Would adding room treatment provide any help?

[iulianm]

My system is in the attic which has a weird shape and I finally decided to try to add something (that would also improve it's aspect) but I am unsure how much it would help with anything.

I have never been to a treated room to get to experience how it would be (basically I don't know what I'm missing).

Any suggestions on what I could improve either by shuffling stuff in the room, adding some treatment on the walls? I am bad with design but I do like a good one when I see it and would also want to improve the aspect of the room.

My gear is Revel M106 and 2 x SVS SB-1000 and near the window I have the desktop speakers (Audioengine A5 with a sub as well that I actually quite a lot (and thinking to upgrade as well)).

I do have the Umik-1, measured with REW each speakers individually (with and without sub) and average is bellow:

With and without sub some measurements looks like this:

RT60 from REW looks like this (L and R speakers with sub on):

Attached as well the mdat file from REW.

 

[Keith_W]

ASSUMING you have taken the measurement properly, the short answer is yes, you need to do something about your room. I don't assume any more, some people mount their mics on mini tripods and rest it on their sofa or on a convenient surface, and wonder why there are so many early reflections. Or hold the mic in their hands. Did you use a boom stand and point your mic at the speakers?

Let's look at some curves.

This is the Energy-Time Curve of "L No Sub". As a rule, any peak arriving within 20ms of the direct sound should be -15dB. Your brain fuses early reflections with the direct sound and smears it, reducing clarity.

You can calculate which surface is responsible for which peak by calculating the distance using the speed of sound equation; d = t/1000 * c where d is distance, t is time in milliseconds, and c is the speed of sound (343m/s or 1125ft/s). For example, the reflection arriving at 1.9ms had to travel a further path of 0.65m or 2.14ft. Now look around your listening room with a tape measure and see if you can figure out which surface is responsible. From your pic, I would guess it's the wall behind you.

You did not state your room dimensions so I can not calculate a target for you. But the RT60 is on the high side. It should be between 250ms - 500ms.

 

[iulianm]

Thanks for the answer Keith! I'm going now through your comments to try to add more details.

ASSUMING you have taken the measurement properly,

Most likely not.

some people mount their mics on mini tripods and rest it on their sofa

That's exactly how I did it (I assumed since the point of the microphone is where my head is, it would be fine)

You did not state your room dimensions so I can not calculate a target for you. But the RT60 is on the high side. It should be between 250ms - 500ms.

Sorry about that! ceiling is 7.5ft; attached a schema with measurements.

 

[iulianm]

Would this help?

I have redone the measurements as I don't have other stand now and also added similar measurements from the computer desktop speakers (Audioengine) which are on the other side of the room.

 

[Keith_W]

Sorry about that! ceiling is 7.5ft; attached a schema with measurements.
View attachment 407450

Here is your RT60 target with upper and lower tolerances calculated for the volume of your room. Ignore everything below 200Hz, those are room modes and not reverberant fields. This is your older measurement, from "L No Sub"

And this is your newer measurement, from "Revel Measurement L without Sub". If anything, it looks even worse.

Cushions are not broadband absorbers. They absorb some frequencies and reflect others. It depends on the material and whether it is porous to sound or not. Read that REW help guide I linked you to carefully - do not introduce multiple unknowns into your measurement, like cushions.

Note that measurement strategies change depending on what we want to measure! Since the intention is to measure reflections at the listening position, the mic should be placed where the head would be. If you do not have a mic boom stand, you can duct tape the mic to a broom handle or long stick, then duct tape the stick to the staircase divider behind the sofa.

BTW to look at the Energy Time Curve, do this:

Click on REW's "Impulse" tab, then change the view from % to dBFS in the drop down menu. Then Ctrl-Right mouse button and drag to select the right area to zoom in to (first 30ms). Then click inside the box to zoom. Look for -15dB, and then look for any peaks above that.

I took a look at the ETC from your new measurements. The cushion appears to have knocked the first reflection down a little.

You have seen that even small changes in measurement strategy will result in very different looking measurements. When wavelengths are short, small changes in microphone positioning can and will result in big changes in what you measure. It is very important to have consistency and repeatability when taking measurements. I would put some markings on the stick and some temporary marking on the staircase divider (with masking tape or a light pencil mark) so that the position can be repeated.

In the end: I think you made many mistakes when taking your measurement which will increase the number of reflections that you measure. But despite that, I still think you have too many reflections in your room. It is very much on the high side.

What next for you:

1. Learn to take measurements with repeatability and consistency so that you can take "before and after" measurements.
2. Work out where to put room treatment by calculating the distance using the equation I gave you and finding the culprit surface.
3. From the RT60 it looks as if everything above 300Hz needs to be knocked down by about 100ms or so. This is the good news, it looks as if you don't need foam which is too thick. Foam needs to be 1/8 the wavelength of the lowest frequency you want to attenuate. 300Hz has a wavelength of 3.75ft (using a freq-wavelength calculator), so your foam needs to be a minimum of 0.5ft thick.

Good luck.

 

[iulianm]

@Keith_W: Thanks for the response! I will try to redo the measurements to get some consistency out.

 

[fuji]

Ignore everything below 200Hz, those are room modes and not reverberant fields.

Hi, how to measure reverb in low frequencies then? If RT60 in that matter is not relevant should we look at RT60 Decay or Waterfall instead to determine if frequencies below 200Hz are not reververant too much?

 

[Keith_W]

Hi, how to measure reverb in low frequencies then? If RT60 in that matter is not relevant should we look at RT60 Decay or Waterfall instead to determine if frequencies below 200Hz are not reververant too much?

"With great difficulty" is the answer. If you are sitting in a null, you will measure zero "reverb". Sit in a peak, and you will measure copious "reverb". It does not mean that the bass isn't ringing, because it most certainly is. But long wavelengths are position dependent.

I would EQ the bass peaks to a target curve, and then look at the decay (waterfall or spectro) after I do that. I am not sure if there is a better method so I will open the question to ASR.

 

[HiMu]

Now look around your listening room with a tape measure and see if you can figure out which surface is responsible. From your pic, I would guess it's the wall behind you.

@iulianm Here is a Amray raytracing save data based on your room floor plan. You can use this to compare possible reflections with impulse response/ETC

Amray - The Raytracing Sketchpad

Sketch your room shape and play around with speaker and listener positions. See in real time how you could splay walls to get rid of unwanted reflections. Or find out where all first andsecond reflections come from.

amcoustics.com

Copy this and press Load in Amray, and paste it in the "Paste from clipBoard"
41732112013112<settngs>BEAMTRC<spview>-1115.197613557205:-206.66729347479776:0.8486258728891327<sktchpd>3%$0.023634199778626908:0.054719923796056946,0.023634199778626908:792.0153590283685,-396.5146868470971:0.054719923796056946,-335.4276970956398:792.0153590283685,-335.4276970956398:395.2003318032987,-396.5146868470971:395.2003318032987,-474.5702848628481:0.054719923796056946,-474.5702848628481:196.66761511106233,-72.33523064748738:238.7586734629121,-72.33523064748738:0.054719923796056946#0:1,0:2,1:3,3:4,2:5,5:4,6:7,8:9%)-338.82141874849844:317.1447337875476%(-85.98915561052218:183.09272849962736%

Guesstimated speaker/listener positions and the stairwell railing structure, so fine tune them to match your situation.

 

[iulianm]

I've decided to limit the budget to $1k and go with GIK and used their tool to build up a mock on how I'll add some.

2D view:

3D view:

First person view:

 

[iulianm]

The panels should arrive mid to end of December, however I had a painting down in the garage that I put it on the back wall and did another measurement with the microphone in the same position (not that far from where my ears would be basically with and without painting (I did ~10 measurements in total)).

The painting is quite "thick" and I was so convinced that when clapping I could hear less of a reverb/echo that I did a measurement.

This is RT60 before and after (measurement with subwoofers on):

I will redo the RT60 once the panels arrive and add them here:

 

[bennybbbx]

you should measure speaker FR for left and right channel. because your system is not symmetric placed you get diffrent room modes for left and right speakers. to avoid more of diffrent on left and right speaker the room modes you can test with crossover frequency when you use the sub. I have treaten the room with ~15 qm basotect(melamin) 5 cm and have 6 melamin basstraps. but the results in sound is not much. I use arc 4 and it reduce the the bass time much more as my treaten do. i use treaten more for warming to save heating costs and i have no hope that resonators bring a good result for the money. best room treating and hifi sound is always put speakers as near you can so direct sound is higher as reverb sound. when have speakers far away as you have, then the direct sound is few and more reverb sound you hear. in this result my speakers are 80 cm away from ear

it is with and without arc the EDT. short EDT is most important hear .

another screenshot with 1/3 bands show more how arc reduce room modes reverb

 

[bennybbbx]

Ignore everything below 200Hz, those are room modes and not reverberant fields.

the room modes are the bad reverberants and bring the mud sound, i hear this because i too have a asymetrical speaker placement. without arc 4 i clear hear the reverb of my room sound from left. in the past my solution was add reverb on right speaker to compensate. but with arc it work without.

 

[iulianm]

Some of the panels started to arrive, the smaller ones:

In the next few weeks I should receive another eight larger panels.

I've done in my journey yet another set of measurements.

Left speaker before & after these square panels:

Right speaker before & after the square panels:

Currently the freq response for L/R speakers looks like this:

 

[iulianm]

All right, another six 46x23 panels arrived.


Overall it seems there's a reduction in RT60 by ~150ms from 300Hz+.

RT60 before I started this (Left & Right)

RT60 now:

Two more will arrive next week and that's it but the difference in considerable.