LG's Super Blu PC plays Blu-ray, HD DVD and DVD

Korean manufacturer, LG Electronics announced they will start selling a PC that includes their hybrid HD DVD / Blu-ray drive. It looks like it is probably the drive that reads both HD formats and burns DVD and CD. The PC comes with a Core 2 Duo cpu and an NVidia GeForce 8xxx series graphics card. There's no information on the price or availability.

Oh, and you gotta love the models. Kind of reminds me of an American trade show from the '70s.

Modular / Open Architecture Design

I like the fact that you can purchase the building blocks to assemble a PC to your exact specifications. The technically savvy person can buy the chassis, power supply, motherboard, cpu, memory, graphics card, sound card, disk drives, etc., etc., from several different manufacturers and put together a system that costs less or performs better than the pre-assembled systems from the major PC manufacturers. Of course, if you are not technically savvy, you can also purchase a complete system from the hundreds of retailers. Since there are so many PC manufacturers, the prices are very competitive. This is possible because of the open architecture of the PC. I think this might have contributed to the popularity and growth of the PC. On the other hand, Apple's proprietary products may be considered a little higher quality, and that may be due to the fact that Apple has greater control over their supply chain, but they also charge more for their PCs. When you compare market share, the open architecture PC is the clear winner.

Open architecture or modularity might work for an audio system similar to the way it has for PCs. Standard components could be available for the power supply(s), PC audio interface, preamp, amp modules and chassis. The preamp would be similar to a PC's motherboard. This is where the source devices would be selected and routed to the amp modules, plus it could include circuitry for analog volume control. The PC audio interface would have all the functionality of the PC's sound system. It would include the interface to the PC using USB or FireWire, along with the DSP, ADC and DAC chips. An amp module would provide the power for one channel or speaker output. Or maybe some manufacturers could design modules that provide stereo pairs at less cost. Amp modules of different power ratings, like 100W, 200W, 400W, etc. could be available, just like we currently can choose hard drives with different storage capacities. These amp modules could also come with integrated power supplies like the ASP Series from IcePower shown on the left. The chassis could be designed with standard layouts and connectors similar to what is currently available for today's PCs. There might be small cases for 2 channel stereo systems, larger 5.1 or 7.1 surround or even huge tower systems that could house enough channels for a sizable whole house audio system. Someone could choose a very basic chassis with a plastic or painted sheet metal skin and save some money, while others could purchase an expensive thick gauge aluminum chassis with a polished finish.

This open architecture approach has a few serious challenges. To be successful, the components have to be designed with standard connectors and form factors. Just like the hard drive's enclosure is designed with a 3.5" form factor and standard connectors for data and power or a PCI card that fits into the connector on the motherboard, has standard heights and widths and includes the backplate to attach to the back of the chassis. It will probably be difficult to get the component manufacturers to agree on standard connectors and form factors unless they are confident there is a large market for these standardized products. In the early PC days, the IBM architecture was very popular because IBM was a well established, respected company. I don't know of any other manufacturer that could have accomplished this level of standardization and there really isn't anybody in the audio industry with that type of clout today. Besides, most of the manufactures prefer to offer their mostly proprietary solutions.

In addition to the open architecture with standard components, there's also modular design. By this, I mean providing specific components for certain tasks. Separate components for the PC interface, the preamp, amp modules, power supplies, chassis, etc. There's also the separate components you can purchase for your home theaters and sound systems. For example, you can buy a CD and/or DVD transport, D/A processor, preamp, and amplifiers. The specialized components usually sound better, look better and cost a lot more than an integrated solution. Amplio's prototypes have been integrated solutions that include the PC interface, DAC/processor, power supplies, and amp modules all in the same chassis. However, some customers might prefer the flexibility of separate modules. We could provide different products like a preamp that combined the PC interface, DAC, volume control, etc., and amps that can be purchased in mono, stereo or multichannel configurations. Two flavors of preamps might let you choose between a 2 channel or 8 channel solution. The combination of an 8 channel preamp and 3 - 2 channel amp modules plus 1 mono amp module would result in a good 7.1 system. Here's an example of an interesting modular design for PCs called the UNI Computer. Maybe we could do something similar for the preamp and amp modules.

If you have any thoughts or questions about modular and/or open architecture design, I'd love to hear from you. Please feel free to post a comment!

The Bad Plus

The Bad Plus are performing in Madison on Friday, September 21st at The Annex.



I can't wait!!

Dynamic Range and HD Audio

Recently, I responded to a comment in an AVS Forum thread where someone posted that people shouldn't get too upset if their high definition audio is converted and resampled to 16 bit/48KHz. Apparently PowerDVD, the only PC software capable of playing HD DVD or Blu-ray movies, converts and resamples all of the HD 24bit/96kHz uncompressed or losslessly compressed audio (DTS-HD, Dolby TrueHD, etc.) to 16bit/48kHz. Many people are upset and would like to find a way to play the full resolution HD audio tracks from their HTPCs. The developer of PowerDVD says they have to downsample the audio because the PC doesn't provide a secure pathway for digital or analog output. I can understand why there might be some problems with a secure pathway for digital output without something like HDCP or AACS, but I don't understand why they have to downsample the audio for analog output. Anyhow, he/she basically stated that since the highest frequency a human is capable of hearing is 20,000 Hz, even when applying the Nyquist theorem to 48 kHz, the downsampled audio can still easily reproduce all audible frequencies. Therefore, I think he/she assumed the only advantage to 24bit/96kHz HD audio is the fact they can play higher frequency sounds. Well, there's a lot more to it than that...

My response just touched on the issue of how the resolution of the audio data is related to dynamic range. There are other factors that come into play, like the tonal effects of high frequency harmonics and phase accuracy. There's also the argument that when an analog waveform is converted into digital data, the higher the sampling rate and resolution of the data, the representation of the original analog signal will be much more accurate. There are also concerns about the quality of the resampling algorithm, etc., etc.

Let me get back to the subject of this post - dynamic range. Dynamic range, when used in audio measurements, refers to the difference between the loudest undistorted sound and the quietest passages. In digital audio, the maximum possible dynamic range depends on the bit depth of the audio data.

To calculate the maximum theoretical dynamic range based on a digital audio bit depth, you multiply the log of the total bit depth by 20.

Dynamic Range = 20 * log(bit depth)

For example, CD audio has a bit depth of 16 bits. A bit is a binary unit, so they are actually referring to 2 to the power of 16, which comes to 65536 decimal units. To be more accurate, we would use 65535 because they use values from 0 to 65535.

When we apply this to the formula above, we get:
DR (16 bit CD) = 20 * log(65535) = 96dB

The maximum theoretical dynamic range for 24 bit audio comes to:
DR (24 bit) = 20 * log(16777215) = 144dB

If it is true that some classical music performances can have a dynamic range of over 110 dB, then it's also possible that an HD movie could also have this large of a dynamic range. Hopefully, there will also be some other musical performances (live or studio) that were recorded in HD and become available in HD DVD or Blu-ray that will also have this high of a dynamic range.

My point is, if the audio data is always converted down to 16 bits, we won't be able to enjoy the full dynamic range available from a high definition audio performance.

Test Your Sense of Pitch

From the National Institute on Deafness and other Communication Disorders:

Have you ever wondered how a musician can pick out a single wrong note in a complex piece of music? Has anyone told you that you are tone-deaf or have a tin ear? These all relate to a sense of pitch—roughly speaking, the highness or lowness of a sound. It's what distinguishes a soprano from a bass singer and gives each piano key a distinct identity.

Our ability to distinguish pitch is not fully understood, but we do know that it involves some processing by the brain after a sound is perceived. This means tone deafness is not necessarily linked to any hearing disorder. An individual with perfect hearing may still have trouble distinguishing pitch because of how the brain interprets the sounds.

Research shows that several percent of the U.S. population has problems with pitch perception. Studies in twins also indicates that the role of inheritance in deficits in pitch recognition is extremely high, with little effect of environmental experience. Tone deafness appears to stem from nature, not nurture.

Want to test your own sense of pitch? We've developed an online version of the Distorted Tunes Test, a standardized survey in use for over 50 years. In it, you'll listen to a series of snippets from well-known tunes—some of which have been distorted by changing various notes' pitch. Your task is to pick out the incorrectly played tunes.

Give it a shot. I picked 26 out of the 26 snippets correctly, so I must have a fairly good sense of pitch. Most of the tunes were pretty familiar to me, so it was easy to hear mistakes. The test may not be so easy if you are not familiar with the songs.

Prototype Sketch

OK, so maybe this isn't really a prototype sketch, but I thought it was a pretty cool illustration and that readers of the blog might appreciate it. I came across the drawing on Audio DesignLines article "Amazing Hi-Fi' cartoon/illustration from 1950s". It was drawn by Roy Doty for the April 15th, 1958 issue of Look Magazine. Click on the Audio DesignLine article link to download a copy of the original image.

How Much Power Do I Need?

Have you ever wondered how much power you will need from your amplifier to drive your loudspeakers?

Maybe this information will help you figure this out.

Amplifier power is usually given in watts, which is the amount of energy expended in one second (1 joule per second). In electrical terms 1 watt is equal to 1 volt multiplied times 1 ampere. Not sure if that helps here, because this doesn't seem to directly relate to how much sound you can generate with an amplifier. We usually measure the loudness of something using decibels or dB. The dB uses the logarithmic (base 10) scale because that is how our ear/brain perceives sound changes. Theoretically, the smallest change in sound level the human ear can perceive is 1 dB.

The following chart shows the amount of dB per watts ((dBW), which will make it a little easier to relate the amplifier's power rating to the amount of sound it can provide:

dBW	Watts	dBW	Watts
17	50	24	251
18	63	25	316
19	79	26	400
20	100	27	500
21	126	28	630
22	156	29	795
23	200	30	1000

As you can see from this chart, an increase of 3 dB results in a doubling of power. So to handle an increase in dB from 23 to 26dB, you will need to double the power from 200 to 400 watts. To be able to notice the next incremental increase in loudness, you would need to go up to 500 watts.

Another factor that we need to consider is -- How loud do you need to go? That depends on your listening preferences. If you normally listen at fairly quiet levels, you don't need a lot of power, but if you like listening to rock music at live concert levels, then you may need a lot. Here's another chart (I love charts) to show how the dB relates to different sound levels:

Decibel (dB) level	Cause or Effect
-80 (p)	Underwater nuclear submarine microphones listening to shrimp chewing on food at 100 meters distance
-30 (n)	One human talking 20 miles away (60 db / meter at a distance of 20 miles)
-4 to +4 (n)	The ticking of an ordinary wristwatch at 1 meter
0 (n)	Beginning of hearing, a mosquito 10 feet away, the ear drum moves less than 1/100 the length of an air molecule
10 (p)	Absolute silence, AT&T - Bell Labs "Quiet Room"
13 (p)	Ordinary light bulb hum
15 (n)	A pin drop from a height of 1 centimeter at a distance of 1 meter
30 (p)	Totally quiet nighttime in desert - impossible anywhere near city
35 (p)	Anechoic hearing test room
40	A whisper
50-65	A normal conversation
80	Average city traffic noise
85	Beginning of hearing damage (8 hrs), earplugs should be worn
85-90	Lawnmower, food blender
100	Normal average car or house stereo at maximum volume
104-107 (p)	The beginning of pain at the most sensitive frequency of 2750 hertz
110	Symphony orchestra
116	Human body begins to perceive vibration in the low frequencies
117-123	Home stereo system, a very loud and powerful 200-2000 watts
120-130	front row at a rock concert - up to 200 refrigerator size speakers and 50000-300000 watts of clean, full frequency sound
125	Drum set - only at the moment of striking, continous level 115
127	Human tinnitus (ringing in the ears) begins
128 (p)	Human, loudest scream measured at a distance of 8 feet 2 inches, head hair begins to detect vibration, can begin to detect very slow “blast wind” of 0.124 meters/second
130 (n)	Marching band - overall level at a distance, 100-200 members
132	Eardrum “flex” totally noticeable
133 (n)	Gunshot- ear level, may vary greatly to size and type of gun, duration converted to one second, peak level may reach 140-160
130-135 (n)	Large train horn
135	Human, a slight cooling effect begins to be noticed, from air expansion
137	Human body vibration is strong
137-140	Human ear all frequencies are painful
140	Extremely damaging to hearing no matter how short the time exposure, human throat and vocal cord vibration begins
141	Human body begins to feel nausea after a few minutes
142	Human body chest pounding is intense
143	Human body feels as if someone just football tackled your chest
144	Human nose itches
145	Human vision begins to vibrate making it slightly blurry, 1-3 degrees
148	Human vibration very uncomfortable and slightly painful
149	Human lungs and breathing begins vibrating to the sound
150 (n)	Rock concert “The Who” two 10 story stacks = 144 double refrigerator sized speakers, actual level reached 120 db at a distance of 32 meters for this normalized reading of 150 db. Continuous level 114-118db (p) at 32 meters
158	Human body vibration is violent, nausea becomes more intense
153-163	N.H.R.A. Dragsters- 5000 to 7000 horsepower, liquid nitroglycerin fuel, earthshaking at 50 feet, humans find it hard to see, and breathe 140db (p)
163 (p)	Glass breaking level, minimum, it is very hard to break glass windows. Many stories come from breaking glass but it is highly variable: it is easier to break if the window already has a crack, is very large or old and brittle and not car safety glass which can flex massively before breaking. An opera singer at 110 db may break a wineglass but it is an example of frequency resonance, and not high sound db level
145-165 (np)	Common type of fireworks at professional pyrotechnic shows
172 (n)	Boeing 727, 737, 747, 757, 767 cruising at 6 miles high mach 0.84, at the ground (sea level) loses an additional 6 db because air density is only half sea level at a height of 6 miles
180.5	Alan Dante reportedly set a new record in the world of in-car bass output by using four Stetsom 7KD amplifiers, 15 Power Master batteries, and a single Digital Designs 9918Z subwoofer.
183 (p)	6 p.s.i. Total destruction of all structures, particle velocity (blast wind) is 180 miles per hour. 0.9 miles from Hiroshima atomic bomb and 3.3 miles from 1 megaton nuclear bomb, less 0.1 % object survival
190.6 (np)	Richter scale 0 (zero) earthquake
190-195 (p)	Human eardrums rupture 50% of time
210 (np)	Richter scale 2.0 earthquake
215 (n)	Thunder, the largest positive giants. Ordinary thunder 165-180 db. Lightning strike on ocean surface 234db (p) at 2exp-5 newtons per square meter
240 (n)	Tornado, Fujitsu 5, energy guess based on 300 mile per hour wind, 1 mile wide
257 (n)	Nuclear bomb, 1 megaton (1 million tons of t.n.t.)
300 (n)	Hurricane – average, extreme energy is “diluted” by covering 500,000 square miles. Energy = approx. 1000 nuclear bombs a second.
320 (n)	Volcano eruption, Tambora Indonesia, 1815, ejected 36 cubic miles. Approximately equal to 14,000 megaton nuclear bombs or a 14 gigaton bomb based on ejected volume, change in megatons times 1.345 equals volume ejected change. If was a nuclear bomb it would create a crater about 12.4 miles wide and 1.33 miles deep. Internal pressure is believed to be about 47 million p.s.i. = 347 db (p)

(n) = Normalized total air power energy level sound plus any wind, watts or joules per second. These levels have been converted.
(p) = actual Peak pressure meter readings i.e. a force per unit area
(np) = Normalized Pressure used in explosive measurements, blast wind is not included
sources: Ultimate Sound Pressure Level Decibel Table, COPYWRITE WILLIAM HAMBY 2004, National Institute on Deafness and Other Communication Disorders.

Update 9/11/07: new entry for 180.5dB from Engadget post.

So, if you want to listen to your sound system at the same level as a symphony orchestra (I assume this is during a loud passage), you would want amplifiers with enough power to deliver around 110 dB. For rock concert levels, something between 120-130 dB. Most of the time you're probably not going to listen at these levels, especially for those of us who share their dwellings with other people, like wives, children, pets, plants, etc., etc. Maybe an amplifier that can provide 105 dB without clipping would be good enough, since you are probably listening between 85-90 dB most of the time. The dynamic range (the difference between the loudest and the quietest sound) for a good system should be from about 105dB down to maybe 35dB. This gives us a total dynamic range of about 70dB.

Now let's take this information and apply it to choosing the right size amplifier for your loudspeakers (if you like to do things ass backwards - you can also choose the right loudspeakers for your amplifier).

1. You need to find the loudspeaker's efficiency or sensitivity specification. This is the sound pressure level (SPL) at 1 watt from a distance of 1 meter, given in dB. My Precise Monitor 10s have an efficiency spec of 88dB/1 watt/1 meter. My Era D5s use those 5" long excursion drivers that provide good bass for a small driver, but they are not super efficient with a spec of 86dB. There are a lot of speakers out there today with higher efficiency, but that doesn't mean they will sound better.
   
   
2. Subtract about 10db SPL to account for the drop in sound level from the speaker to the listening position. (When you double the distance from the speaker, the SPL drops 6dB. The speaker's efficiency spec is based on a distance of 1 meter, and if the distance between the listening position and the loudspeaker is 2 meters, then the SPL drops 6dB. If this distance is 4 meters, the SPL will drop another 6dB for a total of 12dB. If the total distance is 10' (just over 3 meters) then the SPL will drop about 9dB.)
   
   
3. Add 3dB for each additional speaker in the room that will be playing music at the same level (so when you do this calculation for a stereo system you simply add 3 dB).

For my example with the Era D5s, I would get:
86dB - 10dB + 3dB (for stereo music) = 79dB.


4. Next, I need to calculate how much amplifier power is needed to get peak levels to 105dB without clipping.
   
   So I take the difference between the peak level and the loudspeaker value:
   105dB - 79dB = 26dB, which gives me the amount of power needed from the amplifier.
   
   
5. Using the first chart, you can see that I will need 400W of power to get 26dBW.

Using this method, I would need about 250W to power my pair of Precise Monitor 10s. It gets a little more complicated when you try to calculate power requirements for multichannel 5.1 or 7.1 surround sound amplifiers. That's because the amount of sound from the surround speakers is usually less than the front right, center and front left channels. If you use bass management to send all signals below a certain frequency to a powered subwoofer, that will also decrease the power requirements of the multichannel amplifier. If I find a little more data on the most common multichannel surround mastering methods, maybe I will try to tackle this problem in a future post.

Here's a handy dandy dynamic slide rule that you can also use to perform these calculations.

Update 4/8/08: I discovered that Crown has a good article on their website to help you determine how much amplifier power is needed for your loudspeakers.

1/3 of Home Networks Used for Entertainment

This was reported awhile ago in ars technica, but I thought it was significant enough (at least for our business plans) to post here.

A study by Forrester Research found that 27% of online adults in the U.S. have a home network. One third of all these home networks are now used to stream music, movies, TV shows, and other media throughout the home.

Some of the numbers used in our business plan to estimate potential market size are based upon a typical user who is tech savvy, etc. If the user has a home network, specifically used for entertainment purposes, they are more likely to be interested in a product like ours, as opposed to someone who doesn't. It is interesting to note that one of the biggest reasons given for using their home networks for entertainment uses was for streaming music.

It's nice to know there is an actual study that shows how many people who fall into this category.

Microsoft Responds to Vista Audio Problems

Last week's post, 'Networking problems when Vista Audio is Active' linked to reports from the 2CPU forums about networking problems in Vista during audio playback. Adrian Kingsley-Hughes in his "Gear for Geeks" column for ZDNET received a response from Microsoft regarding these problems. You can just read his article, but I might as well provide his list of Microsoft responses here:

• “We have been looking into this problem and are working on a doc that will go into the technical details of what we have found.”
• “Please note that some of what we are seeing is expected behavior, and some of it is not. In certain circumstances Windows Vista will trade off network performance in order to improve multimedia playback. This is by design.”
• “The connection between media playback and networking is not immediately obvious. But as you know, the drivers involved in both activities run at extremely high priority. As a result, the network driver can cause media playback to degrade. This shows up to the user as things like popping and crackling during audio playback. Users generally hate this, hence the trade off.”
• “In most cases the user does not notice the impact of this as the decrease in network performance is slight. Of course some users, especially ones on Gigabit based networks, are seeing a much greater decrease than is expected and that is clearly a problem that we need to address.”
• “Two other things to note. First, we have not seen any cases where a users internet performance would be degraded, in our tests this issue only shows up with local network operations.”
• “Second, this trade-off scheme only kicks in on the receive side. Transmit is not affected.”

Seems pretty strange to me. Slight degradation? Some people have reported network performance throttled to 5-10% when playing audio. Heck, when using Windows Media Player the network performance is reduced even when the audio is paused (using other media players like Foobar2000, the network performance is only throttled during playback). Anyhow, I never had any pops, clicks or skips when playing audio on my old Pentium III or IV hardware running Windows NT while connected to a network back around 1999. So I still don't understand why they are having this problem with today's hardware. Hopefully this will be fixed in a future patch or something.