6 replies to this topic

[Madmax]

jus thought i would put a few things down about all the abbreviations there are in the audio world...

1. PMPO - stands for Peak Music Power Output, amount of power a speaker/sub can take for around 0.5 seconds, manufacturers put it to make their products sound good.

2. RMS - Root Means Squared, the amount of power a speaker can take all day long every day. Best to go for a speaker with a higher RMS if you like your music loud all the time.

3. Impedance - This means the total resistance in the flow of the electrical circuit in the speaker/amp. measured in Ohms. for instance a speaker with a low impedance is much harder for an amp to drive it.

4. Sensitivity - this means that the speaker will deliver 'this much sound' with a certain amount of power given by the amplifier in the head unit etc. sneisitivity is measured in decibels.

5. Pre-Outs - These are amplifier Pre-Outputs that give additional amplifiers a good quality audio signal to use to boost up to the powered speakers. A good pre out level is usually around 4-6 volts. Any lower and the signal can become quite fuzzy.

6. 8,16 and 24 bit conv - this is the conversion rate of the CD players electronics, usually marked DAC (digital-to-analogue-converter). The faster and larger conversion rate, the higher quality the sound. 24bit units can start just over 500 quid.

7. subwoofer blending - this is the term for when the subwoofer and other speakers are properly matched to get the optimum sound of the system. If they are not blended properly it can end up sounding pap.

8. Class A and B amplifiers - there are two major differences between these two types of amplifier. class A amplifiers run the positive and negative signals at the same time, this causes the amplifier to be quite hot (most need fans) as the transistors are permanently used, class A amps are a much better sounding amp. Class B use a diferent circuit to concentrate on the negative signals. This means that some sound quality is lost due to a. extra circuit, b. signal strength lost.

9. Colouration - This is when the bass starts to boom or the treble starts to sound really really tinny. Its not something good.

10. Crossovers - This is a little device which switches the sound between high and lows, then to the right speaker. eg, 13 cm sub (low and mid) and tweeter (high).

11. Bridging this is when you make a 2ch/4ch amp into a mono amp by taking the two/four outputs that are there and turning them into one much more powerful output, basically this is used to allow more power to run the desired sub. it involves hooking up one side of the positive and using the other side of the negative, its very simple and can easily be worked out just by looking at the side of the terminals as theyre almost always marked

errrrrr thats about all i can think of at the moment, i may add some more later.

james

Edited by Madmax, 05 July 2005 - 10:03 PM.

[TimS]

ok just a few little bits to add:


Root Mean Squared

Is actually calculated backwards so Square the peak Figure, Take the Mean and then root it. This is que to the average voltage or wattage of an alternating current being 0 (emagine a sine wave) so this is how to take an average of an alternating current.


Classes of amplifiers

There is also another class of amp Class C, this has even worse sound quality but generate extreemly high powers usually 1000watts RMS+ and due to is poor sound quality it is not sued on free air or std speakers instead Subwoofers as sound quilty isnt very noticable with in low frequencies.


Crossovers

Just to expand a little really, all a crossover is is a resistor and capacitor that smooths out different parts of an alternating signal! so depending on the size of resistor and capacitor depends which frequencis are blocked. this is the crude way, there are also more technical electronic circuitry that will do the same

Edited by Madmax, 07 February 2005 - 02:03 PM.

[Madmax]

Capacitors

THEY ARE WIRED IN PARALLEL ACROSS THE AMPLIFIER

if they are wired in series they do not work, they require a negativ and positive feed, wiring in series would not provide these two feeds.

a power capacitor is basically a big battery to suck up all the draining bass notes...





thanks to P91LMER for providing the image

Edited by Madmax, 07 February 2005 - 02:01 PM.

[Madmax]

and just to add a little more that i thought i added....

Gain- is the input or output ratio, you find it by dividing the input by the output

in other terms, Gain can be classed as a volume

[rob mini]

sorry mate but gain can never be classed as a volume control. admittedly the volume does go up with more gain but if the gain is set at a higher voltage than the Pre-outs deliver the signals to the speakers will be clipped. so...


Clipping When the signal is 'boosted' such as turning the gain up too high or turning up the bass knob on the headunit which delivers a signal with bits missing off it known as clipped signal

[AlexM]

Could you explain impedance more? Is it better to have a lower number like 2Ohms or higher like 8ohms. And why does an amp handle more power at lower figures?

Could you explain speaker wire too. What does all this stuff about gauges of wire mean? Is 0gauge wire good or bad? what applications are different types used for?

You haven't mentioned class D amplifiers, and these tend to be the ones i see the most. Can you give some examples of matching different amps to different speakers.

thanks.

[si89]

Could you explain impedance more? Is it better to have a lower number like 2Ohms or higher like 8ohms. And why does an amp handle more power at lower figures?

Could you explain speaker wire too. What does all this stuff about gauges of wire mean? Is 0gauge wire good or bad? what applications are different types used for?

thanks.

When speaker units run in parallel have a nominal impedance of 2 or 4 Ohm, then the amp can deliver more current to the units because there is less resistance in the load. The problem is if the amp can deliver more power then the circuits in the amp get VERY hot and therefore can burn up (blow). A lot of amps (more expensive normally) will drive a 2 Ohm load. But make sure you find out first. More common in car amps than power or domestic amps.

Nominal impedance because a 4 Ohm driver could actually have an impedance of any where between 2-50 Ohm or more depending on frequency)

Parallel/Series
This is how you wire speakers up. Normally to achieve a particular impedance.

Parallel:
Connecting the amps positive output to two or more speakers positives and the same with the negative connections

Series:
Connecting the amps positive to one speakers positive then from the same speaker connect the negative to the next speakers positive then that speakers negative to the amps negative.
(This would be much easier to explain with a pen and paper )

If you connect in parallel you will half the impedance every time you add a speaker.
In series you will double the impedance.
E.g. two 8 Ohm drivers in parallel = a 4 Ohm load
Two 8 Ohm drivers in series = a 16 Ohm load

Phase.
Making sure all speakers polarity are the same is very important. if you had two subs in normal reflex cabinets in the boot and the polarities where different then each sub would be creating compression in the opposite way there fore to some extent cancelling each other out (not completely but you'll know if their not rite)


Another FAQ with car sound systems is why when you sit in the car does the bass sound so loud. And no this isn’t just because you have the sub volume to high. A theory called the cabin gain. Simply when a low bass note is produced from the sub in the car lets say 50Hz the sound wave is roughly 22.5ft (speed of sound divided by frequency) witch means the sound wave is longer than the space you are sitting in. this sound wave basically bounces around in the car making the sound louder.