Room diffusers are the answer for the dreaded “flutter echo”. As discussed in earlier blogs, these evenly spaced repeating of sound waves greatly interferes with the listener’s ability to hear clean clear audio from a speaker, stereo or live performance.
If you have deep pockets; or a large budget, there are lots of commercial solutions to this major acoustic dilemma. As always, ask questions and do your research about products and the firms that sale those diffusers. For those who are willing to put in the sweat equity I will lay out some solutions that will greatly reduce flutter echo in any room no matter its size.
SHELVING
The simplest of all solution to flutter echo in a room is to put up shelves or shelving units. Shelves are not only a great storage solution, but they also work well for helping eliminate evenly spaced repeating waves of sound (flutter echo). How?
The cause of this problem are hard parallel walls or parallel hard floor and ceiling, shelving helps change the profile of the rooms walls, eliminating the ability of the sound waves to form evenly space repeating of themselves. When you put up the shelving (or whole units) make sure that each set of shelves are offset from other shelves (regardless if they share the same wall or on opposite walls from each other) a minimum of six inch offset (high or lower) will do the trick. The more objects place on the shelving, such as books, stereo equipment etc. will add to the irregularity of the wall(s), which in turn will improve the sound quality of the effected room.
CURTAINS
One of the other easy to do solutions is hanging curtains over one or more walls. The curtain material should be a heavy weave; some great materials are wool, wool blends or burlap. Both these materials have unique smells. The “burlap odor” just as that of untreated wool, it is very noticeable, but this will fade away over time. Or you can impregnate the material with any interior paint. When the fresh paint smell fades off in a few days, the burlap smell will be eliminated. Pleating the curtains helps greatly in giving the covered wall an irregular profile. The slowing of the sound waves as they travel through and back thought the material helps eliminate the sound waves ability to produce flutter echoes.
CARPETS
Placing carpet on the wall will have the same effect as curtains. If you have a parallel ceiling to the floor, putting down carpet on the floor will change the floors profile, this will help to reduce the ability of sound waves bouncing off the ceiling and floor becoming evenly spaced. If possible, make sure to place carpet padding on the floor before laying down the carpet, this will add in slowing the sound waves. In this case, the thicker and deeper the carpet, the better. (Where is that funky old shag carpeting from the 70s when you need it?)
These measures are the easiest and the most cost effect measures to combat the dreaded flutter echo.
Next week’s blog: Building diffusers part II- How to build your own diffusing devices from scratch
NOTE TO READERS: The measures that I will discuss in this week’s blog are things that can be employed by anyone. Including those that consider themselves as the “non-do-it-yourself type.”
The great part is, that these room acoustic improving measures (excluding the purchase of speaker wire) are free of cost!
ROOM SPEAKER PLACEMENT
We have so far in the “Sound Advice” blog discussed the main acoustic problems rooms can suffer from, some corrective measure to solve these problems and how to test for acoustic problems.
A great but often overlooked way to improve the acoustic sound quality of your room is the placement and positioning of your speakers. The placement of speakers in your room greatly affects the tonal qualities and realistic sound reproduction of the audio your ears will perceive.
PLACEMENT OF TOWER (FLOOR) SPEAKERS
Tower speakers should be place at least a minimum of 12 inches out from the wall. This will allow the speakers to deliver optimal sound quality.
What happens if you place your speakers closer than the recommend minimum?
The closer to the wall you place your speakers the duller your middle and upper lower range sound tones become. With that said, if you have tower speakers in the lower price range category, that have small bass speakers, placing them closer to the wall will deliver a move powerful low range response.
If your towers have a two or three way speaker setup, they normally have separate controls on board for fine tuning your High-end, Mid-range and bass speaker. You will need to increase the level settings of your mid-range speaker to help compensate for the dullness created by you, when you ignore the minimum placement recommendation.
You will also want to be mindful of furniture placement. Avoid placing couches, love seats or chairs directly on the wall opposite your tower speakers. The wall apposing your speakers will reflect a lot of the speaker’s sound waves back into your ears from your rear, resulting in the delivery of over saturated bass response and poor overall sound quality to your ears. If you don’t have the space in your room to move your couch, love seat or chairs at least two feet from the wall, the placement of a wall hanging made out of thick fabric will help increase the quality of the sound your ears receive.
While shelving in your room serve help the overall acoustics, by acting as a natural sound diffuser, those really nice glass and glass top coffee tables can add unwanted reflection of the higher sound frequencies, especially when you crank up the volume on your sound system. To reduces this negative factor, you should cover the glass surfaces with a sham. My suggestion would be to use a sham made out of wool or a heavy cotton weave. You should also be aware, that windows pose an even greater problem of unwanted sound reflection, much more then glass tables and glass table tops, since they have a greater surface area. Heavy drapes or curtains are a very effective solution to this problem.
Another problem many people face, is the placement of their speakers next to their television, beside the power of the magnets from your speakers effecting the television’s picture. The sides of the television can cause and unwanted sound reflection effecting the room’s acoustics. The simple solution would be not to place your speakers next to your TV. If that is not an option for you due to your room’s layout, then the next best thing is to move your speakers forward, so they are no longer parallel with the sides of your TV.
SPEAKER ANGLING
Another great away that won’t cost you a penny to positively effect your rooms acoustics, is a technique called “Speaker Angling.” I used this myself to help out my friends at the “911 Media Arts Center” in Seattle, Washington, using this simple technique improved the acoustic profile of their theater and greatly reduced the level of flutter echo.
Instead of placing your speakers so they face the apposing wall, you will be angling the speaker toward each other. Using this technique can dramatically improve the sound quality that the speakers deliver to the listener’s ears, by reducing the area of initial sound reflections off parallel side walls or opposing wall ( which is the cause of flutter echo).
You will need an additional person beside yourself to employ this technique. First, sit yourself faces your speakers, then have the person helping you turn the speakers toward each other. You will hear the flutter echo decrease as the speakers are angled in toward each other. What you are listening for is, the “Magic position,” this is the point where there is the least amount of “flutter echo” and the best treble, mid-range and bass response.
There are is no set angle to set your speakers. Though, I find most people find their “magic point” some where between 5-45 degrees. It really depends on the speakers and size and dimension of your room as to how far in you will need to turn your speakers.
USING THE CORRECT SPEAKER WIRE
Another important factor in the delivery of good sound quality is using the proper gauge of speaker wire. In some cases, you just don’t have a choice in this matter, as some speaker manufacturers only sale pre-wired speakers. Then it becomes a matter of how far from the sound source you can place your speakers, based on the gauge of the speaker wire supplied by the manufacture.
I have seen wire as thin as 22 gauge used by some manufacturers of low price speakers. Most speaker wire world wide range from 20-12 gauge. The “gauge” is the thickness of the speaker wire. The lower the gauge number, the thicker the wire. The farther away from the sound source the speaker is drawing its signal from, the greater the loss of signal quality. To compensate for this loss you need to increase the thickness of the speaker wire you are using to deliver the signal to your speakers.
These are my recommend guidelines for the gauge of the speaker wire vs. distance from the source of the sound signal.
less than 10 feet-22 gauge
10-20 feet-20 gauge
20-40 feet-18 gauge
40-80 feet-16 gauge
80-160 feet-14 gauge
more than 180 feet -12 gauge
Next week’s blog will address the very serious problem of “FLUTTER ECHO” by giving “do-it-yourself” solutions to the reader in use of diffusing methods and materials.
TESTING FOR ACOUSTIC PROBLEMS
In previous blogs I have talked about the most common acoustic problems affecting rooms and how to take corrective measures. The only question left, is how you go about testing your room for these common acoustic problems? In this article we will cover some ways of testing for these problems.
The Hand Clap Test
If you have a good set of ears and some patience, there is a test you can employ that won’t cost you a penny, just some time. This test can help identify problematic sound reflections in your room.
The hand clap test:so named for obvious reasons. You will need to stand or sit as close the middle of your room as possible and clap your hands once, listening carefully to how the sound is affected. Do you hear a slow, even decay? Do you hear a single hard reflection? Or do you hear a multiple of closely spaced repeats? These faster echoes are known asflutter echoes and are created when sound bounces back and forth between two parallel walls or a parallel ceiling and floor. Flutter echo is something that you will definitely want to take measures to correct. One of the cheapest way to address the very serious problem is the use of diffusing methods. (this subject will be be covered in two weeks)
USING A SPL METER IN CONJUNCTION WITH A TEST-TONE CD
If you have a little money to spend, a very cost effective tool that you will want to pick up is a SPL meter. SPL meters are devices used to get an exact reading of your rooms sound levels. For most people the easiest way to effectively use this tool is to purchase a test-tone CD. To test your room, take your SPL meter and get as close to the middle of the room as you can, now start the test-tone CD, you will need to write down each number displayed by the meter. It will take around an hour or so to complete the room test. This test will give you a complete picture of your rooms acoustic responses. Now you know what problems your room has (if any) and what corrections to your room’s acoustics you will what to undertake.
If you have a big enough budget there are many high end testing devices and software on the market, just remember to do your research to find the best deal for your budget and needs.
In testing, one important point of information for all of you would be testers, is that each frequency has a different size wave length. How do you go about finding the size of the wave of a frequency? Here is a easy mathematically formula you can use to find the size of the wave of any given frequency: simply divide 1130 (sound travels at the speed of 1130 feet per second through air) by the frequency. As an example, a 100 Hz would be 11.3 feet and a 1000 Hz would be 1.13 feet. The rule of thumb: the higher the frequency the shorter the wave and the lower the frequency the longer the wave.
Next week’s blog: Room speaker placement. In order to deliver the best sound quality to the listener’s ear proper speaker placement is key. This is a no cost measure that even the non-do-it-yourself types can undertake to improve the listening quality of theirroom.