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Tackling room resonances

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Re: Tackling room resonances

Postby Hugh Robjohns » Wed Aug 14, 2019 10:08 pm

I doubt it has enough mass to be very effective as a LMM, although it might work in multiple layers...

I imagine it's really designed to attenuate direct mechanical vibration from footfall noise, rather than deal with energy from acoustic air movement.

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Re: Tackling room resonances

Postby Sam Spoons » Wed Aug 14, 2019 10:26 pm

:thumbup:
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Re: Tackling room resonances

Postby TNGator » Thu Aug 15, 2019 7:58 am

Hugh Robjohns wrote:I doubt it has enough mass to be very effective as a LMM, although it might work in multiple layers...

I imagine it's really designed to attenuate direct mechanical vibration from footfall noise, rather than deal with energy from acoustic air movement.

H
:thumbup: I think so...it does seem to be geared towards footfall etc. But for 20 euro a roll it might be worth the experiment.and as you say I can layer it to get say 10cm or such. I'll keep y'all posted.
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Re: Tackling room resonances

Postby Wonks » Thu Aug 15, 2019 8:21 am

Note that it has a waterproof membrane layer. That means that sound waves won't pass through it like it does through open celled foam, so multiple layers will not be anything like as effective as rockwool. For bass traps, you can normally get away with one impermeable layer (as long as it is free to move), but I'd have thought that once you get to two layers, especially if pressed together, you won't get any further worthwhile improvement by adding more.
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Re: Tackling room resonances

Postby TNGator » Thu Aug 15, 2019 7:19 pm

Wonks wrote:Note that it has a waterproof membrane layer. That means that sound waves won't pass through it like it does through open celled foam, so multiple layers will not be anything like as effective as rockwool. For bass traps, you can normally get away with one impermeable layer (as long as it is free to move), but I'd have thought that once you get to two layers, especially if pressed together, you won't get any further worthwhile improvement by adding more.

Good point. Which brings us back to the question of sound proofing versus sound treatment. Well it was worth looking into I guess. We can only experiment unless your lucky enough to be qualified in acoustics sciences. And i can barely spell those words.
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Re: Tackling room resonances

Postby James Perrett » Thu Aug 15, 2019 8:42 pm

The right sort of carpet underlay could have its uses but it needs careful thought. I've used the underlay made from recycled car tyres in my studio under the floor joists and also where the walls meet the floor. This was after seeing how the old fashioned felt underlay was used by the company who built my previous studio.

In previous builds we had used neoprene sheet in those places but the underlay was cheaper than neoprene sheet so I thought it was worth a try.
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Re: Tackling room resonances

Postby TNGator » Thu Aug 15, 2019 9:19 pm

James Perrett wrote:The right sort of carpet underlay could have its uses but it needs careful thought. I've used the underlay made from recycled car tyres in my studio under the floor joists and also where the walls meet the floor. This was after seeing how the old fashioned felt underlay was used by the company who built my previous studio.

In previous builds we had used neoprene sheet in those places but the underlay was cheaper than neoprene sheet so I thought it was worth a try.
Is that the multi coloured stuff? I have that under the carpet in the front room. It looks like someone chopped up bits of runner and compacted them together with glue.
I saw something on the AIKEA site which might be useful. A large mesh laundry bag. I have some spare mineral wool but its on a roll. Hard to work with and get into a frame. Shoved down into a large mesh bag it would be easy to experiment with. The bag is only a fiver. Cant go wrong there. Two of them and i could test them in two corners. If all else fails...I can always just go and get the pack of rockwool slabs. At the end of the day its the one product everyone agrees is a very good DIY option.
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Re: Tackling room resonances

Postby blinddrew » Thu Aug 15, 2019 9:28 pm

All being well I'll be able to confirm on the rockwool front in about a month or so. Maybe a couple of months to allow for 'learning experiences'.
But frankly, if Max says to use RW3 rockwool then that's what I'm going to use! :D
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Re: Tackling room resonances

Postby James Perrett » Thu Aug 15, 2019 9:58 pm

TNGator wrote:Is that the multi coloured stuff? I have that under the carpet in the front room.

This is the stuff I used

https://www.tradepriced.co.uk/duralay_s ... erlay.html

It seems to help cut out most external noise apart from low flying Chinooks.
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Re: Tackling room resonances

Postby Sam Spoons » Thu Aug 15, 2019 11:36 pm

TNGator wrote:I saw something on the AIKEA site which might be useful. A large mesh laundry bag. I have some spare mineral wool but its on a roll. Hard to work with and get into a frame. Shoved down into a large mesh bag it would be easy to experiment with. The bag is only a fiver. Cant go wrong there. Two of them and i could test them in two corners.

Why bother? you don't need the mesh bag for anything other than cosmetics, leaving the insulation in the plastic bag it came in will be just as effective at low frequencies. Just shove a couple of bags the corners and see if the room sounds better. :thumbup:
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Re: Tackling room resonances

Postby TNGator » Fri Aug 16, 2019 7:10 am

James Perrett wrote:
TNGator wrote:Is that the multi coloured stuff? I have that under the carpet in the front room.

This is the stuff I used

https://www.tradepriced.co.uk/duralay_s ... erlay.html

It seems to help cut out most external noise apart from low flying Chinooks.

:thumbup:
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Re: Tackling room resonances

Postby TNGator » Sat Aug 17, 2019 10:28 pm

Sam Spoons wrote:
TNGator wrote:I saw something on the AIKEA site which might be useful. A large mesh laundry bag. I have some spare mineral wool but its on a roll. Hard to work with and get into a frame. Shoved down into a large mesh bag it would be easy to experiment with. The bag is only a fiver. Cant go wrong there. Two of them and i could test them in two corners.

Why bother? you don't need the mesh bag for anything other than cosmetics, leaving the insulation in the plastic bag it came in will be just as effective at low frequencies. Just shove a couple of bags the corners and see if the room sounds better. :thumbup:
To be honest I thought the plastic would simply bounce all frequencies back. I didnt think anything would get through. Quick question. As its most likely the low frequencies that cause problems, when looking at a room sweep graph, should i concentrate only on frequencies below a certain value. Say everything below 400 Hz for example. Or even from 6 or 700 down maybe?
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Re: Tackling room resonances

Postby Martin Walker » Sun Aug 18, 2019 2:23 am

TNGator wrote:To be honest I thought the plastic would simply bounce all frequencies back. I didnt think anything would get through.

Imagine yourself standing on the other side of that plastic - what frequencies would you still hear? Most of them, apart from the very high ones ;)


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Re: Tackling room resonances

Postby TNGator » Sun Aug 18, 2019 3:44 am

Martin Walker wrote:
TNGator wrote:To be honest I thought the plastic would simply bounce all frequencies back. I didnt think anything would get through.

Imagine yourself standing on the other side of that plastic - what frequencies would you still hear? Most of them, apart from the very high ones ;)


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Cant say I would have known the answer to that one bro. Ah so much to learn. Do you use a diffuser...no..why? Your room is too small. Do i put stuff on the wall? No, its the corners are the problem. Theres a guy on a website called Acousticfields.com says its a myth that the corners are the problem. You need to treat the front wall. And of course you could always treat the side walls. AAAAAAHHHHHH
Im officially starting to go insane regarding this stuff. :headbang: :headbang: :headbang:
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Re: Tackling room resonances

Postby Lewis Goudy » Sun Aug 18, 2019 8:32 am

I just joined SOS and have not read all the posts in this thread yet, but offer an excerpt from Davis & Petronis "Sound Systems Engineering 3E" Ch. 8 "Small Room Acoustics" This might be relevant or not--I'm a beginner.

"In small rooms, the [initial signal delay gap] is normally quite short, on the order of 1 to 5 ms. In a special design of control rooms for monitoring recording studios, a principle called "Live End Dead End,"LEDE, is used that allows ISDs of from 1o to 20 ms to be developed in rooms with dimensions as small as 2000 cu ft. Before the use of the TEF analyzer during the building of LEDE rooms, the front half of the room was made as absorptive as possible (only the diffusion and spectral frequencies are necessary) and the other half (the half to the rear of the listener) was (and still is) made as reflective and diffusive (highly important and often overlooked) as possible. It's in the reflective half that a thorough plotting of refections becomes a necessity...

The LEDE concepts are physically simple but psychoacoustically complex. The goal of an LEDE control room is to let mixing engineers, who sit at the console, hear the first reflections from the recording studio over the control room loudspeakers before they hear any from the control room the are sitting in."
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Re: Tackling room resonances

Postby blinddrew » Sun Aug 18, 2019 9:22 am

That can happen!
There appears to be a huge amount of nonsense spouted about this stuff and successfully treating a room to its absolute best requires a goid knowledge of the physics and a whole bucket of experience.
You can read books to understand the science and the theory but obviously you can only filter the relevant stuff for your environment.
Fortunately we have a secret weapon on this forum, which is the experience of a few genuine professionals, including a very highly regarded acoustician - Studio Support Gnome.
In the next couple of weeks i'll be starting my own work on treatment but before i do i shall be trawling SSG's posts as a reminder.
Plus doing a search on the various SOS articles on the subject.
I've done a lot of research already, and I have a plan, but it's definitely a case of measure twice, cut once - even conceptually. :)
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Re: Tackling room resonances

Postby Sam Spoons » Sun Aug 18, 2019 11:14 am

Here is a brief, non techie, précis of what I have learned about room treatment (and it is brief :smirk: ) I'm sure the more knowledgable will be along shortly if any of the following is just plain wrong :-

Treat the mirror points so that first reflections don't mess up the stereo image.

Fit as many, and the biggest/deepest, bass traps you can (corners are good 'cos you get a bit of 'free' depth, and don't forget there are corners between the walls and ceiling/floor, sofa's work pretty well too).

Then rule of thumb, any big expanse of wall will benefit from a broad band absorber (or diffuser, i.e. bookcase).

It won't make your living room sound like Abbey Road but it will make it sound a good bit better.
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Re: Tackling room resonances

Postby Hugh Robjohns » Sun Aug 18, 2019 11:29 am

TNGator wrote:Im officially starting to go insane regarding this stuff. :headbang: :headbang: :headbang:

I hate to say 'I told ya'... but I told ya! :lol:

Acoustics really is a black art! Of course, there's lots of perfectly sensible science involved, but applying that science is the tricky bit because every room is different. They are different sizes, different shapes and -- most importantly -- different constructions. This last part really complicates things because it's often far from obvious exactly how they are constructed, and that makes a big difference to the low end performance, in particular.

And then there's the whole measuring nightmare, as you've already found out. Interpreting what the numbers and displays mean requires a lot of experience, and it's very easy to start chasing down one avenue only to find it's a wrong turning!

But Sam is right: put as much real bass trapping in the corners as you possibly can, and treat the mirror points to improve the overall mid-range clarity and stereo imaging. And then have a good listen and see what still needs improvement or tweaking... It's never going to be anywhere close to perfect in a small room, so don't expect miracles!

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