Hey Boostcruisers
With much confusion surrounding this aspect of car modification, I was hoping that with the assistance of people with knowledge on this site, a guide to car audio could be compiled for reference to all in the future.
I hope that this can contain aspects of car audio from calculating Power in WRMS, to the meanings of values such as Xmax, efficiency etc., specifications which are often ignored when shopping for car audio.
I will begin listing a few, but it would be appreciated if people could come forward and share their questions and knowledge so that eventually a guide for reference may be established I will aspire to regularly update this original post to prevent having to scan through the following pages Feel free to correct any of the information
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General Information
*Terminology:
Impedance - The resistance of a load
Ohms - Main unit for Impedance
Watts - Main unit for Power
Amps - Main unit for Current
WRMS - Watts Root Mean Square (see below)
Hertz - Unit of measure of frequency
Frequency response (Hz) - It identifies the speaker bandwidth, the limits within which it can be used with a linear response
Decibel - Unit of measure of sound pressure
HU - Head Unit
AMP - Amplifier
THD (Total Harmonic Distortion) - Measured additional noise or interference induced into the system by the power supplies
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Amplifiers
Calculating WRMS:
From Max Power - Max Power / (Square Root 2)
Bridged Mode for a single 4 ohm speaker - 2*(AMP Power in WRMS @ 2 ohm):
#Eg. 2 Channel Amp; Power: 50WRMS/channel with 4 ohm load, 70WRMS/channel with 2 ohm load .:. Bridged WRMS = 2* 70 wrms = 140 wrms. Therefore the 4 ohm speaker is receiving 140 WRMS of power
Parallel Mode with 2 equal speakers of x ohm - Power = [Power @ (x/2) ohms]/2
#Eg. Mono block Amp; Power: 200 WRMS with 4 ohm load, 350 WRMS with 2 ohm load. .:. Parallel WRMS = 350 WRMS/2 = 175 RMS. Therefore, each 4 ohm sub would be receiving 175 WRMS of power
Series Mode with n speakers at x ohm - ?
*Terminology:
Stereo -A stereo system has two independent signals, each driven into its own separate speaker
Mono - A mono system sends the SAME signal to ALL of the speakers
Max. Power - The maximum power an amplifier can produce with no load
WRMS (Nominal Power) - The power that the speaker is actually receiving from the amplifier at a continuous rate
Bridging - Connecting the -ve from one channel and the +ve from a second channel to drive a single speaker with more power due to each channel seeing 2 ohm resistance. This does NOT mean that there is a resistance of 2 ohm in total, just that each channel see half the total resistance.
Parallel - Running two speakers off the one channel, in result halving the impedance
Clipping - When the volume is turned up past what the amplifier can deliver and distorts
Overload Protection - A protection circuit that eliminates component failure from impedance loads that are to low by shutting off the amplifier
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Speakers
*Terminology:
Power Handling - The power that a speaker can receive for short moments (Max) or for continuous programs (Nominal).
Efficiency (dB): Reference efficiency value of a speaker; it is measured in decibels and at a distance of one meter, with 2.83 Volts in the input
Tweeter - Speaker specialised in reproducing high frequencies
Midrange - Speaker specialised in reproducing mid frequencies
Woofer - Speaker specialised in reproducing low and mid frequencies
Xmax (mm) - Mobile voice coil excursion, in one direction
Voice coil - Wire (usually copper) winding around a cylindrical former that is glued with the speaker membrane. Alternate current passing through mobile voice coil generates a magnetic field that interacts with the one occurring into the gap; the vibrations that derive from this are sent to the membrane, generating sound
Speaker Size - The dimensions of the speaker given in terms of inches
Coaxials - A speaker which produces all three frequencies in one unit
Components/Splits - A set of speakers which seperates into 2 or 3 lone speakers, which is combined with a crossover so that each speaker only reproduces its specific frequency
Crossover - Filter used to separate frequencies to their appropriate speakers
*Resistance Calculations:
Speakers in Series = R1 + R2 + ... + Rn
Speakers in Parallel = [R1^-1 + R2^-1 + ... + Rn^-1]^-1
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Speaker Enclosures
*Terminology:
Sealed - Airtight enclosure suited to general applications
Ported - Enclosure with ports which can be tuned to certain frequencies to change SQ and SPL characteristics
Isobaric - Two speakers placed in an array as to act as one speaker in an enclosure design that requires half the air space that a single driver requires
Bandpass - Bandpass boxes are a special type of ported box designed for maximum bass. The woofer is mounted inside a dual-chambered box (one chamber sealed, the other ported), with the sound waves emerging from the ported side. The sound that comes out of the port is extra loud within a narrow frequency range
Dipole Passive Radiator - A sealed box with 2 subs running out of phase

Infinite Baffle - Infinite baffle enclosures are the simplest from a design concept. The principle of IB design is the seperation of the front output of the woofer from the rear output of the woofers. One of the advantages of this design is the low resonant frequency of the IB system. This low RF allowes the system to have a very good low frequency extension. Another advantage of an IB design is the little amount of boot space needed for this application. For this reason IB designs are popular in cars where the boot space is small but there is a need for big bass...

One of the main disadvantages of this application is the REDUCED MECHANICAL POWER HANDLING of the speaker. This is due to the fact that the enclosure is actually the whole boot volume and the air in the boot is not able 2 help the mechanical suspension system of the woofer, for this reason not all woofers are suited for IB applications.

It is a common misconception that IB enclosures are the easiest to construct, this is not true as maximizing performance in this type of enclosure is quite difficult and time consuming. Maximizing the performance in a IB system you must minimize leaks and maximize the sturdiness of the baffle....

Ok, so in short an IB enclosure is putting a sub in the parcel tray and using the boot as one big enclosure and attempting to seperate all the air either side of the tray, same principal is used when placing a sub in the ski-port in some sedans and using the back seats/parcle tray as the dividing wall and the boot as the enclosure.

Also this type of enclosure means u cant feed buckets of power 2 the sub cos its not being helped by the box and will be worked 2 hard if u do apply 2 much power.

You will be surprised how many installs come out of brisbane car sound like this, if u feel air leaking from around the plate ur sub is fixed 2 then this is the "box" that u have got... *Written by 'Ferdie'
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Head Units
*Terminology:
'Loud' Button - To prevent overloading on speakers i.e push into clipping, try and adjust system gain levels to prevent its use
Power Rating ( 45 x 4 etc.) - This is the Max Power of the HU, not the WRMS. However, this usually equates to only approx. 13 WRMS from each channel
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SPL and SQ
*Terminology:
SPL - Sound Pressure Level, measured in dB
SQ - Sound Quality, measured in ?
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Display Units
*Terminology:
LCD - Liquid Crystal Display
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Wiring Guide
*Terminology:
AWG (Gauge) - American Wire Gauge; Used to describe the size of a wire in relation to its current carrying ability. Smaller the AWG, Higher the current carrying ability
Earth/Ground Wire - The wire which is earthed to the chassis via direct contact; Drains excess electrons to create an equal balance in the system
Power (Memory) Wire - The wire running directly from the battery to the source unit i.e HU, AMP; providing the main source of power. Called memory wire in reference to its ability to provide power to the HU so that stored data is not lost when the car is switched off
Accessory Wire - The wire which only supplies power to the source unit when the ignition is turned over to ACC i.e car turned 'ON'
Speaker Wire - The wire which sends power and signal to a speaker
RCA Outputs - Dual wires which are specifically for sending signal to an amplifier, as they do not have a high enough output current to drive a speaker
Internal Wire Resistance - The resistance of the actual metal which the wire is made out of, usually small in relativity
*Guide to choosing what gauge wire:
AWG___Maximum Rated Current
00___ 400 amps
0___ 325 amps
1___ 250 amps
2___ 200 amps
4___ 125 amps
6___ 80 amps
8___ 50 amps
10___ 30 amps
12___ 20 amps
14___ 15 amps
16___ 7.5 amps
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FREQUENTLY ASKED QUESTIONS (FAQ'S)

Q: Will a blow off valvy thingy give me booste?
A: NO!

Anyways, here is a list of questions that seem to appear constantly in this forum:

Q: Is it safe to overpower a sub or speaker? Eg. 700W amp on a 400 W sub...
A: Yes, as a matter of fact, it is a lot more beneficial for the subs performance and safety that you use a overpowered amp and adjust the gain settings to suit your listening levels. Underpowering a sub, then pushing it to its limits (high volumes) can be harmful to both sub and amp due to clipping (see above)

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Contributors:
+ Boostcruising Members
TRD Rolla, Deva, Nedgeworth, Avieec, 70XIN, WoodStok, ferdie

+ Websites/ Companies
www.boostcruising.com, www.audison.com, www.caraudioaustralia.com, www.bcae1.com, www.crutchfieldadvisor.com, FHRX Studios, www.polkaudio.com

TRD Rolla

**UPDATED AT:**

thats some very useful information there trd. well done

Agreed, Thankyou for the usefull information.

www.caraudioaustralia.com

enough said, i went from knowing NOTHING about car audio, to knowing an incredible amount after surfing this site for a week

Amplifiers
*Calculating WRMS:
From Max Power - RMS value is .707 of PEAK value i.e peak value of Sine waveform (but sometimes amps don't give correct specs so this can't always be trusted)

Bridged Mode @ with x ohm speaker - ?? what u mean?
Parallel Mode with n speakers of x ohm - parallel impedance = R1 + R2 + ... divided by n
Series Mode with n speakers at x ohm - series impedance = R1 + R2 + ...

mm pretty limited on box types. just to let people know there's more to just having a sealed or ported box.

sealed
ported (also known as bass reflex)
dual bandpass
dipole passive raditor (a sealed box with 2 subs running out of phase)
theres more but i cant rember them.


then there's the custom box designs. im actually making a 'wicked one' dual 12" dualbandpass folded horn box. (lol)

with calculating RMS isnt it square root of .707 or somfin? I should know this i have it on a test tomorrow. *Heads back to the books

I've found the following site very helpful as well as what others have stated with CAA. You will find that the following site should answer most if not all of the things that have been posted up to keep updated. Also i have put a link to FHRX website that also has some useful information about things to look for when purchasing and explains a few of the terms also.

http://www.bcae1.com/
http://www.fastfoursforumscarclub.com/temp...studios/faq.asp

Cheers everyone

TRD Rolla

Thanks for that Nedge.

Thats awesome. some faq's might be a good idea, it would pretty easy to do. just flick back a few pages on this forum "car audio/electrical/interier" and find the common questions asked.

also when buying speakers dont look at the spec's use you ear's

cause it dont matter what the spec's say you have to listen to them every day

yeah this can be more or less true to the better brands. But go for something like a Boss Amplifier 1000w max, i know from personal experience that it doesnt put out 500rms.

thanks a bunch TRD+evryone else that posted... its helped me wire up a nice as system! ill probs post pics later

woot i just used this on my car good work

heres a FAQ: does it matter what sort of head unit you have for subs like do you have to have a sub output mp3 blah blah blah or can you just run a decent CD-R reciever???

all sub control does is change the level on the sub channels. so if u don't mind having ur subs at the same level in proportion to the speakers a cd reciever is fine. altough sub control is helpful if you switch between music with lots of highish lows and music with very deep lows, so you can still get decent bass with out your splits screamin in ur ears.

Very useful, thanks a lot, has cleared quite a few things for me.

Source: http://www.the12volt.com/caraudio/theile.asp

Theile-Small Parameters

[center]B[/center] [center]Magnetic flux density in gap, in Tesla-meters ™[/center]
[center]BL[/center] [center]The magnetic strength of the motor structure. "Expressed in Tesla meters, this is a measurement of the motor strength of a speaker. Think of this as how good a weightlifter the transducer is. A measured mass is applied to the cone forcing it back while the current required for the motor to force the mass back is measured. The formula is mass in grams divided by the current in amperes. A high BL figure indicates a very strong transducer that moves the cone with authority!"[/center]
[center]C[/center] [center]Propagation velocity of sound at STP, approx. 342 m/s[/center]
[center]Cas[/center] [center]Acoustical equivalent of Cms[/center]
[center]Cmes[/center] [center]The electrical capacitive equivalent of Mms, in farads[/center]
[center]Cms[/center] [center]The driver's mechanical compliance (reciprocal of stiffness), in m/N[/center]
[center]D[/center] [center]Effective diameter of driver, in meters[/center]
[center]F3[/center] [center]-3 dB cutoff frequency, in Hz[/center]
[center]Fb[/center] [center]Enclosure resonance (usually for bass reflex systems), in Hz[/center]
[center]Fc[/center] [center]System resonance (usually for sealed box systems), in Hz[/center]
[center]Fs[/center] [center]Driver free air resonance, in Hz. This is the point at which driver impedance is maximum. "This parameter is the free-air resonant frequency of a speaker. Simply stated, it is the point at which the weight of the moving parts of the speaker becomes balanced with the force of the speaker suspension when in motion. If you've ever seen a piece of string start humming uncontrollably in the wind, you have seen the effect of reaching a resonant frequency. It is important to know this information so that you can prevent your enclosure from 'ringing'. With a loudspeaker, the mass of the moving parts, and the stiffness of the suspension (surround and spider) are the key elements that affect the resonant frequency. As a general rule of thumb, a lower Fs indicates a woofer that would be better for low-frequency reproduction than a woofer with a higher Fs. This is not always the case though, because other parameters affect the ultimate performance as well."[/center]
[center]L[/center] [center]Length of wire immersed in magnetic field, in meters[/center]
[center]Lces[/center] [center]The electrical inductive equivalent of Cms, in henries[/center]
[center]Le[/center] [center]"This is the voice coil inductance measured in millihenries (mH). The industry standard is to measure inductance at 1,000 Hz. As frequencies get higher there will be a rise in impedance above Re. This is because the voice coil is acting as an inductor. Consequently, the impedance of a speaker is not a fixed resistance, but can be represented as a curve that changes as the input frequency changes. Maximum impedance (Zmax) occurs at Fs. "[/center]
[center]Ms[/center] [center]The total moving mass of the loudspeaker cone. [/center]
[center]Mmd[/center] [center]Diaphram mass, in grams[/center]
[center]Mms[/center] [center]The driver's effective mechanical mass (including air load), in kg. "This parameter is the combination of the weight of the cone assembly plus the ‘driver radiation mass load’. The weight of the cone assembly is easy: it’s just the sum of the weight of the cone assembly components. The driver radiation mass load is the confusing part. In simple terminology, it is the weight of the air (the amount calculated in Vd) that the cone will have to push."[/center]
[center]n0[/center] [center]The reference efficiency of the system (eta sub 0) dimensionless, usually expressed as %[/center]
[center]p (rho)[/center] [center]Density of air at STP 1.18 kg/m^3[/center]
[center]Pa[/center] [center]Acoustical power[/center]
[center]Pe[/center] [center]Electrical power[/center]
[center]Q[/center] [center]The relative damping of a loudspeaker[/center]
[center]Q Parameters[/center] [center]"Qms, Qes, and Qts are measurements related to the control of a transducer's suspension when it reaches the resonant frequency (Fs). The suspension must prevent any lateral motion that might allow the voice coil and pole to touch (this would destroy the loudspeaker). The suspension must also act like a shock absorber. Qms is a measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs. Qes is a measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock. Qts is called the 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same.

As a general guideline, Qts of 0.4 or below indicates a transducer well suited to a vented enclosure. Qts between 0.4 and 0.7 indicates suitability for a sealed enclosure. Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications. However, there are exceptions! The Eminence Kilomax 18 has a Qts of 0.56. This suggests a sealed enclosure, but in reality it works extremely well in a ported enclosure. Please consider all the parameters when selecting loudspeakers. If you are in any doubt, contact your Eminence representative for technical assistance." [/center]
[center]Qa[/center] [center]The system's Q at Fb, due to absorption losses; dimensionless[/center]
[center]Qec[/center] [center]The system's Q at resonance (Fc), due to electrical losses; dimensionless [/center]
[center]Qes[/center] [center]The driver's Q at resonance (Fs), due to electrical losses; dimensionless. "A measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock." [/center]
[center]Ql[/center] [center]The system's Q at Fb, due to leakage losses; dimensionless[/center]
[center]Qmc[/center] [center]The system's Q at resonance (Fc), due to mechanical losses; dimensionless[/center]
[center]Qms[/center] [center]The driver's Q at resonance (Fs), due to mechanical losses; dimensionless. "A measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs."[/center]
[center]Qp[/center] [center]The system's Q at Fb, due to port losses (turbulence, viscousity, etc.); dimensionless[/center]
[center]Qtc[/center] [center]The system's Q at resonance (Fc), due to all losses; dimensionless[/center]
[center]Qts[/center] [center]The driver's Q at resonance (Fs), due to all losses; dimensionless. "The 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same."[/center]
[center]R[/center] [center]Ripple, in dB[/center]
[center]Re[/center] [center]"This is the DC resistance of the driver measured with an ohm meter and it is often referred to as the 'DCR'. This measurement will almost always be less than the driver's nominal impedance. Consumers sometimes get concerned the Re is less than the published impedance and fear that amplifiers will be overloaded. Due to the fact that the inductance of a speaker rises with a rise in frequency, it is unlikely that the amplifier will often see the DC resistance as its load."[/center]
[center]Ras[/center] [center]Acoustical equivalent of Rms[/center]
[center]Res[/center] [center]The electrical resistive equivalent of Rms, in ohms[/center]
[center]Rms[/center] [center]"This parameter represents the mechanical resistance of a driver’s suspension losses. It is a measurement of the absorption qualities of the speaker suspension and is stated in N*sec/m."[/center]
[center]Revc[/center] [center]DC voice coil resistance, in ohms[/center]
[center]Rg[/center] [center]Amplifier source resistance (includes leads, crossover, etc.), in ohms[/center]
[center]Rms[/center] [center]The driver's mechanical losses, in kg/s[/center]
[center]Sd[/center] [center]Effective piston radiating area of driver, in square centimeters. "This is the actual surface area of the cone, normally given in square cm." [/center]
[center]SPLo[/center] [center]Sound Pressure Level, usually measured at 1 watt, at 1 meter in front of the loudspeaker[/center]
[center]Vas/Cms[/center] [center]"Equivalent volume of compliance", this is a volume of air whose compliance is the same as a driver's acoustical compliance Cms (q.v.), in cubic meters. "Vas represents the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker. Vas is one of the trickiest parameters to measure because air pressure changes relative to humidity and temperature — a precisely controlled lab environment is essential. Cms is measured in meters per Newton. Cms is the force exerted by the mechanical suspension of the speaker. It is simply a measurement of its stiffness. Considering stiffness (Cms), in conjunction with the Q parameters gives rise to the kind of subjective decisions made by car manufacturers when tuning cars between comfort to carry the president and precision to go racing. Think of the peaks and valleys of audio signals like a road surface then consider that the ideal speaker suspension is like car suspension that can traverse the rockiest terrain with race-car precision and sensitivity at the speed of a fighter plane. It’s quite a challenge because focusing on any one discipline tends to have a detrimental effect on the others. "[/center]
[center]Vd[/center] [center]Maximum linear volume of displacement of the driver (product of Sd times Xmax), in cubic meters. "This parameter is the Peak Diaphragm Displacement Volume — in other words the volume of air the cone will move. It is calculated by multipying Xmax (Voice Coil Overhang of the driver) by Sd (Surface area of the cone). Vd is noted in cc. The highest Vd figure is desirable for a sub-bass transducer."[/center]
[center]Xmax/Xmech[/center] [center]Maximum peak linear excursion of driver, in meters. "Short for Maximum Linear Excursion. Speaker output becomes non-linear when the voice coil begins to leave the magnetic gap. Although suspensions can create non-linearity in output, the point at which the number of turns in the gap (see BL) begins to decrease is when distortion starts to increase. Eminence has historically been very conservative with this measurement and indicated only the voice coil overhang (Xmax: Voice coil height minus top plate thickness, divided by 2). Xmech is expressed by Eminence as the lowest of four potential failure condition measurements times 2: Spider crashing on top plate; Voice coil bottoming on back plate; Voice coil coming out of gap above core; Physical limitation of cone. Take the lowest of these measurements then multiply it by two. This gives a distance that describes the maximum mechanical movement of the cone."[/center]
[center]Zmax[/center] [center]"This parameter represents the speaker’s impedance at resonance."[/center]

Fuses sizes and power handling of cable sizes.

[attachmentid=25278] [attachmentid=25279]

Great work with that, it'll definitely help the audio newbies..
... But I have to add that you can't exactly calculate RMS from Peak these days, because manufacturers lie so much... Maybe they test their amps with a burped higher voltage, for a split second, not measuring %THD... My friend's "2000 watt amp" has 20A fuses and isn't as gutsy as my "800 watt amp" which has 30A fuses. Imo you can't get anything out of peak besides an estimate, and the most reliable ways to get a power figure are fuses (estimate, or even calculate..), your ears (compare to another amp), or best of all, a CRO (I think that's the name of it - tests the power properly).

Btw nice 6th order horn enclosure avieec..

Basic tech article with lots of pics on how to install a cd player here...
http://www.boostcruising.com/forums/index....howtopic=114457

Hey, interesting article.

I am currently doing a restricted electrical licence and car audio seems to speak a different language to, regular electronics, i mean how can you measure work in ohms? when we work with motors and things, we measure work in amps. Also, what would people recomend for a single cab ute, pioneer have those new flat subs, has anyone used them? I currently have 2 pioneer 6x9 speakers and 760 watts amp, and a pioneer head deck. The problem is, the door inserts are flimsy and you cant turn it up too loud or else you get things vibrating and it sounds crap.

I am over due to upgrade, i was looking through the latest pioneer catalogue, has any actually got the new satellite pioneer system?

Ahh well thats all from me
Seamoose

WOW INFORMATION OVERLOAD!!!! haha great work mate

~Heated Up~

Quick question, I'm buying a second hand amp wiring kit but it doesn't come with a fuse/s, although a few of my friends say that I don't need a fuse could anyone else elaborate more on this? Do I need the fuse/s? Any consequences of not having them?

Well if you would like to see your car go up in flames by not using one go right ahead!!! You need the safety there to protect your investment.

for everyone trying to work out watts rms what is honestly the point. If the manufacturer doesn't have an rms rating don't buy the bloody thing because its obviously a dodgy pos.

This has totally changed my life forever. Me and a couple of mates were looking into buying sound systems for our cars and this has been so helpful.

Glad its still being of assistance all these years later

Thankyou very much for this info, best of luck to other new installers

[qoute]Bandpass - Bandpass boxes are a special type of ported box designed for maximum bass. The woofer is mounted inside a dual-chambered box (one chamber sealed, the other ported), with the sound waves emerging from the ported side. The sound that comes out of the port is extra loud within a narrow frequency range
Dipole Passive Radiator - A sealed box with 2 subs running out of phase[/qoute]



not 100% true only half the story.



a band pass enclosure is more likely to not have a sealed section, but stilla dual chamber enclosure each ported and tuned for the individual speaker, normally with the rear enclosure becoming the front (if this make smore sence : the front of the box [were the ports vent] the chamber housing the rear of the speaker having the shorter port and smaller chamber to create output of certain frequencys at the bottom end of the scale from 30Hertz down as low as the chamber is designed for (msot common around 15) this is to create mroe of a vibrating sensation or rumble to make lsitning a more exiting experience, then the larger chamber housing the front of the speaker and with longer ports which displace less air pressure crating smoother sound for slightly higher frequencys 25Hertz to around 40Hertz. band pass enclusures are onyl suited to some kinds of speakers, and it is hard to go into the correct type but as a general but inacurate way to describe them are speakers with a small coen area and a large suround as this allows the speaker to mvoe more frealy and to move further to displace more and and create more preasure within the chambers.



hope that might help some people a little

^^^^^

remember this is a CAR forum. not a home hifi forum.

go post your reply in a Home Stereo forum.

I know many people who use band pass enclosures in cars . . . if a band pass enclosure wasn’t relevant why was it mentioned in the original post?

in car audio a bandpass box, be it Single Reflex, Isobaric single reflex, three chamber single reflex, isobaric 3 chamber single reflex... i could go on...

All have a sealed section and a ported section.

the only Bandpass boxes that DONT have a sealed section are Eigth Order boxes, Dual reflex bandpass and Quasi-Sixth Order (series tuned and isobaric)

Truth, take some house stereos for example, I know someone with a 30wrms x 2 sony boombox that claims 3,600watts peak.

^This.

A fuse is designed to cut power should your stereo short out, a shorting out power wire to the earth (chassis) of the car is enough to melt anything it's in contact with and cause a fire. Amplifiers have their own fuses to protect your circuitry from damage in such a scenario, but without a system fuse, the wire between the battery and the amplifier will not be protected in a short and likely not only leave a nasty burn in your carpet, but also feed power into the chassis of your car, potentially damaging anything electrical in the car since your cars fuse box only protects the positive side of all the electrics in your car, feed power into the negative side while it's running and nothing is protected.