design high performance cars, ships, aircraft and spacecraft.  You'd need something like CATIA or ProEngineer to provide exact CAD data complete with detailed material properties, and then you'd want to couple this tool to a structural dynamics/modal analysis package like certain versions of NASTRAN or ANSYS and their derivatives.  Depending on how you option those tools out, your talking multiple hundreds of thousands of dollars in software costs alone, and you still need to identify or repurpose a tool to calculate the sound field to drive the simulation... and then you would need to run the simulation as a function of time.

Thinking of a problem of roughly similar complexity, I might consider the case of jettisoning a fuel tank from an aircraft wing while it makes a turn... the lift on the wing deflects the wing, which alters the load on the structure, which starts to bend and twist in response, which alters the lift, which alters the load... iterate that problem until you get a fixed solution for that single instant in time.  (And when I say "that problem", I'm talking about breaking up the air around the aircraft into 10s of millions of tiny pieces and breaking up the structure of the aircraft into 10s of millions of pieces and calculating the forces in each and every piece at that instant.)  Calculate all of the total forces on the various physical objects.  Take a minuscule step in time and calculate where those objects moved as a result of the forces.  Move the objects and go back to the beginning and repeat... for the hundreds or thousands or 10s of thousands of time steps needed to model a single second of actual time.  (The higher the frequencies you want to consider, the shorter the time steps.)  So now in addition to your software costs, you need a multi-million dollar computer in order to generate the solution in less than a decade.

An even more closely aligned problem might be the acoustic loads on the structure of a rocket caused not just by the high speed motion of the rocket through the air, but the incredibly energetic exhaust of the rocket itself.  Or perhaps modeling the acoustic environment in the landing gear well of an aircraft while the gear is extending, including the reaction of the landing gear and bay doors to the pressure and acoustic fields.  I can imagine scenarios of similar complexity involving sonar or radar simulations as well.

The ability to model such complex physical phenomenon currently exists and is in use every day, but the cost of that ability is also part of the reason that high performance or high efficiency vehicles cost so much.

So... just how badly do you want to accurately model the acoustics of your room?

Of course, in 100 years, the cost of modeling such things will be far, far less than today....  the software will be 1/10 the price and run on some derivative of an iPod that has more compute power than all of today's supercomputers combined.  Just imagine the treated audio room your grandkids or great-grandkids might have!

[Ethan Winer]

I believe that the technology exists to accurately model the acoustics of an audio system in an arbitrary room of arbitrary construction - it just isn't feasible for even the most insanely expensive room or system.

That's exactly what I would have said if you didn't beat me to it. You give NASA $75 Million and I bet they'd be able to crack this. Now, split that cost among maybe 10,000 potential customers and each one will pay only $75,000. Such a deal! 

--Ethan

[Bigfish]

Gentlemen:

I have read all of the previous threads with a lot of interest because I have acoustic problems in my room.  First of all, based on reading Ethan Winers FAQ I believe my system may not be positioned correctly in the room.  Here is a picture showing how I have the TV, speakers and system positioned on a long wall:

http://www.audiocircle.com/gallery/albums/userpics/52472/Askew_System_Pics_072307_006.jpg

The room measures 24 X 14 X 8.  To give you a frame of reference the distance from the center of the TV to the wall on the left side of the tv (as you are facing the tv) is closer than the short wall on the right side of the TV.  I have not measured but I would guess the center of the tv is 10' from the left wall which leaves 14 ft to the right wall.  The center of the TV sits directly across approximately in the center line of a double wide brick fireplace (the hearth is at sitting height).  What I am calling the left wall has two 40" wide windows mounted side by side and the other short wall has a French Style Patio door.  The ceiling is flat wallboard with no insulation between the joists.  The floor is hardwood plank on top of 1 1/2" of plywood with insulation under the plywood and roofing paper between the hardwood and plywood.

The speakers are currently not balanced equal distance between the two short walls.  It will be a lot of work moving the tv (wall mounted) but I can balance the speakers if I relocate them to the short wall on each side of the windows (problem is I will have to stand mount the tv - yuk). 

My issue is that since I received the Timepieces I am experiencing "kid in a car with large subwoofer effect) booming bass whenever low notes are played in the music.  The problem is much more pronounced at higher listening levels and tends to be worse with Rock Music than with Jazz.  Have not tried pipe organ music and I don't think I would like the result.  Room has no room treatments. 

I think if I had known I would run into these problems when I started building this system I would not have taken the plunge.  Now that I have invested in the equipment I find I am not where I wanted to be with sound quality.  The smaller speakers I was previously using (smaller in terms of not being able to produce the low, low bass) did not provide me with the resonating bass but also did not provide the clear detail in the upper and mid frequencies.  Guys, I don't have a lot of money to throw at this right now but I need to make the system sound better.  Please tell me how I should start.

Thank you,

Ken

[WEEZ]

Hi Ken

While placing speakers on the short wall would likely work better; it will cost you nothing to try the speakers a few inches one way or the other from the wall; and with a bit more toe-in. If it doesn't help...move 'em back where they were. Nothing to lose.

WEEZ

[bpape]

Where is your seat in the room?

While I'll agree that in that room, I'd definitely rearrange, my suspicion is that the major issue is the seating too close to the wall behind.  The previous speakers didn't put out enough to have the modal issues be obnoxious.  Now, with speakers that will do the bottom, you're hearing all the problems.

Just for kicks, forgetting about imaging for now, put a chair at about 2/3 of the way from the front wall and relisten and see what it does.

Bryan

[Ethan Winer]

Ken,

Please tell me how I should start.

Any chance you can move things around to have the speakers fire the longer way down the room? You said you read my Acoustics FAQ, but this article on our site may be even more useful:

http://www.realtraps.com/art_room-setup.htm

--Ethan

[Bigfish]

Bryan:

I use a comfortable chair and ottman pushed pretty much against the rear wall next to the fireplace.  As the speakers are standing 2.5 ft from the front wall I had pushed my chair back for space and imaging.  I will try your suggestion to see what happens but I think I am faced with rearranging the room as Ethan is recommending.  The plasma tv makes rearranging a tough chore (removing tv, removing hanger and wall repair).

Thanks for the recommendations!

Ken

[bpape]

Understood.  I agree with the rearrangement as I said previously.  I just want you to try the experiment to you can see how much of the issue is seat placement related.  The room will still need to be treated but I think you'll be shocked at the difference.

IMO, the proper way to set up a room is to place the seating first.  Then, place speakers and sub to provide appropriate imaging and best frequency response and integration.  We can spend all the time and money we want on equipment and treatments but if the seat is in a bad place (like against a wall or in a corner), we'll still be fighting it all the way. 

Starting with a good place makes life much easier and allows treatments to be used more for reflection control and decay time control rather than having to use tons of things to try to deal with frequency related issues any more than we have to.

Bryan

[Bigfish]

Understood.  I agree with the rearrangement as I said previously.  I just want you to try the experiment to you can see how much of the issue is seat placement related.  The room will still need to be treated but I think you'll be shocked at the difference.

IMO, the proper way to set up a room is to place the seating first.  Then, place speakers and sub to provide appropriate imaging and best frequency response and integration.  We can spend all the time and money we want on equipment and treatments but if the seat is in a bad place (like against a wall or in a corner), we'll still be fighting it all the way. 

Starting with a good place makes life much easier and allows treatments to be used more for reflection control and decay time control rather than having to use tons of things to try to deal with frequency related issues any more than we have to.

Bryan

Bryan:

Thank you for the recommendations.  When I get back home from this road trip I will experiment with your recommendations.  While I love the Plasma TV on the wall, I wish now I had not mounted it. 

Ken

[Ethan Winer]

While I love the Plasma TV on the wall, I wish now I had not mounted it.

I'd gladly trade two hours of PITA labor for a lifetime of better sound.

--Ethan

[woodsyi]

While I love the Plasma TV on the wall, I wish now I had not mounted it.

I'd gladly trade two hours of PITA labor for a lifetime of better sound.

--Ethan

Sometimes it's not just the PITA.  It's the dreaded WAF.  If she is against it, you may have to promise a lifetime of indentured servitude just to be allowed to do the PITA work. 

[PLMONROE]

The solution is to ban all non music loving spouses to a small tent in the back yard. 

Paul

[woodsyi]

The solution is to ban all non music loving spouses to a small tent in the back yard. 

Paul

Paul,

You try that and you will be the one in the tent with a hand cranked radio. 

[PLMONROE]

Oh well, a tempting thought but maybe not really a good idea .  I would have posted this earlier except I couldn't get in the back door. Sigh.

Paul

[PLMONROE]

Anyhbody have a good used generator for sale cheap? I need something to power my commputer out here.

Paul

[Bigfish]

Where is your seat in the room?

While I'll agree that in that room, I'd definitely rearrange, my suspicion is that the major issue is the seating too close to the wall behind.  The previous speakers didn't put out enough to have the modal issues be obnoxious.  Now, with speakers that will do the bottom, you're hearing all the problems.

Just for kicks, forgetting about imaging for now, put a chair at about 2/3 of the way from the front wall and relisten and see what it does.

Bryan

Bryan:

I just tried your suggestion and bass boominess is gone.  I now have the job to rearrange the room as Ethan and you have recommended. 

Does anyone know of a plain (no shelf) tv stand that will hold a 50" plasma tv 36" off the floor (the bottom of the tv needs to be 36" off the floor)?


Thanks Again Bryan,

Ken

[bpape]

Glad it worked out.  As I said, the room can still stand some treatment to tighten things up even more and provide even more extended bottom end - but this gets you by and lets you work from a good starting point.

Bryan