Talk to me about Room Treatment

Soldato
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Just looking for some advice about DIY accoustic panels.

I've got a music/cinema room that I've built from one half of a double garage. So it's quite small at 3.8m x 3.3m x 2.3m, though I did use heavier materials like blue board, thick selatex and solid core doors to help the room not be too energetic, which seems to have worked as I don't seem to have any problem with the upper frequencies, just some of the ubiquitous bass ones!

Just to say, I'm not trying to make this into a recording studio and I don't have (or really understand yet) all the science about standing waves, room nodes etc, I've just been doing trial and error with various things and see what changes.

The main issue I had was a boom (or resonance/drone/thud - not sure how to describe it) in certain bass frequencies that I found distracting while listening to music. I've done all the things I can to isolate/stiffen the speakers and equipment from vibrations (and tbh, the bass is fantastically controlled) so I came to realise it's a room generated issue.

I've bought some cheapish "accoustic" foam bass traps for the rear wall corners behind the speakers, and tbh, they've done a good job - not only taming a lot of the bass boom, but made the mids/highs clearer and warmer*

The main issue I have now is the back wall reinforcement. The sofa is a little off the wall at 30cm, but the amount of bass reinforcement you get is significant. The difference between where the sofa is now and another say 60-70cm forward is very significant and noticeably improves the SQ. Unforunately, that just brings the sofa too close to the TV to be comfortable, so I prefer it where it is.

So I'm looking to make 4 panels to go across the back wall (and prob 2 more for the side wall 1st reflection) and wondered if there's any pointers and does or don'ts.

Size wise, I'm thinking something like 500 x 1200mm for 3 and 300 x 1200mm for 1 (as it goes on a narrow door on the back wall). Wood frame, suitable fabric cover and either rockwool or accoustic foam. But what thickness should I be aiming for. Common ones seem to be 2" or 4", so was thinking maybe 3" as a compromise as the back wall could probably take 4" ones, but it's going to be pretty bulky. Thinking about 2" ones for the side walls, again more for the aesthetics - even though it's a dedicated listening room, it's still got to have some form, not pure function! :p

I guess one concern I have is not over dampening the room, but doing a few calculators and they do seem to advise about 6 panels for a room of my size.


* I have found though, that when I put these floor to ceiling I find the bass stops dead and loses too much reverb (?) so the sweet spot seems to be only covering half the way up.
 
Thanks Mr Sukebe

Room nodes are directly related to the size of your room. Controlling those nodes is virtually impossible in a small room using passive traps.

Is it still not worth the passive traps for the reflection off the back wall?

The key options that I’m aware of are:
- buying speakers that have a frequency response that doesn’t extend to the same level as the room node (ie some small monitors)

Not looking to replace my speakers! :)

- bass control knob on some amps. I’m not a fan as these tend to be very broad brush about how they apply changes to frequencies and room nodes tend to be at quite specific frequencies, which are correlated with the size of the room

Yea, no EQ on my amp anyway, it's a Rega Elicit-R

- DSP. This to me is the Holy Grail for a typical UK house. Assuming you’re working with digital files, there’s a host of options now for creating a filter that reduces/eliminates very specific frequencies. There are plenty of COTS solutions, eg DIRAC, but it can also be fairly easily done with a Mic, laptop and a frequency sweep if you’re happy to keep it simple

I'm very happy to keep it simple!

I am working with digital files, using a Naim ND5 XS2 for the streamer. I don't really have a clue how to implement any DSP on my setup, could you explain in simple terms? I mean I understand that I need to find what frequencies are causing issues* but I would have no idea how to create a filter.

* I assume this is relevant - I was messing about on YT the other day and found a "speaker test" video and at one section it played a tone starting for 20K Hz down to 20 Hz iirc and when it started to get to the lower frequencies, there were significant increases in volume at ~125 Hz and again ~87 Hz (very roughly) and I assumed this was an indication of the problematic frequencies?
 
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Thanks Hornet

Basically output test tones to each speaker, and sub, using REW and UMIK1
Use REW EQ calculation to flatten peaks

I think my babel fish will be able to translate that ;)

Insert those filters into a streamer (wiim pro plus)

Seems my streamer doesn't accept any EQ filters, would your suggestion require replacing my streamer with the example Wiim or is the Wiim an additionional piece of kit in the network? As it would seem a bit of a downgrade from what I have.
 
Ref bass traps, I have a pair of GIK tri traps behind my speakers. They’re good for reducing some of the reflected sound, but in real world terms, help to clean up the low end and improve definition. I really don’t think that they made much difference to the room node that I have in our lounge.
For ref, our primary is +12db at 38hz, though it’s in a fairly slim band. We have a secondary of +6db at 76hz.

Yea, that's what I found too with the foam ones I put behind the speakers.

I knew the DIY panels wouldn't fix room nodes, I was just thinking of reducing the reflections to do more of the same as the tri-traps, as atm its just all bare walls and quite a small room.

Ref your Naim, sorry, I’m not familiar with its software.
Whilst the Naim streamer doesn’t have the capability, maybe the server/hosting software that you use does? If not, will the Naim work with another piece of server software that supports EQ?
Is your Naim Roon supported? Roon has PEQ features built in

It is Roon compatible, that could be a good option to explore, thanks!
 
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