It seems a lot of project studios have a major problem with a null at the mix position in the low bass. It is very apparent with most of the projects I master that are mixed in project studios, because I find they generally have way too much low end. This is also important to me at this time because I am helping someone design a small studio and want to try and avoid this problem. I myself have mixed in a lot of different backroom environments (hundreds of live to air live mixes), with from terrible to really bad accoustics across the frequency band, yet the only thing that I really couldn't coupe with was when there was a strong null in the low end. It really drives me crazy and I never get comfortable with things.
What is the math involved? Is it the distance of the mix position to the back wall that is the main issue or the overall room dimensions or ? Is it a matter or determining the main frequency and building a resonator that centers on and absorbs this frequency?
I have attached some basic math for a critque. Thanks!
Bass Nulls - Mix Position - or - Room Dimesions or ?
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Howardk
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knightfly
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Nulls will happen at odd 1/4 wavelengths, not half - 1/4 wave from the wall, then to wall, and back to that 1/4 wave distance, = 1/2 wavelength - this puts the original out of phase by 180 degrees with the reflection, so they cancel (minus the slight attenuation caused by inverse square law) - the same occurs at other odd 1/4 wavelengths, like 3/4, 5/4, 7/4, etc - but to a lesser degree in each successive case (again, due to the reflection's loss of amplitude) -
Other causes - mixing with no sub and 5-6" nearfields - having either your head or speakers located in modal peak locations - one "freebie" I've found useful for avoiding this -
http://www.harman.com/wp/index.jsp?articleId=131
This mode calc puts a peak/null graph onscreen for all three axial modes, so you can see exactly where peaks and nulls occur and avoid them with placement.
For sub placement, the simplest way is to put up a known commercial mix, place the sub in your chair, and crawl around the floor til the bass sounds right - then just swap positions, putting the sub where you thought things sounded "right" -
If you're using near/midfields NOT soffited in a parallel walled room, this might be some help -
http://www.cardas.com/cgi-bin/main_cont ... Room+Setup
There are several more pages, click the link at the bottom labeled "For those who must know more" -
Don't bother trying to get the laser link to work, apparently checkpoint is long gone... Steve
Other causes - mixing with no sub and 5-6" nearfields - having either your head or speakers located in modal peak locations - one "freebie" I've found useful for avoiding this -
http://www.harman.com/wp/index.jsp?articleId=131
This mode calc puts a peak/null graph onscreen for all three axial modes, so you can see exactly where peaks and nulls occur and avoid them with placement.
For sub placement, the simplest way is to put up a known commercial mix, place the sub in your chair, and crawl around the floor til the bass sounds right - then just swap positions, putting the sub where you thought things sounded "right" -
If you're using near/midfields NOT soffited in a parallel walled room, this might be some help -
http://www.cardas.com/cgi-bin/main_cont ... Room+Setup
There are several more pages, click the link at the bottom labeled "For those who must know more" -
Don't bother trying to get the laser link to work, apparently checkpoint is long gone... Steve
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Howardk
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- Location: Canada
Oops, yes 1/4 wave length from the wall. Thanks for giving my brain a shake Steve! I have corrected my example sheet and attached.
Good idea on the sub on the chair test, I hadn't thought of that.
In the case that changing speaker physical placement is not an option (as is the case with near fields and no sub), what are the most effecient and compact dampening resonator designs for these low frequencies (to absorb instead of reflecting)?
Good idea on the sub on the chair test, I hadn't thought of that.
In the case that changing speaker physical placement is not an option (as is the case with near fields and no sub), what are the most effecient and compact dampening resonator designs for these low frequencies (to absorb instead of reflecting)?
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knightfly
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Kinda losing me on this one - you started out asking about nulls, and now we're trapping peaks 
I'm also not following why you can't move nearfields just because there's no sub - I've had people on different BBS's move their speakers as little as 3-4 inches, and been called a genius - one guy even made a fancy plaque for the front of the 4" spacers he made for his speakers, that said "Sound by Knightfly" -
To my way of thinking, the first thing to do in ANY room is to make sure your speakers/head are in neither a void or a boosted area for any known modal frequencies - this, because no amount of EQ can fix a modal peak - as soon as you move your head a tiny bit, all the cut you applied is now "gutting" the sound - and boosting EQ more than a little can wreak havoc with phasing in and around the affected frequency - Sooo, before you reach for any knobs you need to first get all the "temporal" problems fixed in the room - this needs to be done by keeping heads, speakers, mics and instruments out of obvious null/peak points. In order to do this, you need to be able to easily calculate where those "no-no" points are, in all three axes.
If the room has bad LWH ratios which cause some of the modal problems to be un-fixable by positioning, and you can't change the dimensions of the room, then it's time for more surgical traps, some of which can be taylored to the specific problem frequencies (for peaks, not nulls - although taming peaks will help even out the nulls) - all rooms, however, can benefit from broadband trapping of corners .
Users of NS-10's claim they watch the cones to tell if they're overdoing the bass, since those speakers are pretty bass-shy - if I were stuck using small speakers, I'd keep a top set of (flat response)cans around(NOT Sony, a lot of them are too hyped in the bottom) to check the rest of the spectrum on from time to time.
Wall construction is another gray area for a room - if you're in a room whose walls are solid concrete, the bass will drive you nuts - if your walls are light paneling with some insulation inside, they can act as panel traps and give you a bass-light condition. Sheet rock walls provide some panel trap effect, usually around 65-90 hZ depending on cavity depth, # of layers and sheet rock thickness.
There are many more factors that can affect bass in a room, and we can eventually cover all of them - but to start, I'd recommend NOT building a bad ratio room, NOT rushing into building til a full understanding of what controls what is achieved, and carefully choosing both speakers and their placement in all three axes - those three things will go a long way toward getting a good sounding room that won't lie to you... Steve
I'm also not following why you can't move nearfields just because there's no sub - I've had people on different BBS's move their speakers as little as 3-4 inches, and been called a genius - one guy even made a fancy plaque for the front of the 4" spacers he made for his speakers, that said "Sound by Knightfly" - To my way of thinking, the first thing to do in ANY room is to make sure your speakers/head are in neither a void or a boosted area for any known modal frequencies - this, because no amount of EQ can fix a modal peak - as soon as you move your head a tiny bit, all the cut you applied is now "gutting" the sound - and boosting EQ more than a little can wreak havoc with phasing in and around the affected frequency - Sooo, before you reach for any knobs you need to first get all the "temporal" problems fixed in the room - this needs to be done by keeping heads, speakers, mics and instruments out of obvious null/peak points. In order to do this, you need to be able to easily calculate where those "no-no" points are, in all three axes.
If the room has bad LWH ratios which cause some of the modal problems to be un-fixable by positioning, and you can't change the dimensions of the room, then it's time for more surgical traps, some of which can be taylored to the specific problem frequencies (for peaks, not nulls - although taming peaks will help even out the nulls) - all rooms, however, can benefit from broadband trapping of corners .
Users of NS-10's claim they watch the cones to tell if they're overdoing the bass, since those speakers are pretty bass-shy - if I were stuck using small speakers, I'd keep a top set of (flat response)cans around(NOT Sony, a lot of them are too hyped in the bottom) to check the rest of the spectrum on from time to time.
Wall construction is another gray area for a room - if you're in a room whose walls are solid concrete, the bass will drive you nuts - if your walls are light paneling with some insulation inside, they can act as panel traps and give you a bass-light condition. Sheet rock walls provide some panel trap effect, usually around 65-90 hZ depending on cavity depth, # of layers and sheet rock thickness.
There are many more factors that can affect bass in a room, and we can eventually cover all of them - but to start, I'd recommend NOT building a bad ratio room, NOT rushing into building til a full understanding of what controls what is achieved, and carefully choosing both speakers and their placement in all three axes - those three things will go a long way toward getting a good sounding room that won't lie to you... Steve
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Howardk
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- Location: Canada
Thanks Steve. Sorry for the confusion, I may be trying to cover too many bases with my questions. I understand what you are saying to some degree.
My focus in this post is on low frequencies (sub 100 Hz). It has been my experience that slight position change to speakers, or one's head, makes little or no noticable difference when talking about low frequencies. I had assumed that a low freq absorber would be able to counteract a low frequency null if tuned to the correct frequency (in the case the rooms size is less than optimum and the monitor position somewhat fixed for practical layout, therefore no real position change options). What am I missing in my thinking?
In the case of the people I am trying to help out (Teen Drop-in Center Studio), the overall space has been determined (the room's envelop is concrete and brick so it will certainly have considerable issue with regard to bass), but the individual rooms are still up for grabs, as I try to work out the best compromizes for a $5000 USD construction budget (including electrical and ventilation). It is interesting that almost all the studio designs are *not* rectangles, but more complex shapes, yet all the basic design tools for calculating room modes are for rectangular rooms. How should one be looking at the room ratios with these more complex shapes?
My focus in this post is on low frequencies (sub 100 Hz). It has been my experience that slight position change to speakers, or one's head, makes little or no noticable difference when talking about low frequencies. I had assumed that a low freq absorber would be able to counteract a low frequency null if tuned to the correct frequency (in the case the rooms size is less than optimum and the monitor position somewhat fixed for practical layout, therefore no real position change options). What am I missing in my thinking?
In the case of the people I am trying to help out (Teen Drop-in Center Studio), the overall space has been determined (the room's envelop is concrete and brick so it will certainly have considerable issue with regard to bass), but the individual rooms are still up for grabs, as I try to work out the best compromizes for a $5000 USD construction budget (including electrical and ventilation). It is interesting that almost all the studio designs are *not* rectangles, but more complex shapes, yet all the basic design tools for calculating room modes are for rectangular rooms. How should one be looking at the room ratios with these more complex shapes?
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Ethan Winer
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Re: Bass Nulls - Mix Position - or - Room Dimesions or ?
Howard,
> Is it the distance of the mix position to the back wall <
Yes, that's a huge factor. To my way of thinking, room modes are a subset of the basic peak/null problems caused by simple acoustic interference. As Steve said, speaker placement can influence the response at the mix position. Though in my experience you can take that only so far and get only so much improvement. In the end you'll need a fair amount of bass trapping to be able to mix with confidence, no matter what the room's dimensions and shape are.
> what are the most effecient and compact dampening resonator designs for these low frequencies <
The notion of designing bass traps that target specific frequencies is old school, and not so effective in the small rooms people are using these days. What you really want is broadband absorption that works well to as low a frequency as possible. The most effective design I know of is the traps my company sells.
But you can get good results with either thick, dense, rigid fiberglass straddling the room corners, or a mix of low-bass and high-bass wood panel membrane traps mounted flat against the walls. John Sayers, who hosts this fine forum, often uses slat resonator style traps.
--Ethan
> Is it the distance of the mix position to the back wall <
Yes, that's a huge factor. To my way of thinking, room modes are a subset of the basic peak/null problems caused by simple acoustic interference. As Steve said, speaker placement can influence the response at the mix position. Though in my experience you can take that only so far and get only so much improvement. In the end you'll need a fair amount of bass trapping to be able to mix with confidence, no matter what the room's dimensions and shape are.
> what are the most effecient and compact dampening resonator designs for these low frequencies <
The notion of designing bass traps that target specific frequencies is old school, and not so effective in the small rooms people are using these days. What you really want is broadband absorption that works well to as low a frequency as possible. The most effective design I know of is the traps my company sells.
But you can get good results with either thick, dense, rigid fiberglass straddling the room corners, or a mix of low-bass and high-bass wood panel membrane traps mounted flat against the walls. John Sayers, who hosts this fine forum, often uses slat resonator style traps.--Ethan
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jim69
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New Room - No Bass
Hey guys,
Just put this room studio together....
Ok I am having the same exact problem. But im not looking to get too technical with calcs and quantum physics =) I need to get somewhat accurate bass in my Mix Position.
Think its possible to get some assistance from the experts (but in laymans terms) ?
Thanks all in advance,
jim69
Cliff Notes -
-room is about 14x10 and 8-10ft ceilings
-to my left is a closet with no doors, goes about 9-10ft high
has record shelves but empty space above them (sound probably gettin lost)
-my mix position is about 6 feet from the front wall
Just put this room studio together....
Ok I am having the same exact problem. But im not looking to get too technical with calcs and quantum physics =) I need to get somewhat accurate bass in my Mix Position.
Think its possible to get some assistance from the experts (but in laymans terms) ?
Thanks all in advance,
jim69
Cliff Notes -
-room is about 14x10 and 8-10ft ceilings
-to my left is a closet with no doors, goes about 9-10ft high
has record shelves but empty space above them (sound probably gettin lost)
-my mix position is about 6 feet from the front wall
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Ethan Winer
- Senior Member
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Re: New Room - No Bass
Jim,
> im not looking to get too technical with calcs and quantum physics =) I need to get somewhat accurate bass in my Mix Position. <
You need bass traps, plain and simple. The more you put in the room, the better the LF response you'll get, and the more even the bass will be around the room.
Was that okay?
--Ethan
> im not looking to get too technical with calcs and quantum physics =) I need to get somewhat accurate bass in my Mix Position. <
You need bass traps, plain and simple. The more you put in the room, the better the LF response you'll get, and the more even the bass will be around the room.
Was that okay?
--Ethan
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nukmusic
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- Location: Dallas,Tx / New Orleans, LA
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Ok.....I'm up on the above. But how is this calculated for a room with non-parallel walls???
http://www.nukmusic.com/studiodesign.jpg
http://www.nukmusic.com/studiodesign.jpg
Docta'J
http://www.nukmusiccompany.com
http://www.nukmusiccompany.com
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knightfly
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- Location: West Coast, USA
J, without spending a few weeks playing with CARA, which may or may not be able to model such a room (haven't had the time to dig as deep as that requires) the only non-physical way I know is to AVERAGE your dimensions - if your CR is 11 feet across the front and 14 feet across the back (and symmetrical) you would use 12-1/2 feet for the average dimension. Same with ceilings if they're not parallel.- for a live room with NO symmetry or parallel walls, good luck - best just build it, calculate what you need for balanced RT60, listen and tweak. This is where either a helper or a pair of accurate RF cordless headphones helps with mic/instrument placement.
If you DO have the time, CARA is a TON of deep for a pittance -
http://www.cara.de/ENU/index.html
Hope that helped... Steve
If you DO have the time, CARA is a TON of deep for a pittance -
http://www.cara.de/ENU/index.html
Hope that helped... Steve
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Eric_Desart
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Hello Steve,
For what it's worth: just a general remark.
This corridor acts as a connected room.
If not strongly absorbed, this mostly gives a strange (not so healthy) effect.
I've been playing with Cara too now (on someone elses CPU).
Amazing what they give for the price.
On a scale from 1 to 10 ratio value/price = 20.
However I want to check some things with them. The program can't handle diffraction (as far as I can see). So I don't expect them to handle such a corridor correctly. It will also not see the open end (entrance) of this corridor as an acoustic boundary.
What I miss in Cara is a better explenation how they handle things.
I can't find how they handle temperature. It seems that they take temperature into acount for air absorption, but which formula do they use for velocity?
I plan (hope) to contact them for some additional background.
I still didn't found which sound speed they exactly use.
Their 1/9 octave band scale is strangly build on a log 2 scale with 10 Hz as an arbitrary start. Why they didn't use a more logical log 10 scale in order to match the official 1/3 octaveband scale sounds a bit strange to me.
But anyhow it's indeed incredible what the program does for the price.
Anyhow this are just some thoughts, nothing more.
The guy with the CPU I used doesn't have this teaching CD.
Does this has some texts with more in-depth explenation?
Warm regards
Eric
For what it's worth: just a general remark.
This corridor acts as a connected room.
If not strongly absorbed, this mostly gives a strange (not so healthy) effect.
I've been playing with Cara too now (on someone elses CPU).
Amazing what they give for the price.
On a scale from 1 to 10 ratio value/price = 20.
However I want to check some things with them. The program can't handle diffraction (as far as I can see). So I don't expect them to handle such a corridor correctly. It will also not see the open end (entrance) of this corridor as an acoustic boundary.
What I miss in Cara is a better explenation how they handle things.
I can't find how they handle temperature. It seems that they take temperature into acount for air absorption, but which formula do they use for velocity?
I plan (hope) to contact them for some additional background.
I still didn't found which sound speed they exactly use.
Their 1/9 octave band scale is strangly build on a log 2 scale with 10 Hz as an arbitrary start. Why they didn't use a more logical log 10 scale in order to match the official 1/3 octaveband scale sounds a bit strange to me.
But anyhow it's indeed incredible what the program does for the price.
Anyhow this are just some thoughts, nothing more.
The guy with the CPU I used doesn't have this teaching CD.
Does this has some texts with more in-depth explenation?
Warm regards
Eric
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knightfly
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- Location: West Coast, USA
Not really - CARA is installed on my laptop (not with me at the moment) but if I remember correctly, the tutorial CD has mainly just several "lessons" on how to do things, not much on how they are computed - these "lessons" are narrated by the person running the software, and you see what happens on the screen as they do the various operations. Even so, I consider that extra disk essential to getting a good start using the software. Even buying the complete package (except for the controller) is still amazingly cheap for what's there.
Given proper specs for your particular speakers, it even lets you model your own speakers as part of the simulation - I did wish they had included more ready-made models of speakers, but it's hard to complain for the price.
I've yet to find time to check this out, but it looks like you can model almost any architectural feature with enough time to play with it, including splayed walls, vaulted ceilings, etc -
Sorry I'm not more help, maybe when I get more "play time"... Steve
Given proper specs for your particular speakers, it even lets you model your own speakers as part of the simulation - I did wish they had included more ready-made models of speakers, but it's hard to complain for the price.
I've yet to find time to check this out, but it looks like you can model almost any architectural feature with enough time to play with it, including splayed walls, vaulted ceilings, etc -
Sorry I'm not more help, maybe when I get more "play time"... Steve
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lovecow
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- Location: Kansas, USA
Re: Bass Nulls - Mix Position - or - Room Dimesions or ?
Note: This might be a bit OT, so the mods should feel free to point me in the direction of a new thread, if that's necessary.Ethan Winer wrote:Yes, that's a huge factor. To my way of thinking, room modes are a subset of the basic peak/null problems caused by simple acoustic interference.
FWIW, I recently built Speaker Boundary Interference Response (SBIR - the technical term for the "peak/null problems" mentioned above) into a test version of an LF response spreadsheet I created a while back. Originally, I created it only to predict modal response for small, rectangular rooms. Now that I've included the effects of SBIR on overall response, I thought this a good place to mention that the modal response still dominates the net response. This is as I would expect since I have compared many measured LF responses in small rooms with predicted modal responses and they always tend to agree very well.
So, this concept of modes as a "subset" of SBIR is incorrect. Modal response and SBIR are mutually exclusive. This is neither unexpected, nor new. Besides my own observations over the years, Richard V. Waterhouse concluded much to the same effect in the myriad papers he wrote in the 1950s and '60s on wave interference.
It should be noted that my interjection here stems not only from this thread, but others where I have seen this "subset" concept proposed. I apologize if it seems like grandstanding.
Final note: I apologize for omitting any link to the aforementioned spreadsheet. It is not yet 100% complete (other things I still wish to include) and the most recent version is over 31 MB. I may post it to the Auralex site in the future so stay tuned.
Best regards,
Jeff D. Szymanski
Chief Acoustical Engineer
Auralex Acoustics, Inc.
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knightfly
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- Location: West Coast, USA
Jeff, there's absolutely no need for apology here - I've yet to see a post from you on ANY forum that isn't more edifying, more gentlemanly, or less commercial than anyone could expect from someone in your position.
Sometimes I think that if I had just printed out all your posts from the different boards that I could have saved myself several hundred $$$ in acoustics books - oops, too late
Thanks... Steve
Sometimes I think that if I had just printed out all your posts from the different boards that I could have saved myself several hundred $$$ in acoustics books - oops, too late
Thanks... Steve
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nukmusic
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- Location: Dallas,Tx / New Orleans, LA
- Contact:
Steve, thanks for the link......I'll look into it more. Great measurement guess too.
The studio is complete, except for the bath. I have to dig under(plumbing) my slab, which i haven't had the time to do
http://www.nukmusic.com/doctasoffice.jpg
I still have some gear to buy and connect. But the CR sound pretty darn good when playing back commerical cds. I do have a little dip around 180 r so(i think) at the mix position...... And a slight Bass null, but I can still hear what's going on. On the sofa, the commerical cds sounds like magic, almost perfect. The bass sound like a there is a sub in the room, but not overwhilming. I do mostly R&B and Hip-Hop, so this is a plus. I think the Mackie HR824's have a midrange dip also, but when played together with my Hafler M5's adds back the lower mids, in turn, puts things on the money(for some strang reason
).
I have 2 16"x4' bass tubes in the front corners, and 2" and 6" foam onthe back wall, 3' x 6' x 6" hanger on the ceiling. A little 2" aurlex on the sides and foam wall. Overall the room sound nice. My ears are great but I may get someone come in to test it out, to see if more tweaking can be done. Maybe I'm just luck to get the CR sounding good on the first go round? I have mixed a fews songs, which turned out nice. Has a listen: MP3 clip
The booth has some of the same treatment and sounds good for close micing, but far micing has that upper mid sound(empty) may be the mic too???. I have to do I haven't tried drums yet.
Thanks
The studio is complete, except for the bath. I have to dig under(plumbing) my slab, which i haven't had the time to do
http://www.nukmusic.com/doctasoffice.jpg
I still have some gear to buy and connect. But the CR sound pretty darn good when playing back commerical cds. I do have a little dip around 180 r so(i think) at the mix position...... And a slight Bass null, but I can still hear what's going on. On the sofa, the commerical cds sounds like magic, almost perfect. The bass sound like a there is a sub in the room, but not overwhilming. I do mostly R&B and Hip-Hop, so this is a plus. I think the Mackie HR824's have a midrange dip also, but when played together with my Hafler M5's adds back the lower mids, in turn, puts things on the money(for some strang reason
). I have 2 16"x4' bass tubes in the front corners, and 2" and 6" foam onthe back wall, 3' x 6' x 6" hanger on the ceiling. A little 2" aurlex on the sides and foam wall. Overall the room sound nice. My ears are great but I may get someone come in to test it out, to see if more tweaking can be done. Maybe I'm just luck to get the CR sounding good on the first go round? I have mixed a fews songs, which turned out nice. Has a listen: MP3 clip
The booth has some of the same treatment and sounds good for close micing, but far micing has that upper mid sound(empty) may be the mic too???. I have to do I haven't tried drums yet.
Thanks
Docta'J
http://www.nukmusiccompany.com
http://www.nukmusiccompany.com