Sound wave cancellation:
It is often stated that the reason for using a baffle or an enclosure for a speaker driver is to 'prevent the cancellation of sound waves' from the front of the speaker.
Take for example a speaker vibrating at 90 Hz. The air pressure variations that make up the sound waves travel forwards from the front of the speaker and rearwards from the back of the speaker.
There is no way for these areas of low pressure to cancel each other out unless there is a reflection of the sound waves by the surrounding walls. Another possibility is the diffraction of the sound waves around the edges of the speaker which will cause interference and cause the speaker to sound less loud than it would if it was placed in an infinite baffle.
sound-waves-visualize-sound | POLITUSIC
With varying frequency sound such as music, it is hard to imagine the frequencies cancelling each out exactly, but it could cause a reduction in bass.
Actually this explains an effect I have come across in which a small 3 inch speaker held about 1 metre from the rear wall seems to ouput more bass as than when it is held against the wall. As the rear of the speaker approaches the wall, the bass effect collapses.
It is often stated that the reason for using a baffle or an enclosure for a speaker driver is to 'prevent the cancellation of sound waves' from the front of the speaker.
Take for example a speaker vibrating at 90 Hz. The air pressure variations that make up the sound waves travel forwards from the front of the speaker and rearwards from the back of the speaker.
There is no way for these areas of low pressure to cancel each other out unless there is a reflection of the sound waves by the surrounding walls. Another possibility is the diffraction of the sound waves around the edges of the speaker which will cause interference and cause the speaker to sound less loud than it would if it was placed in an infinite baffle.
sound-waves-visualize-sound | POLITUSIC
With varying frequency sound such as music, it is hard to imagine the frequencies cancelling each out exactly, but it could cause a reduction in bass.
Actually this explains an effect I have come across in which a small 3 inch speaker held about 1 metre from the rear wall seems to ouput more bass as than when it is held against the wall. As the rear of the speaker approaches the wall, the bass effect collapses.
The audio camer may illustrate the point:
http://www.umiacs.umd.edu/~odonovan/Audio_Camera/
Visualization
http://sploid.gizmodo.com/these-images-of-sound-waves-in-water-are-hypnotic-1759741538
https://mukeshbalani.wordpress.com/2015/02/16/crazy-photography-trick-lets-you-see-sound-waves/
This is what I was looking for:
http://www.appliancedesign.com/articles/94382-acoustic-analysis-and-appliances
See the 4th image from the left.
http://www.umiacs.umd.edu/~odonovan/Audio_Camera/
Visualization
http://sploid.gizmodo.com/these-images-of-sound-waves-in-water-are-hypnotic-1759741538
https://mukeshbalani.wordpress.com/2015/02/16/crazy-photography-trick-lets-you-see-sound-waves/
This is what I was looking for:
http://www.appliancedesign.com/articles/94382-acoustic-analysis-and-appliances
See the 4th image from the left.
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Useful Videos for understanding how speakers work
There are several videos I have found very useful for understanding how speakers work.
A few points fromt he videos:
- Trained and untrained listeners alike can pick out the better loud speakers from the not so good ones
- There is a set of speakers that is 'close to perfection' selling at 1800 per pair, whereas speakers selling for many times the price do not produce the same quality of sound.
-It is possible to realistically produce guitar and acoustic instruments with current speaker technology, but reproducing an orchestra's performance contues to be difficult to achieve.
- Bass performance is 30% of the speakers quality.
I am listing some of them here:
https://www.youtube.com/watch?v=zrpUDuUtxPM
https://www.youtube.com/watch?v=6NgkP8aABO4
https://www.youtube.com/watch?v=7vn6hQHRgzk
https://www.youtube.com/watch?v=9A_IchJbpCI
There are several videos I have found very useful for understanding how speakers work.
A few points fromt he videos:
- Trained and untrained listeners alike can pick out the better loud speakers from the not so good ones
- There is a set of speakers that is 'close to perfection' selling at 1800 per pair, whereas speakers selling for many times the price do not produce the same quality of sound.
-It is possible to realistically produce guitar and acoustic instruments with current speaker technology, but reproducing an orchestra's performance contues to be difficult to achieve.
- Bass performance is 30% of the speakers quality.
I am listing some of them here:
https://www.youtube.com/watch?v=zrpUDuUtxPM
https://www.youtube.com/watch?v=6NgkP8aABO4
https://www.youtube.com/watch?v=7vn6hQHRgzk
https://www.youtube.com/watch?v=9A_IchJbpCI
How Speaker Cabinets work - open baffle
How Speaker Cabinets work
Having covered the basics of how speaker drivers produce sound, it is time now to look at the basics of speaker cabinets, or enclosures.
The simplest form of enclosure is a sealed box. Simpler than this is the "open baffle" type of speaker, which consists of simply the front baffle with the speakers mounted on it.
A note about open baffles - I have experimented briefly with these, as they are simple to construct. I actually have a pair of open baffle speakers which I used in an on-wall configuration, which is, to say the least, not the place for them.
Using a much smaller speaker, tests I have performed have shown be that when the speaker is held about 1 metre from the wall, best bass performance is obtained.
Moving the speaker (driver) towards the wall highlights an interesting effect - the bass collapses and becomes 'thinner' and becomes almost non-existent.
It would seem that the open baffle speaker should be used at a specific distance from the rear walls, that being said, the open baffle did have a pleasing, clearer, uncluttered sound in my opinion.
Here is more information, much of it I have not read myself:
Introduction To The Art And Science Of Open Baffle Speaker Building Article By Darrel Hawthorne Of Hawthorne Audio
Designing Loudspeakers - Part 15 Open Baffles and Bass
Also see here:
Linkwitz Lab - Loudspeaker Design
How Speaker Cabinets work
Having covered the basics of how speaker drivers produce sound, it is time now to look at the basics of speaker cabinets, or enclosures.
The simplest form of enclosure is a sealed box. Simpler than this is the "open baffle" type of speaker, which consists of simply the front baffle with the speakers mounted on it.
A note about open baffles - I have experimented briefly with these, as they are simple to construct. I actually have a pair of open baffle speakers which I used in an on-wall configuration, which is, to say the least, not the place for them.
Using a much smaller speaker, tests I have performed have shown be that when the speaker is held about 1 metre from the wall, best bass performance is obtained.
Moving the speaker (driver) towards the wall highlights an interesting effect - the bass collapses and becomes 'thinner' and becomes almost non-existent.
It would seem that the open baffle speaker should be used at a specific distance from the rear walls, that being said, the open baffle did have a pleasing, clearer, uncluttered sound in my opinion.
Here is more information, much of it I have not read myself:
Introduction To The Art And Science Of Open Baffle Speaker Building Article By Darrel Hawthorne Of Hawthorne Audio
Designing Loudspeakers - Part 15 Open Baffles and Bass
Also see here:
Linkwitz Lab - Loudspeaker Design
Speaker Cabinets
I have built a few speaker cabinets so far, and athough they sounded better than the ones they replaced, some work needs to be done to obtain the maximum out of the drivers I have (PC speaker drivers)
What I have learned so far:
For the on- wall and near- wall applications, the closed or ported box peforms better than the open baffle version, at least at the speaker sizes (3 inch to 4 inch) that I have been trying out.
First trials with speaker drivers mounted in cardboard boxes a more or less ear level showed very encouraging results. The best amplifier I own, which happens to be a Pioneer 50W per chanell MOSFET driven seemingly noisless amplifier is used to aim music directly at my feet, and the other amplifier in use is used to drive two large Sony SS-333 speakers mounted on a high cabinet in the living room.
It can be said that I have not been enjoying direct music for much of the time, and wall mounted speakers were the only way to achieve this and preserve space.
Placing the speakers in cardboard boxes improved the sound vastly over the plastic resonators that the PC speakers came with intially.
The next step was to use thin-walled hardboard in the hope that I could add stiffening to the walls of the speaker cabinets, and I also fitter a port as well, following the Fostex design plans for a ported speaker.
Resonance at 500HZ has a problem, confirmed by tests, which themselves needed to be confirmed, but the 'boxiness' in the sound remained.
The mid-range, clear and loud, takes care of itself, leaving only the bass frequencies to deal with. As far as I know, there are the following methods for increasing bass frequencies
1. Increase the stiffness of the cabinet. Apparently a thin walled resonating cabinet, or an unbraced cabinet will resonate and color the sound in the lowe frequencies. By bracing the cabinet and by making the walls thicker, the theory goes, the resonances are smaller or take place in a smaller area, reducing colorations.
2. Damping material - I have not tried this yet
3. Increase the size of the cabinet - I am not sure how this affects the sound - especially with the sealed type, where the lower frequencies can only exit throught the cone itself
4. Ported or vented speaker cabinets - these will need some experimentation.
The following links are useful:
https://www.audioholics.com/loudspeaker-design/loudspeaker-cabinets
Speaker Cabinet Design - Styles and Techniques | Audiogurus
EDIT: my related threads:
http://www.diyaudio.com/forums/multi-way/287392-new-enclosures-pc-speakers.html
http://www.diyaudio.com/forums/multi-way/283170-my-low-cost-bookshelf-project.html
I have built a few speaker cabinets so far, and athough they sounded better than the ones they replaced, some work needs to be done to obtain the maximum out of the drivers I have (PC speaker drivers)
What I have learned so far:
For the on- wall and near- wall applications, the closed or ported box peforms better than the open baffle version, at least at the speaker sizes (3 inch to 4 inch) that I have been trying out.
First trials with speaker drivers mounted in cardboard boxes a more or less ear level showed very encouraging results. The best amplifier I own, which happens to be a Pioneer 50W per chanell MOSFET driven seemingly noisless amplifier is used to aim music directly at my feet, and the other amplifier in use is used to drive two large Sony SS-333 speakers mounted on a high cabinet in the living room.
It can be said that I have not been enjoying direct music for much of the time, and wall mounted speakers were the only way to achieve this and preserve space.
Placing the speakers in cardboard boxes improved the sound vastly over the plastic resonators that the PC speakers came with intially.
The next step was to use thin-walled hardboard in the hope that I could add stiffening to the walls of the speaker cabinets, and I also fitter a port as well, following the Fostex design plans for a ported speaker.
Resonance at 500HZ has a problem, confirmed by tests, which themselves needed to be confirmed, but the 'boxiness' in the sound remained.
The mid-range, clear and loud, takes care of itself, leaving only the bass frequencies to deal with. As far as I know, there are the following methods for increasing bass frequencies
1. Increase the stiffness of the cabinet. Apparently a thin walled resonating cabinet, or an unbraced cabinet will resonate and color the sound in the lowe frequencies. By bracing the cabinet and by making the walls thicker, the theory goes, the resonances are smaller or take place in a smaller area, reducing colorations.
2. Damping material - I have not tried this yet
3. Increase the size of the cabinet - I am not sure how this affects the sound - especially with the sealed type, where the lower frequencies can only exit throught the cone itself
4. Ported or vented speaker cabinets - these will need some experimentation.
The following links are useful:
https://www.audioholics.com/loudspeaker-design/loudspeaker-cabinets
Speaker Cabinet Design - Styles and Techniques | Audiogurus
EDIT: my related threads:
http://www.diyaudio.com/forums/multi-way/287392-new-enclosures-pc-speakers.html
http://www.diyaudio.com/forums/multi-way/283170-my-low-cost-bookshelf-project.html
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Re-visited this thread after some time, useful reference, and some things make more sense now. Look to update this with recent tests with loudness and tone controls and how it relates to speaker design.
Some information at this thread:
Help me design my home music system amplifier with loudness controls.
Some information at this thread:
Help me design my home music system amplifier with loudness controls.
A microphone can pick up complex waveforms like the sum of two instruments or a voice which has lots of harmonics.
The speaker works the same.
In fact a speaker can be used as a microphone. the "big ear" used to work that way.
I found this incredibly useful:
RMAF11: Loudspeaker Measurements Explained, John Atkinson, Stereophile Editor - YouTube
RMAF11: Loudspeaker Measurements Explained, John Atkinson, Stereophile Editor - YouTube
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