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Thread: Listening Distance/Farfield Speakers

  1. #1
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    Listening Distance/Farfield Speakers

    Still "tweaking" the placement of my L200b speakers and was wondering how far back other members were seated from their large monitors (L300, 4333, L220 etc). I'm seated roughly 15' from my L200b with a Pioneer 53" rear projection tv in center. Works very well for viewing but I have a feeling the seating position could go back another five (5) feet for listening. My listening room is 19'x25' with 13' cathedral ceiling, L200b and tv situated on narrow end (19'). I'v heard the term "farfield" used and wondered if it had any specific boundries.

  2. #2
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    I would have to say your room has enough volume and size to get something of a good audio experience happening.

  3. #3
    Member ralphs99's Avatar
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    Hi Majick,

    Personally I'm listening at a distance of about 10' in a pretty small room. That's with 2344 Bi-radials that can be used at close range. The exponentials throw further and probably can do with a bit more distance. Having said that I would be wary of a positoin very near the centre of the room (assuming it's roughly symetrical). Nodes due to standing waves tend to be more pronounced near the geometric centre of an enclosed space (as well as close to the walls of the room, and especially in the corners). You can't do much about the side to side symetry if you're listening in stereo, but I suggest either forward or rearward of the front-to-back centre point. Which you choose will depend on how much of the near field characteristic of the speaker you wish to hear and how much of the reverberant field (far-field) of the room.

    The terms near-field and far-field desribe the direct sound of the speaker and the reverberant sound field set up by the speaker in the room. As you phyically move further from the speaker, the direct sound level reduces and the relative amount of reverberant sound level increases. The point where the two are equal is called the critical distance. The critical distance can and always does vary with frequency. The directional characteristics of the speaker changes with frequency pushing more or less energy into the room. The brouchers usually show the frequency resonse as being nice and flat directly on axis with the speaker- the direct sound field. However, the off axis sound field is never as flat. The off axis response is largely responsible for the reverberant sound field and the reverberant sound field set up by the speaker is usually bass heavy due to the loss of directional control of the speaker slowly reducing at higer frequncies for direct radiator speakers. Horn loading can offer the unusual benefit of having an off axis response almost as good as on axis, thereby illuminating the room equally with sound at over the entire opearting range of the horn. Horns of this type are called constant directivity horns. Older exponential horns sacrifice high frequency directional control and suffer from the same reduction in off-axis response as do direct radiator drivers.

    The room the speakers are placed in will also have a marked effect on the reverberant sound field. Rooms with a lot of soft furnishings will tend to absorb more of the higher frequencies than the lower ones, thus reducing the amount of high frequency energy in the reverberant sound field. The placement of the speakers is another factor. Corner placement will increase the loading at low freqencies as the speaker is looking into a smaller angle, boosting the reverberant field. Therefore in almost all listening rooms the critical distance is very small at low frequecies, becoming larger at the frequncy is increased. With my 2344 constant directivity horns in a reasonably 'live' room, the critical distance is pretty constitent at about 5' from around 400Hz up to 10kHz. Critical distance can be simply measured with 1/3 octave pink noise and a sound level meter. When you are in the direct sound field of the speaker the level will drop by 6dB each time you double the distance away from the speaker. As you approach the critial distance, the reduction in level will be smaller. As you move even further away, fully into the reverberant sound field, the level will be relatively constant with increasing distance. So at my listening distance of 10' I am listening to mostly the reverberant sound field but with a substantial amount of direct sound. Very importantly, due to the constant directivity horns, the reverberant sound field is relatively flat and there's a large 'sweet-spot' around the typical listening position.

    Armed with the facts, try listening at various distances to some percussive material. Note how you can hear more of the room as you move further from the speakers. Try and listen for the character of the reverberant sound field. This will give you clues as to what kind of acoustic treatment the room may benefit from. Ultimately it will be your personal preferance to how much of the direct and reverberant sound field you wish to hear. A good sounding room is a pleasure to listen to. A bad sounding room can be taken out of the listening experience by moving closer to the speakers. Now you know why near field listening can be very accurate but less satisfying than listening in a large, well designed room.

    Cheers! Ralph.




  4. #4
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    majick47, my 4333's start to sound very good indeed at around the 12-15 foot distance. Coincidentally, that's just where the computer is!

  5. #5
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    About 12' for me with my S22-2 system, I found that 8-10' did not work too well. My room is about 13' wide and I just up-sized the Sonex first reflection absorbing side wall teatment from 1" to 2". What a difference!

    I am using three 2x4 panels wach side. They are a bit expensive, but well worth it in my situation....

  6. #6
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    2 cents worth

    Try this.... place listening position 10 feet from rear wall, no less. With cabinets facing the listening position, place horns 42" from side wall, and 55" out from front wall. Elevate speakers so woofer center is about 3' off floor to start. Angle cabs so horns are aimed at your head. If too harsh aim over your head to taste. On the side walls center some absorbent material 89" out from the front wall. Make sure it's at least 2' x2' or so. Elevation of this material will be between the height of the horn and ear level at listening position. Place some absorbent material behind the speakers too. Place this about halfway between each speaker and its corner. Try about 6' wide or so. Arrange this so it runs from the floor to about 8' or so high. Sit in your spot and have a buddy (not the wife) move a mirror around while it is held against the ceiling. When you can see the horn mark the spot. Do both horns. Place absorbent at the spots. Use thick cushions from couches and chairs as absorbent for the experiment. If you really wanna get fancy - repeat the mirror thing on the floor.
    I didn't just dream this up BTW. It came from a quicky (lunchtime) Autocad peek of your room. The 10' thing gets you a (almost) 18 ms delay off the rear wall. Thats ok. If you can diffuse the return do it. The side wall reflection is at 4ms relative to direct path - a bad thing. The floor reflection is less than that - a 'badder' thing yet. The speaker distances from the wall boundaries are the end result of getting some important things placed - like getting the rear relection time right (20 ms would be better, but your boundaries suffer) and getting out of the center as ralphs99 indicated. Your now in an equilateral triangle with a direct path of 12 feet, and you are almost 3 feet behind center. The resultant boundaries are pretty good from a starting point - 3 feet or better and they are all different. Move the cabs around a bit too. If you move them a lot recheck absorbent placements with the mirror. If I knew the configuration of your cathedral ceiling, I could have kept your buddy from falling off the ladder - sorry for that. If you like this (you will) there are lots of things you can use for absorbent that's cheap and looks good - and won't get you locked up for hanging furniture about your room. Your gonna get a strong reflection off the TV too, as well as other stuff in the room. Look for it and 'fix it'. Your room is plenty big so this is worth it. There are lots of other issues you could deal with, but this will get you a long way there. Have fun!

  7. #7
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    Listening Distance

    Ralph many thanks for taking the time to post all the info, also appreciated the posts by Chas, Jay and John. Spent some time last night repositioning the L200b and they are now 15' from my listening position which is the 2/3 point of my 25' long listening room. The speakers are 8' apart, 5' from the two side walls and 3' from the back wall. Added to this the L200b have a moderate toe in to center. So far I'm pleased with the results but feel that a little more tweaking of the toe in could improve the sound. I'm also useing the two L200b speakers in a H/T setup with a Magnum Dynalab MD-10 (virtual surround sound processor). I'm fairly confident I can get the sound just right both for two way and "surround" if i keep playing with it.

  8. #8
    Administrator Mr. Widget's Avatar
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    Listening Distance

    For Home Theater, the listening distance is more or less determined by the viewing distance. In my room I have a 10' screen and I view it at about 16'. I have the L/R speakers placed at the edges of the screen. If you spread them farther apart it can get weird as you may have sounds for the film coming from off screen when they should be on screen. Obviously if you are using a 42" or smaller display you have to make a compromise here.

    For two channel music reproduction you should have an equilateral triangle. If you have your speakers 8' apart, you should sit 8' away from each speaker as well. Some people like to get a bit closer for a wider sound stage and others prefer sitting a bit farther away for a narrower sound stage. Since most music is mixed with an equilateral setup, if you want to hear it as it was designed to be heard this will get you the closest to that version of "reality".

    Widget

  9. #9
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    Seating Distance

    SteveW and Mr Widget your advice has been very helpful in my attempt to improve the setup in my listening room. Actually I'v had a good sucess by moving the speakers out from the front wall with the baffleboards placed in front of the 53" rear projection tv. Imaging, depth and seperation is now excellent. As I originally intended the h/t setup will be secondary to the two way system. Today I plan to make new grills/frames and shortly have the L200b speakers with 2405 tweeters/3106 crossovers ready for posting pictures. I'll also include pictures of the listening room/equipment showing the layout. In the the end I know that with your help these speakers will reach their full potential which will be nothing short of awsome.

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