Bass - how much is too much?

If you can borrow/demo a Dspeaker Anti-mode 2 it's worth a try. A very good piece of kit designed specifically for the problems you seem to be having

Huge posted:

Filipe,

The pressure levels of the standing waves will be greatest neat the walls, the particle velocity of those same waves will be greatest in the centre of the room.  This is the normal interplay between potential energy (as pressure) and kinetic energy (as particle movement) that constitutes a longitudinal standing wave.

Indeed boominess tends to be because of poor speaker/room coupling... nothing if any to do with electronics other than wide band good quality electronics can show up the poor coupling more

DC71 posted:

If you can borrow/demo a Dspeaker Anti-mode 2 it's worth a try. A very good piece of kit designed specifically for the problems you seem to be having

It's primarily designed to work with the low level interface to a sub, I have no idea how well it'll work with main speakers.  Also the cabling to fit it between the flatcap and the 155 will be "interesting" - it would be a custom job and and not something one would be able to borrow.

Being a long standing ATC fan and customer, I say the ATC 11s are best away from the wall, think about 30 upto 50 cms, yes the bass will tighten and lean everso slightly, but the speed increases and the presentation will be dynamic, punchy, more accurate  and time well. Get the ATCs too close, and the bass gets slightly more prominent, but the dynamic, timing and punch gets sat upon, kind of undermining some of the key attributes of the ATC infinite baffle designs.

Hi Simon,

Yes I agree, but for many other speakers, the effects are even worse - all those you mention and a shed load of problems with peaks and troughs the bass in addition!

(btw 30cm is far too close to a wall for almost any ported speaker, front ported reflex, bottom ported reflex, rear ported reflex or open transmission line, they all share the same problems, and only a few are truly happy 50cm from a wall.)

Huge posted:

jon honeyball posted:

I'd put SCM11s on the right hand wall, either side of the window

I'd agree with the ATC SCM11, and agree with starting with them by the window, but I'd also try them where the current speakers are, to see which arrangement is better.  The SCM11s will be happier close to a wall than the Neats are (note that they'll still be better with some distance behind them, but if you can't give them that, the the effect will be much less detrimental than it is with the Neats.

Note that there are also some other small speakers that will work well (and some that won't), but few of these have as good an overall performance as good as the ATC SCM7 and ATC SCM11, unless you spend a lot of dosh (Wilson Bensch Duette anyone? - N.B. I'm not suggesting them - way to expensive and way too tough a load for you other equipment!).

I meant correctly positioned there. I.e. A 90 degree rotate of the room. Not on the wall a la Kan

Huge posted:

(btw 30cm is far too close to a wall for almost any ported speaker, front ported reflex, bottom ported reflex, rear ported reflex or open transmission line, they all share the same problems, and only a few are truly happy 50cm from a wall.)

I'm sure you are right, which is one of the nice flexibility aspects of the ATC infinite baffle designs.. However I did audition a pair Russel K 100 (front reflex ported) at home and they were quite happy around 30cms from the back wall... but they seem to be quite interesting designs where the case is very much un damped... but then a pair of Harbeth C7s I onece owned I felt they would need to be a mile from the wall before they would fully tighten 

With speaker designs where there is a port (reflex or TL), provided it is on the front the performance with respect to rear wall has nothing to do with the port, as the sound is radiated in much the same manner as that directly from a driver (only 'much the same' as it will vary depending on the design of the port itself and design of the driver). What can influence that behaviour is the dimensions of the front baffle, so an IB and a front ported enclosure having identical dimensions, with identical frequency response, are unlikely to behave any differently with respect to rear wall.

Regardless, if the bottom end of the frequency response of one speaker rolls off more than another, typically as would an IB design vs a ported design, then the boost to bass arising from the speaker boundary interference response (SBIR, commonly known as proximity effect) will tend make the full range design bass heavy, and the curtailed bass design less curtailed.

Coming back to the specific situation, as Huge and I have suggested, testing with REW can help hugely (sorry Huge!) - if you have a computer, all you need is an inexpensive measuring microphone and a cable (cheapo budget one is fine) to go from the computer's audio output to your amp. With that you can see exactly what is going on, and can move the microphone around to see what is happening in different places, and from that assess placement better, and decide whether treatment is needed, etc. 

meanwhile as someone suggested, unusual speaker positions can sometimes work well regardless of all convention, so don't be afraid to try anywhere that one is towards your left and the other towards yourvright from any possible listening position. 

I don't agree reflex ports & close to a rear wall don't work,  its probably true for most/all commercial designs as they go for maximum bass & a close wall blows that to levels of 6dB or more the its design intent.   To work correctly against/close to a wall a speaker needs to have a slow roll off starting from around 200Hz,  typical of the response of an IB.      A reflex speaker (cab & driver) & its port can be tuned to work like this,  thats how I've designed mine,  it gives a result between the extended bass/sharp cut off of a reflex & the slow roll off of an IB.   It gets into overblown bass at higher than the SPL's I normally use,  but at 80dB measured 1/3 oct white noise in-room is ~flat down to port & driver fs at 30Hz.

Mike-B posted:

It gets into overblown bass at higher than the SPL's I normally use,  but at 80dB measured 1/3 oct white noise in-room is ~flat down to port & driver fs at 30Hz.

I'm puzzled how overblown bass (suggesting disproportionate to the rest of the spectrum) can occur like that, meaning that the frequency response is changing with sound level. Whilst the relative sensitivity of human hearing does reduce at the frequency extremities as sound level falls, there isn't a lot of difference in relative sensitivity at the bass end compared to the rest of the spectrum going from, say, 80 to 100 dB. And the magnitudes of peaks of standing waves are directly proportional to the excitation energy, so would be expected to be simply louder in proportion, not suddenly starting to resonate if they weren't before.

Are you saying that you measure a change in frequency spectrum going much above 80dB, or simply that it sounds overblown to you? 

Have you measured decay times?

Adam Zielinski posted:

[@mention:2833539978796882]

An idea to help you with identifying booming spots in your room: I noticed you have some guitars around.  
Do you have a bass-guitar playing friend who has a good bass-combo?
Get him over into your lounge and get him to play all the notes in a chromatic scale of E, starting with open E, and progress through two octaves.
Experiment with placing the amp in various locations (starting with where you have your speakers).

You will quickly realise where problem areas are and at what frequencies you get dull / out of control bass.

An altenative is to use the measurement tools Huge has recommended.

Thanks Adam I will get the bass player from my band to try this. Will also check out REW software. 

Can anyone describe the characteristics of the ATC speakers I like the idea of these 

I have also taken a good look at system pics and there are quite a few full range speakers in maybe not perfect rooms I can't be the only one with some excess bass on some albums??!!! Maybe I'm being too fussy. 

BTW, REW can be used to generate a tone that you can sweep through the frequency range listening for peaks and troughs in sound level, so even without a microphone it can be used to make a more objective assessment of what is going on that listening to music or discrete notes from a guitar. A cable to connect computer to amp shouldn't cost more than about £10, depending on length, available from multitudinous AV and electronics stockists (e.g. Maplin).

There are plenty of other programs that can do the same, I'm just suggesting REW because it is one I'm familiar with, is free, and is very useful if you do ever add a microphone. 

 I am no expert when it comes to room acoustics. The amroc site I referenced does some calculations based on various theories concerning what makes a good listening room and the positions within the idealised room that may be better. Going to the amroc room calculator page which is found by googling "bolt area acoustics" along with tutorials from the University of Salford and an article by nickcreative2 on Wordpress. The Bolt Area displayed by the amroc calculator seems to be an area where there is a good distribution of the modal frequencies of the room. The calculator also plots the modes as a Bonello plot showing how the number of modes increase up the musical scale. A monotonic increase with frequency is deemed a good listening environment.

The music can be lost if the room, speaker positions and listening positions are poor. If the balance of the music (amplitudes of the various frequencies of the music is different from the mix in the recording), then we may be persuaded that bass is booming or something when it could be a loss of other frequencies. The Bolt area seems to be the area where the room sustains a good balance. I think this kind of description is better than bass being trapped in certain areas.

Filipe posted:

 

The music can be lost if the room, speaker positions and listening positions are poor. If the balance of the music (amplitudes of the various frequencies of the music is different from the mix in the recording), then we may be persuaded that bass is booming or something when it could be a loss of other frequencies. The Bolt area seems to be the area where the room sustains a good balance. I think this kind of description is better than bass being trapped in certain areas.

Yes, bass is not actually trapped - or "bass traps" wouldn't need to be added! It is commonly said to "build up" in corners, however another way to visualise what is happening with that sketch that was posted with the red shading is that bass pressure is higher at the walls, or rather solid boundaries, and corners are the junctions of two, and in some places three, boundaries, so have additive effect. With the highest pressure in the corners, especially at junctions of two walls with floor or ceiling, those are most effective places to put things that absorb bass frequencies (so-called 'bass traps') - not that that is always possible or acceptible in a domestic situation.

That relates to sound pressure (correlating to sound level) resulting from the speaker, and thus equates to what the listener will hear in different places (though aside from that there will be peaks and troughs for different frequencies in different places all around the room due to standing waves). Where the speaker is positioned is a bit like that but in reverse, so if placed in a corner they will produce more bass elsewhere in the room than by a waall, and by a wall more than out in the free air away from the wall. And proximity to floor and ceiling also, but in most cases the distance from floor is set in the design stage by the height of the speaker or speaker and stand and varies little in practice, while the ceiling is generally quite some distance away.

An explanation of what is happening with the walls and corners around the speakers requires consideration of the fact that bass frequencies, are far less directional than high frequencies: to all intents and purposes the lowest frequencies can be considered not to be directional and so to radiate spherically from the source, so that if the speaker was in open space suspended high above the ground (or in a chamber with all surrounding boundaries fully absorbing incident sound) they radiate approximately evenly into an entire sphere. Placed on a hard floor but otherwise in open space and they radiate into half a sphere - i.e. the sound that would go down is immediately bounced back up, reinforcing the sound and so doubling the sound level. Add a wall immediately behing the speaker and radiation would be into 1/4 of a sphere, so doubled again. Etc. Compared to this, high frequencies radiate direct at you, and effectively not backwards, up, down, or to the sides, so they are unaffected by proximity of floor and walls, so remain at the same sound level in each setting. And gradually between the lowest bass and highest treble the directionality changes between the two extremes, meaning that the effect of the walls and floor varies with frequency. In a real life situation it is considerably complicated by reflections from surfaces that are varying distances from the speakers in all directions, and by the different degrees of absorbance and reflectivity of different materials at different frequencies, and by standing waves, but the effect is there.

Some speakers are designed to be placed in corners (the classic rear loaded folded horn designs are a good example, where you can picture that the corner effectively extends the mouth of the horn). Others are designed for back-to-wall or even in-wall (these avoid baffle step effects), and the majority for somewhere more within the room. But all will be affected by other aspects of the room, and that is always the difficulty, because rooms vary so much.

However, ignoring all the technical mumbo jumbo, the most important thing is whether it sounds good to the listener. If that is achieved simply by playing with positioning then fantastic. If proving difficult, sof****e can go a long way to helping find the solution. And consideration of physical treatment like reducing early reflections from side walls, floor and ceiling can make a big difference to clarity (especially side walls if they are close, as when 'firing down' the room, while bass traps in some corners might help a little. And if after that there are still significant peaks in response then DSP software of whatever description might be appropriate to consider.

IB's explanation is good and fairly comprehensive, but to add a little on the comparison between bass as against mid and high frequencies.

The position of the speakers to get the most natural sounding response in the critical frequency range for voice and instrumental timbres ia often not the best position for bass response.  This gives two options...

1  Us "full range" speakers and accept a compromise throughout the frequency range (hopefully a balanced compromise). 
2  Use a satellite / sub arrangement separate the bass from the other frequency ranges so that the position of the main speakers can be optimised for mid and high frequencies and the position of the sub optimised for bass frequencies (but then you have to accept a more complex setup task)

In the latter solution DSP software can be used to tailor the bass response to the room acoustics without compromising the quality of the signal in the  critical frequency range for voice and instrumental timbres - the best of both worlds.

Innocent Bystander posted:

Mike-B posted:

It gets into overblown bass at higher than the SPL's I normally use,  but at 80dB measured 1/3 oct white noise in-room is ~flat down to port & driver fs at 30Hz.

I'm puzzled how overblown bass (suggesting disproportionate to the rest of the spectrum) can occur like that, 

Are you saying that you measure a change in frequency spectrum going much above 80dB, or simply that it sounds overblown to you? 

I measure my system to be flat & I normally set the volume at 80dB-C as thats what perfer as maximum when listening.  By overblown I'm talking about the human audio response curve,  it means the perceived speaker response begins to slowly sound overblown to me,  but thats a generalisation.  Its very recorded material dependant,  a string quartet with not much going on below 50Hz can be listened to at high volume but follow that with a rock band & thats pumping sub-bass & I'm reaching for volume control.  

stuart posted:

Hungryhalibut posted:

In my view, with a 152/155 and Motive 2s, the speakers are the last thing you should be thinking of changing. 

I take your point HH. I have tried SN2 and 202/200 but can't seem to tame the upper frequencies with amp changes so far. This seems to be my major issue so I guess this leaves room treatments or speaker change. 

Have you experimented with different interconnect cables? I used to own AR Lunar, which worked great between nDAC and SN2 but in the end sounded little soft and flat. Then tried HiLine, which was super detailed but at the same time very sibilant and harsh sounding, it made my system unlistenable. 15 minutes and I had listening fatigue. Finally I settled with TQ Black which offer best of both worlds. It's not too aggressive sounding but still extracts impressive amount of detail out of the recordings. With interconnects it's easy to fine tune the sound and tame annoying treble. Source plays a big role here also. IMO amplifier has least to do with sibilant highs. 

stuart posted:

Adam Zielinski posted:

[@mention:2833539978796882]

An idea to help you with identifying booming spots in your room: I noticed you have some guitars around.  
Do you have a bass-guitar playing friend who has a good bass-combo?
Get him over into your lounge and get him to play all the notes in a chromatic scale of E, starting with open E, and progress through two octaves.
Experiment with placing the amp in various locations (starting with where you have your speakers).

You will quickly realise where problem areas are and at what frequencies you get dull / out of control bass.

An altenative is to use the measurement tools Huge has recommended.

Thanks Adam I will get the bass player from my band to try this. Will also check out REW software. 

Can anyone describe the characteristics of the ATC speakers I like the idea of these 

I have also taken a good look at system pics and there are quite a few full range speakers in maybe not perfect rooms I can't be the only one with some excess bass on some albums??!!! Maybe I'm being too fussy. 

I would describe atc as honest to the source, adds very little, takes away very little. They have a refined top end that is detailed yet forgiving, not hyped. The mids sound very real, with piano and vocals you get the impression they are there with u. Good depth and soundstaging, very three dimentional. Bass is tight with slow roll off, again not hyped and well balanced. Ive only evr listened to scm19 and 40s - 40 clearly superior right across the spectrum but you need a room that can take suprising amount of bass energy.

im sure its very common for people to have mismatched room/speakers if it doesnt bother you then its not an issue.

Acoustics is a very complex subject. I have Sopra N2 which I am very happy with. The advice Focal provides is below. Most other speaker manufacturers do not seem to give much advice which seems a shame. I'd find it useful to know whether others find these rules work. You might like to read the user guide from the Focal site yourself.

Positioning

These loudspeakers have been designed to deliver the most faithful reproduction of all kinds of music or home cinema programmes. Nonetheless, we recommend following these simple rules to optimise their performance and to guarantee good tonal balance and a realistic sound image. The loudspeakers should be positioned symmetrically, facing the listening area, ideally forming an equilateral triangle with it. However, these distances may be adjusted to find the ideal compromise according to the design of your interior (fig. B). The loudspeakers should be positioned at the same height, in the same horizontal plane. Ideally, the tweeter should be positioned at the same height as the listener’s ears in the usual listening position (fig. C). Do not position your loudspeakers too close to a corner of the room and do not place them too close to a wall. This will induce some unwanted room resonance and artificially increase bass response. On the other hand, if the bass level is considered to be insufficient, you could try moving the loudspeakers nearer a wall to re-balance the bass level (fig. E).

Optimisation

For perfectionists, here is a formula for optimal positioning: If A is the distance from the centre of the woofer to the nearest floor or wall, B is the distance to the next closest floor or wall, and C is the greatest distance (A < B < C), the equation B**2 = AC defines the ideal loudspeaker position.

Example:

If the centre of the woofer is 20” (50cm) away from the rear wall (A) and 24” (60cm) above the floor (B), then the side wall will be ideally 28” (72cm) away [C = B2 ⁄ A = 28” (72cm)] (fig. D).

Recommendations for use

The behaviour of the loudspeakers depends on the acoustics of the listening room, on the correct positioning of the loudspeakers within the room, and on the position of the listener. It is possible to tweak each of these parameters to obtain or improve a desired effect.

Stereo perception is imprecise and poorly centred: try moving the loudspeakers closer together and/or have them facing the listening point.

The sound is harsh, aggressive: the acoustics of your listening room are probably too reverberant. Consider using sound-absorbing materials (carpets, upholstered furniture, tapestries, curtains, etc.) and sound-reflecting materials (furniture) to absorb or diffuse resonance.

The sound is “flat”, strangled: there are too many sound-absorbing materials in the room, the sound is soaked up, it has no relief. Look for the best compromise between sound-absorbing and sound-reflecting materials in your room. In general, aim to have a reflective wall behind the loudspeakers for the sound to develop correctly. The wall behind the listening area, on the other hand, should ideally be sound-absorbing to avoid rear reflections “contaminating” the stereo image.

Furniture can be strategically placed near the side walls of the room to diffuse sound waves and ensure certain frequency ranges are not excited, particularly in the midrange (suppression of flutter echoes). 

The advice from Focal seems to conflict with some given on this forum. However, the Focal advice seems comprehensive. I can see that other makes using isobaric techniques (Neat) or internal chambers (PMC) may introduce additional constraints. I'm certainly glad not to have hard floors, and that our lounge has lots of windows with curtains. I did not like the Neat Ultimatum stand mounted speaker by comparison with the Sopra 2. Doesn't seem worth trying to make the speaker fit the room beyond the advice Focal provide - best to keep trying others until you find the one.

Based on the Focal advice I think the OP's room should be reasonably ok apart from the hard surface behind the listening positions.

By comparison to using REW the advice from Focal is quite superficial, and even REW's room simulation dialogue alone provides more information.

Furthermore the advice on using an absorber behind the listening position is useless without pointing out that this needs to be at least 110mm thick to deal with sound at 1kHz.

I looked at REW help info - very impressive plots. It made me feel amazed that the music I listen to actually comes out anything like the stuff that was recorded in the studio. Acoustics is a very complex science. However, as far as my quick read of the help info went it didn't give any advice on how setup a room from all the measurements it can take.

REW Help Contents
Welcome
Getting Started
Signals and Measurements
REW Overview
Calibrating the Soundcard
Checking Levels
Calibrating the SPL Reading
Making Measurements
Impedance Measurement
Thiele-Small Parameters
Measurements Panel
Impulse Responses
Minimum Phase
The limits of EQ
SPL Meter
Signal Generator
Level Meters
Graph Panel
SPL and Phase Graph
All SPL Graph
Distortion Graph
Impulse Graph
Filtered IR Graph
Group Delay Graph
RT60 Graph
Spectral Decay Graph
Waterfall Graph
Spectrogram Graph
Oscilloscope Graph
Overlays Window
RTA Window
EQ window
EQ Filters Panel
Equaliser Selection
Room Simulation
Importing Measurement Data
Communicating with AV32R DP or AV192R
Communicating with the BFD Pro
Soundcard Preferences
Mic/Meter Preferences
Comms Preferences
House Curve Preferences
Analysis Preferences
Equaliser Preferences
View Preferences
Keyboard Shortcuts
File menu
Tools menu
Preferences menu
Graph menu
Help menu
SB Live! USB 24-Bit External Setup

Linn Space optimisation does appear to work, however, it is nothing more than an electronic 'graphic equaliser' (remember those from the late 1970's?) It takes into account the specification of your speaker, placement, and your room dimensions. 

To use REW.

1)   Use the Room Simulation to find candidate positions for your speakers, sub and listening position.

2)   Setup the room according to one of the candidate configurations.

3)   Look at the minimum phase plot - if there's a discontinuity here then any defect in this area (particularly nulls) can't be fixed.

4)   Look at the impulse response.  From the timing of 'echo' signals, you can work out the distance to reflection points.  Put absorbers or diffusers at these locations.

5)   Look at the frequency response waterfall plot for low frequency peaks that have slow decay, these need bass traps to absorb the excess energy.

6)   Adjust the system.

Repeat the measurement and plots to check your results.  When you're happy, stop; Else GoTo step 2.

Filipe posted:

I looked at REW help info - very impressive plots. It made me feel amazed that the music I listen to actually comes out anything like the stuff that was recorded in the studio. Acoustics is a very complex science. However, as far as my quick read of the help info went it didn't give any advice on how setup a room from all the measurements it can take.

There is no magic formula if that's what you expected, because every room/speaker combination is different. What it does do is simplify assessment by providing an objective and full range means of seeing just what is happening in the room.

Essentially for  speaker placement, you play around with speaker positions measuring at the listeneing position, and vice versa - so quite a bit of iteration between the two, but objective unlike your ears, and can scan the full frequency spectrum, so you can find the best positions within whatever is available to you for possible positions. (Re the listening position, you can just walk around with the microphone trying different positions.)

From the chars you can assess decay time and early reflections, helping identify where whatbtype of treatment would help most, or assessing the effect of putting anything in place.

Filipe posted:

 

Positioning

These loudspeakers have been designed to deliver the most faithful reproduction of all kinds of music or home cinema programmes. Nonetheless, we recommend following these simple rules to optimise their performance and to guarantee good tonal balance and a realistic sound image. The loudspeakers should be positioned symmetrically, facing the listening area, ideally forming an equilateral triangle with it. However, these distances may be adjusted to find the ideal compromise according to the design of your interior (fig. B). The loudspeakers should be positioned at the same height, in the same horizontal plane. Ideally, the tweeter should be positioned at the same height as the listener’s ears in the usual listening position (fig. C). Do not position your loudspeakers too close to a corner of the room and do not place them too close to a wall. This will induce some unwanted room resonance and artificially increase bass response. On the other hand, if the bass level is considered to be insufficient, you could try moving the loudspeakers nearer a wall to re-balance the bass level (fig. E).

Optimisation

For perfectionists, here is a formula for optimal positioning: If A is the distance from the centre of the woofer to the nearest floor or wall, B is the distance to the next closest floor or wall, and C is the greatest distance (A < B < C), the equation B**2 = AC defines the ideal loudspeaker position.

Example:

If the centre of the woofer is 20” (50cm) away from the rear wall (A) and 24” (60cm) above the floor (B), then the side wall will be ideally 28” (72cm) away [C = B2 ⁄ A = 28” (72cm)] (fig. D).

 

 

 

These guidelines won't fit all rooms and situations.

Firstly, they don't address odd-shaped rooms,  like the OP's, and secondly even with plain rectangular rooms they only make sense for some rooms: for example, tKe a room 20ft by 13ft: If  firing across the room, the recommended speaker position for the example given would place the speaker baffle centres 15'4" apart, and the back of listener's ears at the furthest possible distance with head right against the back wall (not an ideal place acoustically) would be 11'  from the plane of the centre of the baffles, quite a bit short of equilateral. And if firing down the room, the speaker centres would be 8'4"apart, and the listening position as the apex of an equilateral triangle would be 10ft from the wall behind the speakers, so bang in the centre of the room, which is also not a good place acoustically.

I know the instructions say to adjust if it doesn't sound right, but so much adjustment would be needed in that example that the so-called 'ideal' position is rather misleading. (And curiously, the position is rather closer to a corner than ai would expect to be ideal for a full-range speaker, but OK if that is where they were designed to be placed)

Filipe posted:

Based on the Focal advice I think the OP's room should be reasonably ok apart from the hard surface behind the listening positions.

But the OP had problems, and might not be able to position as recommended, sommust choose the best compromise.