Whole wall acoustic treatment with fluffy insulation.

[Justdafactsmaam]

That's the kind of thing that real bass traps should help with. Kill (or reduce) the reflected waves and you kill (or reduce) the standing wave nulls/cancelations (and the anti-nodes/bumps).

...You can fix the bumps with EQ but it takes "infinitely large" subwoofers and "infinitely large" amplifiers to overcome cancelation.

You don’t really cure peaks with EQ you just put a band aid on them. The reverb will still be there in the impulse response

 

[neRok]

That's the kind of thing that real bass traps should help with. Kill (or reduce) the reflected waves and you kill (or reduce) the standing wave nulls/cancelations (and the anti-nodes/bumps).

...You can fix the bumps with EQ but it takes "infinitely large" subwoofers and "infinitely large" amplifiers to overcome cancelation.

I don't know what's going on in the 50-90Hz range. The rooms 2nd length mode is at ~82Hz, but it doesn't seem responsible when looking at the various charts and filtered IR, because it looks "normal", just quiet. But also the 1st width and ceiling mode are in the same range (~60Hz and ~70Hz), so they might be contributing?

Here's some results of my right speaker (the volume of REW/system was the same, but I don't know if the gain was exactly the same in EQ APO, but <38Hz looks the same, so probably the volume was the same);






There's obvious improvements across the board there. My room was totally untreated before with brick walls and floating timber floor, so not hard for there to be improvement. Is this improvement better or worse than normal panels, I don't know? Do normal acoustic panels achieve such effects at 100Hz? I've not looked closely but I don't think they do.

Here's the SPL, with sub included (no EQ or LP on it);

The sub looks great below 60Hz, but it too is suffering from 80Hz problem, and considering it is roughly in line with the speakers, is suggesting room mode. Maybe it makes sense, because the back wall is largely untreated, so there's a full force reflection coming and mixing with a diminished wave that came off the front wall?
Also the sub has issues above 100Hz lol. Good thing it doesn't need to operate there. The ~116Hz peak is the 2nd width mode, which makes sense because the room is basically not treated in that direction. I haven't thought about the big hole at ~180Hz.

There's 2 other interesting changes in that data;
1) the massive rise in clarity at ~200Hz, which also has a corresponding dip on RT60 graphs.
2) the lack of SPL in 400-600Hz range that corresponds with a blip on the T20 graph, and possibly it is dragging down the clarity graph too.

There's much to ponder here. Looking at filtered impulses of around 500Hz, it seems there are a lot of new reflections, which is hard to fathom (maybe the shelves?). I did see a post or 2 from other forums about mixing in some heavier density to target different frequencies, which I might consider. I wonder if just jamming in another piece of 2 in the very middle will help, as a pseudo "acoustic panel"? I might experiment with this.

Also on the experimentation front, I pulled down the 2 panels I put up near the door. These would have helped when my room was untreated, b ut now the state of things is completely different. So here I measured with 2 panels, just the bottom panel, and then no panels. It seems those panels were making things worse at ~500Hz. Very interesting. I will have to try them in other places and see what happens.

 

[neRok]

I've had many hours of listening to my system since doing this installation, and I'm really liking it! It's not the most impressive freq response, but I can play my music loud with no booming/honking, and that alone is a massive win. Even when I EQ'd in the past (when untreated), when it got loud, some instruments/etc would scream way louder than they should. Now it just gets loud and keeps sounding great.

It's pretty obvious when looking at the measurements I posted that there is a great deal of absorption happening between 150-300Hz, which must be the honky-zone. Because I just went and examined a selection of songs from my playlist (I listen to various types of metal), and it can't be a coincidence that so much of the songs energy is in the same zone. So that's a good explanation of the improvements for me.


Yesterday I did a bunch of experimentation with placing the panels I made around the room, along with a large box+dooner combo that I was using in the past, and even tried some pillows. I found that more stuff in the room generally decreases the RT60 and increases the clarity, but I couldn't find any combo that was an obvious big improvement. Nothing I did seemed to have an effect <300Hz, especially not at the 80-100Hz null I still have. There were some changes in the dip+peak at 400-800Hz, but also whilst experimenting I realised these seem to be very much desk related, because having the mic on the desk at head height vs holding it where my head would be (<30cm difference) would show pretty major differences. Pillows on the desk in front of the speakers helped the same zone, but I don't think I want anything there. And so after doing all that I also haven't decided how many more panels I will properly install yet (on the back and side walls).

On the 80-100Hz null I still have, I think I will lay my DIY subwoofer on the side and remove a portion of the insulation and push the sub in to that void. That way it will be closer the front wall, because it must be a mode problem and the insulation isn't doing much at ~80Hz, so putting it in a different location should help. (also I looked up some old speaker measurements and it seems a common occurrence for my room to have a null in that area when the speakers were 600-800mm from the front wall, which they still are now).

Also I bought 2x cheap bed sheets to cover the wall with. I did a quick test with 1 (just had it hanging, not properly installed), and it seemed to have minimal affect, which is good. Will post photos when I get it properly installed.

 

[Jorginho]

Well, things have been done. 3 shelves (4 layers) seems good. That's 2 bags on the wall, and I've got a 3rd if need be (was thinking of doing a panel in on the odd shaped rear wall I have).
View attachment 327154 View attachment 327155

I've done a quick sweep and there is improvements but also a bit of a hole around 80Hz which isn't nice, but I'm too exhausted to get in to it further today.

That is insane! A really good type of insane that I wish I could afford (still have a wife I want to keep).

 

[neRok]

I've been really enjoying the results of this treatment effort. I haven't thought about DSP or anything like that for months. I just sit down, push play and enjoy the results.

But yesterday I had the desk out and decided to change the sub location like I think I mentioned earlier. Here's where it is now;

(Yep, haven't covered the wall yet lol. I don't even notice it now. I have no dust/allergy problems to report.)

I made no DSP changes and had a quick listen and could tell that the hole/null around 80Hz was a bit improved, but obviously the timing was a bit off now so I think there was a bit on cancellation elsewhere. But the bass sounded louder so I actually turned the gain down a little for the sub. Then I turned the system up and I think I was starting to feel some impact whilst I was "free standing" in the room. Nice.

So I just did some quick measures to compare to the results earlier in the thread. Here's the sub without EQ or LP in the 2 different positions;

So yep, moving the sub helped nicely. I haven't looked at the timing side of things yet.

I did a quick impulse alignment, and again I can see the improvements in 60-90Hz range;

It's still not great, but it's good enough for tonights listening session. I had the LP at 75Hz so it basically used the 80Hz null as part of the slope, but now I've changed it to 105Hz. I will probably try get it a bit lower, but it might need some different EQ or allpass tweaks here and there to get things in sync better than shown. And now that I'm happy with the subs position, I will put more effort in to the speakers HP. So that DSP design process is going to take some time, so I will do it another day. But things's are looking positive to me.

Edit: One thing to mention, the "L+R+Sub" is with the gains equal, but actually I've been running the sub a fair bit louder, which I'm guessing was helping to fill the hole. Now that I don't have the hole, it seems I don't have to run it so loud. Because in the past up to ~90dB I've been running it about +4dB to +8dB above the speakers depending on the song (I regularly change it depending upon where the song/album has the majority of its content mixed), and those numbers reduce as the volume gets towards 110dB, so I only run sub 0 to +3dB when listening near "full volume".