How to get started with room treatments for the home

[radix]

Here's the most recent measurements. Previously, I had failed to disable a lot of the dynamic EQ and mid range EQ in Audyessey. That is all turned off now. These are the L and R channels plus subs via Airplay.

From the spectrograph, it looks like I have some extra delay around 100 - 300 Hz. I'll work on chasing that down.

In the SPL chart, there's a bad bump at 60 Hz. This is the Denon 6700 crossover frequency I selected for the front. I might have mis-set the sub cross over frequency in Audyssey.

The left has bad dips at 88, 330, 700, and 920 Hz (eyeballing it, not from cursor). The right has dips at 120, 400, 570 Hz.

 

[radix]

I was able to locate some areas that were causing a few of the dips. I stuffed one area (above the keyboard) with pillows and then put up some cheap 12" x 12" x 1/2" panels in the other area. There are just some experiments to see how much a small amount of treatment helps.

That bump in the wall, by the way, is a chimney from the first floor. It's about an 18" square pillar.

Here's the LEFT + sub before (green) and after (blue). The orange panels mostly addressed the some of the 330 Hz dip. It brought it up almost 5dB. It also helped some with the 900 Hz dip.

For the right channel (before red, after cyan), the pillows helped with the 120 Hz dip and the orange panels with the 400 Hz some. At 400 Hz, I think it mostly shifted it left a bit and narrowed it up.

 

[sigbergaudio]

@radix But I assume Audyssey corrects the peak at 60hz? And if so that's not a concern. But more of a concern is the dip from 60-100hz. I would easily try a much higher crossover here, for instance 100hz.

I would not worry about the delay at 100-300hz, it's perfectly normal for the decay to increase with lower frequencies. If you feel like it you can of course add some absorbtion here and there, but you need to add about five times more than you think for it even to be audible.

It's interesting to see left and right individually, but it would also be interesting (especially in the bass and for the integration with the subwoofer) to see a measurement of sub + left + right active (so stereo with subwoofer). If you also do this both with audyssey disabled, as well as with audyssey + and dynamic eq enabled, you can also see what the room correction does. But try a higher crossover (you don't need to re-run Audyssey to increase it)

 

[Acoustics]

Okay, i'll try to guide you in the right direction. First of all there are a few myths and common advices across the net regarding acoustic treatment, that are simply false. People tell other people things they have read somewhere but never treated rooms by themselves.



1. Low End is the main Problem in every room, that is small (acoustic small!) That is the first thing to treat, everytime! Eq is not an Option. It is simply not possible to treat a problem in the time Domain with eq. "But i eqed my 10 db room Mode at 40 hz, it is great!" No, sorry it is not. The amplitude was lowered to a certain degree and room distortion was added because of the room modes. What you hear, is not the Signal how it was intended to be. It has too much decay. Often described as "Single note bass" in the worst case. It still does sound great to your ears ? Okay, it is fine. Just enjoy your music. Just notice, that there is room for a lot of improvement.



2. Treat corners first.

Simply no. Room modes exist between two Walls, not between corners. It is true, that pressure is a little bit more maximized in the corners but if you only treat them, you are not done.



3. RT60

RT60 needs a diffuse sound field to work. There is no diffuse soundfield in acoustically small rooms (less than 40-50 qm, depends on geometry) Use the spectrogram instead to make decisions.



4.

Choose the density and thickness of the porous Absorption Material depending on the rooms decay in the Bass Region.



Dedicated room 2ch:

5. Start with the Front wall, in my room 40cm of sonorock rockwool was the way to go.(works good down to 40hz) I built modules from floor to ceiling, covered the entire wall. Side walls were treated the same way, except the ER Points. I used qrd diffuers. Back wall depends on what is shown in the spectrogram. If everything is fine. (Max 500ms better lower in the 40 hz region) use diffusers. Otherwise use absorbers with an mls sequence, to not kill too much high tone Energy.

Ceiling is entirely treated with Absorption, except above the listening Position. There is diffusion used. That would be the optimal case, if you have a dedicated room and you can use it for music listening only. How does it sound? It sounds like a high end headphone with much more space, a huge stage without being unprecise. There is only the music and space.



6. What can i do, if i only want to listen to music in my living room ? Without tons of treatment ?

Google for dr. Geddes subwoofer placement guide. You need atleast 3. That is in my experience the best way to get an even bass Response with less decay. It's about stimulating the room modes more even. After that, Experiment with diffusers and absorbers to your liking on the ER Points.

I know this is oversimplified, but it is the best advice i can give to someone new to acoustics. If you want to dig deep, go to gearspace. If you Just want to enjoy your music and do not want to become a nerd, follow my advice. Have fun

Greets

 

[sigbergaudio]

@Acoustics it's a bit difficult to understand what was the myth and what was your truth in the first point, but if you're trying to say that EQ doesn't work in the bass, that's simply not true. So in that case you're doing exactly what you are accusing others of.

 

[Acoustics]

@Acoustics it's a bit difficult to understand what was the myth and what was your truth in the first point, but if you're trying to say that EQ doesn't work in the bass, that's simply not true. So in that case you're doing exactly what you are accusing others of.

Okay, it was oversimplified. Yes you can eq some peaks in the frequency Response to a certain degree. What you cannot do is eq dips that are caused by SBIR. What you cannot do is solve the problem of too much decay in the low end. A bass note is played and "smears" in the next one and so on. If you are lucky and you have a balanced frequency Response where your listening Position is, that is only in amplitude not in decay. So the low end will not be clear.
If you are right and you can solve all the low end Problems in a room with eq, acoustic treatment would be worthless. Why should listening rooms and studios be treated for a ridicilous amount of money, when you simply could tweak everything with eq ?

 

[ernestcarl]

Okay, it was oversimplified. Yes you can eq some peaks in the frequency Response to a certain degree. What you cannot do is eq dips that are caused by SBIR. What you cannot do is solve the problem of too much decay in the low end. A bass note is played and "smears" in the next one and so on. If you are lucky and you have a balanced frequency Response where your listening Position is, that is only in amplitude not in decay. So the low end will not be clear.

Some dips can be filled to a limited degree, but it comes with a cost -- oftentimes, it may be better to leave it alone -- esp. if you don't exactly know what you are doing.

Why should listening rooms and studios be treated for a ridicilous amount of money, when you simply could tweak everything with eq ?

That's a red herring... I don't think @sigbergaudio ever claimed the best way to deal with low end issues is to simply EQ it magically away.

No doubt EQ is certainly not the "be-all and end-all" solution -- who on earth here ever claimed to that? -- but depending in the particular room acoustics issue that needs to to addressed, it can be more (cost) effective to EQ than just filling the room with more acoustic treatment products.

 

[sigbergaudio]

Okay, it was oversimplified. Yes you can eq some peaks in the frequency Response to a certain degree. What you cannot do is eq dips that are caused by SBIR. What you cannot do is solve the problem of too much decay in the low end. A bass note is played and "smears" in the next one and so on. If you are lucky and you have a balanced frequency Response where your listening Position is, that is only in amplitude not in decay. So the low end will not be clear.
If you are right and you can solve all the low end Problems in a room with eq, acoustic treatment would be worthless. Why should listening rooms and studios be treated for a ridicilous amount of money, when you simply could tweak everything with eq ?

Please refrain from strawman arguments.

Below 100hz can be addressed effectively with EQ. Not perfectly, but effectively. Suggesting that people treat this frequency range with acoustic treatment in their homes is ridiculous and unrealistic. A purpose built studio is a different matter.

Above 100 and below Schroeder can benefit from EQ but it obviously won't solve all issues. A combination of eq and acoustic treatment is good for this frequency range. And dips from SBIR typically can't be addressed with EQ.

 

[Trdat]

Okay, yes seem like there's quite a bit of reverb in the low end.

Great thread. Thanks for the info about a lot of reverb. Also, following Radix's measurements. I won't hijack the thread but if you can just tell me if the below waterfall is better or reverb still exists quite a bit?

Below is a left right waterfall prior to my height and length mode subwoofers that I added recently. This way we can tell if it is a time alignment issue as both these subs are sumed as one for now, but I can time align them properly(within Audiolense) or purchase minidsp to seperately time align the subs.

Could you just confirm that the reverb is significantly better prior to adding the 2 axial mode opposing polarity subs, then I will know it is a time alignment issue? If not then, it must be a room dominant decay issue under a 100hz. Same parameters as the above waterfall.

 

[Trdat]

From the spectrograph, it looks like I have some extra delay around 100 - 300 Hz. I'll work on chasing that down.

@radix can you describe how you identify the delay on the spectogram?

 

[sigbergaudio]

Great thread. Thanks for the info about a lot of reverb. Also, following Radix's measurements. I won't hijack the thread but if you can just tell me if the below waterfall is better or reverb still exists quite a bit?

Below is a left right waterfall prior to my height and length mode subwoofers that I added recently. This way we can tell if it is a time alignment issue as both these subs are sumed as one for now, but I can time align them properly(within Audiolense) or purchase minidsp to seperately time align the subs.

Could you just confirm that the reverb is significantly better prior to adding the 2 axial mode opposing polarity subs, then I will know it is a time alignment issue? If not then, it must be a room dominant decay issue under a 100hz. Same parameters as the above waterfall.

View attachment 174106

The screenshot seems to be missing

 

[Trdat]

The screenshot seems to be missing

How about now?

 

[sigbergaudio]

How about now?

View attachment 174108

Could you please add the two you want to compare in the same post and make sure all three dimensions are identical?

 

[Trdat]

Could you please add the two you want to compare in the same post and make sure all three dimensions are identical?

I kept the setting the same. Both are left and right. The blue one is with the extra subs and the brown one is prior to adding the subs.

Let me know if you want a screen shot without the settings bar on the top right hand side?

 

[sigbergaudio]

So you want the waterfall / this graph to drop off as quickly as possible (as opposed to coming towards you).

So the brown one looks best, especially below 40hz.

 

[Trdat]

So you want the waterfall / this graph to drop off as quickly as possible (as opposed to coming towards you).

So the brown one looks best, especially below 40hz.

So it seems potentially it could be a timing issue causing the excess reverb.

I will have to add the two extra subs on seperate channels and properly time align them and see what results that gives me.

One last question, is there any way to know if my absorbtion panels are doing there job at least above 100hz? Or is the decay above 100hz also pretty bad? I ask only cause I have heaps of panels, either there density is to much 90kgm3 or there just not in the right place.

 

[sigbergaudio]

Probably decent but a bit hard to tell since the sound never seem to drop of completely. Background noise perhaps?

 

[radix]

@radix can you describe how you identify the delay on the spectogram?

I was looking for places where there are spikes above 200 msec. In my room, that's mostly around 100 - 300 Hz, where it spikes up to 350 msec.

From the feedback I've gotten, it sounds like those spikes are not anything to be overly concerned about.

What I'm trying to track down now are the 6dB (or more) dips. If I use the REW generator at one of those frequencies (e.g. 330 hz), I can clearly hear the sound level peak and rise as I walk around the room. Sometimes just one foot left or right makes a big difference.

 

[Trdat]

Probably decent but a bit hard to tell since the sound never seem to drop of completely. Background noise perhaps?

Can't be bagkround noise unless its the fridge...?

I'm adding a measurement from my second system again with DSP but its a DIY 3 way with a passive crossover and 4 subs, 2 subs at the front slighltly above the floor and another 2 in the back corners but the room has two open areas in the back on the left and right. Essentially I am width ways not lenght ways in which the seated area is in the narrow part and the subs near the part that opens further another metre or 2.

Anyway, I want to see if the reverb is from the system(horn/15inch) perhaps from the DSP or time alignment or will this(below) measurment confirm that the room manifests major problems regardless of sound system.

Below is two from the second system(3 way wide dispersion) and I will also add the brown graph of the previous system(horn/15inch) to compare.

If you could just tell me what you think? Just in simple terms if it room related or the system? The way I see it that the problems are room based although two measurements from the (3 way are different).

This one is the horn 15 inch system from the previous graphs without the added subs on opposite polarites which you said was the best.

 

[Trdat]

I was looking for places where there are spikes above 200 msec. In my room, that's mostly around 100 - 300 Hz, where it spikes up to 350 msec.

From the feedback I've gotten, it sounds like those spikes are not anything to be overly concerned about.

What I'm trying to track down now are the 6dB (or more) dips. If I use the REW generator at one of those frequencies (e.g. 330 hz), I can clearly hear the sound level peak and rise as I walk around the room. Sometimes just one foot left or right makes a big difference.

Mate, if no one tells you its difficult to understand so many of the nuances of REW. Thats a great help thanks so much, so simple yet so complicated.

Ill look into what is audible regarding delay, I am also curious now so I will research deeper but will take on good merit that they are not a major concern.

I am folowing your posts carefully and please add your process and results(the 6db dip) so we can learn.