# Surround speaker perfecting placement



## marty1 (Jun 29, 2010)

I am considering upgrading from 5.1 to 7.1 as I dont feel I am getting much enjoyment from surround sound speakers but wanted to know if I could improve the accoustics in a room of my size and limited positioning.

At the moment I have dipoles placed at the recommended 2 feet above listening position, they were on the side walls either side of the couch, but a proffessional advised me that they were too close to the rear walls (3feet) and would be better on the rear wall facing into the room 1/3 of the room width apart.

The couch is 2 feet from the rear wall so they are fairly close to me, if I was to get 7.1 I think I would prefer to change to direct firing speakers as I like to hear details and I find the dipoles are a bit too diffused for my liking, I very rarely know that I have rear speakers, I know you are not supposed to be aware of them all the time and thats the point of them but I love hearing all the sounds from all the speakers.

If I changed the speakers and had 2 where the dipoles currently are and 2 where they used to be placed on the side walls to the left and right of the listening position would this work? It would mean the surrounds are 3 feet from the rear wall and the rear surrounds are just behind my head.

I get the feeling that there is not enough distance between the 4 speakers to have any real benefit but would like to know for sure. I also feel that direct firing speakers 2feet behind me would be too close to my ears? I could move all 4 speakers up higher, but that would mean they are 7.5 feet up, not recommended as I have always been told the the closer to ear level the better?

I would appreciate your advice please.

Regards
Marty


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## andywolf (Oct 9, 2010)

hey marty, 

i do not think that upgrading to 7.1 from 5.1 will help you with this problem, i would suggest possibly positioning the sofa further forward and the rear monitors slightly lower and wider apart. 7.1 is basically the same as 5.1 but with two extra outputs, 5.1 is still the standard used by most films anyway. When film producers create the sound tracks, they put the majority of the sound in the front center and front left & right, with minimal sound effects in the back, they do this because they want your attention to be on the screen at the front, not on the rear speakers or the exit sign, hence "the name exit sign effect". One of the best possible applications for 7.1 is in larger installations where there is a greater distance between front & rear satellites, If you have too much distance between them you do not get an accurate stereo reproduction. 2 more speakers can be placed in the middle to aid in the Creation of a stereo image between front and rear. Ideally you want to have equal distance between the fl & fr, rl & rr, so that all four speakers form a square. You need to be in the middle of that square to get the most accurate reproduction, or the most accurate perception of that reproduction anyway. sub placement is not so important but you must have a proper decoder so that the sub acts as it should, some decoders just route the low frequencies from the satellite speakers, what should be sent to the sub is the dedicated 6th channel called the lfe, but i digress!! 
what you could do is send a stereo signal to your decoder, you would then get all the sound from all the speakers all the time, just a thought though. 

hope this helps or at least gives food for thought, 

regards, 

Andy


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## marty1 (Jun 29, 2010)

There is 2 problems with placing the couch in the centre of the room:

1. I will be too close to my pj screen which is 9ft wide and I will only be 9 feet away from it.
2. For good quality bass response it is always suggested that the back 3rd of the room is the ideal area, the centre, unless you have several subs to fill the rooms up, then the centre is normally quite a bad position as the bass will sound quite weak.

I can move my couch a little further forward, maybe a foot or so if this makes a difference?


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## Stele (Jul 3, 2010)

Marty,

Lionsgate is the only movie producing company at the moment producing 7.1 Blurays (unless someone can enlighten me otherwise). The movie production studios have to upgrade to 7.1 to be able to produce it of course, which costs time, money etc. But they will as more and more people take it on, indeed all the latest receivers have 7.1 decoding. So while 7.1 is not a must have at them moment, it will no doubt become so 'sometime' in the future.

Go to almost any movie production studio and what you will find is direct radiating speakers, not dipoles. The theory with dipoles is they create a null 'on axis' so they can be placed very close to the audience and not be distracting, and the surround sound is reflected from the front and back walls. However there are to major flaws in this, one I mentioned earlier that the sound studios (most) don't use them, so when the audio engineers create the surround effects, they use the direct speakers they have. The second flaw is to perceive 'spacious', 'enveloping' surround sound, the surround effects actually need to be coming from the sides, any where from 60° to 135° to be precise (0° is straight ahead as you sit and 90° would be to your exact left or right and 180° would be exactly behind you). 

The standard ITU-R .775-2 (2006) identifies speaker placement at 0° (center speaker), +/-30° (Front Left & Front Right) and at +/-120° (Surround Left and Surround Right). This is for 5.1 placement. If you look up the recommended speaker place on the Dolby or THX website they will be pretty close to this.

The distances of the surrounds don't matter so much as you can adjust the timing on your amp (even surround sound field is another discussion).

For the Vertical height of your surrounds, 2 feet above the listeners ear level is pretty spot on, of course room lay out and reality gets in the way of all these specifications.

Avoid placing your front and rear speakers in symmetry, this does nothing for envelopment of sound. It is the way our ears work and the way we localize sounds.

In regards to your seating placement, on the wall is a bad idea as this is a pressure maximum for all base room modes, 2 feet off the wall is better a little more would be better still, but this of course comes down to your room layout and preference.

With all due respect, I have to completely disagree with Andy, Sub placement DOES matter, a lot! Position will excite different room modes for each position and is a massive discussion topic, of getting good even bass response for all listeners.

If you want to read all about this and much much much more, I can not recommend the book: Sound Reproduction, by Floyd E. Toole enough, it is a simple brilliant book and will open your eyes acoustically so to speak. It goes in to not only what you sound do but how and why you sound do it, the things to avoid and the things to strive for.

In summing up for your situation, I would highly recommend getting a pair of direct firing surround speakers that were designed to be put up against a wall (not a bookshelf speaker) and place them back to where your previous surrounds were or even more to the front of the room. 3 feet from the corner is ok, but don't place them in the corner. Refer to the book I mentioned Sound Reproduction, page 292 Chapter 15.10 Finding the Optimum Channel/Loudspeaker arrangement specifically 15.10.2 "Optimizing the Delivery of Envelopment"

Pete
THX Certified Professional


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## marty1 (Jun 29, 2010)

Stele said:


> Marty,
> 
> Lionsgate is the only movie producing company at the moment producing 7.1 Blurays (unless someone can enlighten me otherwise). The movie production studios have to upgrade to 7.1 to be able to produce it of course, which costs time, money etc. But they will as more and more people take it on, indeed all the latest receivers have 7.1 decoding. So while 7.1 is not a must have at them moment, it will no doubt become so 'sometime' in the future.
> 
> ...


I shall definately invest in that book and a pair of direct firing speakers.

I definately agree about the sub, it has taken me a long time to find the correct position and having recently got to grips with REW I am still trying to get it right, its a frustrating target trying to achieve flat response, especially for me and my wife's listening positions.

As for the surround placement I will move the couch as much forward as poss and place the speakers a little way from the corner, are they ok next to the side walls, say on wall brackets or is it away from corners and walls?


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## Stele (Jul 3, 2010)

If you buy pretty much any floor standing speaker, the manufacturer will recommend a distance to be away from walls. Other speakers can be built for on wall placement (and indeed in wall placement). I would say almost certainly your dipoles were engineered to be placed on a wall (all though even if they weren't it doesn't matter any where near as much because of the null on-axis with dipoles). It matter quite a bit with front speakers but less so with rear surrounds as surrounds are use to add the feeling like you are there not to play all the on screen action like the all important center speaker.

You will be able to find quite a few speakers specifically designed to be surrounds (direct radiating) and most (if not all?) will be designed to be put on a wall.

'Sound Reproduction' by Dr Toole goes very in-depth into it, and as you will find out the ideal surround speaker is not manufactured at the present time, yet we easily have the technology, perhaps the marketing department has a lot to do with that......

You'll be trying forever to get a completely flat response, and quite frankly due to the awesome auditory system inbuilt in us all - 2 ears and a brain - you don't need it. We have a brilliant ability to listen to rubbish sound and be entertained. That's not to say don't strive for the best you can reasonably make the sound reproduction. Have you ever become tired from listening to music? I know I have, it's because you brain works much harder to decypher the good from the bad. On the flip side of the coin you can listen to a good quality system (room included) much louder for longer, if it is much cleaner sound (the usual suspect is distortion for tired listening). So if you can get close to +-5dB for all listeners (at around 1/12dB per Octave resolution) and not have any undue ringing, then you are doing fantastic. Bass will more then likely be the biggest variances (it always is) due to 'small' rooms and the looooong wavelengths. In the end it'll always become a balancing act with the listening positions and of course, what you want.....and what the misses wants....

Pete


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## marty1 (Jun 29, 2010)

Stele said:


> If you buy pretty much any floor standing speaker, the manufacturer will recommend a distance to be away from walls. Other speakers can be built for on wall placement (and indeed in wall placement). I would say almost certainly your dipoles were engineered to be placed on a wall (all though even if they weren't it doesn't matter any where near as much because of the null on-axis with dipoles). It matter quite a bit with front speakers but less so with rear surrounds as surrounds are use to add the feeling like you are there not to play all the on screen action like the all important center speaker.
> 
> You will be able to find quite a few speakers specifically designed to be surrounds (direct radiating) and most (if not all?) will be designed to be put on a wall.
> 
> ...


I have focal profile 918 floorstanders and centre speaker so I woul really like to get matching rear speakers, If they can be wall mounted does this also mean they can be placed in a corner, I can't see putting them in a corner as having an effect on the sound as you said they are just for added effect, surely there would be not much low frequency sound coming from them that could be exaggerated?

As fo the bass I have done 1/3 octave smoothing if that is what you mean and although not flat, it isn't too bad, but where my wife sits there is a giant dip, unfortunately if I adjust the PEQ then my response goes uneven, very annoying, she would like the best sound possible although she is not as mad on it as I am.

The pb13u is so hard to move around :sweat:, I have tried it in the 2 positions on the front wall but I do have all the side wall to move it along and test but it will look odd in the room there, I wish there was a simpler way of finding the best position, the crawling around the room method is completely unrealistic but lugging 10 stone around is also a nightmare.

Thanks
Marty


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## Stele (Jul 3, 2010)

marty1 said:


> If they can be wall mounted does this also mean they can be placed in a corner, I can't see putting them in a corner as having an effect on the sound as you said they are just for added effect, surely there would be not much low frequency sound coming from them that could be exaggerated?


Indeed the bass from the surrounds will be redirected to the sub (80Hz) but it's not so much of driving pressure maximum (bass room modes) of a problem as the adjacent boundary effects problem. Basically the Adjacent Boundary Effects in this case is the sound waves radiating out of the speaker, bouncing off the near wall and the resulting frequency response has peaks and dips depending on the size of the speaker, the distance and type of boundary and the listening distance and angle. Is it as bad as placing a front floor standing speaker in a corner? Prob not, but that's because a lot more sound comes through the front speakers. In answer to your question, the speaker manufacturer would have to ideally design the loudspeaker to go in a corner, as despite what some marketing departments will tell you, loudspeakers can not live out side the laws of physics so there is no 'universal' loudspeaker. If it was designed to go on a wall a good manufacturer should readily provide minimum distances from other boundaries (ceiling rear wall etc).



marty1 said:


> As for the bass I have done 1/3 octave smoothing if that is what you mean and although not flat, it isn't too bad, but where my wife sits there is a giant dip, unfortunately if I adjust the EQ then my response goes uneven, very annoying, she would like the best sound possible although she is not as mad on it as I am.
> 
> The pb13u is so hard to move around :sweat:, I have tried it in the 2 positions on the front wall but I do have all the side wall to move it along and test but it will look odd in the room there, I wish there was a simpler way of finding the best position, the crawling around the room method is completely unrealistic but lugging 10 stone around is also a nightmare.


With a single subwoofer, you will never get even bass at all frequencies at multiple listening positions. When you move it around you will be also moving the position of the pressure points (or lack there of). EQ will smooth things out a bit, but it reducing the peak at one seat will reduce that freq everywhere else of course too. A good place to start is 1/3 distance across a wall, this assumes a room with 4 right angle corners (doors and windows also change the 'acoustic dimensions' of the room too especially at low freqs).

Don't forget that if you have full range floor standing speakers they can be adding room modes of there own if you have the bass going to them as well. The easiest (and best) way for bass management is to leave it to the speaker that was designed o do exactly that, the sub!

If the room decor and inhabitants allow it, bass traps/absorbers can smooth out those peaks and dips and are a very good idea.

If you can get your hands on one a low platform with wheels on it will save you the dragging around!

In the end it will always be a compromise without multiple subs and some form of sound field management to individually manage each sub.


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## marty1 (Jun 29, 2010)

Stele said:


> Indeed the bass from the surrounds will be redirected to the sub (80Hz) but it's not so much of driving pressure maximum (bass room modes) of a problem as the adjacent boundary effects problem. Basically the Adjacent Boundary Effects in this case is the sound waves radiating out of the speaker, bouncing off the near wall and the resulting frequency response has peaks and dips depending on the size of the speaker, the distance and type of boundary and the listening distance and angle. Is it as bad as placing a front floor standing speaker in a corner? Prob not, but that's because a lot more sound comes through the front speakers. In answer to your question, the speaker manufacturer would have to ideally design the loudspeaker to go in a corner, as despite what some marketing departments will tell you, loudspeakers can not live out side the laws of physics so there is no 'universal' loudspeaker. If it was designed to go on a wall a good manufacturer should readily provide minimum distances from other boundaries (ceiling rear wall etc).
> 
> 
> 
> ...


Thanks

My speakers are crossed at 80hz so the sub Is taking care of the lower frequencies, so really what I must do is say sorry wifey! You want your side to be flat response buy your own subwoofer :devil:


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