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Old 1st March 2004, 01:14 PM   #11
MR2_ICE is offline MR2_ICE  United Kingdom
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Location: birmingham UK
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
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Old 1st March 2004, 01:20 PM   #12
MR2_ICE is offline MR2_ICE  United Kingdom
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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
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Old 1st March 2004, 02:27 PM   #13
sreten is offline sreten  United Kingdom
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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.
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Old 1st March 2004, 04:47 PM   #14
MR2_ICE is offline MR2_ICE  United Kingdom
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Location: birmingham UK
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
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Old 1st March 2004, 06:34 PM   #15
sreten is offline sreten  United Kingdom
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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.
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