Speaker placement / bass pocket?

[paddyb]

I'm having some problems positioning my Dali Zensor 3's.

I've got them on piles of books at the moment (looking around for second hand speaker stands at the moment). The tweeters are at ear height and I had them about 8 feet apart to make an equilateral triangle with my listening position, as is usually recommended. I've noticed though, that when I stand up, I'm hearing a lot more bass. My room is 12.5ft wide x 11.5ft deep, with an alcove at the back right hand side of 6ft wide x 4.5ft deep. I have my desk in this alcove and also notice the bass is much more pronounced when sitting there.

I mentioned this to a dealer yesterday and they said it was probably a "bass pocket" (I think) and suggested moving them closer together. I've now got them 6.5 feet apart and it does seem to have helped a little bit, but there is still a noticeable difference and I feel I'm losing a bit of soundstage.

Any ideas? I've googled "bass pocket" and nothing relevant comes up, so it must be his own way of describing it. The speakers are along the width of the room and will need to stay there as there is no other way to arrange the room, but I hope there might be some minor tweaks or room modifications that can help.

 

[RobinKidderminster]

Bass trap & room treatment. Lots of threads here and elsewhere

 

[MakkaPakka]

http://en.m.wikipedia.org/wiki/Room_modes

 

[paddyb]

Thanks for your replys. I've looked at the Wikipedia article and had a bit more of a google and get the general idea but a bit lost on specifically how to put this to use in my situation.

Based on the description of the room I gave and the problem I'm experiencing, where would bass traps be best employed (and what shape)? By the speakers? In the area where the "bass pocket" is strongest (not much wall space here due to door to balcomy)? Note that I don't necessarilly want to loose the bass, just focus it more on my listening position. I also have laminate floors, which I know aren't going to help either, rug on shopping list!

 

[JamesMellor]

I'm having some problems positioning my Dali Zensor 3's.

I've got them on piles of books at the moment (looking around for second hand speaker stands at the moment). The tweeters are at ear height and I had them about 8 feet apart to make an equilateral triangle with my listening position, as is usually recommended. I've noticed though, that when I stand up, I'm hearing a lot more bass. My room is 12.5ft wide x 11.5ft deep, with an alcove at the back right hand side of 6ft wide x 4.5ft deep. I have my desk in this alcove and also notice the bass is much more pronounced when sitting there.

I mentioned this to a dealer yesterday and they said it was probably a "bass pocket" (I think) and suggested moving them closer together. I've now got them 6.5 feet apart and it does seem to have helped a little bit, but there is still a noticeable difference and I feel I'm losing a bit of soundstage.

Any ideas? I've googled "bass pocket" and nothing relevant comes up, so it must be his own way of describing it. The speakers are along the width of the room and will need to stay there as there is no other way to arrange the room, but I hope there might be some minor tweaks or room modifications that can help.

I'm not stalking you but I think you've had these a month , so there are as run in as can be , I'd go back to 8 feet , no toe in and some "light" speaker stands , get rid of the pile of books , millions of years ago I got a pair of Royals and blue tacked them to the pair of heavy actama stands I'd used with my Castle Durham 900's , the stands killed them , they where dead went back and talked it over and and was given some light stands the dealer had demoed them they came alive .

So get them back to the triangle , get them off the books and dont toe them in , then move them about abit closer to the wall or father away , that can make a massive differance

James

 

[RobinKidderminster]

Agree with James re positioning. Take a look at my sig for some diy bass traps - if it works u can invest as necessary.

PS. Dont think that traps reduce bass. Read on if I may suggest.

 

[MakkaPakka]

Bass traps dont take bass away they limit the reasonance that occurs when bass waves hit your walls. This tightens the sound up across the whole frequency range because the bass waves will hang around for several hundred milliseconds otherwise and muddy everything else.

You should put bass traps in corners, as many and as deep as possible. More may be helpful in specific spots but just treating the corners behind speakers may be all you need.

Have a look at the real traps site and gik acoustics. Checkout ethan winer on youtube as he explains all the basics. In my opinion bass traps are the most significant upgrade you can make.

 

[ID.]

Same happens in my living room. I also get a significant collection of bass in front of my refrigerator...

In my case it is all down to the acoustics of the room, so I think I'd have to do some room tuning with bass traps, etc.

 

[davedotco]

Bass quantity will vary around a room, particularly one of domestic proportions, in my experience 'treatment' is only really required in very difficult rooms or if you want to play pretty loud.

Firstly play around with the speaker positioning and, if possible, your listening position. A foot or two forward or back can make a big difference.

People often talk about adjusting 'toe in', ie whether speakers are facing straight forward or angled in towards the listener (in the horizontal plane), but rarely talk abount the way the sound of speakers vary in the vertical axis. Generally, two way speakers such as your Dali's actually angle the sound downwards, rather like dipped headlights, this is not really an issue as the speakers will be balanced to sound right with the tweeter around ear height.

However high frequency response will often drop off quite quickly when you move off axis vertically, ie when you stand up. HF response can drop off quickly shifting the balance strongly towards the bass end. This is probably what you are experiencing when you stand up.

You should try and ignore that, along with the bass variations within the room and concentrate on getting the sound as you want it in the listening position.

 

[ID.]

If the OP's situation is anything like mine he may have a bit of a bass null at what is supposed to be the ideal listening position at the head of the triangle.

 

[sheggs]

Before applying any type of room treatment I would recommend two things to look at first -

a) The position of your listening poistion. Ideally your speakers need to be on the short wall facing down the room. In an ideal scenraio the area where your speakers are should be symettrical. ie. side walls equal distance apart, no doors or windows

b) 2nd Monitor position is very important. Common issue are -
Speakers too close together[/b]: narrow stereo image. No real sense of where things are panned in the mix. Basically mono except for the most extreme-panned elements.Speakers too far apart[/b]: marked left/right localization (mix elements panned left/right are “stuck” there with no real sense of larger ambience). No real sense of mix depth, and in some cases no sense of a center-image. It extreme cases a sense of “big mono” where all elements of the mix are localized left and right with little or no center image.Speakers too low/too high[/b]: dull, muddy mid-range; source material sounds “shallow”. Speaker-under-a-blanket effect. Sound changes radically with small vertical head movements.Speakers unequal distance from the listener[/b]: marked comb filtering, the effect of which could be an ice-picky mids/highs or dullness in the mids/highs; localization in the left or right speaker[/list]

 

[sheggs]

If the OP's situation is anything like mine he may have a bit of a bass null at what is supposed to be the ideal listening position at the head of the triangle.

Then I would move onto room treatment. It can easily be sorted and for relatively little cost

 

[davedotco]

If the OP's situation is anything like mine he may have a bit of a bass null at what is supposed to be the ideal listening position at the head of the triangle.

Not at all unusual, hence my suggestion to try moving the listening position.

I have the opposite situation, my 'relaxing' position is on the sofa but that is against the back wall and I get noticeable bass boost. Mostly music is played at lower levels while relaxing, so a kind of built in loudness function. If I am playing 'to listen', I play louder and move forward about 4-5ft.

 

[MakkaPakka]

He said the room is 12.5 x 11.5. There is only going to be so much he can move things around - I don't think you can reduce bass boom in a room that size without some 'help' - particularly as it's virtually a cube. I have a room a similar size - a GIK 244 trap behind each speaker completely eradicated bass boom.

 

[davedotco]

He said the room is 12.5 x 11.5. There is only going to be so much he can move things around - I don't think you can reduce bass boom in a room that size without some 'help' - particularly as it's virtually a cube. I have a room a similar size - a GIK 244 trap behind each speaker completely eradicated bass boom.

The OP is complaining about too little bass, not too much.

We need suggestions how to increase the bass levels at the listening position.

Sure, trapping can tighten up the bass so you can play louder but I am not sure this is the requirement.

 

[sheggs]

If the OP's situation is anything like mine he may have a bit of a bass null at what is supposed to be the ideal listening position at the head of the triangle.

Not at all unusual, hence my suggestion to try moving the listening position.

I have the opposite situation, my 'relaxing' position is on the sofa but that is against the back wall and I get noticeable bass boost. Mostly music is played at lower levels while relaxing, so a kind of built in loudness function. If I am playing 'to listen', I play louder and move forward about 4-5ft.

That would be back wall interference causing standing waves. This can be solved with just a couple of thick panels on the wall behind the sofa at head height

 

[sheggs]

Standing waves bounce against each other creating NULLS or PEAKS in the room. The physics behind this is the same. When treating a room you are primarily trying to -

Smooth the frequncy response, ie create an even sound around the room to prevent nulls and peaks

Cut down the decay time, i.e. the amount of time that any soundwave will bounce around the room.

There are a couple of excellent acoustic primers on google if you look up 'Acoustic room treatment primers' if you are interested in learning more

 

[MakkaPakka]

I understand what you're saying but reducing the boom and evening things out a bit will make it sound like there's more bass. Naturally, when it is more even you can go up a notch on the volume.

 

[davedotco]

If the OP's situation is anything like mine he may have a bit of a bass null at what is supposed to be the ideal listening position at the head of the triangle.

Not at all unusual, hence my suggestion to try moving the listening position.

I have the opposite situation, my 'relaxing' position is on the sofa but that is against the back wall and I get noticeable bass boost. Mostly music is played at lower levels while relaxing, so a kind of built in loudness function. If I am playing 'to listen', I play louder and move forward about 4-5ft.

That would be back wall interference causing standing waves. This can be solved with just a couple of thick panels on the wall behind the sofa at head height

I know what it is, but deal with it by moving the listening position forward as I said, not a problem.

Having even a rudimentary understanding of how things work in a room makes it pretty easy to optimise the listening position, I find treatment beyond normal furnishing to be rarely necessary.

Whilst I appreciate that this is not what you are advocating, some recent experience in quite heavily treated rooms have left me wary, as far as listening for pleasure is concerned. As a working environment, that's different.

 

[RobinKidderminster]

I think many get confused with the phrase bass 'trap' assuming that this is a reduction in bass..Simple wave physics explains that sound cancellation occurs when waves interfere. Noise cancellation (headphones) work by adding sound out of phase with external 'noise' and in the same way, reflected sound can cancel the original sound creating bass nulls. Bass traps aim to remove the reflected sound hence avoiding cancellation effects. It seems odd at first sight but a 'loud' sound played together with the same sound out of phase can become inaudible.
It is therefore correct to consider a trap as a device to remove sound which would otherwise reduce/cancel the original sound.

 

[MakkaPakka]

I find treatment beyond normal furnishing to be rarely necessary.

But this depends on the size of the room. This is with the mic set well into the room away from the back wall. Do you think you could fix this with some furnishings?

 

[davedotco]

Having spent a fair part of my working life in acoustically treated environments I find them 'difficult' when listening for pleasure.

This may well be me, but I find playback in a normal environment preferable. Having also spent cosiderable time selling hi-fi, I have rarely come across rooms that could not be 'sorted' by speaker placement or setup though on occasion optimum setup has been domestically unacceptable.

That said, this is an area in which I have no technical expertise, beyond basic science that is, and only really have my experience to go on.

It is though, an area I will read up in, I have another room that is very replactive and hard, I get a fair amount of flutter echo at higher levels and a 'hollow' sound when listening at distance. In this case I combat these issues by setting up so that I am sitting very close, virtually in the near field, but this is not exactly sociable.

The room is designed to be very visual, very 'clean' and open with large windows giving great views. I am sceptical whether any treatment would be acceptable but this is an area I have always meant to investigate, maybe this will give me the impetus to do so.

 

[davedotco]

I think many get confused with the phrase bass 'trap' assuming that this is a reduction in bass..Simple wave physics explains that sound cancellation occurs when waves interfere. Noise cancellation (headphones) work by adding sound out of phase with external 'noise' and in the same way, reflected sound can cancel the original sound creating bass nulls. Bass traps aim to remove the reflected sound hence avoiding cancellation effects. It seems odd at first sight but a 'loud' sound played together with the same sound out of phase can become inaudible. It is therefore correct to consider a trap as a device to remove sound which would otherwise reduce/cancel the original sound.

Thank you Robin, that is helpful.

 

[davedotco]

I find treatment beyond normal furnishing to be rarely necessary.

But this depends on the size of the room. This is with the mic set well into the room away from the back wall. Do you think you could fix this with some furnishings?

I understand what you are getting at but it is my view that you do not, in most cases have to fix anything.

All rooms have a different response, a different sound, it is easy to hear. But in your own room the ear adjusts and sounds in that room become normal. I have already said that there may be some rooms where treatment can be helpful but in most cases I do not find it is necessary.

Then again, as I have explained in other context, I do not find the way systems alter from room to room that much of an issue, as I have said often enough these are 'presentational' issues that I find have little effect on the 'quality' of the music reproduction.

 

[sheggs]

I find treatment beyond normal furnishing to be rarely necessary.

But this depends on the size of the room. This is with the mic set well into the room away from the back wall. Do you think you could fix this with some furnishings?

I understand what you are getting at but it is my view that you do not, in most cases have to fix anything.

All rooms have a different response, a different sound, it is easy to hear. But in your own room the ear adjusts and sounds in that room become normal. I have already said that there may be some rooms where treatment can be helpful but in most cases I do not find it is necessary.

Then again, as I have explained in other context, I do not find the way systems alter from room to room that much of an issue, as I have said often enough these are 'presentational' issues that I find have little effect on the 'quality' of the music reproduction.

Everything is in context and I agree when it comes to your own listening pleasure how much you treat / don't treat your room is up to personal preferences. I think however for people new to room acoustics understanding what can be fixed readily and easily i.e. flutter echo, back wall reflections etc and what this means to your room environment. I am sure there are plenty of people who 'put up' with certain aspects of their listening expierence because they do not realise this