a few audio questions answered

[wallopsri]

this is a copy of a thread i did on another forum, hope you find it useful.

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 setup 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 earths, 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 headunit 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 headunit to play, the more likely it is to distort,(this is due to voltage drop in the headunit, 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 headunit 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 recieves, if it recieves a good strong signal, it will reproduce a clean clear sound, if it recieves 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 headunits just don't have that kind of power.

when selecting a new headunit you should take into consideration exactly what you require from it. in most cases if you are fitting a headunit 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 headunit is still too powerful for the new speakers, when in truth the opposite is correct, the headunit 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 recieves, 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 faliure.

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 resonnate 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.

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 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 tone on paper it would be 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. 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 impedence, the same applies to all amps and speakers. this is referred to as,"headroom".

[wallopsri]

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.

[wallopsri]

a few basic facts regarding OHM'S LAW

the ohm is a measure of impedence, 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 impedence,(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 impedence, 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






any question's----lol.

just in case anyone out there should require test tones and bass tracks to aid in setting up your systems, follow the link;

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

[wallopsri]

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.

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.

hope you find this useful---wallop

[Rob]

Very comprehensive.

Stickied.

[wallopsri]

WOW!!! that was quick.

[Rob]

- I can speed read!

[wallopsri]

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

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.

[Turbo 4 astra]

Damn what an amazing post! Will try and follow it to a letter!! Makes a lot of things clearer (amazingly!) as well.

Thanks

[Turbo 4 astra]

Oh except the power cable chart, f*** that! lol

[Adam]

what a great thread...i typed into 'search' powercap..as wante info on them and now im saving 50 bucks and not bothering

so should i buy a lardy haauge battery?

[wallopsri]

Originally Posted by Adam

what a great thread...i typed into 'search' powercap..as wante info on them and now im saving 50 bucks and not bothering

so should i buy a lardy haauge battery?

if you've already added a battery to chassis earth to match your audio power feed & uprated your engine/gearbox to chassis earth, then the next step is a larger capacity battery....(assuming the alt is indeed a 100amp one or larger)

you can upgrade to the diesel variant battery for your car, or as shown, opt for a deep cycle battery in place of the stock item.

i would advise cavalier owners to check the alternator output first though, these cars come with 3 basic sizes, 70amp, 90amp, 100amp & in rare cases 120amp,(the latter is normally fitted by audio enthusiasts from either the omega,(v belt) or frontera,(twin belt), and is a direct fit).

if you already have a 100amp alt and have upgraded your wiring, then its time for either a bigger starter battery or a split charged battery in the boot...(esp if running stereo with engine off).

HTH

[GSI_Marko_GSI]

Originally Posted by wallopsri

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.

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.

hope you find this useful---wallop

This may sound stupid but would i do the same test as the front's if i was using some chav by 9s as well as sub's and components. Tar matey

[wallopsri]

Originally Posted by GSI_Marko_GSI

This may sound stupid but would i do the same test as the front's if i was using some chav by 9s as well as sub's and components. Tar matey

GOOD QUESTION




yes mate, if using 6x9's in conjunction with a sub you should high pass them,(start at similar point to fronts, then adjust to taste)...

if using 6x9's instead of a sub, then you can either low pass them,(this will preserve your soundstage and imaging), or run them full range,(crossovers/filters switched off), for added volume,(but this will drag your soundstage toward the rear of the car and muddy the imaging)....if low passing them i would start at 125hz and adjust to taste....

for best results i would advise 6x9's are run in sealed enclosures,(if shelf mounted then simply box them in using a single shallow box that houses both baskets with all joins sealed with a bead of silicone caulk)....allow 24hrs for sealing agent to cure, chemicals given off whilst curing can damage some speaker components...

HTH

[smokey!]

Where can i get testing cd or downloads? for setting up install?

[wallopsri]

Originally Posted by smokey!

Where can i get testing cd or downloads? for setting up install?

the bottom of POST 3 on this thread mate

[Kabouter]

wallopsri, you mentioned I think earthing rca leads to eliminate ground noise or the buzzing on the speakers from power steering or alternator. Can you explain on how you would go about earthing the rca's?

[wallopsri]

Originally Posted by Kabouter

wallopsri, you mentioned I think earthing rca leads to eliminate ground noise or the buzzing on the speakers from power steering or alternator. Can you explain on how you would go about earthing the rca's?

i think you may be a little confused mate, earthing the RCA's is only done to elliminate noise caused by a headunit actually earthing through the RCA and so through the amp,(pioneer units are renowned for this fault)...

there are a number of faults which can promote background noise, the most common being a poorly selected or prepared amplifier earth site...

however, as a general guide, you should firstly try to isolate the item which is causing the problem;

switch off system----disconnect RCA's from the suspect channels----switch system on;

if noise is still present---then its either amp wiring,(suspect earth site/connection), or possibly a short in the speaker wiring,(check no speaker terminals are touching internal door panels or window mechanism parts), it may also be a faulty speaker itself...

if noise is no longer present---this indicates the amp and speakers are fine---so now you should---switch system off---reconnect RCA's to the amp---now remove headunit from the dash but leave wiring connected---now disconnect RCA's from the headunit---switch system on;

if noise is present---this indicates its simply a faulty RCA lead.

if noise is not present---this would indicate you are using a PIONEER headunit 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 headunit,(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 headunits 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 headunits chassis,(i usually use the headunits rear support screw location), this fix should solve most cases, but on occasion it can be necasary to also earth the headunits mounting cage to the cars chassis....

HTH

[Kabouter]

brilliant will try it and see what works. Have been having this problem since the original install and thought it was the epx2 at first but the latest suspect has been the remote wire, because if I switch the head unit off I get a boom on the speakers as the amps switch off?
thanks for the reply.

[wallopsri]

Originally Posted by Kabouter

brilliant will try it and see what works. Have been having this problem since the original install and thought it was the epx2 at first but the latest suspect has been the remote wire, because if I switch the head unit off I get a boom on the speakers as the amps switch off?
thanks for the reply.

amplifier pop when turning off or on is an indication that the amp earth is suspect,(either a poor connection and/or earth site)....

[wallopsri]

Originally Posted by wallopsri

if you've already added a battery to chassis earth to match your audio power feed & uprated your engine/gearbox to chassis earth, then the next step is a larger capacity battery....(assuming the alt is indeed a 100amp one or larger)

you can upgrade to the diesel variant battery for your car, or as shown, opt for a deep cycle battery in place of the stock item.

i would advise cavalier owners to check the alternator output first though, these cars come with 3 basic sizes, 70amp, 90amp, 100amp & in rare cases 120amp,(the latter is normally fitted by audio enthusiasts from either the omega,(v belt) or frontera,(twin belt), and is a direct fit).

if you already have a 100amp alt and have upgraded your wiring, then its time for either a bigger starter battery or a split charged battery in the boot...(esp if running stereo with engine off).

HTH

thought i would add this to save searching for it at a later date....


ok, over the last few weeks 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 ..

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

had a young lad last week 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 everytime 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 theres 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)....

EDIT; forgot to mention, the split charge relay should be mounted inside the car to protect it from the elements...

heres a quick sketch which should help you avoid this issue...

[michael61182]

I'm a bit confused. I have 1 cerwin vega vmax 12, dual coil. 2ohms each coil. My amp is kenwood excelon kac-x522, bridged output is 4-ohms. How should i wire my sub for best sound. Thanks.

[wallopsri]

Originally Posted by michael61182

I'm a bit confused. I have 1 cerwin vega vmax 12, dual coil. 2ohms each coil. My amp is kenwood excelon kac-x522, bridged output is 4-ohms. How should i wire my sub for best sound. Thanks.

Hi mate,

Welcome to MIG, here you go;

[F4ntasia]

I understand everything so far, except for the wiring sizes. I have 2 Alpine 900watt(Peak) 300watt(RMS) subs. And a Pyle Driver 1300watt(Peak) bridged amp with 500watt(RMS) x 2 channels @ 4 Ohms. (My subs are both 4 Ohms) However I just dont understand what size cable I require, or how to choose it. Can anyone help me out please?

[wallopsri]

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...

To achieve 150dB takes planning, experimenting and bucket loads of power......

If you have a 150dB boot only install then get along to Car Audio & Security in Hayes on the last Sunday of each month, they run a Monthly competition & the loudest car always gets a nice Prize, (Vibe 'Black death' sub this time round).....