# Room simulation



## JohnM

Last year I found myself wanting to study the effect of multiple subwoofers, so I wrote a simulation for rectangular rooms that supports up to 4 subwoofers and a pair of speakers. I've finally got around to tidying it up and including it in the latest REW beta release.









I'm curious to know how useful people find a tool like this. Many of us don't have rectangular rooms of course, and ultimately there is no substitute for measurements, but if this sort of thing is useful and there are additional features that would make it significantly more useful I'll look at adding them. Let me know what you think.

P.S. Here is some help information for the room simulator (also in REW's help): simulator help.


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## fusseli

Very cool! It could be useful in setting up small office systems which are perhaps more commonly rectangular.


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## Chester

An optimization feature where placements with flat responses and minimal resonance dips could be found would be cool! I realize this may be a lot of work. Something like RPG room optimizer... Also, the way things are color coded on this site: http://www.hunecke.de/en/calculators/loudspeakers.html in the applet is pretty cool, it basically shows based on the listening positions, what some decent placements are... the 2-dimensionality of it makes it a little difficult to use, maybe there is a way to show in 3d where good/bad (even/uneven) placements responses would be, based on the listening position.

Is it possible to add non-rectangular rooms via some sort of wave field analysis? I realize that if it were easy, you probably would have already implemented this 

The way you have things setup where the various microphones follow the head is beautiful, excellent design - thank you for making this! This is truly a great feature.

EDIT/addition: also, a way to compare two different sub locations directly, where you could see sub location response a vs b in comparison would be very cool. Does REW save the dimensions, absorption coefficients, etc when it is closed?


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## JohnM

Chester said:


> Does REW save the dimensions, absorption coefficients, etc when it is closed?


Of course it does


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## machuk

I have been using REW some time ago. 

It would be awesome if you put away the restrictions of the measures. 

(excuse my English)


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## cavchameleon

John,

Thanks a LOT for doing this, awesome as always. I'll try it out soon.

Ray


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## 3ll3d00d

This is great, really useful and interesting to play with. 

What would it take to extend this to slightly more irregular rooms? is that feasible or becomes too computationally challenging? 

The reason I ask is because my room is essentially a cuboid but with alcoves/recesses. I find the simulation is really accurate when the MLP is away from those recesses but not particularly accurate when you approach those corners. 

To be specific, I measured 4 sub locations with responses in 3 listening positions, the simulation is consistently accurate for MLP 2 but not for MLP 1 or 3.


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## JohnM

3ll3d00d said:


> What would it take to extend this to slightly more irregular rooms? is that feasible or becomes too computationally challenging?


It would need a completely different approach as closed form solutions for the equations do not exist - the main approaches are finite element, finite differences and boundary element method, but all are computationally intensive.


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## cleansocks

John,

It is a really cool software!Thanks from Chinese fans here.All my friends are suprised on it.So exciting!
Just one thing they want me to ask,How come the frequency response curve will not change if we just change the woofer's direction by Right click the icon of subs,Because it will change at physical truth.
And will you improve the Room simulation by adding this function in new beta REW?
Thank you so much for doing those great jobs!

Your Chinese pal,
Ryan


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## JohnM

Hello Ryan. REW treats all the sources as omnidirectional, so rotating them will not have any effect. I'll look at supporting directional sources but it may not be easy to achieve.


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## Chester

It would be cool if we could program in the frequency response of the speakers/subwoofers (from sweeps)... 

Also/EDIT: If there were a way to define a 'zone' (averaged frequency response across an area, rather than points, I could see that as useful info too. Additionally, in an earlier post, I mentioned an 'optimization functionality', where REW would find the best location for the sub based on the flattest frequency response across the responses at displayed positions... since presumably most of us are EQ'ing the sub, rather than the flattest response, maybe a 'least variation over a given area' response would be better: so rather than having to eq for two positions, there could be a general curve that is pretty close to what every position needs? just a thought


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## CFmartin

This is a great tool, thanks John!

Some thoughts:

Main speaker's -3dB LF point is needed for the calculations, but slope type is not. This is something that I would like to be able to adjust. For example 12dB/oct for closed box, 18dB/oct for vented and 24 and 48dB/oct for active crossovers. Subwoofer filter slope should be also adjustable.


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## stevekale

What if the sub is elevated to the ceiling? (BTW If sub one and two aren't paired at the front, i.e. you made subs two and three be at the front speaker position, it doesn't seem possible to align the positions of the subs with their aligned dimensions.)


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## JohnM

stevekale said:


> What if the sub is elevated to the ceiling?


Not sure I understand the question, the sub height can be set in the Elevation view. 



> If sub one and two aren't paired at the front, i.e. you made subs two and three be at the front speaker position, it doesn't seem possible to align the positions of the subs with their aligned dimensions.


Sub 3 points forward by default, rotate it by right clicking on it or using the 'R' or 'L' keys.


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## cleansocks

Awesome!Thank you so much!


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## Chester

Had another (hopefully) useful idea: it would be awesome if you could select a 'default response location', and then as the head placement moves, it would show the relative differences from the original location (subtract original response). This would make it easier to find locations of minimal bass response variation over an area. Would this kind of thing be difficult to implement?

My subwoofer is currently standing on 12 cinderblocks because of this simulation  47" off the ground, I managed to find a relatively smooth response location somewhere I never would have tried before! Thanks!


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## BlueFlowers

Nice new feature on an already great program.

Unfortunately it is of limited use to myself because of the very atypical room I'm in. 
As is stated in the first post, that isn't something which is easy to simulate off course.
A link to or examples on how to calculate the absorption values of wall and furniture etc could make it easier to use.
Just my 2cts.

Regards!


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## AlexF

Thank you John! This is very useful tool within one program. Is is possible to use it for the square rooms?

And on the "sources" tab there is the *"surface absorption" list*. As I understand correctly it refers to the different materials (wood, concrete, plaster boards, carpets, etc) and their absorption properties. Where can I take this data?


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## FoLLgoTT

The room simulation ist extremely useful! Thanks for that! 

I used ABEC to simulate my double bass array (DBA) before which gave me the same results. Would it be possible to add controls for setting up delay and gain for each subwoofer? This would be a killer application.


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## fokakis1

I can't wait to get home and try this. My room is perfectly rectangular and of the 5:4 proportion, so this should be a useful tool for my setup.


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## fotto

Very nice tool John, thanks. I saw a post in another forum where a user had overlaid the predicted sim response to an actual sub sweep response in REW. I can't figure out how they did that. Assuming there's a way, can you advise how to do it?


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## JohnM

AlexF said:


> And on the "sources" tab there is the *"surface absorption" list*. As I understand correctly it refers to the different materials (wood, concrete, plaster boards, carpets, etc) and their absorption properties. Where can I take this data?


You can find a handy list of typical data here. Absorption varies with frequency, but the simulation uses a single figure for its whole frequency range so you'll need to pick the figure for the range of interest.


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## JohnM

FoLLgoTT said:


> Would it be possible to add controls for setting up delay and gain for each subwoofer? This would be a killer application.


Yes, and I've already done it. Will be in the next release (don't hold your breath, I'm working on a couple of other things also that need to be finished, but shouldn't be too far off).


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## JohnM

fotto said:


> I saw a post in another forum where a user had overlaid the predicted sim response to an actual sub sweep response in REW. I can't figure out how they did that. Assuming there's a way, can you advise how to do it?


Don't know, perhaps in an image editing program. I could add a feature to turn the simulation results into REW measurement files if folk can think of some good uses for that.


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## AlexF

JohnM said:


> You can find a handy list of typical data.


John, thank you for this very important information. I think it would be *very useful to include it into the HELP section *on the program in order it will be always on hand within the program itself.


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## FoLLgoTT

@JohnM
Are you planning to implement the loading of an "absorption over frequency" file per wall to simulate specific absorbers?


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## JohnM

FoLLgoTT said:


> Are you planning to implement the loading of an "absorption over frequency" file per wall to simulate specific absorbers?


Not at the moment, though it would be possible to have frequency-dependent absorptions with the method used.


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## fusseli

I played around with the room simulator in my computer room / office while taking measurements with my UMM-6. Looks like room simulator is doing a pretty good job, it did help me get better overall FR after shifting around my speakers and sub. The green is after tweaking with my soundcards 12-band graphic EQ :T


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## mojave

JohnM said:


> Yes, and I've already done it. Will be in the next release (don't hold your breath, I'm working on a couple of other things also that need to be finished, but shouldn't be too far off).


I'm enjoying playing with the Room Simulation. Any estimate on when the next release will be available that includes delay and gain?


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## JJ_MADI

JohnM said:


> You can find a handy list of typical data here. Absorption varies with frequency, but the simulation uses a single figure for its whole frequency range so you'll need to pick the figure for the range of interest.


John,
thanks for the link. If I am running a simulation and plan to cover my rear wall, for example, 25% of the surface with bass absorbers that has an average absorption of 1.55 from 125-4000hz, would a guy enter .40 in to the surface absorption rear wall parameter to approximate the change in response?
Thanks,
Jay


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## jjeronen

Thanks for a very nice tool, John!

Some suggestions:

- Are there plans to support more than two main (non-subwoofer) speakers in a future release? It would be handy to obtain a ballpark estimate of the frequency response of a 4.1 or 5.1 surround system (some people may want 6.1 and 7.1, too).

- When positioning the listening position or speakers, an option to snap to fractional values such as 1/2, 1/3, 1/4 would be nice. Also, snapping to an x/y/z coordinate shared by one of the other speakers would be useful. Both of these would allow easier placement of speakers on the same line, and the first would help with moving the listening position back to the center line without changing other settings.


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## JohnM

No immediate plans for changes to the room sim, but I'll add those to the request list.


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## giogt600

Hi there
I've just downloaded Rew for my mac but i can't seem to see the room sim tab at the top.
Am i doing something wrong or is there a setting i've missed ? Any help appreciated.

Kind regards
gio


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## 3ll3d00d

giogt600 said:


> Hi there
> I've just downloaded Rew for my mac but i can't seem to see the room sim tab at the top.
> Am i doing something wrong or is there a setting i've missed ? Any help appreciated.
> 
> Kind regards
> gio


Did you download the beta or the 5.00 version? The sim is in the beta only.


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## giogt600

3ll3d00d said:


> Did you download the beta or the 5.00 version? The sim is in the beta only.


Hi there

I've tried both and there was no difference. The only thing i will add is that i'm still running snow leopard on my macbook. Does that make any difference at all ?

Many thanks
Giovanni


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## JohnM

The latest REW beta only supports 10.7.3 onwards (that is the earliest version that Oracle's OS X Java runtime supports, which is required for properly functioning audio interfaces).


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## giogt600

JohnM said:


> The latest REW beta only supports 10.7.3 onwards (that is the earliest version that Oracle's OS X Java runtime supports, which is required for properly functioning audio interfaces).


Thanks for the reply John. I'm also running Windows 7 on my macbook via parallels so I ended up downloading the beta version for that. 
One thing I noticed though was some strange behaviour when running the room simulator unless its me, not being familiar with this programme. If it is me I apologise in advance John. 
I put in my room dimensions, my main listening position and then proceeded to place one sub and later a second. I placed number one sub on the right wall at 1.4 meters from the screen wall. 
All ok so far, but when I go to place sub number two on the left wall at the same distance the diagram is not symmetrical. Sub two shows 1.4 meters to be much further away from the screen wall than sub one on the right at the same distance settings. 
I was just wandering if there was a reason for this or wether I'm doing something wrong. 

Kind regards
Giovanni


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## JohnM

I'm not sure I understand Giovanni, could you post a screenshot showing what you mean?


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## giogt600

JohnM said:


> I'm not sure I understand Giovanni, could you post a screenshot showing what you mean?


I'm not at home at the moment so I'll look into posting something up for you. 

Basically, once I've put my room dimensions in I then look at the overhead plan view. I first place my main seating position at the bottom in the middle of the room. I then place sub one on the right wall at 1.4 meters from the front of the room which is the screen wall. You click on the icon of the sub and it shows the distance you've placed your sub ( i.e. 1.4 meters ). If I then go to place a second sub on the left at the same distance of 1.4 meters from the front wall the icon I would imagine should be in the exact opposite location to sub one. To get the icon of that second sub to read at 1.4 meters from the front wall I need to position it further down so that when your looking at the plan view they are not opposite each other. 

Probably no clearer after that explanation either John......but I can still post something up tomorrow if I've made it as clear as mud....!! Lol. 

Regard 
Giovanni


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## JohnM

Are the orientations of the sub's different? The distances are to the acoustic centre, which is near the front (where the arc is). The sub's can be rotated by right clicking on them.


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## giogt600

JohnM said:


> Are the orientations of the sub's different? The distances are to the acoustic centre, which is near the front (where the arc is). The sub's can be rotated by right clicking on them.


Thanks for your reply John. I don't know wether my computer was having a bit of a strange moment the other night but I started the programme up again last night and all seemed to be displaying correctly now. Oh well....the joys of modern technology I guess.....!!

Thanks go your input anyway. It's a great piece of software in my opinion. 

Regards
Giovanni


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## luegotelodigo

JohnM said:


> You can find a handy list of typical data. Absorption varies with frequency, but the simulation uses a single figure for its whole frequency range so you'll need to pick the figure for the range of interest.


I think it's more realistic and easier if you calculate the average alpha using T60 and the Sabine equation:
*Avgalpha=0,16*V/(SS*T60)*
where:
V: volume (m3)
SS: Sum of the surfaces (m2)
T60: RT averaged as in ISO 3382 (s)

Jose


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## luegotelodigo

By the way, I posted how to use the REW room simulator for dipoles in my blog but I can't include links. If anyone is interested I can send it in a private message.


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## lesmor

Thanks for providing the room simulator as many members find it a useful tool

Is there anywhere that explains the "Time Align Speakers and Subs " feature?
i.e. do you add or subtract the time align ms to those already presented in speaker distances "from mains"?
Would be neat to have the distance required along with the time align ms.

Thanks in advance
Andy


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## JohnM

Time alignment behaves the same as it does in a processor, all sources are delayed to have the same delay as the one that is furthest away.


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## lesmor

JohnM said:


> Time alignment behaves the same as it does in a processor, all sources are delayed to have the same delay as the one that is furthest away.


Hi John
At the risk of sounding dumb but wouldn't that mean in a Home cinema all speakers distances would be set at the same distance as the furthest speaker, even if the surrounds are much closer i.e. a sub in a front right corner being the furthest?


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## JohnM

No, because the distance settings are used by the processor to work out how much it needs to delay the nearer speakers to arrive at the same time as the furthest. After it applies the delay the _effect_ is as if all speakers were at the same distance though, which is what is required.


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## Chester

Could we apply a speaker frequency response measurement (nearfield) of a speaker to the computed room response (same goes for subwoofer) so that overall response can be predicted?


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## JohnM

Can't apply a measurement, but can adjust the LF -3dB point and enclosure type settings for the subs and speakers to reflect their approximate low frequency performance.


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## shkumar4963

Thanks John. Love the simulation. Not for finding out the sub locations that will give the best frequency response but for getting a better understanding of how sub placement changes the response. 

I do have one question though for REW. When it creates EQ, does it take into account regions that are at min phase and the regions that are not at min phase? In other words, does it ignore non-min phase regions before deciding on EQ curves?


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## JohnM

REW's target match will not try to correct notches in the response, which is generally where the non minimum phase behaviour is to be found. Whether a section of response is minimum phase or not doesn't prevent EQ being applied to it, and it might even be possible to correct the magnitude (SPL) response in such a region back to flat, but the phase response will not be corrected so the overall effect of the EQ would not restore the timing of the signal even if the magnitude is flattened.


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## shkumar4963

JohnM said:


> REW's target match will not try to correct notches in the response, which is generally where the non minimum phase behaviour is to be found. Whether a section of response is minimum phase or not doesn't prevent EQ being applied to it, and it might even be possible to correct the magnitude (SPL) response in such a region back to flat, but the phase response will not be corrected so the overall effect of the EQ would not restore the timing of the signal even if the magnitude is flattened.


That is true. But I thought that correcting the amplitude out side the min phase region will result in worse audio quality than before and should be avoided. 

Do you agree? 

Also how does it sound when frequency curve is equalized in non-minimum phase regions (and phase could not be corrected?)


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## JohnM

shkumar4963 said:


> I thought that correcting the amplitude out side the min phase region will result in worse audio quality than before and should be avoided.
> 
> Do you agree?


Not really, no, that's too much of a generalisation. There are two kinds of feature in the response that can correspond to non-minimum phase behaviour. The first is partial cancellation of sounds travelling different paths to the measurement point, which causes sharp dips in the response and also shows up as sharp spikes in the Excess Group Delay plot. There is nothing to be gained by trying to raise those dips with EQ and trying to do so would be detrimental. The second is peaks caused by sounds on different paths combining to cause reinforcement at some frequency, which shows up on the group delay plot as broader bumps. Those can be addressed by EQ to reduce or eliminate the emphasis that would otherwise occur at that frequency which would typically be better than doing nothing, though the benefit may be restricted to a fairly small region near the measurement point.



> Also how does it sound when frequency curve is equalized in non-minimum phase regions (and phase could not be corrected?)


I don't know that there is any meaningful answer to that. How something sounds depends on the whole response and the content being reproduced and is very subjective. Trying to assign a label to the 'sound' of an aspect of one small part of the response is likely to be futile.


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## shkumar4963

Thanks John. I recently have been reading about Dirac Live. They claim that it can look ahead in the music and cancel reflections by sending inverse in time domain. The idea sounds feasible but I have not been able to read any papers or books that can explain how this is actually done and how effective it could be. For now I am assuming that this is different than what REW does which is in frequency domain and at min phase. But I may be wrong and Dirac assertions may only be a marketing line. Could you comment and refer to somewhere where I can read and learn more about the technology.


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## JohnM

That's how FIR filters operate, there's more info in this wikipedia article and particularly in its references and external links: http://en.wikipedia.org/wiki/Digital_room_correction. There is also relevant discussion in this thread.


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## shkumar4963

Thanks John. There was a lot of great information in that thread. arc2 is very similar to Dirac live. REW is very easy to use and gives great EQ curves. Do you know of a free pc based system that does the same for FIR filters. I would try it and then post results.


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## lovingdvd

John and all - Wow the REW Room Simulator is a fantastic tool. With my room set up I need to sit in middle of a 28 foot room, slightly off center. This of course is not good because of the 20Hz 10-20 dB drop it creates due to being in the middle. However I think I have a workable solution with two HSU subs rated for 18 Hz (VTF-3 MK5).

Please view the screenshots I took of some configurations with Room Simulator. Can you please tell me if this looks like it would provide a viable solution?

There are a number of screenshots available here http://s177.photobucket.com/user/lovingdvd/library/Sub Sim . Look at the title shown in for pic for a terse summary of what that configuration consists of.

Note that you can see the speaker/sub placements and MLP in the diagram on the top left of each picture.

- It starts with rew-sim-left-sub with is just one sub in the best possible spot. Not a terrible starting spot I assume.

- Next is rew-sim-two-sub. This is with a second sub placed. Wow this really looks great (I think??) as the peaks around 80hz should be easily equalized out.

- Normally we would be done here I suppose, but look at the next pic titled rew-sim-two-sub-with-fronts. This adds in the L/R fronts. Wow that 40 Hz dip is horrendous! Am I correct to assume that I cannot discount this and that indeed you have to look at the total result with the subs AND the fronts included like this?

- Assuming the answer to the above question is "yes, it matters!" then how about this next one rew-sim-two-sub-with-fronts-crossed-120hz... Its the same as the last one except I cross the fronts at 120hz instead of 80hz. The dip at 40hz is much improved and now "only" -10 dB.

- Next up is rew-sim-two-sub-with-fronts-crossed-120hz-5ms-delay. Here I add a 5ms delay to each sub. Now we just have the peak at 80 to (easily) handle. However look at the massive dip at 110hz. Is that a concern?

- Finally is rew-sim-two-sub-with-fronts-crossed-120hz-5ms-delay-subs-absorb. This is the same as the last one, except assuming the room is treated with material with an absorption factor of 0.30. I do plan to use acoustical panels for all walls and ceiling, and to have a carpeted floor. What type of absorbtion factor do acoustical panels provide? I'm not sure is 0.30 is low or high. But assuming its not hard to get 0.60, have a look at the last one rew-sim-two-sub-with-fronts-crossed-120hz-5ms-delay-subs-absorb-60. With this curve there is a little peak at 80 and that's about it.

Hopefully I am on the right track here and am not just adjusting things that can't really be done just to get a pretty curve.  Please let me know if this may be realistic to achieve. For example I will have a highish-end AVR like Denon 5200W with its advance multi sub eq. I assume it will find the delays or otherwise allow me to manually set such adjustments?

Thanks!


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## JohnM

For much content the contribution of the main speakers does matter. Did you try a more symmetric positioning of the speakers across the width? There is a table of absorption coefficients here.


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## lovingdvd

JohnM said:


> For much content the contribution of the main speakers does matter. Did you try a more symmetric positioning of the speakers across the width? There is a table of absorption coefficients here.


Thanks John. Yes I experimented with several placements. You can see the various results by viewing this "photo album" of screenshots here http://s177.photobucket.com/user/lovingdvd/library/Sub Sim?sort=2&page=1

In general how does an uneven rectangle affect the results? For instance, the front half of my room is 18.5 feet wide, but then there is a 42.5" bump out (about 17 feet from the front right wall) that runs down the rest of the room on that side, which makes the back half of the room 15 feet wide.

To put it another way, imagine a 18.5' x 17' rectangle, followed by a 15' x 11' rectangle that's flush with the first rectangle on the left-hand side. 

I have a lot of confidence in the REW simulator and am happy with the various options it shows that I have as good starting points, but I am unsure of how much of a difference there will be in the real-world due to my room not being a perfect rectangle. 

And, I wasn't sure what would be a better model given that I can only draw a rectangle - to do one at 15' wide or to do one at 18.5' wide. I did one at 16' wide too. Anyway, here is the latest one I did for one sub:










and here's one with two subs:









There are based on 18.5' wide model.

From everything you've seen so far in my simulations, do you think its a safe assumption that I can count on getting a great EQ/calibration for my sub, despite sitting in the center of the room (although technically because the room is wider at the top, I am sitting a few feet off center there, which helps avoid a dip I think).

Thanks!


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## JohnM

The substantial change in width will affect all the modal paths that encounter those surfaces, so don't put too much store in the simulation output. Even if the room is rectangular there is still no substitute for measurement.


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## luegotelodigo

JohnM said:


> The substantial change in width will affect all the modal paths that encounter those surfaces, so don't put too much store in the simulation output. Even if the room is rectangular there is still no substitute for measurement.


I agree but the simulation is a good way to explain what you measured and to predict what will happen placing absorbers. I'm very happy you improved it enabling different wall absorptions but as it's becoming more complex, a project saving option would be of help to recover past simulations.

I'd ask for more features like mode decay estimation or Q, the ability to add absorption in Sabines or by frequency but I think that would be too much.

Thanks for the software, every new version is better.
Jose.


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## lovingdvd

luegotelodigo said:


> I agree but the simulation is a good way to explain what you measured and to predict what will happen placing absorbers. I'm very happy you improved it enabling different wall absorptions but as it's becoming more complex, a project saving option would be of help to recover past simulations.
> 
> I'd ask for more features like mode decay estimation or Q, the ability to add absorption in Sabines or by frequency but I think that would be too much.
> 
> Thanks for the software, every new version is better.
> Jose.


I agree. It would be nice to not only have a way to save but something like a tabbed view that made it easy to switch back and forth easily so you can see how various scenarios or changes compare to one another.

Even better would be a way to handle multiple dimensions beyond just squares and a basic rectangle. For instance some rooms are like a rectangle but wider in part of the room than another.


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## luegotelodigo

lovingdvd said:


> Even better would be a way to handle multiple dimensions beyond just squares and a basic rectangle. For instance some rooms are like a rectangle but wider in part of the room than another.


That would need a full change in the way the simulator works. When one of the walls is not parallel to the axes or you want a more complex shape, like a "L" shape you must use BEM, FEM or different numerical methods so it seems to be easy but the maths involved and the calculations get much more difficult.


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## dgmartin

John, 
First I'd like to thank you personally for making such a great tool as REW available to everyone!
I just noticed that cool (new) feature the last time I opened/updated REW. It looks very easy to use.

A few years ago I made a 2D FEM of my open-floor basement. The method being computationally intensive like you mentioned above, 2D was all my old laptop could manage at that time. Now having access to decent workstation, I have started using 3D FEM to get FR (from Harmonic response analysis) at LP from my multiple subs in my irregularly shaped room. I'm hoping to study the placement of my 3rd and 4th subs this way. 

Eventually, if the method is accurate enough to be useful without having to put too much details about boundary absorption coefficients, furniture etc, I planned to make a form (in excel) available in this forum where the room shape can be described and I can run the analysis in batch at little cost in terms of man-time.

I will certainly start using REW as a basic validation tool for my method. I'll be simulating simple test cases that falls within REW limitations and see how it compares with FEM. Even if I get the FEM working well, I'll still be using REW as a quick tool to perform sensitivity studies. Like every calculation it is good to do 1D/2D to identify what to do next in 3D!

So the answer to your OP question is yes, it will always be useful even for someone having irregular room and access to FEM. Thanks again for sharing that!


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## luegotelodigo

dgmartin said:


> Eventually, if the method is accurate enough to be useful without having to put too much details about boundary absorption coefficients, furniture etc, I planned to make a form (in excel) available in this forum where the room shape can be described and I can run the analysis in batch at little cost in terms of man-time.


That's very good news, I can't wait for that!

I think John provides an example of how good is sharing what you know so I offer myself to create a humble excel file to estimate the surface absorptions. I also wrote how to measure RT using REW and how to use the room simulator with dipole speakers. Both files are in Spanish but I can translate them if you just ask.


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## dgmartin

luegotelodigo said:


> That's very good news, I can't wait for that!
> 
> I think John provides an example of how good is sharing what you know so I offer myself to create a humble excel file to estimate the surface absorptions. I also wrote how to measure RT using REW and how to use the room simulator with dipole speakers. Both files are in Spanish but I can translate them if you just ask.


Thanks for your kind offer. I haven't replied since I wasn't able to dedicate enough time. I will start new thread once I get something useful.


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## pepe44

Hi everyone. 
At first i would like to thank the REW team for such a great tool.:sn:
I have one question, and sorry if its too lame .

What to do when you know that the absorption coefficient is different in materials in different frequencies, what value to you use ? i assume that there is not possible way to calculate the average value ... Lets say i have a material that has 0.02 at 125 Hz and 0.65 at 4KHz ? what value should i use if there is only one box for surface absorption.


Thank you in advanced.


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## JohnM

The room sim only covers the range up to 200 Hz, so use a value that reflects the low frequency behaviour.


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## pepe44

That makes perfect sense, Thank you!


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## luegotelodigo

You can do it in several steps and look the band you simulated, RT and therefore absorption are typically very different from 32 to 200 Hz.


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## lemania

luegotelodigo said:


> By the way, I posted how to use the REW room simulator for dipoles in my blog but I can't include links. If anyone is interested I can send it in a private message.


Hi luegotelodigo, can you tell me how you implemented dipoles in REW room simulator?
Best regards
Michael


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