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Creating a false ceiling as a huge bass trap?!?

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Creating a false ceiling as a huge bass trap?!?

Postby Siejen » Mon Nov 22, 2004 5:52 pm

Hi all,
My studio is the spare bedroom in a 1930's semi. Its 3m x 3.1m x 2.7m tall. I want to improve the low frequency performance of the room as I'm finding it really difficult to judge the level of bass in my mixes. Standard issue problem, they don't translate well!
The standard solution is to install bass traps in all the corners / wall joining points, but can I do something cleverer? To move the room away from being a perfect cube I'm thinking of lowering the ceiling to 2.5m high, by installing a complete ceiling of Rockwool RW3 or 5 (preferences on a postcard) with a gap (say 10cm Rockwool, 10cm air gap) thus creating a serious bass trap the size of the room?
I realise this will do nothing for flutter echoes and the like, but is there any reason this isn't better than the few panel traps that I could fit in my room (other corners are inhabited by a door and a boiler)?

All thoughts appreciated,
Iain
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Re: Creating a false ceiling as a huge bass trap?!?

Postby Ethan Winer » Mon Nov 22, 2004 6:00 pm

Iain,

> I'm thinking of lowering the ceiling to 2.5m high, by installing a complete ceiling of Rockwool RW3 or 5 <

Yes, that's a great idea. You'll still benefit even further from adding more fiberglass in the wall-wall corners, but covering the entire ceiling will definitely help.

--Ethan
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Re: Creating a false ceiling as a huge bass trap?!?

Postby Siejen » Mon Nov 22, 2004 6:04 pm

Many thanks Ethan.
Having read your quite comprehensive writings on the subject I was hoping to catch you online..... Must be my lucky day. :lol:

Iain
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Re: Creating a false ceiling as a huge bass trap?!?

Postby Hugh Robjohns » Tue Nov 23, 2004 10:15 am

Yes, the ceilning trap idea will help. Paul and I visited a domestic spare room studio in a recent Studio SOS article where the guys had done exactly this (only using dense foam instead of rockwool).

However, this approach doesn't address all the problems, and as Etahn has said, I would suggest efficient corner trapping is still an important aspect to do as well.

The Studio SOS I referred to above hadn't installed any corner trapping, and although the level of bass in the room was far more consistent than it was without the ceiling trap, there was still some variation -- most significantly an incredible null in the bass response right in the centre of the room !

Hugh
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Re: Creating a false ceiling as a huge bass trap?!?

Postby Siejen » Tue Nov 23, 2004 1:35 pm

OK, thanks for that. As I said, I can get 2 corners trapped, but am scuppered on the other two. Naturally the two I can trap are behind the monitors...

Mind you, the facing wall has a sofabed on it and thats big and full of foam. Its got to help :D

Another weekend, another sum of money at DIY superstore.

Iain
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Re: Creating a false ceiling as a huge bass trap?!?

Postby Paul Woodlock » Tue Nov 23, 2004 6:46 pm

Siejen wrote:OK, thanks for that. As I said, I can get 2 corners trapped, but am scuppered on the other two. Naturally the two I can trap are behind the monitors...

Mind you, the facing wall has a sofabed on it and thats big and full of foam. Its got to help :D

Another weekend, another sum of money at DIY superstore.

Iain

Greetings

Don't forget Horizontal corners. Where wall meets ceiling ( Or floor )


btw- Don't buy your rockwool slabs at DIY superstores. Far too expensive.

Goto a building supplier liek Travis Perkins. Much cheaper, and you can haggle. :)

Paul
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Re: Creating a false ceiling as a huge bass trap?!?

Postby new sonic arts » Mon Nov 29, 2004 7:52 pm

how are you guys attaching the rockwool to the ceiling? i want to do this but trying to think of ways to do it with minimal drill holes (its rented accomodation...)
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Re: Creating a false ceiling as a huge bass trap?!?

Postby Scott R. Foster » Mon Nov 29, 2004 9:11 pm

A standard ceiling tile grid is not very expensive - space the grid to match your mineral fiber panels and you have a drop in solution.

You may need to add some track lighting.

When you move you might pack your mineral fiber to resue, and install standard ceiling tiles, leaving the grid and track lighting in place... nothing to patch.
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Re: Creating a false ceiling as a huge bass trap?!?

Postby new sonic arts » Mon Nov 29, 2004 9:44 pm

thats an idea...! but i think i might have to go for something even less destructive, as i think i might not even be allowed to put up a ceiling grid.

so i think i will construct a series of slats along the walls which will support horizontal joists running parallel to the ceiling - which will support the bass trap. im pretty handy with timber so this shouldnt be too difficult.

this allows me flexibility in placing the exact height of the bass trap. so ideally how much space do i need between the ceiling and the rockwool? and what is best to cover the rockwool - plywood, or some kind of soft fabric?

in addition to setting up the ceiling, i also plan to add bass traps in the corners, and then i guess stick a few other absorbers on the walls. (hopefully it wont be neccesary to completley cover the walls?)

this is a basement studio by the way - just in case that has anything to do with the price of cheese :)

thanks for all your help - really appreciated!!!
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Re: Creating a false ceiling as a huge bass trap?!?

Postby Scott R. Foster » Tue Nov 30, 2004 1:01 am

How is the exisitng ceiling finished?

Is their a ceiling light fixture?

The thicker the better.

If you cover the mineral fiber with a diaphragm [plywood, plastic, paper or otherwise] you will in effect "tune" the device the resonances of the panel / membrane. Better to build a broadband absorber of nice thick panels and achieve a flatter absorption curve.

Also for a given panel thickness, a bit of an air gap behind will boost effectiveness... but filling the available space with mineral wool of the appropriate density would make for a better trap.

How much space do you reckon you will have left to fill after erecting your frame?

You could do the ceiling treatment in sections [leave some ceiling untreated].

Good Luck
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Re: Creating a false ceiling as a huge bass trap?!?

Postby Paul Woodlock » Tue Nov 30, 2004 2:51 am

Hugh Robjohns wrote:Yes, the ceilning trap idea will help. Paul and I visited a domestic spare room studio in a recent Studio SOS article where the guys had done exactly this (only using dense foam instead of rockwool).

However, this approach doesn't address all the problems, and as Etahn has said, I would suggest efficient corner trapping is still an important aspect to do as well.


Greetings Hugh

If the wall to wall ceiling absorber is thick enough, it covers all Horizontal ( wall meets ceiling ) corners anyway, but yes, trapping the vertical corners too would be very beneficiall

The Studio SOS I referred to above hadn't installed any corner trapping, and although the level of bass in the room was far more consistent than it was without the ceiling trap, there was still some variation -- most significantly an incredible null in the bass response right in the centre of the room !

Hugh


Even with huge amounts of trapping, you'll never totally get rid of standing wave ( mode ) bumps in the freq. response at the listening postion. or indeed you'll never get rid of freq. response inconsitencies throughout the room either.

See Mark Edmonds Studio Build Diary His Room has 25% of the total room volume broadband absorbed. And it's in all the right places.

It sounds damn good in there despite his Mackie HR824s being the weak link in the monitoring chain ( yeuch! ). But... He still has modal innacurracies, and is consiering further absorption in the near future. And now he can hear how bad the 824's really are in a well treated room, he's going to uprade them ASAP too ;)



Here's what I'd do for starters.....

I'd build the false ceiling as low as possible. Bear in mind your room is nearly a cube!!! A cube, ( along with a sphere ) is one of the worst shaped rooms to have regarding standing waves. You're gonna need a lot of trapping

I'd then do a complete fill of rockwool around the perimeter above the false ceiling about 2 feet thick from the walls ( or maybe a bit more ) to cover Hoz corner trapping.

I'd then do a partial fill on half the false ceiling ( Inner area ) between the listening position and the speakers, to take care of the ceiling Early Reflections.

I'd leave the back half of the false ceiling without rockwool ( except for the perimeter, as mentioned above ), and used the rockwool saved to make some vertical corner traps.

Of course filling the whole void above the false celing is cool, but I feel some of the rockwool up there could be better employed as Vertical Corner Traps.

Of course if ya can afford it then fill the whole ceiling AND make broadband rockwool traps in all vertical corners :)

And don't forget Early reflection absoprtion too!! :) No good having a tight bass if the whole frequency range has a crap stereo image, crap clarity, and a comb filtered freqeuncy response due to Early Reflections.

Oh before I forget, and regarding false ceiling height...... As people don't usually stand up in the area between the listening position and the speakers( There's usually a workstation of some sort in the way ;) ), consider building a false ceiling that slopes towards the speakers from the listening position. This way you can get more absorption in the horizontal corner behind ( and above ) the speakers

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Re: Creating a false ceiling as a huge bass trap?!?

Postby Paul Woodlock » Tue Nov 30, 2004 3:12 am

James Walker-Hall wrote:....

in addition to setting up the ceiling, i also plan to add bass traps in the corners,


Cool. Make 'em as big as possible, bearing in mind your 'near cube' room.


and then i guess stick a few other absorbers on the walls. ( hopefully it wont be neccesary to completley cover the walls?)
.....

Well the early reflection rule of thumb would mean you should cover all walls, but it might not be necessary.

Early reflections are those that arrive at the ear within around 20ms of the direct sound. And are percieved by the ear as being part of the direct sound, instead of discrete reflections.

When the direct and refelcted sound combine at the ear, and cause frequency depenent colouration of the direct sound.

Sound travels roughly 1 foot per millisecond in air, so......

Any reflection path length that is less than 20 feet longer than the direct sound path length will cause an EARLY Reflection.


The easiest way to find the areas os reflection that affect the listening position is to use the mirror trick.... it's easy....

1] Sit in the listening position

2] Get a friend to move a mirror around all surfaces of the room

3] Wherever you can see a speaker(s) is where you need to place absorptive panels to, erm, absorb the early reflections. Absorption efficiency is also frequency dependent ( HF being easiest, LF being the hardest ), so the thicker the absorption ( and greater the air gap behind ) the better.

Early reflection control is usually done on the walls and ceiling between the listener and the speakers, but in very small rooms ( Like yours ), early reflections can will also come from the back wall. So don't be afraid to try absorbing the back wall too.

If all this makes the room a bit too dead/dull, then you can hide some mid/high diffusion panels under the cloth that covers your corner traps to give the room a bit of sparkle back. It's ALL experimentation at the very end of the day.

HTH :)


Paul
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Re: Creating a false ceiling as a huge bass trap?!?

Postby new sonic arts » Tue Nov 30, 2004 10:28 am

hi guys

this is all a great help. although i obviously wanna get it done asap, so i can get back to making music (and specifically take down some vocals that ive holding off for a few months) im definitely not going to rush into anything... ive waited long enough already so i plan to do it as best i can.

im moving into the flat this weekend, so what i will do is take some pics of the room, and make some measurements, and if its ok - post them here for some further advice.

i will also put up some sketches of what i mean for my timber framework, (which will serve to support my inner ceiling and soundproofing walls).

from what ive seen so far, and from your advice, i will probably use a load of rockwool as the main material (as i can get it locally from travis perkins ive discovered). if it will help, i certainly dont mind buying a few bits of more expensive stuff. this whole thing looks like its gonna be much cheaper than i expected (the cost to me is the good few evenings/weekends to construct).

i havent received the specs sheets yet for nidaplast, but im slightly dubious about it being effective for LF anyway, because from my laymans logic the honeycomb would have to have some very large cells to be be effective at the low end???

anyway, exciting stuff! i will be back... thanks again...!
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Re: Creating a false ceiling as a huge bass trap?!?

Postby Hugh Robjohns » Tue Nov 30, 2004 12:02 pm

Great contributions Paul. I'm sure everyone here will find your suggestions useful. However, can I gently suggest a little more moderation when it comes to some of the other comments:

Paul Woodlock wrote: And now he can hear how bad the 824's really are in a well treated room, he's going to uprade them ASAP too ;)

I know there's a smiley face there, but this is hardly a constructive or objective comment, and is likely to cause an unwarranted degree of unrest in several quarters.

If you happen not to like the performance of the HR824s, that's fine. If your budget allows you (or your friends) to purchase far more accurate (and more expensive) monitors, that's fine too.

However, I think most would agree that for the money the HR824s offer a very respectable performance compared to the immediate competition. Sure, if compared to serious high-end three-way active systems the 824s exhibit deficiencies. But it's all a matter of perspective and budgetry restrictions -- compared to lower budget monitors the Mackie HR824s represent a significant boost in quality, and since people tend to upgrade in stages over time, this is a far more relevant point.

I'm not a Mackie user and I'm not trying to wave a banner in favour of Mackie. These comments could apply equally to many other monitors. However, I don't think it fair to castigate a product in this way without making it clear that it is a personal and subjective opinion, and in an appropriate context.

hugh
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Re: Creating a false ceiling as a huge bass trap?!?

Postby Scott R. Foster » Tue Nov 30, 2004 1:20 pm

Hugh:

Ya Paul's a snob!

;)

I use the Mackie's and with the addition of a sub I find them quite workable. I added one of these to the system and am pretty happy with em ever since.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=300-762

Of course if Paul would like to send me his monitors for an extended season of destructive testing, I am ready to be proved wrong.
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