John Sayers' Recording Studio Design Forum Archive

Maybe with these you can further comment if this is an SBIR vs Modal issue.

OK, I took a look at your data, and you have both! You very definitely have an SBIR problem of some type, clearly visible in the sequence of readings with the speaker at different positions. And you also have modal issues, but not quite so serious.

Your "50 Hz null" is modal, and it is at 47.8 Hz. almost exactly where it should be for the 1,0,0 mode (predicted: 48.1 Hz). You are sitting in the null for that mode.

It's interesting that as you move the speaker further from the wall, that null does not change at all! Even at the point where the SBIR issue is pumping massive energy into that frequency, there's still a null. Classic case. Key give away. Even SBIR cannot fill in a modal null. The mode just sucks it all out... The next axial mode in the same direction (2,0,0) is also clearly present as a peak, at about 96 Hz, but because it is a peak (not a null) it DOES get eaten by the SBIR issue when the speaker is in the right place. Text book! And the very next version of the same mode (3,0,0) is right there too, as a null, at about 144 Hz. Right where it should be...

So that's why you were confused: You have both modal and SBIR issues, and even though the SBIR can eat a modal peak, it can't fill in a modal null. A null is a bottomless pit: You can pour all the energy you want into it, and it will have no effect on the null.

So there's your basic issue.

The room is also acoustically dead. The overall decay times are around 100 ms, but for that size room it should be more like 230 ms. So it is over-treated with absorption.

If you set up your speakers and listening position correctly, you might be able to get a slight improvement, but it probably won't be huge. You would also need to do something to liven up the room: it's way too dead like it is. It must be uncomfortable trying to mix in there.

But even if you did all that, it won't solve your problem with the ceiling symmetry. You did not show any tests where you did the Left and Right channels separately as well as together, so I don't have any hard evidence for this, but I strongly suspect that you have rather important differences between left and right response. It would be interesting to see a test like that. But to it at 80 dBC for each speaker (meaning that with both on, you will automatically get 86 dBC, which is the "standard" calibration level)

One idea was to convert the live room which is 31'L x 19' 2.5"W x 8' 7"H into a control room. Maybe see if it could work as single room for both recording and mixing. Possibly use the "terrible" room as a recording booth.

That makes a lot of sense. It's a much bigger room, so all of the big issues will be down lower. You should be able to get flatter response in there, but it will also need careful setup.

- Stuart -

I think you can search online for acoustic hangers.


[SPAM SIGNATURE REMOVED BY MODERATOR]

Bambierichard wrote:I think you can search online for acoustic hangers.

I think you can be banned for spamming!!!

Jakob De Wittig wrote:

Bambierichard wrote:I think you can search online for acoustic hangers.

I think you can be banned for spamming!!!

I think you are right, Jakob! In fact, I think that's what happened... Banned, blocked, and spam removed....


- Stuart -

Hey guys,

I flush mounted my very large B&W 808 monitors. I left a 4ft tall section open under the baffle for bass trapping as per John's diagram. I'm considering hangers, versus super chunk treatment in that space. The speakers are on cinder block stands, which does break up the cavity about in half. Since the deepest part of the cavity is 2ft 3 inches deep, and continuously getting shallower until it is only 6 inches deep, I'm not sure I have enough space for hangers to be effective. I think I could get 5 of them hung at a size of 4ft by 2ft, then another 5 or 7 going down in size to only 6" wide by 4ft high. This is per side, since the new wall/baffle dies in the middle of the room. So, I'm looking at about 20 or so rather small hangers across the lower part of the front wall.

Would I just be better off stuffing it with rock wool? That certainly would be less labor, but I'm willing to try the hangers if there is a potentially large benefit. The room itself is well treated, with my nulls being centered at 70hz and up.

Thanks for any advice!

Hi guys!

I've been lurking around for some time now and acoustic hangers seems like a very interesting idea.

I'm interested in treating the back wall of a cellar room - 4 meters wide, 5 meters in length and 2.1 meter in height - by using acoustic hangers.

In your experience, if I make the depth of the back wall treatment 30 centimeters deep and use hangers with a width of 40 centimeters, and hang as many as possible without them touching each other - would the absorption reach down to the realms of 30-35 Hz?

There is a resonance frequency around 34Hz - the lowest standing wave in the room - and it's quite prominent due to the stone walls and concrete floor and ceiling. Instead of trying to build some kind of resonator tuned to 34Hz - which can be a hit or miss - I figure it's better to build back wall treatment that absorbs as much low-end as possible.

The rest of the room is treated with absorbers and bass traps - so it's mainly the back wall that's available for acoustic treatment.

Should I maybe make the hangers 50 centimeters wide to "tune them" to a lower frequency? But then I can't angle them much.

Or should I make them 25 centimeters wide and hang them in 90 degree angle to the back wall?

Due to the layout of the room, I will be able to treat about three meters in width of the back wall. From floor to ceiling.


Any information is highly appreciated!


Cheers
Fred

Hi Fred, and Welcome!

and acoustic hangers seems like a very interesting idea.

And they work! This comment comes from one of my customers who recently installed hangers in his new room: "Wow these hangers are amazing. I have never put a bass trap in and had such a noticeable change in the room."

I'm interested in treating the back wall of a cellar room - 4 meters wide, 5 meters in length and 2.1 meter in height - by using acoustic hangers.

It's a small room, and hangers work very well in small rooms, so they should work for you too.

In your experience, if I make the depth of the back wall treatment 30 centimeters deep and use hangers with a width of 40 centimeters,

I would try to go deeper than that. I normally plan to have about 50cm or 60cm of depth for hangers at the rear, where possible. If you can't afford that much space across the entire rear wall, then at least do it in the corners. And more is better: if you can do, for example, 80cm in the corners but then gradually reduce that to 40cm for the central part of the wall, that would be a good way of doing it.

I usually put 5cm to 10cm if fiberglass insulation directly in the wall, then a small gap, then the hangers from there, as long as I can make them, and angled somewhere between maybe 15° to 35°, depending on the room.

and hang as many as possible without them touching each other -

I do that inside the speaker soffits, yes, but for the rear wall I follow John's method: Place one hanger on the mid-line of the room, not angled, (or two together angled in a "V" shape), then another one almost against the wall (one on the left wall, one on the right wall), angled, then halve the distance between those and place a hanger there (angled), then halve the distances again an place more hangers (angled), then halve again, etc. until I can't get any more in. That places hangers at the full wave nodes, half wave nodes, quarter wave nodes, 1/8th wave nodes, etc. for the room width. It seems to be very effective.

would the absorption reach down to the realms of 30-35 Hz?

It will do something down that low, yes, but it won't be massively effective. That's a very low frequency, and hard to damp, especially if you have a major modal problem there. Damping anything that low, with any type of treatment, isn't easy.

There is a resonance frequency around 34Hz - the lowest standing wave in the room - and it's quite prominent due to the stone walls and concrete floor and ceiling

If that's your lowest mode, then the floor and ceiling are not relevant! It's the 1,0,0 axial mode, and it does not really involve the floor or the ceiling: it only involves the front and back walls.

Have you done a REW test, to determine the exact frequency, and see just how much of a problem it is?

Instead of trying to build some kind of resonator tuned to 34Hz - which can be a hit or miss - I figure it's better to build back wall treatment that absorbs as much low-end as possible.

Right! Exactly! A problem that low is going to need a very large tuned device (panel, membrane, etc.), which would take up most of the back wall anyway, yet it would treat just one single frequency. Not a smart way of dealing with it! Exactly as you said, hangers will deal with ALL modes at ALL frequencies, that involve the rear wall.

The rest of the room is treated with absorbers and bass traps - so it's mainly the back wall that's available for acoustic treatment.

How? Where? What type? How big? How thick? How effective are they? What were your decay times like before you put those in (measured at 1/3rd octave band centers), and what are they like now?

The reason I ask all of that is because a common mistake is to over-treat the mid and high range, simply by having too much bare absorption aimed at the low end of the spectrum. You might need to do somthing to fix that if this is what has happened. If you have not already done so, then please do a full REW test and post the results.

Should I maybe make the hangers 50 centimeters wide to "tune them" to a lower frequency? But then I can't angle them much.

It's not just the width of the hangers that is important, but also the depth that they cover, plus other absorption in the same area. As I mentioned above, I put absorption against the rear wall, then the hangers, and sometimes I put more absorption in front of the hangers. For example, a 5cm or 10cm thickness right across the room, or partly across the room, just a bit in front of the hangers. That can extend the range quite usefully, and also improve the effectiveness. So, for example, I might have 5cm at the back a 2 cm gap, 40 cm of hangers (wider than 40cm, but angled), 2cm gap, then 10cm of absorption at the front, for a total of 58 cm. By the time you add any foils, framing, and finish fabric, that brings it up to about 60 cm. That will go down into the low 30 Hz region quite decently. Getting lower than that takes even more space.

Or should I make them 25 centimeters wide and hang them in 90 degree angle to the back wall?

I would not do that, no. 25 cm is not going to be highly effective, no matter how you hang them. It will do a lot of good, yes, for sure, but to go down low, you need more depth overall.

Due to the layout of the room, I will be able to treat about three meters in width of the back wall

Why only 3m? You said the room was 4m wide...

Please provide a diagram of the room, showing how you have it laid out at present, with dimensions, indicating the positions of the speakers, mix position, other furniture, doors, windows, etc.

And photos! It really helps us to understand your room better if you post photos of it.


- Stuart -

Thanks Stuart!

Really appreciate your help!

Soundman2020 wrote:I usually put 5cm to 10cm if fiberglass insulation directly in the wall, then a small gap, then the hangers from there, as long as I can make them, and angled somewhere between maybe 15° to 35°, depending on the room.

Okay, good to know.

Have you done a REW test, to determine the exact frequency, and see just how much of a problem it is?

Yes, I have.

It's a colleague's control room and due to the fact that he's using a pair of two-way Genelec speakers that aren't that big, the resonance at 34Hz is not that problematic as it would be with larger speaker. But playing a guitar cabinet in the room, the resonance becomes quite obvious.

How? Where? What type? How big? How thick? How effective are they? What were your decay times like before you put those in (measured at 1/3rd octave band centers), and what are they like now?

It's a combination of Vicoustic Wavewood and Cinema Round absorbers, and Super Bass Extreme and Vari-Bass bass traps - they made quite a difference in this room.

My colleague didn't want to build anything, just apply absorption and bass trapping with commercial products, and they had to look good.

He's not a mixing engineer, just a musician recording and producing his own band.

In my experience, this treatment would be fine in a normal room with wooden or gypsum walls, but I told him that the stone walls and concrete floor and ceiling help keep most of the low-end energy in the room. So he said, let's do the initial treatment and hear how it sounds, and leave the big bass trapping for later.

Now, he wants to go for the second phase of the room treatment, and that will be putting acoustic hangers close to the back wall.

Having built several smaller studios myself, I know that all surfaces needs to be properly treated, but it simply wasn't possible in this room - there was already a really large and heavy production desk in position, so I had to go for simple absorption panels on the front wall.

The reason I ask all of that is because a common mistake is to over-treat the mid and high range, simply by having too much bare absorption aimed at the low end of the spectrum. You might need to do somthing to fix that if this is what has happened.

Agree, and nothing is more unsexy than an overly treated room in the mid-range and treble, but still with boomy low-end that clouds the mid-range even more.

This is not the case, the Wavewood panels provide (somewhat) diffused reflections from about 2kHz and up, and sound really musical. So, in my opinion the room is not overly damped.

It's not just the width of the hangers that is important, but also the depth that they cover, plus other absorption in the same area. As I mentioned above, I put absorption against the rear wall, then the hangers, and sometimes I put more absorption in front of the hangers. For example, a 5cm or 10cm thickness right across the room, or partly across the room, just a bit in front of the hangers. That can extend the range quite usefully, and also improve the effectiveness. So, for example, I might have 5cm at the back a 2 cm gap, 40 cm of hangers (wider than 40cm, but angled), 2cm gap, then 10cm of absorption at the front, for a total of 58 cm. By the time you add any foils, framing, and finish fabric, that brings it up to about 60 cm.

Okay, I have persuaded him to go for 50 cm depth, and more in one of the back corner, the other corner is occupied by a radiator and can't be exploited.

May I ask what kind of absorber you put on either side of the fiber-board? And how thick?

Why only 3m? You said the room was 4m wide...

It's due to limitations in the layout of the room. But I will be able to treat one of the back corners. It's not kosher, I know, but I figure it's better to treat one of the corners, than none of them.

Please provide a diagram of the room, showing how you have it laid out at present, with dimensions, indicating the positions of the speakers, mix position, other furniture, doors, windows, etc.

I don't want to derail this thread about acoustic hangers, maybe I'll start another thread with REW measurements and photos.


Many thanks
Fred

I don't want to derail this thread about acoustic hangers, maybe I'll start another thread with REW measurements and photos.

Excellent! As soon as you have your new thread, please place a link in your first post there back to your first post here, so people can follow things better, and also in your post above, add a link to your new thread.

he's using a pair of two-way Genelec speakers that aren't that big, the resonance at 34Hz is not that problematic as it would be with larger speaker.

When you do the REW test, do make sure that you have the system calibrated correctly for 86dB with both speakers on (refer to this post for details: http://www.johnlsayers.com/phpBB2/viewt ... =3&t=21122 ), and run your tests from 18 Hz to 22 kHz. Hopefully that will trigger the mode enough to identify it well. Also, if there is any treatment that can be taken out easily, then do one set of tests with no treatment in the room (or as little as possible), and another set of tests with all the treatment in. That helps in two ways: 1) Better identify all of the low end issues, and 2) show what is working with the current treatment, and what isn't working.

a combination of Vicoustic Wavewood and Cinema Round absorbers

Those are good mainly for controlling the mid range, especially the low mids. They don't do much at all for the low end.

Super Bass Extreme and Vari-Bass bass traps

They go down a bit lower, for sure, but the still don't get to the area you need to deal with. 30-something is really low, and hard to hit.

My colleague didn't want to build anything, just apply absorption and bass trapping with commercial products, and they had to look good.

To be honest, I'm not aware or any commercial products that accurately and effectively target the very low end, below about 50 Hz. That's a really tough zone to deal with.

but I told him that the stone walls and concrete floor and ceiling help keep most of the low-end energy in the room.

Exactly. Most people don't realize that by "soundproofing" (isolating) a room, they make it sound WORSE inside. The better isolation you have, the worse the room will sound inside. Because isolation prevents the sound from leaving, and if it cannot leave then it must stay inside! Bouncing around . . .

So he said, let's do the initial treatment and hear how it sounds, and leave the big bass trapping for later.

That's actually a bit amusing, since the "initial treatment" for any small room IS the bass trapping!

This is not the case, the Wavewood panels provide (somewhat) diffused reflections from about 2kHz and up, and sound really musical. So, in my opinion the room is not overly damped.

I'd really like to see the REW data, and get details of the room dimensions, layout, and current treatment, to see where it is right now, and where it needs to go.

Okay, I have persuaded him to go for 50 cm depth,

the other corner is occupied by a radiator and can't be exploited.

There might be a way around that... photos!

May I ask what kind of absorber you put on either side of the fiber-board? And how thick?

Medium to light density fiberglass, usually. Maybe around 25 kg/m3m or a bit less. And at least 25mm on each side, more if the room geometry will allow it. 50mm on each side is a good depth to aim for. It's the panel spacing and angles (as dictated by room width), that puts a limit on that. You don't want to go too high in density, or you lose effectiveness in the low end. If you can find the GFR numbers for the products you are considering, then something in the range 10,000 to 20,000 would probably be about right.

It's due to limitations in the layout of the room. But I will be able to treat one of the back corners. It's not kosher, I know, but I figure it's better to treat one of the corners, than none of them.

How about the other corners? There are twelve corners in a room... Have you considered doing the rear-wall/ceiling corner? Like this: Looking forward to your thread!

- Stuart -

Soundman2020 wrote:

So he said, let's do the initial treatment and hear how it sounds, and leave the big bass trapping for later.

That's actually a bit amusing, since the "initial treatment" for any small room IS the bass trapping!

I know, I know. But building thick absorbing inner walls was not an option for my colleague. If I had made such a solution for his room, he would have backed away and continued to produce music in cave acoustics.

Looks like I can't exploit either of the back corners after all, because there's ventilation in one corner and a radiator in the other.

So, what do you think of the following solution for the backwall? (see attached pics)
With "breathable" cloth in front of the isolation.

The hangers have a width of 50cm.


Cheers
Fred

Hi,
This article talks all about acoustic hangers and how to choose the right ones for your space: https://www.mecanocaucho.com/en-US/news ... c-hangers/
I hope this is useful

This article talks all about acoustic hangers and how to choose the right ones for your space:

WRONG! The article does NOT even mention the type of acoustic hangers that this thread is all about!!! And that is pretty darn obvious, just from looking at the last few posts. But would be abundantly clear if you would start from the beginning!

If you don't know the difference between an isolation hanger and an acoustic bass trap hanger, then you have no business posting on this thread at all.

Next time READ THE THREAD before you post totally irrelevant trash.

Also, read the forum rules for posting (click here). . YOu have been warned twice now. You won't be warned a third time. So far, you are acting very much like a "signature spammer", which is why I've been watching your posts so closely, and disabled your signature on every single one. If that is your intention, then leave now. If you really do want to be an active, participating member of the forum, then follow the rules.


- Stuart -

So I am trying to find homasote for the hangers but unfortunately is not available here in Greece.

So I 've got three alternatives (thin to thick and cheap to expensive).
I am posting here and not on the thread I started about my studio, so people will know about these as alternatives (in case they do work)

COPOFEL is made of short-grained cork with polyurethane binder.
Density: 200-280kg/m3.
Thickness of 5mm.
Price=0.67€/m2
Expanded polystyrene (EPS)
density range of 11 to 32 kg/m3.
Thickness of 10mm. Price=0.70€/m2
Standard rockwool
Density: 150kg/m3.
Thickness of 20mm.
Price=3.44€/m2
Which one do you think will work best?
My opinion is the rockwool but regarding the price maybe the next best option is the cork. But I would like to hear your thoughts guys.

Thanks a lot
George

Definitely not the polystyrene or the rockwool. Maybe the "copofel" might work... Is it fairly rigid, something like OSB but softer and more flaky? Also, 5mm is too thin: it needs to be about 12mm

- Stuart -

Soundman2020 wrote:Is it fairly rigid, something like OSB but softer and more flaky

Yes it is softer and flaky but not even close to rigid as osb is. its kinda flexible.
I guess if I glue two sheets together will be more rigid but still..

I `ve been searching for alternatives but with no luck.

So it needs to be rigid like osb but kind of softer, probably porous, density of 150 to 300kg/m3?

hmm