50 replies to this topic

[Rob Himself]

Background

I'm not an expert. I'm not in the industry. I'm just a well-seasoned and reasonably experienced enthusiast.

I've seen so many threads repeating the same question, so I'm aiming to answer some of them here.
If I do come across as ultra-basic or patronising; forgive me. I'm just trying to write it from the perspective of a total newbie who knows nothing.

If you do have any questions - just ask! Failing that, get yourself over to talkaudio.co.uk!


Contents:

• Background - Post 1
• Powercaps - Post 2
• Sound Deadening - Post 3
• Resistance (Ohms) - Post 4
• Power (Watts) - Post 5
• Dual Voice Coils - Post 15
• Rear Speakers - Post 19
• Setting Gain Levels - Post 20
• ICE Acroyms & Abbreviations - Post 21
• Basic Layout of a Simple Sound Setup - Post 24

Edited by Rob Himself, 27 June 2008 - 01:02 PM.

[Rob Himself]

Powercaps

Power caps are misunderstood things.

Many people believe that adding a cap will stop your lights dimming, make your system louder and add about 13bhp to your engine (...probably).

First, let's see what a capacitor is.
http://electronics.h...m/capacitor.htm

To summarise, a capacitor is similar to a battery, in that it stores electrical enegy. A good analogy used is:

One way to visualize the action of a capacitor is to imagine it as a water towerhooked to a pipe. A water tower "stores" water pressure -- when the water system pumps produce more water than a town needs, the excess is stored in the water tower. Then, at times of high demand, the excess water flows out of the tower to keep the pressure up. A capacitor stores electrons in the same way and can then release them later.

So all that caps do is store a small amount of energy, which is then released when required, the rest of the time it is charging.


When NOT to use a power cap:
If when listening to your system with engine on, a bass note hits and your lights dim and stay dim, you should not get a power cap. You should instead upgrade "the big three" - either a bigger battery (or a second battery), uprated cabling and/or a more powerful alternator.

When to use a power cap:
If when listening to your system with engine on, a bass note hits and your lights dim and return to full brightness immediately, then a power cap can help your system.


So a power cap can work in theory. But how well? Well I'm sure at some point you've used a camera with the flash on. The flash is powered through a capacitor too. But when you've just taken a photo, do you have to wait for a good few seconds before the camera does anything? Because at the moment the
flash goes boom, the circuit's 'output' (in this case converting electrical energy into heat and light energy) section increases suddenly, and the 'waiting time' is the battery recharging the capacitor.

But this is controlled by the camera's software, and limits you from taking a photo to every few seconds, as otherwise the flash would just be a measly candle flash.

But similarly, in car audio, when the current demand suddenly rises (ie: when the bass hits, to convert electrical energy into mechanical energy and then acoustic energy) the first line of defence is the amplifier's on-board capacitor bank, which smooths a lot of the draw.
Outside of this, you'll be looking at the power supply sections: battery, alternator, and your capacitor.

For those who don't know, the alternator works by being driven by the aux belt and converting mechanical energy into electrical energy, stored in the battery.

So bass hits, first few beats... power cap helps a bit. But when the stored energy depletes? The alternator's busy charging the battery, and all the battery's power is going into your amp which is making your 18" MegaBass sub and making Kylie sound like thunder.... it's not re-charging your power cap. The electricity is just going straight through it. So you'd be better off spending your money on a bigger battery and alternator.... assuming that your cabling is up to scratch.

If you're really that adamant about it, then buy one and test it... and trust me, your headlights will dim both before and after.

Rob.



PS: "But my voltmeter reads about 14 volts so it must be working isn't it!" No. A voltmeter measures the voltage across and given point in a circuit. You can stick it over your battery, across a random length of cabling, or anywhere you like - it'll still read the same. They just pop one on the power capacitor to make it look like it's doing something. What you want it an ammeter

[Rob Himself]

Sound Deadening

"Sound Deadening" isn't just "deadening sound" such as stopping the odd panel from rattling. As a starter, you've got road noise, engine noise, panel rattle, interior resonance.

The whole lot can be broken down into 4 chunks:

• Dampening
• Blocking
• Absorbing
• Isolating

Each of these requires different products, does different things and uses different techniques to do their job. Some products cover more than one of these, some don’t.



Dampening / Mass Loading

This is probably the most common approach, usually the only aftermarket approach to ‘sound deadening’ in a car. Resonance is the addition of sound energy by the reflection or vibration of, in our case, panels.
The idea of dampening is to reduce the resonant frequency of panels to below the frequencies usually played, by increasing mass.
These are often bitumen based and is where your roof/lead flashing etc comes into play. However, the best of the mass loaders are usually designed absorb vibration motion and convert it into low level heat, such as Dynamat and Brown Bread etc.

Mass loading and dampening are usually used in the car to increase clarity of the bass (in car audio) by preventing panel resonance. Whilst it may help to reduce road noise, this is not it’s primary role and is actually a bit of a side effect.

When applying to a panel, we're looking for the best contact - so any area which rings or rattles when tapped.


Dynamat Xtreme






Blocking

This is stage 1 to reducing actual interior noise from the engine & wheels. Does what it says on the tin - it blocks sound.

These products are ideally suited as they simply stop any sound from passing through them and have low resonant frequencies so reduce more low frequency energy from passing though. These products are usually available in ‘sandwich’ form where they are coupled to a closed cell foam.
Also, although not highly evident, it's worth noting that your ordinary Dynamat also has some very mild blocking aility ... wondered what that foil/alloy backing was for?!

The product use is usually a matting that helps reduce road and transmission noise for that kinda peace you only get in a German saloon. It’s best used on the floor pan, the bulkhead and the transmission tunnel.

Second Skin Motormat
http://www.a1caraudio.co.uk/images/shop/small/secondskin/s_motormat.jpg/im]



[b]Absorbing[/b]

Without meaning to go into too much technical detail, this does a very similar job to blockers, but backwards. Instead of merely stopping the road noise, it absorbs it - usually turning it into kinetic energy. Usually an thick foam, it has the added bonusof being great for stopping fixtures such as door cards, rattling against panels, such as doors, simply due to the movement of the vehicle.


[i]Second Skin Sludge - for noise absorption and vibration resistance.[/i]

[img]http://i6.photobucke...86/DSCI0021.jpg



Isolation

Lastly, isolation - again HIGHLY overlooked in car audio.. but not so much in home audio. The idea is to isolate the potential 'noise maker' from the source... so where possible, rubber bushes/minimal point of contact should be used. Not quite so applicable to this situation.




So overall, it's up to you to what extent you want to take it... I've known car audio guys to have spent £1000+ on 'sound deadening' alone. Me? Personally, I've got Dynamat Xtreme, Second Skin Sludge & Second Skin Overkill Pro all on my floor and doors. Next - bulkhead and boot.

[Rob Himself]

Resistance ('Ohmage')

Electrical resistance is a measure of the degree to which an object opposes an electrical current through it, measures in ohms.

Speakers too have resistance. (For clarity of definition, d/c circuits have resistance, a/c circuits have impedance).

The lower the resistance in a circuit, the closer it comes to short-circuiting. Think about a 9v battery and paperclip - the paperclip offers neglible resistance, and so when you complete the circuit (ie: touch the clip to the terminals) it short circuits and sparks.

Amplifiers:
Amplifiers are designed to push a current around a circuit at a designated resistance. Therefore, a 4ohm amplifier can happily power a 4ohm subwoofer.
A 4ohm stable amplifier cannot play into a 2ohm resistance, as it will be pushing too much current, get hot, and eventually shag the amp.
However, a 4ohm stable amp can play into a 8ohm resistance, as it is pushing less current so keeps cool. Unfortunately as there is twice the impedance,and so the consequential output will be half as powerful.

Often with multi-channel amps, you can 'bridge' 4 channels into 2 (ie: 1 + and 1 -) so that the amplifier 'sees' half the resistance of the subwoofer or speaker.
Henceforth, manufacturers state whether or not bridging channels is safe or not for that amp, for example:

4 x 90w @ 4ohm
2 x 90w @ 4ohm + 1 x 180 @ 2ohm

Speakers:
When you have 2 4ohm speakers wired in series, they will show an 8ohm load.
When you have 2 4ohm speakers wired in parallel, they will show a 2ohm load.

Without illustrating every single configuration, it's now a matter of matching the right subwoofer to the amplifier. This is often done by using subwoofers which have dual voice coils (DVC), although many do have just one single (SVC). JL Audio's website lists all the possibilities: http://mobile.jlaudi...php?page_id=145

[Rob Himself]

5000watt amp for £40 on eBay (or something to that effect)

Slander aside, Legacy, SPLX, TheLoudest.com and others immediately spring to mind.
Watts (which measure power) are derived from joules (which measure energy). Therefore, the more the better, surely?

9 times out of 10 - if it looks too good to be true, it probably is.

Go to any reputable car audio dealer, and instead of just 'watts' you will start seeing 'watts RMS' and then 'watts peak'.

RMS stands for 'root mean square.' Now go back to your GCSE Maths. Root and square are opposites, and mean is average. Technically, RMS is the measure of magnitude of a varying quantity. In car audio terms, RMS tells you what power the amplifier can continously put out, (or 'on average' if you insist).
Peak power is the maximum power that it can output for a very short burst of time..... and this is what those £40/5000w amps quote. And often, those are measured under unnatural conditions.



Still not convinced? Look at the fuse on the side.

Amplifiers come in 'classes' - Class A/B are (optimistically) 60% efficient, Class D are 80% efficient.
The maximum RMS 'wattage' can be calculate as:

Voltage x max current draw x efficiency

So if your amp has a single 40amp fuse, and is class A/B, then:

13.8 x 40 x 60% = 331w.

Let's have a look at this TheLoudest.com one here. (Apologies for having to download the file).

8000w it says! Ooh wow. But that's at 2ohm, max. Yet their own quotes figure is 3000w RMS - how they derived 8000w peak from that is beyond me.
13.8v (typical in-car driving voltage) x 240A (they say) x 82% (they say... we'll have to trust them) = 2715w.

Still only 2715w at a push... a far cry from the alleged 8000w, but not half as bad as some.



So next time you're looking for a powerful amp... just do some quick maths

[Brams96]

Hust thought I would add a pic or two to help with wiring configurations:
http://www.theminifo...x...st&id=57029
http://www.theminifo...x...st&id=57032

[Rob Himself]

Ta for that... though it'd be easier to save the 3 x power fuses and use a distro block!

Any more requests?

[langers2k]

Put a remote wire on the diagrams?

Maybe a quick overview of sound stages and *standard* speaker positions for mini's? Other than that, amazing work!

Oh, and will you come and sound deaden my mini!?

[HARBER07]

Just a tip (dunno if its the same for this) but as a sparky to find an RMS from a peak power, times the peak power by 0.707. To find a peak from an RMS divide it by 0.707.

[Jet_black]

What about different types of subwoofer enclosures and what they do.

[Rob Himself]

On my list I've got:

- The 'rear speakers' debate
- Subwoofer enclosures is a kettle of fish... quite subwoofer dependent too, but could try!
- Idiot's guide to a basic ICE install

[Tomf]

A guide to wiring up an amp would be good, including wire colours, etc....

Also what would be the best sort of cheap sub and amp to buy?

[Piddling Kid]

explain a bit about speaker location? this link may help someone got it off another thread sorry to owner lol

back of headunit diagram

[Brams96]

X-OVER's for component speakers explained: http://www.mtx.com/c...versFilters.cfm

[Brams96]

DUAL VOICE COILS Explained

--------------------------------------------------------------------------------

What are the advantages of dual voice coils?


The primary advantage of the dual voice coil speaker is wiring flexibility. A single dual voice coil driver offers the user three hookup choices...parallel, series and independent. In a parallel hook-up the drivers impedance will be half that of each individual coil (a dual 4 ohm speaker would be a 2 ohm speaker in parallel.) A series hook-up results in twice the impedance of each single coil (a dual 4 ohm speaker results in 8 ohms if its coils are wired in series.) Finally, you can wire each voice coil to a separate channel of your amplifier, which can be useful if your amplifier is not mono-bridgeable or if you are bridging a four channel amplifier down to two channels to run your sub.

The independent wiring application is the one that brought about the need for dual voice coil speakers in home audio. Unlike most good car amplifiers, home amplifiers and receivers are typically not mono-bridgeable. For this reason, dual voice coil woofers were developed so that a subwoofer or center speaker could be driven from the left and right channels of the average stereo home amp/receiver. Since sub-bass frequencies are hard to localize, the dual voice coil subwoofer allowed sub-bass reinforcement within one cabinet and one speaker. This cabinet could be placed inconspicuously in a corner or along a wall of the listening room, with the obvious benefits being space-efficiency and lower cost than two independent bass cabinets or a larger cabinet with two subs in it. Many popular home subwoofer / satellite speaker systems still use this basic configuration


Does It Matter How The Voice Coils Are Wired To Each Other?

A dual voice coil speaker will behave exactly the same way whether it is wired with its coils in series or parallel. The only thing that changes is the impedance that the amplifier sees. This means that enclosure calculations are constant for dual voice coil woofers no matter how the coils are connected to each other, as long as both are connected.
A common misconception with regard to dual voice coil speakers is the assumption that nothing changes if you power only one of the voice coils. With only one coil hooked up, a dual voice coil speaker will suffer a loss in reference efficiency of about 3dB (only half the coil windings are being energized) as well as a significant shift in its Thiele/Small parameters. This renders any enclosure calculations inaccurate unless you remeasure the speakers parameters with only one coil hooked up. Failure to account for the different parameters of a dual voice coil speaker with only one coil powered can result in very poor performance.

NEVER POWER JUST ONE VOICECOIL !


How are dual voice coil speakers rated for power handling?


A dual voice coil speakers power handling is typically specified by manufacturers for the whole speaker. This means that a 250 Watt dual voice coil driver is designed to handle a total of 250 Watts whether the coils are wired independently, in series or in parallel.

** COPIED FROM [url="http://www.floridaspl.com/forums/showthread.php?t=510""]http://www.floridasp...read.php?t=510"[/url]

Edited by Brams96, 28 April 2008 - 02:14 PM.