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Author Topic: Too much bass trapping?  (Read 8136 times)

Chris Griffith

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Too much bass trapping?
« on: September 01, 2008, 12:42:05 AM »

Bob Hodas stated in an online presentation on mixonline that he's had room issues that were caused by too much trapping.  

I've always read you cant have too much basstrapping.  Is this true?  

I'm about to build a new control room (11' 5"x 13 x 15'10" good ratios from looking at a mode calculator) and was planning to heavily trap the two front corners and build a 12" deep trapped back wall with homemade panel absorbers lining the back 4" of it covered by pink and rigid fiberglass on the front (not touching the panel traps) I'll also have a large soffit that goes all the way around the room that would be 3' tall and 2' wide covering all ceiling to wall corners.  Then 4" of treatment for a ceiling cloud and at first reflection points. So altogether I'll have about 15 to 20% of the cubic volume of the room filled with broadband absorption, most of it over a foot deep.  

Everything is going to be pink insulation stuffed tightly behind 4" of rigid fiberglass.  Does this sound like too much?  I'll also have 4'X8' area of some sort of diffusor (qrd, omnifussor or skyline) and slats on the back wall and lining most the soffits to keep the room sounding a little natural.  

I'd like the room to be as flat and neutral as possible.  My favorite control rooms are usually on the dead side.  Is this overkill for a room this size?  Am I going to put weird bumps in the low end or should I be fairly safe?  

Sorry for the ramble.  Too much coffee.  I'll try and post a sketchup of the room in the next couple days.  
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jfrigo

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Re: Too much bass trapping?
« Reply #1 on: September 01, 2008, 02:40:35 AM »

Chris Griffith wrote on Mon, 01 September 2008 00:42

Bob Hodas stated in an online presentation on mixonline that he's had room issues that were caused by too much trapping.  

I've always read you cant have too much basstrapping.  Is this true?    



Generally speaking, for a small room acoustics, like control rooms, it's hard to overdo bass trapping if its the right kind. If it's effective at the wrong frequencies, ineffective where you have problems, doesn't extend deep enough, or covers a lot of area and is too absorptive at mid and high frequencies, then it can be a problem.

In large room acoustics it can also cause trouble where the cutoff frequency is so low that the small room modal problems we are used to talking about are no longer the issue, and depending on the room application, you want to keep as much of that low frequency energy in the room (think large performance spaces and concert halls etc.)

If planned and designed properly, and integrated as a part of a whole-room plan, a large amount of trapping is unlikely to cause problems. However, those are some serious cavets. Some people order pre-made traps that are wrong for the job, and put them all over, and this can be a true mess.
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Ethan Winer

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Re: Too much bass trapping?
« Reply #2 on: September 01, 2008, 01:29:38 PM »

Chris Griffith wrote on Mon, 01 September 2008 00:42

I've always read you cant have too much basstrapping.  Is this true?


Yes, in a room the size you're making it's not possible to have too much bass trapping, Assuming, as Jay mentioned, that it's good bass trapping, extends to a low enough frequency, and optionally absorbs mids and highs less than is absorbed below about 300 to 400 Hz.

Quote:

Is this overkill for a room this size?  Am I going to put weird bumps in the low end or should I be fairly safe?


Adding bass traps should never introduce new peaks and nulls. It can only make things better. And it's not just peaks and nulls that matter, but ringing too.

--Ethan

Chris Griffith

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Re: Too much bass trapping?
« Reply #3 on: September 01, 2008, 03:24:34 PM »

In the Bob Hodas presentation he said there have been times when he's been tuning rooms and removing bass traps has helped even out the low end response. This has me scared since it goes against how I was thinking of building my new room.  

I figure if I start with a room with evenly spaced modes and trap the hell out of it (thinking about just framing a false ceiling at 8 ft so I can have 3.5 ft of broadband trapping over the entire room with deep absorption in the front corners and the entire back wall) and add slats and diffusers over the absorption in key places to keep the room from sounding too dead I'll be safe.  

I wish I had the money to hire a designer but its just not possible.  Is this a safe bet for designing a room?  I'm ok with loosing a lot of space in return for smooth even bass.  
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jfrigo

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Re: Too much bass trapping?
« Reply #4 on: September 01, 2008, 05:30:40 PM »

Chris Griffith wrote on Mon, 01 September 2008 15:24

In the Bob Hodas presentation he said there have been times when he's been tuning rooms and removing bass traps has helped even out the low end response. This has me scared since it goes against how I was thinking of building my new room.  


It's been several years so the details of my recollection may be off, but I seem to remember talking to Bob and hearing that story about a certain kind of commercial bass trap that was more narrow-band (tuned), and the optimum frequency did not match the modes in the room, and when adding many of the same, less-than-appropriate units rather than a more wide-band approach, it was bad news.

Quote:


I figure if I start with a room with evenly spaced modes and trap the hell out of it (thinking about just framing a false ceiling at 8 ft so I can have 3.5 ft of broadband trapping over the entire room with deep absorption in the front corners and the entire back wall) and add slats and diffusers over the absorption in key places to keep the room from sounding too dead I'll be safe.  

I wish I had the money to hire a designer but its just not possible.  Is this a safe bet for designing a room?  I'm ok with loosing a lot of space in return for smooth even bass.  


The general approach could work, but the devil is in the details. At the very least, I'd feel a little constricted by that ceiling height, and I'd have to know more about how you intend to build that "false" ceiling. Is it flat? Angled? Are there clouds? Is it all transparent? Does that mean it will be 100% absorptive? That ceiling could be trouble, though the core idea of trapping in a cavity above a ceiling is certainly not a bad one. Extra space above a room is a great place for some additional trapping.

Also, depending on what kind of slats and diffusors you intend to put over the back wall, where and how, it could significantly impact how it responds. It's hard to say for sure without seeing more detailed plans and doing some due dilligence on them, which of course is what a consultant would do.

So basically, some of your general ideas could work well, but implimented incorrectly, they still could be pretty disappointing.
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Chris Griffith

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Re: Too much bass trapping?
« Reply #5 on: September 02, 2008, 01:34:23 AM »

jfrigo wrote on Mon, 01 September 2008 15:30

 

It's been several years so the details of my recollection may be off, but I seem to remember talking to Bob and hearing that story about a certain kind of commercial bass trap that was more narrow-band (tuned), and the optimum frequency did not match the modes in the room, and when adding many of the same, less-than-appropriate units rather than a more wide-band approach, it was bad news.





Good to know.. I was thinking it was a commercial broadband absorber of some kind.  

Basically my idea for the ceiling is to frame a new ceiling inside the room at 8 ft tall and fill the 3.5ft of space above it with R19 insulation hanging from the ceiling going all the way to the frame of the false ceiling.  Then I'll fill the space between the studs with some sort of compressed fiberglass or rockwool and cover the entire thing in fabric.  

Ive seen several studios with a similar ceiling.  Is this a bad idea?  I'm ok with loosing space if I'll gain smoother low end.  I don't plan on having many people in the room so space isnt a huge concern.  

I'll try and post a sketchup in the next couple days of the entire room to get more advice.  

Thanks so much already!

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Ethan Winer

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Re: Too much bass trapping?
« Reply #6 on: September 02, 2008, 01:19:34 PM »

jfrigo wrote on Mon, 01 September 2008 17:30

a certain kind of commercial bass trap that was more narrow-band (tuned), and the optimum frequency did not match the modes in the room


Yeah, that's the only explanation that makes sense to me.

--Ethan

brett

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Re: Too much bass trapping?
« Reply #7 on: September 04, 2008, 07:01:48 PM »

Why does it have to be 3.5 ft thick? You are already doing a  cloud. So 3.5ft thick on the ceiling sounds excessive and you lose a lot of asthetics. You should do 12" drop ceiling with r32 a ft thick and then your cloud. Would give you two extra ft in the room.  
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Chris Griffith

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Re: Too much bass trapping?
« Reply #8 on: September 05, 2008, 12:52:30 AM »

Oops I forgot to say I was getting rid of the cloud if I added the lower ceiling. The whole thing would be like an enormous basstrap/ cloud.  

The other idea is just a 3' by 2' soffit that goes all the way around the room in the ceiling to wall intersection and a cloud over the mix position.  

If I'm not going to gain a lot by having the entire ceiling filled up I'd rather do the soffits so I can retain some of the tall ceiling height.

I figure in a room this small I need as much deep trapping as possible.  
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brett

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Re: Too much bass trapping?
« Reply #9 on: September 05, 2008, 08:40:59 PM »

The goal shouldn't be to make the entire ceiling non reflective but the room balanced. Doing all the soffits, you still need to do the floor to wall corners evenly. and wall to wall corners symetrical.

I had a 10x10 room I got some really good low end response out of by using 1ft thick rear wall absorbtion and 8" thick front wall. then symetrical placment of all other corners 4", two 4" panels to the side of me and a 6" cloud.

But you really can't hurt the room with too much broad band absorbtion. You can hurt your wallet.


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maarvold

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Re: Too much bass trapping?
« Reply #10 on: October 07, 2008, 01:15:30 PM »

Ethan Winer wrote on Mon, 01 September 2008 10:29

Chris Griffith wrote on Mon, 01 September 2008 00:42

I've always read you cant have too much basstrapping.  Is this true?


Yes, in a room the size you're making it's not possible to have too much bass trapping, Assuming, as Jay mentioned, that it's good bass trapping, extends to a low enough frequency, and optionally absorbs mids and highs less than is absorbed below about 300 to 400 Hz.

Quote:

Is this overkill for a room this size?  Am I going to put weird bumps in the low end or should I be fairly safe?


Adding bass traps should never introduce new peaks and nulls. It can only make things better. And it's not just peaks and nulls that matter, but ringing too.

--Ethan


I have been chasing GREAT low end (huge, powerful, articulate, pitch-defined) in my small control room for around 3 years now.  I am using a lot of proprietary design membrane bass trapping and a couple of SpringTraps.  With the membrane absorbers, I started with X amount, then added more, then more, then more, then more again, then even more--and this last round was a big addition.  I don't think--physically--I could add much more, if any.  With every single addition things improve.  At around step 3 (of 6) there started to be a 'stillness' or calmness' to the air--as if it was a much bigger room, or maybe as it's sonic signature became less and less a part of the equation.  I have truly full range monitoring: custom-designed 3 way speakers, 2 custom sealed box subs with JL Audio drivers, digital room correction (separate digital correction and crossovers for the subs) and over 3,000 watts RMS.  I can truthfully say there is not a control room in L.A. that I would rather be sitting in listening to music right now.  

With this last, and probably final, addition of membrane absorbers, the bottom end's power and effortlessness has become almost limitless in terms of any situation I might encounter in real life, except maybe being run down by an 18 wheeler or being in an earthquake.  But the other interesting thing is that the soundstage has finally completely 'broken free' of the speakers, floating whatever space there is in the recording in front of me as if I was listening to it through a big, glassless window frame.  All kinds of little sonic details (that don't seem like they would have anything to do with the low end) come peeking through without drawing extra attention to themselves.  

FWIW, I'm also using a dozen RPG Skyline Panels and a fair amount of carefully-placed 4" thick open cell foam.  

Thanks A LOT to this forum for helping me find my way to this sonic point, which  I am now really enjoying.  
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Michael Aarvold
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chorga1

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Re: Too much bass trapping?
« Reply #11 on: October 07, 2008, 06:32:10 PM »

This is a lil off-topic but,


Maarvold - how are those JL Audio drivers for subs? Aren't they used mostly in car audio???
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maarvold

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Re: Too much bass trapping?
« Reply #12 on: October 07, 2008, 08:34:00 PM »

JL Audio started in car audio, but they make some extremely highly-regarded self-powered subs now.  They also hold several patents for driver design that apply directly to sub drivers.  I remember Vance Dickinson, author of "The Loudspeaker Design Cookbook", writing somewhere (maybe in a review) that the JL Audio drivers he tried out kind of unnerved him because they always seemed to be playing too loud, but then he re-evaluated his diagnosis and decided that actually everything else's voice coils  heated up and started compressing EXCEPT the JL Audio drivers and he just hadn't experienced no compression in sub drivers before.  I may have the details slightly wrong, but the essence of the story is certainly correct.  I'm using 2 - 10" drivers and they totally kick ass.  
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Michael Aarvold
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Thomas Jouanjean

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Re: Too much bass trapping?
« Reply #13 on: October 13, 2008, 06:31:59 AM »

Chris Griffith wrote on Sun, 31 August 2008 23:42


I've always read you cant have too much basstrapping.  Is this true?  

[...]

So altogether I'll have about 15 to 20% of the cubic volume of the room filled with broadband absorption, most of it over a foot deep.  

[...]

I'd like the room to be as flat and neutral as possible.  My favorite control rooms are usually on the dead side.  Is this overkill for a room this size?  Am I going to put weird bumps in the low end or should I be fairly safe?  


The risk in these situations is that from a certain point you will keep adding material/traps which will be basically useless to treat the remaining problems in your room.

Because Rockwool & Co based treatment works only within a certain bandwidth (and usually when FRK type is used, it tends to act more membrane like, but with a rather narrow Q - so beware) you will keep treating the same frequencies on and on and not really focus on where your remaining problems are.

Treatment based on resistance to flow can only do so much in fixing problems in the LF region.

In most cases, those situations result in very dead rooms with a boomy/loose low-end with heavy pressure variations in the room and more often than not is followed by a pretty poor imaging too.

If you have a bit of time, I would suggest you rather go step by step and regularly evaluate the situation (response of the room in many different points, RT etc). Keeping a simple journal of the evolutions in the room treatment and measurements provides very useful and reliable info. It will help you dicriminate between useful new treatment and useless new treatment.

That you consider diffusion too is very good, as this is a very important factor. But not all diffusors are born equal  Smile so spend some time thinking about which type would suit your room best.

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Thomas Jouanjean
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