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Does it matter how high a fully absorptive ceiling is? Studio Monitors
Old 23rd April 2018
  #31
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Quote:
Originally Posted by attaboy_jhb View Post
Ok but no ceiling is not possible so 1/4 wavelength is a must for those who want full absorption right?

Then how can ceiling heights of anything less than 14' be acceptable since the lowest frequencies will require over 6' of treatment?
How did you determine that full absorption is required?

All this subjecture in the absence of any intended purpose is rather fruitless. Are you attempting to build an anechoic chamber? A recording room? A mixing room? What is the outer shell of the building?

Generally it seems that in this thread you are hell bent on driving the result that you want...if you don't want other peoples inputs, it's far more simple to not ask for them.

Short answer: most studios are going to be fine without full absorption, in many cases better as fully anechoic environments are neither desirable or practical... Also broadband absorption is not the only choice and many will use more targeted panel or Helmholtz style absorbers to address specific issues...additionally if the walls aren't solid concrete, then you can take into account that some bass is escaping the boundaries as well.


Also to address the random incidence, that accounts only for bass response below Schroeder...I'm talking about the real world issues of treble response above Schroeder- materials that cover insulation are not as acoustically transparent in all circumstances as we would like to think of them, and where diffractions off the surface come into play this is especially an issue in when in close proximity.
Old 23rd April 2018
  #32
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Quote:
Originally Posted by RyanC View Post
How did you determine that full absorption is required?
I didn't but if you have a 10ft ceiling is there really another option?
Old 23rd April 2018
  #33
Gear Guru
Practical Acoustics

A 10' ceiling should have a lowest mode of about 100Hz. We may bandy about 1/4 Lambda in response to complete absorption. But to be reasonable, 0.85 Absorption is often regarded as good enough. This occurs at say 1/10 Lambda.
That plus BBC research showing decent absorption down to 50Hz using 1' traps.

So with these (I wish) 10' and 9' ceilings, 1' of fibre would be a decent treatment.
DD
Old 24th April 2018
  #34
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Quote:
Originally Posted by DanDan View Post
A 10' ceiling should have a lowest mode of about 100Hz. We may bandy about 1/4 Lambda in response to complete absorption. But to be reasonable, 0.85 Absorption is often regarded as good enough. This occurs at say 1/10 Lambda.
That plus BBC research showing decent absorption down to 50Hz using 1' traps.

So with these (I wish) 10' and 9' ceilings, 1' of fibre would be a decent treatment.
DD


Is there a specific height below which it is advisable to have a fully absorptive ceiling?
Old 24th April 2018
  #35
Gear Guru
Siempre

Always. Or I do not understand your question.
DD
Old 24th April 2018
  #36
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Quote:
Originally Posted by attaboy_jhb View Post


Is there a specific height below which it is advisable to have a fully absorptive ceiling?
this is function of the first mode due to the celling.
Old 24th April 2018
  #37
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Quote:
Originally Posted by dinococcus View Post
this is function of the first mode due to the celling.
I don't understand. Could you please explain this?
Old 24th April 2018
  #38
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Quote:
Originally Posted by DanDan View Post
Always. Or I do not understand your question.
DD
In other words, when do we want an absorptive ceiling?
Old 24th April 2018
  #39
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Siempre

When do we not?
DD
Old 24th April 2018
  #40
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Starlight's Avatar
Quote:
Originally Posted by DanDan View Post
When do we not?
DD
a) When the gig is outdoors.
c) In cathedrals built for choirs.
b) In a stone drum room.
Old 24th April 2018
  #41
Gear Guru
UP

1 LOL, there is no ceiling outdoors.
2 Cathedrals are designed to cause long and confusing beautiful droney nonsense, kinda the opposite to what we are doing here.....
3 I would not recommend a reflective ceiling just above the drum overheads.

DD
Old 24th April 2018
  #42
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Quote:
Originally Posted by attaboy_jhb View Post
I don't understand. Could you please explain this?
I answer more quickly, apolo x.

I explain in IMHO : nobody can give you a precise response. We don't know the level of decay and amplitude of your modal reflections.
When you will publish measurements of your room, you will have a response.
Old 24th April 2018
  #43
Quote:
Originally Posted by dinococcus View Post
I answer more quickly, apolo x.

I explain in IMHO : nobody can give you a precise response. We don't know the level of decay and amplitude of your modal reflections.
When you will publish measurements of your room, you will have a response.
It doesn't matter. The OP keeps using the words "fully absorb" but doesn't understand what that means. The only way to approach a fully absorptive ceiling is what myself and DanDan have tried to express, but that information seems to be lost, so I'm guessing the OP doesn't in-fact want a fully absorptive ceiling but isn't aware of how to ask what they actually want, which is an acceptable amount of absorption in a specified frequency or frequency range.
Old 24th April 2018
  #44
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Quote:
Originally Posted by Jeremiah Sheets View Post
It doesn't matter. The OP keeps using the words "fully absorb" but doesn't understand what that means. The only way to approach a fully absorptive ceiling is what myself and DanDan have tried to express, but that information seems to be lost, so I'm guessing the OP doesn't in-fact want a fully absorptive ceiling but isn't aware of how to ask what they actually want, which is an acceptable amount of absorption in a specified frequency or frequency range.
by "fully absorptive" I meant having the ceiling fully covered in absorption not that the absorption absorbs all frequencies. Is that clearer? I understand why it may have sounded confusing before
Old 24th April 2018
  #45
Quote:
Originally Posted by attaboy_jhb View Post
by "fully absorptive" I meant having the ceiling fully covered in absorption not that the absorption absorbs all frequencies. Is that clearer? I understand why it may have sounded confusing before
Yes that is clearer, but now you need to specify why you would want that with the understanding that different frequencies will be absorbed at different efficiencies. You might just end up with a room that's uncomfortablely dead in the frequencies above maybe 200Hz and not tackle the problematic room modes at all.
The unfortunate fact of nature is that the lower your ceiling is, the less room you have to properly do what you are asking without causing more problems, which means you simply have to find other ways. As I've mentioned, the higher the ceiling, the more effective a ceiling full of insulation might be at the frequencies of interest. There gets to be a point where you simply can't work in the room because you've stacked too much insulation on the ceiling and it's not only uncomfortable physically, but also uncomfortable acoustically.

Find the spots where the peaks and dips are most drastic and put a crap-ton (technical term) of insulation there (or other type of absorber). There's a halfway decent chance that it won't be in areas where you actually need to physically be to work. It also won't cause a terribly dead space to work in.
Old 24th April 2018
  #46
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Quote:
Originally Posted by DanDan View Post
When do we not?
DD
well I thought that when you have a higher ceiling you don't get comb filtering as when the surfaces are too close together so you wouldn't have to treat the entire ceiling with absorption. In other words, some reflections from the ceiling might be desirable from a higher ceiling in a live room.
Old 24th April 2018
  #47
But maybe you want a dead space to work in. Give it a shot. Might work for you.
Old 24th April 2018
  #48
Quote:
Originally Posted by attaboy_jhb View Post
well I thought that when you have a higher ceiling you don't get comb filtering as when the surfaces are too close together so you wouldn't have to treat the entire ceiling with absorption. In other words, some reflections from the ceiling might be desirable from a higher ceiling in a live room.
The modes (comb filtering) don't just go away. The first and subsequent modal frequencies drop down as height increases. Get a large enough room and the first couple modes will be lower than the frequency at which you need to work - let's say 40Hz. As you get larger and larger the frequency drops to a point of *almost* zero, but never fully zero. Thankfully the acoustical energy is usually not great enough to cause issues in rooms that large. This is why to FULLY absorb (or fully negate) you need an infinite amount of space... Open air.
Old 24th April 2018
  #49
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Quote:
Originally Posted by Jeremiah Sheets View Post
Yes that is clearer, but now you need to specify why you would want that with the understanding that different frequencies will be absorbed at different efficiencies.
I thought that if you have a ceiling that is low (let's say 10ft in this discussion) and try to record music the sound will sound bad because the two boundaries are too close together (comb filtering etc). Yes the low frequencies are always going to be harder but what other options do you have to treat the low ceiling to floor modes? I know you do get low frequency absorption but have not seen this in ceilings, I thought ceilings in most studio live rooms were absorptive unless the ceiling is really high. Can any reflections that close (10ft) be beneficial in a recording?
Old 24th April 2018
  #50
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Quote:
Originally Posted by Jeremiah Sheets View Post
The modes (comb filtering) don't just go away. The first and subsequent modal frequencies drop down as height increases. Get a large enough room and the first couple modes will be lower than the frequency at which you need to work - let's say 40Hz. As you get larger and larger the frequency drops to a point of *almost* zero, but never fully zero. Thankfully the acoustical energy is usually not great enough to cause issues in rooms that large. This is why to FULLY absorb (or fully negate) you need an infinite amount of space... Open air.
So if you are unfortunate (like 99% of us home studio recordists) to have a low ceiling, what do you do?
Old 24th April 2018
  #51
It depends on how much energy you are putting into a room.

Live room:

If you are recording drums, 10' is a little tight, but certainly doable with a little bit of absorption above the kit. You don't need to absorb anything below maybe 200 Hz (or even higher) and really only at the first reflections points to the microphones. Or maybe it will sound great without any absorption at all! Height is not the only dimension in a room.

Guitars or other close-mic stuff? 10' is ample.

Control room:

Lots of people make 10' work. My current room is 9'. Tackle first reflections down to the frequency that is directional enough to cause comb-filtering. Tackle room-modes with trapping and listening position. Tackle SBIR with speaker placement.

10' isn't that bad, but it could be if not approached appropriately.
Old 24th April 2018
  #52
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johndykstra's Avatar
 

Quote:
Originally Posted by attaboy_jhb View Post
If you have a thick absorptive ceiling with good absorption down to low frequencies then does it matter how high the rigid boundry behind it is? So let's take a 10' and 9' room with the same 1' absorptive ceiling. Does one have a benefit over the other?
Yes, it matters.

The overall cubic footage is a factor, even the space the trap occupies.

Also the proximity of the ear or a microphone to the absorbent material will be closer, thus hearing the reflections that make it an imperfect absorber all the louder.

All speaking hypothetically of course.

Not sure I would want a fully absorbent ceiling. Not as a piece meal solution at least. That's to say a professionally designed control room could employ a fully absorbent ceiling. Thomas' FTB rooms look NE in nature, but even there the ceiling isn't fully absorbent.

I certainly wouldn't want one in my tracking room, but I would love the option in part of it.
Old 24th April 2018
  #53
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Quote:
Originally Posted by johndykstra View Post

Not sure I would want a fully absorbent ceiling. Not as a piece meal solution at least. That's to say a professionally designed control room could employ a fully absorbent ceiling. Thomas' FTB rooms look NE in nature, but even there the ceiling isn't fully absorbent.

I certainly wouldn't want one in my tracking room, but I would love the option in part of it.
good post, kind of the kind I was looking for when starting the thread

So you wouldn't want one even if your tracking room had low 10' ceilings? What would you like on that ceiling in a tracking room like that?
Old 24th April 2018
  #54
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johndykstra's Avatar
 

Quote:
Originally Posted by attaboy_jhb View Post
good post, kind of the kind I was looking for when starting the thread

So you wouldn't want one even if your tracking room had low 10' ceilings? What would you like on that ceiling in a tracking room like that?
Over the whole ceiling? probably not. Certainly an area of it. I'd put the drums under a cloud for close mics and over heads and have the room mic out somewhere in a more lively portion.
Old 24th April 2018
  #55
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When acoustic become a story of sound aesthetic!
Old 24th April 2018
  #56
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12ax7's Avatar
 

Quote:
Originally Posted by dinococcus View Post
When acoustic become a story of sound aesthetic!
'Twas ever thus.
.
Old 24th April 2018
  #57
Gear Guru
Balance

There is consensus on the hard floor. Area rugs, foot noise aside. This adds very early energy. Much later ceiling energy would probably be more interesting, but a mesh floor over anechoic would be impractical! Either way these are the two biggest areas and flutter is a real danger. DD
Old 24th April 2018
  #58
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Hard floor? In this forum. For other and me the floor is treated. For me with Japanese tatami and a rug. For other they uses horn opening at 40 degrees vertically and set in height to avoid reflections du to the floor.
On this forum, the philosophy of the live room is predominant.
There are other kinds of treatments including celling with absorption.
Old 24th April 2018
  #59
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For others and me the floor is treated. For me with Japanese tatami and a rug. For other they uses horn opening at 40 degrees vertically and set in height to avoid reflections du to the floor.
On this forum, the philosophy of the live room is predominant.
There are other kinds of treatments including celling with absorption.
Old 24th April 2018
  #60
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johndykstra's Avatar
 

what is it about the acoustic forum that has people wanting to post in riddle and prose?
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