Small Basement Studio - Home Working Place

i checked again and im not in the middle of the room, im behind the middle... is this bad or better than the middle? room is 6 metres... listening position is 3.44 measured from the front wall (concrete / not soffit mount wall) i don´t know what to think about angles above 60 degrees... i´ve never seen it and i don´t really wanna try it either :) damnit im stuck here... what to do? please help me guys... THanks Andi

hansaffe wrote:

i don´t know what to think about angles above 60 degrees... i´ve never seen it and i don´t really wanna try it either :)

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damnit im stuck here... what to do? please help me guys...

We are! We are giving you solid, sound, good scientific and acoustic help. Just because you have "never seen it" doesn't mean that it is not correct.... :) - Stuart -

ok thats totally new to me :lol: thanks stuart i really appreciate your help! what about sitting more in the back of the room than in the front? my seating point is 42% from the back of the room... is this bad? if yes i will IMMEDIATELY change the design to achive the 38% :) Thanks Andi

before you do that. you need to be inside of the 60 degree cone, not at the tip. so if you're at 42% of the room length that will probably be fine. also, the massive soffit you are building, the room modes will be forced into behaving differently and the absorption behind that will temper the original modal response so the soffits response is dominant. i'd extend the slats on the first angled walls on either side to the full length. then the small angled wall totally absorptive, and then the second angled walls - wider slots but still a slat wall.

so if you're at 42% of the room length that will probably be fine.

Glenn, he's talking about 42% from the BACK wall, ie, 58% from the FRONT wall. Not so fine, I think. Andi, the other thing you could do if you don't want to change the speaker angle, is to move the speakers a bit closer together, which means reducing the size of your center panel. That will also bring the listening position closer to the front wall. And as Glenn already mentioned, you want your EARS at the 38% point of the room, NOT the apex of the triangle. Since it is your ears that actually do the hearing, they need to be at the location in the room where the modal issues are least serious, which is theoretically 38% of the room depth (and also 62%). The apex of the triangle will be at some point BEHIND your head, since the edges of the imaginary triangle should obviously go through your ears, not your eyes! So, just to repeat the geometry thing again, for clarity: Draw lines along the acoustic axes of the speakers (not the center-line of the speaker: the acoustic axis), such that the lines just touch your ears at 38% from the front wall, and intersect a bit behind your head. The point where they intersect isn't important: the point that matters is where your ears are. Once again, 38% is NOT written in stone! It's a rough guideline, a starting point. If you think about it, even moving your head a bit or sliding your chair a little bit will change you far away from the 38% mark anyway. Plus, it seems like many engineers like to be a bit closer to the front wall than 38%. So don't worry about it too much: just make sure your ears are not at 50%, or some other "bad" point in the room. And as Glenn also pointed out, with large soffits like yours (which is GOOD!) that changes the modal behavior of the room too, most likely pushing the theoretical perfect "38%" point to some other location in the room anyway. So don't sweat it too much: go for ball-park, and you'll find the actual sweet spot once the room is built. - Stuart -

guys you´re so cool... thanks alot... keep motivating me! :yahoo: but sorry for my dumbness: whats the acoustic axis of the speaker? not just the middle of it? maybe i translated it wrong and just dont get it... edit: ok i just checked again and just corrected the speaker position more to the middle but thats the most i can go i think (because the wood baffle need to be at least 3 times the half diameter of the woofer right?) if yes that would be 45 cm left and right minimum in this design... with this speaker postition my ears (not the apex of the triangle) are at ~41% i think this is good enough for me :yahoo:

but sorry for my dumbness: whats the acoustic axis of the speaker? not just the middle of it?

The acoustic axis is kind of like the center point of the expanding sphere of sound emitted by the speaker. Some manufacturers indicate where it is in their specs (check your user's manual), but most don't. It is somewhere in between the woofer and tweeter, normally much closer to the tweeter than the woofer. Imagine that you are drawing a line on the front panel of the speaker itself, joining the center of the woofer to the center of the tweeter: the acoustic axis of the speaker will most likely fall somewhere along that line, and will poke out from the speaker panel at right angles. If your speaker specs don't show where it is, then you can consider it to be the center of the tweeter and you won't be far wrong. (Some people even say to always use the center of the tweeter, and while that is close, strictly speaking it wont be exact. But we are talking a few centimeters, at most, so it's good for a rough estimate). Regarding what you did with your diagram: I was thinking more of moving the entire soffits! I mean, cut a slice off each side of the center panel in between the two soffits, and bring each of the soffits closer to the center. That way each speaker will still be centered in its soffit. You can even adjust the side walls a bit, if you want. - Stuart -

ah ok i´ll do that... what about the front panel between the soffits? can it be fully absorptive or does it have to be reflective? because i really like this angle in the design...

It can be either, but if you want to make it reflective then you'll have to figure that angle very carefully to avoid reflections bouncing off it and back to your ears. - Stuart -

does reflective have any advantages over absorbtive in this kind of soffit front? edit: by the way: i love this forum :D

does reflective have any advantages over absorbtive in this kind of soffit front?

In my personal opinion, no. I'd go with absorption: I just don't like the idea of having reflective things in front of me, and also in front of the speakers. It's really hard to figure out where those reflections are going: maybe coming back off the console or desk, or the floor, or side walls... Unless you have a ray-tracing program, it's hard to figure more than two bounces. Even one bounce is hard enough! (But I'm sure others might have differing views... :) ) - Stuart -

Hi Guys, for those of you who are still interested: dont think i´m not thankful or that i just suck up infos from this forum and then leave... i was just so busy with building and earning money that i just didn´t manage it to post regularly... AND i got a girlfriend and a dog :P i made a huge process in building the studio and i think you guys need to know whats going on... please dont blame me for my non-existing building skills and please dont blame me for having done mistakes (i´m sure) but how it is going to be when its finished is enough for my (home) needs :) plus i am very sure i broke some rules, especially when it comes to soffit mounting :) but i did a couple of measurements recently and it turned out better than expected... but see for yourself... enjoy basic framing

framing filled with rockwool for absorbtion... i had itchy pain all over my body and IN my body even days later :x

starting rear wall framing and rockwool stuffing with cavity for my diffractal diffusors whole backwall trap is 50cm deep... unfortunately i couldnt fill the corners more, because of the doors on each side... i think i had to stuff 12 packs of rockwool in this frame :shock: i also doubled checked with the diffusors if im still on the right course :D

adding melamine foam (basotect) to the side walls for raising the efficiency of the absorber and as a first trickle protection (i had a couple of mats lying around)

first positioning of speakers and measurements of the room so far

i decided to add hangers to the whole concept because i had bass problems and i wanted to get rid of it... i also had spare room beside the speaker front because i changed my original layout a bit for not sitting in the middle of the room... i´m now at 38-39% of the room front... speakers went more together so why not adding hangers... as much as the wallet allows :lol: i tried to differ the hangers in size and thickness for making them more broadband... i really didn´t know what im doing exactly because there is no science about them anywhere.... but in the end they turned out to work just perfect... i didnt take screenshots of the measurements but i can tell you i had almost 1,5 seconds decay at 50hz before and afterwards (with all hangers and backwall absorber) i had only 450 msec... i think its a great improvement :lol: by the way... all frames on the ceiling and floor are glued, no screws at all, because drilling in stell-reinforced concrete would have driven me crazy... this was easy, cheap and fast... and its so extremely stable, its crazy...

starting the speaker front

here comes the crazy part :) i put my speakers on the thick mdf plate for a vibration test just to look how the framing behaves and it was horrible... everything was shaking.... even the wall vibrated and sound transmitted to everywhere... floor, rooms above, etc... i know its a early building phase but to avoid fights with my neighbours i just decided to decouple everything a bit more :mrgreen: i did cut the mdf-board to build a tower of concrete blocks underneath the speaker-box... 400 kg of pure concrete per side placed on thick rubber that was the fastest, cheapest and easiest way to decouple the speakerbox from the room i paid 80 euros for all of the concrete plus 20 euros for the rubber mats

results were very good, nothing was vibrating, i think it was enough mass to reduce the mechanical vibrations here a little pic where i started to place the concrete (forgot to post this one before) after that i built the thick mdf-box around the speakers filled with rubber mats for a very tight fit of the speaker i then placed the mdf-box (very heavy) on top of the concrete with big sorbothane blocks underneath for even more decoupling

for those of you who think: where are the ventilation holes in the speaker box? i didn´t implement them because my speakers are driven by external three-way system fully active so i need no cooling (i checked the speakers after hours of playing at high volume, they were not getting warm at all) the crossover and the amps will be mounted in a rack in front of the whole soffit wall and will be ventilated well :wink: meanwhile i stuffed a more dense mineralwool in the backwall to prevent the fluffy stuff of falling out and to have a nicer surface for the next steps

i was stuck here... because i didnt know how to make that whole speaker box stable and tight that it doesnt move afterwards and touch the front baffle or stuff like that... but then i luckily saw these tension belts at the hardware store... they did the job perfectly... i also could use them to give the sorbothane under the box the compression it needs to work best... i chose a compression amount of 20% then i filled up the cavity of the soffit with fluffy insulation (this step totally changed the room sound - for the good :) )

then i added hangers under the soffit front... because i think: more hangers = better! :)

finally the carpenter arrived with the front baffle... it consists of 3 layers of 19mm OSB and is beech-veneered. that stuff was so accurately made that the baffle had exactly 1mm air between the wood and the speaker... no touching at all... but expensive as %&?&=$$%$ :D

i then continued the front baffle and plastered them with rockwool in picture 2 you can see the thickness of the wall