Take out the small room... DONE! Now I have a whole new set of problems. :(

[MarkP]

Hi,
First of all I'd like to thank John & mjbphotos for the feedback and advice.

It's taken a lot longer than I expected to rip out the small room and put things back together.
I have added absorbers to the new large room, but because the room is now square I've run into a new set of problems.

I have placed 6ft x 2ft, 4inch thick absorbers in each corner, added two 2ft x 4ft absorbers behind my speakers and two more the same size on adjacent walls ( used a mirror to position them)
I have also added a 4ft square x 2 inch thick cloud.

Now you'd expect that lot to make a big difference, but it really hasn't because of the shape of the room. I have a massive null around 100hz.
Its so bad if I walk to the centre of the room and bend down so my head is around 4 ft from the ground it completely cancels out.

So, I've experimented with different set-ups. I removed the absorbers from behind the speakers and to the sides and it made very little difference. I then decided to make a monster cloud, so put two pieces of rope
on the ceiling, removed the small cloud and put the four 2ft x 4ft absorbers above my head. You'd think having a 4 inch thick 4ft x 8ft cloud would make a difference... It did, but only by a very small amount.

I've just finished putting together a plan in sketchup that is to scale and I've tried to get the measurements to within a few millimetres of where I have things positioned.
I've also posted my REW results. the measurements were taken in the mix position, one sitting and one standing.


Edit: I can't seem to upload the sketchup files, saying they are invalid? I've posted pong file to look at,b ut will happily email them to anyone interested in helping.





The big question is... Even if I spend thousands on trapping will I ever get this space sounding good, or do I need to go back to the drawing board - Actually, I did play around in sketchup and wondered if it would be cheaper and more effective to just add a couple of stud walls to improve the room ratio. Png's below:





Any thoughts or better ideas than mine would be great,

Many thanks,

Mark

 

[jimmys69]

I am starting to wonder if the two side rooms are creating the issue. Maybe resonating and introducing bigger issues.

JH Brandt- where are you???

I will email him now and ask him if he is willing to help.

 

[miroslav]

A null at 100 Hz ain't all bad....just don't try and make up for it during mixing.

There's a point where unless you plan on ripping down the whole room and rebuilding....you just make the best of it, and do NOT undermine your comfort and the overall space "feng shui".

You can make yourself nuts chasing nulls and whatnot endlessly.
How does the room sound to you?
Play some known music, and see if it translates well or if doesn't.


Personally, I would take the single large room any day, over two smaller ones, regardless of their shape.

 

[RAMI]

Looks like you have nothing at your first reflection points. I might be seeing the diagrams wrong, but that's what I think I see. I'm not saying that this is the problem either way, just pointing out what I think I see.

 

[rayc]

1st reflection points - yep. you need stuff there more than you need it behind your speakers.
If you're considering chages then why not alter the shape of the room asymetrically. the stud walls you've done drawings for are symmetrical and whilst the situation may alter from what you have now it will alter to a new set of issues caused by the symmetry. One of those cupboard like spaces with a pegboard like face, (much bigger holes though) and walls padded with bass aborbing stuff could work as a storage/isoish space and bass trap.
Are the corner bsorbers actually bass traps? If not they need to be - home made is fine as longa s the proportions and spec of the rockwool/etc fibre is correct.
What's happening with reflections from the glass at the opposite end of the room?
You'd actually be better off with your mixing position where the sofa is. A year or so ago I was strongly encouraged to move my mixing position to directly infront of a large set of windows (me facing the windows the speakers away). To me it was counter intuitive but it worked brilliantly. The wall facing my mix poistion has bookshleves stuffed with a wide range of work related book sizes and heights (it's in dewey order not neat order) that act as diffusers.
My space is a small rectangular prism. With shelving, speaker cabs, CD racks (the CDs are alphabetical but with random, frequent CDs poking out, pushed back in etc to also diffuse) and other large shapes the symmetry has been altered and this helped quite a bit. Bass traps in the corners and a cloud waiting to go up.

 

[jhbrandt]

Mark,

Please send me your skp file. > john@jhbrandt.net

Meanwhile, do NOT build the room smaller! Please don't add those side rooms.

Tell me; What is the construction material used in this room/building? Please list: exterior sheathing, shear wall, stud type - OR brick type (double wythe or single), interior surfacing (gypsum board or plaster render)... Also ceiling/roof construction - everything please. And photos too.

According to my calculations for this room, you MUST bring the overall RT60 down to 0.24 seconds with a permissible rise to 0.30 seconds @ 63 Hz... This rise should only begin at 200 Hz and end at 63 Hz. - THAT's a very tight room and if you do that, you'll have an FR like the sim attached. And possibly better.



This requires a full coverage of treatment and absorption down to AT LEAST 30 Hz, which is the lowest axial mode. ** To trap below 100 Hz (and do it well) you will need to analyze the room's mass boundaries and either calculate the pass band OR test to find that pass band (resonance), then design trapping to cover the bandwidth.

The ONLY rooms that can work with 'minimal' treatment like reflection panels are those that have thin walls that allow frequencies lower than 100 Hz to pass without reflecting back. I suspect that your wall partitions are of a more 'solid' material and therefore this room will require substantially MORE absorption, particularly BASS TRAPPING. Please download my paper, 'Room Acoustics Design and the Frequency-Power Spectrum'. (it's on my publications page).

Cheers,
John

 

[MarkP]

Hi, Side rooms not in that was just an afterthought.

 

[MarkP]

A null at 100 Hz ain't all bad....just don't try and make up for it during mixing.

There's a point where unless you plan on ripping down the whole room and rebuilding....you just make the best of it, and do NOT undermine your comfort and the overall space "feng shui".

You can make yourself nuts chasing nulls and whatnot endlessly.
How does the room sound to you?
Play some known music, and see if it translates well or if doesn't.


Personally, I would take the single large room any day, over two smaller ones, regardless of their shape.

Hi, Thanks for your reply.
I really don't want to shrink the room. I've spent years mixing in horrible spaces and I don't want to have to compensate any more, or suffer headphones for hours on end. listening at the moment isn't great. When I play bass heavy material I go from non existent A notes to stupidly loud G's - It's not ideal.

 

[MarkP]

Looks like you have nothing at your first reflection points. I might be seeing the diagrams wrong, but that's what I think I see. I'm not saying that this is the problem either way, just pointing out what I think I see.

Hi,
I used a mirror to position absorbers behind, to the side and above the listening position, so I thought I'd nailed the 1st reflections?

 

[MarkP]

1st reflection points - yep. you need stuff there more than you need it behind your speakers.
If you're considering chages then why not alter the shape of the room asymetrically. the stud walls you've done drawings for are symmetrical and whilst the situation may alter from what you have now it will alter to a new set of issues caused by the symmetry. One of those cupboard like spaces with a pegboard like face, (much bigger holes though) and walls padded with bass aborbing stuff could work as a storage/isoish space and bass trap.
Are the corner bsorbers actually bass traps? If not they need to be - home made is fine as longa s the proportions and spec of the rockwool/etc is correct.
What's happening with reflections from the glass at the opposite end of the room?
You'd actually be better off with your mixing position where the sofa is. A year or so ago I was strongly encouraged to move my mixing position to directly infront of a large set of windows (me facing the speakers away). To me it was counter intuitive but it worked brilliantly. The wall facing my mix poistion has bookshleves stuffed with a wide range of work related book sizes and heights (it's in dewey order not neat order) that act as diffusers.
My space is a small rectangular. With shelving, speaker cabs, CD racks (the CDs are alphabetical but with random, frequent CDs poking out, pushed back in etc to also diffuse) and other large shapes the symmetry has been altered and this helped quite a bit. Bass traps in the corners and a cloud waiting to go up.

Hi, I'd rather not do any more structural alterations if I can Help it. The side rooms were more of an after thought. I did think about having the desk the other end by the glass, but it's not possible because it's the door in to the building.

 

[jhbrandt]

Mark,

I also recommend that you turn to face the side wall... put the glass on your left OR right. not behind you. It will create more acoustic issues behind you.
I look forward to the mdat file... Also please tell us exactly WHERE the speakers are positioned relative to the wall behind them.
Cheers,
John

 

[MarkP]

Mark,

Please send me your skp file. > john@jhbrandt.net

Meanwhile, do NOT build the room smaller! Please don't add those side rooms.

Tell me; What is the construction material used in this room/building? Please list: exterior sheathing, shear wall, stud type - OR brick type (double wythe or single), interior surfacing (gypsum board or plaster render)... Also ceiling/roof construction - everything please. And photos too.

According to my calculations for this room, you MUST bring the overall RT60 down to 0.24 seconds with a permissible rise to 0.30 seconds @ 63 Hz... This rise should only begin at 200 Hz and end at 63 Hz. - THAT's a very tight room and if you do that, you'll have an FR like the sim attached. And possibly better.

View attachment 86577

This requires a full coverage of treatment and absorption down to AT LEAST 30 Hz, which is the lowest axial mode. ** To trap below 100 Hz (and do it well) you will need to analyze the room's mass boundaries and either calculate the pass band OR test to find that pass band (resonance), then design trapping to cover the bandwidth.

The ONLY rooms that can work with 'minimal' treatment like reflection panels are those that have thin walls that allow frequencies lower than 100 Hz to pass without reflecting back. I suspect that your wall partitions are of a more 'solid' material and therefore this room will require substantially MORE absorption, particularly BASS TRAPPING. Please download my paper, 'Room Acoustics Design and the Frequency-Power Spectrum'. (it's on my publications page).

Cheers,
John

HI John,

Thanks for all the info and help.
I'm not at home today, But I'll get the skp file to you when I get back.

construction material used in this room
It's basically a wooden shell.
55mm T&G that interlocks well.
Internally it has 4" stud work attached to the shell.
The walls and roof have 4" rock-wool slab in between all of the stud work. I've used High density. I seem to remember it has a density 45 kg/m³. It's the UK equivalent of the Owens-Corning brand.
On top of that there is a layer of 22mm OSB board, then two layers of 15mm Gyproc Soundbloc Plasterboard (Higher density core.)
Its all been layered up with bucket loads of silicone, around and between the boards.
It's standing on a 5" thick concrete slab, with bitumen sheeting and acoustic matting under the floor boards.

The building does leak a little as I expected when I lined it, but it's not too bad considering the thickness of the walls.

If I can get it as smooth as your calculations show I'll be a very happy man!

I used to be a cabinet maker, (many years ago) so constructing the necessary components shouldn't be too difficult. my problem is knowing what to build? I've looked at all of the expensive foam kits, but I'd prefer to have a go at making my own.

I'm going to download your paper later on and have a good read.

Many thanks,

Mark

 

[MarkP]

Mark,

I also recommend that you turn to face the side wall... put the glass on your left OR right. not behind you. It will create more acoustic issues behind you.
I look forward to the mdat file... Also please tell us exactly WHERE the speakers are positioned relative to the wall behind them.
Cheers,
John

Hi John,

I have two sets of speakers, the back outside corners are 600mm from the rear wall. I have a pair of ns10's that rarely get used and a pair of JBL LSR4326P's. (they are rear ported) the JBL's are spaced just under 6ft apart on my desk. I would like to pull them away from the wall a bit more, but that puts the listing position too close to the centre of the room.

There is a lot of glass in the back wall, so I will definitely have a go at shifting the desk 90 degrees. Probably better against the wall with the smaller window to my right rather than having the large glass doors to my left.

Cheers John.

Mark

 

[mjbphotos]

I've never been real clear on the 'first reflection point' traps - mirror where should show what? In the diagram on page 1, it does seem like the FRP traps are too close to the front corners - after all the speakers don't fire sideways.

 

[MarkP]

I've never been real clear on the 'first reflection point' traps - mirror where should show what? In the diagram on page 1, it does seem like the FRP traps are too close to the front corners - after all the speakers don't fire sideways.

Hi,
Your right it does look weird. The room is very wide, which gives that impression. If you imagine placing your console so that the outer wall is running directly through the centre and then draw a line from your mix position to the right speaker, that is where the panel sits. the mirror saves calculations, just get someone to slide it flush against the wall until you can see the speakers reflection and you should get it in the right place.

 

[mjbphotos]

Hi,
Your right it does look weird. The room is very wide, which gives that impression. If you imagine placing your console so that the outer wall is running directly through the centre and then draw a line from your mix position to the right speaker, that is where the panel sits. the mirror saves calculations, just get someone to slide it flush against the wall until you can see the speakers reflection and you should get it in the right place.

Yeah, I get that but if I am sitting 3 feet from the monitor, then the FRP panel will be on the wall within that 3ft area(if I drew parallel lines from monitor and my seat to the wall). The monitor is not firing sideways 180°, most likely its cone of projection is 90-135°, so the direct soundwaves from it are not hitting the FRP panel at all.

 

[Manslick]

Yeah, I get that but if I am sitting 3 feet from the monitor, then the FRP panel will be on the wall within that 3ft area(if I drew parallel lines from monitor and my seat to the wall). The monitor is not firing sideways 180°, most likely its cone of projection is 90-135°, so the direct soundwaves from it are not hitting the FRP panel at all.

Pretty sure the sound is radiating in a 360° sphere. No?

 

[jhbrandt]

Mark,

Here's a solution for you. By the way, your speakers are WAY too far from the walls. You want to get them right up close to the boundary in front of you (behind them).

(This is for example only!) If you want details, you're gonna have to pay me.. LOL!!

See attached. This is what I would recommend for most home studios. - As Master Yoda said, "There is no try. There is only do or do not."

- I look forward to your questions.
Cheers,
John

 

[mjbphotos]

Pretty sure the sound is radiating in a 360° sphere. No?

Not unless you are using one of those omni speakers with a speaker facing up to a ball top! The reflections bounce all over, but the sound is coming in a cone outwards from the front of the speakers.

 

[mjbphotos]

Mark,

Here's a solution for you. By the way, your speakers are WAY too far from the walls. You want to get them right up close to the boundary in front of you (behind them).

(This is for example only!) If you want details, you're gonna have to pay me.. LOL!!

See attached. This is what I would recommend for most home studios. - As Master Yoda said, "There is no try. There is only do or do not."

- I look forward to your questions.
Cheers,
John

I don't think Mark is planning on converting the room that far .... or has $14,000 for a set of monitors ...