Spl graph looks relativly fine but Rt is quite high

Soj

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Hi
New around here :)
Was wondering if anyone could help me interpret my measurements and explain why my rt60 is so high but my graph is relatively fine (except for that 150-400 range which i cant quite figure out the reason to right now).
 

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John Mulcahy

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Your RT60 is below 150 ms everywhere the measure is meaningful (from about 300 Hz up), which is very low. Below 300 Hz the decay figures are driven by modal resonances in the space. Your response shape is pretty unusual though, with a heavy emphasis on the upper bass and low mid.

31120
 

Soj

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Hello John, thanks for replying.
Any thoughts on why that’s happening? A solution?
i added a small drawing of my room.
Thanks.
 

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We don't have any information about the room or speakers. When you measure with two speakers running the HF graph is unreliable. Unless the mic is precisely centred the two tweeters will comb filter at the mic. This can end up looking like a roll off, as in your graph. The lack of low LF suggests small speakers, or that they are far from the Front Wall. As John said your room decay is very short over most of the spectrum. Look at the Waterfall, you can see the lowest mode(s) vividly. These singularities can sometimes be avoided using speaker and listener locations. I have found Dirac Live does a great job on my 35Hz lowest mode.
 

Soj

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Hi Dan Dan I am using amphion one 18 on top of iso acoustics 155 on top of heavy 70 pound stands.
The monitors are powered by the amphion 500 power amp.
I have made the measurements using presonus prm 1 mic connected to my apogee element 24, the mic was on a stand and in the 38% of the room.
My room dimensions are:
3.45m= L
2.66m= w
2.7m= h.
I have self-made traps made from two layers of 80 kg Rockwall 120mx 60cm on reflection points+ceiling and some bass trapping on the rear wall and one large bass trap on the front wall behind the desk.
The desk itself is made out of MDF and it’s quite heavy I’m going to share a link with some photos of the studio and the desk please let me know if there is any other information I can supply thank you.
 
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DanDan

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I don't know how Amphion are employing that passive bass cone, but I would try moving the speakers close to the Front Wall. Almost touching.
I am not sure that the Front Wall trap is doing anything constructive. Bass Trap Absorption is magnified in Corners. Cloud?
 

Soj

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Here are some pics and a sketch of the room:
Btw with this measurement the monitors tweeters are around 40 cm from the wall.
 

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DanDan

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Tx. As I said I don't know how the Amphions will react, but they are not that strong in the LF so I would defo try them as close to the FW as possible. If necessary temporarily lose the isolators or stands.
I mean almost touching. The toe in angle is probably enough to allow rear radiation.
 

Soj

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Tx. As I said I don't know how the Amphions will react, but they are not that strong in the LF so I would defo try them as close to the FW as possible. If necessary temporarily lose the isolators or stands.
I mean almost touching. The toe in angle is probably enough to allow rear radiation.
Will do, Btw although I am sitting at the 38% point of the room but I am not sitting in an equilateral triangle: distance from one Monitor to another is around 1.40m and the distance of both monitors for me are 1.10cm so I am sitting in bilateral triangle.
 

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The 38% thing is a bit of a snowball. It is based on a hard concrete space with flush mounted speakers. I would encourage no preconceptions, try speaker AND listener positions until you get the best LF available to you.
 

Soj

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So i moved the speakesas close to the wall as possible and it gave a pretty nice result, tho rt60 still looks insane.
I still don't understand why...
 

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DanDan

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Good, that looks like a useful increase in LF. I would encourage use of Dirac Live to generate a bit more. Or a Sub, dunno about you but I need a solid 30Hz to Mix or Master. The B&K or Harman Target Curve would greatly help translation from your almost anechoic space.(Similar to mine 150mS)
As John said RT60 is overwhelmed by Modes at lower frequencies. Your 1/3 Oct Topt has a distinct peak, but really 450mS or so is not at all long. The EBU Critical Listening Spec allows 400mS.
Looking at a 1 Octave Topt your room decay appears exemplary, albeit on the dry side.
Your Waterfall viewed with a somewhat stringent 50dB vertical range, shows your modes, but there are a few and really nothing much to worry about. Again Dirac Live would tidy these up nicely for you. It would also pull down your prominent mids. BTW, it is important not to stand near the mic when measuring. B&K advise that this can cause anomalies of up to 6dB around 400Hz.
31208
 
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Soj

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Good, that looks like a useful increase in LF. I would encourage use of Dirac Live to generate a bit more. Or a Sub, dunno about you but I need a solid 30Hz to Mix or Master. The B&K or Harman Target Curve would greatly help translation from your almost anechoic space.(Similar to mine 150mS)
As John said RT60 is overwhelmed by Modes at lower frequencies. Your 1/3 Oct Topt has a distinct peak, but really 450mS or so is not at all long. The EBU Critical Listening Spec allows 400mS.
Looking at a 1 Octave Topt your room decay appears exemplary, albeit on the dry side.
Your Waterfall viewed with a somewhat stringent 50dB vertical range, shows your modes, but there are a few and really nothing much to worry about. Again Dirac Live would tidy these up nicely for you. It would also pull down your prominent mids. BTW, it is important not to stand near the mic when measuring. B&K advise that this can cause anomalies of up to 6dB around 400Hz. View attachment 31208
Hello again, in regards to standing next/behind to the mic while measuring : sure i could put on a timer on rew and leave the room while testing but i thought that my body is in the room while mixing so staying while measuring kinda makes sense because ill generate these freq nevertheless.
Ill test it anyways.
should i un-dry my room?
if so, how?
Would you recommend more bass trapping on the front wall?
Would love to hear your take on when is a room done and a person starts obsessing over acoustics?
I'll
admit that i'm not familiar with Dirac but ill start reading right away, from what i saw its a measurement software much like rew that in conjunction with an external DSP (would love a recommendation for a 2 channel one) that sits between the monitors and sound card and applys correctional eq, am i right?
Thanks.
 
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DanDan

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Just stand back from the mic. 2 Metres should be fine! Small rooms treated to a reasonable professional standard very often end up dry. I have never found dryness to be a problem when Mixing or Mastering.
I find it essential to impose a Target Listening curve, a Tonality, which has been measured in real listeners spaces. The B&K curve works for obvious reasons.
Dirac is a speaker controlling app. It is complete and self contained.
 
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Soj

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Hello Again DanDan,
I did some more testing with these deferences:
*Monitors are as close to the front wall as i could.
*Measured 2 times per file (instead of one).
*I was not present in the room during the test.
*Measured L and R separately.

I would appreciate it if could tell me how do i look ar the L and R measurements, what should i be looking for?
Regarding the correcting Eq: understand that Dirac needs some sort of hardware but afraid it will interfere with the quality of my apogee conversion, any insights on this?
I try'd looking for a way to place an eq on my apogee's master channel but couldn't find anything, maybe with their new alloy coming...
 

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DanDan

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Still looks good to me. Dirac Live works at OS level. Originally I used it with an outboard DAC, but now I use a second pair of outputs on my HD I/O.
You have to persuade your rig to send your Mix Buss to two sets of outputs. Use the 'clean' Master Outputs for working output, bounce to disc or whatever. Insert the Eq on the Monitoring Outputs.
 

Soj

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Still looks good to me. Dirac Live works at OS level. Originally I used it with an outboard DAC, but now I use a second pair of outputs on my HD I/O.
You have to persuade your rig to send your Mix Buss to two sets of outputs. Use the 'clean' Master Outputs for working output, bounce to disc or whatever. Insert the Eq on the Monitoring Outputs.
Btw, I found your thread over at the Gearslutz acoustic forum and I have a question regarding what you wrote about the rt60.
So, from what I understood I should ignore and uncheck all values except the T30 and topt?
I’m asking this because with my measurements the t20 and specially the edt were super High (almost a full Second).
 

DanDan

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RT60 is strictly speaking not defined in small rooms. It requires full bandwidth diffuse field conditions, which simply cannot happen. We use the term anyway but it can cause problems such as you are experiencing.
i.e. Your RT views are picking up on modes.
Topt is JohmPM attempt to do better than the classical RT60. T10, 15, 20, are the slopes at the start of the decay. They may have very different slopes to the majority of the whole 60dB decline. Your Topt viewed with one octave smoothing correlates quite well with your Waterfall. There is also the Spectogram and the Filtered ETC.
 
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Soj

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My AV System  
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Amphion one18
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Thanks for taking the time and helping me :)
 

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You are welcome, is that a real LA2A? And the mic very sensibly covered by a plastic sandwich bag.....? 67 or 87? Looking at your pictures again I see shortie absorbers at the Side Reflection zones. Then a taller one behind.
I would move them about, to have as little as possible bare wall in the region between you and the speakers. Also, I wonder if your midrange resonance is coming from those acoustic guitars.....
 

Soj

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Amphion Amp500
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The LA2A is real but it’s the new version not the vintage one.
The mic I’m using is a u87 from 1974.
The plastic bag is from an article that I read regarding dust and sugar on out breaths mixing and sticking to the membrane.
Let me see if I got what you wrote straight I should remove the shorter traps from the side and put them on top of the larger ones next to the monitors?
You know I thought about measuring without the guitars in the room I just forgot about it but it was for that reason.
would you recommend me purchasing another bass trap for my front wall?
I admit that I did not fully understand what you said about Dirac as a software, does that mean it does not require the hardware unit to function?
If so is there a video on YouTube you can refer me to?
 

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The old 87 is very similar to the 67. I use plastic bags too. I think Neumann recommend them, but I am totally sure they are better than fabric bags and such. I am lucky to own a 67 and a 47!
Side reflections are more destructive than over head or floor ones. The area to be treated depends on the geometry of your speaker and listener positions. But typically it is a snooker shot exactly half way between your ear and the correspond tweeter. Get a pal to hold a mirror to the wall, move it about until you see the speakers, particularly the tweeter. That's the classic 'mirror trick'.
Because we move about I recommend covering a zone tweeter image as the centre. As ever with treatment the bigger and deeper the better.
All of your traps could benefit from a free lunch by spacing them out from the wall a bit. Equal to their depth is a safe bet. I don't know if they have Vids, but the DL manual should do it. It is software, standalone in the OS, AND a Plug in for your DAW. They have licenced it to quite a few Hi Fi brands, and minidsp.com boxes. I have both. I do a bit of Beta and User feedback for them. They are friends of mine. Ditto Sonarworks but I don't think they would mind me saying they are both excellent but DL is a tad better. https://live.dirac.com/content/uploads/2019/05/dirac-live-quick-start-print-version.pdf
I run a HDX rig so I am not familiar with Native systems. But now that DL is a plug in, you don't need to mess with the OS and third party drivers anymore. Just create a pair of Monitor outputs and insert the DL Eq plug.
 
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Soj

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I never tried the 67, I have rented a 47 couple of times and was very pleased with it.
The fact you have them both is amazing, I would love to hear some of the stuff you make in your studio.
What kind of monitors, conversion do you use?
Haven’t tried the mirror trick in a while I’ll try it today.
Given the results of my room do you think I could benefit from spacing?
I’ll give that manual a read!
 

DanDan

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Here's a 67 https://soundcloud.com/soundsound-ie%2Fvaj-vaj I have a ProTools HDX rig with HDI/O. The only thing I have heard which is probably better is a Lavry A/D
Neumann KH310. Extraordinary speakers, IMO as good or better than speakers 3 times the price.
Your room seems fine. If it were mine I would look at a sub or two or bigger speakers. You can probably improve the positioning of those side absorbers, and maybe introduce an air gap behind some or all of them.
What do you mean by spacing?
 

Soj

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1st of all the song is great i love the "just like rain" line and "because i love...you" and the melody and instruments opening up there :)
The vocals sounds very clear and full, The piano sounds amazing man, wow, did you mic it with 67 as well, what kind of a piano?
Is this your material?
hmm ill go to the hardware store this week and look for something longer that i can screw to the wall instead what holding the traps now -so i could space them, any reccomandations?
Had those neumanns for a try it way those vs pmc two two 6 (i preferred the newmann) in the end i went with the amphions.
Pm me your mail and ill send you some of my material :)
 

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