Wall/slot

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?

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

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

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

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!

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

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?

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 :cry: ) 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

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

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

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?

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

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 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?

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

I dont know what to say Steve! You are always very helpfull!! Ok I am starting construction tommorow!Could I post pictures? Could you tell me what to read to understand those modes? I have Everest's Handbook Cooper's Building a recording studio and Newell's Recording studio design. Yet I dont have a clear understanding on what those p,q,r are!j(':oops:') last question(for today)(':roll:') John's resonator Starts at 5cm and goes up to 20cm with an angle. i have 30cm space how should I make that angle? Also can I mix slats width-depth and use several gaps or make each resonator with one size slats? Thank you very much

Steve, today I have start the construction! First the ceiling and then framing!! About those 3cm MDF!Man its really heavy.......VERY heavy!!! Do you know the weight per square meter? please tell me about those slots that I have asked in my previous post! thanks!

A 1200mm x 2400mm x 30mm MDF should weigh around 175-190 pounds, or about 80 kg. About 28 kg per sq. meter. Here's what I'd do for your slats; remember, every dimension in this drawing will affect your center frequency if you change it - I chose 300 hZ because it's a common problem, but without a drawing of your room I couldn't even get close to what needs to be there; even WITH a drawing, the only SURE way is to LISTEN and TEST after the room is DONE. Odds are, though, that this will work well. The Depth From Wall measurement of 150mm is an AVERAGE - you can run the depth from nearly nothing up to your maximum of 300mm, and the trap will work at a smooth band somewhere around 300 hZ. If you have a 9mm handgun, you could just use a couple of bullets for spacers when placing the slats... :twisted: Steve

Thank you Steve! John's resonator starts from 5cm up to 20cm and has 5cm insulation behind the slats! 1) Should mine start from 10cm up to 30cm and have 10cm of insulation? 2) I will have 3 resonators 0,80cmx2,17m. make them all around the same center fq of 300hz ,as you mention, or choose different for each one? If yes what fq would you choose please? Thank you very much

1) - Depends on how WIDE your unit will be; you want at least a 6 degree angle to help kill flutter echo. You've given NO DIMENSIONS whatsoever yet, so I can't answer in absolute measurements until you do. 2) - without a drawing of your room I couldn't even get close to what needs to be there; even WITH a drawing, the only SURE way is to LISTEN and TEST after the room is DONE. I've seen your drawing on the Design forum, but which of those openings are you planning on covering with these "trap/soundproofing" panels, and what size are those openings? Also, are the walls of this space made from concrete, wood, gypsum, ?? Please understand that any advice I give you from across the sea will at BEST only be a WILD GUESS; you will need to make tests and listen in the space, in this case do some recordings and analyze their quality, etc; anything else is just BULL. About all I could do is calculate APPROXIMATELY what the modes would be for that size room, but with 3 openings and any other features that take away from it's being a perfect rectanglular room, it's just not very useful... Steve

"Please understand that any advice I give you from across the sea will at BEST only be a WILD GUESS;" You are right Steve but your advice ,even if it is from the other side of the world, its an EXPERT'S advice. You are a great help for me and for many others keeping us away from darkness!! I will try to be as analytical I can This room is 270cm x 324cm x 300 cm (small room) Its gonna be the tracking room. I have live 30 cm space from the ceiling(concrete) and then i have put 30cm of rockwool in this order. top to bottom: ceiling >30cm space>10cm rockwool(40kg)>10cm rockwool (75kg)>10cm rockwool(40kg)>cloth. In the picture rockwool of 10cm its: 5cm 40kg(face) and 5cm 75 (back) The basstraps are rockwool 75kg and i will put 4 ceiling corners basstraps also. the size of the red resonator on the right side its not as the size of the openig(measurement its on the openings not the resonators) The size of that panel is 217x 92 x20cm. The resonator at the bottom is two panels 217 x 80 x30cm Also the measurement its on the openings not the resonators Should i make the panels feet in the openings(with rubber around)or make them cover the openings? thank you Ps:the floor is marble

Should i make the panels feet in the openings(with rubber around)or make them cover the openings? Since you want these to help isolate, it might be better to build them similar to "window plugs" - http://www.johnlsayers.com/phpBB2/viewtopic.php?t=239 Drawing at the bottom of the page is for window plug, but the main thing I meant was to use the "Lip" around the edge, with some kind of foam seal as shown at the bottom of the drawing. Maybe this (idea below) could work - Steve

Thank you Steve! 1) What if I do it as the draw below? Its easier for me. 2) also the panel will be two pieces 65cm wide. Should I live the space behind the insulation empty or put some more so the 50% of the air space be insulated? 3)what angle should I choose? thank you

Seals - either side will work, no problem. Angles - 6 degrees is MINIMUM, a bit more wouldn't hurt. Building the insert with just ONE, full-width, section (as I sketched) will work as well and be easier to build - but heavier to move... Forgot to mention, the foam-lined board is something you push up against the bottom of the panel after it's in place, just to seal around the bottom. The space behind the insulation needs to be open; I think I mentioned that the thicker the insulation (in percent of total ) the broader the response, but also the LESS the absorption at center frequency. Somewhere between 25% and 50% of the AVERAGE depth of the trap is a good choice... Steve

Hi Steve I have finally finish the rec room and It sounds very neutral!! I am happy with it! my question is about the angle of the slots. i have two boxes 215x65x20cm. what angles should I use? A or B ? you said that the angles help to kill flutter echo. Echo is caused by the opposite parallel wall? Even if it has 10cm rockwool with 5cm airspace? I am asking that because its difficult to make the angles. Thank you