Speaker placement, reflections, cancellations, modes - making the best of a bad job

All general audio posts go here.
User avatar
karatestu
Posts: 4982
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Has thanked: 1162 times
Been thanked: 680 times
Great Britain

Speaker placement, reflections, cancellations, modes - making the best of a bad job

Unread post by karatestu »

First off I want to say I am nowhere near an authority on this. Some may say they are not overly bothered about such things but I believe it is worth trying to understand the issues so you can make the best of a bad job. Can't polish a turd though.

Many of us here are semi omni lovers :romance-grouphug: but we face the same problems as the point and squirt brigade. Also as filter dodgers and prone to complexity dodging we don't have any baffle step comp circuitry to enable the speakers to be away from the wall where they usually sound the best. They have to be close to the front wall to get the level of bass we need to marry with the higher frequencies.

As we have chosen semi omni then I presume imaging is not the be all and end all for us. But even so, why not make the best of what we have - there is no harm in that is there ? Early reflections are bad for imaging (Haas effect) yet our speakers need to be close to the front wall and the up firing mid bass is producing very early reflections off the said wall. Nothing we can do about it really apart from treatments on the wall. That would help with the frequencies down to a point . But we need the later reflections otherwise we will only hear sound which is of a purely omni directional nature. So keeping the speakers away from the side walls if possible is probably going to help.

Then we have destructive cancellation from sound waves bouncing back from a boundary (walls, ceiling, floor) and combining with the front wave out of phase causing a dip. There is nothing worse than following your favourite bass players lovely flowing parts and suddenly one or more notes disappear or are severely reduced in level. Then there are room modes which cause peaks at certain frequencies making the whole thing even worse. This might not bother you - it annoys the hell out of me. These cancellations can occur higher up than the bass as well depending on distance to the reflection point and the wavelength of the frequency concerned. They can be calculated but I guess nobody here has gone to that length or are even bothered.

Floor bounce from a woofer can be a pain in the arse and it can affect mids as well - high frequency is often mopped up by a carpet or rug if you have one. Doc always referred to Roy Allison's work on boundary effects. He was known to put the woofer as close to the floor as possible, cross it over low and put the mid near the top of the baffle with the tweeter. A compromise was made here as the woofer and mis are a long way from each other but it was crossed low which is better for keeping the centre to centre distance within a quarter wavelength at the xover frequency (speed of sound divided by distance divided by four ?)

Cube users can't get the bass driver at floor level but you can get it close to the front wall which should help with cancellation in the bass but it will move higher up in frequency. It may have to reflect off at least one other boundary (the ceiling) to reach your lug holes as the mid bass is usually above ear height in order to get the front firing tweeter to ear height.

Point and squirt users can't get the centre of the bass driver as close to the front wall as cubes and maybe they don't need to and have adequate bass a little further out into the room. But the destructive cancellation will be at a very noticeable frequency. The general advice is either get the speaker as close to the wall as poss or over a metre out into the room. I can't live with speakers that far out so I am stuck with wall placement :(

I have tried my speakers near the centre of the room well away from walls and the listening position being nearfield. The worst place to be seated is against the back wall especially if the speakers are tight up to the front wall. I situated my chair as far from the wall as I could. It was the best sound I have ever heard in this room. With conventional cubes that are not baffle step compensated I expect the bass will be too far down in level due to lack of boundary reinforcement. Room gain will help but it will probably not be enough. They will sound thin and fatiguing. In my case I got away with it because the bipolar up and down firing mid bass provided very good levels of bass due to it's inherent baffle step compensation and I have tweeters pointing in various directions. I was absolutely in love with the amazing clarity of the sound. I even moved the two speakers next to each other so they only had a mm or two between them. No stereo imaging and not much sound staging but I loved that even more. It is a real shame that this set up can't be accommodated in my living room at home :crying-blue: :crying-blue: :crying-blue:

So what can we do about these problems? Ignore them ? That is a possibility but with a little effort we can make the best of a bad job. DSP is all the rage these days - music killers as Doc would say :grin: New devilry imo. I could live with the idea more if the chain was all digital before it but converting an anologue signal to digital andthen back to anologue is just all wrong in my book.

We could invest in room treatments but who in the real world would go to the effort, expense and prospect of row inducing aesthetics . Bass traps have to be ridiculously large to have an effect. Panels for higher frequencies at first reflection points may be acceptable to some but not me though. The best option imo is to fill the room with the possessions of life - some of us who don't have a dedicated listening room with extremely directional speakers and a single chair with vice to hold your head still (a very unsociable and selfish way to listen imo) have to live in the same room as the hifi. Shelves full of books, cd's, vinyl and the clutter of life can act as diffusers for higher frequencies.

Have a carpet or at least a rug at the first reflection points. If you are listening with a family present spread across several sofa's then the right thing to do imo would be to carpet the whole room. If it's just you :( then a rug would probably suffice. I once thought of filling the voids in my sofas with bass absorbing material. Then I realised the sofa would have to be a frame type so a fruitless exercise in my case.

I would say that there is nothing we can do about ceiling reflections and as semi omni lovers we need the ceiling. My ceiling is textured (Artex) but no idea if that helps at diffusion at all or even if it is desirable with up firing drivers.

You often read of hifi nut's swapping speaker after speaker and very rarely find something they are truly happy with. That is a shame imo. If only more were in to diy speaker building as it really is an excellent way to design and make a speaker system which suits your ears and room. Different aspects can be changed. Too much bass right against the wall - make the box bigger or change the driver for a slightly lower efficiency one and cross over to the mid at the middle of the baffle step transition. Or use a dedicated amp for the bass driver and give it it's own volume control :shock: Or even buy an amp with tone controls :laughing-rolling: :laughing-rolling: :laughing-rolling:

Lately I have been trying to get the down firing bass driver as close to the floor as possible (going to try as close as an inch) for boundary reinforcement and to try and minimise any floor bounce cancellations. That is what is pointing me in the direction of going to a three way as having mid frequencies rattling about down there doesn't sound like a good idea to me. The mid can be up firing into my tweeter sphere.

Another thing I found which helps with room modes is to set up your speakers across a corner with each speaker on a different wall. Works a treat in my room with my gear. It has the added bonus of making the sound field/ stage seem deeper as you have some distance behind the mid point between the speakers.

Failing this just go open baffle if you have the room, dsp and some muscle amps. Or buy some of them Dutch & Dutch, Devialet, Buchard or similar whatsits that can also make you a cup of tea and wipe your arse at the same time. Your fooked if they go tits up though.
These users thanked the author karatestu for the post (total 2):
CN211276 (Sat Oct 16, 2021 11:08 am) • Fretless (Sat Oct 16, 2021 12:00 pm)
DIY inspired by Richard "The Doc" Dunn RIP

User avatar
karatestu
Posts: 4982
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Has thanked: 1162 times
Been thanked: 680 times
Great Britain

Re: Speaker placement, reflections, cancellations, modes - making the best of a bad job

Unread post by karatestu »

I'm loving the replies so far on this thread, keep up good work. At this rate I will be forced to emigrate to pfm for somebody to talk to. I will be carpet bombed with graphs, equations and comments that I have no idea what I am talking about whilst they have a good chuckle that I can't really be serious about music reproduction.
DIY inspired by Richard "The Doc" Dunn RIP

User avatar
Lindsayt
Posts: 3586
Joined: Fri Jul 13, 2012 9:06 pm
Has thanked: 387 times
Been thanked: 293 times
VATICAN_CITY

Re: Speaker placement, reflections, cancellations, modes - making the best of a bad job

Unread post by Lindsayt »

Big rooms with a lot of furniture or clutter in them seem to be the sort of rooms that can house a variety of speakers with the acoustics not being an issue for any of them.

For sure different speakers can sound best in different locations. The 2 biggest extremes that I have are my EV Patrician corner horns that sit with their rear 1" from the corners and my infinite baffle Bozak Symphonies that are pulled out 2 or 3 feet (I've never measured it) into the room.
With the positioning of the speakers being what gives the cleanest bass.

In my rooms I've never seen acoustics, room cancellation and nodes as a big deal. The overall quality of the system and a nice variety of music are far bigger deals.

If I had a small acoustic band playing live in my room I wouldn't be thinking about the acoustics, nodes and all that. I'd just be enjoying the music.
If the signal that my system puts out is close to a live band in my room then I'll get on with enjoying the music.

I have been in one or two homes where the listening rooms have had problem acoustics. As in crazily echoey bass. And for them DSP and that jazz makes sense.
These users thanked the author Lindsayt for the post:
karatestu (Sun Oct 17, 2021 9:39 am)

User avatar
SteveTheShadow
Posts: 1477
Joined: Thu Sep 12, 2013 5:24 pm
Has thanked: 140 times
Been thanked: 190 times
Great Britain

Re: Speaker placement, reflections, cancellations, modes - making the best of a bad job

Unread post by SteveTheShadow »

Personally, I think that far too much is made of this business of speaker/room interaction. Concert hall acoustic engineering design is a serious science, populated by serious people, who know what they are doing and why they are doing it. The professional arena is a different world entirely to the domestic listening environment and those who purport to apply the same rules to a tiny (by comparison to a music venue) little domestic room are simply spouting pseudo scientific bullshit of the worst kind, in order to prize money from the wallets of the gullible.

IMHO it is piss poor speaker design rather than ‘difficult’ domestic acoustics that cause 99.9% of problems. Anyone who tells you that you can create concert hall realism in a domestic room is talking total shite and is not to be trusted. They are selling a lie and I don’t know which is worse, the shysters purveying the gear or the eejits that fall for the bullshit they spout.

A slow 12dB/octave rolloff of frequencies below 50Hz will solve 99% of ‘room’ problems. If you want bass down to 16Hz you are going to have to listen in a concert hall, so stop trying to pretend otherwise folks. As a famous fictional starship engineer once said ‘I cannae change the laws of physics captain.’

Trouble is that the 20-20KHz paradigm is so ingrained that any speaker not doing that range flat to within 0.0001dB will get panned, even more so, if it is a big bugger like my Fanes or Lindsay’s EVs. Thing is, the old guys knew a lot more than they are given credit for and were extremely canny designers infused with a healthy dose of pragmatism. Yes, they built big speakers, but they also built for real rooms rather than anechoic chambers.
These users thanked the author SteveTheShadow for the post (total 2):
Lindsayt (Sun Oct 17, 2021 12:08 am) • karatestu (Sun Oct 17, 2021 9:39 am)
Molly Winley, she smooks loike a chimley, but she’s my little nicotine gal.

User avatar
CN211276
Posts: 5337
Joined: Tue Aug 09, 2016 9:29 am
Location: Cardiff
Has thanked: 591 times
Been thanked: 420 times
EUROPEAN_UNION

Re: Speaker placement, reflections, cancellations, modes - making the best of a bad job

Unread post by CN211276 »

karatestu wrote: Sat Oct 16, 2021 8:32 pm At this rate I will be forced to emigrate to pfm for somebody to talk to.
God forbid. :lol: I was banned years ago but was able to rejoin last year with a new email address I had to create to take up the Tidal Black Friday offer. I have not posted because I can have a more intellegent discussion with my five month old grandaughtinstigat


I concur that speakers should be designed to take account of the listening room. A modest system which interacts with the room will sound better than a silly priced one which does not. Out of necessity my speakers need to be close to the wall. I was concerned that the upgrade from Cube 1s to 3s might lead to over blown bass, but as Richard Dunn advised this was not the case. I am content that there are no frequency anomolies. The Sbooster PSs which I connected to my source components not so long ago extended the bass and initially there was a lack of control. After some running in things settled down and definition became spot on. I have found that changes to furniture and rugs
have affected the frequency balance, but not to a great extent. I have been able to compensate by changing the subtle filter settings on the DAC. As well as the frequency balance I am very happy with the sound stage and imaging, optimised by experimenting with the toe in of the Cubes and distance apart.
These users thanked the author CN211276 for the post:
karatestu (Sun Oct 17, 2021 9:42 am)
Main System
NVA BMU, P90SA/A80s (latest spec), Cube 1s, TIS, TISC(LS7)
Sonore OpticalRendu, Chord Mscaler & Qutest, Sbooster PSs
Network Acoustics Eno, ifi iPurifier3, Audioquest Jitterbug FMj, Cisco 2940 & 2960
DH Labs ethernet, BNC & USB cables, Farnells cat 8 ethernet cable

Second System
NVA P20, A20, Cubettes, LS3, SSP
Sonore MicroRendu, Topping E30 MCRU PSs, Audioquest Carbon USB cable & JB

Headphones
Grado SR325e/Chord Mojo, Beyerdynamic Avetho/AQ DF Red

RIP Doc

User avatar
karatestu
Posts: 4982
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Has thanked: 1162 times
Been thanked: 680 times
Great Britain

Re: Speaker placement, reflections, cancellations, modes - making the best of a bad job

Unread post by karatestu »

I wish I had never tried my bipolar speakers and listening chair well away from the walls. Unfortunately I can't un-hear it. I am all too familiar with piss poor speakers - I've made a few :grin: I can't now ignore the fact that rooms and boundaries are bad. If I could I would have a single speaker with both channels coming from it and positioned about a third of the way into the room. Seating similarly away from the walls and listening near field.
DIY inspired by Richard "The Doc" Dunn RIP

User avatar
savvypaul
Posts: 6730
Joined: Tue Oct 11, 2016 7:14 pm
Location: Durham
Has thanked: 1057 times
Been thanked: 1145 times
Contact:
Great Britain

Re: Speaker placement, reflections, cancellations, modes - making the best of a bad job

Unread post by savvypaul »

I've found that natural materials work well. Wool carpet with decent underlay, rugs, cotton or leather sofas, textured wallpaper, lined curtains. Books and LPs are great for breaking up reflections, as is 'general clutter' (though you don't want your 'stuff' to shake, rattle and roll with the music).

Experiment with speaker positioning to understand where the room's null points / bass nodes are. Also experiment with listening position.

If you want bare surfaces in a fairly empty room / or you must have your speakers in only one spot, DSP / EQ can treat some of the symptoms. I would use it for doing shows where we have no control of the furnishings and often very little choice about speaker positioning.
I am in the hi-fi trade
Status: Manufacturer
Company Name: NVA Hi-Fi
https://nvahifi.co.uk/

User avatar
CN211276
Posts: 5337
Joined: Tue Aug 09, 2016 9:29 am
Location: Cardiff
Has thanked: 591 times
Been thanked: 420 times
EUROPEAN_UNION

Re: Speaker placement, reflections, cancellations, modes - making the best of a bad job

Unread post by CN211276 »

CN211276 wrote: Sat Oct 16, 2021 11:28 pm Out of necessity my speakers need to be close to the wall. I was concerned that the upgrade from Cube 1s to 3s might lead to over blown bass, but as Richard Dunn advised this was not the case. I am content that there are no frequency anomolies. The Sbooster PSs which I connected to my source components not so long ago extended the bass and initially there was a lack of control. After some running in things settled down and definition became spot on. I have found that changes to furniture and rugs
have affected the frequency balance, but not to a great extent. I have been able to compensate by changing the subtle filter settings on the DAC. As well as the frequency balance I am very happy with the sound stage and imaging, optimised by experimenting with the toe in of the Cubes and distance apart.
Image

This is the listening part of the room which is open plan and comprises the length of the down stairs. The right speaker is not close to the side wall and the left speaker is a long way from the patio door, though close to the solid wooden rack. The leather sofa in view with cushions and the rug, with decent underlay, minimise reflections. Nearly all of the rest of the room is uncovered wooden floor. The listening sofa is also leather and higher than the one in view and close to a wall.
These users thanked the author CN211276 for the post (total 2):
karatestu (Mon Oct 18, 2021 4:01 pm) • savvypaul (Mon Oct 18, 2021 8:08 pm)
Main System
NVA BMU, P90SA/A80s (latest spec), Cube 1s, TIS, TISC(LS7)
Sonore OpticalRendu, Chord Mscaler & Qutest, Sbooster PSs
Network Acoustics Eno, ifi iPurifier3, Audioquest Jitterbug FMj, Cisco 2940 & 2960
DH Labs ethernet, BNC & USB cables, Farnells cat 8 ethernet cable

Second System
NVA P20, A20, Cubettes, LS3, SSP
Sonore MicroRendu, Topping E30 MCRU PSs, Audioquest Carbon USB cable & JB

Headphones
Grado SR325e/Chord Mojo, Beyerdynamic Avetho/AQ DF Red

RIP Doc

User avatar
karatestu
Posts: 4982
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Has thanked: 1162 times
Been thanked: 680 times
Great Britain

Re: Speaker placement, reflections, cancellations, modes - making the best of a bad job

Unread post by karatestu »

CN211276 wrote: Mon Oct 18, 2021 3:29 pm
CN211276 wrote: Sat Oct 16, 2021 11:28 pm Out of necessity my speakers need to be close to the wall. I was concerned that the upgrade from Cube 1s to 3s might lead to over blown bass, but as Richard Dunn advised this was not the case. I am content that there are no frequency anomolies. The Sbooster PSs which I connected to my source components not so long ago extended the bass and initially there was a lack of control. After some running in things settled down and definition became spot on. I have found that changes to furniture and rugs
have affected the frequency balance, but not to a great extent. I have been able to compensate by changing the subtle filter settings on the DAC. As well as the frequency balance I am very happy with the sound stage and imaging, optimised by experimenting with the toe in of the Cubes and distance apart.
Image

This is the listening part of the room which is open plan and comprises the length of the down stairs. The right speaker is not close to the side wall and the left speaker is a long way from the patio door, though close to the solid wooden rack. The leather sofa in view with cushions and the rug, with decent underlay, minimise reflections. Nearly all of the rest of the room is uncovered wooden floor. The listening sofa is also leather and higher than the one in view and close to a wall.
Are you going to try the new NVA speakers when they become available Clive ?
These users thanked the author karatestu for the post:
savvypaul (Mon Oct 18, 2021 8:08 pm)
DIY inspired by Richard "The Doc" Dunn RIP

User avatar
CN211276
Posts: 5337
Joined: Tue Aug 09, 2016 9:29 am
Location: Cardiff
Has thanked: 591 times
Been thanked: 420 times
EUROPEAN_UNION

Re: Speaker placement, reflections, cancellations, modes - making the best of a bad job

Unread post by CN211276 »

Will wait and see.
Main System
NVA BMU, P90SA/A80s (latest spec), Cube 1s, TIS, TISC(LS7)
Sonore OpticalRendu, Chord Mscaler & Qutest, Sbooster PSs
Network Acoustics Eno, ifi iPurifier3, Audioquest Jitterbug FMj, Cisco 2940 & 2960
DH Labs ethernet, BNC & USB cables, Farnells cat 8 ethernet cable

Second System
NVA P20, A20, Cubettes, LS3, SSP
Sonore MicroRendu, Topping E30 MCRU PSs, Audioquest Carbon USB cable & JB

Headphones
Grado SR325e/Chord Mojo, Beyerdynamic Avetho/AQ DF Red

RIP Doc

Post Reply