Does setting distance of speakers on receiver actually make a difference?

**hershon** · 10-03-2004, 08:05 AM

I nominate myself for stupid question of the year, but if anyone is in a charitable mood, please give me some pointers on this. Specifically, I just installed a second home theater system in my bedroom & I'm trying to get the sound (volume) balanced. The rear speakers are on my nightstands about 2-3 feet from me on my bed and the satellites are on my dresser, about 17 feet from my listening position on the bed. I set the distance at about that on my receiver speaker configurations and while the balance is OK its not great.
Do these distance settings on the receiver actually effect the volume from the speakers? If so, is the following applicable- the closer the distance set, the lower the speaker sound & the longer the distance set, the louder the speaker sound. Any pointers you'd recommend & or are there any general rules on this, such as add/delete actual feet when configuring on your receiver?

**N. Abstentia** · 10-03-2004, 08:55 AM

I would think the distance would affect the delay, not the volume. There should be a seperate level adjust for each channel.

**sy_lu** · 10-03-2004, 02:07 PM

Distance only affect time delay. You do need proper time delay for rear speakers for the correct sound effect. You also need to set/balance sound level using a SPL meter. Some receiver can do auto setting you may still need to manually adjust them a little.

**hershon** · 10-03-2004, 02:34 PM

Now I'm confused. What is an SPL meter, where do I get it and how do I attach it? Thanks

Originally Posted by sy_lu

Distance only affect time delay. You do need proper time delay for rear speakers for the correct sound effect. You also need to set/balance sound level using a SPL meter. Some receiver can do auto setting you may still need to manually adjust them a little.

**N. Abstentia** · 10-03-2004, 02:40 PM

SPL meter = Sound Pressure Level meter. It measures how loud something is. You can get a cheap one at Radio Shack or just go to ebay and search for spl meter.

**Lensman** · 10-03-2004, 08:06 PM

Originally Posted by hershon

I nominate myself for stupid question of the year, but if anyone is in a charitable mood, please give me some pointers on this. Specifically, I just installed a second home theater system in my bedroom & I'm trying to get the sound (volume) balanced. The rear speakers are on my nightstands about 2-3 feet from me on my bed and the satellites are on my dresser, about 17 feet from my listening position on the bed. I set the distance at about that on my receiver speaker configurations and while the balance is OK its not great.
Do these distance settings on the receiver actually effect the volume from the speakers? If so, is the following applicable- the closer the distance set, the lower the speaker sound & the longer the distance set, the louder the speaker sound. Any pointers you'd recommend & or are there any general rules on this, such as add/delete actual feet when configuring on your receiver?

Not a stupid question at all. In fact it's a fairly complicated one. But knowing the answer will greatly improve your sound. So here's the nickel tour:

A surround sound system works to create an encompassing 3-D sound field that can accurately simulate how things would sound if you were hearing them in the real world. Yeah, basic stuff. But to make this convincing, settings need to be adjusted on your receiver to insure sounds played through the speakers you've set at different distances from your listening position and in different place in your room will arrive at your ear at the right times and at the right volumes to make your ears believe things are all around you equally.

Let's start with your distance settings and use an example. Say a jet flies by (front to back) in a movie. Your front speakers will play the jet's sound, then relay the sound to your surrounds in the back. Since you're farther away from your back speakers, their sound will take more time to arrive at your ears than the sounds from your front speakers. As sound travels roughly 1,100 ft/sec., this time difference is actually very small (as in milliseconds). But your ears DO notice it and it makes a big difference in where you think the plane is.

The distance setting is used by your receiver to correct the timing of when your speakers play the sounds assigned to them. It does this by setting delays based on how far away your individual speakers are located from you. Unadjusted, sound delays from your back speakers will take too long to arrive at your listening position because they are farther away than your fronts. The result could sound echoed and unnatural, and images in your soundfield won't sound like they're where they're supposed to be. If you moved your back speakers closer than your fronts, the unadjusted delay would be too short and things would sound too flat and 2-dimensional. Setting your receiver with the right distances will give you the correct impression of the front to rear fly-by because the sound is will be in the front speakers, then the back ones at the right times.

To do this, place yourself in your primary listening position, then measure how far away you are from each speaker. This is the distance you need to put into your receiver for each speaker. Most receivers round this to the nearest foot.

You can also improve the realism of your soundfield by adjusting the placement of your speakers. The following link shows Dolby's recommended positions for speakers in a 5.1 setup:

http://www.dolby.com/consumer/home_e...oomlayout.html

I'm not sure why they don't mention this anymore, but they used to recommend your surrounds be mounted 2-3 ft. above your ear. I have mine currently at about 1.5 ft.

With your speaker distances properly set, it's now time to fix your balance problem. All things being equal, when you set the volume on your receiver to a specific level, you should hear any speaker play it at the same volume. But the placement of your speakers and the acoustics of your room can change how loud each speaker actually sounds. For example, speakers placed against room boundaries such as walls or corners will generally sound louder than ones placed far away from anything. In fact, even the top of your dresser has an effect on the way your surrounds sound.

So how do you correct this? Most receivers have a "test tone" in their setup mode where they play white noise briefly through each speaker. When you're in this mode, you can set the volume of each speaker up or down as it plays the tone. Each speaker will then actually play louder or softer as you tell it, but combined with the surrounding acoustics, you'll hear them all at what sounds like the same volume after you've made the adjustments. Though you can do this by ear alone, it can be difficult, especially when speakers are only off by 1 or 2 db from what they should be. Three decibels are generally considered to be the smallest amount of change in volume the average ear can detect, which is why you see a lot of speakers rate their frequency response +/-3 db. But even smaller variations in volume in a surround soundfield can leave you feeling something isn't quite right.

The easiest, most accurate way to set the volumes is to measure the sound pressure levels coming from each speaker. Hence the mention of an SPL meter. Radio Shack's meters are routinely recommended as they're readily available at any Radio Shack and tend to be cheaper than SPL meters from other companies. The RS SPL meter is a handheld device available with an analog meter for $39.95 or a digital readout for $49.95. The digital readout is easier to be more precise with, and for my money, is well worth the additional 10 bucks. With the SPL meter, you can get a reading of the effective volume of each speaker from your listening position, then use this to adjust the volume of each speaker. For example, you may read the test tone as 72 db from your front left, 70 from your center, and 69 from your front right. Now you can go back and set the front left for -2 db on your receiver, leave the center at 0, and change the front right to +1 and they'll all sound like they're playing at an equal 70 db. Make sure you use the "C" weighting, and set for "slow".

Here's links for the two meters mentioned:

http://www.radioshack.com/product.as...t%5Fid=33-4050
http://www.radioshack.com/product.as...t%5Fid=33-2055

Hope this helps.

**hershon** · 10-04-2004, 07:15 AM

Thanks alot for taking all the time involved to write this up. I appreciate the detail and clarity and will be using your info as my guide. I salute you. Thanks again

**Sir Terrence the Terrible** · 10-04-2004, 09:56 AM

I hate to do this because so many people get so offended, but Lensman explaination is very good, but some points need to be spotlighted.

Your front speakers will play the jet's sound, then relay the sound to your surrounds in the back. Since you're farther away from your back speakers, their sound will take more time to arrive at your ears than the sounds from your front speakers. As sound travels roughly 1,100 ft/sec., this time difference is actually very small (as in milliseconds). But your ears DO notice it and it makes a big difference in where you think the plane is.

The speed of sound at sea level is 1116ft/sec(small potatoes from Lensmans number). A jet is not really a good example because it fly's over our heads, and HTR effects make it extremely difficult to ascertain direction overhead. A better example would be a car, since it is more on the plane of our ears, and it includes what our ears hear prominently, a floor bounce(or street bounce or close reflection) . The basic reason for delay is to properly time align the arrival of the different signals(from different directions) to the ears. Since most of the time your SURROUND speakers are closer to the listening position(and often different distances from one another) than the fronts, it is necessary to align those for time alignment to the fronts. If you are able to setup your surrounds with an equi-distant position to the fronts(and each other), delay should not be used(because its another level of processing)

As for delay on the front speakers, this is critical, even more critical than the surrounds. I say this because hometheater is generally a front loaded system(most of the output comes from the front of the soundstage) Generally when people setup their front speakers, they setup along a straight line with the center speaker. This will make the L/R mains slightly farther from the ears than the center. Either the L/R mains need to be physically aligned(placing them in front of the plane of the center) or electronically aligned via delay. If you can physically align them(all three physically equidistant to the listen position) do not use delay. Just like my comment on the surrounds, it is a extra layer of processing.

Once again, good explaination Lensman!

**Lensman** · 10-04-2004, 08:54 PM

Originally Posted by hershon

Thanks alot for taking all the time involved to write this up. I appreciate the detail and clarity and will be using your info as my guide. I salute you. Thanks again

The pleasure is mine. Please let us know how things work out. If you decide pick up an SPL meter, there's some additional info I'd be happy to pass on regarding room acoustics and calibrating your subwoofer.