splitting a 50W output across 3 speakers?

[MR2_ICE]

i really need help,

this guy that was recommended to come to me by someone i had installed a basic audio system for, has asked me to design and build an audio system for him.

he has a 2 channel amplifier (4ohms) 600W RMS
he wants a 300WRMS subwoofer
and wants 4 speakers too

the audio output channels from his head unit are taken up by the four speakers already in the car but he has a Line-Out on his head unit which can be connected to an amplifier

i was thinking that i could connect a 300W subwoofer to one of the outputs, leaving the built in crossover to full, and using an external crossover to filter the lower ranges to the subwoofer

i thought of seperating the current output from the amp (or watts ouput, whatever its called ... what IS it called? is watts current? or is it called something else?) of the other unused 300W channel, so that i have...

2x 100W and
2x 50W...

...so that i am able to connect 4 speakers to these newly created outputs

is this possible?

if so, is there a certain formula or something i need use? do i need expensive electronics parts? or is it just capacitors and resistors that i need to use?

any kind of help would be greatly appreciated, espcially diagrams although it would be nicer to have little explanations and reasoning behind any suggestions... u know how the saying goes...

give a man a loaf of bread and he will eat for a whole day, explain how its made, and he will eat until his last day

i know i could just tell the guy that i cant do it, but then, i dont know that yet, cos i havent tried it, and besides .... its nice to know, purely because i dont presently know and learning something new is pretty cool

thanks guys (means or gals too!! )
.... and u guys who set this site up, theres a lot of people here, that means a lot of potential help, its greatly appreciated

thanks

Ps. if i can do this, i will probably get quite a few people coming to me for MR2 audio installations as he is part of a couple of MR2 owners clubs like IMOC and knows a few people... ive even set up a site hoping itll kick off! hehe .... talk about counting ur chickens b4 they hatch huh lol ... oh well, i havent put anything on the site yet, as i need to satisfy this man first

 

[Immo_G]

On some of the really cheapo Audioline amps, they have a wiring schematic where you have your left and right speakers connected normally, and then a sub bridged across it as well.

The idea being that the rising impedance of the left + right means the amp doesn't really have to power them in the sub frequencies, and that the subs higher impedance at higher freq means it isn't drawing power.

Whether it actually sounds any good, i don't know, but i doubt it.

 

[sreten]

Basically put your spare channel can easily drive an extra 4
speakers wired in series / parallel but the problem is it would
be mono, and impossible to control from the head unit.

First off the existing installed speakers should be upgraded
to quality units (where would you add 4 more units in a MR2?),
most manufactures make drop in replacements.

If the head can drive them properly fine, if it can't add a 4
channel power amplifier and use the head as a preamp only.

Subwoofer design is much more complicated than specifying
how much power you want. For the MR2 a sealed, small low
efficiency (hence decent bass) sub with lots of power is
indicated.

Whether you need 300W I can't say, perhaps you would
with more power to the other 4.

You should strive to make all the adjustability available in
the head unit usable, so the system is easy to use.

sreten.

 

[MR2_ICE]

hi guys

thanks for your replies

the amplifier is external, plugged into power and wired to the output of the head unit, im not sure what is meant by changing stuff on the head unit, but theres nothing to change on the head uni, the head unit is 50W per channel and is wored to four speakers already of around 50W.

what i want to do, is use one of the 300W (4ohm) output channels and connect it to something that i can make, like a unit with 4 channels... if u know what i mean, i want to convert that one 300W channel so that it distributes two 100W channels and 2 50W channels

what i wanted to know is if this is possible, my theory is, that all it is, is some kind of current, and u can always reduce it... but im not sure how it all works, i dont think i want to bridge anything (the sub is 300W RMS and corresponds exactly to the 1x 300W output channel on the external amplifier) or wire anything in serial unless there are proper electronic components supplying only the current the speaker needs to that speaker.

so basically, what im sayin is, without bridging and changing speakers which isnt what i want to do, i need to be able to seperate the currents to each speaker from one 300W output
using some kind of device that doesnt amplify current or reduce it
ive enclosed a diagram for u guys so its easier to understand what im talking about

thanks again

 

[sreten]

You are out of your depth and sinking fast.

If the guy has already bought the amplifier then he's made
the first cardinal mistake, you don't buy something and then
try and use it, you work out what you need and buy it.

If you want to be a MR2 upgrade guru I think my previous
post covers it.

sreten.

 

[MR2_ICE]

i know what ur sayin, ur saying that i shouldnt even be thinkin about it like that, i should just ask him to pay for another amplifier with 4 channels powerful enough to run 4 speakers off, (which are going to be house in fibre glass custom moulds 2 in the door and 2 in the rear by the window) run that off the output on the head unit.

but what i wanted to know, was if this is possible, at the end of the day as far as i know, its just some electricity passing through those channels in to the speakers, im thinkin its possible somehow, all i want to know is, if it is, or if it isnt, regardless of how expensive or long winded the approach may be, my only need is to learn and understand.

thanks for ur help

 

[MR2_ICE]

please guys, i need help, not to be told im not, or my plan is not wise, its a thought and all i want to know is if im right in assuming it is possible

all i want to know is, is this actually possible?
does my thought on being able to split the current into seperate controlled currents to four channels from one 300W output have any substance?
and if it IS possible, then how do i go about making the device

im not out of my depth, if this is possible im willing to take this to the end. even if no one will explain how its done but leaves a diagram, ill strive to find out myself, purely because i wasnt able to before.

please dont reply if you think i shouldnt or are worried about space costs etc .. no offence intended but its not the answer im looking for

i hope u guys dont think this a nasty post, it really wasnt, its just i have a question and i need help to find the answer to my question, not an alternative

thanks again for all ur posts on this subject, the fact u tried to help is also greatly appreciated

 

[AudioFreak]

If you want to keep the ability to use the controls in the head unit such as pan / balance etc etc etc. you'll need individual amplifier channels for each speaker position you want to control individually. End of story.

 

[MR2_ICE]

hi

ok, all that is going to be controlled is the volume, you dont need to worry about pan and balance, fade and the rest of it

i dont get it, im still not being answered, i dont understand why people are more willing to tell me im thick or i cant do it cos i should be thinkin about something else or that IF i want to control fade pan etc from the head unit THEN i cant

i dont wnat answers to any of that, please dont assume i am not aware of this aspect, i am aware that only certain things can be controlled by doing what i want to do, the head unit has two outputs, one front (wired to an amp already) and one rear (which is connected to the amp in question) in addition to the standard 4 speaker output of the head unit at 50W per channel (which too are connected to repective speakers)

please
please
please
can we stick to the question?

is my theory possible?
if u dont know, please dont answer
if u have alternatives or are here to put me down or demotivate me by saying im wrong in wanting to do it then also please dont answer

only answer this post if u know if my theory is possible, or indeed if its been done and u know how its done

thanks again

 

[sreten]

I don't know what your problem is, your question has already
been answered, given that you've not really explained very
well what it is that you want to do.

4 identical drivers wired in series parallel will each get 1/4
of the channels output i.e 75W each.

If you want to vary the power you need to exploit different
inpedance drivers or add some power resistors - always
being mindful of the the total load on the amplifier channel.

Two 4ohm drivers is series wired in parallel with two 8 ohm
drivers in series, the 4 ohm side will receive twice the power
of the 8 ohm side, but it won't split 200W/100W, you'll get
less power, 170W / 85W ?.
(depending on the amplifiers variation of output with loading)

(which are going to be house in fibre glass custom moulds 2 in the doors and 2 in the rear by the window)

People have assumed these are the 4 drivers you are talking
about driving with your extra channel, and have justifyably
pointed out that this is not a good idea at all.

If your intentions are different, then its very unclear what they are.

sreten.

 

[MR2_ICE]

im sorry if i came across as if i had a problem, its just i felt i was being told alternatives rather than given answers

your last post was helpful, i do appreciate ur continuing help very much and id like to apologise if the way i write has caused offence

the speakers are all 4ohms ... 2 of the speakers (6x9) have an RMS of 80W which is ok i think if theres 75W coming out of the amplifier to each speaker,
which components would i use to reduce the power from 75W to the other 2 speakers that can only handle 40W rms ?

is there a certain formula i can use that will give me the value of the resistor i need to install the same way u can work out speed=distance/time? thatd be really great

apologies again
and thankyou for ur help

 

[MR2_ICE]

just some extra detail u might find useful,

the amplifier can handle 4ohms only, it can handle 2ohms but only if the amp is bridged

 

[sreten]

It really isn't just a simple question of matching amplifier
power to the drivers that are fitted, its far more involved.

You have misunderstood the amplifier specifications,
most can handle 2 ohms except when bridged when
most require > 4ohm load.

Theorectically you would add a 3.3R 10w to 15W power
resistor in series to the 2 4ohm 40w drivers wired in series,
this will bring them down to 37W each.
And wire the other two in series in parallel.
Giving a 4.7 ohm load.

But it still doesn't sound like a good idea to me.

sreten.

 

[MR2_ICE]

hi sreten,

thanks for ur reply

so the resistors are like fuses? .... would it be safe to assume that if any more current gets to it, the resistor will blow and break the circuit and in turn protecting the speaker its connected to? if not, how would i go about doing something like that?

i did misunderstand the instructions, its 4ohms bridged and up to 2ohms unbridged.
as the speakers are 4ohms im thinking of taking ur advice and asking the mr2 man to buy a fairly cheap four channel amplifier... there is a 4 channel 300W amp that gives 75W at 4ohms per channel.

wire in the 2 6x9's to two of the channels and then the two mid range speakers to the other two inputs using the theoretical method u proposed in ur previous post using resistors...
would this be a better idea?

could i wire a 3.3R 15W power resistor to each of the other 2 outputs individually to control the power going to the 40W speakers from each of the other 2 channels

and how do i work out what specification power resistor to use, is it possible to work it out in ratios? or is it more complex than that?
i was thinkin if i took this example

3.3R 15W resistor = reduces 75W output power to 37.5W

would...
3.3R 30W resistor = reduces 75W output power to 18.75W?

is it safe to assume that a resistor at 15W will resist 15W of power? if this is the case could i wire 35W 3.3R resistor and achieve a 40W power supply to the 2 40W speakers? or is it worked out some other way?

thanks again for your help

 

[sreten]

You are totally out of your depth, utterly........

Tell the guy that you have been reccommended to that
as far as installing stuff you can manage it comfortably.

But by being careful and asking advice it appears that design
is a lot more complicated than the basic stuff you've done
before and you've been told that to do a good job he should
take professional advice as to how to upgrade his system,
but you'd be still be happy to install all the stuff for him,
with a layout of the required changes.

If he has already bought some stuff tell him its because
he already has the stuff it makes the design far more
difficult, and the best way forward needs advice from
someone with a lot more experience of upgraded systems.

(If he doesn't like the result, its not your fault,
it will be if you carry on the way you are going)

Its the only way for this particular case.

sreten.