Car Audio Questions.. Answered

[Deutscher]

Thought I'd try and help some people out with some questions.
If I have anything wrong let me know.

Speaker Sensitivity
A sensitivity rating tells you how effectively a speaker converts power (watts) into volume (decibels). The higher the rating, the louder your speakers will play with a given amount of amplifier power. Sensitivity is often measured by driving a speaker with one watt and measuring the loudness in decibels at one meter.

For example Hertz HKS 165.

Power Handling: 125rms (not 250 which is PEAK!)
Sensitivity: 92dB

1watt @ 1meter = 92dB
2watt @ “ = 95dB
4watt @ “ = 98dB
8watt @ “ = 101dB
16watt @ “ = 104dB
32watt @ “ = 107dB
64watt @ “ = 110dB
128watt @ “ = 113dB

At 128watts your speaker will be producing 113dB @ 1m. It does not mean that the speaker will sound clean at this volume.

Active System:
Head Unit --> Crossover --> Amplifier --> Speakers

Passive System
Head Unit --> Amplifier --> Passive Crossover --> Speakers.

Advantage of Active: Better Tuning capabilities, Full power to speakers, Time-alignment.
Disadvantages: More expensive, Time Consuming.

Ohms
Ohms is resistance. Most common speaker ohms are: 8ohm (generally home audio), 4ohm (car audio), 2 (Subs and few speakers) & 1ohm (Subs). With amplifiers, for Example Boston Acoustics GT2300 - 300 watts x 2 @ 4ohm, 500 watts x 2 @ 2ohm, Bridge 1000 watt x 1 @ 4ohm, Bridged 1400 watt x 1 @ 2ohm. The fewer the ohms the more current passes. When halving the impendance, the speakers dampening factor also halves - with a lower dampening factor it affects the ability of the amplifer to control the speaker.

Amps:
Class A/B Amps- A Class A/B amplifier uses two amplifying devices (transistor or vacuum tubes) over the entire 360-degrees of the amplification cycle, one for the positive half of the waveform and one for the negative half of the waveform. A Class A/B amplifier is also known as a push-pull amp. Or pretty much, Class A/B amplifiers are generally Speaker amps.

Class D Amps- Class D amplifiers work by generating a square wave of which the low-frequency portion of the spectrum is essentially the wanted output signal, and of which the high-frequency portion serves no purpose other than to make the wave-form binary so it can be amplified by switching the power devices. Generally Class D amplifiers are for Subwoofers - these amplifiers are larger in size compared to the A/B and also produce more watts. Generally Class D amplifiers are mono blocks (1 channel).

When looking for an amplifier to power your speakers, I’d recommend at least 1.5x -2x the power of the speaker for the amplifier, this will leave headroom so the amp doesn’t continually play at maximum output and distort or burn out. Example, TRC6N (200rms at 4ohm), I’d look at an amplifier that can produce at least 300rms at 4ohm.

Rear Speakers:

Ask yourself this.
When you go to a concert (this is what we are trying to achieve - Live music), do you:
A. Have your back to the stage, looking at the back wall, & listening to the bouncing sound waves hitting against the back wall.
B. Face forwards and listen to the band INFRONT of you - Do you ever see speakers behind you? Unless it’s for rear fill i.e. surround sound.


Fader on your Head Unit, if the HU's fader is turned toward the rear (amplified) speakers; the image will be from the rear of the vehicle which is generally undesirable. As a driver you are closest to the front speakers therefore the front speakers are the most important for you. If you use the Fader to turn down the fronts, you might as well have save some money by buying cheaper speakers that aren’t as loud because you’re reducing the full potential of the speakers. Rear speakers are not worth getting; your money is better spent on anything else: Better Fronts, Dynamat, Amp, or Head Unit.

Parallel v Series
Parallel
Load impedance drops when speakers are wired in this fashion. The more speakers you wire in, the lower the impedance is shown.

1/R = (1/R1 + 1/R2) therefore R=R1 x R2 / R1 + R2

Example: You want to run 2 subwoofers on 1 amp, if all speakers have the same impedance; 4ohm subwoofers.

R= 4x4 / 4+4 = 16/8 = 2ohms.

Series
When speakers are connected in this fashion, load impedance increases – the more speakers, the higher the impedance. SPEAKERS SHOULD NOT BE WIRED THIS WAY.

R = R1 + R2.. etc

Example: If both of the speakers have an impedance of 4 ohms, the total impedance will be 8 ohms. In a series connection, you simply add the individual impedances.

Subwoofers

A 8" or 10” will give you much tighter bass than a 12” or 15". The response of the 10" are much quicker than those of say 15". 15" subs can also sound flabby, for example the Orion HCCA154.

8" subs won't produce 30-40Hz hip-hop bass lines at full volume but they will work fine for rock and jazz.

However, you can sacrifice a little low end and still get great SQ with an 8" or 10".

15" can produce very low frequencies, & the larger diameter pushes more air. If your after SPL some good 12" or 15" in a Ported enclosure is the way to go.

Ported v Sealed
I’m not going into details here. Generally speaking - Sealed enclosures are aimed for SQ subwoofers while Ported enclosures are aimed at SPL subs.

Coaxial v Component
Components or Splits typically are generally 4”-6.5” for the woofer and 1” tweeter and also a passive crossover. Coaxial speakers have the same dimensional with a tweeter mounted on. Splits allow you to move the tweeters away from the woofer for example onto you’re a-pillar while the coaxial tweeter is fixed to where the woofer is located.

Generally Components are more expensive than Coaxial and are the better choice for your Front stage, IF you do want rear fill, stick some Coaxials in.

Dampening Factor

The value of the damping factor between a particular loudspeaker and a particular amplifier describes the ability of the amplifier to control undesirable movement of the speaker cone near the resonant frequency speaker system. A high damping factor indicates that an amplifier will have greater control over the movement of the speaker cone.

Filters

High Pass Filter (HPF) is a feature that allows the user to keep low frequencies from playing through full-range speakers.

Low Pass Filter (LPF) is a feature that allows the user to exclusively designate lower frequencies to a subwoofer. Once the LPF has been set at a specific cutoff point, all frequencies lower than the cutoff will be passed.

Band Pass Filter (Band) is the combining of a HPF and a LPF into a single filter.

2way vs. 3way Components

3way Components - You have 3 sets of speakers & crossover. A 3way system will have greater SQ than a 2way system (If good time spent tuning); Speakers: 6-8” Mid, ~4” & Tweeter. Advantages: Better SQ, Disadvantages: Cost more than 2way, harder to install, harder to tune, if going active more amps.

2way Components - You have 2 sets of speakers & crossover. The advantages of a 2way system is the ease of installment/tuning and also less costly than 3ways. 2way components are generally 6-6.5” mids and a tweeter. Typically 2way systems are more than adequate for most audio lovers.

SPL Subwoofer

A Subwoofer with high power capability (RMS), high XmaX (Excursion), will net good SPL results when combined with a proper box design. Enclosure size, design, Tuning, and Port area are very important to maximising your SPL output.

Not best SPL sub, but the:
Orion HCCA154 - RMS 2000, Xmax 30.18mm, Vas 2.82 cu ft, Qts 0.54, Fs 30.02Hz. Here is a clip, watch the excursion go! http://www.youtube.com/watch?v=5JRUzBDPXnw

Edit: Forgot to mention, some information is c+p'd and other information is how I know it to be. I am still learning car audio myself. Also some things are personal opinion. I wrote this up for a mate because he was going to buy crap from JB Hi.

[StoneX]

Well done on going to the effort of trying to help people, but it appears you've taken that from a bunch of different sources and some of it isn't correct.

Anyway, people are lazy, they don't search, all the questions relating to these answers will continue to be posted as new topics

[Deutscher]

Well done on going to the effort of trying to help people, but it appears you've taken that from a bunch of different sources and some of it isn't correct.

Anyway, people are lazy, they don't search, all the questions relating to these answers will continue to be posted as new topics

That is correct. I was in a rush and didn't write that some info was c+p'd while others came from my head from my understanding.

I was writing this up for a mate because he had no clue. But this was from my understanding of the stuff anyway, I'm still learning myself.

Could you, if you have time, tell me which parts are wrong and I could fix em up?

Edit: Is it the Series/Parallel wiring? Cause if its that I dont think I understand it haha.

[StoneX]

I don't have time to correct everything so I'll just point out what is incorrect.

- Lower impedance doesn't mean more distortion.

- Class D amplifiers are made for full range speakers too, not just subwoofers.

- Speakers shouldn't be connected in series.

- Subwoofer diameter isn't always an indication of how "tight" the bass is. That section isn't wrong, but it's confusing. The speaker's motor strength influences the "tightness" much more.

- Same with the sealed vs ported section... Not wrong but not right either. Ported is quite often used for SQ setups to give a flatter response over a specific frequency range.

Not sure if you've read this site but it has quite a lot of electrical info which relates to the speaker wiring sections.

[Deutscher]

I don't have time to correct everything so I'll just point out what is incorrect.

- Lower impedance doesn't mean more distortion.

- Class D amplifiers are made for full range speakers too, not just subwoofers.

- Speakers shouldn't be connected in series.

- Subwoofer diameter isn't always an indication of how "tight" the bass is. That section isn't wrong, but it's confusing. The speaker's motor strength influences the "tightness" much more.

- Same with the sealed vs ported section... Not wrong but not right either. Ported is quite often used for SQ setups to give a flatter response over a specific frequency range.

Not sure if you've read this site but it has quite a lot of electrical info which relates to the speaker wiring sections.

Cheers StoneX.
I'll further my research and update my original post.
Why do you say Class D amps are for full range speakers aswell? Aren't Class D amps mainly mono's?

[2LOUD2OLD]

they make full range class d amps now, so no they aren't mainly mono

[Deutscher]

they make full range class d amps now, so no they aren't mainly mono

Ah k. I've just been searching for some. Not a lot out there though.
The Alpine PDX4.100 is a Digital Class D 4channel.

Edit: According to SonicElectronix (I know some people aren't a fan but they got a good setup on their webpage), Class D amplifiers that they sell are:
196x Mono Block
9x 4-Channel
2x 2-Channel

[Philthy]

Ah k. I've just been searching for some. Not a lot out there though.
The Alpine PDX4.100 is a Digital Class D 4channel.

Edit: According to SonicElectronix (I know some people aren't a fan but they got a good setup on their webpage), Class D amplifiers that they sell are:
196x Mono Block
9x 4-Channel
2x 2-Channel

I thought all of Jaycars amps were Class D?

[Philthy]

How did I manage that...nothing to see here

[Deutscher]

I thought all of Jaycars amps were Class D?

The Precision 5 channel is a full range class D. But the rest don't appear to say anything according to the website.

[bezz]

Nice write up mate, lots of good points and a lot of frequently asked questions answered really well.

If you want to be pedantic, resistance is only 1 part of a speaker's impedance. In the frequency domain (ac, what is being output by the speaker) impedance takes into account not only resistance, but also capacitances, inductances etc, as well as phase differences. Its really not that important, and I wouldn't bother looking into it unless you like complex numbers, but try to stick to calling it impedance and not resistance if you want to be 100% correct in your terminology.