Null Problem

Hello Folks... I´m new here and have a big prob... I´m trying to build a pro-sounding control room in my home. The Room is 5.4 meters length x 3.6 mts with x 3.2 meters high with a 45° Angle on the front wall (sorry for the bad english, but i think you know what i´m talking bought... :-). Pleas look at the pics... The walls are 12,5 cm Thick Brickwalls and the angled wall is 25 cm Polystyrene plus Roof-construct, the ceiling is 4cm Wood plus 15cm Polystyrene insulation above it. So i bought good monitors, bouht a room acoustics book and ordered Absorbers and Resonance-Bass Traps for about 3000,- Bucks. My Problem is, that, the Genelecs on the Table sound kinda good (i´m sitting wether in a null nor a peak... kinda balanced), but, whatever i do with the position of the K&H 0300 (in the selfmade stands) and my own listening position, i do hear nearly no bass... Bigtime Null problem... I thought the Resonance Basstraps will fix that... but they didn´t... Then i stuffed 8 Boxes with Rockwool and placed them behind the stands in the corners (as seen in the pics), with (nearly) no result... It got better (but only a bit)... What do i do wrong? This null drives me cracy... The more i go backwards with my head, the stronger the null becomes... Maybe someone has an idea of what´s goin wrong.. thanks Manfred

Here are some pics just to give you an idea of what i´m talking about...

Hi, and please read the "sticky" posts on the first page of this forum, with the rules about posting. You probably won't get any replies if you do not follow those rules. Regarding your problem: First, to me it looks like you don't have anywhere near enough bass trapping for a room that size. I'm not sure what you mean by "resonance bass traps" (that could be a number of things), but I'd suggest you they aren't doing very much at all: I'd say replace those with proper "superchunk" bass traps in both of those rear corners, plus another one across the top of that rear wall (the ceiling-wall corner), then also in front of your desk in the floor-wall corner, plus up as high as you can get across those front corners behind the speakers, and as many other corners as you can possibly do. Second, did you actually measure the room response at your mix position? Where exactly are the nulls? (what frequencies and how deep). With those dimensions I'd expect issues at the following frequencies: 31.9, 47.8, 57.5, 63.8, 79.7, a big one at 95.7 (0:2:0 and 3:0:0 both line up there, exactly), 100.8, 107, 115, 127, and that's just up to 130 Hz. Some of those will be nulls, some will be peaks. But that's just theoretical: You'll have to actually measure the room to find out where your problems are, then you can figure out how to fix them. Third: What are the "resonant bass traps", what frequency are they tuned to, and what is their Q? Are they the red things in the corners, or the black things on the floor? Do you have specifications for them, or maybe a link to the manufacturers web site? US$ 3,000 for those seems a bit steep... Anyway, they may well be tuned to entirely the wrong frequency, so they might even be making matters worse. What exactly are they, and what principle do they work on? Fourth: Where is the mix position (position of your head)? In terms of how far from the front wall, how far from the back wall, and how high above the floor. - Stuart -

Hy Soundman2020... The Black boxes on the floor of the Rear Wall are Membrane-Resonance Absorbers tuned to 30-90 Hertz. http://www.mbakustik.de/main.php?target ... 478f953b93 They are called RAB650. Replacing the RAB´s is no option, because i just payed over 900,- bucks for them... The Red ones and the Big Black one over the listening Position are Broadband absorbers from the same manufacturer. BAB150 and the Black one BAB100. http://www.mbakustik.de/main.php?target ... ndabsorber In the front corners are the 8 boxes filled with rockwool, which are 80 cm´s in depth... I think i will continue with buying more rockwool and place it on the back wall/corners with some kind of enclosure...

Oh, and the listening position is 2,9 m´s from the front wall, 2,3 m´s from the back wall and in 1,25 m´s height.

Soundman2020 wrote:

Hi, and please read the "sticky" posts on the first page of this forum, with the rules about posting. You probably won't get any replies if you do not follow those rules. Regarding your problem: First, to me it looks like you don't have anywhere near enough bass trapping for a room that size. I'm not sure what you mean by "resonance bass traps" (that could be a number of things), but I'd suggest you they aren't doing very much at all: I'd say replace those with proper "superchunk" bass traps in both of those rear corners, plus another one across the top of that rear wall (the ceiling-wall corner), then also in front of your desk in the floor-wall corner, plus up as high as you can get across those front corners behind the speakers, and as many other corners as you can possibly do. Second, did you actually measure the room response at your mix position? Where exactly are the nulls? (what frequencies and how deep). With those dimensions I'd expect issues at the following frequencies: 31.9, 47.8, 57.5, 63.8, 79.7, a big one at 95.7 (0:2:0 and 3:0:0 both line up there, exactly), 100.8, 107, 115, 127, and that's just up to 130 Hz. Some of those will be nulls, some will be peaks. But that's just theoretical: You'll have to actually measure the room to find out where your problems are, then you can figure out how to fix them. Third: What are the "resonant bass traps", what frequency are they tuned to, and what is their Q? Are they the red things in the corners, or the black things on the floor? Do you have specifications for them, or maybe a link to the manufacturers web site? US$ 3,000 for those seems a bit steep... Anyway, they may well be tuned to entirely the wrong frequency, so they might even be making matters worse. What exactly are they, and what principle do they work on? Fourth: Where is the mix position (position of your head)? In terms of how far from the front wall, how far from the back wall, and how high above the floor. - Stuart -

Thanks Stuart! This was very helpful to me! I was thinking I needed superchunk bass traps as well since my mixing area is small as well! Thanks!!