my studio- null on listening position

Hello to everyone here. I'm Davide from Italy (Verona). I have some problems in my studio, already treated. Dimension are: lenght: 4,57m - 14 ft width: 3,67 m - 12 ft height: 2,53m - 8 ft Treatment: - Frontal Angles: bass trap with 1 panel 200x100x5cm fiberform 30kg/m3 (not floor to ceiling, inside empty. But no great results filling inside with others fiberform.) - Frontal desk: bass trap two panel (up and down - sit in horizontal way) 100x200x10cm with fiberform 5cm+5cm air gap - Lateral desk : fiberform 200x100x5 (not space to wall) - Ceiling on the monitor/desk: two panel 5cm 100x200x5cm with fiberform (not space to wall) - Celing on my head : bass trap 200x100x10cm with fiberform 5cm+5cm air gap Its like a Lede project Back: - lateral sx down: Helmoltz resonator 200x100x15cm + fiberform 5cm inside+10cm air gap - lateral sx up: fiberform 200x100x5 (not space to wall) - ceiling: helmoltz resonator 180x100x15cm - lateral dx up: 100x100x5cm fiberform (not space to wall) - lateral dx down: 100x100x15 (helmoltz) - door with a 100x100x5 fiberform Back wall: - Two fiberform 200x100x5cm (not space to wall) - two diffuser - height my head - no angles bass trap Studio is fine with genelec 1030, but now I introduced more large monitors atc that have roll off as my room first mode, about 37hz Yeah, on that frequency i have a bump inside, like a rumble, but rt 60 and 30 is not so bad. Anyway with that monitors came up some problems: - very poor energy from 70 to 110 hz (still with genelec too) - a peak on 37 hz about 10/15 db Its strange, but you can hear bass power in the lower and in the higher space of the studio. In the middle, bass energy drop down. Its like a knife that cut half my studio in a horizontal way, a range about 50cm for all studio area, specifically in the listening position. I dont know if it's only a problem for ceiling or it's a back reflection... does anyone have some ideas?? I try to realize a sketch design..if it can help --conversion: http://www.csgnetwork.com/csgcvtmeters2ftincalc.html

the ceiling height 68 (1/2 = 34hz) and the length (38hz) are probably combining to produce the low end problem. you probably need a lot more back of the room absorption and even in the front. you might consider a panel trap on the front and back wall for the low end and hang an absorber in front of those. not sure what you have for a cloud but consider building one angled and using a hard backing. also, with the larger monitor, presumably you are still using the same levels? its only the extended response that is causing this?

Thanks Guilfo here a sample of the ceiling sorry for my dummy level on sketchup they are parallel to wall. nothing angled. in the front, 5cm are over my monitors and desk 10cm over my head 15cm in the back of ceiling <<you might consider a panel trap on the front and back wall for the low end and hang an absorber in front of those.>> another panel to add on the old ones? I was thinking to replace 5cm, and 10cm panel in front, lateral, ceiling, back adding 5cm of air gap and 5/6cm of mineral wool: so airgap->mineral wool->fiberform << not sure what you have for a cloud but consider building one angled and using a hard backing>> should I angle the panel over my head? what do you mean with "hard backing"? should I take away the helmoltz ones? <<also, with the larger monitor, presumably you are still using the same levels? its only the extended response that is causing this?>> For the level: still use same level, around 80 db spl. With roomeq I see room response is about the same at 75/78db. Changes are only in the low end: genelec have less energy down to 50hz Others: Genelec is placed high at 1m and 14cm, and there I heard more powerful bass than the larger atc, that are placed with the woofer 70/80cm less or more from the floor. I bought some sonotubes to do some tubetraps to fill completely with mineral wool. 35cm and 30cm..but I dont know if this can help. Cause If I add some absorber, before to work on the 40 hz, they also drop down the energy around 70-110hz...

i'm suggesting membrane panel absorbers targeting the very LF as the resonators cannot treat that low. on the cloud, using a 3/4" (19mm) MDF backing on 4" (100mm) absorption.

Thanks gullfo <<you might consider a panel trap on the front and back wall for the low end and hang an absorber in front of those.>> So: absorption(5cm) +MDF(2cm)+absorption (10cm) ? so your advise is covering frontal panel and back ones with a MDF panel?, On the cloud will I cover with MDF+ 100mm of mineral/fiberform . No air gap? p.s but don't membrane panels work better only for large rooms? any kind of room?

the membrane panel absorber would typically use 1/8" (2.5mm) or 1/4" (5mm) panels (plywood is generally a good choice) because you want th panel to vibrate, then the sealed cavity and insulation inside dampen the panel vibration. on the cloud, make a 3/4" (19mm) panel then line the face of it with cloth covered porous absorption - 4" (100mm) thick rigid insulation. then hang on a angle (say 15°, more if possible if possible) over the mix desk.

thanks gullfo so I need more density panel to absorb around 40hz...something like 30-40kg/m2 .. for 19mm?

HI, Its late and tonight I'm not able to add any intuitive statements to your discussion anymore, but i can add some pictures. Maybe it helps. Most important all your modes: And as a function over frequency - the space between adjacent modes and for the sake of completeness: In the 'floor' tab of this applet you could theoretically move your listing and subwoofer positions. But I have not finished/tested this feature yet, so I don't know the accuracy. best regards Andy

on the cloud the backing helps to disrupt the modal response between the floor and ceiling.

thanks a lot both! gullfo: do you think a panel 180cmx100cmx1,9cm (5ft+10.86inch x 3ft+3.37inch x 0ft+7.4inch) is good enough? or maybe more / less?

Can you post a picture of it?? "Its like a Lede project" maybe there's the problem ;)

I'll try to post as soon as possible. Thanks Gullfo, thanks John. as "lede", cause it's dead in the front part for room (monitor, desk and listening place) and in the back there are some helmoltz (2x ceilings, 2x lateral down) and some panel (lateral and back) but also a 2x QRD diffusors What do you think John?

no wall angled or others, walls are parallel to each other

just as a curious idea, what if you turned your desk to face the back of the room and position your seat @ 38% from that back wall? "live end" now in front, and "dead end" now in back.

Hello. sorry for late. @gullfo: I have some problems to turn the listening place in studio. I can do that when the new desk will be in. @john: here some pictures. sorry for "messy"..I'm doing some works... what do you think?

the front end absorbers don't seem nearly thick enough. the clouds overhead - same issue. you need to get at least 4" thick absorbers all round in the small a space. also, lifting the front of the desk 4-5" (100-125mm) to tip it will help with the reflections off the table.

thks the desk will be replaced with a better acoustic one, as sterling modular style..so comb filtering every 1 khz will be resolved. My doubt is about how resolv the combination modes that cut bass at middle height room. I think those next step: - reinforce dead space with double panels (mineral wool+fiberform, about 10 cm) - check what i have - do angles membrane panels. Is the real problem over my head? so do i need to resolve before the ceiling?

the clouds need to be bigger and thicker and hang them down from the ceiling on angles (say 15 degrees) so you maximize their absorption. if necessary, use plywood or MDF on the back of the clouds. skip membrane panels until you know the other absorption tactics aren't solving everything. you want broadband control to flatten the room response so you're not just selectively trying to treat problems you have not identified yet...

Hello again I did something.. I try to change the position of monitors from dead space to live space, but no great result. Also I try to make an angled ceiling over my head (listening position) with 5cm fiberform 30kg/m3+fiberform 40kg/m3+ fiberform 30kgm3 (something less than 2 m x 1m) with no result at all I understand that 66hz vertical mode does a null at listening position and two strong resonance at the top and at the bottom for all room. I understand that 132 hz does two null at the top and at the bottom and a strong resonance at listening position. I try to put some 60cmx60cm fiberform (30+40kg/m3) over my head like clouds, with no symmetry and this makes region 110-130 hz more flat.. I havent tried yet with membrane panel... Still have 37hz modal peak, and a drop down at 60hz to 100hz (deep at 74) Still I try with membrane panels?

I try to make more fat my angle trap and add more absorber on backwall and the result is that I still have a peak on 37hz but now I have a peak also on 74 hz , cause null now is more narrow down to 100-110hz before I have a null on 74hz... what could be? Should I have turned the phase of first or second axial mode?