4 speakers, 2 channel amp, 1 crazy idea

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alrighty ladies and gentlemen I have a crazy plan and I was hoping to get input from someone who actually knows what they are doing. I bought a cheap stereo and speakers for my wifes car and now i'm trying to patch it up with more cheapness. I have 4 good 6x9's I would like to install in her car and a 2 channel amp..it only says 300w max I'm assuming the RMS is probably half or at least hoping..so for all figures forthwith let us use the 150Wrms figure.

The head unit in the car doesn't put out enough wattage as of right now and I was wondering if it would be practical/possible to install the 4 speakers and wire them all into the 2 channel amp? Everything initially is 4 ohm I believe. I was thinking I could connect both left speakers to the left channel on the amp and both right speakers to the right...what are the implications of this? what sort of wattage/ohm issues do you forsee? The amp I have can be switched for high/full/low so I'm assuming I would need it to be kept at full...

someone let me know if i'm crazy or if this is a workable solution..

thanks!
dlv
 
it`s a workable deal.if the amp is 2ohm stable.
and it work for awhile if it`s not.
or you can run them in series,keeping them 4ohm,2 left and 2 right.
to do them in series run the +of the amp to the+ on 1 speaker and the - of that speaker the + on the other speaker and the - of that speaker to the - on the amp.that is 1 chanel in series.
so the choice is yours.
 
ORB,
the series connection will give 8 ohms a side.

MG,

I assume the head is 4 channel ?

It is normal practise to run the the front two speakers off the
head, usually it can manage more power only driving two
channels. Usually the front speakers can't produce decent
bass.

Its then normal to place the rear 6x9's where they can produce
bass and drive them off the amplifier and set the amplifier to low.

After some setting up then the front/back control will control
the richness of the sound.

If the amp is 2 ohms stable 4 6x9's at the back is possible.

:) sreten.
 
so you think it might be best for me to run the 2 front speakers off the head units amp (which is kinda quiet when running all 4 speakers and let the standalone amp push just the back speakers? How will I wire up the front 2 speakers to the head unit so they get essentially half of the wattage of the head unit to each channel? And then I would presumably connect the 2 rca pre-amp's to the amp and then just wire it to the 6x9's in standard fashion...i'm worried that the big amp on just 2 speakers might be overkill. I'm just looking for the cleanest power solution with what I have already..any wiring diagrams you could point me to would be great as well :)

thanks!
 
ok..so when I amp them all how should I wire them? I'll be coming out from the 2 pre-amps (which i assume is basically a "line-out" for all frequencies correct). Then how should I wire the 6x9's? Obviously I want to put both the left speakers on one channel and both the right on the other...perhaps I should get one of those high pass filters for the front speakers from radio shack? xover @ about 200hz? helps me make the most of this sorry stereo system! What will the specs be as well? assuming it's 150w will I be getting 37.5Wrms per channel? I believe I read somewhere that when you run speakers together is ends up halving the wattage again which would leave me with only about 18w/channel which would be undesirable..thanks for the input thus far!

thanks!
dlv
 
offroadbum said:
sreten,your right sorry about that it was about 1am and i wasn`t will the clearest of heads.


excuses excuses... its nearly 2am here and I'm not blaming that for my terrible spelling typing punctuation and stuff like that that you might have truble wif at sum stoopud our of da mornin.... :D its all natural my friend.. no sleep induced stupidity here.... what was this thread about? :xeye:
 
muskgrave said:
The head unit in the car doesn't put out enough wattage as of right now and I was wondering if it would be practical/possible to install the 4 speakers and wire them all into the 2 channel amp? Everything initially is 4 ohm I believe.

You could try your idea and run all 4 if the amp is 2 ohm capable.

But if you want the best possible quality from the system, you should concentrate on the front speakers. Imaging and sound stage are compromised if you have the main speakers behind you. For that reason, most people amp the fronts and leave the rears on head unit power if you only have 2 channels of amp available.

The amp I have can be switched for high/full/low so I'm assuming I would need it to be kept at full...

Normally we would hipass front speakers at 50-80 Hz and rely on subs to handle the low end. That lets you put as much power into the front speakers as possible without "clicking" from over excursion. But without subs you'd run them full range and just keep the bass equalization low.
 
ok so power the back with the head unit..

*QUESTION*:what is the best way to wire them up so I get the full wattage of the head unit to the speakers? I'm assuming it doesn't dynamically dole out wattage depending on which speakers are attached..should I hook it up like this:

From Speaker: -BL wire to -BL and -FL on head unit
-BR wire to -BR and -FR on head unit

same for +BL and +BR

and power the fronts with the amp..I'll just set these up in a "standard" 2 ch amp configuration and keep the amp level down.

???????????????????????????????????????????????????

I think thats about the only question left...Once I know how to do that I think i'm good.
 
no the amp section in most (99.99%) of head units is not bridgeable however if you only hook up two speakers (to the rear outputs in your case) it will put out a little more power than o those two than it would to 4 because the rail voltages stay alittle higher in the amp section with less load.. you share one power supply in the amp for all four chanels...........
 
okie dokie

ah ha so my head unit is dynamic to a small degree with it's little amp..i'm just worried that it won't push out enough since it will have the drive the bass as well. Actually i suppose it really won't need to since the 6x9's in the front will supply bass as well and the back speakers will just kind of complement the fronts...so i'll leave the amp set to full in this case...

dlv
 
paint a picture for me now...

ok so i found out my amp is 70w rms per channel. but i noticed there are 2 inputs on it..one is dual RCA and it says "low" and another is a plastic block with 4 pins and says "high". there is also a switch on the amp that has the options high/full/low...my brother in law said when he hooked it up using the rca "low" input it still played the mids and highs as well..if anyone knows what i'm talking about please ease my fears..i want the amp to push all frequencies to the front speakers and LOUD...then of course all freq's to the back but not as loud just to complement the front...

lead the way capitan
 
both inputs on the amp are the same, just that one has an internal voltage divider so you can use the speaker output on the headunit to get an audio signal into the amp.

so, the filters will have the same effect on both inputs.. :)

if you do parallel the speakers, they will all be just as loud as each other... but this shouldn't be a problem as the rears are further from you than the fronts, and should therefore sound slightly quieter :)
 
sitting on the fence...

so now i'm torn again between running all 4 speakers off the amp or the 2 front off the amp and the 2 back off the HU. If I run all 4 off the amp then i'll effectively be getting about 18w/channel correct?...i'm still worried about how to get the 6x9's where the 5x7s went..i suppose i'll figure that out once i get the door panels off :p..
 
"Crappy" amps typically don't do well with 2 ohm loads. You'd likely be best off amping the fronts only.

And if you don't already have speakers, squeezing 6-1/2" rounds in the doors will get you better sound quality than ovals. It also opens the door to more serious upgrades in the future.
 
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