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Sweet spot at 38% tolerance either way?
Old 13th September 2020
  #1
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Sweet spot at 38% tolerance either way?

Hey I am just trying to work out which compromise would benefit me greater here please.

I have a new space which is 2.4m tall 3.7m wide 4.3 long.

I have my monitors (Genelec 8020c) setup 20cm away from the front wall (narrow wall 3.7m)

I have them setup so they are spaced in the middle of the room 1.25m apart and my listening position is 1.25m away to create the 60degree triangle.

This means my listening position is 1.4m away from the front wall.

According to the 38% rule I should be 1.6m away from the front wall. So the question I have is...

My Genelecs could move another 20cm away from the front wall and I move my listening position accordingly but what other issues would that introduce?

Genelec say a max of 60cm away from the wall so I would be under that threshold OR am I over thinking it and 20cm isn't that big of an issue?

OH and one final question. The height of the monitors, I have set them up so they aren't centred at 1.2m as that would be perfectly in the middle of the height of my room, is this a factor to take into account? I have centred them at 1.07m.

Thanks people.
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Old 13th September 2020
  #2
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Northward's Avatar
38% is not and never was a rule. It's not even a particularly good starting point.

The idea that 38% distance is special doesn't make any sense. It won't fix anything.

Forget about it.

Acoustics is about managing sound in time. Fix your time domain by managing your boundaries and the rest will fall into place as a result.
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Old 13th September 2020 | Show parent
  #3
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Quote:
Originally Posted by Northward View Post
38% is not and never was a rule. It's not even a particularly good starting point.

The idea that 38% distance is special doesn't make any sense. It won't fix anything.

Forget about it.

Acoustics is about managing sound in time. Fix your time domain by managing your boundaries and the rest will fall into place as a result.
Lovely, very philosophical.

Have you any suggestions for the best location for the sweet spot based on my room dimensions.

I have to form a triangle that means my monitors and me are 125cm apart.( I have a door to the right of the right monitor on the front wall)

Thankou.
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Old 13th September 2020
  #4
Old 13th September 2020 | Show parent
  #5
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Northward's Avatar
Quote:
Originally Posted by Muskman View Post
Lovely, very philosophical.

Have you any suggestions for the best location for the sweet spot based on my room dimensions.

I have to form a triangle that means my monitors and me are 125cm apart.( I have a door to the right of the right monitor on the front wall)

Thankou.
The only thing you can do if you want a real answer is to take the time to calculate it. Takes a few hours but it's worth it.

It's simple, will require a basic pocket calculator functions and speed of sound over distance and difference of distance between direct and reflected sound paths as a variable (usually called the "Delta" between time variables).

With that you can easily determine what's going on and what compromise you're getting yourself into. Draw simple sketches and graphs. You will see how it's all changing and where the response is maybe better (but again, your global time domain response / decay time will remain globally just as it is)

Doing that in parallel to using software like REW is eye opening.

The actual solution is treatment at the boundaries though. Location of speakers is very much intertwined with that.

You will also notice that a good starting point in a lot of cases is with the speakers right against the front wall. The bass boost you get is pretty much minimum phase, so for once you can simply use a shelf EQ to compensate for it. And that way you take some of the reflections out of the equation and push some issues way up in the midrange where they are much less noticeable, depending on speakers cabinet size and dispersion characteristics.

Only when a room acoustics "problem" is minimum phase can EQ be used to compensate.

Otherwise, if not minimum phase which are 99.9% of room acoustics problems: the physics of it is that you can't fix a time domain problem in the frequency domain. Because the frequency response in the room is a function of the time response. Time = phase. Putting an EQ doesn't fix a phase issue. It still cancels or sums up (and rings), whether or not you add or remove energy.


Contrary to the 38% thing, that is a very real thing.

If you don't want to do it, there are some websites around that can help with basic estimates like these. A quick Google search will yield a lot of results.
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Old 14th September 2020
  #6
Lives for gear
If you are not familiar with acoustics, it's easier to measure your room response using REW rather than calculate it, specially if you already have a defined space IMO.
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Old 14th September 2020 | Show parent
  #7
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Quote:
Originally Posted by JayPee View Post
If you are not familiar with acoustics, it's easier to measure your room response using REW rather than calculate it, specially if you already have a defined space IMO.
I just did this now. With a blanket across my desk and with my normal setup with synths etc in front of me.

Brown with blanket green without.

Just trying to get some help on interpreting these recordings somehow!\
In the file I have recorded the speakers individually too.
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Old 14th September 2020 | Show parent
  #8
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Northward's Avatar
Quote:
Originally Posted by JayPee View Post
If you are not familiar with acoustics, it's easier to measure your room response using REW rather than calculate it, specially if you already have a defined space IMO.
Yes and no... I see what you're saying but calculating makes what you see on REW a lot better/easier to understand and process.

I see too many people endlessly moving their setup hoping to get a better result almost exclusively counting on... Luck. Random trial and error.

A lot of time wasted, and unrealistic expectations (a byproduct of the "flat line" syndrome often witnessed on forum like this one for decades) can add difficulties and a lot of frustration to the process.

If you know your parameters because you ran the basic numbers, you know whether or not you've realistically reached the potential of the current space.

From there you can better decide what the next step is.

REW is great, I use it too. But it's like flying blind if the given conditions and correlations aren't well understood. It's simply and only a (great) verification tool.
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Old 14th September 2020
  #9
Lives for gear
100% agree, if the OP knows how to do it, it's the best method.

Just wanted to suggest a dirty and quick approach.

As you said, it's very relevant when you match the numbers and the measurements.
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