Wall/slot

Yiannis · Post by **Yiannis** » Tue Apr 12, 2005 3:10 am

Hi to all!!

What do you think about this wall unit!
Its gonna be a moving wall plus it will have a slot resonator on the inside.

any comments please?

knightfly · Post by **knightfly** » Tue Apr 12, 2005 6:42 am

Doesn't look like it will work for either use; if those two brown layers at the rear on either side of the rear most absorbent are supposed to be two leaves in a mass-air-mass barrier, they are flanked by the end pieces and are too light for good isolation.

How will this be set up so it's movable? Hinges, casters, handles to pick it up, ??

The inner insulation layer, in order to work as a Helmholtz, needs to be up against the front slats with only a cloth between it and the slats; this forces the slots into helmholtz mode, and also damps the slats to lessen any ringing at resonance frequency.

The thicker the insulation inside, the broader band the Helmholtz action and the less the trapping effect; somewhere around 50% of the total inside space (average) is a good working range of thickness in most cases... Steve

Yiannis · Post by **Yiannis** » Tue Apr 12, 2005 7:21 am

Hi Steve,

thank you very much for your reply and for your help again!

I am trying to do the best for the place that I have to work in for the moment!

Anfortunately I dont have the ideal place to record music, so I am trying to do the best to make it sound ok.

Well the back panel gonna be 3cm mdf as the one in the middle.
Still not good right?

About the resonators you say that fill the 50% withh isulation gonna be ok.

What about if I fill all the space behind the slots?

I am planning to use 3cm slats.Is that ok?
Also John says (in the draws) that the salts should have gaps from 6mm-12mm.In what ratio and order please?

I mean if it is : 6mm-7mm-8mm-9mm-10mm-11mm-12mm
It should be in linear mode or random?

Thanks again and forgive me for my english

Yiannis

PS:I will use casters and handles to move those panels

knightfly · Post by **knightfly** » Tue Apr 12, 2005 7:42 am

Well the back panel gonna be 3cm mdf

3 cm, or 3mm??

What about if I fill all the space behind the slots?

Then you would have a nice looking bass trap that won't absorb highs, but it would NOT be a slat absorber.

There are specific ways of setting the spacing and depth of each part of a trap to get the desired result. Unless you already KNOW what specific frequencies you will have problems with (doubtful until you finish the room) it's not a good idea to pick random frequencies and build traps for them.

Can you link to your existing thread on room details so I can get a better idea of what's already there (or will be)? Thanks... Steve

Yiannis · Post by **Yiannis** » Tue Apr 12, 2005 7:58 am

Thanks Steve.

Its 3cm.

Here is the link but please dont laught with the room (at least not loud)

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=3470

Thank you very much Steve!
Always a big help!

knightfly · Post by **knightfly** » Tue Apr 12, 2005 10:12 am

OK, starting to make a bit more sense now I see what you're up against - still, I'm not sure I understand what your picture of the slat absorber is showing - I see a thin layer at the very back, then rockwool, then a thicker layer, then more rockwool, then an air space and finally the slats.

What SHOULD be there, is a HEAVY back panel, then an air space, then rockwool against the front slats, with a cloth cover between the slats and the rockwool.

Are you hoping that this will also act as a sound isolation between rooms by placing it in front of your doors? Steve

Yiannis · Post by **Yiannis** » Tue Apr 12, 2005 7:23 pm

Hi Steve,

Here is an update of the slot!

The MDF is 3cm. Is it heavy?

I am trying to make it act as a sound isolator too!Not a perfect one!!

Thank you!

PS:Is 50kg/m3 rockwool ok?

knightfly · Post by **knightfly** » Wed Apr 13, 2005 4:43 am

3 cm MDF should be heavy enough to give you a hernia; and if it's sealed around the edges, it should help several dB with isolation (provided that the REST of the space is ALSO sealed - otherwise, not so much

)

That's the correct positioning for the absorbent when used in a Helmholtz (slat) resonator. Now, do you have ANY idea what frequency(s) these should be tuned to? Steve

Yiannis · Post by **Yiannis** » Wed Apr 13, 2005 4:56 am

Steve,

I will be very carefull when I will move those beasts!!

finally I have 3cm for the back-top-bottom and 2cm for the sides!

Should I make the slats with an angle(as in the draw)or not?

What do you think about the panel?Live it as in the draw or make it like this: back panel 3cm MDF>>5cm rockwool>>2cmMDF(or osb) and then air space rockwool,cloth,slats!

Will that give to me better isolation?
I have no idea about those frequencys!

Thank you

knightfly · Post by **knightfly** » Wed Apr 13, 2005 6:19 am

I would leave it as in the drawing; your sound isolation would be limited to "mass law" of the rear panel, so would only amount to maybe STC 30 at best, with around 20 dB TL at low frequencies. Even this will only happen with total seal around the edges.

The slanted front will help reduce or eliminate flutter echo in the room... Steve

Yiannis · Post by **Yiannis** » Wed Apr 13, 2005 6:36 am

Ok Steve I will construct it as you say!

The oposite wall from the panels will be 10cm rockwool with 5cm space coverd with cloth.Good or bad?

All the corners will have basstraps.Also the ceiling corners

another question about the ceiling please!

Room height is 3,24m!
i am planning to live 30cm air space and then put 30cm of rookwool covered with cloth.Not for isolation just for absorption!
Comments?

Yiannis · Post by **Yiannis** » Wed Apr 13, 2005 2:20 pm

Steve you said that

"your sound isolation would be limited to "mass law" of the rear panel,"

Then I have 3cm MDF (mass) air gap(spring) and 5cm rockwool(mass?).
Should I double the rockwool layer to have more mass or live the construction as John says at 20cm?
Now its 30cm front to back

Thanks

knightfly · Post by **knightfly** » Thu Apr 14, 2005 5:09 am

No, only the MDF would count as isolation; the rockwool won't do ANYTHING for isolation, only for absorption at or around frequencies determined by slat and slot width, and average air gap depth measured from the rear of the slats to the midpoint of the rear MDF panel.

If anything, putting the slats/rockwool in front of the MDF would WORSEN the isolation, especially at the resonant frequency.

You do NOT want to thicken the rockwool to fill the trap, or else it won't BE a trap but only a deflector; leave the rockwool thickness as John said... Steve

Yiannis · Post by **Yiannis** » Thu Apr 14, 2005 5:13 am

Yiannis wrote:Ok Steve I will construct it as you say!

The oposite wall from the panels will be 10cm rockwool with 5cm space coverd with cloth.Good or bad?

All the corners will have basstraps.Also the ceiling corners

another question about the ceiling please!

Room height is 3,24m!
i am planning to live 30cm air space and then put 30cm of rookwool covered with cloth.Not for isolation just for absorption!
Comments?

Thank you Steve!

Could you please tell me your opinion on the above questions too?

knightfly · Post by **knightfly** » Thu Apr 14, 2005 5:39 am

That all sounds like a good plan; especially the ceiling. That should give good absorption to pretty low frequencies, so should be very even sound... Steve