Basic treatment for small home production/mixing room

#1

Hello everyone,

I come here from the John Sayers forum and since Stuart was the only one that I got any feedback on my plan from there and John himself provided the link to this new forum I figured I will move my topic here

For start let me just copy some information about the room from my original post and then I will pick up where I am now and post some measurments

I am currently in the process of designing my room. Due to budget constraints my plan is to go with basic treatment and hopefully get a useable space to work in. The room is going to be used mainly for production (sound effects and music) and mixing, would be nice to be able to record some voiceovers and maybe acoustic guitar.

CONSTRUCTION DETAILS:

The room is on ground level, floor is strip footing filled with concrete, wall with window on it is an outer wall made from concrete masonry unit and styrofoam (12 concrete, 8 styrofoam, 24 concrete, 45cm total thickness) and other four inner walls are made from brick (25cm thick). Front wall is next to the garage, rear wall is next to a hall connected with kitchen.

The floor surface is roughly 13.5m2 and ceiling is 270 cm high.

ROOM LAYOUT:

I plan to put the desk so that the window is on my right side when mixing in order to place speakers along the longer wall. I’m also considering flipping it so that the window is behind in case this 30cm deep window cavity turns out to compromise symmetry.

The speakers will be Genelec 8030 with 7050 sub. Though I’m aware soffit mounting would probably be best I could do I don’t feel like being able to construct them properly for now and it also might exceed the budget quickly, so instead I hope to reduce the SBIR issues reasonably by placing speakers, on massive stands, tight against 10cm thick panels and a little bit with speaker cabinet construction.

ISLOATION

I got some measurements done with SPL meter and music playing in the room at 95 dBC reads about 60 dBC in the kitchen and living room next to the room (ambient level there is 35 dbA) and 75 dBC and 70 dBC at the door and window respectively.

At the line of the property it reads about 50 dbC and the local code states max 50 dbA for the day and 40 dbA for the night.

As for noise coming in I measured the exceptionally strong wind and rain few days ago along with loud kitchen equipment running and it showed 60-65 dbC in the room. Probably the biggest issue here is the front door of the house as slamming it gives about 85 dBC in the room and normal operating about 70 dBC, but since it is house structure related I guess it's just something I will have to live with for now, considering small budget.

TREATMENT:

Basic treatment plan is superchunks in three right angle vertical corners (ROCKSONIC SUPER 10CM, 38KG/m3 density, ~78cm across corner), 2 panels on the front wall, behind the monitors, tight against the wall (PT80 80kg/m3, 10 CM), 2 side panels on the first reflection points (TOPROCK SUPER 15 CM 40kg/m3) 10cm gap from the wall, floor to ceiling on the rear wall treatment (TOPROCK SUPER 15 CM 40kg/m3). Hardbacked cloud on the ceiling.

These are the specs provided by manufacturer of PT80 (80kg/m3):

Here is the design of treatment in skechup including advice I got from Stuart on John's forum:

: jaku5-treatment-rear-2.png (212.31 KiB) Viewed 45888 times

: jaku5-treatment-rear-2.png (212.31 KiB) Viewed 45888 times

: jaku5-treatment-rear-1.png (281.43 KiB) Viewed 45888 times

: jaku5-treatment-rear-1.png (281.43 KiB) Viewed 45888 times

: jaku5-treatment-front.png (80.22 KiB) Viewed 45888 times

: jaku5-treatment-front.png (80.22 KiB) Viewed 45888 times

Cloud:

206 cm x 105 cm frame, 2 cm thick MDF/OSB hard backed, angled 15 degrees. Thanks a lot Stuart for providing that ray tracing tool.

: jaku5-cloud-raytracing.png (176.15 KiB) Viewed 45888 times

: jaku5-cloud-raytracing.png (176.15 KiB) Viewed 45888 times

The oroginal plan was as follows:

The plan is as follows

1. Rip out the carpet
2. Do the baseline REW test
3. Superchunks and panels behind speakers
4. REW test
5. Rear wall treatment and side panels
6. REW test
7. Ceiling treatment
8. REW test
9. Door replacement and floor finishing
10. REW test

But now I'm thinking maybe I should take care of isolation and HVAC first so replace the door and stuff the window before any treatment comes in.

Speaking of HVAC I did some calculations:

The general plan would be to divide HVAC in two stages. First make a ventilation system now and then save some money during winter and install the mini split once temperatures start to rise (around March).

The room is ~38 m3 so I would need 228 CMH = 3,8 CMM = 134 CFM of an air flow. 25% of makeup air would then be 57 CMH = 0,95 CMM = 33,5 CFM which should be also enough for two people to be comfortable in the room.

For my ventilation I was planning to go with small HRV unit, 125mm diameter flex duct (which would give me an air velocity of 1,29 m/s) and two silencers (one for intake and one for exhaust) outside the room but after some more thinking I am kind of leaning towards inline fan and making fresh air intake in front and using the existing passive exhaust at the back because this is not huge amount of air and I'm wondering is HRV really worth it in my situation.

Cross-sectional area of silencers would be 16 cm x 16 cm = 256 cm2 (125mm duct CSA = 123 cm2).

Registers could then be 170 mm x 300 mm (effective 300cm2) resulting in 0.38 m/s air velocity.

If I calculate that correctly (thanks to Greg on JS for making calculator and sharing his knowledge) the entire ventilation system should give me around 25pa of static pressure which would be about all right for the HRV unit I was considering.

: HRV-spec.png (36.94 KiB) Viewed 45888 times

: HRV-spec.png (36.94 KiB) Viewed 45888 times

I am yet to calculate my sensible and latent loads to chose right mini-split but I will leave an empty space next to fresh air intake register for the unit.

Original HVAC plan:

: jaku5-registers.png (252.1 KiB) Viewed 45888 times

: jaku5-registers.png (252.1 KiB) Viewed 45888 times

: jaku5-duct.png (157.46 KiB) Viewed 45888 times

: jaku5-duct.png (157.46 KiB) Viewed 45888 times

Here is my SkechUp file:

Jaku5_cr_design_treatment_hvac_ray5.skp: (5.41 MiB) Downloaded 1434 times

Jaku5_cr_design_treatment_hvac_ray5.skp: (5.41 MiB) Downloaded 1434 times

There is a delay in the speakers shipment, but just to not come to this new place empty handed i took my old Mackies MR5 and did a pre baseline test

That is stands are lightweight aluminium and carpets is still in place. Anyway here is the REW file, I hope I did it correctly:

Jaku5_pre_baseline_191006.mdat: (7.11 MiB) Downloaded 1552 times

Jaku5_pre_baseline_191006.mdat: (7.11 MiB) Downloaded 1552 times

Thanks a lot for reading

#2

Hi there Jakub! Welcome again! :yahoo:

Glad you made it over here...

Excellent first post, too.

The room is on ground level, floor is strip footing filled with concrete, wall with window on it is an outer wall made from concrete masonry unit and styrofoam (12 concrete, 8 styrofoam, 24 concrete, 45cm total thickness) and other four inner walls are made from brick (25cm thick). Front wall is next to the garage, rear wall is next to a hall connected with kitchen.

That construction should get you decent isolation. Is what you are getting at present, enough for what you need?

The floor surface is roughly 13.5m2 and ceiling is 270 cm high.

Small, but not too bad, and the high ceiling is nice.

I plan to put the desk so that the window is on my right side when mixing in order to place speakers along the longer wall. I’m also considering flipping it so that the window is behind in case this 30cm deep window cavity turns out to compromise symmetry.

I would suggest trying it both ways, setting up as accurately as possible, and using REW to check which way works out best, both for symmetry and also for general room acoustics. The down side of having the window behind you, is that you'll need to cover it up with treatment... the rear wall of any small room always needs a lot of treatment. So from that point of view, it would be better to have the room facing the way you show it now.

The speakers will be Genelec 8030 with 7050 sub.

Nice! That should be a good setup.

Though I’m aware soffit mounting would probably be best I could do I don’t feel like being able to construct them properly for now and it also might exceed the budget quickly,

Have you set a final budget already? Flush-mounting your speakers in soffits really can make a great improvement to the overall acoustics. On the other hand, it does cost money to build them (even if not a lot...), and you could certainly add the in at a later stage, if your budget doesn't allow for that now.

so instead I hope to reduce the SBIR issues reasonably by placing speakers, on massive stands, tight against 10cm thick panels and a little bit with speaker cabinet construction.

What do you have in mind for the "a little bit with speaker cabinet construction"? The rest sounds fine, but I'm curious about that part...

I got some measurements done with SPL meter and music playing in the room at 95 dBC reads about 60 dBC in the kitchen and living room next to the room (ambient level there is 35 dbA) and 75 dBC and 70 dBC at the door and window respectively.

At the line of the property it reads about 50 dbC and the local code states max 50 dbA for the day and 40 dbA for the night

You should be fine, then, because dBC is a lot more sensitive to low frequencies than dBA... thus, what you measured at 50 dBC is actuallly quieter than 50 dBA, by several decibels. How much quieter depends on the music you used for the testing: if it was very bass heavy, and your sub was blasting loudly, then there could be maybe 15 or even 20 dB difference (in other words, your 50 dBC would measure more like 35 dBA), but if there wasn't so much bass in there, then the difference would be less. But still useful.

OK, so it looks like you are fine legally, but what about audibly and "neighborly"? Was it annoying at the property line? OK, so you won't normally be playing at 95 dBC, probably more like 80 for typical mixing, but it's still a good thing to check that, as you might want to boost the levels every now and then to "check the bass", as mix engineers like to say...

I also noted that you are getting about 35 dB isolation inside the house (to the kitchen), which isn't too bad. Is that enough? My guess is that just by sealing the doors and windows better, you should be able to improve that by a few dB. And replacing the door with a solid core door that has a rubber seal all around all four edges, would be even better.

I have to run now, but I'll get back to respond to the rest shortly... I just wanted to get the first part answered while I had a couple of minutes... Stay tuned!

- Stuart -

#3

... continued!

Basic treatment plan is superchunks in three right angle vertical corners (ROCKSONIC SUPER 10CM, 38KG/m3 density, ~78cm across corner), 2 panels on the front wall, behind the monitors, tight against the wall (PT80 80kg/m3, 10 CM), 2 side panels on the first reflection points (TOPROCK SUPER 15 CM 40kg/m3) 10cm gap from the wall, floor to ceiling on the rear wall treatment (TOPROCK SUPER 15 CM 40kg/m3). Hardbacked cloud on the ceiling.

Looks like a good basic plan, assuming you don't have a symmetry issue with the side walls. You might also need some wood slats to avoid removing too much high end. The panels behind the speakers could also be wider.

These are the specs provided by manufacturer of PT80 (80kg/m3):

That looks pretty good.

You might also find this "freebie" useful: Soundman Simple Dynamic Adjustable Acoustic Absorber Panel Tool for SketchUp You can adjust several parameters to make it fit your needs. Let me know if you like it, and find it useful.

Here is the design of treatment in skechup including advice I got from Stuart on John's forum:

I'm pretty sure that's good advice!

206 cm x 105 cm frame, 2 cm thick MDF/OSB hard backed, angled 15 degrees. Thanks a lot Stuart for providing that ray tracing tool.

I'm glad it's useful! That's why I released it: I find of very useful for figuring out angles and reflections. For those who don't know what that is, here's the link: viewtopic.php?f=9&t=2

I would suggest boring large holes or slots in the front, rear, and side faces of your cloud. Helps to expose more insulation to the room, and also does a bit of diffusion.

1. Rip out the carpet
2. Do the baseline REW test
3. Superchunks and panels behind speakers
4. REW test
5. Rear wall treatment and side panels
6. REW test
7. Ceiling treatment
8. REW test
9. Door replacement and floor finishing
10. REW test

But now I'm thinking maybe I should take care of isolation and HVAC first so replace the door and stuff the window before any treatment comes in.

Right! Add that as "step number 0" to your list.

Speaking of HVAC I did some calculations:

The general plan would be to divide HVAC in two stages. First make a ventilation system now and then save some money during winter and install the mini split once temperatures start to rise (around March).

The room is ~38 m3 so I would need 228 CMH = 3,8 CMM = 134 CFM of an air flow. 25% of makeup air would then be 57 CMH = 0,95 CMM = 33,5 CFM which should be also enough for two people to be comfortable in the room.

For my ventilation I was planning to go with small HRV unit, 125mm diameter flex duct (which would give me an air velocity of 1,29 m/s) and two silencers (one for intake and one for exhaust) outside the room but after some more thinking I am kind of leaning towards inline fan and making fresh air intake in front and using the existing passive exhaust at the back because this is not huge amount of air and I'm wondering is HRV really worth it in my situation.

Do you have large temperature differences between indoors and outdoors, where you live? If the difference is only a few degrees, then it probably isn't worth it. HRVs are only efficient / justifiable when there's a large difference in temperature: say more than around 15 or 20°C. If it gets very cold in winter (less that 0°C most of the time, and/or very hot in winter (over 35°c most days), then yes, an HRV might be a good idea. Otherwise: not so much.

If you go with an in-line fan, then do be careful where you install it: Don't put it inside the wall, between your leaves! You will need access to it for cleaning, maintenance, repairs, replacement, .... So have it some place where you can get easy access to it, without needing to open up big holes in your walls...

There is a delay in the speakers shipment, but just to not come to this new place empty handed i took my old Mackies MR5 and did a pre baseline test That is stands are lightweight aluminium and carpets is still in place. Anyway here is the REW file, I hope I did it correctly:

The data is valid, so it looks like you did the testing correctly. There does seem to be a bit of a roll-off above about 1 kHz. That looks like it is probably speaker-related or signal-chain related, not room-acoustics related. Do you have any EQ applied anywhere?

There's also a difference between the left and right channels in symmetry, but it's not huge, and it's mostly in the low end, so that's probably manageable, if you want to keep your room oriented the way you have it. It will be interesting to see the results for the new speakers when they arrive.

Of course, the REW data is pretty ugly (T30 is 1400 ms! Even EDT is nearly 800 ms!!! :shock:

), but that's the way it should be for an empty room. All of your modal stuff is very clear, and several other things too.

Summary: your basic plan looks fine, so I would suggest that you get started on the HVAC part, and the isolation, as well as posting new REW data once your speakers arrive.

- Stuart -

#4

Thanks a lot for taking your time to read and respond

Soundman2020 wrote:That construction should get you decent isolation. Is what you are getting at present, enough for what you need?

Apart from the door and window sound leakage I think it is well enough.

I would suggest trying it both ways, setting up as accurately as possible, and using REW to check which way works out best, both for symmetry and also for general room acoustics. The down side of having the window behind you, is that you'll need to cover it up with treatment... the rear wall of any small room always needs a lot of treatment. So from that point of view, it would be better to have the room facing the way you show it now.

All right, will do once speakers arrive.

Have you set a final budget already? Flush-mounting your speakers in soffits really can make a great improvement to the overall acoustics. On the other hand, it does cost money to build them (even if not a lot...), and you could certainly add the in at a later stage, if your budget doesn't allow for that now.

Well the minimum budget is ~1000$, but there might be a possibility to stretch that a bit depending on economic situation and I have to admit that after reading through Jennifer's topic I am giving soffits a second thought

That being said I didn't realise that adding them at later stage is an option. My understanding was that flush-mounting would make most of my current plan's front treatment useless.

What do you have in mind for the "a little bit with speaker cabinet construction"? The rest sounds fine, but I'm curious about that part...

I remember reading somewhere that whole purpose of this egg-shape Genelec cabinet is to reduce resonance inside speaker, but perhaps it's negligible?

You should be fine, then, because dBC is a lot more sensitive to low frequencies than dBA... thus, what you measured at 50 dBC is actuallly quieter than 50 dBA, by several decibels. How much quieter depends on the music you used for the testing: if it was very bass heavy, and your sub was blasting loudly, then there could be maybe 15 or even 20 dB difference (in other words, your 50 dBC would measure more like 35 dBA), but if there wasn't so much bass in there, then the difference would be less. But still useful.

OK, so it looks like you are fine legally, but what about audibly and "neighborly"? Was it annoying at the property line? OK, so you won't normally be playing at 95 dBC, probably more like 80 for typical mixing, but it's still a good thing to check that, as you might want to boost the levels every now and then to "check the bass", as mix engineers like to say...

I also noted that you are getting about 35 dB isolation inside the house (to the kitchen), which isn't too bad. Is that enough? My guess is that just by sealing the doors and windows better, you should be able to improve that by a few dB. And replacing the door with a solid core door that has a rubber seal all around all four edges, would be even better.

It was hardly audible at the line so I hope sealing window would make it almost inaudible

As for the inside it could definitely be a bit quieter, but as you say sealing doors and working on lower volume most of time would improve situation and I think this will be enough to make things fine.

Soundman2020 wrote:
Looks like a good basic plan, assuming you don't have a symmetry issue with the side walls. You might also need some wood slats to avoid removing too much high end. The panels behind the speakers could also be wider.

Noted

You might also find this "freebie" useful: Soundman Simple Dynamic Adjustable Acoustic Absorber Panel Tool for SketchUp You can adjust several parameters to make it fit your needs. Let me know if you like it, and find it useful.

Nice, I will give it a try for sure

I would suggest boring large holes or slots in the front, rear, and side faces of your cloud. Helps to expose more insulation to the room, and also does a bit of diffusion.

Thanks, makes sense

The data is valid, so it looks like you did the testing correctly. There does seem to be a bit of a roll-off above about 1 kHz. That looks like it is probably speaker-related or signal-chain related, not room-acoustics related. Do you have any EQ applied anywhere?

I don't think I had an EQ anywhere but I will investigate this roll-off before posting any new measurements.

There's also a difference between the left and right channels in symmetry, but it's not huge, and it's mostly in the low end, so that's probably manageable, if you want to keep your room oriented the way you have it. It will be interesting to see the results for the new speakers when they arrive.

That is good to hear.

Of course, the REW data is pretty ugly (T30 is 1400 ms! Even EDT is nearly 800 ms!!! ), but that's the way it should be for an empty room. All of your modal stuff is very clear, and several other things too.

That is kind of good to hear too

Summary: your basic plan looks fine, so I would suggest that you get started on the HVAC part, and the isolation, as well as posting new REW data once your speakers arrive.

- Stuart -

Thanks again for taking time to review and comment on it :!:

Ok, so I will redesign the HVAC for the inline fan option, look into door design and seals, do some more research on soffits and post a base line test with new speakers

#5

I have to admit that after reading through Jennifer's topic I am giving soffits a second thought

Yes yes yes!

! Very much recommended, if you can find the extra budget. Even in small rooms they can give very good improvements.

That being said I didn't realise that adding them at later stage is an option. My understanding was that flush-mounting would make most of my current plan's front treatment useless.

Some of it will need re-purposing, yes, but the rear wall, side walls, and ceiling won't change a lot. And whatever you do on the front wall can be disassembled and re-used for the soffits...

I remember reading somewhere that whole purpose of this egg-shape Genelec cabinet is to reduce resonance inside speaker, but perhaps it's negligible?

That's part of the reason, yes, but a bigger part is "edge diffraction". It works like this...:

For high frequencies, a speaker works mostly like a spotlight, focusing sound in a cone towards the rear of the room. For low frequencies, a speaker acts like an open light bulb, illuminating in all directions equally: it is a "point source". Low frequencies spread out in a sphere around the speaker, highs as a "beam". So, considering those two extremes, obviously there's some point on the spectrum where this changes over from "spotlight" to "point source". There must be one frequency where everything higher is "spotlight cone" and everything lower is "expanding sphere". Yes there is: it's called the "baffle step response" frequency. It's actually not really a single sharp point, but rather the center of a wide range where things change over gradually from "cone" to "sphere". The graph of that looks like this for a typical speaker:

: BAFFLE-STEP-RESPONSE-CURVE-TYPICAL.gif (7.43 KiB) Viewed 45862 times

: BAFFLE-STEP-RESPONSE-CURVE-TYPICAL.gif (7.43 KiB) Viewed 45862 times

That shows the sound level you would hear when standing directly in front of the speaker, if it was putting out the same power for all frequencies. You can see where things change over from "cone" to "sphere" as a drop in level of 6 dB, and this is logical too: with the "cone" at high frequencies, all of the power heads directly at you, all in front of the speaker, none going back behind the speaker. For the low "sphere", half of the sound wraps around behind the speaker, and only the other half goes forward. So there's a drop of 6 dB (half the power). That curve covers a range of 4 octaves: 2 octaves above the "baffle step" point, and two octaves below.

It's called the "baffle step response" issue for a simple reason: all of this depends on the size of the front baffle of the speaker! The larger the baffle is, the lower the frequency is. For really huge speakers, the step is so low down that it doesn't matter: off the bottom end of the scale. So you could buy a really huge speaker, the size of your entire wall.... or you could take a small speaker and put a bigger baffle around it... by building a soffit !

Yup, that's one of the good things that flush-mounting does for you: it eliminates the power imbalance between the lows and highs, so there is no more "baffle step response" problem.

OK, but I still didn't get to edge diffraction... the above is just the introduction stuff that you need to know, so I can explain the edge difration thing, and the egg shape of the Genelecs.

If you think of it like this, it's a bit easier to get your head around it: for highs, there's a cone of sound, and for lows there's a sphere. So if you use your imagination, you can make a mental picture of a cone that starts out narrow for high frequencies, then gets wider and wider as you work your way down the spectrum... and eventually you get to the point where the cone is 180° wide: it spreads out exactly across the face of the speaker (the "baffle"). If it widens out any more, then the cone has to "wrap around" the sides of the speaker, and start spreading around to the back... and that's exactly what happens at the "Baffle step" frequency. At that point, sounds waves are not just going out in a cone, but they are actually spreading out sideways across the face of the speaker.... but then they reach the edge! And that's a problem. As the wave moves across the face of the speaker, it experiences one level of acoustic impedance, but exactly as it reaches the edge of the front face, there's a sudden big change in impedance, because now there's no more solid surface on one side:; suddenly, it is just air. That "impedance mismatch" messes things up: part of the wave wants to bounce back off that mismatch, and go back the way it came, part wants to carry on going the way it was, and part wants to "go around the corner", and head out backwards. As you can imagine, there's a lot of interference going on between those various parts of the wave beating itself up... which is not good for the sound of the speaker! This is "edge diffraction". Its the mess a wave makes of itself as it reaches the sudden discontinuity at the edge of the front face (baffle). Now, if you put a bevel on the edges of the front face, you reduce the problem. Because then the discontinuity isn't quite so bad: the impedance mismatch is a bit less. So some manufacturers make speakers with canted edges. And if you round off the corners of the front face, you reduce the problem even more, as the transition is a lot smoother. Genelec takes this to extremes, by making the entire cabinet round (or egg shaped), so there are no edges! This minimizes the edge diffraction problem. It is still there, though: just reduced in intensity.

The point where all this happens is at the point where the wavelength of the sound exactly matches the width of the baffle. For all shorter wavelengths (higher frequencies), the wave cannot "wrap around" because it is too small: the cabinet is bigger than the wave, so it just gets projected forward, in that cone. For all longer wavelengths (lower frequencies), the wave is bigger than the cabinet, and it can wrap around.

This implies that it should be possible to calculate the exact frequency where all of this stuff happens... and yes, there is: As I said, the effect happens over a range of four octaves, and the center point of the that is = 115824/W, where W is the width of the baffle in millimeters. It's that simple. That's the frequency where the wavelength matches the size of the baffle. Thus, for a speaker that is 20cm wide (about 8"), the baffle step would be at 115824 / 200 = 579 Hz. So everything above that is "cone", and everything below that is "sphere", with a transition zone of two octaves each way. If you had a much bigger speaker that is 1m wide (about 39") then it would be at 115 Hz... and if your entire front wall is the "baffle", at say 3m wide, then the frequency is 38 Hz... However, if you soffit mount your speakers properly, then it's not just the front wall... the side walls also become part of the system, to basically there is no more baffle step!

And since there are no longer any edges, there is also no edge diffraction. And since your speakers are now flush with the wall, there is also no more SBIR. And since you have now loaded the speaker more effectively, it can operate down to lower frequencies... and since it is in the wall, most of your modes are now minimum phase, so you can treat them with EQ... and... and.. and... and... and... There's just so much "good stuff" that a proper flush-mounted speaker soffit does! So many benefits...

Thanks again for taking time to review and comment on it Ok, so I will redesign the HVAC for the inline fan option, look into door design and seals, do some more research on soffits and post a base line test with new speakers

Sounds like a good plan to me!

- Stuart -

#6

Wow this took a while to digest but here I am

Seriously though thanks for laying it out like that makes total sense even with my very limited knowledge and I really hope you have that book on acoustics coming one day

I had to step aside from this project for a while, but I’ve been lucky enough to be able get some work done on cans in the mean time (I mostly do audio for games so there are times when critical listening is not essential when dealing with some more technical tasks and it is relief as working in headphones for prolonged periods can be really fatiguing at least for me), but had new speakers looking down on me with regret for far too long now so I hope to move on with this project at least a bit now.

Since my last update I got rid of the carpet and room was repainted in white (it was quite a long time since last painting, so it seemed like a good time to do it anyway).

Finally speakers arrived around November 2019 so I took new REW measurement but this HF rolloff persisted, even though I tried different mic and cables and soundcard but still no idea what might be the cause of it.

The sub arrived about a month later but that’s when I had step out a bit. Anyway here are the new measurements taken with new the sound card (old one went flank in the meantime) and sub recently.

Jaku5_baseline_210302.mdat: Jaku5_baseline_210302; (14.06 MiB) Downloaded 1150 times

Jaku5_baseline_210302.mdat: Jaku5_baseline_210302; (14.06 MiB) Downloaded 1150 times

HVAC

Initially I decided to ditch the idea of incorporating chimney in ventilation design since I had trouble calculating amount of static pressure it would introduce but my alternative plan was not possible because of electrical wires running all over the wall where intake silencer was supposed to be so there is no way to drill the ventilation hole there.

Current plan:

So getting back to chimney idea what seems to me from playing with some calculators and such is that its dimensions (14 x 14 cm) over the length of 5m would introduce a negligible amount of static pressure (even though it’s a rough old brick on the inside) comparing to 4.14m of 100mm duct planned for the intake in the front of the room.

Intake at the front:

: intake

Exhaust at back:

: exhaust

Hole leading to chimney:

: chimney hole

Overview:

: hvac_overview

Silencers:

From what i found online thickest duct liner they offer here is 2 cm thick but I’m guessing given my moderate isolation needs and no 2 leaf system this should not be critical. Sadly I didn’t find any acoustic data for it neither. It’s called INDUSTRIAL BATTS BLACK 60 and of course only sold in large quantities

And the MDF Boards are 18mm here so to make things a bit simpler I’m planning to go with that for the case and 10 mm for baffles.

I redesigned my silencers (basically scaled them down by 20% since I plan to use 100mm flex duct insted of 125mm):

: intake_silencer

: exhaust_silencer

From what I’ve been able to calculate this design would result in 57.2 Pa, so I am considering this Harmann ML 100/300 fan for the job:

: fan_spec

DOOR

Finally found a contractor who is willing to make and install them, plan is to make them 3 layers of MDF and they will probably weight somewhere around about 120 - 150 kg. Some really great intel on that in Steve’s thread as well as site built door pair thread in reference section. First concern the contractor expressed when discussing the design was the hinges that would keep such heavy door up so I take it as good sign

So the doors will hopefully be the next step and we’re scheduled for it sometime in April.

Since it looks like the making and installing the doors would consume my total initial budget I’m yet to set the date on HVAC and see if I can afford the mini split to have it installed together with silencers and fan.

And here is the photo from setting up the measurements

: measurements

Thanks for reading and take care everyone

#7

jaku5 wrote:Source of the postFrom what i found online thickest duct liner they offer here is 2 cm thick but I’m guessing given my moderate isolation needs and no 2 leaf system this should not be critical. Sadly I didn’t find any acoustic data for it neither. It’s called INDUSTRIAL BATTS BLACK 60 and of course only sold in large quantities ...

If you have not already bought the duct liner, let me know how many square metres you will need and I can check how much I have left, quite probably enough for two silncer boxes.

I paid £448.55 for a 20m roll including delivery from the UK. That works out to 121 zloty per metre. INDUSTRIAL BATTS BLACK 60 may work out cheaper as I find most things are cheaper in Poland! As both Poland and Slovakia are in lockdown now I would need to send it to you as neither of us can make the 480km journey between Kampinos and Poprad right now.

You can see the roll and my lined silencer boxes in post 56 of my build topic, here.

#8

Starlight wrote:Source of the post
jaku5 wrote:Source of the postFrom what i found online thickest duct liner they offer here is 2 cm thick but I’m guessing given my moderate isolation needs and no 2 leaf system this should not be critical. Sadly I didn’t find any acoustic data for it neither. It’s called INDUSTRIAL BATTS BLACK 60 and of course only sold in large quantities ...

If you have not already bought the duct liner, let me know how many square metres you will need and I can check how much I have left, quite probably enough for two silncer boxes.

I did not, thanks for the offer! Let me triple check how many I would need and I'll send you a message later this/next week

Starlight wrote:Source of the postI paid £448.55 for a 20m roll including delivery from the UK. That works out to 121 zloty per metre. INDUSTRIAL BATTS BLACK 60 may work out cheaper as I find most things are cheaper in Poland!

When studying in Cieszyn few years back we had some collaborative projects with students from Slovakian university and I remember them being amazed with a price of whortleberries here in Poland :lol:

Starlight wrote:Source of the postAs both Poland and Slovakia are in lockdown now I would need to send it to you as neither of us can make the 480km journey between Kampinos and Poprad right now.

Oh yes which is a shame as I actually have some great memories from ski camp in Ždiar as a kid and wouldn't mind visiting the neighborhood again one bit

Starlight wrote:Source of the postYou can see the roll and my lined silencer boxes in post 56 of my build topic, here.

And thank you again, looks like I got some more catching up to do here

#9

Ok rather modest update time. We had a slight delay with contractor but things finally started this week and old door had been removed.

Since this probably marks the start of actual construction phase I updated sketch design per Stuart suggestion to make front panels behind the speakers a bit wider. (Used dynamic absorber component from freebies section of the forum for this, simple and neat!) and that hopefully locks the design (apart from all the little details I'm sure I missed).

: Wider front panels

Looking forward to having new door come in next week / two weeks.

Thanks for reading.

#10

Nice to see you moving on this again. I forgot you have Genelec 8030s, same as myself. I've decided to definitely soffit mount them by the way, but not likely to start doing this for a few months or so. Does the 7050 sub work well with them?

Cheers!
Jennifer

#11

Thanks Jennifer! Loving the speakers even in untreated current space, but due to their shape I expect soffit mounting them to be quite a challange, so my thinking now is to get new space up and running in the current design form and then possibly upgrading to soffits next year or so (though your post with list of "rules if soffits" made me rethinking that again

) So for now wishing you best of luck in flushing yours and something tells me you're going to do a great job with that

As for the 7050 I'm afraid I can't tell you much since I only used it in current untreated room so far, but just being able to hear it produce this low frequency content I have feeling its going to play out real nice in a bit more controlled environment. I'll be more than happy to update this report once some treatment goes into new room eventually

#12

Ok, so time for an update. Here goes the photo sequence of placing new doors:

installing frame:

: installing frame

: installing frame

: installing frame

: installing frame

hanging raw MDF door

: raw door

: raw door

: hinge

Completed door with closer

: finished door

Prior to door replacement I redid the noise measurements, this time with sub. With music playing at 95 dBC from the room I measured 85dBC (right at the doors on the other side) with old door and 60 dBC now with new one, so pretty happy with results. Might consider adding 2nd layer of seal in future.

Next thing is ventilation, we started with making a hole for fresh intake at front and the next step would be to seal it with silencer.

: hole for fresh air intake

#13

Dzień dobry, Jakub.

That door is a serious step forward. I would guess the 35dB isolation it provides is similar to the wall, so that is good to have achieved that level of isolation. Well done!

The fresh air hole is a good start to the next step. I look forward to seeing how that turns out.

#14

Dzień dobry

And thank you most kindly for the words of encouragement

One thing I forgot to mention is the fan I decided to get is TD SILENT 250/100 already mentioned on this forum. The Harmann ML one I posted the specs earlier in this thread is apparently only safe to operate in no less than -5 degrees Celsius and it can certainly get colder in the garage (where then fan will be placed) during winter here. TD SILENT promises operation down to -20 degrees Celsius.

#15

Glad to share some progress. At the begging of December contractor showed up and we installed silencers he built and made the hole in exterior wall for the fresh air intake. We had to change its position and lower it a bit.

We then installed the fan and some low noise can be heard in the intake sleeve that's penetrating the front wall. It's faint but audible and my guess is the sleeve should be covered in duct liner as well (which lack of I obviously overlooked in my design), so I'm waiting for the contractor to drop off leftovers and see if there's enough.

I did similar test to one Jennifer did on her system (using PRM1 mic used for other measurements) and looks like with fan on (low speed) it would still meet the NR10 curve, measured from the mix position and it's not audible when playing the music but can be surely heard when listening to some quiet ambient recordings etc:

No fan:

Fan:

Also we should probably move the fan further away from silencer, closer to a exterior intake and add a filter box and change the duct for an insulated one.

It seems the fan running on low speed is underspeced a bit, as the CO2 levels can gaet up to about 700 ppm with only me in the room and cold winter air blowing into the room, so when I'll be changing the fan placement I might put it on high speed and add speed controller.

Then finally insulation had arrived. From what I was able to get I went with Rockwool Superrock 38kg/m³ for both 10 and 15 cm treatment.

During the weekend I stuffed the window cavity and measured almost 30 dB C isolation improvement there. Then I redid the baseline REW measurement. Next thing I placed placeholder panels behind the speaker and run another test.

Looks to me they're reducing decay times at above 100 Hz quite nicely.

Before:

After:

Next we made superchunks on the front wall and another test:

Next we proceeded with rear wall treatement and another test:

We then placed side panels on first refelection points:

Next I tried to detrmined suitable position for sub, by placing it on mix pos and playing pink noise and then followed sub manual for phase alignment settings and run another test:

That's where the room is now you can download the mdat here:

jaku5_sub_phase.mdat: (12.49 MiB) Downloaded 940 times

jaku5_sub_phase.mdat: (12.49 MiB) Downloaded 940 times

As can be seen I still have the HF roll off issue (amongst others

) and I might have figured what's causing it. When I said I ripped the carpet I didn't mention there was a thin layer of whatever they used to glue it and it was impossible to get rid off with any methd I could think of. Hopefully this picture shows what I mean (actual concrete and material from under the carpet):

So next what I think I plan to do is cover the floor and bass traps with plastic (thinking of something like 0,03kg/m3) and attach it temporarly with tape and see how that affects the highs. And then work on superchunk above the door and door treatment and maybe lay laminate panels on the floor.

All in all it feels really nice to see this sketchup model I started designing on Christmas 3 year ago slowly come to reality so thanks again to all of you for making it possible!

Thanks for reading.

PS. I think the post above is a spam

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