imaging???

[newtoitall]

Hi folks,
Well the summer is here and I haven't been able to read much, the boss thinks the summer is for either painting, fixing or gardening. The winter is for computers and loafing around .
Anyway, I was looking through some of my old pamphlets, I own and use as my rears, a pair of Energy 3.1s, they have an 8 inch woofer and a 3/4 tweeter.
In the original folder that came with them it talks about the front baffle around the tweeter being designed to create a larger sound stage due to the reflected sound waves bouncing off the walls next to them. It actually shows the direct sound waves and an imaginary set of waves farther out to the sides and a little back.
Is this the way a larger sound stage is created or is it as you folks put it "snake oil"????
If this is the way speakers are supposed to work, then why do I read so much about controling the reflections???

This may be a silly question, but I am still new to it and am a little confused.

Regards,
Frank

 

[RhapsodyInBlack]

I could be wrong here since im fairly new to the game myself, but i would imagine that they are pointing out that particular set up for those who dont have rear and/or side surrounds. If placed and utilized as you read,it would give the perception of back and side surrounds when there really arent any......again,this is just a guess....

 

[j_garcia]

It's not snake oil. The design of the waveguide for the tweeter is very important to how the sound is radiated and dispersed from the speaker. It's sort of like using a nozzle on the end of your hose to control where the water flows.

You want some reflections, but not all of them. Minimizing them is a good thing, and depending on the room (tile or hardwood floors, etc...), may be a necessary one.

 

[newtoitall]

Thanks for the replies.

RhapsodyInBlack
I do have a suround system but it was only the front mains playing in stereo I was asking about, I should have specified.

j_garcia
How do I know what reflections are acceptable and what ones need to be deadened ?

Thanks
Frank

 

[j_garcia]

What you want is a balance between no reflections and too many. An active room will allow the sound to bounce around too long after the speaker has stopped playing. With the sound bouncing around too much, the sound starts to "smear" because of the delay in the reflected sound. Think of clapping your hands in a racketball court - you hear the clap, but you also hear what sounds like 4 or 5 others echoing afterwards - this is obviously undesirable in a HT system.

 

[snickelfritz]

Thanks for the replies.

RhapsodyInBlack
I do have a suround system but it was only the front mains playing in stereo I was asking about, I should have specified.

j_garcia
How do I know what reflections are acceptable and what ones need to be deadened ?

Thanks
Frank

In a nutshell, you need to reduce as much as possible, the reflections that occur close to the speakers.
Your brain cannot separate these early reflections from the direct output of the speakers, so they get combined into a single blurred image.
It's analogous to double-vision.
Reflections from farther back in the room are sufficiently delayed that they do not blur the stereo image.

The axiom is to place absorbers at the points halfway between you and the speakers on the sidewalls and ceiling, and carpet on the floor.
The area near the listening position is better treated with diffusers rather than absorbers. (tall bookshelves work well as diffusers)
This scatters the reflections and prevents flutter echo from developing, without also creating a dead acoustic.

 

[newtoitall]

snickelfritz

What would be considered

close

when refering to the reflections coming from my speakers?
Can I assume that the distance from my speakers and the side walls will make a big difference in the time it takes the reflections to get to my listening position?

Thanks again
Frank

 

[jaxvon]

Yes, it would. If your speakers are really far from the sidewalls, then there will be a larger delay. However, it is best to treat these reflective points anyway. Primary reflection points along the sidewalls should be your first step (unless you have omnipolar or other similar speakers with wide dispersion). To find the primary reflection point, grab a friend (or significant other) and a mirror. Sit in your listening position and have your friend slide the mirror along each wall until you see the reflection of your speaker. Place an acoustical treatment (be it absorbtion or diffusion) at the point on each wall.

 

[newtoitall]

Once again I apologise for taking so long to get back on line.

jaxvon.
Your little mirror trick seems to have helped, a wall rug in the right place cleaned the sound up a bit.and a little more playing might do wonders.

To all, I really do appreciate any help given though you may not think so when it takes me soooo long to get back to you.
Thanks again,
Frank

 

[snickelfritz]

One established axiom regarding reflections:
If the path of the reflection (from speaker to ear) is shorter than 22' it will tend to mix with the direct output of the speakers, reducing clarity.
This is why sidewall and ceiling reflections usually have to be absorbed.
(most rooms are not large enough to create a 22' reflection path from the speaker to listener; you'd need 16' ceilings and 30' room dimensions)

 

[WmAx]

One established axiom regarding reflections:
If the path of the reflection (from speaker to ear) is shorter than 22' it will tend to mix with the direct output of the speakers, reducing clarity.
This is why sidewall and ceiling reflections usually have to be absorbed.
(most rooms are not large enough to create a 22' reflection path from the speaker to listener; you'd need 16' ceilings and 30' room dimensions)

Actually, >5ms[but less than 10ms] reflection time will tend to be percieved as ambience; which can be desirable, provided that the reflections are close to or identical in spectrum as compared to the direct arrival sound[obviously, this will not occur with most speakers; so in the majority of cases, some diffusion or absorbtion of the 1st reflections will be beneficial]. For the purposes of hi-fidelity sound reproduction, an audible reflection delay with time difference equaling a 22' reflection path[roughly 22ms] may be non-desirable for sound reproduction, as it may not be percieved as ambience, as it will begin to approach the range where it can be percieved[Haas effect] as an interference-like audible delay if high enough in amplitude relative to the source sound.

-Chris