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Room Measurement After Consulting Gearslutz
Old 5th May 2011
  #1
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BeatlesForever's Avatar
 
🎧 10 years
Room Measurement After Consulting Gearslutz

Dear guys, I'm new here.
Sorry to trouble you with this thread, but REALLY this time I need to know a precise response in regards to these room measurements I made, because till now I've always studied and improved them searching similar cases around the forum, to not disturb you...
...but now I'm in the situation I find very difficult to improve them anymore, so I think it's time to request a proper response to the proper people, and I have to admit the proper people is in this forum lol.
So, before to start, THANK YOU in advance to Ethan, Glenn, John, Weasel and everyone of you who taught me this fantastic discipline room acoustic is, and everyone of you who is going to give an help here...

OK,
my room is about 14'(L) x 11'(W) x 7.5(H)...according to what I learnt from this forum, I made a complex of 22 bass traps, without wood support, so pillows-like, dimensions are 2' x 4' x 6" deep of rockwool with density 60 Kg/m^3, well-tightened with fabric that you can breath inside, and placed them around the room:

Front Wall:

The panel at the lower corners are 2' x 2' x 8", the one straight is 2' x 6' x 6", the one at the ceiling is 2' x 4' x 4"

Rear Wall:

The panel at the upper right (left in truth) corner, over the door, is 2' x 2' x 8" , the one at the door is removable of course and it's 2' x 6' x 6" , all the others are 2' x 4' x 6"

Left Wall:


Right Wall:


These instead are my graphs ( as you see, I don't have a subwoofer )













I want to know if I can start to fine-tune my room with ARC or whatever equalizer, or if there's ABSOLUTELY the need to continue making bass traps....guys, REALLY, I don't know where to put 'em anymore lol !!

I'd be very glad to receive a comment from you gurus of the acoustic, because my competences cannot go further than they are, by now.

Again, THANK YOU in advance.
Old 5th May 2011
  #2
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Glenn Kuras's Avatar
 
🎧 15 years
Looking pretty good to me. You could always make more traps, which will improve things but the question is "How are the mixes translating to you?". If good then your done.
Old 5th May 2011 | Show parent
  #3
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BeatlesForever's Avatar
 
🎧 10 years
Thanks Glenn, I've just added some pics of the room, but they are too big size and I think I'm going to change them lol...

apart that, I want to thank you soo much for the amazing amount of information I got from your site and from suggestion you gave around here...really AMAZING what you can do with acoustic treatment, I can't stop to be happy my friend !!

and about the way they translate, before to test that, I just wanted to follow a RULE, to try to believe in Theory, and realize measurements that would be, "on the chart", "scientifically", more proper to the standards you and all the Masters around here purpose.
Old 5th May 2011 | Show parent
  #4
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PaulRain's Avatar
 
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🎧 10 years
I think it looks very good....I don't think you need to improve much more...there will be always room for improvement but then it becomes obsessive ....now I think it is time to start to mix something.
It seems the two windows on the side corners helps a lot on the bass....it probably go through...
If I really must search of the ear on the egg (I don't think this is correct in English but just translate it in Italian heh ) there are two problems you can see on the Spectral Delay at circa 40Hz and 75Hz.....if I'm not wrong they are modes because you can see them only on the SD and on the Waterfall.....I don't think you need to worry too much about the 38.....but the 75 is not easy to treat........ I'm still in the process of making a right tuned trap to solve a problem around there...porous absorbers will need to be much thicker than the one you have now.....
Looks like 75 is the height mode....
hunecke.de | Room Eigenmodes Calculator
If you spare few more Panels you could try to put a thick one on the corner between the front wall and the floor where that mode should be strong.
anyway be very happy because the result is very good, I wish I could have that result :(
Where are you in Italy?
The only thing that scares me a little is the fact you did the bass trap with no structure at all.....maybe rockwool at 60 Kg/m^3 is not stiff enough to stay straight after 1 year....I don't know...
Old 5th May 2011 | Show parent
  #5
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Jens Eklund's Avatar
 
🎧 10 years
In terms of frequency response only, the result is good but the decay time is extremely short in the region above 100 Hz and a bit too long below. This is however not surprising considering the treatment. You could experiment with covering the traps (besides the ones for early reflections naturally) with slats or thin board to regain some life in the upper region and if you want to try and tame the remaining decay in the sub 100 Hz area, you could try and add some pressure based absorbers. An ETC (approx. 100 ms and 30-40 dB range) is also needed to evaluate the current state.
Old 5th May 2011 | Show parent
  #6
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BeatlesForever's Avatar
 
🎧 10 years
Thanks Paul & Jens for the suggestions, and in fact, apart that I'm tired to build pillows and fix them on the wall lol, the reason why i would stop making them is that, for the purpose to flatten at the very best the low frequencies, I'm completely killing the room...
just to say, I took the measurements with closed windows, aware of the fact that they could reveal useful to gate the low out of my b***s, thus giving me a conscious desired obstacle.
Paul, in regards to the suggestion to put the pillow in the front corner floor/ wall, already tried that...the null at about 600 Hz went down to 40 dB...lemme search that graph...
Old 5th May 2011 | Show parent
  #7
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PaulRain's Avatar
 
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🎧 10 years
don't thank me I'm just a stupid that can't keep his mouth shut......
Old 5th May 2011 | Show parent
  #8
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BeatlesForever's Avatar
 
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cannot find that graph Paul, I've probably erased it, but I remember there was a lil improvement between 200 and 300 Hz...
replying to Jens yes, it's true and noticing it, was quite suffice to bring my case to the Gearslutz's Trial...and about covering the bass traps (not at the reflection points), which material and how thick?
Old 5th May 2011 | Show parent
  #10
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🎧 10 years
Congrat! Great response.
You may want to add some diffusers in the future.
Old 5th May 2011 | Show parent
  #11
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Jens Eklund's Avatar
 
🎧 10 years
Adding diffusers to a dead room will not bring back anything unless reducing absorption (in the higher range).
Old 6th May 2011 | Show parent
  #12
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BeatlesForever's Avatar
 
🎧 10 years
thanks again Jens for the links....before to check them and report what I think in regards, replying to Paul about the integrity of the panels, I think I'll take periodic measurements to see if everything is still ok, and build new panels in place of the weakened ones.
and yes Paul, I'm italian, from Venice, the land of Lovers (lol??)
actually also the land of Garbage out of the doors of the houses, hehe...
Jens, sorry, but the ETC function is present only in the "Room Eq Wizard" v.4 or also in the v.5 ?? I'm not able to find it there, so I think I'll use the previous version..don't worry to reply to this thanks.
About diffusors, correct me if I'm wrong, but I've heard lots of stories in regards to dimension of the room, and also to distance from the listening position...that is not worthy to use diffusors unless the room is big, or better, that your listening position is at least about 8 feet far from the rear wall...then I know that a bookcase full of book is not really a diffuser (imaging it with books in disordered position, as scattering the sound), but it's more considered as absorber...not to say that I tried to add it in the read wall of the room (and also on the front wall), but I didn't see real improvements...anyway, thinking of such tuned traps with holes inside the bookcases, distanced according to the frequency you want to "catch", I'm still tempted to re-arrange my bookcase in order to accomplish this..,but I'm afraid it's very difficult to make it work...
Old 6th May 2011 | Show parent
  #13
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Jens Eklund's Avatar
 
🎧 10 years
The ETC is one of the most basic functions so I assume it has been in REW since the beginning.

Before you start thinking about diffusers you need to recover the energy in your room, either by removing the current panels or covering them with panel/perforated panel to restrict the absorption to where it’s needed; in the bass region. If you decide to go down this path, you can start to experiment with diffusers:

https://www.gearslutz.com/board/bass-...-diffuser.html
https://www.gearslutz.com/board/6521707-post2.html
Old 6th May 2011 | Show parent
  #14
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🎧 10 years
anca Montebeuna xe tera de amanti....
to access ETC in REW go to the Impluse tab....then on the bottom select Envelope (ETC)
Old 6th May 2011 | Show parent
  #15
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BeatlesForever's Avatar
 
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Ok Jens, the concept of the diffuser is perfectly clear now...in other words if I don't free the proper correct energy (of the HF) from the room, there's going to be nothing to diffuse, so I have to proceed to rectify my traps in the way you suggested, before to think to that...

hehe Paul, c'abbiamo l'Esse Music Store lì !!! (translate: "We have the Esse Music Store in Montebelluna !!)

Thanks for the tip Paul, wasn't able to notice it cuz on the v.4 it has its own tab, while in v.5 is in the impulse tab.

Here are the graphs:









Again , here guys my skill in understanding deeply such stuffs is ridiculous, so please if some of you can help a poor old man (35 years old !!) to understand what hell is happening here, and your implacable responses of course, I would be extremely grateful...for instance, why between 100 ms and 200 ms the wave is not "tight" as in the other position of the graphs?
I asked my granny and he looked at me as saying : << You don't know that, my son ??? I'm disappointed of you!>>
Old 6th May 2011 | Show parent
  #16
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by BeatlesForever ➡️
Ok Jens, the concept of the diffuser is perfectly clear now...in other words if I don't free the proper correct energy (of the HF) from the room, there's going to be nothing to diffuse,
Correct.


Regarding ETC:

Quote:
Originally Posted by Jens Eklund ➡️
An ETC (approx. 100 ms and 30-40 dB range ) …
Please adjust the scales of your graph or post the impulse file and I’ll fix it for you.
Old 6th May 2011 | Show parent
  #17
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🎧 10 years
Good timing Jens - I was then thinking about this myself....

What are the best scale limits to set for IR/ETC graphs please? I'll be doing some myself soon and was meaning to ask....
Old 6th May 2011 | Show parent
  #18
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mmmm....100 ms seems a lot to me.... over 30ms I have nothing under 30/40dB...
Old 6th May 2011 | Show parent
  #19
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BeatlesForever's Avatar
 
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Sorry Jens, got some issues with this kind of graphs...you mean 100 ms as +/- 50ms or from about 0 ms to 100 ms?
and 30-40 dB range , starting from where?
If you can just tell me the parameters to set (Left/ Right // Top/Bottom), I'm going to correct it right now...unfortunately I'm not able to understand the concept behind this graphs...

can this be ok?

Old 6th May 2011 | Show parent
  #20
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by BeatlesForever ➡️
Sorry Jens, got some issues with this kind of graphs...you mean 100 ms as +/- 50ms or from about 0 ms to 100 ms?
and 30-40 dB range , starting from where?
If you can just tell me the parameters to set (Left/ Right // Top/Bottom), I'm going to correct it right now...unfortunately I'm not able to understand the concept behind this graphs...

can this be ok?

That’s ok.

What we are interested in is observing the early reflections, when they arrive and at what relative level. In a control room, we strive to minimize reflections arriving too soon (approx. 15-20 ms) after the direct signal and after a time period called the ISD-gap, we usually want a diffuse field (lots of dense reflections). Unfortunately, a bit like the opposite of what the above ETC shows. In small rooms it might be problematic to achieve a good termination of the ISD-gap but at least one should try to minimize the level of reflections within approx 15 ms. You should try and figure out what causes the reflections arriving at about 2-3 ms in your room and absorb/redirect them.
Old 6th May 2011 | Show parent
  #21
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by PaulRain ➡️
mmmm....100 ms seems a lot to me.... over 30ms I have nothing under 30/40dB...
I guess you mean that you don’t have anything over 30/40dB after 30ms.

In this room you’re probably right, but in a good room you are not only looking at the ISD-gap, you also want to see that the diffuse field after the ISD-gap is sufficiently dense and uniform without apparent single, stronger reflections.
Old 6th May 2011 | Show parent
  #22
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by Max Dread ➡️
Good timing Jens - I was then thinking about this myself....

What are the best scale limits to set for IR/ETC graphs please? I'll be doing some myself soon and was meaning to ask....
Depends on the data. Usually we are interested in a time range of about 0 (direct) to 50-100 ms depending on if there’s still some energy to display. In rare occasions, there’s energy before the direct sound () caused by structural vibrations causing surfaces to radiate sound closer to the listener than the loudspeaker and if so, the time before the "direct sound" (from the speaker) is also of interest. Below approx. -40 dB there’s usually not much of interest in the ETC but an exception is for example an ambechoic room where the diffuse field starts at approx -30 dB down.
Old 6th May 2011 | Show parent
  #23
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ahhh, now I see it...and according to what you say, then I also should treat that peak happening at about less than 10 ms, touching the -25 dB line, being this included too in the time-range of the 20 ms...and at this point also the lil peak in the middle of the one you reported and the one I find out (at about 5/6 ms )
And after treating these 3 points above mentioned, after the gap (so after 20 ms), is it recommended that the decay of the wave we see here to be longer in time, for instance that instead of reaching 45 ms at -50 dB, it reaches, let's say 60 or more ms ??
Thanks for the constant interest_
Old 6th May 2011 | Show parent
  #24
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Jens Eklund's Avatar
 
🎧 10 years
BeatlesForever

Why not try to use some of your existing panels, relocate them to absorb the early reflections.
Old 6th May 2011 | Show parent
  #25
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BeatlesForever's Avatar
 
🎧 10 years
Jens because I tried a lot of positions, but the one you see in the room pics assure me with closed windows to have the low frequencies between the range of +/- 5 dB (not smoothed)
Old 6th May 2011 | Show parent
  #26
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Glenn Kuras's Avatar
 
🎧 15 years
If you want to try to get some of the high energy back into the room then try covering the fronts with FRK or thin cardboard.
Old 6th May 2011 | Show parent
  #27
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by BeatlesForever ➡️
ahhh, now I see it...and according to what you say, then I also should treat that peak happening at about less than 10 ms, touching the -25 dB line, being this included too in the time-range of the 20 ms...and at this point also the lil peak in the middle of the one you reported and the one I find out (at about 5/6 ms )
And after treating these 3 points above mentioned, after the gap (so after 20 ms), is it recommended that the decay of the wave we see here to be longer in time, for instance that instead of reaching 45 ms at -50 dB, it reaches, let's say 60 or more ms ??
Thanks for the constant interest_
Normally you don’t bother with reflections lower than about -20/25 dB unless they are alone and isolated and this is somewhat the case here but start with the earliest, stronger ones.

In a good LEDE room, the termination of the ISD-gap should be around -12 dB down but lower is ok as long as there’s a marked difference in level compared to the ISD-gap. Again, this is not easy to do in small rooms so focus on the early reflections and just try to reach as long and even (in frequency) decay as possible. Around 0,2 - 0,3 seconds is good but small rooms are difficult to keep alive unless going nuts with pressure based absorbers and using velocity based solely on early reflection points.
Old 6th May 2011 | Show parent
  #28
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🎧 10 years
ok, thanks Glenn for the thin cardboard suggestion, this could be good and easy-made to take back HF energy, so after this new treatment to the traps, I could expect an incrementation of the global decay of the ETC graph, so giving me a room ambience result nearer to what Jens told (0,2s or lil more)...but first of all, I have to deal with those early reflections happening in the ISD-gap domain, and must try to dampen at least the major peak (at 3 ms) down to homologate with the whole curve of the decay...windows? the lil low deck? the door? or probably the heater in conjunction with the door at the corner??
I'm going to check those things before, try to correct those peaks doing new measurements, and once done, thin cardboard on the traps to retrieve energy..
Thanks guys REALLY for all those suggestions.
Old 6th May 2011 | Show parent
  #29
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PaulRain's Avatar
 
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🎧 10 years
Quote:
Originally Posted by Jens Eklund ➡️
In a good LEDE room, the termination of the ISD-gap should be around -12 dB down but lower is ok as long as there’s a marked difference in level compared to the ISD-gap. Again, this is not easy to do in small rooms so focus on the early reflections and just try to reach as long and even (in frequency) decay as possible. Around 0,2 - 0,3 seconds is good but small rooms are difficult to keep alive unless going nuts with pressure based absorbers and using velocity based solely on early reflection points.[/FONT][/COLOR]
Just to make few references.....
so 0.2/0.3 second until the decay gets to the level of the graph before the 0 peak? In BeatlesForever case is more or less around 230ms.
I remember you (or maybe someone else) saying somewhere here in the forum, about not to care much of the really very early reflections...I don't recall how much early.....I'm I wrong?
Old 6th May 2011 | Show parent
  #30
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by PaulRain ➡️
Just to make few references.....
so 0.2/0.3 second until the decay gets to the level of the graph before the 0 peak? In BeatlesForever case is more or less around 230ms.
I remember you (or maybe someone else) saying somewhere here in the forum, about not to care much of the really very early reflections...I don't recall how much early.....I'm I wrong?
Not sure what you mean but when we talk about decay time we are referring to the time it takes for the level to drop 60 dB (from -5 to -65). This figure can be extracted from different ranges, T20, T30, T45 etc. and interpolated and this is why they differ if uneven decay. Worth mentioning is that it is not scientifically correct to talk about reverberation time in small spaces like control rooms.

The very early reflections are usually a result of either diffraction from the speaker cabinet, and this one reason for flush mounting, and/or a desk. None of these are easily dealt with in a home studio environment.

The level of energy before the direct sound is, unless the scenario described above with vibration causing a new sound source closer to the listener than the speaker, the noise floor of the room/equipment.
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