slow progress again. now I managed to make my final measurements before building.
so this will be my baseline and hopefully I get better results later:)
Green line is measurement taken inside.
Blue line is SUM of measurements taken outside.
once I had taken my first measurement(green line) I moved microphone to outside and measured all 4 walls, mic 1m from wall.
Biggest sound leaks came from window and air conduit and on the side sound leak measured a lot lower.
there was birds chirping and flying around and all normal noises from the neighborhood that messed up the measurement in the kHz range,
but now I have atleast something to compare.
another garage conversion
Originally posted at johnlsayers.com, topic 22175.
wanted to share my progress but first sorry to see these sad news about mr.Sayers!
glad to see that the future of this forum is good hands.
I now have empty room (inner measurents 4.1m x2.9m)
sidewalls are made from 10mm OSB+13mm gypsym
frontwall 13mm gypsum (and will add a layer of OSB)
ceiling 13mm gypsum
backwall 2x13mm gypsum.
attached picture or the room and sound leakage test
generally I'm guite happy with the isolation i got,
but empty room sounds the even worse than I did expect :oops:
In measurements I noticed this ~10dB difference at ~95hz and that is buzzling me:
mic was 1.61m (39% of room lenght) from front wall, ear hight (120cm)
used one genelec 8020 placed symmetrically with lasers and tape measure as I could first L then R position.
is this something that comes from difference in walls (right wall is "damped" by old existing wall while left wall is facing center of garage)?
and is this something that should be adressed ie.making stiffer walls or parts of the existing walls stiffer etc?
or can few mm difference in speaker placement couse measurement error in this low frequency?
or is this something so minor that it can be ignored?
maybe move the listening mic a bit to see how stable that 95hz is. it may be a mode function based on the room width. or room height. moving back and forth, side to side over (say) a 1m circle should tell you.
I did actually have an measurement, where mic was closer
and in that one the difference L/R is lot smaller!
Also attached is picture of difference of two mic postions.
Attached measurements of left speaker,
Mic moved to different distances from front wall
So is this ~90hz room mode?
I remember reading topic about graph that acted like this with mic movement but cant find it now..
note how the curve has flattened on one position. the peaks can be turned down via EQ.
Yes I was wondering that! Closer the front wall I move the flatter it gets :D I can eq that with glm when I bring my main speakers. So how does the situation change if I soffit my speakers? Front wall will move(or part of it?) and it changes the situation(?) Btw.should I also do "empty room" measurements with my big speakers or it doesn matter?note how the curve has flattened on one position. the peaks can be turned down via EQ.
the soffits will cause a change in the LF response because (if done correctly) the baffle step will eliminate the "wrap-around" of LF and form a single wave front. you then compensate this (hence baffle step correction) typically reducing the LF by around 6db. of course tuning the response would be easier with a parametric-type crossover on the speaker system.
I'm now puzzled by soffits or speaker location:
If I understand this correctly, soffit wall should be very sturdy->does this mean that my rooms "shell" will be altered?
ie.middle section of my front wall will now be (~0.5meters/depth of soffit) closer to my listening postition.
is there a way to predict is there going to be (big) change in my graphs in low frequencies purely caused by this new wall?
I guess this boils down to knowing should I also take measurements where speakers are moved to different positions ie.if I do soffit
I would put speakers close to the space they would be when soffitted or if I take easier route and use speakers on stands I would place speakers away from the wall.
last measurement was made by setting speakers as close as I could get them of front wall, 55% of the room width apart.
the soffit approach eliminates the issues that free standing monitors have - mainly SBIR. however, they're more complex to design and build. they need to be rigid and ideally decoupled from the surrounding walls, floors, and ceiling. angled to maximize the listening position and sealed but vented to ensure heat off the speakers are released.
yes I've been trying to study them and I realize how hard they are to make correctly, let alone some of those fancy tensioning etc Ive seen in Nortwards designs. I quess that again after some thinking, main reason for soffits in my case would be that I could use this small space more efficiently ie. if I make superchunks in corners, my floor standing speakers would have to be moved back from front wall and that would shift the whole room back while with soffits my speakers could stay more back. I know it would be stupid reason to soffit speakers, but since this is quite small space, I have to compromise between good sounding room vs.room that has no space. But again if I want to make proper and good soffit, I know that I will spend this coming year asking questions and designing stuff..while without soffits I think designing and building would be MUCH faster. I think it's quite hard to find good reference designs in this(or other) forums that are designed without soffiting speakers.the soffit approach eliminates the issues that free standing monitors have - mainly SBIR. however, they're more complex to design and build. they need to be rigid and ideally decoupled from the surrounding walls, floors, and ceiling. angled to maximize the listening position and sealed but vented to ensure heat off the speakers are released.
did you ever post the room dimensions? i'm looking through the thread and only see the initial raw space dimensions.
Yes sorry! Measurements are: Height:230cm Lenght:413cm Width: 288.5cm (inside-out walls measured from widest place)did you ever post the room dimensions? i'm looking through the thread and only see the initial raw space dimensions.
so you could do soffits fairly easily in this size room. you'd need to route out a bezel to fit the edges of the speakers but that can work. something like this:
thank you Glenn and those renderings look really good! I guess next question is would "semi proper" soffit installation be better than leave speakers on floor stands? if I open this question up a bit: if I would start building now, I would make 2x4 frames, shelf for the speakers, build some sort of mdf box where to place my speaker(maybe copy attached official flush mount kit) where speakers are standing on isopods, with no sylomer etc on below/back/sides of speaker(?) leaving space for heat/air to circulate, then couple of layers something heavy sheets for frontpanel. I know that I would really need to also make sure that speaker would be floating behind front panel (standing on some stand/not touching soffit "face"), this is something that is still unclear to me and would require a lot reading. +then there is also this;so you could do soffits fairly easily in this size room. you'd need to route out a bezel to fit the edges of the speakers but that can work. something like this:
https://support.genelec.com/hc/en-us/ar ... nstructed- but I think they are referring to wall materials more than framing, but still I wouldnt want to make concrete wall for these :shock: I wish there would be some light-version of soffit:) one option is to build rest of the room and use it while searching for more info..and when I feel ready add soffits.Wooden walls are not recommended as these are typically not lossy and stiff enough and the unit mass of a wooden wall remains rather low.
properly designed, wood frame based soffits are workable. its a matter of getting the framing to be stiff enough along with layers of dense panels. and decoupled speakers/boxes to reduce any structural transfers. less hard in practice than over-thinking it :-)
you could go with free standing and front walls absorption and see how it works for you. then as you become accustomed to the room and you find the remaining SBIR effects (and etc) are problematic, then you can build out the soffit approach.
Thanks Glenn! I might actually have a bit bad habit of sometimes overthinking :D I think that could be the way to go in my case!properly designed, wood frame based soffits are workable. its a matter of getting the framing to be stiff enough along with layers of dense panels. and decoupled speakers/boxes to reduce any structural transfers. less hard in practice than over-thinking it :-) you could go with free standing and front walls absorption and see how it works for you. then as you become accustomed to the room and you find the remaining SBIR effects (and etc) are problematic, then you can build out the soffit approach.
While surffing around, I bumped into this attached picture
Where genelec 8260 seem to be installed in soffit without bafles. And this place was designed by well known local studio designer.
Is there any up/downsides in this sort of installation?
I would basically surround my speakers bass traps and not waste space..
after googling these came up: viewtopic.php?f=2&t=19672 https://gearspace.com/board/studio-buil ... offit.html https://gearspace.com/board/studio-buil ... ption.html http://arqen.com/acoustics-101/speaker- ... erference/ tldr: it can be good or bad :DIs there any up/downsides in this sort of installation?
so maybe this is something I can try later on. I quess next question that I'm strugling with is optimal thickness for my front wall (porous) absorber and distance of speakers from front wall (real wall, not the absorber "wall".) By making thicker front wall(absorber) I can make it more effective on low fq BUT I then have to move my speakers away from front wall to not so optimal place."The fourth cure is to make the wall so absorptive that the reflected energy becomes negligible and hence does not cancel any of the direct sound. The thickness of a porous absorber has to be one quarter of the wavelength of the frequency to be absorbed to become effective. This is the same distance that determines the frequency of the cancellation dip and therefore the absorber has to be very thick. Usually, the required absorbing thickness is so high that such solution is practically not implemented."
sketching some ideas just to see how much space I would need,
if my whole front wall is porous absorber it doenst matter if it has angles or not?
I know its stupid to draw conclusions just on pictures of studio without knowing whats under the surfface,
but I've seen some pictures where front walls are angled and full of absorption.. I understand if you use slats etc but I dont get what other reasons there is?
(other than looks or maybe saving some materials etc)
and most LEDE/RFZ have reflective front wall?
generally speaking it's useful to have some hard surfaces rather than purely soft. but since you have inside-out walls (and assume you did similar to ceiling) then you can try things out and expand the treatments as / if needed. so when building out, some treatments should be angled to get the support for the audio level balance, and still reduce/eliminate reflections.
Thanks, exellent points once again! Actual my ceiling and front wall are normal and rest of the walls are inside-out. If I want to think about angles: Most topics about front wall angles talk about soffits, I guess those "rules" are good for my situation too? And some ray-tracing tools could be used in this case also? Originally when I started planning this whole build, I thought that I would fill walls with oc703-ish insulation and bass traps front and back..but I now understand that one wouldnt want to make your room too dry.generally speaking it's useful to have some hard surfaces rather than purely soft. but since you have inside-out walls (and assume you did similar to ceiling) then you can try things out and expand the treatments as / if needed. so when building out, some treatments should be angled to get the support for the audio level balance, and still reduce/eliminate reflections.