Room Acoustics

[matt49]

I think an awful lot in this thread is complete nonsense.

In all my years in this business I have come across truly awful rooms perhaps, half a dozen times.

The trick, such as it is, is to match the system, primarily the speakers to the room, remember this is your room, you live in it, talk in it, do whatever in it. More importantly, you are used to it, this is important, the sound of your room is your reality, yes other rooms sound different, but it doesnt matter, you listen in your room and that is what counts.

This is not difficult, except for one thing, the modern obsession with 'bass', the requirement seems to be for huge amounts of it, mostly entirely unnconnected with any music being played, being produced by, in the main, ghastly cheap floorstanders that cost about 2 bob.

I still hear such garbage in peoples homes and as an ex-dealer I am sometimes asked 'what do you think'? Mostly I just smile and say 'wonderful'.

It's remarkable that someone with so much experience and knowledge could talk such utter garbage. But I suppose that's what happens if you have an obsession with speakers that don't produce real bass.

The fact is most rooms in the UK will suffer from very obvious bass modes below 80Hz. The science of this is very well known, and no amount of idle hand-waving will change that.

Any sensible person will realize that by fettling the position of the speakers and listening position, or by applying some DSP to the bass, you can get a very good result. But to claim this isn't an issue is plain silly. *kiss3*

Thank you, that was quite deserved.

Even in 'ranting' mode I can normally make my point and explain my views far more clearly and coherently than my earlier post.

Failing totally to make the distinction between what is possible for the enthusiast and the realities of what is acceptable for many music/hi-fi lovers was I think the cardinal sin.

I'm in the middle of a very busy weekend, if the thread is still running when I have the time, I will revisit.

Dave, I'm glad you realized I wasn't being altogether serious.

Unless an EQ system can redirect high frequencies from the driver itself (which it can't), it has to reduce HF exaggeration due to wall reflections without reducing that particular frequency - and then you're fundementally altering the speaker's output, affecting quality. Personally, I'd rather address negative room issues with physical solutions to try and address the major issues.

That's not to say that digital EQ doesn't have its place, as there are instances where physical room solutions just aren't possible.

I'd agree that physical treatments are preferable, though treating bass modes physically is often not practicable. A good general principle is: correct mid-range and HF problems with physical treatments; correct LF problems with DSP.

Why? Because most correction will aim at smoothing off unwanted peaks in a room's response, which generally result from reflections. Physical room treatment aims at preventing the reflections by absorbing (or scattering) soundwaves. For different frequencies, different kinds (and more importantly quantities) of absorbent material are needed, and once you get down to room modes around, say, 60Hz, the thicknesss of absorption required is simply not practicable. (There are other "non-absorbent" ways to treat bass, such as Helmholtz Resonators and other forms of resonating panel designs, but doing this correctly requires a level of expertise well beyond what most of us possess.)

So for most people the only practicable way to treat bass modes will be with DSP. Fortunately there are some simple 'fit and forget' solutions available, e.g. the DSPeaker Anti-Mode.

One important principle to remember is that whilst you can cut off a bass peak using DSP, you shouldn't try to fill a bass null using DSP. Bass nulls arise from cancellation of waves at a particular frequency. Throwing more of that frequency at a room by turning up the bass isn't going to solve the problem, and it may well end up frying your amp.

On the other hand, treating HF reflections physically is relatively easy. It's easy to experiment (hang a duvet on the wall behind the listening position), and it's relatively easy to solve HF problems without turning the room into something that looks like a recording studio.

 

[DocG]

IMO the quantity of relections is less of a problem than the quality. If the reflected sound were in phase with the direct sound, it wouldn't be that much of an issue. Ever experienced room problems when someone is playing a guitar or a recorder, or talking to you? The thing is: most speakers keep their drivers' output in phase within a tiny sweet spot; what reflects off your walls is not is phase by far, hence sounds very unnatural, tiring, irritating, ... So if absorbing/scattering the reflections is not feasible/wanted, a pair of omnidirectional speakers can be a valuable alternative. Unfortunately, the market is not flooded with omnis (to put it mildly).

PS: I'm not talking about bass issues/room modes. That's a different kettle of fish!

 

[DocG]

Another thought: treating a living room with absorbers/diffusors is not socially acceptable most of the time (a suspended ceiling might be the exception here). But trying different positions (within certain limits) for speakers and (IMO most of all) the listening seat is a worthwhile exercise! Acceptable and free!

 

[CJSF]

Mmm . . . I would sugest much of the 'anti' room treatment is that most dont know how? . . . dont know good from bad? . . . or see the fitting and measuring of a room as an issue? Who has actualy made the effort to listen to a treated room v the same room untreated, a real problem, its not like changing over a couple of pairs of speakers and hearing the differeance?

The base problem these days is boaring to me, my system produces plenty for me with in the confines of speaker size, room size and the ability of the system as a whole. My criteria over the 30 years in hifi has always been the base line has to have construction and is tune full, anything outside this one ignores or even tunes out.

In the 80's I was fortunate enough to have the perfect room . . . susequently all my evaluation in those days was spot on IMHO. Since then house moves have not been so kind in music room terms. I went into making the best of a bad job mode, I think average is my best description looking back, cos I did not know what I was missing out on.

Fortunatly I chose my curent system well, despite a poor room sound that I did not know about at the time. about the middle of last year I was thinking and listening feeling very much at a loose end. What about room treatment? A bit of serching soon came up with basic ideas and the simple 'reflection method' of determaning where to place panells as a starter.

When you dont know what you are doing, the investment of hundreds of pounds is dificult to justify and then to screw onto wall blind . . . not a good idea.

With a mirror and the reserch information, I worked out where to place panells but I had not got any. I'm a boddger of the first order when it comes to proving a point. I eventualy came up with a couple of large blankets folded in four, creating two panells 110cm x 90cm, these were fixed to a couple of pairs of 2m bamboo canes. Proped against the wall, thes blankets transformed my room, removing one alowed me to hear the echo on the other wall, a little adjustment from the mirror position and all was well.

It cost me nothing to prove the point, did not even take much time to do. I have not replaced my boddge for propper panells yet, I procrastinate a lot these days, a personal issue I have to cope with. I'm sure a profesional would laugh at my efforts but it has don a temporary job and proved to me dont pohoo anything you dont understand bfor trying it.

By the way, I was able to test my room 'with and without', it was like swaping a pair of speakers over . . . *acute*

CJSF

 

[iQ Speakers]

Could i sugest people post room sizes and the speaker they own along with or without room problem.

PMC DB1i across the room. No problem. IPL Acoustics M1TLm (5" driver, ribbon tweeter small floorstander) across the room No problem.

I think you would see a pattern emerge of over done speaker choice causing problems.

 

[matt49]

Could i sugest people post room sizes and the speaker they own along with or without room problem.

PMC DB1i across the room. No problem. IPL Acoustics M1TLm (5" driver, ribbon tweeter small floorstander) across the room No problem.

I think you would see a pattern emerge of over done speaker choice causing problems.

Nice idea.

Speakers: Martin Logan Montis (i.e. electrostatic line-source panels 23kHz-340Hz and 10" active electrodynamic woofers 340Hz-29Hz, with bass adjustment +/-10dB). I have the bass adjustment set on 0dB. The speakers stand on Townshend Isolation Bars which remove almost all of the resonance between the speakers and the floor.

Room: 5.25m x 5.25m, including a bay window.

Speaker position: centred on wall 2.75m apart, and 0.75m away from front wall.

Listening position: 1.5m from rear wall. From the listening position, the bay window is to the right and to the left is a 2.5m-wide opening through to another room. (The opening is sometimes shut with sliding doors.)

Acoustic 'problems': (1) 6dB 'spikes' at 30Hz and 60Hz (measured using DSPeaker Anti-Mode). These are the main LF room modes, and the bass here is both loud and resonant. (2) general feeling of excessively lively top end, with a bit of slap echo. I haven't measured this; I'm just comparing from memory how the same system sounds in my study upstairs.

Other room features: bare sprung wood floors, two leather sofas and leather ottoman, bare walls. There's nothing alse in the room at all: no other furniture, bookshelves etc.

Treatments: (1) Using the automatic LF correction in the DSPeaker Anti-Mode, the LF spikes have gone, and the bass response is pretty smooth down to 25Hz. (2) We're in the process of having the room refurnished: should be done in about 2 months. This includes: very large thick rug covering most of the floor; textured wallpaper; replace leather-covered furniture with fabric covers; large acoustic 'art' panel on wall behind listening position. I'm hoping that these measures will soften the acoustic.

 

[iQ Speakers]

Could i sugest people post room sizes and the speaker they own along with or without room problem.

Nice idea.

Apart from weirdo's like you! *wink*

 

[TrevC]

A badly tuned Ferrari is not a bad car, just badly tuned. No matter how well you tune a standard Robin Reliant, it will still be s***.

agreed, so then what Hifi is in Robin Reliant territory?

Or Matiz Chevrolet. The worst car I have ever driven. The C5 Sinclair must be worse though.

 

[steve_1979]

Room: Irregular shaped 7m x 5.5 x 4.5m

Speakers: AVI DM5 plus AVI subwoofer.

Generally no big problems. The room is a bit bright with too many large flat surfaces but this is not an issuse from my listening position which is near field from 1.5m away. There are a few peaks and troughs in the low frequencies depending on where in the room you listen from but again nothing too major and from my listening position the bass is just right apart from a pretty major dip at about 40-50Hz.

The DM5 also sound good no matter where in the room they are placed. Whether on stands in a well placed position, near or far away from a wall/corner or even just plonked on a cardboard box in the middle of the room.

 

[dim_span]

many years ago, I worked as a design engineer for a company in South Africa that designed conference rooms/auditoriums etc including the installion of all furnishings and decor

we had a team of guys who sorted out the room acoustics after the furniture and decor was installed

amazing differences and it makes a huge difference

 

[CnoEvil]

A badly tuned Ferrari is not a bad car, just badly tuned. No matter how well you tune a standard Robin Reliant, it will still be s***.

agreed, so then what Hifi is in Robin Reliant territory?

Or Matiz Chevrolet. The worst car I have ever driven. The C5 Sinclair must be worse though.

The Trabant must be there, or there abouts.

 

[iQ Speakers]

Room: Irregular shaped 7m x 5.5 x 4.5m

Speakers: AVI DM5 plus AVI subwoofer.

Generally no big problems. The room is a bit bright with too many large flat surfaces but this is not an issuse from my listening position which is near field from 1.5m away. There are a few peaks and troughs in the low frequencies depending on where in the room you listen from but again nothing too major and from my listening position the bass is just right apart from a pretty major dip at about 40-50Hz.

The DM5 also sound good no matter where in the room they are placed. Whether on stands in a well placed position, near or far away from a wall/corner or even just plonked on a cardboard box in the middle of the room.

so Steve has smallish speakers in a large room, No problems and he can turn the bass down if he did.

 

[matt49]

Room: Irregular shaped 7m x 5.5 x 4.5m

Speakers: AVI DM5 plus AVI subwoofer.

Generally no big problems. The room is a bit bright with too many large flat surfaces but this is not an issuse from my listening position which is near field from 1.5m away. There are a few peaks and troughs in the low frequencies depending on where in the room you listen from but again nothing too major and from my listening position the bass is just right apart from a pretty major dip at about 40-50Hz.

The DM5 also sound good no matter where in the room they are placed. Whether on stands in a well placed position, near or far away from a wall/corner or even just plonked on a cardboard box in the middle of the room.

so Steve has smallish speakers in a large room, No problems and he can turn the bass down if he did.

For listening nearfield in a big room it looks like a great system. I suspect the bass response would be more even if there were more than one sub.

 

[matt49]

Could i sugest people post room sizes and the speaker they own along with or without room problem.

Nice idea.

Apart from weirdo's like you! *wink*

It's a fair cop, guv. *crazy*

 

[steve_1979]

Room: Irregular shaped 7m x 5.5 x 4.5m

Speakers: AVI DM5 plus AVI subwoofer.

Generally no big problems. The room is a bit bright with too many large flat surfaces but this is not an issuse from my listening position which is near field from 1.5m away. There are a few peaks and troughs in the low frequencies depending on where in the room you listen from but again nothing too major and from my listening position the bass is just right apart from a pretty major dip at about 40-50Hz.

The DM5 also sound good no matter where in the room they are placed. Whether on stands in a well placed position, near or far away from a wall/corner or even just plonked on a cardboard box in the middle of the room.

so Steve has smallish speakers in a large room, No problems and he can turn the bass down if he did.

For listening nearfield in a big room it looks like a great system. I suspect the bass response would be more even if there were more than one sub.

Thanks. I'm very pleased with it (boardering on addicted to it)

If I could be bothered to move the room around I could probably find a better position for the sub but as it is it's placement is determined by the rest of the room layout. A second sub or maybe even moving it to another position would probably fix the 40-50Hz dip but it's not really an issue as it isn't noticable when listening to music and films. It's only noticable when using a sine wave sweep. Most music doesn't have much or any output below 50Hz anyway.

I might give an antimode DSP gadget a try on the subwoofer at some point to see if it makes a worthwhile difference. I doubt it will though as I have the DM5 set to full range and the subwoofer playing at very low volume to fill out the existing DM5 bass rather than having the DM5's set to small with all the bass going to the subwoofer.

 

[davedotco]

Well the thread is still rumbling on, so here goes.

For the enthusiast with a good system, a decent size room and the flexibility to set up correctly, there is absolutely no doubt the room 'treatment', be it specialsed acoustic modification or simply moving the furniture around can make a great difference. Even just optimising speaker placement and the listening position will make a help tremendously, this is so obvious that I didn't even mention this in my earlier post.

My concern, my rant, really concerns the ordinary enthusiast, one who lives in a multipurpose living room and a situation where, moving a sofa to ensure an optimum listening position, is out of the question, and the opportunity to move the speakers a couple of feet out from the wall is non-existent.

In such situations, in my experience easily the most common, the only practical solution is matching speaker to room. Mostly this means using a smaller speaker, whose more modest bass performance, augmented by a little room gain, will give a very acceptable performance an most music, most of the time.

Steves DM5 system are a good example of this, on a lot of music the subwoofer will make a minimal contribution, the basic balance of the diminutive 5 inch two way is, in a smallish room, capable of being convincing enough to be very enjoyable. The fact that the low bass output is quite modest is a huge advantage here, room modes are barely excited but for various reasons, deep bass is often not missed by the listener.

Good small speakers, be they active or passive, will often sound far more convincing in the bass than is expected, and in many cases are a far better bet for situations that are less than optimal, exactly the reverse of so many of the cheap floorstanders that simple boom and woofle in such situations.

 

[iQ Speakers]

I don't know how to break it to you Dave, but I think that's exactly what we have been saying, so on this occasion your rant was completely superfluous.

 

[ellisdj]

Room: Irregular shaped 7m x 5.5 x 4.5m

Speakers: AVI DM5 plus AVI subwoofer.

Generally no big problems. The room is a bit bright with too many large flat surfaces but this is not an issuse from my listening position which is near field from 1.5m away. There are a few peaks and troughs in the low frequencies depending on where in the room you listen from but again nothing too major and from my listening position the bass is just right apart from a pretty major dip at about 40-50Hz.

The DM5 also sound good no matter where in the room they are placed. Whether on stands in a well placed position, near or far away from a wall/corner or even just plonked on a cardboard box in the middle of the room.

Thats great feedback - 40 - 50hz dip seems pretty common. I have a peak bigger than eifel tower at 68hz is a real bugga because of my room - unlistenable

What about the decay? Have you measured the decay time of your bass and how even is it?

This is the same for the rest but measured via RT60 (only way I know whats what) - what RT60 time and how even is it?

This is an interesting and helpful article for anyone looking at things more deeply

 

[MakkaPakka]

Could i sugest people post room sizes and the speaker they own along with or without room problem.

Most people don't know they have a problem with the exception of maybe slap echo. They'll get used to the sound and tell themslves it sounds good and it probably does sound good compared to what they'd otherwise be listening to music on. It's only when you start measuring or experimenting with treatment that you realise you have problems.

 

[davedotco]

I don't know how to break it to you Dave, but I think that's exactly what we have been saying, so on this occasion your rant was completely superfluous.

Yeah, I know, I was in a bit of a strop.

However the real point I was trying to make is that any kind of room treatment is quite out of the question for an awful lot of people, in many cases even elementary matters of speaker and listener position are not addressed.

I don't get into as many peoples homes as when I was a dealer, but I am still asked as an 'expert' (sic) to offer opinions or to sort out issues with peoples systems. Current hi-fi marketing trends really do not help and decent advice from a dealer seems remarkably absent.

The result being that many of the setups I see are hopelessly unsuited to the room and, just as importantly, the limitations of setup and positioning. The main problem here remains excessive bass, bass sells and speakers, particularly in the budget/mid-fi sector of the market are designed to deliver lots of it, whether on the recording or not seems not to matter.

 

[ID.]

However the real point I was trying to make is that any kind of room treatment is quite out of the question for an awful lot of people, in many cases even elementary matters of speaker and listener position are not addressed.

Bingo.

Room treatments out of the question and very little flexibility for placement. Pretty much the boat I'm in. Tiny living room (4 x 5m) open on one side to the kitchen. Uneven ceiling. Interesting bass dips and peaks all over the place. At least most of my issues are bass related so the smaller speakers or smaller speakers + sub is a doable solution.

Was looking at moving, but for various reasons we are staying put for a few more years at least.

 

[davedotco]

However the real point I was trying to make is that any kind of room treatment is quite out of the question for an awful lot of people, in many cases even elementary matters of speaker and listener position are not addressed.

Bingo.

Room treatments out of the question and very little flexibility for placement. Pretty much the boat I'm in. Tiny living room (4 x 5m) open on one side to the kitchen. Uneven ceiling. Interesting bass dips and peaks all over the place. At least most of my issues are bass related so the smaller speakers or smaller speakers + sub is a doable solution.

Was looking at moving, but for various reasons we are staying put for a few more years at least.

The other possible advantage of smaller speakers is that you can often listen quite close, the integration is good enough and a nearfield position can help tremendously by reducing volume levels and minimising room effects.

I had a situation where, for normal everyday listening I would sit on the sofa in a less than ideal position, but could, by moving a chair into the optimum position get much better performance listening in the near field. Practical and reasonably acceptable to everyone involved.

 

[sheggs]

I was away this weekend so didn't see this thread so won't go over what has already been said. But for those interested I will be at the Bristol Show next month (for the first time) in Room 322 with Heed Audio with our GIK Acoustics products. So if you have not had the opportunity before pop in see the products and what they can do and have a chat about room acoustics in general

 

[Covenanter]

Surely everywhere you listen to music has acoustic limitations! I'm old enough to remember The Albert Hall before they put the mushrooms in the roof and there was a definite echo. However I don't remember not enjoying the concerts. Yes modern concert halls are better, Symphony Hall here in Birmingham and The Anvil in Basingstoke being particularly good IMO, but I still enjoy music in less acoustically well designed spaces. The Old Town Hall here in Birmingham is just a big cube with solid walls but I've heard great concerts there.

I can't hear any echoes in my apartment and neither have I noticed any peaks and troughs at specific frequencies. That may be because my old ears aren't sensitive enough but I live here and I want my apartment to be aesthetically pleasing to the eye. It also has to be practical so my lounge is my living room, my dining room, my study, and my library as well as my music room. As it happens my taste is for hard surfaces, wood, metal and glass and I'm not going to embrace soft fabrics.

So I won't be measuring the frequency response of my room because it sounds fine to me as it is. Neither will I be installing acoustic panels and the like. Which is not to discourage others who feel the need to do so. If it sounds bad to you then you must do whatever you need to do to make it sound better. Each to his or her own!

Chris

 

[MajorFubar]

Good few points made in this thread. Room acoustics play a massive part in the perception of the sound of your HiFi. However unless you're building a home recording studio with a very big budget, for many of us it's going to be a balancing-act between cost, practicality and domestic acceptability. Simple improvements can be accomplished cheaply or at no cost: rugs, decent carpets, thick curtains, common sense placing of furniture, speakers and reflecting items. You want a cheap change? Try moving your seating position forward or back by as little as 6". You'll be amazed. The room size also plays a massive part as well, particularly with bass frequencies, and unfortunately that's often unchangeable. Many people are sitting in a room where the distance from the speaker to the wall it faces isn't even long enough to accomodate one cycle of a 60Hz sinewave, let alone anything lower.