Surround Sound
Adventures in Surround Sound, from 7.2 to Quad - Wendy Carlos
An interesting resource on surround sound by Wendy Carlos. It includes a lot of historical information on quadraphonic sound. Here is the link.
Surround Sound Page
I am in the process of setting up a surround mixing system for music. So far my research has revealed several different takes on where to place the speakers:
| surround_speaker_setups.pdf |
| surround_speaker_setups_chart.pdf |
The speakers are up
For the surround installation I purchased two sets of M-Audio AV40 speakers. One of each pair has the amplifier in one speaker (sort of a semi-powered monitor). The passive speaker is quite light, and even the one with the amp weighs only 6kg. This made mounting a bit easier and I used Wacky Brackets (Aussie made). I had to bend them a bit to get the speakers angled sufficiently to fire at the mixing position. Before I started I mapped out all the possible placements with masking tape (using a little trigonometry to get the positions correct). I wanted something suitable for music surround as well as sound for picture. Two compromises also had to be made - the room is small, and this alters the ideal placements, and although the speakers are not very heavy I don't want them falling down on anybody so the brackets had to affix to timber in the walls. In the end I put the rear speakers upside down on the back of the side walls at a height just above the top of the door. They are placed between Dave Molton's ±144º, and the ITU ±110º. One of the other pair is the Centre channel, and the other is mounted at the centre of the rear wall at ceiling height. The existing L-R monitors are a pair of Genelec 1030a. There is also a pair of Yamaha MSP5A which can be positioned out to the sides at around ±72º. For now I have ignored a sub-woofer because the room is so small. In any case it is not needed for music. Clearly, this is not the ideal setup but good enough to start experimenting with a variety of surround mixes. All the channels terminate on a patchbay for flexible configuration.
Mixing Surround in Pro Tools and Logic
My surround experiments have been shelved for the last 18 months thanks to the earthquakes. Time to get started again...here is a short document on how to setup and pan surround in either of these two DAWs.
| using_surround.pdf |
Yamaha DSP-1
While on the hunt for a quadraphonic tape recorder, I came across a Yamaha DSP-1 'Natural Sound Digital Sound Field Processor'. That's quite a name! Incidentally, 'Natural Sound' is what the NS stands for in Yamaha's NS10 speakers.
Made in 1985, it is a unit that synthesises surround sound from stereo. It can derive Dolby Surround in either 4 or 6 channels (in which case there are additional front and rear channels along with the main stereo). So far, this is just another box that was made redundant by Dolby Digital, but there is more...
The unit contains 3 of the Yamaha YM3804B LSIs. These are the DSP chips used in the Rev 7, Rev 5, and SPX-90. Effects such as reverb, phasing, chorus, and delay are available in 16-bit quality. With a sampling rate of 44.1kHz, the effects frequency response is 20 to 20kHz. Furthermore, the remote allows extensive programming of the unit, with effect parameters able to be altered (eg pre-delay on a reverb). In its day this was a top unit, with Burr Brown PCM54HP D-A convertors. It sold in the US for $1000. Yamaha were the first to do this surround spacial processing and although the DSP-1 didn't become commonplace, it led to the development of the current 'Cinema DSP' for home theatre (which works with Dolby Digital or DTS decoders).
The bottom photo shows inside the unit. You can see the D-A convertors on the main board. On the right is the DSP board, with the YM3804B ICs. Three of each is required to provide for the 6 channels. Under the DSP board is the CPU board. The unit weighs nearly 5 kg.
Made in 1985, it is a unit that synthesises surround sound from stereo. It can derive Dolby Surround in either 4 or 6 channels (in which case there are additional front and rear channels along with the main stereo). So far, this is just another box that was made redundant by Dolby Digital, but there is more...
The unit contains 3 of the Yamaha YM3804B LSIs. These are the DSP chips used in the Rev 7, Rev 5, and SPX-90. Effects such as reverb, phasing, chorus, and delay are available in 16-bit quality. With a sampling rate of 44.1kHz, the effects frequency response is 20 to 20kHz. Furthermore, the remote allows extensive programming of the unit, with effect parameters able to be altered (eg pre-delay on a reverb). In its day this was a top unit, with Burr Brown PCM54HP D-A convertors. It sold in the US for $1000. Yamaha were the first to do this surround spacial processing and although the DSP-1 didn't become commonplace, it led to the development of the current 'Cinema DSP' for home theatre (which works with Dolby Digital or DTS decoders).
The bottom photo shows inside the unit. You can see the D-A convertors on the main board. On the right is the DSP board, with the YM3804B ICs. Three of each is required to provide for the 6 channels. Under the DSP board is the CPU board. The unit weighs nearly 5 kg.
Quadraphonic lives again
The other day I bought a pair of quadraphonic headphones just for old times sake. Then I thought why not hook them up to something, so I am using the softsynths in Logic to create 4 channel mixes. These are fed through the I/O to a 4 channel headphone amp, and voila - surround sound in my headphones.
Quadraphonic FM radio
Yes, there was such a thing (in the USA). You can read about it here. The most popular was the Dorren Quadraplex system designed in 1969, with an AES paper published in 1972. Interestingly, a January 1978 Popular Science magazine mentions that at that time there was still no standard for Quad broadcasts. By then Quadraphonic sound, FM or not, was already on the wane.
Virtual Surround
Any surround sound system reproduces the sound source from multiple directions (ie more than two). Results can be dramatic but the extra complexity and cost limits the appeal of such systems. An alternative approach is to try to trick the listener into thinking he/she is hearing direct sounds from many directions from an ordinary stereo pair of loudspeakers. The generic name for this is “virtual surround”.
The principle that virtual surround works on is complex. It relies on the psycho-acoustic fact that part of our ability to distinguish sound directivity is due to the Inter-aural Time Difference (ITD). This is the arrival time delay between the ears. There is also a complex comb filtering relationship in the pinna (visible ear) and ear canal. Virtual surround attempts to generate similar transformations to the pinna and thereby fool the ear into hearing sound from a location other than between the two speakers. While it cannot rival a discrete multi-channel system (eg Dolby Digital), virtual surround can add an extra dimension to the sound.
Accuracy of location is somewhat limited, and results can vary significantly depending on listening position, and between listeners (each persons pinna transform is a unique pattern).
An example of a home theatre system using virtual surround is the Yamaha YSP1000. It uses 42 speakers in one box, which are driven from digitally phase-shifted signals to provide the 3D spatial image.
The principle that virtual surround works on is complex. It relies on the psycho-acoustic fact that part of our ability to distinguish sound directivity is due to the Inter-aural Time Difference (ITD). This is the arrival time delay between the ears. There is also a complex comb filtering relationship in the pinna (visible ear) and ear canal. Virtual surround attempts to generate similar transformations to the pinna and thereby fool the ear into hearing sound from a location other than between the two speakers. While it cannot rival a discrete multi-channel system (eg Dolby Digital), virtual surround can add an extra dimension to the sound.
Accuracy of location is somewhat limited, and results can vary significantly depending on listening position, and between listeners (each persons pinna transform is a unique pattern).
An example of a home theatre system using virtual surround is the Yamaha YSP1000. It uses 42 speakers in one box, which are driven from digitally phase-shifted signals to provide the 3D spatial image.
