New space - studio in Athens

Gregwor wrote:

20 kg/m3 of fiberglass?

Yes it's black colored fiberglass wool

I know where I live Homasote is worth more than gold so I am using 2" insulation in my design to save thousands of dollars.

I found the 2.44m x 1.22m Homasote board that is 10mm thick around 10euros each, so is not cheap but it's ok. If I just make the hangers less thick and add like 5 to 10 more hangers overall, it's not a big deal, if they indeed are more effective this way..

I found the 2.44m x 1.22m Homasote board that is 10mm thick around 10euros each, so is not cheap but it's ok.

Those run about 40euros here. Greg

wow! Also Greg , I am almost done with the ventilation, I will soon post the details!

So hanger's plan changed. That's the new one: I will now have 43 hangers instead of 34 with the previous plan. And bigger too going from total coverage of 140m2 to 203m2 They will be 3.6 meters high :) Of course there will be some changes here and there because of the door and vent's pipes but you get the big picture.

Hi all! I read that a good ISD gap for an RFZ room falls between 20ms to 30ms with the ideal being towards 25-30ms. I am trying to find information how to handle longer ISD gap but no luck.. According to my room dimensions (8.7L x 4.45W x 3.95H meters) I get from AMROC that the critical distance is 1.31m , while J.H.Brandt’s room mode calculator doubles the critical distance to 2.6m for an EBU listening room. I suppose the later is the correct one. Anyway, listening position of 38% percent falls far outside these regions (1.3-2.6m) as it is 3.3 meters, so it is more likely to place the listening position somewhere between 2-2.5 meters of the length (regarding SBIR, measurements and practical position). That gives me an ISD gap of 36 to 39ms roundtrip for the back wall reflection. I am already building the back wall hangers, as you can see on previous posts, and I am also thinking about building a 75cm deep skyline diffuser (18x17, prime 307) for regions 250 to 3500 (LF and HF cutoff calculated for my room and listening distance) though I can not make it bigger than 90x90cm due to the position of the door being close to the center of the back wall. So ending with my questions, is this longer 35-40ms ISD gap a problem? If not then are the hangers and the diffuser enough to return this reflections as a diffusive field's ones and lowered by 20-25db? Any thoughts would be appreciated! Thanks!

ok there's my answer, thanks Stuart :)

Soundman2020 wrote:

Therefore, the current best control room designs do return that diffuse field after about 20ms, or maybe 30 ms, or maybe even 50 ms in a large room, and that gives your brain all the clues it needs to figure out the room that it is in, and correctly interpret the acoustic "signature". As long as the "gap" is at least 20ms long, and up to about 50ms, your brain is happy: the room sounds natural, neutral, open, neither too dead nor too live, and you get to hear only the pure, clean, unmodified sound exactly as it came out the speakers, not colored in any way by the room, or by these subtle psych-acoustic effects. [...] So, the sound field that comes back at you from behind 20ms (or more) after the direct sound, also has to be at least 20 dB lower than than the direct sound, and it has to be diffuse, not specular. In most control rooms, that is achieved with a combination of acoustically absorptive surfaces (to reduce the level by 20 dB), acoustically reflective surfaces (to send a little bit of the sound directly back, but not much) and acoustically diffusive surfaces, to break up the sound into a diffuse field. [...] Now, if your room is bigger, then the ITDG can be longer: 30ms is good too! And you can also have a slightly lower level, such as maybe 25 dB down, especially if he room is large, ... as long as you still have an overall decay time that isn't too short for the size of the room.-

Post taken from this topic Still don't know if hangers and this single diffuser will be enough to achieve the desired result but I guess I will find out the hard way..hehe :D

Looks good! Greg

Good to know that I am on the right track! Thanks Greg Today I figured out that in addition to the central 90x90cm skyline diffuser I can add more diffusers in variable places on the back side. Two 1d qrd diffusers on left and right part of the back wall ( hanger's false wall) and another two on back side walls, being something like 1x1m big each for frequencies of 350 to 3500hz. Also 2 skylines on ceiling at the back, right before the false wall, on both sides of the cloud. I will ray trace to find the exact spots for the placements. Hopefully this plan will return a diffusive field back to listening position

Jumping back..about the front superchunks.. Do you see any advantage of adding a rockwool face layer of 1-2cm, 75kg density (49K.Pas/m2) ? I am using porous calculator and it tells me that it is better without a face layer.. Any real world experience? To remind you that my superchunks are 1.42 meters wide and 4 meters high.

Anyone who has tested something similar? the chunks are filled with light wool GFR of 5Kpas/m2

You are probably fine just like that, but if you want to be certain, then use REW! Do a test now, compare it to the test for the empty room. Then add the face insulation temporarily and do another test: compare that against both of the previous tests. That way, you can see if it makes a useful difference anywhere. - Stuart -

Thank you Stuart, I think I 'll take your word that its fine without the face layer because right now I am in the middle of building the hangers on back wall and I have moved all things close to front wall so it's difficult to test it. That's the reason I asked for an assessment. I will see if I can give it a try once I am done at the back!

Posting some photos of my progress so far. I've built the ventilation's silencer boxes using 15mm OSB, lined inside with 50mm insulation. Four of them, two for each air path (fresh and exhausted), one on each side of the room (in and out). Added two layers of 12.5mm gypsum board over the 15-20mm OSB/mdf of the boxes and interconnections. All layers mould proofed, glued, screwed, caulked, primer coated and painted. Working as calculated (Thanks Gregwor!!!) moving a big mass of air but really slow, no sound leaking neither inside nor outside, no audible sound of the motor, the moving air and finally the speakers. There is a thing though. I can see that when I move really close to a power outlet (that would be close to a wall that has a drilled hole for fixing an external power outlet), fresh air is coming inside from the cracks of this hole (all walls are double brick with air gap inbetween). Like the fresh air coming inside from the ducts is not enough for replacing the exhausted and like trying to get more from all possible openings ( as the door is totally sealed). Not sure why this is happening, I only calculated the total static pressure for the system. Maybe I had to compare in and out paths to be matched.. Since the system is working on a single motor which exhausts the air, thus forcing the fresh air to get in, I was wondering if adding a second motor to push the air inside would fix this issue? Boxes and inside work:

And some more on a second post cause they were too much fitting on my previous post. Just the outside on this:

Woah! That turned out killer! How does your insertion loss seem with the silencers? Can you hear much through them? Greg

Not at all! I am satisfied as I tried higher than my normal mixing levels and still is good, no sound getting in or out. I guess the 2 boxes inside, 2 outside and making them really big is working good! Also there is no sound at all when the ventilation is working. I even tried boosting the motor's speed up to 100% and still you can not tell if it is on. It's design to work around 35% in order not to overload the motor and meet the criteria for the air changes, etc. Still on full speed you can only feel the draft! Working like a charm. I can't thank you enough for all your help Greg

Amazing to hear (or not hear I guess!) Please continue to share your journey with us! Greg

Will do!!!! I am still working the hangers project on the back wall, I will post some photos as soon as I finish. I just got the homasote boards and the insulation, the surrounding walls are all lined with rockwool sheets and just finished installing the hanger's support frame on the ceiling. Getting there...!

That's the soft board I am using for the hanger's core. The density is around 300kg/m3. It supports the weight of a 3.6 meter high and 85cm wide hanger , (with 3cm thick and 20kg/m3 dense insulation on each side attached ) easily without bending or tearing apart. Here's also a video of it: https://youtu.be/emqtCSduZOA

Hey, I'm looking forward to your posts on your back wall since I'm about to get going on the same thing! Keep us posted!

Hey, thanks, I will post some photos of the progress made so far within the next few days! If you need any help just let me know!

Hi!!! Posting more photos of my progress so far! Here's my DIY 1D QRD: Here are the steel supporting rails for the hangers: Hangers' core and insulation: Hangers:

Holy crap those are tall hangers! Are you taking acoustic measurements at each step of the treatment process? I'd love to see the difference the hangers have made. What is your design logic behind the diffuser? It is obviously tuned very very low. Are you concerned about lobing effects? Great work as usual my dude! Greg

Gregwor wrote:

Holy crap those are tall hangers!

Yeap 3.6 meters high monsters!

Are you taking acoustic measurements at each step of the treatment process? I'd love to see the difference the hangers have made.

I would love too! Hang on there sir, I have to get rid a mountain of things sitting right in the middle of the room covered with a plastic foil..No room to move them elsewhere.. :cry Soon..

What is your design logic behind the diffuser? It is obviously tuned very very low. Are you concerned about lobing effects?

I am aiming for a back wall returning sound field that will be diffusive. So I need a combination of absorption, reflection and diffussion. I also planned ahead and I have the option of adding more diffusers for the desired frequency range on that back wall to make the effect stronger but that will need testing. I am not worried about the lobing effects because according to my calculations I am at a safe distance from the back wall. That will be 6 meters (20ft) away from my head when on listening position. The diffuser's dimension were calculated in order to tune it specifically for my room taking into consideration it's LF and HF cutoff, listening position (regarding SBIR, measurements and practical position), ISD gap, etc.

Great work as usual my dude!

Thank you so much my friend!!

I'm also very interested in some measurements, since I want to build something similar for my new mixing room! :mrgreen: