Dear Forum, I have a home studio that I use for doing sound design for theatre, mixing acoustic theatre (theatrical installations and radio drama) and composing electro-acoustic music. I'm gradually diminishing the reverb in the room and I'd like some advice please on further steps I can take on a low budget (we renovated this house recently so I'm doing things slowly!).
The room has the dimensions: 480 x 350 x 250cm (15.74 x 11.48 x 8.2 feet). My monitors are Tannoy System 12 DMT IIs, a mid-field system. The dual concentric cones of these are placed 2m apart at ear-height with more than a metre away from the rear wall (the 350cm length) and slightly less from the side walls - I used a golden mean ratio - and they sound good where they are now, after having tries various positions in the room.
Behind the speakers is a large double doorway of glass (which can be folded away) and wooden shutters (Venetian style) which are generally exposed when I work. There's another glass/shutter window, a recessed doorway, hardwood floor, flat plaster ceiling and parallel plaster walls
Carpet is a bit of luxury item here in Brazil and I've managed to cover probably about 70% with rugs. I have 3 fairly lightweight foam mattresses placed on the walls to the sides and behind the listening position as a temporary measure.
At present, if clap my hands, I estimate the reverb time to be one second. I'd like to reduce this and I wonder what an ideal reverb time would be?
Right now I have the opportunity to buy acoustic wall panels left over from the refurbishment of a cinema. I don't their specifications yet nor the price, but wonder what sort of of wall coverage forum members would recommend? ie. what percentage - and where.
I'm not trying to isolate the sound, just improve the internal acoustics. I don't have a acoustic testing mic, but I can afford a Behringer if necessary. I have a sound meter though and software to play pink-noise, sine-sweeps etc.
Thanks!
Comments
"One thing is clear - you've got a less than developed idea of w
"One thing is clear - you've got a less than developed idea of what sound treatment is and does"
Thank you for pointing that out, that's why I'm here, but I have to say that for want of anything better the carpet and mattresses help significantly. I'll have a look for the book, thanks for the suggestion. Yes, the walls are parallel and do give a nasty echo especially without any furnishings. I mentioned the acoustic panels from the cinema that are available, do you have any recommendations on where I can place these and how many square metres I might need?
+ 1 on Rod's book Surdo, post: 424154, member: 47791 wrote: Car
+ 1 on Rod's book
Surdo, post: 424154, member: 47791 wrote: Carpet is a bit of luxury item here in Brazil and I've managed to cover probably about 70% with rugs. I have 3 fairly lightweight foam mattresses placed on the walls to the sides and behind the listening position as a temporary measure.
As Paulears said, every material affect the sound differently, the worst thing you could do is improvise and create problems.
Foam mattresses are not the same as acoustic foam. Acoustic foams have regular cell structure and accurate control of the cell size, higher air flow resistance, and therefore better acoustical absorption.
Other than absorbtion, you can go a long way with diffusion. Having a bookshelf in the room with uneven stuff on it will break a good part of room echo without taming random requencies.
Anyway read some theory before you invest. You will save some deceptions.
I did say "temporary measure" - but I'm sorry I mentioned the ma
I did say "temporary measure" - but I'm sorry I mentioned the mattresses... a red rag to a bull it seems. The shutters at the front and on the window act as good diffusers and a diffuser on the two side parallel walls is probably a good idea. But again, any opinion on on the acoustic panels and where I can put 'em.
Home recording studio acoustic treament
Some things that will help; home-recording-studio-acoustic-treatment
Thanks Space. My room is similar to the model in the link you se
Thanks Space. My room is similar to the model in the link you sent. If I place bass traps, they would have to be at the front-right and at the left-rear due to a window and the main doorway (not the double doors). I'm not sure if diagonal bass traps will cause any problems. An overhead cloud is possible as are two lateral broadband absorbers. Here is a photo of the room:
The snag with using cinema size products is that they were proba
The snag with using cinema size products is that they were probably built to tame the problems that space had, so if they are designed to 'suck out' certain resonant frequencies the room enhances, then the chances that you want the same are slim. On the other had they could be broadband products - but unless you can pull them apart and work out what they are designed to do, the best you can do is flood some pink noise into the room and measure the before and after response to see what they do - they could be good for you, or the reverse.
I had a pair of the Tannoys, the 15" ones, and I really loved them - BUT - they do have a rather specific sound, but if you like it, as I did, they're rather nice because the sound doesn't change very much as you stand up, which most conventional ones do. You're probably getting quite a lot of reflection back to those doors from the monitor - it's rather close to the speakers. what is on the wall where the camera is?
wow! that's a crazy hard room and an awful lot of speaker for it
wow! that's a crazy hard room and an awful lot of speaker for it. the shutters aren't going to diffuse as much as you think. you need mass and depth for a true diffuser. get some sheets of ridgid fiberglass and put them on the walls in the corners. look up superchunks. what' is on the back wall?
Excellent video Marco. This guy is right on. Okay, I have Real
Excellent video Marco. This guy is right on.
Okay, I have Real Traps and there are some differences. Lets find out if they matter?
Mine are 4 inches thick and have open slots all the way around the traps. They are excellent and look great and I do hang them off the wall so the waves get behind them. Real Traps are made of thin, well designed metal which may be lighter than wood.
They are costly compared but who cares if these work. Or, I don't mind paying more for and improved product.
I am an excellent builder, and plan on adding another 20 for my next room.
Here are the things I do wonder about.
Poplar from this area twists pretty extremely so just saying... But, its strong and will hold up if it doesn't start going wonky.
Maybe Ethan or Space knows how important RealTraps perforated sides are? Real Traps have slots cut all the way around them so Im assuming, the sound disperses?
Until the expert gets here... absorptive bass traps are basical
Until the expert gets here... absorptive bass traps are basically the same as broad band traps, but made thicker to extend to lower frequencies. Tuned traps are tuned by their geometry to operate at a specific frequency, and drop off in effectiveness as frequencies get further from the tuned frequency.
How to make base traps
Thanks for the links. I'll watch the videos now. Posting here some info on locally available materials:
Still waiting on information on the cinema material and I'm also trying to find a local equivalent to the "Owens Corning 703" fibreglass wads (importing is not usually a viable option due to high taxes - usually 100% - and delays), but here are some options that are available for acoustic foam:
1. This one is typical of the acoustic foam available here. 26Kg/m3 at R$25 per square metre. 35mm thick when "open" and 45mm when "closed", which I assume means 2 panels back-to-back.
2. A made-to-order cloth-covered material with a choice of colours and easily mountable from top. R$32 per square metre. I was interested in this, but looking further, the foam, "D33", seems to be used for mattress construction:
3. Bass traps made of "Lã de Rocha" - which I believe translates to "rockwool". Cloth covered wedges, 144Kg/m3, with the dimensions (faces of the wedge) of 80cm X 43cm X 32cm. Pricey at R$240 per unit.
4. I found this rockwool manufacturer in São Paulo that has a site in English. See the products link. I don't know if they sell direct to the public but perhaps this might be a cheap option for bass traps or broadband absorbers?
Cloth-covered fibreglass panels with acoustic absorption coeffic
Cloth-covered fibreglass panels with acoustic absorption coefficient data (see towards the bottom of the page "Performance Acústica"). Looks good between 500Hz and 4kHz - I guess this would constitute "broadband"? Have requested a quote:
Another bass trap with some acoustic data - R$510 for 4 X 61cm w
Another bass trap with some acoustic data - R$510 for 4 X 61cm wedges:
This company sells DIY panel frames and full panels. They also d
This company sells DIY panel frames and full panels. They also do room acoustic analysis for 50-70 $
http://www.readyacoustics.com/products/do-it-yourself-acoustic-panel-parts/chameleon-acoustic-frames/chameleon-c2-high-frequency-noise-absorption-panel-frames-do-it-yourself.html
Never tryied them, just a google find ;)
Their corner nest seems interesting : 
i did some research and i was wrong about absorbers. they are ba
i did some research and i was wrong about absorbers. they are bass traps as well.
i found http://en.wikipedia… this info without the hype.
lack of symmetry between speakers and listening position
Kurt Foster, post: 424167, member: 7836 wrote: wow! that's a crazy hard room...
And that is the biggest issue at this point. The lack of symmetry between speakers and listening position, the lack of absorption behind the speakers, the lightweight stands the speakers stand on...and all those hard surfaces. Including the window to the left which aborts symmetry and introduces leakage at low frequency.
The best thing you could do at this point, assuming you develop corner broadband and side wall absorption and an overhead cloud, would be to re-orient the equipment 180 degrees. That setting you have now is just not going to ever give you a good mix position.
Thanks a lot. I'll try re-orienting the equipment by 180 degrees
Thanks a lot. I'll try re-orienting the equipment by 180 degrees. The stands too in the future. Would stacked bricks be OK? There is that recessed door on the rear wall which won't help the symmetry any.
I got information on the acoustic panels that are available to me at good price (i hope) - they are fibreglass insulation panels - they are much the same as the panels in the following link with slightly different dimensions (50 X 50cm):
A detailed acoustic test is given here (see page 3 for a graph of the absorption coefficients): http://www.isover.c…
If someone could please comment on the efficacy of using these as broadband absorptive panels, I'd be very grateful. My other option will be to purchase acoustic foam.
They also have a big tub of "green glue compound" available, which I understand can be used to mount the panels: http://www.greenglu…
Cheers,
Space, post: 424243, member: 32398 wrote: The best thing you c
Space, post: 424243, member: 32398 wrote:
The best thing you could do at this point, assuming you develop corner broadband and side wall absorption and an overhead cloud, would be to re-orient the equipment 180 degrees. That setting you have now is just not going to ever give you a good mix position.
Space, I know you are the pro here.. but I don't get this one. If he turns 180degree, the wall behind his speakers won't be even because of the space going to the door. Please educate me on how this is going to be better..
Surdo, post: 424270, member: 47791 wrote: Thanks a lot. I'll try
Surdo, post: 424270, member: 47791 wrote: Thanks a lot. I'll try re-orienting the equipment by 180 degrees. The stands too in the future. Would stacked bricks be OK? There is that recessed door on the rear wall which won't help the symmetry any.
I got information on the acoustic panels that are available to me at good price (i hope) - they are fibreglass insulation panels - they are much the same as the panels in the following link with slightly different dimensions (50 X 50cm):
A detailed acoustic test is given here (see page 3 for a graph of the absorption coefficients): http://www.isover.c…
If someone could please comment on the efficacy of using these as broadband absorptive panels, I'd be very grateful. My other option will be to purchase acoustic foam.
They also have a big tub of "green glue compound" available, which I understand can be used to mount the panels: http://www.greenglu…
Cheers,
I don't speak Portuguese, but from what I can tell this looks to be typical of 25 mm (1") thick absorptive panels. They're useful as 'broadband absorbers' in the midrange to high frequencies, but quickly fall off below 500 Hz. 25 mm material isn't effective for low frequencies, but using multiple layers per panel and spacing the panels from the wall will increase absorption in the low end.
Green Glue is a damping compound used in construction for 'soundproofing.' It isn't useful in acoustically treating rooms.
pcrecord, post: 424271, member: 46460 wrote: Space, I know you a
pcrecord, post: 424271, member: 46460 wrote: Space, I know you are the pro here.. but I don't get this one. If he turns 180degree, the wall behind his speakers won't be even because of the space going to the door. Please educate me on how this is going to be better..
The problem with this room is that it has many areas that leak. In the current configuration, the window to the left and the open door bi-fold area are at a point that should be a hard boundary with some absorption to reduce early reflections PLUS low frequency absorption in the front corners.
Even if he did that, the window destroys the required symmetry and adds an acoustical hole that will not be matched on the opposite side and the bi-fold does not, as Kurt stated, add any diffusion especially at this close a range so it is the worse of two evils.
To rearrange the equipment 180 degrees gains the hard boundaries back on both the side and behind the speaker walls while reducing the issues down to the door. The door can be massed up to match the existing wall areas and you now have an area that is better to start in then was the other end.
What you need the most in a mixing environment are:
Symmetry;
A balanced equilateral triangle for your speakers and head to fit in;
A mass laden stand for each speaker to over come vibrations introduced from either direction;
Absorption directly to the left and right of the listening position centered on the listeners ears;
An overhead cloud to reduce the early reflections;
Typically back wall low frequency absorption to once again stop early and multiple reflections and catch low frequency waves.
These are the basics. Differences in the room sheathing, dimensions and gear will put you into round two of the fight in the attempt to tame or eradicate intrusive rays and waves from the listening position.
Project Studio Design & Build with Sweetwater's Mitch Gallagher
pcrecord, post: 424175, member: 46460 wrote: Some ideas from Sweetwater rep :
Nice one Marco, I feel like I'm watching myself here. Mitch and I have an near identical approach right down the treatment, TV, piano upstairs, tracking acoustic G and vocals while using larger facilities for those bigger room requirements.
With the exception to my 2 DAW approach, a lot of the gear we use is the same. We share the same hybrid approach, "scaling down on some area's while up scaling quality".
I have a Large VocalBooth Amp enclosure in a corner room that I'll leave open when I can. Its packed with treatment.
My Studio is fitted with Real Traps etc..
It works excellent for me.
I'm even testing how the Apollo 16 integrates with my Neos and Dangerous Master.
Thanks for posting this one. (y)
Perhaps it didn't come out well in the photo, but there is a bal
Perhaps it didn't come out well in the photo, but there is a balanced triangle formed by the speakers and the listener position, however no, it's not exactly an equilateral triangle. It's slightly elongated: 210cm distance between the speaker axes and slightly more (225) between each speaker-face and the listener. This is done following the recommendations of Tannoy for the DMT Series speakers, where the speakers are also meant to be angled between 10 and 15 degrees off-axis (to "give the optimum spread of the HF information").
Re. absorption behind the speakers, when I can, those double doors are wide open, which forms a 100% absorptive panel at the rear (there's a marauding 5 month-old german shepherd puppy outside which is why it was closed when I took the photo).
Re. the side window, perhaps I can make a demountable rig with absorptive panels to cover the window, with a matching panel on the right. Would this help?
Not sure how the door recess can be "massed up", although I could potentially put a second solid-wood door to cover the door opening. The current door opens inwards towards the door cavity.
Re. speaker stands, I'll look into something done with bricks.
RealTraps bass traps are are broadband bass traps
audiokid, post: 424182, member: 1 wrote: I'm going to ask Ethan. Stand by...
:D
Thanks for the heads-up Chris. RealTraps bass traps are not tuned - they are "broadband bass traps" meaning they absorb mostly bass, but over a wide range of bass frequencies. They do use a membrane to increase LF absorption and decrease HF absorption, but it's not the same type of resonant membrane as the old-school tuned membrane traps in this article:
http://www.ethanwin… Build a Better Bass Trap
In a room that's only 15.74 x 11.48 x 8.2 feet the main problem is bass peaks and nulls and ringing, and early reflections. RT60 isn't as relevant, and isn't quite the correct metric anyway.
As for buying used panels from a cinema, that might be brilliant or a total waste of money. It depends on the thickness of the panels and what they're made of.
--Ethan
Thanks. The panels from the cinema are made of glass fibres - u
Thanks. The panels from the cinema are made of glass fibres - unfortunately the site describing them seems to be down at the moment (see links in message #27 above) but I think they are 25mm thick and from memory they have reasonable absorption between 500Hz and 4kHz. The Reverend Lucas above suggested doubling them up or mounting them away from the wall to improve low frequency absorption.
Surdo, post: 424293, member: 47791 wrote: Re....those double d
Surdo, post: 424293, member: 47791 wrote:
Re....those double doors are wide open, which forms a 100% absorptive panel at the rear (there's a marauding 5 month-old german shepherd puppy outside which is why it was closed when I took the photo).
It is a big hole where your music leaks out. Here is what we all try to attain. An area that captures ALL the sound. This requires hard boundaries. A louvered bifold is not a hard boundary it is a leakage area that will allow the music a path out of the room especially low frequency.
This means that you make poor mixing judgement errors in under or over compensating for this audible gain or loss.
At the listening position you want to capture all the sound. All the direct sound. In order to do this you have to create a contiguous area with hard boundaries that do not let any of the music out of this environment.
Surdo, post: 424293, member: 47791 wrote:
Re. the side window, perhaps I can make a demountable rig with absorptive panels to cover the window, with a matching panel on the right. Would this help?
You can develop a window plug that matches the same mass as the exterior assembly on the outside and matches the interior sheathing on the inside and plug that window. That will essentially remove that path. But you still have to deal with the actual 4 foot wide by 80 inch hole that the light weight bifold door introduces.
Now, you are free to do as your situation might seem to suggest, but the leakage at the existing end you are using is going to cost more in trying to match it up to the opposite end.
And...after re-orientating 180 degrees you get the added benefit of having a path for lower frequency waves to escape by having that bifold door way behind you.
OK, but getting back to the door cavity. When the speakers etc a
OK, but getting back to the door cavity. When the speakers etc are rotated by 180 degrees, the left speaker will have a big hole behind it. The door, there at the back of the cavity, is not even solid board, but that can be fixed. And I can potentially install a second solid wood door to enclose the hole. That's the best I can think of.
I did once try putting the speakers along the longer side of the room, on the side with no window, but it sounded terrible - very boomy.
correct me if I'm wrong here, but doesn't an open doorway or win
correct me if I'm wrong here, but doesn't an open doorway or window provide 1 Sabin of low frequency absorption/dissipation? In short, is it not in fact acting like a gigantic bass trap, and could it not skew the bajeezus out of the acoustic fingerprint of your room?
Sabin as Unit of Sound Absorption
The unit of sound absorption is square meter, referring to the area of open window. This unit stems from the fact that sound energy traveling toward an open window in a room will not be reflected at all, but completely disappear in the open air outside. The effect would be the same if the open window would be replaced with 100 % absorbing material of the same dimensions.
source: http://acoustics-en…
Surdo, panels that are one inch thick (25 mm) are useful only fo
Surdo, panels that are one inch thick (25 mm) are useful only for reflection control. Even doubling them up won't do any good for corner bass traps. Now, stacking four of them adjacent would be fine.
Yes Donny, an opening to the outdoors is a perfect bass trap. An opening indoors could be excellent or only so-so, depending on what's beyond. But generally an opening is a Good Thing if it's in a useful place.
--Ethan
I'd seriously suggest Rod Gervais' book - Home recording studio,
I'd seriously suggest Rod Gervais' book - Home recording studio, which will show you quite clearly how to make the gizmos you need, but a few things come to mind. However, a couple of things come to mind straight away. You have 1 second reverb time, when you clap. Many churches don't have that much! So what is probably happening is the unpleasant reflections that come from multiple parallel surfaces. One thing is clear - you've got a less than developed idea of what sound treatment is and does. Carpet is pretty rubbish, and blankets and mattresses just soak up the very top end, leaving the medium and low frequencies to go straight through and reflect back. In Rod's book he explains how to identify and fix lots of room problems. Absorbers and traps are devices that will 'soak up' particular frequencies and diffusers are different devices to reflect sound in multiple directions. Some are wide band devices, others are tuned to soak up specific problem frequencies. Some big and chunky things, others foam of various depths. They all do different things and help cure different problems. All the carpet, blankets egg boxes and other stuff won't cure a rotten sound outside of their capabilities. Simple stuff like acoustic foam comes in various depths to do different things. In my studio, there's just one little area where reflections from the glass created a strange 'tinniness' if you stick a mic half way between the window and the wall - which ironically is exactly the best physical place for the mic! Just a couple of 50mm foam tiles cure this one, but in my edit suite, to do any recording, as a spill over space I have to be careful because it's boomy at the bottom end - and at some point I will get round this and put some treatment in. At the moment, audio recorded in there is bass light, unless I compensate.
Have a Google for some of these gizmos, but if you can work with wood, get the book, and build some of the designs in it.