Problem with bass region (100 - 200 HZ) - any suggestions?

[nstu]

Hello, (and sorry for my bad english)

i hope to find some help here for my next decision.
Long story short: I build my project studio in 2011, room in room by myself. After some years now many things have changed and also my understanding and listing of engineering.
Most of the time I got the sound I want with reference tracks and listing on many many things (headphones, cars, etc).
I ever know I had to deal with an unclear bass region but it works ""okay and my clients very happy in the end.
For some weeks I tested the sonarworks reference 3 plugin and was really shooked what it dose to my monitor sound and I liked it. The plugin tells me already what it dose but I did another measuring with the REW app and the results seems to align.

I have a „big“ problem between 100 and 200 Hz. (beside that dip at 70 Hz)
I also testet some more DIY absorber, but that did „nothing“. I also placed my Neumanns more back to the wall, but I get crazy dips under 100 Hz, so there were they are yet it is still the „best place“. I also did a measure through the Yamahas and the problems are in the same range (a bit higher) but still near the 100 Hz.

Now I am at the decision to contact a professional acoustic company to make a real measure and to offer me a possible solution for my problem.

I like DIY and learned a lot in the last years but I think that one is to tricky for me and I want to do it right.
But also I want to get some Ideas to know and maybe an alternativ solution to test before I make the pricey step with some one else.

So what do you think could help to tighten my bass at around 100 Hz and 200 Hz?

I did the REW measurement with an soundlux ECM-999
and the sonarworks with the sonarworks mic incl. a mic file for that mic.

Room Info:

Hight is 3 meter
All walls are regibs with 10cm rockwool sonar rock behind.
All absober are DIY with 10cm rock wool sonar rock as well.

I appreciate any feedback and hope that I don’t miss any informations. I load up some pictures, the plan with the room infos and the REW file as well what sonarworks tells me by the software.

If you need any more infos please let me know.
Thanks, Niels

[Soundman2020]

Hi Niels, and welcome to the forum!

There are several problems with your room that are visible in the photos. Firstly, it is clear that you do not have any bass trapping in there! Without bass trapping, it is impossible to get the low frequencies under control. You are going to need to make some very large bass traps. The small panels you have in there right now are far short of what you need. They won't do very much at all, and they are also in the wrong places.

There also seem to be issues with the room layout and the geometry of the listening position / speakers, and I suspect there are problem with the way the soffits are built (the "soffits" are the angled parts of your front wall, where you have the speakers installed). There are other problems too, I suspect, but those are the ones that are obvious.

Your graphs show a little bit, but in order to understand the real problems with the room, I would need to see the actual MDAT file created by REW. Please post it some place that can take large files (like Dropbox, for example), then post the link here on the forum so I can download it and analyze it completely.

The problem at 100 Hz is certainly a room mode, and several of the other problems also appear to be modal, but you have the scale to coarse to be able to tell. You should be looking only 20 Hz to about 400 Hz, and you should also be looking from 30 dB to 110 dB on the vertical scale. The way you are viewing the data in your graphs is distorted, so we can't see properly what is going on.

Also, it seems like you did not measure the dimensions of your room correctly. There is very, very definitely a modal issue at 100 Hz, but when I use the dimensions you gave, there are no modes in that region, that could be causing such a huge problem at 100 Hz! There are some tangential modes around there, but I'd bet good money that what we are seeing on those graphs are not tangentials: they are almost certainly axial modes. However, with the dimensions you gave, the closest axial modes would be at 90 Hz (0.2.0 mode) and 115 Hz (0.0.2 mode).

How did you measure those dimensions? You need to measure all the way to the hard, solid, rigid, massive boundary of the room, not to the face of any treatment devices in the room. So please check your dimensions, and make sure you are measuring all the way to the surface of the real walls.

I like DIY and learned a lot in the last years but I think that one is to tricky for me and I want to do it right.

You can fix it yourself, for the actual construction: That much is very clear, since you already did a really nice job building it the first time! It just needs to be designed properly. Your building skills are fine, but you need the design done properly, so you can build it.

But also I want to get some Ideas to know and maybe an alternativ solution to test before I make the pricey step with some one else

It MIGHT be possible to get some good improvements by treating your room correctly, but I am not convinced about that. I'm not sure that treatment alone can do the job. I suspect there might be underlying issues caused by the way the room is built, and that you might need to modify some of that.

Please explain how the soffits are built: Do you have any photos from when you were building them? If so, then please post those photos. Also tell us in words how you built them: what type of framing is holding up the soffits? What are the front panels of the soffit made of, and how thick are they? What is inside the soffit? How are the speakers attached to the soffits? I suspect there may be a problem with that. It is also possible that the 100 Hz problem you see is related to some type of resonance going on inside the soffit, but I suspect that it is actually a modal problem. However, I also suspect that there are other issues with your soffits...

If you need any more infos please let me know.

First, you need to re-calibrate REW and do your tests correctly, and send me the MDAT data file, so I can analyze it properly. Use a hand-held sound level meter to calibrate REW at 85 dB (NOT 75 dB as it says in the manual: this is a control room, not a home theater, so the calibration and testing need to be done at 85 dB).

Then run a series of REW tests, with "start frequency" set to 15 Hz, "end frequency" set to 22,000 Hz, Level set to -120 dB, "Sweeps" set to 2, and "Start Delay" set to 10 seconds. The purpose of "start delay" is to give you enough time to get out of the room and close the door before the test starts, so that it can run without anyone in the room. Your body is enough to affect the acoustics in the room.

Next, make sure that there is no EQ anywhere in your signal path: Id you are using a channel on your console, make sure that the EQ on that channel is flat. Also if you are using a mic pre-amp, make sure that it has no EQ settings in use.

Next, set up your mic so that the tip of the mic is exactly where your head would be while you are mixing normally, and the mic is pointing upwards at an angle of at least 45° to 60°. It must not point straight ahead.

Now run one REW test with only the left HS80 on (the right one must be turned off, or signal disconnected). Then do another test with only the right HS80 turned on (left one turned off): Then do another test with both speakers on. Do not change any settings between tests!!!! Make a very, very careful note of exactly what settings you have on the entire signal path, so that you can set things up again exactly the same for future tests. And also measure the exact location of the tip of the mic in the room (accurate to within 5 mm) and write that down, so you can get it back to the prices same location for all future tests. It is very important that you do all future tests in the exact same way, with the same settings on all of your equipment, and the mic in the same position.

In your REW file, mark which test is "Left only", which is "right only" and which is "both", then send the MDAT to me. I'll take a look at it, and let you know what I see.


- Stuart -

[nstu]

Hi Stuart,

at first - many many thanks for your response and all words!

I will get into that to make the right REW files (as you describe) at the coming weekend and will provide you as much info and photos of the bulding stage that are helpful.

When I build that room I though that was the best way - today I would do many things different. I would not do soffits myself again, because I think that was not so a great idea for the first building and if it helps to make the room better now I would change this immediately and put the yamahas right next to the neumanns.

However, I will get back to you when I have all the files ready!

Thanks again!
Niels

[nstu]

Hi Stuart,

it had no rest me.
I set up all again (as you said, as well with the mic position and the 45°-60°, checked levels, measured all again and did a new room measure (your were right, I had a big mistake in my plan notes). The measuring is with my apollo with nothing on chain right from the apollo to my PreSonus Central Station. All boxes have no EQ or Room-Correction engaged, so they are also flat. I hope that the measure is right now. (I took notes and photos form my setup and chain to set it up all again for another measuring check)

I measured the KH120 (both, left, right) as well the HS80m (both, left, right) - all is in that file from REW 5. I put notes as well in the measuring files where the boxes stands and the length to the mic position. I also left the room by the measuring process as you said.
I found some old pictures about the building stage. Including with the new room info all is in that folder that you can load here as a ZIP.
(The room hight is still 300cm)

https://dl.dropboxusercontent.com/u/103 ... 2-2015.zip

The KH120 are my "main" monitors and as I said I would also pull out the HS80m off the wall and place them beside my KH120 to make it a better listing room.
I think (today) that my soffit is not correct what I build years ago (where I thought I can do that) and would now change that.

But it will help me a lot to know what and where I can do something with acoustic panels (bass traps, absorber, diffusor) to make the room better.
If I had to build my own panels I would probably ask my neighbor (he is an professional joiner) if I know what I need to get build if I can't buy any existing panels that suites my needs.

So again, thanks for your help!

Best regards,
Niels

[Soundman2020]

The KH120 are my "main" monitors and as I said I would also pull out the HS80m off the wall and place them beside my KH120 to make it a better listing room.

If the KH120s are your main speakers, then you should soffit mount those! Put your best speakers in the soffits, so you get all of the benefit of the soffits for them.

I think (today) that my soffit is not correct what I build years ago (where I thought I can do that) and would now change that.

If you want to re-build your soffit, that would be excellent: we can help you design it so that it works well with your KH120's, which are very nice speakers, by the way!

You could then use the HS80's as secondary speakers, for checking your mixes.

But it will help me a lot to know what and where I can do something with acoustic panels (bass traps, absorber, diffusor) to make the room better.

I will take a look at your MDAT and other data, and give you some suggestions later.

If I had to build my own panels I would probably ask my neighbor (he is an professional joiner) if I know what I need to get build if I can't buy any existing panels that suites my needs

It is not hard to build basic treatment, and it is cheaper than buying commercial panels. As long as you can use a hammer, tape measure, and a saw, then you can do it.


- Stuart -

[nstu]

Hi Stuart,

first of all - happy new year!

Thanks for taking time to give me some suggestions on my problem.

If you could give me some ideas how I can get rid of the peaks at the low end would be perfect. I am not really sure if I want to build new soffits but I would design the front or even back wall complete new if that has to be done. If I could deal with other solutions like bass absorber or anything would be better for sure.