Improving my studio

Hi! Thanks. :) The rear wall is a stud frame with 25 cm of 50/75 m3 rockwool, covered with fabric. No slats, just rigid insulation.

ok, sounds right then... I saw you built another wall behind the rear wall to get a symmetry, right? I remember John saying that you don't need symmetry for bass traps/absorbtion, so it must be something else. and the effect is not as expected (when i look to your measurings) because the second wall hasn't the same dense, weight compared to the outside wall, so it's unnecessary from my point of view... You could may add a second cloud, starting where the first cloud ends, sloping down to the rear wall and put some more hangers above the cloud... as i said before, i'm no pro, just a little swiss knife, so let's wait what the experts have to say! greez Roman

I saw you built another wall behind the rear wall to get a symmetry, right? I remember John saying that you don't need symmetry for bass traps/absorbtion, so it must be something else. and the effect is not as expected (when i look to your measurings) because the second wall hasn't the same dense, weight compared to the outside wall, so it's unnecessary from my point of view...

Yes, I finished the second wall. Steve told me to try. There is no big change, but some work is sometimes useless, what to do :? Never mind I don't give up :evil: I don't think that dense difference of the second wall is so important to 100 hz region (700-800 kg/m3 seems enough), if you are looking that wall like the panel trap. I think wall is acting like some various frequency panel staring from around 50hz down to 10 hz. Calculation is from 2cm panel mass around 15 kg/m2 and distance between panel and brick wall varying from few cm to 1m. Maybe I'm wrong :roll: Steve, John, where are you :D

btw. what about your phase problems? solved? greez roman

Phase is much better in the new mix position. I have to solve some HF reflections from desk, and to try with side absorbers. That will be the piece of cake compared to the finding 100 hz slice source :wink:

so you didn't stick some more insulation in the cavity behind the speakers?

sillybird wrote:

so you didn't stick some more insulation in the cavity behind the speakers?

I sticked more at rear false wall. That was slight change. I don't think that filling the soffit with 3cm MDF front baffle can change something. :wink:

This weird response really makes me nervous, so I decided to analyze my situation from scratch :? Adding symmetry at the back didn't improve much, same like more layer of rockwool :cry: . So, I disconnected my desk and moved to another room, and detached the cloud because I found that some issue is going from the ceiling. I was thinking to add some more absorption to the ceiling, but when I tried to measure without cloud I found that there is no more problems with 135hz :!: :!: :!: Midrange reverberation without cloud is noticeably longer, so there is no chance to work without. BTW, removing hangers above cloud didn't change the situation. (same like I removed them from the back of room). What's going on? Is it possible that cloud makes some kind of resonance or maybe is acting like membrane and reflecting 135hz :?: Construction is usual, studs, 10cm 50kg/m3 rockwool, fabric ... No panels . Because of dimension , weight is around 200kg. :?

maybe using multiple small clouds would be better? smaller ones spaced and angled to keep the reverbation and reflections under control and small and light enough that you can adjust them (space from ceiling, position overhead, and angles) more easily than a large single unit. because of the asymmetric ceiling it seems feasible the single large unit has differences in space and angles that account for the 135hz issue. depending on how your hangers are, er, hanging, you may be able to have the clouds match the asymmetric ceiling dimensions but still solve the reflection issue (i.e. the clouds may hang at different levels over your head, but bcause of a more consistent space to the ceiling, reflections and the absoption are correct).

Moby, Since that response is really the interaction of multiple waves phase it makes sense that changing one of the interacting sources produces a different result than you expect. You must be looking at the sum of many causes. In mid bass (100 > 200hz) situations like yours I tend to use surgical style solutions. One might be to add 1/4 wave resonant tubes above and behind the mix position to add energy of the correct phase and frequency to the mix position. I use 4" thin wall sewer PVC pipe. Cut one end square and the other at an angle (lowers Q). Put a plug in the square end (plywood circle with a foam tape seal) and tune it to your problem fz. Play the problem fz through the monitors as you move the tube around and measure the effect. An SPL meter or mic & VU in the mix position will give you a readout. Run sweeps to verify the result. By having tubes tuned slightly above and below the center fz and at different distances from the mix position you can produce a nicely diffuse mid bass sound field. Just an idea. This is cheap and fast to try. I know how frustrating it can be when you can't put your finger on a cause.

Thanks guys. In the meantime I tried to remove all rock-wool from cloud just to test how the frame is resonating. I think that really weird things are happening with this cloud filled and positioned like it is. I decided to leave clod empty just for look because there is no change compared to the situation when I remove it. So, solution with few smaller clouds will be possible... Also, I'm thinking about making some panel broadband absorbers mounted directly on the angled ceiling to fix mid freq. problems, and maybe to fill the top of the ceiling ("A" ) like some kind of bass trap.... Look at that angle makes me nervous and I'm afraid that it's acting same like any other corner :? BTW, Don, I don't know how to calculate 1/4 wave resonant tube :oops: Can you please post some formula and maybe some pic about.... Are the tubes filled with insulation or not?

Moby, Here is a quick drawing of a resonant tube and a pic of tubes mounted to the ceiling of a control room.

Don, that looks interesting :!: So, you think that it's possible to correct some issues that way. I must admit that I never saw that kind of approach, but maybe is worth of trying :wink: Thanks :!:

Moby, I have used it very successfully when many small things in the room sum together to create dips or peaks in the room response. Rather than locating and figuring how to treat each surface individually, the tubes let me sum in more energy to smooth the curve. In a small control room even the rear wall reflections can color your mix due to short times and temporal fusion. The tubes allow you to flatten and diffuse the response so even though the reflections come early they don't color your perception. Also, it helps keep the room "live" sounding. It can get involved if you also try to utilize the harmonics in the tube. Strategic location of the insulation can suppress every other harmonic, for example, due to their wavelengths. Cut the tubes longer than you calculate so you have room to fine tune & mount them. On edit: The angle cut of the tube also spreads out the harmonics. Lower Fz's see the long part and higher ones see the short. One thing to watch for, make sure the tubes have the same decay rate as the room (amount of fiberglass you put in the tube). Otherwise you will hear the tubes ring after the exciting sound has decayed. Using end plugs with a foam seal rather than a friction fit will also shorten the decay time. I don't usually install them that way because I don't want someone to change, by accident or otherwise, the tuning after I have them set. Now that I am back at PCC I will take a pic of the test tube I use in my classes for demonstration. I hope it helps,

This is really great! Thanks again :wink:

Moby, Here is that pic of my resonant tube & slide I use when testing for proper tuning.

Cool. Very detailed description. I can't miss :D

Moby, I did some more studying of your response curves. With the mix position moved forward (red trace), imagine the curve with the mid-bass between 125hz & 250 hz diffused and reduced by tube resonators. To me the response would look pretty flat. I got to thinking, it is not reasonable to think of the depth of the notch by itself because the peaks right next to it are too high as well. Moving the mix position reduced the notch by 8db and diffusing the mid-bass after it would leave deviations around 6db. Not too bad and cheap to try.

very interesting... Moby, did you tried the tubes ?

Yes I tried. It works great, but it's very sensitive to position. Its possible to make it worse if you miss. Anyway, it works, but have to be ready for few days of "hunting". :wink: