Bass traps and diffusers

[RoadrunnerOZ]

I will say that I could probably fit into each panel another layer of the 4” rockwool if that would help?
As it is quite compressed and there is a little space at the back of each panel.
If I did this the rockwool would then definitely make contact with the wall when it is hung on the wall.
It would then be 12” of rockwool into 8” deep panel.

About the best you can achieve but you need to pinpoint where to put these. I’d set up your monitors with the correct monitoring angles centred to the room - you’ll cause yourself grief having them offset to one side

You don't want to add backing material to a velocity based porous absorber, you lessen the effectiveness as you lose the benefit of an air gap.

But if you go for a pressure based absorber it's a different story. Essentially you want a non-rigid vibrating membrane with a lot of mass, and then the insulation material provides damping. This would be a new build, simply adding wood panel backs wouldn't achieve this.

You might want to look into VPR absorbers, fairly simple, low depth, and effective provided you get the right materials. Eric Valentine on you tube has videos documenting a studio build using these.

his absorbers aren’t porous - they’re plastic bagged

 

[Spencerleehorton]

Well I feel like I’ve been a bit miss-informed now from Jesco as I’ve paid for the course and bought all the materials that he specified and from what you guys are saying I’ve got 12 panels that basically do very little to the problem areas of the room!!
I really need to find a plan to try and sort this out and this thread seems to keep spinning off with some other stuff to do with the pipe traps.
What would my best next steps be?
Buy some more dense rockwool?
Build a Helmholtz trap?
VPR absorber?
It’s really quite confusing of what to actually think now!!

 

[Electrobumps]

A lot of the merit in the lower density material is that it provides a smoother damping of the mids and highs whereas the high density compressed board has a much better absorption coefficient at LF without huge depth, coupled with a backboard makes a pretty effective surface treatment.

It has more to do with the gas flow of the material rather than the density. If you have the space to use cheap fluffy fibreglass you will get more low-end absorption. This has worked for me seems to be a consensus for this over at Gearspace. Of course space can be an issue.

 

[Spencerleehorton]

Yes the rockwool is wrapped in cellophane as instructed by Jesco on his course I paid for!
Should I remove all cellophane and just wrap rock wool in hessian or another cotton dust sheet?

 

[RoadrunnerOZ]

Find the locations of the hot spots in the room near your monitors and front of room by generating the frequencies that show as nulls and you’ll hear where the energy is highest. Try unbagging 4 panels and see if when they’re placed in those hot spots they have better effect than the bagged ones. You’ve already made the panels so you need to try and get the best you can from them. If the wool is close to the wall in an unbagged panel it should be fine. The bagged ones may be not working as they have no back resistance and are like leaves in the wind??

 

[Electrobumps]

1. Well I feel like I’ve been a bit miss-informed now from Jesco as I’ve paid for the course and bought all the materials that he specified and from what you guys are saying I’ve got 12 panels that basically do very little to the problem areas of the room!!

I really need to find a plan to try and sort this out and this thread seems to keep spinning off with some other stuff to do with the pipe traps.
What would my best next steps be?
Buy some more dense rockwool?
Build a Helmholtz trap?
VPR absorber?
It’s really quite confusing of what to actually think now!!

It is confusing, I've been there. I've watched some of Jesco's vids and read some of his free stuff. I'd recommend searching some of the threads on Gearspace relating to "pink fluffy" insulation.

I'm now an advocate of deep traps with low gas flow fibreglass. Experiment with that link to the absorber caIc I posted and try a gas flow of 10000 (your rock wool) and 3000 (fluffy fibre) then see what the maximum fluffy fibre you could use vs rockwool and you can get a rough idea if it will help to sort the problem frequencies.

This is why I am an advocate of deep low gas flow broadband absorbers.

1. The absorption is broadband.
2. Has good effect even as low as 30hz
3. The material is cheaper than denser insulation
4. It's lighter and easier to hang

Cons

1. Takes space
2. Needs chicken wire to prevent sagging

 

[kags]

I think things are moving off course. Velocity absorbers do not work well with hard backing or a hard center. They also work well with a few inches of airspace (or more as in the corners). You should also check on “random incidence” for the absorber calculator. Safe n Sound is about 10,000 ray’s and 703 is more like 250000. I don’t know what would be 3000, other than fluffy roll insulation.

 

[Electrobumps]

I don’t know what would be 3000, other than fluffy roll insulation.

I got great results with fluffy fibre at 18" and the air gap is not so important at such low gas flows......so I've read!

 

[Spencerleehorton]

Should I remove the clingfilm plastic wrap on the rockwool in each panel?
Could this be one of my many problems?

 

[Spencerleehorton]

Ah ok sorry missed that post:

To do list

1. Set frequency generator to 83hz and walk room and find loud point and then to 118hz and walk the room and try and find the loudest point at those frequencies
2. Take plastic wrap of 4 panels and place panels in the loud positions and see if wrapped or not wrapped rockwool works better
3. Build some more traps (I have some more materials to build some smaller traps but I can use them for the other room but these can help find the problem areas in the mix room.

 

[Tubetec]

I just dropped in on this thread now ,so might have to catch up .

I'm just wondering about rockwool or fibreglass safety , in terms of house insulation this stuff has been superseeded , the main reason being its prone to degrading under certain conditions and its an irritant .
For instance if theres high humidity the rockwool fibers absorb some of it , if it then goes below freeze the stuff has a tendency to turn to dust particals ,glass dust is not healthy .
I've been talking to a few people in the building trade lately about the various hazardous materials used over the years , One wise old guy told me , whats used currently doesnt tend to get badged 'dangerous' or hazardous until the superseeding product has become common .
Anyway just wondering if anyone has checked into the safety aspects of using rock wool and what alternatives there are .

Theres lots of stories from the building trade over the years about problematic materials that degrade over time , one was the use of polystyrene insulation in close proximity to electrical wiring , it leaches out some of the oils from the wire insulation and can eventually lead to it breaking down .

 

[RoadrunnerOZ]

It has more to do with the gas flow of the material rather than the density. If you have the space to use cheap fluffy fibreglass you will get more low-end absorption. This has worked for me seems to be a consensus for this over at Gearspace. Of course space can be an issue.

It’s about gas flow through the material and the amount of resistance imposed by the material before it reaches a reflective surface and then the resistance as it passes back through after reflection. That’s why the high density stuff has a much higher absorption coefficient at low frequencies compared to the low density. If the absorptive material can’t restrict the airflow, it’s not working - it needs to impede the flow of air to convert sound mechanical energy to heat - 3 layers of 35Kg/cuM Rockwool may have the same effect as 1 layer of higher density material at say 96Kg/cuM for the same sheet thickness and will maybe have a better gas flow impedance due to the distance travelled through resistive material but the size gets outrageous. I don’t see how lightweight glass fibre would be an improvement on heavier Rockwool. The compressed fibreboard I have compared to packed blanket in walls in several studio builds and on panel absorbers and to be honest it’s streets better.
Space is an issue here as the room is only 3M x 4M.

 

[RoadrunnerOZ]

I just dropped in on this thread now ,so might have to catch up .

I'm just wondering about rockwool or fibreglass safety , in terms of house insulation this stuff has been superseeded , the main reason being its prone to degrading under certain conditions and its an irritant .
For instance if theres high humidity the rockwool fibers absorb some of it , if it then goes below freeze the stuff has a tendency to turn to dust particals ,glass dust in not healthy .
I've been talking to a few people in the building trade lately about the various hazardous materials used over the years , One wise old guy told me , whats used currently doesnt tend to get badged 'dangerous' or hazardous until the superseeding product has become common .
Anyway just wondering if anyone has checked into the safety aspects of using rock wool and what alternatives there are .

This is one of the reasons to use the compressed sand/fibreglass board - webbed resin backing, cloth facing, you can just resin brush the edges to prevent shedding after cutting with a trimming knife. Rockwool and glass blanket shed continuously for their whole life as they sag under their own weight and the fibres break. I mentioned previously about opening walls that had originally been filled with blanket insulation and the top 1/4 of each chamber was empty - the blanket had been wired in place and glued to one inside face but it still just fell off.

 

[kags]

I think things are moving off course. Velocity absorbers do not work well with hard backing or a hard center. They also work well with a few inches of airspace (or more as in the corners). You should also c heck on “random incidence” for the absorber calculator. Safe n Sound is about 10,000 ray’s and 703 is more like 250000. I don’t know what would be 3000,

Should I remove the clingfilm plastic wrap on the rockwool in each panel?
Could this be one of my many

Well I feel like I’ve been a bit miss-informed now from Jesco as I’ve paid for the course and bought all the materials that he specified and from what you guys are saying I’ve got 12 panels that basically do very little to the problem areas of the room!!
I really need to find a plan to try and sort this out and this thread seems to keep spinning off with some other stuff to do with the pipe traps.
What would my best next steps be?
Buy some more dense rockwool?
Build a Helmholtz trap?
VPR absorber?
It’s really quite confusing of what to actually think now!!

Have you looked at the time decay (waterfall or spectrograph) for your room? The freq response is not bad if the decay time is pretty even, especially for that room. Have you measured with the door open or closed (think about how you will typically work)

Jesco has solid info. You can get way more complicated or exotic, but his principles will get you to a really good place. For just porous absorbers like yours, I would think 10 to 15 panels would be necessary. If you want to build tuned panel absorbers, they would be thin enough (4” or less) to go behind porous absorbers.

Inspect the time behavior before you worry more about the frequency graph.

 

[RoadrunnerOZ]

Ah ok sorry missed that post:

To do list

1. Set frequency generator to 83hz and walk room and find loud point and then to 118hz and walk the room and try and find the loudest point at those frequencies
2. Take plastic wrap of 4 panels and place panels in the loud positions and see if wrapped or not wrapped rockwool works better
3. Build some more traps (I have some more materials to build some smaller traps but I can use them for the other room but these can help find the problem areas in the mix room.

Perfect - make sure to set up your monitors first. I use a tape measure and protractor to set the monitor equilateral triangle.

 

[kags]

This is one of the reasons to use the compressed sand/fibreglass board - webbed resin backing, cloth facing, you can just resin brush the edges to prevent shedding after cutting with a trimming knife. Rockwool and glass blanket shed continuously for their whole life as they sag under their own weight and the fibres break. I mentioned previously about opening walls that had originally been filled with blanket insulation and the top 1/4 of each chamber was empty - the blanket had been wired in place and glued to one inside face but it still just fell off.

Do you have a brand / model for those boards? I haven’t seen cloth faced panels around here.

I like the epoxy sealant idea, too

 

[kags]

Personally I wouldn't remove the wrap and risk exposing fibers. My guess is it will only alter high frequency absorption. But if you are willing to do it, it would be interesting to see if it makes a low frequency difference. It's possible the wrap might actually be slightly helping low frequency due to membrane effect.

The big issue is that treating low frequency modal problems is not easy. The options are generally frequency targeted pressure absorbers, or you brute force with 24-30" of low density insulation.

I agree about the plastic. He does have that effective depth across the corners. Some room dimensions never get much better without exotic solutions , but as long as the time domain is even, the room will yield excellent results.

 

[john12ax7]

Anyway just wondering if anyone has checked into the safety aspects of using rock wool and what alternatives there are .

Caruso Isobond is an interesting option if you are in a part of the world where is available

 

[kags]

It has more to do with the gas flow of the material rather than the density. If you have the space to use cheap fluffy fibreglass you will get more low-end absorption. This has worked for me seems to be a consensus for this over at Gearspace. Of course space can be an issue.

I like to use a 1 or 2” layer of dense, like 703 or 705 or even Roxul 40 with fluffy behind it, if you have the space. Dense insulation loses its effectiveness after 8” or so and the density gradient and possible membrane behavior of the dense “face” adds more effectiveness. Plus the dense material provides a nice flat surface to back the fabric. I’m doing this treatment now. Front corners are 1m wide and .4 m deep with 4” Roxul 40 and fluffy behind. I used similar treatment in rear corners and we have excellent results. We also have a large 10” ceiling cloud and other first reflection treatments.

 

[kags]

I got great results with fluffy fibre at 18" and the air gap is not so important at such low gas flows......so I've read!

A 4” Air gap behind 6 or 8” is about 90% as effective as thicker fiber and costs less, but yours should be great!