Small top floor mixing room [in progress]

here some pics. Happy Xmas :)

Short question for the ceiling over the monitor and window section cause I started to build up the frame... is it good to angle the ceiling absorber from 44cm to 20cm as shown on the sketchup pic below? I would put in lighter rockwool there "Sonorock 6kPa". I hope to cure the still existing 1000hz reflection problem but also the deeper midrange (300-500hz) by the material thickness of 20-30cm in the first reflection part and 44cm max over the window. Or is it not a good idea making it so thick in considering of the new measuries two posts above? Best regards Aaron

Angling would be fine! That would help to give a bit better broadband coverage. How thick are you planning to make it? It doesn't need to be 20 cm thick on one end and 44cm thick on the other: You could, for example, make a panel 15 cm thick and just angle the entire panel, leaving a small air gap at one end and a large air gap at the other. That would be just as effective. Of course, if you really want to make it that thick, there's no reason not to! (Except cost... :) ) - Stuart -

Hi Stuart, i finished the ceiling construction after reading your post on 28. but i was not able to upload the pic with my ip*d :). Thanks for answering.

today is a good day cause i could make some new tests and photos. I can tell about improvements happened to the sound. What i did so far: Finished the front 30cm superchunk wall under the window and beside the window there is added 10cm of 703 like wool, preparing the corners for the hangers (i will get wood fibre next week). The ceiling absorber are finished too. There is a angled one head over the speakers 40cm to 20cm and like you recommended a angled one 15 to 10 cm head over the sitting position. It looks nice and enlarge the room anyhow :wink: The room sounds even much more better than before. The sound image is very nice now but i hope the slot walls will help getting the mid range in a better shape. There are reflections from the backwall and side walls that i think cause the canyons in the frequency range. What do you think about the up-to-date measuring and the coming slot walls? Should I angle it or better tune it to problematic midrange frequencies with 50-80% wool inside to make it broadband :?: Does it make sense putting something absorbent on the backwall and measure again to find out the exact frequencys that cause the backwall and both sidewalls? regards Aaron

Those graphs are starting to look pretty good! I'm glad it is sounding better in there as well. :)

What do you think about the up-to-date measuring and the coming slot walls? Should I angle it or better tune it to problematic midrange frequencies with 50-80% wool inside to make it broadband

I would angle the lot walls slightly, yes, and also put plenty of wool in them, but make sure it doesn't touch the slats themselves. Also, don't forget to carefully seal the cavity behind the slats! It has to be airtight in order to work. You could try to tune some of those slats around the problematic frequencies: it can't hurt! Those deep dips might be reflections, but if you are angling your slot walls and you do tune to those frequencies, you'll be covering a broad spread anyway, so that's fine. Also, you seem to be testing with the volume levels a bit low: normally rooms should be tested and calibrated at 85 dB (each speaker individually).

Does it make sense putting something absorbent on the backwall and measure again to find out the exact frequencys that cause the backwall and both sidewalls?

Yes! You absolutely do need something absorbent on the rear wall anyway, and thick, so you might as well put it there now and measure again, before deciding if you need additional treatment. But your graphs seem to be showing reasonably even response, withing about +/-8 dB mostly, with very few exceptions. Looking good! :) - Stuart -

Hi Stuart, very nice to read that the measuries are also looking good to you too :) :yahoo: It was interesting measuring with different absorber setups today. For testing the actual roommodes, I put two 100x60 and 10cm thick 703 type absorber onto the end of the sofa leaned to the backwall. Freqs in the range between 160-190hz, 290hz and 600-1000hz have changed. The graphics below are mostly one speaker with the current referenz measure with no absorber and the measure with absorber. The colors and function is labeled in the footer of each pic. One mode at 260 did not even change (this seems not to be a mode of the back or sidewalls). Maybe if i had used 20cm of the 701like wool it would improve much more of the two modes at 160 to 190HZ on the backwall. So i think i need to replace the wall and put in 20cm rockwool or should i still use hangers? If so, what deph would be good for the backwall cavity? Maybe i do not need such a deep cavity as planned. I added a pic of the ceiling corner on the backwall, there would be also space for a hoizontal superchunk long ago the ceiling. The results of testing the sidewalls with the absorber were frequency-changes at 192hz, 281hz, 370hz, 367hz, 452hz. The right speaker-response was even flat on 150hz for any reason while the left speaker has a deep dip. Putting an additional absorber in the right corner of the backwall could increase that a bit. In the right corner on the backwall would be space for a vertical superchunk or better 3-4 hangers? I´m not really clear what frequencys i should use for the slot wall. Can the slot wall be effective at 150hz or should i only focus on the mids starting at 200hz and angled to 500hz for the slot wall? Can i use 5cm thick very low dense polyester wool? I did a measuring only with this pwool added to the left sidewall to find out what it does absorb. Not as much but highs down to 600hz. I´m afraid using the wrong wool and the sidewalls will have no useful effect... :| (added the measuring pic of the pwool - last pic below if it helps to judge the wool.) Aaron

...hoped to get better results with hangers i build the last two days but the result seems deflating. Some 3-4db improvements at around 200hz and the highs but a bass drop at 60-70hz on both speakers... Maybe i did something wrong,... I tryed to face the hangers to the sitting position with the plan site but i could only place 2-4 hangers then so i made them face to the sidewalls... :roll: What do you think, is it good that i added hangers or can it be that any additional basstrap makes the bass between 60-70hz more worse in my case? best regards Aaron

Finaly i replaced the hangers with low dense (sonorock) superchunks and got some nice results on the right speaker. The bass range seems to be even flat right now. But the left speaker has some curious measures. There are two valleys at 60 and 104hz i could not realize why they were produced :shock: sincerely Aaron

yesterday i removed the left part of the backwall and did a measure again. The bassrange at around 60HZ is improved somewhat. Also interesting to see that the highs at around 3khz and 13khz are even flat the first time. [I think i gonna wait with the slot absorbers till i have the room construct ready with the new coming respone] I will remove the middle part of the backwall today too. Stuart, i need your advice again. What should i do with the backwall? I guess i need to make it as big as possible to provide solving the bass problem. What do you think of making a 15cm absorber wall and enlarging the room behind with an angled storrage room? Or Plan B making a 20cm symmetric rockwool wall with two layers drywall on the outer site? Or Plan C if it is necessary to make a thicker wall. If Plan A with the angled storage room wouldn´t be bad for the acustics i´d like this version putting printers and office things in the left side. thank you very much Aaron

this is the actual backwall layout. The measures based on this but without slot walls and closed door. Aaron

I would appreciate any opinion about the rearwall (planA,planB,planC above) very much. Thanks Aaron

Sorry about the lack of response, Aaron! Lots going on here... To be honest, your graphs are looking pretty good, at least down to 70 Hz, and that's a major achievement already for a room such as yours! Those waterfall plots are very clean. Sure, the frequency response isn't flat, but you'll never get it perfectly flat, not in that shape/size room. You are within roughly +/- 10 dB from 20 Hz upwards, across most of the spectrum, and those higher frequency dips are most likely reflections and comb filtering from other surfaces in the room. The lower frequency dips are likely to be the room structure itself getting involved (resonance in the walls, floor, ceiling, and structure) and there's not much you can do about that. But you might still be able to tame things a bit more, so here's what I would do: My suggestion would be to leave that center wall as it is, but I would also put something on the OTHER side of it (the side facing the speakers, above the sofa. I reckon that some of your issues are coming from there. Maybe put 10cm or 15cm of absorption on it. You could even angle it, thicker at the top and thinner at the bottom. So then you'd have the center rear wall with similar gaps on each side, and a large space behind it. I'd put some hangers in that large space, sort of like Plan "C", but make that area as deep as you can. 50 cm is OK, but if you could spare more space, that would help. For example, 75cm would give you enough space to line the walls with 10 cm of insulation, and still have plenty of space for lot of hangers. Space the hangers about 10 inches apart, and angle them a bit, so that you can make them bigger. I think the reason why you weren't getting much effect with the hanger on the front wall, is because they were too close together, and they weren't angled: If you would have angled them at maybe 30 to 60 degrees, I think they would have been more effective. But what you did with the insulation there is fine: you don't need to change that. Anyway, that would be my suggestion! - Stuart -

Soundman2020 wrote:

Sorry about the lack of response, Aaron! Lots going on here... To be honest, your graphs are looking pretty good, at least down to 70 Hz, and that's a major achievement already for a room such as yours! Those waterfall plots are very clean. Sure, the frequency response isn't flat, but you'll never get it perfectly flat, not in that shape/size room. You are within roughly +/- 10 dB from 20 Hz upwards, across most of the spectrum, and those higher frequency dips are most likely reflections and comb filtering from other surfaces in the room. The lower frequency dips are likely to be the room structure itself getting involved (resonance in the walls, floor, ceiling, and structure) and there's not much you can do about that.

Thanks so much for your response! I was willing to build the rearwall tomorrow and it was very good reading your suggestions.

My suggestion would be to leave that center wall as it is

too late, i removed it today but i think it is not as bad, i will follow your advice with the plastic strips behind the fabric.

(the side facing the speakers, above the sofa. I reckon that some of your issues are coming from there. Maybe put 10cm or 15cm of absorption on it. You could even angle it, thicker at the top and thinner at the bottom.

Nice idea, i will do it that way.

but make that area as deep as you can. 50 cm is OK, but if you could spare more space, that would help. For example, 75cm would give you enough space to line the walls with 10 cm of insulation,...

This is the thing - I could do a straight wall that would be 40cm deep total for insulation. I think it must be as deep as possible too... What would be if i take plan A and fill out the complete right part with low dense rockwool? I would have a 40cm to 1m big superchunk but not symmetric behind the sitting position... would be symmetric important at this point? I guess the most reflective point for the deep frequencys is the bottom right corner of the floorroom. It is 30cm brickwall each side. Reflections would need to go trough the thick 1m part of the superchunk. I could insert a second door then but if this version is not better then the symmetric 50cm rearwall i wound forward thinking about that.

I think the reason why you weren't getting much effect with the hanger on the front wall, is because they were too close together, and they weren't angled: If you would have angled them at maybe 30 to 60 degrees

Very good information (I had the problem understanding Johns Hanger pic - i was not clear if 15cm space between the cores of the hangers or the absolute space between the hangers was meant :oops: ) Thank´s for taking the time to answer my questions Aaron PS: would it be better doing it this way showed on the picture below or a symm.50cm deep straight wall?

here are two drawings of both ideas. Plan C isn´t bad with the angled rearwall and superchunk on the ceiling and maybe it does absolutely suffice or do you think is the revised "Plan A" better?

"Plan C" still looks like the best option to me! - Stuart -

Ok Stuart, thanks for taking a quick look into this thread :). I will have a lot to do with this wall tomorrow and over the weekend and i will tell you how it does sound after that. :) But everything is better than braking down an old dusty wall... This was very dirty :horse:. Have a nice day :!: we have evening right now ;) Aaron

puhh, it took me some days building the rearwall but it is finished and i did some measuries yet :) From 200HZ everything looks much much better but there is a new 80HZ drop on the right speaker that made me jump :| . What is the reason for the 80hz dip... does something make sense that this dip became? When i removed the left side of the old wall and (on the right side was the closed door) the bass range of the right-speaker was even flat... it would be nice if I can get sort out this frequency dip but i have no idea how i can proceed. Hopefully you have an idea :) If i put additional rockwool before the corner-bass-trap the 80hz dip gets more worse and if i remove rockwool from the corner trap the 80hz dip gets better. This is contrary to my tought there can not be anough bass trapping... Maybe i need to remove the rear-corner-bass-trap? Thanks so much Aaron New Rearwall: I did not build hangers, it was so much work to build 2 extra long hangers that i decided to fill it with sonorock rockwool completely (hopefully not the badest decision). The angled front inside the room is closed with fleece and thick plastic foil strips. The corner bass trap in the right last corner on the pic is 50x50cm sonorock + the attached 50cm wall. So 1m total on the longest side.

Could it make sense to remove the rear corner trap? Anyhow it seems to enlarge the 80hz dip. Another idea (if this is a new roommode cause of the 2layer drywall) and maybe a bit gruffy to drill some 6cm holes into the new rearwall on the floorside. I can not deconstruct the wall as i glued and screwd the drywalls together. But i guess the 80hz go trough the wall and it may does not make sense to do so... If the absorption is the reason, this can be "easily" changed from the room inside :) wuaa... Thanks Aaron

this is a nother idea and the backwall from the floorside. If this is the only way to get rid of the 80hz dip, what material should i use? I could make a decoupled plate absorber-like inlay of 2mm steel or simply 3mm wood that i glue into the cuttings with two wood lips on the inner side to hold the plates. It could pass the 80hz to the floor and maybe vibrate a little bit for absorbtion... Do you have any opinions about that? :idea: Aaron

here is the comparsion chart of the rearwall steps (right speaker): green: old rearwall with 5cm thick light bricks. red: partially opened old rearwall - opening on the left side. blue: new 50cm shifted drywall - 2,8cm thick and 50cm rockwool on the inner side. loooks like the 87hz are not new :oops: . They have been there with the old wall too but not as heavy. I thought the thinner drywall could be the reason that makes things worse but it was even better with the left opening on the old wall and everything i put into the floor space did not change the measure, so I send a 87hz sinus signal trought the speaker and listened outside the room on the floorside and could not hear much going through the drywall... It is very quiet in the floor so i guess it must have something to do with the left part of the rear-drywall - diagonal to the right speaker. It not seems to be a roommode coming from the massive outer wall at the end of the floor . Maybe i have to cut 2-3 squares into the drywall on the left side and close it with a thin sheet...:?: Hope this graph helps to find some logic anyhow... all best Aaron

Hi Aaron! I can't give you any advices on your problem as I'm not an expert, but I just want to bump your thread up :D I'm struggling the same kind of problems than you are.. You have also a dip at near 180-190Hz. Looks like you are fighting against the nasty room mode.. Don't know have you followed my construction but in my room there's a 10 db dip on 110Hz. Otherwise quite straight... And that dip is only at right speaker.. Entry door in my CR is on a left wall at the back, so there are not much absorbtion. I've got little better results when I placed several rockwool bats against the entry door in the corner.. (left wall) Have you tried to put absortion where you have now the storage room? -Janne

Hi Everyone, here are the actual measures of the room. What i did so far: *Removing the drywall-> rearwall again but i let the 40cm insulation between the room and floor. *Using 0,5mm pond foil instead thick PP foil on the rearwall (it made the bassrange btween 60hz and 300hz 3db better) *Building two slot walls tuned to two frequencys and broadband 60-100hz and 230-300hz *Painting the slats *Making the front insulation 20cm thicker with 5kPa wool made a huge different of 6db on 70hz instead using 6kPa rockwool #Experience: #Slot walls: I rebuild the slot walls three times total. The reason was i used PP Wool for the first time and it was way to dense. When i generated a tune of the slotwall resonance 100hz, the wall worked like a reverbator and the reverb time was very long after stopping the signal. Don´t use any very low dense pp wool in a slotwall! It wound make you happy. So i used 10cm 6kPa and 5cm 16kPa wool and the effect of the wall was much better, it did absorb around 6db better than before. But there was still a low reverb that i did not like so i rebuild it the 3. time and added a second layer of the 16kPa wool to have totaly 10cm 6kPa + 10cm 16kPa. The fabric does not touch the slats but the absorbtion effect got worse 3db but the reverb was no more there anymore. I stayd with to save my nerves ;) The total absorbtion effect of the slotwalls and the tuned frequencys was only 3-6 db depending on how much and what wool i used in the resonator room. But it made the Room much more better in the high frequency and it is also looking nice :) #Porous absorber I did not belief this before i had have not tryed it myself but the difference between 5kPa and 6kPa seems to be massive on absorbing bass depper than 80hz. You might consider better using for >40cm bass absorber 5kPa insulation instead 6kPa. In my case it was an effect of >6db. #Measures Some of my measures are irritating. I needed to shift my speakers several times to work on the ceiling and walls. When i turned them to the first position they were shifted some cm and this some cm made few huge differences in the measures. I could cure some db in the bassrange by fine tuning the position and angle of the speakers too. #Foils Using foils is well known here but there are not many suggestions about different foil thicknesses. You can buy very thin to thick foils in a building store. From my own experience in this small room it is much better using thick foils everywhere at the ceiling sides and rearwall. The only full absorbtion area is the front wall. I tryed different foils and absorbtion areas from making holes and slots in foils to using no foils on the rear wall and the best thing i went for was buying a 0,5mm pond foil i nailed onto the whole rearwall. I think every foil is a kind of membrane that starts to reflect depending on the thickness and starts to vibrate depending the weight and size. Anyhow i can not explain why but the pond foil made the whole bandwith 2-3db better from lows to highs instead of a thick ppfoil i had used before. Now, I gonna experiment using 15cm 50kg rockwool absorbers on the sides for cureing the 200hz dip. One 6db/100hz mode seems to be caused by the reflection of the slats /width 3,5m between the slotwall ends. but all in all it looks way better than before i think :-) The bassrange is only a broad dip that is 6-8db deep at 100hz. Here are pics:

Wow! Nice improvement from your earlier measurements! Place is also starting to look awesome!! Keep up the good work :D -Janne

Yeah, I'll second that! The response is looking much better, and so is the room! - Stuart -