Speaker Asylum

Posted by tomservo (M) on September 06, 2024 at 14:33:01

In Reply to: RE: After getting the room placement do you ever modify your offerings posted by Edp on September 06, 2024 at 10:58:22

Hi
A scratch on the surface;
The late Don Davis once said the purpose of a sound system is to bring the speaker or performer closer to the audience.

I will explain what he meant by that.
Imagine your in a giant empty room like a train station where there is no absorption, all tile.



On a stool right in front of you is a high quality speaker playing a recording of a voice and music. It is perfectly clear and you measure the SPL.

You step back a distance, still sounds pretty good but differnt, spl has fallen and falls at the inverse square law, falls -6dB each time you double the distance.

AS you move farther away, you are hearing more and more of the sound bouncing around the room and as you move farther , the spl stops falling at the inverse square and far enough away, it literally stops falling and all you hear is a jumble that is probably music or talking / has the average spectrum of that.

What your hearing is the transition from the near-field into the far field.
The near field is where the direct sound is louder than the room sound and the far field the converse.

For a loudspeaker to increase the near-field distance requires directivity, that means less sound hitting the walls etc. It is that ability he was taking about to reduce what the room does, as if you were moving closer.

The stereo image is also harmed by reflections, there are no other examples where adding to the original makes it more original.


In the home it's usually the large radiator speakers that have the directivity. The figure 8 pattern of open baffles work especially well keeping it off the side walls and often the rear reflection is far back in time and level


Alternately if speakers have to be by side walls, put a mirror on the wall and while siting on the couch, where you see your speaker in the mirror, put some absorption if you can.
So if you have a live room and can't do anything to it and you have physically small speakers, the alternative is actually to move the speakers closer to you. this does the same thing as directivity.


Remember each time you make the reflections farther than the direct sound, they are also lower in level than the direct sound .
Note that in recording studio's there are often small speaker right above the meter bridge, far from the side walls and close to the engineers ears.
If you have a way to do it with small speakers , try sitting 3 or 4 feet away or to hear how much your room does, set up outside and listen for a while.
Enjoy Audio
Tom

So far as the room design process, in the olden days with those horns, the advice was mount as high as you can and aim at the back row.
Given that the horn had a "lobe" pointing the loudest part at the farthest seat, that made the spl change much less with distance than being on axis up front. The only difference now is our horns are full range, larger and constant directivity.

Now days for big stuff the idea is to make or import a room model and assign a listening plane. Given the space, there are limits to where speakers can go and when you assign those spaces, you can plug in the model for different speakers, aim them, elevate them etc and see what the coverage map is.