Dynamic Range Expander - Page 2

Bob Richards · 23rd January 2012, 09:07 PM

I've always hated dynamic range expanders. Every time I listened to one, it sounded un-natural and irksome. But now I need to create one for my surround sound extractor project. I'm doing an L-XR on the left and right, front and side/rear signals to cancel most of the L+R signal, but for the center channel I'm doing an L+R addition, and want to include a small amount of wideband expansion, with a control signal that is bandwidth limited to upper midrange frequencies. To limit audibility of the expander effect (humping, pumping and breathing), I'm going to limit the effect to 3-6dB maximum change. I'm using the Analog Devices SSM2018T VCA chip, precision full wave rectifier circuit, peak detector with adjustable attack and decay, and now my assignment, if I choose to accept it, is to figure out the best attack and decay times. I'm thinking 1mS and 0.5S. Any thoughts will be appreciated. Where's all that smoke coming from?

Jonathan Bright · 23rd January 2012, 09:34 PM

Best place to go is "The Journal of the Audio Engineering Society". If you can get to a Tertiary institution you can probably get a photocopy. (They have a good reprint service too.) I have the article in the files back here somewhere but we moved recently and I can't put my hands on is straightaway. I think it was produced in the 1970's and it was an extremely thorough examination of the material you need. They had a wealth of data on appropriate attack/decay times. Good section on band splitting etc. (Btw there was a subsequent errata publish a month or two later with amended graphs.)

Others here may well have the answers form their own experience....might be a lot quicker!

I'll have a look for it here later today.
Might get lucky.
Jonathan

Chris Daly · 25th March 2012, 12:29 PM

DBX founded by David Blackmer David E. Blackmer - Wikipedia, the free encyclopedia
represent products specializing in companding.... their Type 1 companders are just as applicable today with CD. reproduction. Some models offered real time companding whilst others required a recording medium. I have used their 150x and 155 models.

23rd January 2012, 09:34 PM	#12
Jonathan Bright diyAudio Member Join Date: Feb 2004 Location: Queensland	Best place to go is "The Journal of the Audio Engineering Society". If you can get to a Tertiary institution you can probably get a photocopy. (They have a good reprint service too.) I have the article in the files back here somewhere but we moved recently and I can't put my hands on is straightaway. I think it was produced in the 1970's and it was an extremely thorough examination of the material you need. They had a wealth of data on appropriate attack/decay times. Good section on band splitting etc. (Btw there was a subsequent errata publish a month or two later with amended graphs.) Others here may well have the answers form their own experience....might be a lot quicker! I'll have a look for it here later today. Might get lucky. Jonathan __________________ "It was the Spring time of the year when aunt calls to aunt like mastodons across the frozen waste." P.G. Wodehouse.

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23rd January 2012, 09:07 PM	#11
Bob Richards diyAudio Member Join Date: Feb 2011 Location: Portland Oregon, USA	I've always hated dynamic range expanders. Every time I listened to one, it sounded un-natural and irksome. But now I need to create one for my surround sound extractor project. I'm doing an L-XR on the left and right, front and side/rear signals to cancel most of the L+R signal, but for the center channel I'm doing an L+R addition, and want to include a small amount of wideband expansion, with a control signal that is bandwidth limited to upper midrange frequencies. To limit audibility of the expander effect (humping, pumping and breathing), I'm going to limit the effect to 3-6dB maximum change. I'm using the Analog Devices SSM2018T VCA chip, precision full wave rectifier circuit, peak detector with adjustable attack and decay, and now my assignment, if I choose to accept it, is to figure out the best attack and decay times. I'm thinking 1mS and 0.5S. Any thoughts will be appreciated. Where's all that smoke coming from?

25th March 2012, 12:29 PM	#13
Chris Daly diyAudio Member Join Date: Sep 2004 Location: hobart tasmania	DBX founded by David Blackmer David E. Blackmer - Wikipedia, the free encyclopedia represent products specializing in companding.... their Type 1 companders are just as applicable today with CD. reproduction. Some models offered real time companding whilst others required a recording medium. I have used their 150x and 155 models.

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