Nissan 370Z Forum - View Single Post

zakimak · 04-25-2013, 04:16 PM

Part 4

Head Unit.
The head unit or radio is typically referred to as a device that has the capability to receive, decypher and convert various signals into a low level analog or digital signal so that it may be used by the device down the line - typically some sort of amplification or frequency division network/DSP.

For instance, it may receive radio or satellite signal, convert various compression formats (mp3, mp4, WMA, WMV, Ogg, FLAC, etc) or playback CDA or HD Audio, DTS Audio or DVD Audio data. There’s a vast number of features that may be brand or model specific but essentially they all do the same thing, providing an audio signal to the next device. Some will have built in amplification which can be use to power speakers but are typically very limited. DSP are typically limited to simple effects (stadium, hall, bathroom, karaoke, etc)

Location in chain: Beginning

What to look for:
Essentially most modern brand name head units are features specific. Whether it be navigation, Video, Bluetooth voice or streaming, Iphone integration, format support, etc. The differences and will usually reflect in the price are the features. It is best however, to spend sometime testing the GUI and look at the display carefully. Not all display/touch surfaces are the same as cheaper one tend to use resistive screens rather than capacitive ones which are better in the majority of cases as they have better visibility in sunlight and sensitivity. An alternative and gaining popularity are computer based systems which requires customizations and component sourcing. If you decide to go this route, I suggest doing a lot of research into it as the technology availability changes daily. Personally, I would prefer using something simple like and Ipad, playbook, Nexus, etc. One caveat, give some serious listening to the output stage of these units as any of their deficiencies will be very relevant when amplified which didn't seem to be objectionable when heard through the earbuds before.

In the Z34:

Base Audio: Plays CD and radio but no decompression (mp3/wma) capability nor satellite radio. Onboard amplification. 4 Speakers (tweeter and woofer)

Bose system: Plays CD, mp3, wmv, satellite. 6 speakers and 2 subwoofers, outboard amplification

NAV: Same as bose plus navigation with USB and HD system with 9 GIG data built in

Division Network/Etc

These devices do not generate signal themselves but rather take the signal from the head unit and process them according to their function.

Line Driver
Importance: output level and frequency response.

This is a device that performs like a simple amplifier that boost a low level signal from the head unit to a level that is much higher (typically 10v<) to keep the noise floor down. Some design would include a gating function which would shut off any signal being pass down the line if no signal is present at the input stage.

What to look for:
There really isn't much to look for here with the exception to the signal to noise ratio and output voltage. Measured in db and volt, the higher the value, the better. Signal to noise ratio measure the background noise a component makes when there are no signal. Since this is a mini-amplifier, be aware as to how this rating was achieved. At maximum rated output or at standard 2V. Although less significant, it does have some effect as the higher the output, the differences will be more pronounce. Always compare apple to apple.

In terms of output, the higher the voltage, the cleaner the signal can be used to drive multiple devices while keeping the noise floor low.

Location in chain: Usually before the amplifier

Digital Signal Processing (DSP)
Importance: Type, number of effects, adjustment level, output level

Famously first use in the studio by Lexicon then made popular on the consumer level by Yamaha, this is a device that incorporate signal delays/division/equalization and mix it back into the chain or alternative path for further processing. Famous for the stadium, hall and bathroom effects and are highly effective in movie production where individual signals can be manipulated to simulate a helicopter fly-over. In car audio, it is pretty limited since I have yet heard an unit that can process full HD/DVD/ audio effectively. One aspect that can be effectively use is timing of individual drivers. As stated above in localization, individual driver timing can be accomplish to ensure the sound from each individual driver will arrive at the same point at the same time. This greatly reduce delays variations.

What to look for:

Adjustability and flexibility. Aside from the gimmicky sound effects, the main use is time delay. Look for ones that has tine tuning (small increments) and total number of channels available. This would allow individual adjustment to individual drivers. Be aware, that expert tuning with proper measurement tools will be necessary to fully use this effectively. As much as some who hates OEM systems, this area is where they truly excel. Tuning for specific trim levels due to different textures are completely possible but is prohibitively expensive aftermarket.

Location in chain: Usually after the head unit

Equalizer
Importance: Type, number of bands (20Hzto20KHZ), adjustment level, Q curve.

Dependent on the head unit, most are limited in the number of bands available for adjustment. Usually you can expect a Bass and Treble (typically at 100hz and 10KHZ). A dedicated EQ will allow more frequency bands for finer adjustment. The more you have the more adjustability to shape the sound.

There are essentially two types commonly use. Parametric and Graphic. Parametric EQ allow you to sweep between a predetermined set of frequencies and then have the ability to increase or decrease the level of the selected frequency. This is very desirable since the flexibility would allow pinpointing the exact frequency you would want to adjust. Graphic equalizer contain predetermine frequencies and would only allow level adjustment. A word on Q. This term is refer to the effect or the curve of the band adjacent to either side of the frequency that is being adjusted. The higher the Q the less effect. Think V verses U. Q can sometimes be adjust but are typically found only in Parametric EQ. Usually the greater the number of bands, the lower the Q in order to have a more precise adjustment of said frequency. In general, Graphic EQ are often use to shape the sound where as Parametric EQ is to fix certain undesirable frequency within the system.

What to look for:

The more you bands you have the more adjustability. That said, the ability to increase that particular band is meaningless if you can't increase or decrease it sufficiently. Expect any decent unit to have the capability to do it with +/- 12db. Anything above 18db or more acts like a filter and when having the ability to adjust the Q to very narrow band, can act like a frequency kill.

Location in chain: Usually after the head unit

Continue to Part 5

04-25-2013, 04:16 PM	#4 (permalink)
zakimak 6/2/80 - 9/29/14 - RIP Lukas Join Date: Jun 2011 Location: Ottawa, Ontario Posts: 450 Drives: ZR; Q45; VTR1K, GT65 Rep Power: 17	Part 4 Head Unit. The head unit or radio is typically referred to as a device that has the capability to receive, decypher and convert various signals into a low level analog or digital signal so that it may be used by the device down the line - typically some sort of amplification or frequency division network/DSP. For instance, it may receive radio or satellite signal, convert various compression formats (mp3, mp4, WMA, WMV, Ogg, FLAC, etc) or playback CDA or HD Audio, DTS Audio or DVD Audio data. There’s a vast number of features that may be brand or model specific but essentially they all do the same thing, providing an audio signal to the next device. Some will have built in amplification which can be use to power speakers but are typically very limited. DSP are typically limited to simple effects (stadium, hall, bathroom, karaoke, etc) Location in chain: Beginning What to look for: Essentially most modern brand name head units are features specific. Whether it be navigation, Video, Bluetooth voice or streaming, Iphone integration, format support, etc. The differences and will usually reflect in the price are the features. It is best however, to spend sometime testing the GUI and look at the display carefully. Not all display/touch surfaces are the same as cheaper one tend to use resistive screens rather than capacitive ones which are better in the majority of cases as they have better visibility in sunlight and sensitivity. An alternative and gaining popularity are computer based systems which requires customizations and component sourcing. If you decide to go this route, I suggest doing a lot of research into it as the technology availability changes daily. Personally, I would prefer using something simple like and Ipad, playbook, Nexus, etc. One caveat, give some serious listening to the output stage of these units as any of their deficiencies will be very relevant when amplified which didn't seem to be objectionable when heard through the earbuds before. In the Z34: Base Audio: Plays CD and radio but no decompression (mp3/wma) capability nor satellite radio. Onboard amplification. 4 Speakers (tweeter and woofer) Bose system: Plays CD, mp3, wmv, satellite. 6 speakers and 2 subwoofers, outboard amplification NAV: Same as bose plus navigation with USB and HD system with 9 GIG data built in Division Network/Etc These devices do not generate signal themselves but rather take the signal from the head unit and process them according to their function. Line Driver Importance: output level and frequency response. This is a device that performs like a simple amplifier that boost a low level signal from the head unit to a level that is much higher (typically 10v<) to keep the noise floor down. Some design would include a gating function which would shut off any signal being pass down the line if no signal is present at the input stage. What to look for: There really isn't much to look for here with the exception to the signal to noise ratio and output voltage. Measured in db and volt, the higher the value, the better. Signal to noise ratio measure the background noise a component makes when there are no signal. Since this is a mini-amplifier, be aware as to how this rating was achieved. At maximum rated output or at standard 2V. Although less significant, it does have some effect as the higher the output, the differences will be more pronounce. Always compare apple to apple. In terms of output, the higher the voltage, the cleaner the signal can be used to drive multiple devices while keeping the noise floor low. Location in chain: Usually before the amplifier Digital Signal Processing (DSP) Importance: Type, number of effects, adjustment level, output level Famously first use in the studio by Lexicon then made popular on the consumer level by Yamaha, this is a device that incorporate signal delays/division/equalization and mix it back into the chain or alternative path for further processing. Famous for the stadium, hall and bathroom effects and are highly effective in movie production where individual signals can be manipulated to simulate a helicopter fly-over. In car audio, it is pretty limited since I have yet heard an unit that can process full HD/DVD/ audio effectively. One aspect that can be effectively use is timing of individual drivers. As stated above in localization, individual driver timing can be accomplish to ensure the sound from each individual driver will arrive at the same point at the same time. This greatly reduce delays variations. What to look for: Adjustability and flexibility. Aside from the gimmicky sound effects, the main use is time delay. Look for ones that has tine tuning (small increments) and total number of channels available. This would allow individual adjustment to individual drivers. Be aware, that expert tuning with proper measurement tools will be necessary to fully use this effectively. As much as some who hates OEM systems, this area is where they truly excel. Tuning for specific trim levels due to different textures are completely possible but is prohibitively expensive aftermarket. Location in chain: Usually after the head unit Equalizer Importance: Type, number of bands (20Hzto20KHZ), adjustment level, Q curve. Dependent on the head unit, most are limited in the number of bands available for adjustment. Usually you can expect a Bass and Treble (typically at 100hz and 10KHZ). A dedicated EQ will allow more frequency bands for finer adjustment. The more you have the more adjustability to shape the sound. There are essentially two types commonly use. Parametric and Graphic. Parametric EQ allow you to sweep between a predetermined set of frequencies and then have the ability to increase or decrease the level of the selected frequency. This is very desirable since the flexibility would allow pinpointing the exact frequency you would want to adjust. Graphic equalizer contain predetermine frequencies and would only allow level adjustment. A word on Q. This term is refer to the effect or the curve of the band adjacent to either side of the frequency that is being adjusted. The higher the Q the less effect. Think V verses U. Q can sometimes be adjust but are typically found only in Parametric EQ. Usually the greater the number of bands, the lower the Q in order to have a more precise adjustment of said frequency. In general, Graphic EQ are often use to shape the sound where as Parametric EQ is to fix certain undesirable frequency within the system. What to look for: The more you bands you have the more adjustability. That said, the ability to increase that particular band is meaningless if you can't increase or decrease it sufficiently. Expect any decent unit to have the capability to do it with +/- 12db. Anything above 18db or more acts like a filter and when having the ability to adjust the Q to very narrow band, can act like a frequency kill. Location in chain: Usually after the head unit Continue to Part 5 __________________ What doesn't kill you might make you a cripple so chose wisely. Free Stuff for Premium Members - Yeah Really Last edited by zakimak; 04-27-2013 at 10:44 AM.