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A Few Audio Related Pointers....

13K views 15 replies 2 participants last post by  TINTIN 
#1 ·
Firstly

PLEASE DON'T POST UNTIL THIS MESSAGE IS DELETED THANKS

A few basic questions answered whilst I'm not busy.
When installing amps;

1, How do I know what size power cable to run?

The answer in basic terms is;

Add up the on board fuses on each amp you are going to use, say your mono amp (for the sub/subs), is fused with 2x 40amp fuses,(80amps in total), and your second amp,(for the fronts or fronts & rears), is fused with 2x 30amps,(60amps in total), then you can work on the assumption your maximum current draw is going to be 80+60=140amps, so with this set up you would require 0awg power & earth cable.

2, How do I know what size fuses I require?

The answer is;

The actual cable rating denotes the required fuse rating, you must remember you are fusing the cable and not the amp, as an example;

If running a 0awg power cable from the battery to the boot then the required fuse should be higher than the load,(current draw from the amps etc), but lower than the cables rating.
So with a max current draw of 140amps, and a cable rating of 250amps, you would use a fuse of 200amps. This fuse should be mounted as close to the battery as possible.

3, Why do i get engine whine through my speakers?

The main cause of alternator whine is poor earthing, you should always select a good earthing point, I recommend the boot floor, be careful when drilling to avoid the fuel lines/tank, electrics & brake pipes, clean the area back to bare metal and use a nut & bolt. You should avoid using, seat belt anchor points, rear light cluster earthing points, rear seat hinge bolts.

4, Where can i mount my amplifier?

When mounting your amp/amps I would recommend you avoid placing them in direct line with your sub, a sub firing directly into an amp will eventually cause damage due to excess vibration. You should also avoid mounting amps on the outer faces of the sub enclosure, this will also expose the amp to excess vibration.
You should also avoid mounting the amp upside down or at any angle beyond the vertical,(on rear seat backs for example), this is because of the heatsink. The amps heatsink is designed so that when it heats up, the warmed air rises and draws in cooler air from the ends, this cooler air then cools the heatsink, becomes warmer air and rises away and so the cycle continues, however if the amp is mounted incorrectly the warmed air rises into the amps internals and can't escape, because it can't escape it can't pull any cooler air in, and so the amp runs hot, and can cause the amp to trip into thermal protection.

5, When installing multi amps can I daisy chain the remote switch on lead.

If using two amps then this shouldn't be a problem, if however you require your remote lead to operate on say, two amps, a sound processor, dvd unit, etc etc, then I would recommend the use of a relay, using the remote lead as the switching supply.

6, Fed up with amps now so lets move onto headunits and distortion;

1, The average head unit is fused at 10amps, these 10amps at any one time are supplying;
cd laser
cd drive motor
cd laser carriage
unit illumination
flashy graphic display panel
and eventually the internal amplifier

When playing a full range signal the internal amplifier will require more power than it would if it were say playing a signal high passed at 100hz, so to translate this into basic terms, the more bass you ask your head unit to play, the more likely it is to distort,(this is due to voltage drop within the head unit, not poor speakers).

A simple test;
Play a dynamic cd, gently increase the volume until you can hear distortion, now lower the bass settings on your head unit and the distortion will stop, now increase the volume again, it should play at an increased volume without distortion.

A speaker can only reproduce what it receives, if it receives a good strong signal, it will reproduce a clean clear sound, if it receives a weak signal thats ragged it will reproduce poor ragged sound,(distortion). The higher excursion that is required for lower frequencies demands a stronger signal, (which is why sub amps have higher rms ratings), and unfortunately head units just don't have that kind of power.

When selecting a new head unit you should take into consideration exactly what you require from it. In most cases if you are fitting a head unit and using it to drive stock speakers you will notice an improvement in sound quality and output level, however if you decide to upgrade the speakers at the same time you may find its not as loud or warm, (bassy).

Most people when they detect distortion in the stock audio system run down the local audio outlet and purchase uprated speakers, then discover that it still doesn't sound any better, so they then assume the problem is that the head unit is still too powerful for the new speakers, when in truth the opposite is correct, the head unit is not powerfull enough.

Pointers on speaker selection;

Speakers being driven by a headunit without a sub installed

These should be rated at around 20watts rms, either component or coaxial, capable of playing down to around 45hz with a sensitivity of 93db+.

Speakers being driven by a headunit with a sub installed

These should be rated at around 30watts rms, preferably components, capable of playing down to around 70hz with a sensitivity of around 91db+.

Speakers being driven by an external amp without a sub installed

These should be rated at around 70watts rms, definitely components, capable of playing down to around 45hz with a sensitivity of 90db+

Speakers being driven by an external amp with a sub installed

These should be rated at around 90watts rms, definitely components, capable of playing down to 70hz with a sensitivity of at least 89db+

To supply rearfill, for those that want it, should be done using small coaxial speakers.

Now to the dreaded 6x9 debate.

These should be used where the fitting of a sub is not desired or possible. They should not be fitted in parcel shelves with their cones sharing the same air as a sub or subs. If you decide you want 6x9's in the back they should be fitted so that you can enclose their baskets to afford them protection from the sub/s.

As previously stated a speaker reproduces sound according to a signal it receives, to reproduce that sound correctly the speakers cone needs to react naturally to the signal, but when you have a sub firing massive shock waves through the boot it reacts to those shock waves causing poor sound reproduction. You can actually see this happen if you have 6x9's mounted in a shelf above a sub, all you do is disconnect the negative speaker wire off each 6x9 speaker, shut the hatch and play your music, watch the 6x9's cone, it will pulse with the beat, the louder you go the further it will move. This movement affects sound reproduction, causes the voice coils to work harder, which causes heat build up, which in turn promotes premature speaker failure.

When fitting 6x9's into a car, if they are fitted correctly, and driven by an external amp they are a decent alternative to a sub, but when driven with a headunit they sound crass and harsh.

7, Sound deadening on the cheap

When fitting a sub into your car I would recommend sound deadening the following;
1, boot floor
2, rear quarter panels
3, rear hatch panel
4, boot sides

The difference between a car thats deadened and a car thats not is truly amazing, it seems so much warmer and louder, all the sound thats lost through thin panels is held in the car, thin panels no longer ressonate and so it sounds cleaner.

When doing budget jobs I always use,"wickses high tack flashing tape", its not as good as dynamat or similar but it certainly makes a difference at a fraction of the price.
I would also recommend doing the front doors, its easy to do this when fitting new speakers, just cut tape into small strips and apply it to the outer panel through the holes in the inner panel. When you are satisfied with the outer panel you can then do the inner panel taking care not to foul any levers or operating rods, (for best results you should cover all the access holes, effectively sealing the door cavity).

When installing speakers always try to use mdf baffles, and where the baffles join the mounting surface seal it with grip fill or similar.

Hope you have found the above useful, if not i hope you found it interesting lol.

8, The art of speaker & amplifier matching

Firstly i should point out that when selecting speakers or amplifiers you should ignore max output figures, they are misleading and rarely accurate. You should however take note of the rated figures,(commonly noted as RMS figures).
The RMS figures refer to the average output that the unit can output continuously.

Secondly, I should point out that recording levels vary from source to source, so for example a 50hz test tone recorded at 0db,(the highest possible level), will play extremely loud, where as the same test tone recorded at -3db will play at around half the volume. This sliding scale can become extremely confusing so I'm not going to go there lol.

So in effect a 50watt rms amp will deliver 50watts rms when playing a test tone recorded at 0db, but will deliver much less if playing a test tone recorded at -3db.

If you were to represent a test tones rms output on paper, it could be shown as a straight horizontal line.
If you were to represent music in the same manner it would be a series of peaks and dips, now because the maximum recording level is 0db, the peaks would be recorded at 0db, everything else would be recorded at a lower level, giving a much lower average output, (or rms output). So, because of this, when selecting equipment you should bear in mind what you will be playing.

So I always take note of the speakers rms figures, then select an amp that is rated at least 25% higher, so if I was selecting a mono amp to drive a sub, I would check the subs rms figure, say its 300watts rms, I would then look for an amp capable of delivering at least 375watts rms into the correct impedance, the same applies to all amps and speakers. This is referred to as,"headroom".
 
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#2 ·
GENERAL ADVICE ON POWER ISSUES

Do I need a powercap?
The general opinion held by 95% of the Halfords, Motorworld, Motormania etc etc brigade is that for every 1000watts rms you require at least a 1 farad cap to avoid dimming lights, this is rubbish. By its very nature the power supply in any car fluctuates up and down and in some instances this can affect sound quality,(I'm talking competition level sq here), in these applications powercaps can be used, not to bolster, but to smooth out, the power delivery.

Dimming headlights.
This is caused by voltage drop in the power supply, by adding an extra item that requires constant charging,(a powercap), you are simply masking the problem for a few seconds, as soon as the cap is discharged it must recharge, placing yet another strain on the cars charge circuit. If you were to connect a headlight bulb up to a 1 farad cap, how long do you believe the bulb would be illuminated for? seconds, minutes, or maybe hours,(its actually seconds).

Whats the best way to avoid dimming lights?

1, Turn the stereo down.
2, Turn the lights off.

Or;

Read on.

The most logical place to start is the battery, how many of you out there have simply purchased an amp wiring kit, ran the power cable through the car, connected it up and thought, job done. well unfortunately it isn't. A statement that is true with all electrical circuits is;

YOU CAN'T TAKE OUT, WHAT YOU CAN'T PUT BACK IN.
To explain in basic terms;
Imagine a tank of water,(your battery), this tank is being emptied using a hose pipe,(your audio power cable), the same water is running back into the tank,(your battery), through a drinking straw,(your cars standard battery earth cable), now obviously the water,(current), will only flow as fast as the smallest pipe will allow,(in this case the drinking straw), so a bottleneck develops where the hose,(audio power cable), meets the drinking straw,(stock vehicle's battery earth lead).

So although you are running correctly sized and fused power cable, the circuit will be restricted by the battery to chassis earth cable.

So in the quest for better power follow this advice;


1, Always fit an extra earth to your battery,(at least the same size as your new power cable).
2, Uprate your alternators batt charge lead,(reduces resistance and gives a slight improvement).
3, Uprate the alternators earth if fitted.
4, Uprate the engine/gearbox to chassis earth.

HTH someone.

A little advice for sub enclosures;

There are a few ways you can improve a subs performance in any given enclosure.

1, Try adding a 1" thick layer of fibrous material,(fibrefill, pillow stuffing, loft insulation), to all internal faces of a ported enclosure, this will dissipate the soundwaves bouncing around inside the box, as previously stated pressure waves reacting with a speakers cone can cause poor quality and heat build up in the coils. With this layer added the sub will handle more power and give cleaner lower bass.

2, Try loosely filling a sealed enclosure with fibrous material,(for this i use loft insulation), this will make the sub behave as if its in a larger enclosure, with the added bonus of higher power handling, a sub mounted in an enclosure like this will play lower and with more power.
 
#3 ·
Lets cover basic amp setting up by ear.

OK, going to assume I'm setting up a system comprising off;

A 4ch amp driving front speakers off the front ch's and a sub bridged off the rear ch's.

Basic settings to start with;


headunit;
bass---at "0"
treble---at"0"
any factory preset eq's---off
any added bass circuits---off
graphic or parametric eq's---flatline at"0"
any media expansion circuits---off,(these are used to improve mp3 playback quality).
bass boost features---off

amplifier;

front ch's;
crossover switch---set to high pass
gain control---set to min
freq control---set to approx 100hz
stereo/mono switch---set to stereo

rear ch's;

crossover switch---set to low pass
gain control---set to min
freq control---set to approx 80hz
stereo/mono switch---set to mono
bass boost circuitry---set to min or off

Now your ready to begin;
To avoid problems associated with your headunit running out off power and supplying a clipped signal you should select as your max volume a point approx 20% below max, so if using a scale that goes from 0 up to 35,(like Alpine's), you should treat say 30 as your max "safe" volume.

http://www.realmofexcursion.com/downloads.htm

So go somewhere where your not going to offend people, select your headunits safe volume and play a 1khz test tone,(you can download it from link previously supplied), on repeat.
On your amp's front settings adjust the gain control upwards until the test tone changes, this change is where your amp is clipping, now back off the gain slightly so the tone is playing as normal again, thats the front's gain set

Now play a 50hz test tone,(again downloaded from previous link), and adjust the rear ch's gain in the same manner, as you hear distortion back off slightly, thats the rear's gain set.

Now play a dynamic cd that you are familiar with to adjust the crossover freq's to your taste.

When complete you should have a basic setting that you can tweak to get it as you want it, this won't take 10min's, it will probably take day's.

To balance the bass to your front end you should always alter the highest one, so if your fronts drown out your sub, then lower the gain on the fronts, if the sub drowns out the fronts, then lower the subs gain control.

You should bear in mind that you have set the gains using a source recorded at 0db, so if you will only be playing music you could in theory increase the gains slightly to give a higher output.
 
#4 · (Edited)
A few basic facts regarding OHM'S LAW

The ohm is a measure of impedance, this can become confusing so i will keep it basic.

If an amp is producing 50watts rms into 4ohm's, it will produce 100watts rms into 2ohm's, so if you halve the impedance,(ohm's), the output doubles.

The same amp at 4ohm's is drawing say 25amps current, at 2ohm's its draw will also double to 50amps, so if you halve the impedance, the draw,(power needed), will double as does the output.

If wiring either a dual voice coil sub or two or more subs in series you would add the ohm's value off each coil together, for example;







If wiring the same subs in parallel, you would halve the ohm's value





When using multiple dual voice coil subs it's perfectly OK to configure ALL the coils in 'parallel' or 'series' then wire up ALL the subs in 'parallel' or 'series'....

So if all the coils are configured in 'series', then all the subs are wired to an amplifier in 'parallel', then that's perfectly fine.....But if you should try mix & match your asking for trouble....

Here's a quick pic denoting my subs wired in series & parallel to achieve an ideal overall 4ohm impedance;

Coil 1 = A + A
Coil 2 = B + B

 
#5 ·
CAUTION; When working on a system you should pay heed to a few safety tips to avoid possible system damage;

If any part of the boot power supply is to be disconnected, (Earth or Live), then always follow these easy steps to avoid possible head unit damage).....

1, With system switched off....
2, Disconnect all RCA leads from any amplifier which is/has been in use....
3, Reconnect all RCA leads last....
4, When fitting any amplifier you should ensure you wire it up in the correct order;

Connection sequence;
1, Speaker wires
2, Batt +ve feed
3, Amplifier earth
4, remote turn on
5, Double check all connections, fit power supply fuse, Switch system on and check amp powers up.....
6, If amp powers up OK, then switch system OFF....
7, Connect all RCA leads....

To disconnect an amp;
1, System OFF...
2, Remove RCA leads, remove power supply fuse....
3, Remove amp remote
4, Remove amp earth
5, Remove amps batt +ve
6, Remove speaker wires

Simple Rule---RCA leads should be connected last & disconnected first....
 
#6 ·
More Useless Information Regarding Amplifier Gain Controls

Amplifiers have 'gain' controls so the input signal voltage can be adjusted to permit the amp to achieve full output power, if the gain is set too low, then the amp won't achieve full output, if the gain is set too high, then the amp will reach full output too soon & signal 'clipping' will occur....

The RMS voltage of a 'clipped' signal is much higher than that of an 'unclipped' signal, so heat generated from a 'clipped' signal is much greater than that of an 'unclipped' signal.....Essentially, 'clipping' = BAD NEWS....

A 'clipped' signal can be heard as distortion, basically as the speaker cone reaches full excursion, (max power), it simply stops and sits at full power for the extended time spent at full voltage, (extended duration at the peak of the wave form), whilst the cone is stationary heat build up in the coils is greatly increased, (in basic terms, the coil acts in a similar fashion to a heater element)....

This would be easier to explain using a sketch.....You should at first realise that a speaker receives voltage through both the negative & positive terminals, positive voltage pushes the cone outward, negative voltage pulls the cone inward....an amplifier has two voltage rails, ones positive, ones negative....once the max output voltage of these rails is achieved, then clipping will occur, (no increase in volume can be had once an amp is clipping although RMS voltage will increase).....



KEY;
Trace A & B = Amplifier running at full volume, (GAIN SET CORRECTLY)
Trace C & D = Amplifier running 'clipped', (GAIN SET TOO HIGH)...
Trace E & F = Amplifier running below full output, (GAIN SET TOO LOW)...

If you check the peaks of TRACES C & D you will see the time or duration spent at full voltage is much greater, (the wave form is squared off or 'clipped'), this is where the heat generated is at its greatest.....
 
#7 ·
Background noise/Alternator whine....

To sort this you need to actually locate the source of the noise....

Is the noise only present with the engine running....

YES---Then its going to be a ground loop scenario, in 90% of cases its poor amplifier earthing thats the root cause....

Amplifiers should be earthed to the boot floor using good quality connectors, the earth site should be cleaned back to bare metal and once tightened treated against corrosion....

NO---Then chances are its down to a faulty item.....

With system switched OFF....

Remove the RCA leads from the affected amplifier....

Switch system on and play as normal....is the noise still present??

YES---Then its an amplifier or associated wiring fault, (Speaker cable pinched & shorting?? Speaker terminal shorting to a door panel?? etc etc)

NO---Then the fault is before the amplification stage, carry on...

With system switched OFF...

Refit the RCA leads into the amp, remove the head unit from the dash and remove the RCA leads from the back of it....

Switch system on and play as normal....is the noise still present??

YES---Then its a faulty RCA lead, simply replace the affected lead.....

NO---This would indicate you maybe using a PIONEER head unit which at some point has been connected up or disconnected incorrectly which has caused an earth track fault,(it can affect other brands, but the main culprit is PIONEER)...


To get round this fault,(it's not a repair, it's simply a quick fix), you should do the following;

Run a fused direct live,(20amp cable fused at 15amps), from the battery to the head unit,(essentially bypassing the audio looms constant live). you should leave in place the ign live so the unit operates as it should on the ign...

Run the head units earth,(again bypassing the stock audio loom), direct to the cars chassis,(use 20amp cable & ensure you select a good earth site and clean the area back to bare metal), the condition of this earth site will affect the success of this quick fix...

You will now need to earth the RCA plugs outer sleeves to the head units chassis,(i usually use the head units rear support screw location), this fix should solve most cases, but on occasion it can be necasary to also earth the head units mounting cage to the cars chassis....
 
#8 ·
CABLE ROUTING

POWER CABLE----This should take the most direct route possible, (this keeps cable length to a minimum), you should avoid sharp bends because this can affect voltage and current flow, (creates a point of high resistance and heat build up), all connections should be tight and no copper should be showing....

POWER CABLE & RCA LEADS----Most will state these should be kept apart, this is correct if dealing with AC, but we're not....A cars supply is DC so any interference experienced will be from either a ground loop, (caused by poor earthing), or a faulty item, (RCA lead or electrical appliance)....

I've ran signal cables and power cables together many times, with no issues to date, (but I don't use RCA leads from the local pound shop).....
 
#9 · (Edited)
Thought I would add a power cable chart, this chart is made up taking into consideration voltage drop, so in basic terms each cable will safely carry more current, but at the expense of voltage.
all cable lengths are in meters....

Your new power cable should be fused as close to the battery as possible....





So if your max draw is say 80amps and your cable length is say 4 meters you will require either 3awg or 2awg cable. you could actually use 4awg also but you will suffer some voltage drop.

A 0.5v drop over the full length of your main feed, (batt to boot), should be considered acceptable.....
 
#10 ·
OK, I have seen a number of cars that have split charged boot batteries. the vast majority,(in fact all but one), have been wired correctly but with woefully inadequate cabling/fusing.

Apparently, the main culprit seems to be the,"over the counter split charge kit".

Thought I had best offer some advice in the hope it saves anyone else being caught out!!

In these kits you get a 180amp split charge relay, so by definition the suppliers are expecting,(quite correctly), large current surges/draws. but for some reason these same suppliers include either 10awg or 8awg power cable with 30amp fusing:eek: ..

In the interests of safety I always follow the basic rule that all power cables should be capable of handling the max possible current draw, (which includes the battery connecting cable), and fused accordingly.

Had a young lad a while back who purchased one of these kits from a reputable local I.C.E. outlet along with a JL AUDIO 12W7 and JL AUDIO 1000/1 amp, he had fitted it correctly and duly visited the local haunts of the young boomers. He played his system for around 25 mins at moderate volume with no issues. When it came to driving home he simply started the car and drove away....his system shut down halfway home because of a flat boot battery. The poor kid thought he had toasted his system because every time he replaced the 30amp fuse in the split charge circuit, it blew as soon as he tried to start the car...

The problem is, on initial start up of the car, not only does the alternator try to charge the rear battery, so does the fully charged starter battery,(I have seen 200amp breakers trip on startup before ), so a puny 30amp fuse coupled with cable rated at 30amps over 5mtrs doesn't stand a chance .

So, if there's a slight possibility of your system being used when the car is not running, use at least 4awg power cable fused at 80amps,(you can stretch this to 100amps if needed), if you will definitely be using your system with the car not running, then 0awg is really your only option,(but do not exceed the relays ampage with power cable fusing)....

The split charge relay should be mounted inside the car to protect it from the elements...

Here's a quick sketch which should help you avoid this issue...

 
#11 ·
A Few Interesting Points Regarding Amplifier Output in Relation to Audible Volume Level.....

Lets say your currently using a mono amp with a rated output of 2.5kw rms....We know this figure was achieved playing a 0dB sine wave at 14.4v.....

Lets assume playing a 50hz sine wave in your car gives a reading of 147dB, just how does this actually break down into understandable figures.....

Firstly you should understand that playing music through the same amplifier at the same head unit volume will yield much lower actual output power, but just how much does rms wattage drop???

You should also understand that doubling amplifier output doesn't make a system twice as loud to the ear, to achieve double the volume to the ear requires an increase of 10dB, (or approximately 10X the amplifier output).....

The difference in volume level to the ear between a ported enclosure and a sealed enclosure, (playing the same track at the same head unit volume), is noticeable, but not as large as one would think dB wise.....On average it's around 3dB, or the same as doubling the amplifiers output power.....

Here's a simple to understand table based on my cars system.....

Amplifiers output is 2.5kw rms into a 4ohm load, but how does that break down.....

2500w rms = 147dB, (test tone at full volume)....
1250w rms = 144dB, (music at full volume)....
625w rms = 141dB
312.5w rms = 138dB, (test tone at approx half volume to the ear)
156.25w rms = 135dB, (music at approx half volume to the ear)

Interesting isn't it???? 2.5kw rms and at half volume, (to the ear), it's actually using only 156w rms......

Obviously the above figures are not voltage dependant because they are actually derived from my car, but you should consider the power supply when comparing between current amplification and a possible future upgrade to achieve higher scores/volume.....

So, in order for me to 'Chase' 150dB I would require a staggering extra 2.5kw of amplifier output power, (plus power upgrades to maintain present voltage levels)......

So, to give some insight into just how loud 160dB is, I would need a system doing in excess of 50kw rms......

As I pointed out before simply switching from a sealed enclosure to a ported enclosure will give a 3dB increase....also adding drivers will yield similar increases as will switching from a 'boot only' to say a 'walled' install.....Hence the importance of enclosure design when 'chasing' big numbers.....

So, just to recap, with 3 12" JBL GTi subs and 2.5kw rms on tap I can hit 147dB.
With no enclosure mods, I would need 5kw rms plus power supply upgrades to achieve a possible true 150dB.....

Maybe now you can better appreciate why I tend to take most out put claims with a pinch of salt......

To achieve 140dB is pretty easy...;)

To achieve mid 140s dB is good going...:rolleyes:

To achieve 150dB takes planning, experimenting and bucket loads of power......:eek::cool:
 
#12 · (Edited)
Crossover Basics

Switch Settings & Results....

LPF = Low Pass Filter --- Permits lower frequencies to be played
Flat = OFF --- Permits all frequencies to be played
HPF = High Pass Filter --- Permits higher frequencies to be played

Crossover 'Roll Off' Slope --- Controls how sharp output drops above or below crossover point, most common 'Roll Off' slopes are 12dB or 24dB....Higher value equals a steeper or more abrupt drop in volume as the frequency gets higher/lower....

A couple of quick pics to help;

Red Line = output level





Sub Sonic Filter....

These are effectively high pass filters which operate below the low pass filter, bet that confused you lol....

These tend to be used to prevent a sub playing below an enclosures tuned frequency....The power saved by not playing these lower frequencies can be diverted to a Bass Boost circuit that operates at a pre-set frequency, (usually between 40Hz & 50Hz)....These circuits tend not to be used because they can promote premature 'clipping'....

A sub playing at an enclosures tuned frequency will have less excursion than anywhere above or below it....As frequencies get higher, less excursion is required....As frequencies get lower, greater excursion is required....A sub playing too low will have a tendency to 'unload' & 'over-excurt' causing possible damage....

 
#13 · (Edited)
A few handy pics....

1, Hard wiring Head Unit to battery but keeping ign dependance....


2, Powercap wiring showing remote turn on, (not on all caps)....


3, Powercap wiring with multiple amps, (no remote turn on)....


4, Head Unit Powercap wiring....(Diode should be same value as Head Unit on-board fusing)


5, Standard amp power supply wiring....


6, Relocating battery to boot....(Fuse covering alt charge lead should be greater than alt output but less than cable rating)....


7, Basic Amplifier & Sub wiring....


8, Basic Two Way component wiring....
 
#14 ·
Power cap, should I, or shouldn't I.....????

Firstly, I don't work for Halfords, I don't work for Motorworld or any of the other, "You need a power cap", brigade....

A few basics....

A cars power supply is DC, (Direct Current), so cable resistance plays a large part in supply voltage....

Supply voltage directly affects current being delivered....

A cars stock electrical loom is designed with safety & cost in mind....

On 90% of cars a simple test can be performed to evaluate your stock loom, simply turn on your interior light, now operate your hazard lights, does the interior light dim in time to the hazards???

Operate the windows, again does the interior light momentarily dim???

If you were to rewire your entire car with only electrical performance in mind, then the costs would spiral as would the overall weight of the loom itself....

General claims....

1, Makes system louder.....

Utter unfounded crap....

2, Improves sound quality.....

Debatable, caps are usually used on the bass side of systems, if the bass side is particularly heavy then the cap will become discharged quite quickly, (you need to remember a cap will supply as well as draw from both directions depending on point of lowest resistance), so in some cases a cap can actually harm overall quality....

3, Very fast discharge/recharge cycle.....

True, caps do indeed discharge/recharge very quickly, but you need to remember this cycle is dependant on draw, (if the relevant charge circuit is lacking in any way, then cap performance will suffer)....

4, Will sort 'dimming lights' syndrome.....

If your charge circuit is capable of supporting a power cap, then chances are fitting one won't alter the 'dimming effect' one bit....The only way to rectify the issue in this case would be rewiring the light circuit with performance in mind....

Avoiding Dimming Lights.....

The most common cause of 'dimming' lights is incorrect wiring practices....

YOU CAN'T TAKE OUT WHAT YOU CAN'T PUT BACK IN

A circuit is just that, an outward path & a return path, current will only flow as fast as it can at its weakest/narrowest point....

Lets revert to a basic pic, makes it easier to explain & hopefully easier to follow;


As current is drawn, voltage will dip, (blue level line), if return path is restricted then voltage will remain low, if return path is similar or larger then current will flow easier, (quicker), so maintaining higher voltage level....

By 'NOT ADDING' a new battery to chassis earth to MATCH the new power supply, your simply creating a dam that will restrict voltage throughout the whole car....

A power cap can supply the initial high transients that are required on big bass hits, but if the charge circuit is restricted elsewhere then its usefulness over anything more than a few seconds is very doubtful....

In short, a power caps usefulness is limited to your actual charge circuit, if the charge circuit is adequate, then you simply don't need one....If your charge circuit isn't adequate, then fitting one is pretty much pointless....

Nothing stopping you from using one on the supply to your head unit though:nod:
 
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