have you tried 4" thick 3pcf or 6pcf rigid fiberglass across the corner? a properly sealed poly floor to ceiling? something to trap a lot of air and acts on the velocity and/or pressure on the corners. the lenrds seem too small to do the job. a superchunk absorber is a stack of 703 (or equiv) insulation in the corner with at least a 24" face.
keep in mind that modes permeate the room - treating just one corner isn't typically going to show all the response shift that 2 corners will. and 2 won't be the same as 4... low frequencies are big wavelengths and they tend to interact across the entire room.
timogiodeson MEASUREMENTS THREADS! Tracking Room Acoustic
Originally posted at johnlsayers.com, topic 9383.
Thank you Glenn, No, I never tried 3pcf or 6 pcf or a sealed poly, only foam, 8 pcf and 2.5pcf. and R insulation. The big poly made by a curved 4x8 1/4 plywood lined with insulation sound very affordable ... and the pressure things should work better than a velocity porous absorber for the modes we are dealing with correct? From your personal experiences, the corner Poly, will work better than the velocity absorber I measured in the picture below? I can even fill the cavity of this think with low density R insulation eventually... I noticed in my measurements that below 100hz a 4' wide absorber in one corner only , works better than 4 corners treated in the traditional way... In my measurements I noticed that 4 feet wide across corners improve absorption below 100hz do you noticed? Can you please take a look to the "one corner measurements in page 3" please? of course I will treat all 4 corners... but, If the poly works better or about the same , I will prefer it because it's much more affordable... P.S. My only concern with slats and poly's is that their reflective surfaces toward the room, will be 5 inc or more closer to the mics and musicians than a regular wall that reflect highs between porous absorbers... see for example a big corner poly.. it will take about 3 feet of space in each corner etc... this will reduce even more the dimensions of the room after all... the H. F. reverberation time? maybe the room will sound smaller at the end ? Any thoughts on this?have you tried 4" thick 3pcf or 6pcf rigid fiberglass across the corner? a properly sealed poly floor to ceiling? something to trap a lot of air and acts on the velocity and/or pressure on the corners. the lenrds seem too small to do the job. a superchunk absorber is a stack of 703 (or equiv) insulation in the corner with at least a 24" face.
the poly is not as efficient as the heavy rigid fiberglass for a broad band absorption, but it does adds diffusion and trapping in one unit - at the cost of extra space. and it does introduce the possibility of reflections if the mics are close (but walls will be problematic as well).
if you feel more comfortable that the corner absorption with the fiberglass will reduce the need to additional panels in getting the reverberation under control, then go with that approach. if keeping the room more alive is important and you plan on adjusting the space using smaller absorption panels, then the polys would do it (assuming the space consumption is ok).
a live diffusive room will not sound small but a small room will sound small without mode control and balanced reverberation. in the case of your room - get the bass trapping up. then adjust the reverberation until you feel its balanced. there is a limit to what measuring a single corner will give you.
Glenn thank you, OK about the single corner things... So...In your opinion will be enough if I treat all the 4 corners like in the example below with 2 regular 2x4 4" tick 8 pounds absorbers with Lenrds behind ? What is your opinion? Please look at the measurement below where all 4 corners are treated in this way . Please let me know your opinion about the measurement because If it's not enough I think I have a better idea and also enough material.....and I will show you later.. "note that the mic and sub position in this measurements was not one of the worst as far of showing big deep and nulls..also I had to move the sub woofer slight away from the corner to make space for the absorbers because it was the first time I had all 4 corners treated." also please note " Jeff suggested to listen to my hear , I do also listen to my hear, but, it's not easy to understand, and between experiments and measurements can be confusing especially for bass freq... Also the walls treatment effect how I perceive the bass at the end for example with more high freq I hear less booming bass etc .. So for the low modes , It's not better to look at the measurements instead?...and maybe listening the bass drum... Another point: If the room, after treating a couple walls, sound better to my hear, doesn't mean that it sound good, eventually I don't even know how the room should sound jet.!. there is a limit to what measuring a single corner will give you.
Hi Gab,
you can see where the response is tightening by almost 10db in some cases, but you can also see that between 100hz and 200hz you're getting a lot of absorption. overall its flatter and peaks like 30hz could be an EQ cut. how does the bass sound (subjectively)? it may be that if you add some additional 2-4" absorber panels 2-4" off the walls to tame the high end you'll find some more of the low modes go away but the really low stuff below 100hz may need a panel (membrane) trap to address if you find the modes annoying.
thanks for explaining Glenn. Yes I guess the modes are annoying, Before building the panel traps I would like to try one more things.. (4) Mega Lenrd floor to ceiling in one corner, (4) 8 pound 4" absorbers 4' wide floor to ceiling in two of the corners, And something else on the fourth corner will see ... I will try this today, I will measure and see if this will flatten , If not, I will build the big poly or the panel traps you sugested for the freq below 100 hz.. I will post the results later tonight regards thanks againHi Gab, you can see where the response is tightening by almost 10db in some cases, but you can also see that between 100hz and 200hz you're getting a lot of absorption. overall its flatter and peaks like 30hz could be an EQ cut. how does the bass sound (subjectively)? it may be that if you add some additional 2-4" absorber panels 2-4" off the walls to tame the high end you'll find some more of the low modes go away but the really low stuff below 100hz may need a panel (membrane) trap to address if you find the modes annoying.
Gab,
I wasn't aware you had MegaLENRDS - I must've missed that.
Those should be easy enough to try in the wall/floor corners, in addition to the LENRD/Mineral Fiber wall/wall corners. Doable?
Hi Jeff, I don't have mega lenrds, but I make the same size absorber with 4 Lenrds together ... I can make a wider megalenrd too if I need , see the pictures below P.S. I have 20 Lenrds total so I can make 5 mega lenrds, or 4 mega Lenrds plus 4 Lenrds, or mega lenrds made with only 3 lenrds etc Also a good 8" tick broadband absorbers for the walls can be made with 4 layers of 2" studio foam ... I have all this foam already, some how I need to use it !Gab, I wasn't aware you had MegaLENRDS - I must've missed that. Those should be easy enough to try in the wall/floor corners, in addition to the LENRD/Mineral Fiber wall/wall corners. Doable?
OK Glenn and also Jeff, thanks for helping me out with this, I think everything is clear for me now.
1) I can clearly hear during the sweep, big nulls and picks and problems. starting at about 20hz with a vibration of the walls...then from 30hz up to about 150hz I can clearly hear the sound level going up and down several times . Above 150 Hz everything sound more even.
2) With a deep bass drum with Evans emad drum head I can definitely hear this booming loud pressure, not sure about the frequency but sound very similar to the 20-40hz sweep I guess..
3) I made this new measurements today, the measurement mic now is unluckily on the upright bass position near the right corner of the room. You can clearly see on the measurements the problem from 30Hz to about 130hz..I see that 70hz is about 60 db louder than 130hz!
I made 3 last measurements
(note that now there is several diffusers in the room walls and ceiling,)
I'm measuring only to see what kind or how many low F. absorbers I need (low frequencies below 150 Hz)
I can tell you by hear playing the bass drum that 4 lenrd in each corner floor to ceiling don't do enough, 8 pound absorbers 4 inc tick in front of the lenrds floor to ceiling improve a lot, and 4 feet wide 4 inc tick absorbers and Mega Lenrds floor to ceiling improve even more!
With the last approach the grand piano sound finally good across all the frequencies especially in the middle where the problem was...
Also the snare and bass drum sound more tight with better intelligibility,
however, the cymbals tend to sound dry, (this is not really terrible but it sound like if the cymbals are inside a drum both and the drums in a larger room..) Also, a 4' wide absorbers take really to much space in my room...I hope there is another way to go...I don't have space for this.
I don't know how much dry or live I like the room jet ....but as long as the drums and cymbals and piano sound like in the same room, everything will be OK. :)
Eventually a very dry room can be OK too if everything is balanced...
Right now, I can think of only this options:
1) floor to ceiling lenrds behind 8 pound 2x4 absorbers in all corners ( a la Jeff) , and eventually more in the ceiling corners ?
or
2) Start with absorbers that works only 150hz and below and then add any of the material I have to tune the room, a broadband absorber tuned to absorb only and everything below 150hz ...can be done?
or
3) many small 2x2 or smaller, very thick 6 inc and up porous absorbers and deep small corner traps made with foam, insulation, mineral wools etc Spread all over the room alternating with 2x2 or smaller diffusers leaving some space between each panels for a more open sound.
however I think option 2 will be a more versatile approach without risks of over absorbing highs..
measurements:
(note that now there is several diffusers in the room walls and ceiling,) I'm measuring only to experiment with the Porous L.F. absorbers I have.
1) 4 Lenrds bass traps in each corner, floor to ceiling, (16 lenrds)
1/3 octave smoothing and regular view.
2) Additional 4 inc tick 8 pound 2x4 absorbers in front o the Lenrds floor to ceiling , (16 lenrds plus 8 2x4x4" absorbers in the room)
1/3 octave smoothing and regular wiew.
3) 4' wide 4" tick , 8 and 2.5 pound absorbers plus mega lenrds floor to ceiling ( 5 mega lenrds, 2 -4x8x4" absorbers, 1 4x6x4" absorber)
1/3 octave smoothing and regular wiew.
here the same 3 measurements all togheter, 1/3 octave smoothing and regular
black = lenrds only
blue = lenrds behind 8 pound absorbers
red= large 4 feet wide absorbers
Gabriel, thanks for the pictures, measurements, and listening reports. Interesting.
Are the wall made of one single sheet of plasterboard ? If think my design would improve also the ringing walls problem, but of course the heavy guys approach would be to affix a second layer of plasterboard with Green Glue or mass loaded vinyl in between.
If you want to stick with material you already have you should try corner absorption between the walls and the ceiling. As an experiment you can try between the walls and the floor. This should improve even more the TR in the low-mid/bass register. If you're happy with it, you then have to find a way to set the panels between the ceiling and the walls. Then, to counterbalance this added absorption in the room, so you should probably keep diffusion on the walls.
Concerning the cymbal problem you should probably go for a BIG diffuser above the drums.
thanks misikio From studs to inside the room: Walls: Studs -5/8 screwed drywall - 5/8 glued ceiling tile - 5/8 glued drywall -paint. Ceiling: Studs- 5/8 screwed drywall - 5/8 glued ceiling tile- 5/8 glued ceiling tiles- paint. I need an absorber that works broadband from about 20hz to about 150hz, without absorption above 150hz. then I guess above 150 Hz will be relatively easy to tune the room with the porous absorbers I have by hear... let's see what Jeff and Glenn suggest, I can be wrong... I hope for some input from John and Kendale too.. P.S. Sorry Jerry I tough your name was Aloha... :) Happy Thanks Giving!thanks for the pictures, measurements, and listening reports. Interesting. Are the wall made of one single sheet of plasterboard ? If think my design would improve also the ringing walls problem, but of course the heavy guys approach would be to affix a second layer of plasterboard with Green Glue or mass loaded vinyl in between. If you want to stick with material you already have you should try corner absorption between the walls and the ceiling. As an experiment you can try between the walls and the floor. This should improve even more the TR in the low-mid/bass register. If you're happy with it, you then have to find a way to set the panels between the ceiling and the walls. Then, to counterbalance this added absorption in the room, so you should probably keep diffusion on the walls. Concerning the cymbal problem you should probably go for a BIG diffuser above the drums.
Gab,
I'm a little confused. It would appear from the above statements that you are happy with the bass drum and piano sound. Why do you think you need more treatment at 150 Hz, specifically? As for the dryness of the cymbals and diffusion, I concur with msikio.With the last approach the grand piano sound finally good across all the frequencies especially in the middle where the problem was... Also the snare and bass drum sound more tight with better intelligibility, however, the cymbals tend to sound dry, (this is not really terrible but it sound like if the cymbals are inside a drum both and the drums in a larger room..) Also, a 4' wide absorbers take really to much space in my room...I hope there is another way to go...I don't have space for this. I don't know how much dry or live I like the room jet ....but as long as the drums and cymbals and piano sound like in the same room, everything will be OK. :) Eventually a very dry room can be OK too if everything is balanced... Right now, I can think of only this options:...
Thanks Jeff, No, I don't need treatment at 150hz specifically, I said that ? :o My last experiment was about using very large 8 pound and 2.5 pound 4'x8'x4" absorbers across the corners and also Mega Lenrds floor to ceiling in one corner and one more Mega in one tri-corner. This last approach improved the piano considerably...and also snare and bass drum intelligibility, however it is an experiment, this 4x8 mineral wool absorbers are really too big for my room. I need the space, the MegaLenrd size is acceptable, but also introduced high frequency absorption, and now that I'm thinking... you said:... I'm a little confused. It would appear from the above statements that you are happy with the bass drum and piano sound. Why do you think you need more treatment at 150 Hz, specifically? As for the dryness of the cymbals and diffusion, I concur with msikio.
Can be the cymbals things correlated with this? There is 5 mega lenrds in the room in addition of the two 4x8 and one 4x6 corners absorbers and ceiling tiles... about the 150hz things... here my two previous messages:"Foam tends to shave off more of the very high frequencies (> 6-8 kHz), making the room relatively "darker."
also :I need an absorber that works broadband from about 20hz to about 150hz, without absorption above 150hz. then I guess above 150 Hz will be relatively easy to tune the room with the porous absorbers I have ...
To be honest, I don't know jet how dry or how live I like the room, it can be variable too eventually.. as long as the decay time sound uniform across all frequencies it will be OK, perhaps, without this booming things 30hz to 130hz... the room can sound OK just the way it is only with diffusers and ceiling tile I guess! A very live one then... this are my impressions, but I can be wrong .... don't trust me to much :?OK Glenn and also Jeff, thanks for helping me out with this, I think everything is clear for me now. 1) I can clearly hear during the sweep, big nulls and picks and problems. starting at about 20hz with a vibration of the walls...then from 30hz up to about 150hz I can clearly hear the sound level going up and down several times . Above 150 Hz everything sound more even. 2) With a deep bass drum with Evans emad drum head I can definitely hear this booming loud pressure, not sure about the frequency but sound very similar to the 20-40hz sweep I guess.. 3) I made this new measurements today, the measurement mic now is unluckily on the upright bass position near the right corner of the room. You can clearly see on the measurements the problem from 30Hz to about 130hz..I see that 70hz is about 60 db louder than 130hz! .
if the corner traps are too absorbant, you could try to put something like a diffuser over it to reflect the sound back into the space and still provide low end absorption. the problem with bass trapping is it does take space not matter what you do... a simple frame of 2x4s arranged (ie cut) to make a prime 11 array (http://www.mhsoft.nl/diffusor.asp#calcul) with gaps. not a perfect QRD by any means but better than simply having a flat panel.
thanks Glenn , 4 feet wide 4" tick, 8 pounds, 4x6 or floor to ceiling across corners works much better than the other options I experimented here...I can hear the difference. but below 130hz I need something more Can a corner Helmholtz, Poly, panel traps, hanging panel etc. be broadband from about 30hz to 130hz? I need something that works at very low freq. to use in conjunction with this large absorbers across the corners.. the big 4x6, 8 pound absorber centered across the corners ( with some air on top and bottom) sound good... I can already hear the difference with only two of this panels P.S. About the measurements below... Something is wrong with Lenrds in the corners, there is about 50 db in difference between 30hz or 40hz or 70hz and 125hz. 16 Lenrds did nothing helpful ! Axially the measurement look worst .. ...there is a scientific explanation for this? I don't understand... :shock: I spent over $700 only for the Lenrds last year this is very depressing . I will post extra measurements later. The second graphic is the same measurement but with 1/3 octave smoothingif the corner traps are too absorbent, you could try to put something like a diffuser over it to reflect the sound back into the space and still provide low end absorption. the problem with bass trapping is it does take space not matter what you do... a simple frame of 2x4s arranged (ie cut) to make a prime 11 array (http://www.mhsoft.nl/diffusor.asp#calcul) with gaps. not a perfect QRD by any means but better than simply having a flat panel.
for lows - 30-100hz - use a panel trap. its flatter and you can build a pair on a corner. check Ethan Winer's site for details on bass trapping using panel traps. http://www.ethanwiner.com/basstrap.html
as for LENRD vs fiberglass http://forum.studiotips.com/viewtopic.php?t=536 properly done the fiberglass is pretty close in performance and also has a bit more high end absorption.
thanks Glenn, the link you send me it shows MEGA LENRDS compared with SUPER CHUNKS and CORNER ABSORBERS. There is no regular size LENRDS data on the examples... I can confirm to you that in my room: 1) Regular size Lenrds standalone without studio foam in the walls are useless 2) (A la Jeff) Lenrds floor to ceiling behind 4" tick 8 pound 2 feet wide absorber floor to ceiling works just like Mega Lenrds. 3) 4x6 , 4inc tick 8 pound absorber centered across the corners works much better than Mega Lenrds floor to ceiling. In my room it's all about the size, I can confirm that a 4 feet wide absorber across the corners floor to ceiling (or just 6 feet tall centered which I prefer because it give a little more air to the sound) works better and lower than all the other methods I experimented with including Mega Lenrds floor to ceiling. I can definitely add the panel traps you suggested behind the 4 feet wide absorbers, there is room! But approx how many panel traps I will need for the 30hz and other modes below 100hz?for lows - 30-100hz - use a panel trap. its flatter and you can build a pair on a corner. check Ethan Winer's site for details on bass trapping using panel traps. http://www.ethanwiner.com/basstrap.html as for LENRD vs fiberglass http://forum.studiotips.com/viewtopic.php?t=536 properly done the fiberglass is pretty close in performance and also has a bit more high end absorption.
Ethan has recommend a pair in each corner in other threads. maybe do 2 corners with 30hz and two corners with 100hz. another option is to build the panels on the axial mode points - length width or height - although corners have all modes.
Ethan has recommend a pair in each corner in other threads. maybe do 2 corners with 30hz and two corners with 100hz. another option is to build the panels on the axial mode points - length width or height - although corners have all modes.
thank you Glenn, look like, Ethan low bass trap is centered around 90 or 100 Hz, which is where porous traps straddling corners also peak What about the big corner Poly you suggested , do yo know approx the center freq? It will be more effective below 100hz than my large 4'x6'x4" 8 pound porous absorber across the corner or a flat panel trap? If the poly or panel trap really works , I don't need large 4x6 8 pound absorbers across the corners ... I will save some space !Yes, but if I were going to do that I'd tune the panel absorbers to a center frequency around 50 or 60 Hz. The "low bass" trap in my plans is centered around 90 or 100 Hz, which is where porous traps straddling corners also peak. So it makes more sense to use the panel traps to target the really low stuff where porous absorbers are less effective. This is the big feature of wood panel traps - they absorb low frequencies with a relatively thin profile. A 4-inch deep panel trap hits 100 percent absorption around 100 Hz. Even if you aim for 50 Hz you'll get 100 percent absorption with a much thinner profile than any type of fiberglass. --EthanHmmm, I wonder what 2 panel absorbers in the corner mounted flush to the wall, as ethan describes, and then with a standard broadband absorber straddling the corner in front of those would work? Perhaps the best of both worlds (pressure and velocity absorber) there....
B.D.R.
You asked me to have a look here.
But you're doing right with all your testing.
And whatever it remains difficult to draw general conclusions, which isn't that important since you're testing what's important in your specific circumstances.
When you speak about 1/4 round isolation (duct type isolation), then I do have measured them in a lab as well, and they also show this peaky around 100 Hz behavior (depending on size). I even wonder if not a bit more.
Hence using 1/4 circles will not gain you a lot.
Be careful to make panel traps or slat slot resonators in corners (which such open diffusers are) without testing them. You don't know exactly how they will behave.
If that rounded 1/4 circle is a closed panel, it will show an entirely different behavior than a traditional flat panel trap.
In groups like this one just combines principles in the assumption all these principles will support one another, but in fact people don't know. I as well see it as possible that you degrade principles.
This is not just an addition of possible good properties, but a new system with unknown or hard to quantify properties.
:twisted: The more Glenn masters sketchup (and Glenn is very good at it), the more unanswered questions are suggested as possible improvements.
Foam sculpting magic becomes sketchup magic.
For me, we do know how corner absorption works based on measurements (hence empirical). Converting them to slat resonators, in the assumption that it will reflect more highs is certainly correct, but what happens with the corner absorber in itself, I doubt anyone has any objective data to compare that.
That standard Lenrds do less in the lows is the logical consequence of being so small. What they do one can check on Ethan's site.
And if good measurements are still not on Auralex's site is their fault, and for me enough not to consider them any further.
It's almost a poor joke that to know what Lenrds do we have to check a competitors site.
In fact for their size and cost they are really good, but it's commercial hype that they still wants to live from the old magic rather than giving objective data.
But still it's not that simple that you can take 1 room with a very specific pattern in function of modal behavior, as a general conclusion of which is best or worse. For what is best is what solves the specific frequency related limitations of YOUR room.
Which does not means that your measurement series aren't very valuable.
To compare absorbers in themselves one has to use more neutral rooms and for now, with the uncertain behavior of corner absorption, even official measurement methods have their question marks.
as Eric points out, straddling the corner with panels or slats becomes an approximation since you can only average values to estimate the range of performance. since we're getting to specific frequencies, i'd stick with the idea of use porous absorbers across the corner and panel traps to address the specific frequencies. using the polys as diffusers flat on the walls as you have so far.
more playdoh: here's the correct poly design which is elliptical not round.
:roll:
Thanks for the encouragement.B.D.R. You asked me to have a look here. But you're doing right with all your testing. .
Too bad, they should make them bigger then, I paid for it...that standard Lenrds do less in the lows is the logical consequence of being so small. .
That's will be the simplest approach , but what about if you paid for it and then spent a years trying to figure out why you don't like how your room sound??And if good measurements are still not on Auralex's site is their fault, and for me enough not to consider them any further. .
Thanks Eric, Auralex offer specific room kits based on the dimension of the room. The Roominator kit for Live/rehearsal/tracking room include: 8 lenrds 24 2x2 2 inc studio foam 6 2x2 diffusers The Rominator kit for project studio include: 12 lenrds 36 2x2 2 inc studio foam 8 diffusers I have both , And additional 8 Lenrds. Note that the live/ tracking kit it's obviously intended for a room with real instruments ....and the kits are offered based on room dimension, a neutral room is not required. Most of the musicians don't know about room acoustics.., it's easy to believe in magic and spend all you have in colorful foam for your dreamy tracking room. About the big poly in the corners: If I place about 3 of my 6 feet tall Cylindrical diffuser in the corner behind the drum almost simulating a big Poly... I can axially hear the effect of absorption on the bass drum... The real sealed corner Poly filled with insulation should be very good! I never made one jet because I'm not sure if I like diffusion near the instruments...It's almost a poor joke that to know what Lenrds do we have to check a competitors site. In fact for their size and cost they are really good, but it's commercial hype that they still wants to live from the old magic rather than giving objective data. But still it's not that simple that you can take 1 room with a very specific pattern in function of modal behavior, as a general conclusion of which is best or worse. For what is best is what solves the specific frequency related limitations of YOUR room. Which does not means that your measurement series aren't very valuable. To compare absorbers in themselves one has to use more neutral rooms and for now, with the uncertain behavior of corner absorption, even official measurement methods have their question marks.