Spires rear distance placement with room treatments...

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dmusoke

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Hi All:

I have ML Spires currently approx. 3 feet from the back wall. The back wall high-frequency room treatments from Ready Acoustics (http://www.readyacoustics.com/acoustic_panels.html) that have an absorption range from 250Hz to 20KHz.

Does this mean I can place the Spires closer to the wall since the room treatments absorb and delay the reflected the back wave? if so, how much closer should I be to the wall? I feel at 3 ft the bass suffers since I'm not taking advantage of room corner loading.

Thx,
David
 
David, what are the dimensions of your room ?

IMO, the ideal distance from the wall behind your Spires should be 5-6 feet, yes there plenty of us on here with less(mine are 40" from the top of the stat panel) but increasing absorption so as to further decease that distance makes no sense. If your bottom octaves are not up to snuff, get a good sub (or two) and you'll never look back !
 
18'X20'...

I have 2 sealed subs (SVS SB13 Ultras). I wanted to gauge the bass of the Spires when playing stereo sources only and that's when I found out the bass was lacking and hence the idea for moving them closer to the wall, if warranted.

Is it recommended to place room treatments behind Xstats in general?
 
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Dave is correct.

Five feet to panel front is what I used for 20 plus years on four different ML models.

If you can do this, it "might" allow you to forgo back wall treatments, except for bass traps in the room corners.

Give it a try, you might be surprised.

And to answer your last question, not necessarily.

GG
 
18'X20'...

I have 2 sealed subs (SVS SB13 Ultras). I wanted to gauge the bass of the Spires when playing stereo sources only and that's when I found out the bass was lacking and hence the idea for moving them closer to the wall, if warranted.

Is it recommended to place room treatments behind Xstats in general?

That's a nice sized room, to get the best low-bass, you will definitely need those subs, the Spires alone won't cut it. So I'd focus more on getting the ideal performance out of the Spires from your crossover freq on up and leave the Bass to the SB13's. That said, how and where you cross over, whether you use Room Correction or not and how much room treatment there is will all dictate the quality of the bass performance.

I *always* recommend absorption behind the ESL panel, for one, it does allow you to be closer to the wall behind it as the rear wave gets attenuated in the critical 300Hz on up region that can smear the timing information. See my system for a full detail on how I used multiple tools to achieve a great result.
 
I differ with JonFo on the need for absorption behind the panels as an absolute. That's one reason why I suggest five feet from the back wall.

You may or may not like what they do. In my experience, they can potentially cause the sound to be over damped and somewhat lifeless.

You should certainly experiment in your room, with your gear, using your ears.

You may also want to try diffusion versus absorption. Two very different concepts.

GG
 
I think every room is different. Different sizes, different finishes, different furnishings, all make for different interactions of room, speakers, and listeners. That said, I found that my SL3s sound best about 58" from the front wall. I also found that diffusion (2 RPG Skyline panels behind each speaker) work better than absorption to yield an open and detailed sound. I do use absorption at the first reflection point of each speaker. I have one sub crossed over at about 32Hz. And speakers and sub are corrected in the low frequencies via a DSPeaker Dual Core DRC unit.

I got to this setup--and to a very satisfying sound--only after a lot of experimentation, which is really the point I'm trying to make: you may be surprised how much the sound of your system can be improved by experimenting with various parameters such as wall treatments, speaker and listening position, sub crossover frequency and gain, etc.

Good luck and best wishes for success!

Guido F.
 
Guys:

I appreciate your helpful responses to my question above. I thought the answer would be simpler as I assumed the science would be clearer on this subject. I will try to solicit some advice from the manufacturer as he'd have the absorption data for my panels.

I actually found a youtube video by ML saying 2.5ft is what is needed(http://www.youtube.com/watch?v=ckoqpBmS_mw). This will generate the 5ms delay between the direct and reflected sound that will generate that ambience and depth we are seeking.

David M.
 
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Try what Dave suggested. I had my CLS's 3'-6" to 4' from the wall for years. This was beause I didn't want to have my listening chair to close to the wall behind it but keep a large distance between my ears and the speakers to enjoy a large sound stage.

Last year I pulled them out to 5' even though I was concerned about getting to close to the speakers and not having enough room for the sound stage and image to properly develop. My other concern about being to close to the speakers was that the sound would move to far in front of the speakers and become a near field listening experience.

To my surprise the stage and image didn't move forward at all. I created a much deeper detailed sound field. Do give it a try and see what you hear.

Brad
 
That might be considered as absolute minimum distance as early reflections will smear the timing information of sound. It will however improve with more distance but everything also depends on room acoustics too.
 
Agree with Guido and Gordon. Depends on many variables as they've already said. And with your room being approximately the size of mine, with my experience diffusion gave great results. I used 4' Polys behind each speaker and Summit panels were about 5' off the front wall.
 
The answer to your question is no. Do not move them any closer to the front wall. Not because of the rear wave of the panel, which you are mostly absorbing. But because moving them closer to the rear wall is likely to skew your bass response. Speakers right up next to a wall will generally cause issues in the room's bass response.

As for absorbing the rear wave of the speaker here are my thoughts after years of trial and error with different setups in a similarly-sized room (14'x19'): if you can get the speakers five feet out from the front wall, then you will get the best sound by placing diffusers behind the speakers (I'm talking "real" diffusers, not just books on a shelf or a fake plant or some of the other "homemade" diffusers that don't actually do anything.) If you can't get them at least five feet from the front wall, then you are better off with absorption than diffusion. You will get less width and depth in the soundstage, but you will get much better clarity, details, and imaging.
 
I actually found a youtube video by ML saying 2.5ft is what is needed(http://www.youtube.com/watch?v=ckoqpBmS_mw). This will generate the 5ms delay between the direct and reflected sound that will generate that ambience and depth we are seeking.

David M.

This is wrong, for several reasons. It is just too complicated a subject to get into too much detail, but for starters: 5ms is an absolute minimum, and it will not work in a lot of situations. 10ms or more is required for your brain to fully separate the initial wave from the reflection. This is also influence by the strength (energy level) and directionality of the rear wave. If you have a flat hard front wall, the bouncing wave will have full energy and will be coming fom mostly one direction (reflecting off back and then side walls to hit the ear from that direction) and in that case you may need more delay to separate the sounds. But in the case where you have diffusers on the front wall, the rear wave is broken up and scattered in multiple directions and time delays. This results in it having less energy when it hits your ears, and so your brain may be able to separate the signals with a shorter delay. But there are so many variables involved that you really have to do a lot of trial and error to figure out the sonics of each room and setup.

Another interesting thought about this is understanding what the curved panel does to the back wave. It focuses the sound wave to a vertical line behind the speakers, and then the wave "inverts" (for lack of a better description) and expands horizontally. I'm not sure at what distance the sound wave is focused to a vertical line, but I'm thinking if I had my speakers that close, with my diffusers behind, then wouldn't the sound be focused into one of the wells of the diffuser instead of being spread across the whole panel? I obviously don't understand the physics well enough to have a clue what I'm talking about here, but I do find it fascinating. Seems like the horizontal radiation pattern of the back wave of the speaker is almost as important as the time delay when determining the proper distance from the front wall, especially if you are using vertical well diffusers behind.

Regardless, my own experiments in my small room have made it clear that any less than five feet from the front wall will compromise the speaker's performance in some way, regardless of what you treat the wall with.
 
This is wrong, for several reasons. It is just too complicated a subject to get into too much detail, but for starters: 5ms is an absolute minimum, and it will not work in a lot of situations. 10ms or more is required for your brain to fully separate the initial wave from the reflection. This is also influence by the strength (energy level) and directionality of the rear wave. If you have a flat hard front wall, the bouncing wave will have full energy and will be coming fom mostly one direction (reflecting off back and then side walls to hit the ear from that direction) and in that case you may need more delay to separate the sounds. But in the case where you have diffusers on the front wall, the rear wave is broken up and scattered in multiple directions and time delays. This results in it having less energy when it hits your ears, and so your brain may be able to separate the signals with a shorter delay. But there are so many variables involved that you really have to do a lot of trial and error to figure out the sonics of each room and setup.

Another interesting thought about this is understanding what the curved panel does to the back wave. It focuses the sound wave to a vertical line behind the speakers, and then the wave "inverts" (for lack of a better description) and expands horizontally. I'm not sure at what distance the sound wave is focused to a vertical line, but I'm thinking if I had my speakers that close, with my diffusers behind, then wouldn't the sound be focused into one of the wells of the diffuser instead of being spread across the whole panel? I obviously don't understand the physics well enough to have a clue what I'm talking about here, but I do find it fascinating. Seems like the horizontal radiation pattern of the back wave of the speaker is almost as important as the time delay when determining the proper distance from the front wall, especially if you are using vertical well diffusers behind.

Regardless, my own experiments in my small room have made it clear that any less than five feet from the front wall will compromise the speaker's performance in some way, regardless of what you treat the wall with.

Agree 100%, well written. This is why diffusers don't work in small to moderate sized rooms for almost any type speaker. You cannot get enough of a time delay between the primary and diffused sound, which the brain perceives as a lack of image focus, poor sound stage, etc. The only type diffuser that may work is an absorber/diffuser combo to partially absorb and then diffuse = some delay + some attenuation.

My only comment IMO is that while the back wave focuses the sound (opposite the front) the angle is slight, so the focus point would likely be much farther than most rooms' front wall to the speaker panel (10+ feet?). So if anything, being close to the front wall allows a diffuser behind it to diffuse the vast majority of the wave since it's too close for it to become a single vertical line.
 
But has other serious deleterious affects (low freq in particular)..
 
Agree 100%, well written. This is why diffusers don't work in small to moderate sized rooms for almost any type speaker. You cannot get enough of a time delay between the primary and diffused sound, which the brain perceives as a lack of image focus, poor sound stage, etc. The only type diffuser that may work is an absorber/diffuser combo to partially absorb and then diffuse = some delay + some attenuation.

My only comment IMO is that while the back wave focuses the sound (opposite the front) the angle is slight, so the focus point would likely be much farther than most rooms' front wall to the speaker panel (10+ feet?). So if anything, being close to the front wall allows a diffuser behind it to diffuse the vast majority of the wave since it's too close for it to become a single vertical line.

I have to disagree. Diffuser placed to/near front wall is in the near field of the panel and is receiving quite uniform sound field. Only critical thing is the distance from diffuser to the listener and that hardly can be issue considering average listening distance. Typical diffusers operate down to few hundred Hz and require 3 times wavelength of lowest diffusion frequency which in case 500Hz would be 3*0.69m=2.07m or 3*2.26ft=6,78ft. A skyline diffuser with the lowest diffuse frequency of 500Hz would need to be 34.4cm or 1.1ft. Most common commercial diffusers are only few cm deep and can be placed relatively close to a listener.
 
I have to disagree. Diffuser placed to/near front wall is in the near field of the panel and is receiving quite uniform sound field. Only critical thing is the distance from diffuser to the listener and that hardly can be issue considering average listening distance. Typical diffusers operate down to few hundred Hz and require 3 times wavelength of lowest diffusion frequency which in case 500Hz would be 3*0.69m=2.07m or 3*2.26ft=6,78ft. A skyline diffuser with the lowest diffuse frequency of 500Hz would need to be 34.4cm or 1.1ft. Most common commercial diffusers are only few cm deep and can be placed relatively close to a listener.

I have to disagree with your disagreement! :D

The issue is the time delta between the primary wave and reflected wave. As the speaker gets closer to the front wall the delta between the primary (front panel wave) and secondary (rear panel wave) delivered to the listening position reduces which can cause smearing, sound stage issues, etc. For a dipole this is extremely critical since you have mirror image waves front and back occurring essentially simultaneously albeit out of phase. For a box speaker, it's less critical since there's no rear wave and the majority of sound reflecting off the front wall has already bounced off the rear wall creating a sufficient delay >5 msec.

Also, commercial diffusers range from ~1 inch - 1' in depth depending on the technology deployed and frequency diffusion capability. Skylines are typically ~7" deep - I just made 2.
 
I have to disagree with your disagreement! :D

The issue is the time delta between the primary wave and reflected wave. As the speaker gets closer to the front wall the delta between the primary (front panel wave) and secondary (rear panel wave) delivered to the listening position reduces which can cause smearing, sound stage issues, etc. For a dipole this is extremely critical since you have mirror image waves front and back occurring essentially simultaneously albeit out of phase. For a box speaker, it's less critical since there's no rear wave and the majority of sound reflecting off the front wall has already bounced off the rear wall creating a sufficient delay >5 msec.

Also, commercial diffusers range from ~1 inch - 1' in depth depending on the technology deployed and frequency diffusion capability. Skylines are typically ~7" deep - I just made 2.

Now you confuse me :confused:

Are we even talking about same thing here? Only thing I have said about distance to front wall is that it needs to be more than (someone said 2,5ft) that to get reasonable playback.
Diffusion or no diffusion is another thing. I was trying to say that keep your speakers off from front wall (I prefer 5ft) and that diffusion placed on front wall will be acceptable as distance to listener is long enough. For example: panel 5ft to front wall and listener 10ft to panel, thas shall create 10ft-(5+5+10ft)=10ft delta difference between direct and diffused sound field which gets close to 10ms arrival time difference between direct and diffused sound.
We have to also consider that while sound gets diffused it's energy will be reduced as it will not create as strong reflection towards listener as untreated front wall would. So basically we can consider a diffuser as somewhat absorber for early reflections. This is of course true only for frequencies which are covered by the diffuser by design. Higher frequencies are likely getting somewhat scattered while frequencies below the range of diffuser shall remain unaffected.

Maybe I just misunderstood what you are saying as English is not my first language, not even my second one :p
 
Now you confuse me :confused:

Are we even talking about same thing here? Only thing I have said about distance to front wall is that it needs to be more than (someone said 2,5ft) that to get reasonable playback.
Diffusion or no diffusion is another thing. I was trying to say that keep your speakers off from front wall (I prefer 5ft) and that diffusion placed on front wall will be acceptable as distance to listener is long enough. For example: panel 5ft to front wall and listener 10ft to panel, thas shall create 10ft-(5+5+10ft)=10ft delta difference between direct and diffused sound field which gets close to 10ms arrival time difference between direct and diffused sound.
We have to also consider that while sound gets diffused it's energy will be reduced as it will not create as strong reflection towards listener as untreated front wall would. So basically we can consider a diffuser as somewhat absorber for early reflections. This is of course true only for frequencies which are covered by the diffuser by design. Higher frequencies are likely getting somewhat scattered while frequencies below the range of diffuser shall remain unaffected.

Maybe I just misunderstood what you are saying as English is not my first language, not even my second one :p

I believe we are saying the exact same thing. I agree with everything you just said. So I won't add any more! :D
 

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