Chris's Blog

Living Room Acoustics for Beginners

2011-08-22T16:46:00.001+01:00

I would like to start by saying that although I have some knowledge on this subject I am by no means an expert. I covered acoustics whilst at Uni but in a very specific way, aimed purely at room acoustics and recording studios. There is much more to this ‘dark art’ than what I covered, however I do know enough to write this article.

I write this because in my line of work I come across people who claim to know about acoustics, room treatments and in particular how to make a cinema “sound good”. I aim to dispel some of the myths and give a simple guide to ways in which you can go about improving the acoustics of you living room to suite a surround sound system or hi-fi.

So, lets start at the beginning.

How does sound behave in my Living Room?

To answer this we need to consider the room its self and what we have in that room. We of course have four walls, each of which will reflect sound. Very simply two parallel walls reflect low frequencies, these are known as Axial Modes, and are the most powerful and troublesome echos we have to deal with.

The simplest solution is to have no parallel surfaces, however we all know in our living room this is impossible. The ceiling and the floor will always be parallel even if the walls are not. The next best thing is absorption, acoustic specialists will tell you to invest in “bass bins”. They are absolutely right technically, but this is your living room not a recording studio, the best this to do is add as many soft furnishings as possible, no leather sofas, plush deep carpets, heavy curtains big cushions etc. This will be no means cure the problem, but it will help.

Sound does not just bounce in one direction, it can bounce of at angles. If the sound remains on one plane, i.e. x or y or z then we say these are Tangential Modes. These are made up predominantly by mid frequencies.

If the sound bounces randomly across all planes, i.e. x, y and z then we say they are Oblique Modes and are generally high frequencies.

This is of course highly simplified, but the principle will ring true. The best way to deal with the frequencies bouncing around that we don’t want is absorption, things like canvas paintings are good for mid frequencies as are light curtains, blinds and even fabric wall paper. The other option is to use diffusers, these scatter the Tangential Modes into the least problematic Oblique Modes, some diffusers can be make to look quite nice. If you want to go down the diffuser route, hunt around but don’t forget, you still want your living room to look homey or your wife will kill you!

I wouldn’t worry too much about Oblique Modes as they scatter and die out very quickly.

The next question to ask is; does it make a difference where I put my speakers?

The short answer is yes. The long answer is it depends on what speakers you have and what you hope to achieve.

If you are looking at setting out your Surround Sound have a read of one of my previous posts How to Setup Your Surround Sound. If you are setting up a Hi-fi or are creating a listening environment then you need to place your speakers at about ear height and 30 - 40 degrees apart as viewed from the desired sweet spot. You should also bring them away from the wall slightly as if they are too close you get something called comb filtering (for the super geeks follow this link to Wikipedia). The best way to check if you have got it right is to have a listen, if the music sounds muddy move the speakers further from the wall. Another tip is if your speakers sound a little weak in the bass area to put them in corners as this will give a 3dB lift to bass frequencies. If the speakers have a port you can also experiment with putting different kinds of foam in the port, this will change the way air flows in and out and consequently how the speakers respond to bass.

As far as setting up the room goes that’s it! Remember to listed to your work and save using your EQ for minor tweaks.

How to Setup Your Surround Sound

2010-12-03T16:31:00.002Z

We’ve all been there, having just bought an all-in-one DVD/Blu-ray with surround sound, complete with speakers, got it home all excited and can’t wait to get it going. Most of us will have just spent a few hundred or even a few thousand pounds on our new exciting purchase, but how do we get the most out of it?

The first thing is to take things slow, don’t rush into anything, make a cup of tea and get out the instructions. Yes guys I know, instructions are for losers, but trust me, if you new system has a handy button for setting up the surround sound you’ll want to know about it.

Once we’re au fait with our new systems features we can start to consider our setup. I’m sure we are all aware that a surround sound system has three front speakers, two rear speakers and a sub woofer, though some may have a pair of side speakers as well. Before we consider placing our speakers we must first consider the room in which they are going. Where do we want the “sweet spot” to be? Will the system be setup around the room or will the room be set be around the TV? For best results I recommend setting the room up around the system.

Now to business...

First lets consider the fronts, assuming that the television is all setup (I recommend 1400mm from floor to screen center by the way) we can place the center speaker. When placing speakers be aware that for best results the tweeters should be at about ear height when seated, generally this will be about 1400mm from the floor (see how that matches the TV?).

The center speaker is where the dialogue comes from and so should be unobstructed or speech will sound muffled. Place this either above or below the screen, this can be hard up against the edge of the screen or a little distance away, but remember if it is too far from the screen then it won’t sound like the actors are talking from the screen but from somewhere else.

Now lets look at the front left and front right speakers, these create the stereo effect. They play a small amount of dialogue, but predominantly are for sound effects. As with setting up any stereo system these should be about 30 - 40 degrees from the center speaker measured from the sweet spot, the further they are placed from the sweet spot the further apart they will need to be. You may wish to adjust the angle of these to get a clear sound at the sweet spot, generally pointing the tweeter towards the sweet spot will achieve this.

Now the rears, these create the surround effect and are only rarely heard. The thing to consider here is that you want the sound to wash behind you, in other words fill the space behind the sweet spot with a wide stereo effect. These can be placed at about 100 - 120 degrees measured from the sweet spot when facing the screen, pointing the tweeters at the back of the persons head. Di-pole speakers are ideal as surround sound rears, however these rarely come in the kits. Mounting a conventional speaker on the ceiling just behind the listening position can create a similar effect, though not many of us will go to that extreme.

The Sub woofer fills in the low frequencies that the surround speakers cannot produce. Sub frequencies are omnidirectional and so it is not hugely important where the sub is placed. Some will tell you to be wary of null points, though for most of us this isn’t a huge issue. The human ear can her frequencies as low as approximately 20Hz, as this has a wavelength of 17m it is unlikely that most of us are going to fit this in our living rooms. However this can still be heard as we feel the vibrations created at these low frequencies, this is called psychoacoustics and we can use this to our advantage. If the sub is placed say under a seat or downward firing then less volume is required for us to hear these sub-frequencies as we will feel them more readily. This has the added advantage of not pissing off the neighbours.

Finally the sides, if you have these in your system i.e. 7.1 they go parallel with the ears of the person sitting in the sweet spot.

Think we’re done? Not quite!

Now we have to set up the levels (relative volume of each speaker) and if possible distances. Setting the distances is easy, measure from each speaker to the sweet spot and put in the values, this helps prevent sound cancellation. When setting levels you will want the centre speaker to be slightly louder than the left and right so that dialogue will be clear, also the rears and sides will want to be a little quieter than the fronts so that they can be heard but are not distracting. The best way to get this all sounding great is to put on a film that you love with lots of surround sound action in and experiment. Personally I do not recommend boosting (amplifying) any speaker channel by more than 3dB, if a speaker is too quiet turn the others down to suit rather than turning the quiet one up. This will help to improve audio quality as sound will distort less as the volume is turned up.

Multi-room Audio on a Budget

2010-10-15T13:03:00.003+01:00

Before I launch into this one I should explain a little about what multi-room audio is forgive me if this seems a little obvious but we should all be on the same page to start. Multi-room audio is the ability to listen to a single source or group of sources in multiple rooms in the house at the same time. That is to say one radio can be listened to from speakers in several different rooms, not having a radio in each room.

Believe it or not multi-room audio is nothing new, systems have been around for at least 25 years with the earliest having push buttons to switch between sources and a volume knob on each control panel. These were in the days before you could remotely control devices so to change radio stations you would have to switch between different radios permanently set on a station. Thankfully times have moved on and you can get systems that are easy to use and can control devices with that all important feedback, i.e. display track/station names fairly cheaply.

So lets say that I’ve decided to get a Multi-room audio system, I have four rooms that I want to hook up, I want to have an iPod dock, DAB/FM radio, play songs from my iTunes library and maybe Internet radio as well, where do I go from here?

First you need to know what you really want, do you want an audiophile grade system or are you the kind of person that listens to their iPod through tiny headphones and are perfectly happy with that level or quality or are you somewhere in between?

Audiophiles; go to a professional and expect to spend around £30,000 or more for your system. Yes that sounds a lot, but you will have an incredible system. If this is you then stop reading this blog because you will probably hate everything else that I am going to suggest.

iPod with small headphone listeners; there are more options than what you can get from Curry’s/PC World/Play.com. Watch this space and pay attention.

In betweeners; you may want to spend a little more than what I’m going to suggest, the principle is the same, you will simply need better speakers, amps and possibly sources.

O.k. here goes...

Possibly the cheapest system that is even worth mentioning is Sonos. This is fairly low quality, though can be improved with better amps and speakers, but you get a lot of bang for you buck. You can have an iPod dock, play from you iTunes library and listen to Internet radio, which kind of makes DAB radio superfluous. Use Zone Player 120s and all you need do is plug in your speakers. Use Zone Player 90s and you can add you own amps and speakers and up the quality. This is very easy to install and you shouldn’t need a professional to get your system off the ground. The down side to this is, you can’t easily add you own sources. This system will cost around £600 - £700 per room.

The next step up will probably require some input from a professional and you would be looking at a system similar to NuVo. This offers multi-room audio that has all of the things that I spoke about in my brief above, iPod Dock, DAB/FM Radio, the ability to play from iTunes and Internet radio! All you need do is add speakers and you are away, though this requires cabling to be installed as well as a degree of programming so you will need professional help. This system would cost around £1,000 per room but offers better sound quality than the above system and the ability to add equipment of your choice, such as CD players, Turn Tables etc.

You can of course achieve a system similar to or the same as the NuVo one with systems such as Crestron, Control4 or AMX. However, unless your are in pursuit of audiophile sound quality or want to integrate anything other than music into the system, you cant really justify the added expense of these systems.

One final note...

If you are seeking the help of a professional with your system don’t ask them to install a complete Sonos system. By all means ask to have Sonos integrated but expect to be told that you would be better off with a different option. True professional will tell you this for the following reasons.

They can make very little money on Sonos, it is designed to be purchased and installed by the end user.
Sonos offers fairly low quality sound and those with a reputation to maintain will not want to stake their reputation on what Sonos has to offer.
Any wireless system will have reliability issues and most installers don't want to be hampered with constant call-outs.

Having said that, Sonos is an excellent option if you are on a budget and are happy to install the system yourself. It has a very simple interface, is easy to install and it does work very well. If you are having problems you can always add in a zone bridge and that usually sorts things out.

Apple’s iPad as a Home Control device

2010-10-01T18:25:00.008+01:00

Apples latest offering, the iPad, has achieved great acclaim. People love it, it’s easy to use and with the multitude of apps on offer, it can do virtually anything. As home automation technology becomes more available to the common man, is the iPad really the only control device you’ll need?

The iPad has many great features, not least the enormous and constantly growing library of apps. This sleek, cool device can be made to do virtually anything, and that, in the world of home automation may be it’s down fall. I am constantly being asked what I think of the iPad in the context of Home Automation or if I can control someones home with only an iPad. My answer is always the same, the iPad is great but first lets think about what you want to use it for. You may wish to subscribe to a paper and read it on the train every day, you might want to browse the Internet, play games, listen to music, watch movies and more. The iPad can do all of this and control you home, a truly fantastic device I think you’ll agree.

What happens then if you take you iPad on the train and someone left at home wants to watch TV? What if you have a Movie playing at full volume whilst you are browsing the Internet and the phone rings? What happens when the battery goes flat? All of this must be considered before choosing the iPad as a home control device. The simple answer is to have multiple iPads that are solely used as home control devices. That’s great but you’ve invested your money into a device that can do a great many things, then use it to a fraction of it’s capabilities.

My personal opinion is that the iPad should be used in conjunction with traditional home controllers. By all means choose the less feature rich, cheaper alternatives to the pricey touch screens. But remember that when you need to press mute quickly, switch the lights on early in the morning or use you door entry system simplicity is the key, and it doesn’t get more simple or reliable than a wired, solid push button. You’ve got all the great features of the iPad, now back them up with sensible, reliable and easy to use controllers.

Speeding up VBA Macros in Excel

2010-06-22T20:21:00.008+01:00

I have stumbled upon a good way to speed up macros in Excel. If you use the Application.ScreenUpdating = False argument at the beginning of the macro, then the macro will not display what it is doing. Then when you use the argument Application.ScreenUpdating = True at the end of the macro everything the macro has done will become visible. This works well in speeding up long and complex macros.

Problems with double sided printing in adobe acrobat pro

2010-06-22T20:21:00.007+01:00

In my office we were having a problem printing double sided a document with a mixture of portrait and landscape pages. The solution was to un check the "Auto rotate and centre" box. What this does is to automatically print portrait pages in portrait and landscape pages in landscape. When you un check the box you will need to set the paper up yourself and for any pages that are on a different orientation you will need to manually rotate or print separately. This cured the problem for me.

Highlight Duplicates in Excel 2003

2010-06-22T20:20:00.004+01:00

In Excel 2003 there isn't a way to highlight duplicate items so i have written this VBA script to do it for you, just copy and past the script below. You will need to sort the data before you can run this script. You can change the values in the colour argument to change the colour that the cells will be high lighted in.

Sub FindDuplicates()
'
' !!NOTE: You MUST select the FIRST cell in the column and
' make sure that the column is SORTED before running this macro!!
'
Application.ScreenUpdating = False

colour = RGB(255, 0, 0)
FirstItem = ActiveCell.Value
SecondItem = ActiveCell.Offset(1, 0).Value
Offsetcount = 1
Do While ActiveCell <> ""
If FirstItem = SecondItem Then
ActiveCell.Offset(Offsetcount, 0).Interior.Color = colour
Offsetcount = Offsetcount + 1
SecondItem = ActiveCell.Offset(Offsetcount, 0).Value
Else
ActiveCell.Offset(Offsetcount, 0).Select
FirstItem = ActiveCell.Value
SecondItem = ActiveCell.Offset(1, 0).Value
Offsetcount = 1
End If
Loop

ActiveCell.Offset(-1, 0).Select

FirstItem = ActiveCell.Value
SecondItem = ActiveCell.Offset(-1, 0).Value
Offsetcount = -1
Do While ActiveCell <> ""
If FirstItem = SecondItem Then
ActiveCell.Offset(Offsetcount, 0).Interior.Color = colour
Offsetcount = Offsetcount - 1
SecondItem = ActiveCell.Offset(Offsetcount, 0).Value
Else
ActiveCell.Offset(Offsetcount, 0).Select
FirstItem = ActiveCell.Value
SecondItem = ActiveCell.Offset(Offsetcount, 0).Value
Offsetcount = -1
End If
Loop

Application.ScreenUpdating = True

End Sub

This macro will process one column at a time and it will process the entire column.

Move a Sheet in Ecxel using VBA

2010-06-22T20:19:00.002+01:00

I recently found the need to make a little button that would copy an entire sheet from a template document into a target document the VBA code needed to simply select and copy a sheet is:

Sheets("sheet name").Select
Sheets("sheet name").Copy Before:=Workbooks("target workbook name").Sheets("sheet name")

Adobe InDesign 'Falure to PDF' error

2010-06-22T20:18:00.003+01:00

I have created a template in Adobe InDesign for a style of document that is used quite frequently. Recently the completed documents have started throwing up a 'Failure to PDF' error when exporting to PDF. As far as I can tell the reason this happens is due to the security features related to any PDFs linked into the document. The copyright security features prevent the document from creating a new PDF incorporating any PDFs in the document. The best way to solve this I have discovered is to change the PDF files into jpegs, a really easy way to do this is to download Virtual Image Printer from www.download.com, it's free and creates pretty good quality jpegs, the relink all of the PDF files to the new jpeg version you have created, this should solve the problem. More info can be found on the Adobe Forums.

Rendering Glass and other Transparent Materials in Indigo from Sketchup

2010-06-22T20:17:00.001+01:00

Lately I have been trying to render a few items that include some glass parts using the Indigo Render Engine. Every time I rendered the image the glass would come out black. I was using the Sketchup Background Black environment as i wanted to use my own light sources. By chance I tried to render the same image using the Sun and Sky environment and the glass magically became transparent. I have found that the preset glass material only works well with the Sun and Sky environment. If you want to use your own light source it's a bit more complicated.

First create a new colour that is the shade you want you glass to be, i.e. with a slight blue hint or tinted black etc. and make it a phong material (or use the car paint preset). Then create another new material, this one we will paint the surface with, make this a blend material and select the A material as none and the B material as you glass colour. you can adjust the transparency of the glass by changing the blend ratio of these materials (1 being opaque and 0 being completely transparent) i suggest a value of between 0.3 and 0.5 as this gives a good reflection and colour in the glass but maintains transparency.

Combining Cells in Excel

2010-06-22T20:16:00.003+01:00

A while back I was asked if there was a way to combine cells in Excel. The answer is there isn't, what you have to do is write a formula in the destination cell that reads '=A& &B& &C& &...' or you can use the 'Concentiate' function. Either way the cells that you want to combine must still exist as discreet cells you simply add an extra cell to combine the others together in.

Creating a Date Stamp in Excel

2010-06-22T20:15:00.001+01:00

Strictly speaking the date stamp in Excel is done by pressing Ctrl + ; however if you would like to place a date stamp automatically when data is entered into a specific cell the i find that the following formula works well.

=NOW()

This will place the current date and time e.g. 15/08/2008 13:57. The down side is that every time the sheet recalculates i.e. any time enter or return is pressed the date stamp is updated. The easiest way around this is to create a circular statement. For example if when data is entered in to cell A1 you want to place a date stamp in B1 then the following formula will work.

=IF(A1="","",IF(B1="",NOW(),B1))

However due to the circular reference which basically stop the cell recalculating an error will be returned. To stop this go to Tools>Option select the Calculation tab and tick the Iterations box. This will solve the circular reference problem.

Removing alert Messages in VBA

2010-06-22T20:14:00.004+01:00

I had written a VBA script that copied information from one workbook to another, every time the info was copies an alert popped up that had to be confirmed. This was tiresome to say the least, after much research and a little help form the Microsoft Forums writing the line

Application.DisplayAlert = False

just before the 'paste' command prevents this alert from popping up.

3D Wii

2010-06-22T20:13:00.001+01:00

I've just been show this awesome video of this guy who has basically reversed the Wii and turned it from being a 2D into a 3D device. Just check it out, you'll see what mean.
Wii Head Tracking