Standing waves and room tuning

Hi-Fi Corner
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Hello Community,

This is my first post…
I have read quite a lot on this forum before venturing out to join and post…

Meaning of joining the forum is to seek advice on tuning my room, which now contains a new sound system.
I have put an Atom HE, NAP 250 (current gen) and a pair of B&W 703 S3’s in a Georgian lounge in my flat. The room is relatively square and I am running into standing wave issues with the low end…

The listening centre is pretty much in the centre of this (relatively close to) square and cubic room. The frequency response is quite interesting in the low end. It came over as confusing on tracks with a spectrum of bass from 30Hz to 100Hz. (Anything with a more advanced or complex bass line).

I have played individual sine waves from 20Hz to 100Hz to see what is actually going on with the response at the listening position and it looks subjectively absurd. Admittedly we are talking about my ears and subjective response, but there is a pattern. Although B&W do not publish frequency response curves, it is very clear what I am getting below is not what’s coming out of the speaker. Indeed, out of the listening position, standing either between the speakers or in the room corners the bass profile changes and what seems quiet in the centre seems loud in these positions.

rolloff from silence enters at about 25 Hz with soft and sweetly audible bass at 30Hz
30Hz to 40Hz → Response increases in shallow linear louder manner up to 40Hz
41Hz to 48Hz → Response decreases to very low response at 47 - 48Hz
49Hz to 52Hz → Response increases to medium/mellow response at 55Hz
53Hz to 60Hz → Response decreases rapidly and is low/flat/mellow to 60Hz
61Hz to 78Hz → Response increases again to 78Hz (at 78Hz, the volume is back up to as loud as at 40Hz)
79Hz to 88Hz → Response mellows off again to low but present levels
89Hz to 99Hz → Response increases to be at about 80% of subjective volume of the peaks at 40Hz and 78Hz

You may assume at this point that I am a bass heavy listener and wonder why I have the above set of kit at all and not a huge sub. This is not the case at all. I am a cross-genre music junkie and am very happy so far with the rest of the frequency spectrum of this setup. My focus is on the bass because this is where the only problem seems to lie and needs to be improved. It upsets the overall balance of music in a seemingly random and confusing way, depending on where the bass of any particular music matches the ability of this setup to reproduce it in my room…

For example: Bass heavy reggae with lots going on at 40Hz but not much else may sound sweet and great, but the bottom end of rock may sound wrong. Some hip-hop with bass variants in 50Hz range may sound wrong. Complex spectrum wide bass lines will just sound absurd. Dance/House is very hit and miss.

At first I had B&W 704 S3’s in this room, and thought there may just not be enough extension with the 5" woofers, so I listened to both the 703’s and 702’s in the studio and they both had much more bass extension but a very similar sound signature to each other. So I chose the 703’s and returned my 704’s, because the 702’s are down-firing (and also physically massive), and more expensive. I figured the rear-firing 703’s would allow more adjustment with positioning from the wall to get the bass response right.

Has anyone got experience with sound absorption panels and room tuning? I have been told by one company to send dimensions of my room and speaker locations and they will tell me what I need to buy and where to place it.
…I’ve been told by another company not to spend a penny on panelling until the room has been evaluated by someone with microphones and measurements, because I may be sold loads of panelling that does not do the right job first time…

All in all I’m a bit gutted my sound quality is at this sort of level with the sort of kit I’ve gone for.

I’m not exchanging any kit or spending any more on equipment until I have a more educated way forward…
I’m not buying a subwoofer. I’d only go down that road if I was also swapping the 703’s for standmounts like 705’s. I also have every reason to believe a subwoofer setup would have the same problems as the setup I have now…

Anyone faced a similar situation or able to recommend an approach or appropriate services to get this forward…

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Square rooms are ‘difficult’. :slightly_smiling_face:
Before you spend any money you should move your speakers and your listening position to the place where the boom is the least intrusive.

If it’s still too much then you are going to need some DSP. I use a Roon Convolution filter created by REW measuring software to reduce a room node at 50Hz, this works well and makes the bass much more tuneful.

I doubt that any acoustic panels will help at all at such low frequencies.

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Yes: as @Guinnless says would be my recommendation too. Home Audio Fidelity (HAF) make convolution filters for use with Roon that are great. Several of us on the forum recommend them. If you do a search for HAF or Home Audio Fidelity in the forum you will find lots of helpful information. All the best.

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Square rooms are indeed, very difficult, but perfect cube rooms are a nightmare! If changing the location or completely restructuring the room is out of the question then I think I would just go for really good headphones…

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I used to have similar bass problems when I ran a Superuniti with Kudos X2s (small floorstanders) in a square-ish room. In some parts of the room, the bass was severely lacking, and in others it was very exaggerated. I was more or less resigned to the fact that this was an unavoidable characteristic of the room.

I later embarked on an upgrade path, first adding a 200DR power amp, which improved things very slightly, then an NDX. Again, only minor improvements. Then I sold the Superuniti and bought a 282. Finally everything fell nicely into place, as you might expect with such a big preamp upgrade. What surprised me here was that the room node problem almost completely vanished. So I guess the quality of the bass must have been a key factor here, as the room dimensions that I thought were the cause of the problem were unchanged.

On the basis of that experience I wonder whether your Atom isn’t helping here. On paper it’s a pretty weak source/pre to be using with a 250. It would be interesting to see whether a Naim preamp on the same level as your 250 would help. That would mean something like a 282, or maybe a new 333 or 222, so it’s not going to be a cheap solution.

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Two threads worth a perusal if you haven’t already:

It can be very helpful to get a copy of REW software (free) and a measuring microphone (the one REW recommends cost around £110-120 last time I looked, half to three quarters secondhand and easily sold on if not required anymore), to find out what is going on in the room, and explore the effect of different positioning. Don’t forget that the listening position is every bit as important as the speaker positions. Bear in mind that sometimes unconventional layouts work, especially in awkward rooms, e.g. diagonal placement.

If playing with positioning doesn’t resolve your issues, GIK Acoustics, who make treatment products, can analyse REW files and even recommend what measurements to take, and from that recommend solutions, though of course aimed at selling their products.

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Thanks muchly for the replies!

Headphones:
I actually have a long headphone background. Current favourites are Etymotic ER4-XR’s paired with Snugs custom earpieces. This setup sounds out-of-this-world good when plugged into the Atom HE. I’d be surprised if any speaker setup outside of a tuned studio could match this for frequency response.

Buying more/higher end pre-amp kit/sources:
My source kit and amp is staying put for the time being. I accept that higher end source kit is more “matched” to my NAP-250, and well aware the NAP-250 is the high point of my system. The Atom HE is nonetheless what the NSC-222 is based on, and is designed as a balanced streaming pre-amp, with a streaming chipset ahead of both the Atom, Star and Nova. It’s what I can afford for now. An NSC-222 or something else may be in the future…but I don’t think this is the current weak point.
The weak point is very clearly my room and doing something with positions and wave adaptation/EQ if possible…

I also accept a £12k system is probably pocket change to some on this forum :wink:
I’m not so fortunate…yet…

EQ:
My concern here is that an adaptation of EQ at source (with no physical room correction) may well correct the frequency response at listening position, at the expense of dramatically over-driving my woofers and massively amplifying boom at other parts of the room, potentially bassing out my neighbours (which is another concern)

Boom
At listening position (centre), there is NO boom. There are only dips/flat spots. The bass response that is patchy, is at an appropriate volume and clarity for what is produced. The boom is at other positions in the room which are not the listening position…between the speakers and in the rear corners. Bass response is improved pretty much anywhere in the room except the listening position!!! :slight_smile:

Positioning/Furniture
The speakers are placed either side of a Georgian chimney breast, with a wood burner installed and a 48" OLED above it, with an East - West integrated cable tunnel mortared into the wall for a cable-free TV panel and speaker cable from left-right inside the wall (no floor running cables). It’s quite a design piece…
→ The approximate position is quite fixed in terms of whole room direction. Going diagonal or rotating 90 to another wall means disregarding a fundamental room design…

There is room for moving my speakers in their current positions, but I have already tried this to limited effect.

My next stage I think should be to try moving the furniture I am able to move to see if that makes a difference. There is also scope to move my sofa backwards more towards the rear wall, having moved some furniture away from said rear wall…

Room Adaptations
I’m pretty confident I’m going to try this direction one way or another in some form unless moving the furniture produces some miracle. From what I’ve now learned about square rooms I have my doubts…but I will report back…
I am surprised that this is condemned by some as pointless. Bass Traps are a known mode of resolving this sort of problem…I just have no experience whatsoever with how to approach this in a sensible, calculated financially efficient manner…I have no doubt I could be sold a fortunes worth of panels to be simply told “yeah try something else”. I do believe some practical physical solution exists…just that it may be very difficult to find…

…to be continued…

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For room correction you only ‘cut’ to level things out. This is how my Roon Convolution works.

Issues at sub 100Hz are not likely to be fixed with bass traps.

IB’s advice is well worth following :slightly_smiling_face:

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This is also how I believe HAF convolution filters work in Roon.

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Re bass traps. It is not that complicated unless you want it to be. Taming bassi’s all about quantity. Start in the corners and then back wall. Put some thin panels on the side walls at the reflection points.

I just kept adding bass traps as and when I could afford them. Not have 5 Gik corner traps 4 monster bass traps and 3 side panels

Makes a huge difference

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If you have Roon a cheap and easy test is to use the Housecurve app; it’s like REW but on your phone so need to buy a microphone. There is a thread on this already.

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With an expensive hifi I’d rather use a decent calibrated microphone than rely on my phone’s capability - after all the one recommended by REW is only about £120 new, around half to three quarters of that secondhand, and easily sold on when done if you don’t see any further use for it.

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In addition to what @Innocent_Bystander said, housecurve is not available on all phones. It’s iOS only.

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Look up the “Sumiko Masterset” method if you haven’t already tried it. I’ve had some success using it to set up speakers, including a pair of Naim allaes in a square room, but also some Thiel CS1.6 in a couple of others. In the case of the allaes 1/2” separated a one note bass from an even response, as judged by ear at any rate.

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Have you considered rotating the living space 45 degrees so that the speakers are firing diagonal 'each speaker on a different wall). This may help remove some of the 180 degree reflections that lead to standing waves. It certainly won’t be a cureall but it’s the first thing I would try.

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I want to check in and offer thanks for all your replies and suggestions.

I’ve experimented a bit with simple moving of sitting position and speaker position. 1 ft forwards/backwards seems to hit a sweet spot between 50Hz acceptable level and 40Hz boomy. In addition, I seem to be noticing the bass profile changing as the system initially ages (whole system was brand new). Dealer says to expect this.

Now this might be psychosomatic, but I’m sure I’m noticing a stronger low end profile when my amp is hotter, which is accelerated in the recent heat. It could also be my imagination or even my own hearing changing with the heat.

My listening position can never be diagonal. The window of variance is in moving sofa forwards/backwards, and the speakers in quite a wide variety of possibilities.

There is also furniture in this room that is planned to be removed, one piece of which will certainly affect acoustics a lot.

For this reason I think I will do the following:

  • Keep listening, enjoying system as-is (positioning and “burn in” seems to have improved a lot)
  • Await major furniture changes to take place
  • Following this, re-evaluate response and look into the REW measuring tools and/or professional help with adaptations and panelling…
  • At least this way, the expensive options (professional measurements and panelling) would be taking place on a room in a settled layout on a run in system.

I’m pretty sure some big improvements can and will be made. I’m sure this room can sound good…just not studio good!

Maybe I should have just bought a Nova and not gone Atom HE/NAP-250…

I have to say, apart from the quirky bass response, this system sounds really really lovely. I’m used to listening with Etymotic ER4-XR’s on snugs custom ear inserts. I did not think I’d hear a speaker based system approaching this for clarity and overall frequency balance…but this really does…

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While that is also likely in this hobby, it is well known that air pressure and humidity change how sound behaves.

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