planning to build car sub amp, help needed

[clipto333]

Originally Posted by low_bass_makker

the 300 VA 24-0-24 or 25-0-25 or 24-0-25 step down would cost around 1200/- .........for 1500/- it is a bit on the higher side....is there any brand related to the transformer or just it is a local brand....I used to get GURU....they were quite good.....

i think guru is available here. the transformer is local made.
ill try and find out if guru's avaiable.

thanks
clip

ot - hey lbm, nice amps.

[navin]

1200-1500 is a good price. Miracle would be more I guess.

[clipto333]

Originally Posted by navin

1200-1500 is a good price. Miracle would be more I guess.

hi,

ill buy it from here only. but my project is stuck as i dont know the size of resistors, caps etc. size as in physical size. so dont know what to use from the library of eagle. wish i had a board design of pa100 in eagle.

cheers

clip

[clipto333]

hi,

i was thinking if i can use 3 drivers on 1 channel? eg. if i use 8 ohm drivers( woofer,mid,tweeter) is it possible to get 8 ohm load on the amp on 1 ch? ill use a crossover but dont know how il get the impedance to 8 ohms.

1 thing more. i have hertz energy 165 comps. the drivers are 4 ohms. they have seperate XOs. what will be the final impedance if they are wired in parellel i.e. 1 tweeter and 1 woofer on 1 channel of the amp?? im confused. do they present a 2 ohm load on the amp?

cheers

clip

[low_bass_makker]

no the final load will be 4 ohms if you connect them through the XOs......as there is a capacitor in the way....which will reduce the impedence of the tweeter....

[Bass&Trouble]

Originally Posted by clipto333

1 thing more. i have hertz energy 165 comps. the drivers are 4 ohms. they have seperate XOs. what will be the final impedance if they are wired in parellel i.e. 1 tweeter and 1 woofer on 1 channel of the amp?? im confused. do they present a 2 ohm load on the amp?
cheers
clip

Any component set has one woofer and one tweeter on one channel of the amp. That is normal. Just dont bypass the crossover while wiring like this.

[clipto333]

Originally Posted by Bass&Trouble

Any component set has one woofer and one tweeter on one channel of the amp. That is normal. Just dont bypass the crossover while wiring like this.

hi,

i know how to wire the comps. just want to know how the capacitors lower the impedence. lower as in 4 to 8?? or 4 to 2??

lbm paaji please clarify.

cheers

clip

[low_bass_makker]

if we pass DC current from a capacitor it wil not allow but when we pass AC current it will allow to pass.....likewise in a inductor it will allow to pass DC current and will not allow AC current to flow....in the above statment if I mean allow to flow does not mean it will not flow but a liitle will flow...let me explain a bit further....

In terms of crossover there are capacitor, inductor and resistance is used...

the capacitor is used to make high pass filter.....the inductor is used to make low pass filter and the resistance is used to adjust the gain......


here is a simple circuit of a 6 db slope crossover in which the speaker is given a HPF with the help of the capacitor and the woofer is given a LPF with the help of a inductor......

you can see that the as the value of the capacitor or inductor the change of frequency is there......

there is something more left...will be posting soon...as I have to go for some work....

[navin]

Originally Posted by clipto333

i know how to wire the comps. just want to know how the capacitors lower the impedence. lower as in 4 to 8?? or 4 to 2??

clipto you are confusing impedance with resistance. impedance is depedant on the freq at which it is measured. if you are connecting a 8 ohm woofer, midrange and a tweeter via a crossover each driver will reproduce a seperate freq band and the nominal impedance of the speaker system will be 8 ohms. In reality there will be peaks and dips in the freq response.

A capacitor does NOT decrease or increase the resistance of a tweeter. It does however LIMIT the freq range of the tweeter. In a perverse way one can say that a capacitor INCREASES the impedance of a tweeter because a cap is an OPEN circuit to DC and as the freq of the signal increases the capacitor shows less resistance.

[clipto333]

Originally Posted by navin

clipto you are confusing impedance with resistance. impedance is depedant on the freq at which it is measured. if you are connecting a 8 ohm woofer, midrange and a tweeter via a crossover each driver will reproduce a seperate freq band and the nominal impedance of the speaker system will be 8 ohms. In reality there will be peaks and dips in the freq response.

hi navin,

thanks for clarifying. what i understand from the above is that the nominal impedance of the speaker system( woofer,,mid,tweet ) will be 8 ohms nominal.
if i dont use a XO, will the nominal impedance still be 8 ohms??

Nominal impedance is measured in free air at a given low frequency right??

I just built a pcb myself. it turned out really good. ill post pics in a while. my cam is on charging. this was my first attempt and its almost perfect. i used the toner transfer method.

cheers

clip

[low_bass_makker]

if you dont have the XO then the nominal impedance will be 4 ohms when the woofer is 8 ohms and tweeter is 8 ohms....

yes the nominal impendance is measured in free air....when the impedance of speaker has reached the resonant freq it will have maximum impedance....


wating to see the pics of your amp.....

[clipto333]

Originally Posted by low_bass_makker

if you dont have the XO then the nominal impedance will be 4 ohms when the woofer is 8 ohms and tweeter is 8 ohms....

yes the nominal impendance is measured in free air....when the impedance of speaker has reached the resonant freq it will have maximum impedance....


wating to see the pics of your amp.....

hi lbm,

thanks for clarifying. ive not build the amp yet. just built the pcb. ill post pics of that tomorrow.

cheers

clip

[low_bass_makker]

here is a graph of a sub the black line is the impedence of the driver....and its FS (resonant freq) is approx 75 hz.....at which the sub is having least impedance otherwise it is close to 4 ohms as the sub is a SVC......hope this make the thing a bit more clear....

[navin]

Originally Posted by clipto333

f i dont use a XO, will the nominal impedance still be 8 ohms??

if you dont use an XO and connect all 3 drivers in parallel you will get a nominal impedance of 2.33 ohms (8/3). However once you connect your amp to this speaker and play it for a while the nominal impedance will rise to 4 ohms becuase you will have burnt your tweeter out and you will have only 2 drivers (woofer and midrange) left. :-(

Why on earth are you trying to build/wire a 3 way speaker and bypass the crossover?

[clipto333]

Originally Posted by navin

Why on earth are you trying to build/wire a 3 way speaker and bypass the crossover?

hi navin,

im not going to power the speakers without the XO. it was just for knowledge. ill have to do more research on the XO to understand how it works. :-)

cheers

clip.