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PostPosted: Thu Jan 17, 2013 8:30 pm 
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Joined: Thu Jan 17, 2013 5:00 pm
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Location: Hong Kong
Greetings to all, this is my first post here and I would really like to say thanks to all who constantly contributes to wealth of knowledge in studio design/construction. I have learnt quite a lot here in a short period of time. :mrgreen:

Concerning soffit/flush mounting, I think I have acquired some basic ideas but I still have a lot of confusion on it. I believed that most of the questions I would be asking are just beginner's question! Let me first begin to speak of my concept of soffit mounting so you guys can correct me if somethings isn't right. (I would use non-technical terms because I’m not sure about the nuances of the meaning of those terms.)

Soffit mounting means you construct an artificial wall (or panel) and leave an opening for you to place your speaker in. The wall is a front panel which act as a big big baffle (as an extension of the original speaker baffle). Generally it give a better listening experience as in enhancing the bass, reducing unwanted effect of soundwave emitting from the rear of speaker..etc.

A box is constructed for the speaker to put in, the speaker should fit in tightly (here I have some question here, “tightly” means the height and width of the opening is same as the speaker?) and leave some airspace behind. Vent can be made on the box for ventilation. After considering the angles of the speaker to the listener, a wall is built according to this angle. Inside this wall, at certain height (so that the tweeter is at 1.2m above the ground), a horizontal surface is constructed for the speakers (in the box) to sit on. This surface also separate the upper half and the lower half. An opening is made on the wall where the speaker can be inserted to the flat surface. The unoccupied space at the upper half is filled with insulation material (e.g. rockwool), while the lower half is occupied by a hanger to act as bass trap. An opening is made at the bottom and top of the wall for ventilation.

I know there must be something wrong or incomplete in my understanding, please point that out. And here are some questions.

1) I notice that people talk about decoupling from the front panel (or from other things), so what exactly is it? Does it mean that I need to add some insulating material between the bottom of the speaker and the box so that it is “decouple” from the whole soffit structure?

2) should the speaker touch any side of the box? If it is touching the sides of the box, isn't it not decoupled?

3) Some people mentioned there is a stand (e.g. a brick stand extending up from the floor) for the speaker to sit on, what is it different from having a flat surface that is built onto the internal structure of the soffit. (like the design by John)

4) Does the "extended baffle" means the whole “wall” from ceiling to floor? Because when I look at John’s design, the upper half and lower half “wall” seems different? So which part actually act as the “extended baffle”?

5) Does the insulation in the soffit structure act as a normal “bass trap”/”superchunk”/”absorber” like those typical triangular absorber that is placed at the corner of the room?

I know some of my question might seem very silly or do not make any sense at all, but I would really appreciate if anyone can make my muddled mind clearer. Thanks in advance! :D
Hope to start my own studio project soon!


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PostPosted: Wed Jan 23, 2013 10:53 pm 
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Joined: Mon Sep 24, 2012 9:12 am
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Location: Munich, Germany
I guess you did not read the rules thoroughly, as you did not specify you location. I am myself building the first soffit in my studio, so I am not the right person to answer your question, as others have more knowledge about it. Read the rules and I am sure someone will answer your questions ... :-)


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PostPosted: Fri Jan 25, 2013 9:43 am 
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Location: Santiago, Chile
Hi "locyedwin". Please read the forum rules for posting (click here). You seem to be missing a couple of things! :)

Anyway...

Quote:
The wall is a front panel which act as a big big baffle (as an extension of the original speaker baffle).
Exactly. Technically, it is called an "infinite baffle", but of course it isn't actually infinite in the real world.

Quote:
Generally it give a better listening experience as in enhancing the bass, reducing unwanted effect of soundwave emitting from the rear of speaker..etc.
Yes, but the biggest two issues are that it restores the correct power balance of the speaker itself, and eliminates SBIR.

Quote:
A box is constructed for the speaker to put in, the speaker should fit in tightly (here I have some question here, “tightly” means the height and width of the opening is same as the speaker?)
Personally, I prefer to have rubber between the speaker and the box, to decouple the actual speaker cabinet form the rest of the soffit as much as possible.

Quote:
Vent can be made on the box for ventilation.
Yes, you do need a vent, especially if you have active speakers, but even for passives it is important.

Quote:
After considering the angles of the speaker to the listener, a wall is built according to this angle. Inside this wall, at certain height (so that the tweeter is at 1.2m above the ground), a horizontal surface is constructed for the speakers (in the box) to sit on. This surface also separate the upper half and the lower half. An opening is made on the wall where the speaker can be inserted to the flat surface. The unoccupied space at the upper half is filled with insulation material (e.g. rockwool), while the lower half is occupied by a hanger to act as bass trap. An opening is made at the bottom and top of the wall for ventilation.
That's basically it yes! You seem to have the correct idea.

Quote:
1) I notice that people talk about decoupling from the front panel (or from other things), so what exactly is it? Does it mean that I need to add some insulating material between the bottom of the speaker and the box so that it is “decouple” from the whole soffit structure?
You can do that too if you want, yes. There are other design concepts for soffits, but personally I prefer a combination of Barefoot's design and John's design: Barefoot decouples the speaker from the soffit as much as possible, and John makes use of the space underneath for hangers and absorption.

Quote:
2) should the speaker touch any side of the box? If it is touching the sides of the box, isn't it not decoupled?
Exactly! Two different concepts. John holds everything very rigidly and tightly in place, Barefoot decouples the speaker from the infinite baffle. Both concepts work. And they can be combined...

Quote:
3) Some people mentioned there is a stand (e.g. a brick stand extending up from the floor) for the speaker to sit on, what is it different from having a flat surface that is built onto the internal structure of the soffit. (like the design by John)
That's simply a variation on how the speaker is supported. Solid brick means that it is rigidly held in place, but the bricks do take up the space where you can have hangers, which are very useful.

Quote:
4) Does the "extended baffle" means the whole “wall” from ceiling to floor? Because when I look at John’s design, the upper half and lower half “wall” seems different? So which part actually act as the “extended baffle”?
The baffle is "infinite" in theory only. As long as it is very large with respect to the original tiny baffle on the speaker, you will get the right effect. John's baffle goes down almost to the floor: there is an opening at the bottom about a foot high, to the hangers, but above that opening is a shallow "box" filled with insulation. The insulation helps deal with reflections off the rear of the desk and console, and the box is an extension of the baffle. That far away from the speaker, it doesn't matter that there is a slight "step" from the baffle panel to the rear panel of the box. And in any event, the sound waves from the speaker are basically moving along the surface of the soffit, and since the angle of incidence to the absorption in the box is basically 90°, there isn't much absorption happening there anyway: Absorption drops off quickly for high angles of incidence.

Quote:
5) Does the insulation in the soffit structure act as a normal “bass trap”/”superchunk”/”absorber” like those typical triangular absorber that is placed at the corner of the room?
You mean the absorption in the top part of the soffit, around the speaker itself, in Johns design? No, that just damps the resonance inside the cavity, and in general absorbs a bit of the sound.

Quote:
I know some of my question might seem very silly or do not make any sense at all,
Not at all! Soffits can be pretty complex, and there are different design concepts that seem to contradict each other, but in reality they don't. They are just different approaches to the problem.

You might find these threads helpful:

viewtopic.php?f=2&t=839&p=10842&hilit=rigid+thomas#p10842
viewtopic.php?f=12&t=718&hilit=soffit


- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.


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PostPosted: Fri Feb 01, 2013 12:46 am 
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Joined: Thu Jan 17, 2013 5:00 pm
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Location: Hong Kong
Thanks stuart, you helped to make things more clear!
There is still much to learn, and thanks for the info.

And I think I have fixed "the missing thing" already haha


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PostPosted: Fri Feb 01, 2013 12:51 am 
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Location: Santiago, Chile
Quote:
And I think I have fixed "the missing thing" already haha
Yup, that was it! And feel free to ask more questions, and also to post your soffit design / build details here, firstly so we can see if there are any ways of improving it, and secondly to document it as you build it, since that is very helpful for others in the future.

- Stuart -

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PostPosted: Fri Dec 05, 2014 7:39 pm 
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Joined: Fri Dec 05, 2014 7:26 pm
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I think I will have to experiment with placement of free mounting 824s and perhaps get a decent pair of speaker stands, struggling to get a good stereo image with them.


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