Speaker shopping S.O.S guide

Chris' Acoustic Blog

I often find my friends contacting me with a link to an audio product with the question “is this good?” or “should I get this one or this one?” So here I am going to go into the basics of speaker and amplifier specifications.

Firstly: Think about what you actually need. Smaller rooms will only need small bookshelf (or ‘stand mount’) speaker sets. These speakers are small but still very capable of delivering lots of musical goodness to your ears. Due to their size they may require a sub-woofer to help with films and bassy music.

Floor standing speaker sets are larger and can often outperform the bookshelf systems (more on that later). These speakers are often used in living rooms, either for music or as the front channels in a home cinema system (see my other post about surround sound systems).

The Speakers:

Right, now that you know roughly what…

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Why you should spend more than £20 on headphones…

Last night I horrified my girlfriend. Her head whipped round to face me, her eyes ablaze as she looked at me and roared “HOW MUCH!?!” I had made the fatal mistake of telling her how much my headphones cost. To me £60 is a completely reasonable price to pay for some magical sound-devices that go inside your ear, however many people my age do not share this view.

Many of my friends also do not understand why I spend so much more than them on audio equipment… That it until I let them play their favourite tracks and listen properly…to which they say sounds “depressingly beautiful” as they realise they will go home and be forever disappointed with their cheap sets!

So whats wrong with a set costing £10? when you press play…you hear the singer…you hear the guitar.. you hear a little bit of other stuff…what could be wrong?

everything!

that’s right, everything about them sounds wrong! listen very carefully… does the band sound like they are in the room with you? NO! Can you count how many people are harmonising together? NO! do guitars sound like actual guitars? NO!  These are just a few things that are missing from your audio… There will be many subtle parts to your favourite tracks you aren’t even hearing! hard to believe perhaps, but I’ve sat a friend down in front of my speakers to listen to tracks of his choice(Papa roach… red hot chili’s and Jeff Wayne’s war of the worlds). He cannot hear 100% well and was convinced high quality audio would be wasted on him. 10 minutes later I asked him how things sounded and his response was;

“depressingly beautiful”.

why would he say that? because he knew he had to go home and listen to the same tracks on his crackly £5 apple earphones, now that he had seen the light.

So the moral of my rant is… that If you are wondering about upgrading your headphones, you will never go back!

 

 

Speaker shopping S.O.S guide

I often find my friends contacting me with a link to an audio product with the question “is this good?” or “should I get this one or this one?” So here I am going to go into the basics of speaker and amplifier specifications.

Firstly: Think about what you actually need. Smaller rooms will only need small bookshelf (or ‘stand mount’) speaker sets. These speakers are small but still very capable of delivering lots of musical goodness to your ears. Due to their size they may require a sub-woofer to help with films and bassy music.

Floor standing speaker sets are larger and can often outperform the bookshelf systems (more on that later). These speakers are often used in living rooms, either for music or as the front channels in a home cinema system (see my other post about surround sound systems).

The Speakers:

Right, now that you know roughly what you are wanting, here is a breakdown of the specs you will need to know about:

  • Frequency Drop-off (a.k.a. frequency response or f3) is a term used to describe when a system is getting noticeably quieter at a certain frequency. Taking about the low end drop off (this means bass!) The speakers will continue to get quieter the further down in frequency you go. So in short: the lower the frequency drop off, the more bass you will be able to hear. Floorstanders usually provide a lower frequency drop off, so can deliver most of the action effectively on their own (unless your watching films loudly or want to shake windows).

*systems with a drop-off at 70Hz or more will benefit greatly from a sub-woofer.*

  • Sensitivity: this is how easily a speaker can be driven by an amp. a higher sensitivity is good as it will require less power to drive, so a smaller amplifier can  be used. (a sensitivity difference of 3dB will require DOUBLE the power from an amplifier to achieve the same volume)
  • Power rating. This a measurement, in watts, of the unit’s maximum power it can handle. There are sometimes two values, the maximum power for an instant in time and the RMS power. The latter being the important one!. This value should not be significantly higher than an amplifier’s power output in watts rms.

The Amplifier:

Amplifiers also have a scary page of strange numbers and symbols. the two key specs of an amp are its signal to noise ratio and its power.

  • Power, is the measurement, in watts, that the amplifier can provide a speaker. If the speaker have a  power rating of 50w rms, and the amplifier has an output of 10w rms, the amp may struggle to provide a high volume from that speaker. So you will turn it up more…this will cause distortion and you risk blowing your precious new boxes of sound, so choose amplifiers with a similar or higher power output. (amplifiers with a much higher output will very easily drive the speakers, however turning them up can very easily damage the speakers).
  • Signal to Noise ratio….or S/N means how much of the sound coming out the amp is music in comparison to hissing. All amplifiers make a teeny bit of noise, but it is usually too quiet to hear over the music…UNLESS the signal to noise ratio is low, then you may hear hissing on come tracks or quiet parts in songs. Number crunching… 70dB is typically a very low(cheap) S/N ration, whilst slightly more expensive units will achieve closer to 90dB.

Surround Sound at home

I recently went over to a friend’s house to view the new home cinema system the family had bought. It was time for a film. With the curtains drawn and the lights off, ‘Batman: The dark knight’ was fired up in the dvd player and everything was set into motion. As the explosions, car chases and satanic voices filled the room however, something was not right. all the voices seemed to be coming from my right, and anything slightly boomy managed to rattle everything in the room! I began to scan the room to see where the speakers where placed and it all started to make sense. The speakers had been crammed into the most awkward and alarming places! So I decided to investigate…

 

A 5.1 surround sound system comprises of 5 speakers and a sub-woofer. The 5 speakers are designed to handle the mid and high frequencies whilst all of the low frequency material such as explosions is sent to the sub-woofer.

The 5 channels…

the 5 ‘smaller’ speakers are the left, centre, right, rear left and rear right channels. If these are placed in a room correctly, they will be able to work with each other to provide a complete surround sound experience to listeners positioned in the centre of their arrangement. Of course not many houses have sofas in the middle o the living room, but it is still beneficial to set them up that way. Above are the correct angles of placement for the channels. The front speakers should be positioned around 30 degrees to each side of the listening position, with the rear channels around 110 degrees each side.

The sub is a different story… since low frequencies are not very directional, and humans find it very hard to localise low frequency sounds. So the sub should be able to be placed anywhere, in whatever direction right? NO! If the sub is placed close to any boundaries (walls and the floor), the sound produced will reflect off, complimenting the original sound as if a second source was in the room (this is an image source, created at an equal distance ‘into’ the boundary to where the sub is placed)

1 boundary (floor) gives a 3dB increase to bass volume

2 boundaries (floor and 1 wall) gives 6dB increase to things boing bang and boom.

3 boundaries (in the corner of a room) will give a 9dB increase to the original sub’s output, resulting in a very muddy sound.

These increases to bass might look like a good idea, but they don’t SOUND like a good idea! with a single sub-woofer, room modes will create some very interesting phenomena. Standing waves will occur and the volume of the bass will change depending on there you are in the room! so the guy sitting next to you might be hiding for cover while you don’t even feel a rumble. The best thing to do, is try to avoid placing the sub near walls, and if you have to… put the sub at different distances from each wall. (for example in the corner of a room… 10cm from the back wall and 22 from the side wall).

 

So there you have it, if you have a home cinema 5.1 system, try to space the channels out symmetrically from you, and if you find there is too much bass then move the sub away from the wall.

 

 

references:

http://www.audioholics.com