John Sayers' Recording Studio Design Forum

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 . 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
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

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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

-Janne

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http://www.myspace.com/moonwagonfin

http://www.miamiwiseguys.com/

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

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Nice to read your feedback Stuart and Janne,
I'm very happy with the small computer room that you have planned and i can recommend to everyone putting the computer in an other room. it does not heat up the room as much, quiet and it is much more better for the electronic vibrating not as much as it would do under a desk.

You can see on the picture above the corners between both angled fronts and the slot wall.
I will enlarge the angle a little bit with 10cm 5000kPa insulation and 5cm air space. Hopefully i get cured the 200-230hz mode that seems to be a reflection of this corners.

Yesterday i finished a second cloude that is between the rear cloude and the hard fixed front cloude.
Also draped the left part with 10cm insulation and 5-20cm air space. It improved the -6db 100hz mode 3-4 db so this mode is looking good now on both speakers.

The left speaker has still a -10db problem on 50hz. I found out it has something to do with the untreated storrage room, that acts like an amplifier horn with the angle at the front i have space to build a helmholz resonator behind the electronic in the future.... for now i have anough to do with treating the front and the details at the ceiling

Thanks so much
Aaron

... finaly after many hours fighting with the left speaker room mode and reading thousands of threads about passive and active panel absorbers i simply used my subwoofer as panel resonator in a kind of DBA placement but only with one subwoofer (+ both 300 that acts like stereo front subwoofers). I read many interesting articles about modding a subwoofer to a tuned resonator by playing around with polarity and well i could hit the bulls eye by placing subwoofer on the opposite of the problematic wall

The subwoofers chassi is facing to the reflecting wall on the other site and erases the wavelengh totaly. On the listening position i have now a very flat response on both speakers. I could also find out that the angled inner part is causing the 200hz mode on both speakers. I will build an additional cloude for that purpose. I´m totaly happy now with the sound
Never give up with a small room. It sounds awesome and soooo big now!!!

Aaron

Active acoustic cancellation! Man, you sure do go to extremes for perfection, don't you! But it just goes to show that with perseverance, you can get great sound in a small room. I must admit, that it turned out better than I expected: with that size and shape of room, I never thought you'd be able to get to where you are now! A job well done.

I sure am glad that it worked out for you, Aaron, and that we could be of some help for you on the forum.

(If I'm ever in Germany again, you might find a stranger from Chile knocking on your door with a bottle of good Chilean wine in one hand, and offering to trade that for an hour listening to your system.... )


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

you definitely contributed a lot. I have learned a lot from you using more the calculator too. Thank you so much
And if you are in Germany again, you are very welcome for a wine and a listening session .

Aaron