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Omnidirectional Speakers and Room Acoustics/Treatment

Denosaur22

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Are there unique considerations or recommendations that differ for omnidirectional stereo speakers that should be considered when performing room acoustical treatment?

My understanding is bass frequencies would still require bass traps in the four corners of the room regardless of the type of speaker. But what about absorbers and diffusers? I have a recommendation from an acoustician that I should use all diffusers and no absorbers due to the unique nature of omnidirectional speakers. I was also instructed not to use any treatment on the wall behind or in between the speakers.

I have two Ohm Walsh Super Sound Cylinder 4900s for a stereo setup. Our dedicated TV room is on the smaller side. It is roughly 13 ft x 10 ft. Unfortunately, we did have to set it up on the long axis of the room in this home. That won't be a problem in our next home as we will build a dedicated room with better dimensions. It's a lot of money for acoustical treatment and we want to make sure we get the best bang for our buck.
 

Doodski

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Unfortunately, we did have to set it up on the long axis of the room in this home.
Do you mean the speakers are placed along the long wall or the short wall? The long wall is generally the preferred layout. When the speakers are on the short wall facing down a longer dimension the sound can sound off.
 
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Denosaur22

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Do you mean the speakers are placed along the long wall or the short wall? The long wall is generally the preferred layout. When the speakers are on the short wall facing down a longer dimension the sound can sound off.
Yes. The speakers are along the long wall. Most of the recommendations/diagrams have the speakers placed along the short wall. Is that not right?
 

Doodski

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Yes. The speakers are along the long wall. Most of the recommendations/diagrams have the speakers placed along the short wall. Is that not right?
In most situations the long wall placement is advantageous. When they point down the long dimension they can sound hollow and boomy. If you stand in the corners of the room and speak and clap your hands you can get a feel for this situation. You may need a test subject to stand in the corners, speak and clap so you can stand in the middle of the room and hear the effect. This is a basic simple test to show the acoustics of placement. To show off the acoustics even more have the test subject face into the corner and speak.
 
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Denosaur22

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In most situations the long wall placement is advantageous. When they point down the long dimension they can sound hollow and boomy. If you stand in the corners of the room and speak and clap your hands you can get a feel for this situation. You may need a test subject to stand in the corners, speak and clap so you can stand in the middle of the room and hear the effect. This is a basic simple test to show the acoustics of placement. To show off the acoustics even more have the test subject face into the corner and speak.
I did not know that. Makes me feel better about our arrangement. We didn't really have an option here.
 

kongwee

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Long wall most of the time for me. Having a walking space behind the speaker and sweet spot, also form the triangle to start with. Move the speaker around till it sound right or the best measurement you can get. You gonna have a room, why not take the time to understand the behaviour of your speaker? In future, you can communicate better with your acoustic designer.
 

Doodski

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I did not know that. Makes me feel better about our arrangement. We didn't really have an option here.
The situation is better than a cubed room dimension. Rectangular has advantages. Are you using a PC for a source?
 
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Denosaur22

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The situation is better than a cubed room dimension. Rectangular has advantages. Are you using a PC for a source?
We are using a Blu-ray DVD player, a gaming console, and a Chromecast for streaming content. We have all this connected to an AV receiver. And an amplifier connected via pre-outs.
 

Doodski

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We are using a Blu-ray DVD player, a gaming console, and a Chromecast for streaming content. We have all this connected to an AV receiver. And an amplifier connected via pre-outs.
I was hoping to squeeze in a EQ/PEQ in some sort of computer...lol :D It's the single biggest improvement outside of replacing the speakers. Hardware PEQ exists although I'm not sure your system can manage one because I don't know if it is 2.0, 2.1 etc or surround sound?
 

tuga

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Are there unique considerations or recommendations that differ for omnidirectional stereo speakers that should be considered when performing room acoustical treatment?

You need:
a) a large room and
b) to place the speakers away from all boundaries.

No treatment needed except perhaps for the range below Schroeder.
 
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Denosaur22

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I was hoping to squeeze in a EQ/PEQ in some sort of computer...lol :D It's the single biggest improvement outside of replacing the speakers. Hardware PEQ exists although I'm not sure your system can manage one because I don't know if it is 2.0, 2.1 etc or surround sound?
That's a good consideration. We are using it as a 2.0 surround system. The speakers puts out enough base. In fact, they have a three position switch on the back that allows you to adjust this based upon the room size. But it affects both the base and treble.
You need:
a) a large room and
b) to place the speakers away from all boundaries.

No treatment needed except perhaps for the range below Schroeder.
Unfortunately we don't have a large room... yet. Hopefully in our next home.
 

Doodski

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That's a good consideration. We are using it as a 2.0 surround system. The speakers puts out enough base. In fact, they have a three position switch on the back that allows you to adjust this based upon the room size. But it affects both the base and treble.
Well... The best method is to use a PC as a head unit and install free software for PEQ control. The other option is to get hardware DSP PEQ. That could be done with a miniDSP 2x4 or a miniDSP 2x4 HD (Has a faster computer processor inside.) and also buy a UMIK-1 calibrated microphone so you can use REW a free software to set up your DSP PEQ. The miniDSP unit would go between the receiver and the amp and so all sources could be PEQ'd.
 
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Denosaur22

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That's a good idea. That was one of my next questions! Room EQ. With omnidirectional stereo speakers does it make a significant difference? Worth the investment? More than room acoustical treatment?
 

Doodski

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That's a good idea. That was one of my next questions! Room EQ. With omnidirectional stereo speakers does it make a significant difference? Worth the investment? More than room acoustical treatment?
I can help you with setting up DSP PEQ to a degree although when it comes to acoustics and room treatment I am out of my realm. There are peeps here farr far more qualified than I on those topics. Otherwise PEQ will help any type of speaker. :D
 
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Denosaur22

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Any help is much appreciated! The reason we're looking at room acoustic treatment is that we are having some echo and want to tighten up the sound. I assume that's from reflections or reverberation.
 

tuga

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That's a good consideration. We are using it as a 2.0 surround system. The speakers puts out enough base. In fact, they have a three position switch on the back that allows you to adjust this based upon the room size. But it affects both the base and treble.

Unfortunately we don't have a large room... yet. Hopefully in our next home.

If walls are close then it might be worth to consider placing broadband absorption on early-reflection zones.

See below.
 

tuga

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I've just found the positioning recomendations for your speakers, always a good place to start:

Placement of the loudspeakers in relation to wall surfaces affects bass performance. The closer the loudspeaker is to a wall or corner, the louder the output will be in the range below 150 Hz.

Bringing the speakers away from the front wall will also affect the apparent height of the stereo image. We do not recommend placing the speakers more than two feet away from the front wall. For best imaging, the front wall should be reflective and dispersive – not absorptive.

If you want more treble, rotate the speakers outward. If you want less treble, rotate the speakers inward.


https://ohmspeaker.com/site/assets/files/2452/ssc_4900.pdf
 
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Denosaur22

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I've just found the positioning recomendations for your speakers, always a good place to start:

Placement of the loudspeakers in relation to wall surfaces affects bass performance. The closer the loudspeaker is to a wall or corner, the louder the output will be in the range below 150 Hz.

Bringing the speakers away from the front wall will also affect the apparent height of the stereo image. We do not recommend placing the speakers more than two feet away from the front wall. For best imaging, the front wall should be reflective and dispersive – not absorptive.

If you want more treble, rotate the speakers outward. If you want less treble, rotate the speakers inward.


https://ohmspeaker.com/site/assets/files/2452/ssc_4900.pdf
What would you do to the rest of the walls? Easy enough to make the wall behind it reflective (as it already is). Unfortunately, we have echo and the sound is not as clean or as tight as I think it could be. Probably from reflections and/or reverb? We can always do trial and error approach.
 

Katji

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I have a recommendation from an acoustician that I should use all diffusers and no absorbers due to the unique nature of omnidirectional speakers. I was also instructed not to use any treatment on the wall behind or in between the speakers.
[...]
It's a lot of money for acoustical treatment and we want to make sure we get the best bang for our buck.
Be careful about these experts. Get a second and a third opinion. [Like you are doing here.] :)
 

tuga

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What would you do to the rest of the walls? Easy enough to make the wall behind it reflective (as it already is). Unfortunately, we have echo and the sound is not as clean or as tight as I think it could be. Probably from reflections and/or reverb? We can always do trial and error approach.

Maybe @Bjorn could make a few suggestions regarding treatment.
Personally I would not use omnis unless I could have them clear from the walls.
 
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