Speaker placement [Archive] - Audio & Video Forums


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12-21-2006, 02:07 PM
I have rear speakers on my RSF1000's,I'm sure you knew that. How far do I keep these from the wall and how far apart.Right now they are on either side of my entertainment center which is close to 5 FT. wide and they are probably 8 in. from the wall.Just trying to get the best sound from them possible.Oh and my living room is about 12.5 x 15 ft. so I don't have tons of room.

12-21-2006, 03:16 PM
What does your manufacturer suggest? Most speakers come with placement suggestions. Unfortunately, it's impossible to recommend anything other than "whatever sounds best to you." Every room will interact with every speaker differently, so there are no hard and fast rules regarding placement. Just play around with the distance and toe-in until you have a stable image and good, clean sound. Pay attention to first-order reflections and if you need more bass, try moving them closer to the corners (just don't mistake boominess for good bass). If you really want to get serious, do a search for "room treatments" and you'll be rewarded with a wealth of information. Also search "Richard Greene" who wrote a few articles on room nodes/modes that should be mandatory reading for anyone truly interested in getting the best sound possible out of their rig.

Hope this helps.

12-21-2006, 05:17 PM
Hey thanks,what does toe in mean? I don't have the manual for these and I can't seem to find one anywhere.I've heard though if you get the rear firing speakers too close to the wall some kind of cancellation occurs,I'm not really sure what I'm listening for yet.

12-22-2006, 09:59 AM
Toe-in is when you angle your speakers towards the listening postion as opposed to having them fire straight ahead.

I'm not familiar with your speakers at all, but are you saying they are bipoles (i.e. rear firing drivers)? If so, that changes everything. Bipoles need lots of room to work correctly. I'm thinking usually 3' or so from the back wall. Minimum. The only bipoles I've encountered that don't need that much room were Energy Audyssey 5+2's where the rear drivers were purposely out of phase to allow near-wall placement.

Bipoles are designed to give a very diffuse sound by bouncing the sound off the rear wall. The challenge is if this sound comes back at the listener out of phase with the direct radiating speakers (the front facing drivers) thereby cancelling some frequencies out and/or augmenting other particular frequencies. You'll need a lot of space and very likely room treatments on the back wall and on the sides. Here is a good article (http://www.acoustics101.com/) on room acoustics that might give you a better handle on things. Chapter 1 will give you the groundwork and if you want to start treating your room, just read on.

What are you looking for? Whatever sounds best to you :). Most of us are looking for the best approximation of a live event, albeit tethered by the limitations of our own gear and listening environments. Here is a great guide on speaker set-up from Jim Smith, a hi-end retailer and consultant. I got this from PS Audio's monthly newsletter and found it very informative.

Jims tip
For those of you new to the newsletter, Jim Smith helps us a great deal and one of the reasons we have him on board is his years of experience at Magnepan, Audio Research, Avantgarde and as a high end retailer. He's sharing with us his 31 secrets to achieving better sound from your system, and I find these extremely valuable.

This is a really involved tip, but I can tell you from personal experience, if you follow what Jim's writing about here, you'll likely find as big an improvement as you're likely to enjoy in your system. Good setup can, many times, provide benefits greater than even a new piece of equipment. So, read on, roll your sleeves up this weekend and make your system sing!

4) A simple three-step speaker installation technique for satisfying results
This three-step technique will get you to a satisfying sound faster than any other system I've seen.

The three steps must be followed in this order.

1. Bass
2. Image
3. Frequency response/tonal balance

OK, what do we do at each step?
First, you've got to get the bass generally pretty good. This means that if you have a full-range speaker, it should reproduce the deepest bass with the greatest smoothness.

Why does the bass come first?
Until you know how far away you'll be sitting (speaker position and listening position), how can you proceed to step 2, getting the best stereo image? And we've seen that we can make some adjustments in the overall frequency balance with subtle changes in position (separation and toe-in). But first weve got to at least establish the distance to the speakers from the listening seat before we can begin to decide how far apart we want our speakers.

(1) The best bassa throwback to early TVs.
Here's how long I've been teaching this technique for getting the best bass

I started out using a TV analogy that asked the installer to compare this step to the tuning methods from TVs of the '60s and early '70s! Those TVs had a fine tuning knob and channel selector switch. Here's the analogy: Finding the best placement for the speaker in the room is a bit like fine tuning for best reception. But finding the best place to locate the listening seat is a bit like using the channel selector!

In other words, the most important consideration (whenever possible) is to discover where in the room you should sit to take advantage of the least negative room interactions (obvious peaks and dips in the bass), and the most positive room interactions (the most extension and attack without annoying overhang).

This is because your room will have obvious standing waves developing in the bass region (well call this region 25 Hz to 250 Hz). These standing waves are very measurable and they are quite audible as resonances or 'suck-outs.' They exist due to your room's particular geometry.

Moving a speaker forward and back in the room can make a noticeable difference in the bass. But moving the seat forward and back the same distance in an average room will result in much more dramatic differences in bass performance.

Although these resonant room frequencies can be considered axially, tangentially, and obliquely, our primary concern here is with axial. These consist of destructive (to varying degrees) waves and constructive (to varying degrees) waves. A destructive standing wave is produced when two or more wavelengths meet at a point in a room, anddue to the time arrival of these wavessome will arrive slightly (or even directly) out of phase with others.

The varying time arrival is based primarily on room geometry (for examplelength of the room vs. height). This results in a cancellation of frequencies at that particular point in the room. Destructive standing waves produce dips in frequency response. Conversely, constructive standing waves can produce peaks in response.

The following system assumes you've placed the speakers in a generally acceptable position in the room:
A simple way to prove this theory is to put on a CD recording with a repetitive bass line (preferably the upright acoustic bassmaybe Ray Brown). You'll need to move your listening seat out of the way, perhaps to the side of the room.

A note on the recording select a piece that plays bass notes up and down the scale. While it's playing on repeat (that's why I chose CD as the source), walk back and forth slowly through the larger proposed listening area. You'll notice dramatic differences in bass quality and quantity in a space of +/ 2-3 feet. Listen closer and you'll find the smaller 'window' of acceptability for that particular bass line.

Once you've found the best spot to locate the seat (again, only for that particular series of bass notes), you'll notice that moving the speaker forward and back an equivalent difference makes much less of a difference. This is all to say that your room resonances are going to be pretty much the same for most likely speaker placements, so find out where in the listening end of the room these resonances are least objectionable, and that's where you'll sit.

A quick note on finding the overall best bass listening position in a roomthe quickest way to do it is with a real-time analyzer, preferably 1/3 octave. You'll need to use pink noise as your source, set on the slowest filter, using flat or C-weighting. You'll need to run its SPL level at least 20dB over the room noise floor, so as to avoid any unrecognized interference with your measurements.

You're only looking at the region from around 25 Hz up to about 250 Hz. You'll notice immediately that fairly small movements forward and back in the room are very obvious on the display as the various peaks and dips become quite easy to see.

Don't have a RTA sitting around? Try to borrow or rent one for a few hours. By the way, I do NOT recommend using a Radio Shack SPL meter and test tones for this procedure. Actually, if the tones were 1/3 octave pink noise bands, it could perhaps work, but unfortunately the Radio Shack meter simply isn't very accurate in its frequency response. And the RS mic suffers from proximity effect, unlike an omni (which is the preferred pick up pattern for a microphone in this application).

You could use the test disc and your ears, though! Can't find a RTA, or youre uncomfortable technically with the idea of looking at how your room behaves in the bass resonance region?

Then find several recordings of music representative of the stuff you like to hear, and adjust for the best bass by listening while moving back and forth in the general listening position. What you're listening for is the majority of the bass reproduced with the notes neither emphasized nor diminished. You're also listening for the deepest bass. But sometimes the price for getting the deepest bass in an average room is an uneven bass response in the region where most bass notes occur. This is where youll have to pick the best compromise to your ears.

At this point, you'll find that a difference of six inches or less forward or back will usually present you with a choice of the bass compromise you prefer. Once you've discovered this listening position that is least affected by room resonances, mark this spot (or at least measure how far it is to the wall behind you and write it down).

Now you can play with fine-tuning where the speakers go to make the bass better. Once you have that position to the point that is best to your ears, you'll need to recheck the listening position a bit to make sure that a slight distance forward or back isn't necessary now.

(2) Imaging and the X-files
Finally you've establishedpretty closelywhere you'll be, and approximately how far away the speakers will be. Once you know 'X,' you can start to work on 'Y.' X is the distance from your ear to the plane of the tweeter (should be equidistant from the listening seat to each speaker). Lets say X is 10 feet. A general guideline is to start Y at about 80% of X. Y is the distance from the center of the left tweeter to the center of the right. We use the tweeter because its the primary source for directional cues (imaging).

A note on separationthis is to your taste. I personally like Y to be about 83% of X for most speakers. For planar speakers, Y may be smaller, maybe as small as 70-75% of X. Some companies want you to use an equilateral triangle (X and Y are equal in distance), or greater. I suggest playing a mono source like female vocals and keep pulling the speakers apart until the voice becomes a fairly precise point between the speakers. Pulling it apart any further results in a too small voice or one that now begins to come from each speaker. Bring them back to the point where it worked, switch from mono to stereo and check out the image. This technique assumes you've established a grid on the floor so that movements are the same for both channels.

The other test is simply to notice when the female voice starts to sound unacceptably thin. Then voice the separation by tonal balance, as well as image precision. Once again, it's a compromise. You have to decide what means the most to you.

(3) Frequency response/tonal balance
Remember how we said that changing the separation could yield a cooler or warmer sound? And how toe-in can also dramatically affect balance (particularly high frequency balance)? Well, now you're at that point (this assumes that your speakers are either nonadjustable, i.e. tweeter lever control, bass level control, etc., or that you've selected the nominal 'flat' position as a starting point).

Here's an exampleand listen, it's just an exampleyou might feel quite differently. I find that if I set up most direct radiating speakers on an equilateral triangle, the sound (for my taste) is usually too lean. I can hear all the tiny sounds in the soundstage, but it's become a precise, almost mechanical sound. It's not 'relaxed' for want of a better word. It makes great Audiophile stuff, but the sound just doesn't have the body and warmth that I hear with live music.

And yet, I know highly respected reviewers and manufacturers who prefer to listen with Y being greater than X. Thats why its your tasteremember, it's not about some notion of 'accuracy,' it's about the music and you.

Step 3 is the final fine-tuning that will make the difference for you. One final notesome Audiophiles adjust toe-in to make the speaker seem to 'disappear.' This is usually not on axis, but aimed to crossfire somewhere behind your head, or even aimed straight ahead. This is your call as well. I recommend going for the musical balance before going for an audiophile sound effect, but sometimes you can get both, so go for it if you like

This should get you pretty close to a satisfactory set-up.

There are even smaller increments of adjustments that can pay significant dividends, but that's a topic for another time (I call it 'Playing the room').

12-22-2006, 12:43 PM
Thanks man that is great! My speakers are Di-polar and the highs seem to all mesh into each other when pushed a little when they are that close to the wall.There is no way I can set them 3 ft. from the wall,they would be in the middle of the room then.I have a 12x15 listening area.

Dusty Chalk
12-22-2006, 05:49 PM
You should seriously consider room treatment for right behind them then. The problem is, you'll get the sound directly from the speaker interacting with the "first reflection" off the wall behind it, which will be slightly delayed. What this yields is comb filtering. I don't know how to describe comb filtering unless you've heard it, but try moving your head around with respect to the speakers, especially forward and back. You should notice the frequency response doing some weird things, like playing around wildly with a 31 band equalizer.

12-22-2006, 06:15 PM
Dusty I finally found a manual for these today from the guy I bought them from,I disabled the rear speakers,the recommended space between the wall and speaker is at least 18in. and I can't get near that,the ideal space is 24in. I don't have the problem now I had before when they were running,it's alot cleaner with better separation with the fronts and center running.