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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
 Posted - Apr 23 2009 : 04:12:24 AM
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Hello everybody,
I want to get more involved into audio. You can assume that I am a newbie. The goal of this project is to make a "Home Made Digital Surround Sound Speaker System" "Home Made Advanced Digital Home Theater System" I will be posting my progress on this project as time time goes by. Sometimes I may need your valued and experienced opinions on certain things, so therefore I will base this thread as the hub of this project. Feel free to post your own resources, I will add them to this first post if they are relevant.
This first post will contain resources I will be referring to. I will add important info to this first post. If I refer to a particular resource you can always find it in this post.
Features and Specifications (There are still uncertainties with this):
- Highly configurable sound system.
Wireless surround speakers have their own Class D amplifiers. Note: Another approach is being devised.
- Surround speaker units are 3-way and bi-amped (maybe). Passive crossover between mid-range and tweeter if bi-amped.
The ability to use audio DSP to enhance the audio and adjust delays and frequency spectrum amplitudes etc.
- Use a modified low-profile x86 architecture processing platform for processing of sound and to provide media playback facilities.
- Digital Inputs:
Four pairs of S/PDIF audio inputs, both RCA and Optical data links per pair.
- Analog Inputs:
Four pairs of RCA audio inputs. Assignable. for: FL FR SL SR RL RR CENTER SUBWOOFER per set
- Power requirements to head unit:
100VAC to 250VAC, 50-60Hz with a fused C14 chassis socket.
*-Head unit should pass less than 50W.
- Power requirements to subwoofer:
100VAC to 250VAC, 50-60Hz with a fused C14 chassis socket.
- Power requirements to surround speakers:
100VAC to 250VAC, 50-60Hz with a fused Unpolarized C7 Line Connector.
- Surround sound speaker units and subwoofer unit(s) are expected to be far away from the head unit. Each surround sound speaker unit contains a small efficient SMPS, subwoofer unit(s) as well. Surround sound speaker units and subwoofer unit(s) acquire their sound data via a digital link RCA connector on the back face of the unit which connects to the head unit. This method means that theoretically unlimited numbers of speakers can easily be assigned to a each channel for boosted loudness for large rooms.
Resources/Research:
http://www.smps.com/Knowledge/MOSFET_Switching/FETsw_p1.shtml
http://www.epanorama.net/documents/audio/spdif.html
http://sound.westhost.com/articles/pwm.htm
 spdif.zip 13.33 KB
subwoofer_big.jpg 42.3 KB
images-details-truesubwoofereqsigpr.jpg 107.62 KB
Alpine_Swx_1242d_12_3000w_Dual_4_ohm_Subwoofer.jpg 17.73 KB
Polk_Audio_PSW10_subwoofer.jpg 35.34 KB
subwoofer-Pioneer-TS-WX301.jpg 38.33 KB |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
Edited by - wasssup1990 on Sep 25 2009 12:53:12 AM |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 23 2009 : 04:23:30 AM
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I'm researching and looking at the S/PDIF output on my oscilloscope. I'll see if I can decode it with one of my microcontrollers and play the sound.
Research:
Data is sent out in blocks of 192 frames. There are 2 sub-frames per frame, one for each channel (LEFT, RIGHT).
A "B" preamble preceeds channel1 of a new data block for the (LEFT) channel.
After the first subframe ("B"+channel1) has been sent a "W" premble will then be sent preceding channel2. ("B"+channel2) subframe is now sent.
FRAME
{
A "M" preamble preceeds channel1 (LEFT).
A "W" preamble preceeds channel2 (RIGHT).
}
Loop back to FRAME for the remaining 191 frames to be sent.
"M" Ch.1 "W" Ch.2 "B" Ch.1 "W" Ch.2 "M" Ch.1 "W" Ch.2 "M" ...
| ||_ sub __|_ sub _|| |
| || || |
|__ Frame 191 ___||__ Frame 0 ___||__ Frame 1 ____|
Refer to page1 of spdif.pdf to see the makeup of a sub-frame.
Important:
Datarate of encoded audio = 2 * audio_sample_rate
e.g.
SPDIF_out(bps) = 2 * 44KHz
= 88(Kbps)
Researching... Datarate of encoded audio should be at least double the audio sample rate. It's more complicated. Depends on audio channel resoltion e.g. 8/16/20/24bit and the number of channels e.g. stereo, 2.1, 5.1, 7.1.
Each subframe contains 32 bits.
Audio sample word == 20 bits OR 24 bits (20 bits Typical)
Bits 3 through to 31 in a subframe are coded using BMC (Biphase Mark Code), it's a digital form of phase modulation.
The "B" preamble symbolises the start of a new data block since it can be easily detected because it violates BMC and is the only preamble of its type that occurs in a datablock, right at the start of it.
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The electrical signal output characteristics:
- AC only! (Convert from TTL to AC signal)
- 75-ohm(terminated) coaxial OR optical interface
- 100KHz to 8MHz
- 0.4Vpp to 0.6Vpp (Although my computer shows > 1Vpp on its output)
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When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Apr 23 2009 : 09:26:38 AM
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A company sells extremely expensive speaker cable (Monster Cable)to gullable fools who believe the lies that it makes the sound better. Just use lamp cord instead of telephone wire.
You do not need DSP nor equalization to cancel the resonance of a speaker. The enclosure design uses the resonance for a flat extended bass response. There are computer programs that design the enclosure for the detailed spec's of the raw speakers. Then you can change the size or the type of enclosure to see what happens to the response of one speaker or change speakers.
I made speakers from existing enclosures that are too small, added a port that is tuned too low then added bass boost to simulate a larger enclosure and they sound pretty good. I used Boxplot program to see all the changes. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 23 2009 : 10:06:48 AM
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Hi John,
quote:
A company sells extremely expensive speaker cable (Monster Cable)to gullable fools who believe the lies that it makes the sound better. Just use lamp cord instead of telephone wire.
I'll go wireless. I'll draw up a diagram of what I intend to do, then we can see if it a good idea.
I should mention that this is just a learning exercise for me. I won't be selling anything. I'll become more sharp in DSP, radio comms, audio, programming and power supplies.
quote:
There are computer programs that design the enclosure for the detailed spec's of the raw speakers. Then you can change the size or the type of enclosure to see what happens to the response of one speaker or change speakers.
I'll be using my physics simulator. I'll create a virtual environment and different enclosures and then I'll be able to simulate how the air molecules respond and monitor frequency response and other things. You'll be able to see it all in 3D, now that's pretty cool man. Probably far better than anything that's out there already. I have been getting lazy on posting updates on my physics simulator thread, but you should see what it can do. You will eventually. Still a lot of work to do though.
If you want an idea of what my physics simulator is capable of watch this video.
So yeah I will draw up that diagram when I can. |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
Edited by - wasssup1990 on Apr 23 2009 10:34:01 AM |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 24 2009 : 06:12:56 AM
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I'm drawing how everything will look. This is quite a high tech system. It's being designed for a guy like me.
I'm using paper to draw the concept art. I will then scan it and post it here. |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 24 2009 : 07:14:48 AM
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When I say wireless I mean the there are only cables for mains power for all speakers. All audio signals travel in a digital form wirelessly.
The advantage of this is:
The rear speakers don't need to be hooked up to the head unit. They can stay at the back of the room and just plug them into the power point there. No need to run an audio cable back to the head unit. The active subwoofer is described with a picture in the next post. |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 24 2009 : 07:19:57 AM
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It's not a washing machine ok.
Download Attachment: Picture.jpg
132.06 KB
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When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 24 2009 : 07:50:20 AM
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I have tested and experienced the simplicity and energy efficiency of PWM audio before. I will therefore make this sound system using CLASS D amplifiers. This after all is a digital sound system.
http://sound.westhost.com/articles/pwm.htm |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
Edited by - wasssup1990 on Apr 24 2009 09:11:11 AM |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 24 2009 : 07:55:17 AM
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I have a question now.
Would I get better sound quality if, for each surround speaker, I used several speakers to achieve full range or just one full range speaker? |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
Edited by - wasssup1990 on Apr 24 2009 09:10:55 AM |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 24 2009 : 10:29:43 AM
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Download Attachment: home_theatre4.jpg
24.81 KB
Yeah! That looks good.
Maybe I should have active (wireless) speakers that can be mounted and dismounted from a stand.
By the way, all the surround sound (full range) speakers can be selected as FL, FR, RL, RR et cetera from the control panel on the active subwoofer. Each surround speaker has a unique number that identifies it and allows that speaker to play the correct audio channel. |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 24 2009 : 8:52:43 PM
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| Audioguru what speakers to you recommend? A particular brand? What should I be looking for? |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 25 2009 : 05:04:12 AM
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Download Attachment: Picture 001.jpg
123.63 KB
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When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 25 2009 : 05:37:58 AM
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Download Attachment: Picture 002.jpg
89.62 KB
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When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 25 2009 : 07:20:35 AM
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Download Attachment: Picture 003.jpg
92.44 KB
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When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 25 2009 : 07:34:56 AM
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Download Attachment: wavelength.PNG
75.88 KB
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When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Apr 25 2009 : 09:15:43 AM
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Back to S/PDIF
I have been doing some experiments. I'm looking at the S/PDIF output on the oscilloscope. It was hard to set the trigger level because the signal is always changing, but eventually I homed in on a stable trigger. I am looking at a subframe. If you don't know what a subframe is go back a few posts. On my computer I have set the "Output sample rate" to 44.1KHz. Let's see if we get double this. We should get double the frequency (88.2KHz) because S/PDIF uses BMC.
TIME/DIV = 2us
Division taken up be the subframe = 5.9
Period = 5.9 * 2us = 1.18e-5 (0.0000118) seconds
Frequency = 1/(1.18e-5) = 84.746KHz
Yes! We are not exactly at 88.2KHz but very close. That was confirmation experiment well done. |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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Topic |
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Home Made Advanced Digital Home Theater System
subwoofer_big.jpg
images-details-truesubwoofereqsigpr.jpg
Alpine_Swx_1242d_12_3000w_Dual_4_ohm_Subwoofer.jpg
Polk_Audio_PSW10_subwoofer.jpg
subwoofer-Pioneer-TS-WX301.jpg