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PostPosted: Tue Feb 23, 2010 12:08 am 
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Joined: Mon Feb 22, 2010 11:35 pm
Posts: 26
Location: Vancouver Island, BC, CAN
Hey guys,

Just wanted to confirm with my fellow canucks that the system I am about to install in my car has enough amp to it.
Also, if you can recommend anything during the install, or some little quark about this system...

Car is a 1972 Datsun 240z (think: Small, big engine bay, 2 seats and a "rear hatch area")

HU = Eclipse CD 5000
EQ = Ph.Gold EQ215i

Midwoof/tweet/xover = Dragster 5.25" mid / .75" tweet / 4ohm with 75 RMS (140 max) / 60-25kHz (12dbB/oct x-over)
Sub = Ph.Gold 12" (4ohm) "XS124" subwoofer. I have been unable to find the RMS or Max anywhere. Not even a manual.

Amp = PC4400 (400W PowerClass). 100 WRMS x 4 @ 2Ω per channel .
If I bridge two of those amp channels for the sub, I'll have
(2) 100 WRMS 2Ω for the speakers, and
(1) 200 WRMS x 2 @ 4Ω.

Am I going to damage anything?
Should something be changed?

This is my first speaker install ever.
Sorry for sound so amateur in such a professional group of people.


EDIT: Wow... after writing that... I guess one of my questions should be "Does anyone know the RMS/Max of the Phoenix Gold "XS124" (4Ω version)?


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PostPosted: Tue Feb 23, 2010 6:56 am 
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Joined: Sun Feb 06, 2005 1:54 pm
Posts: 1514
Location: Calgary, AB, CA
The Precision Power PC4400 only puts out 50 x 4 into 4 ohms.

I'm not sure why you think you'll have 2 ohms on the front speakers...they're 4 ohm speakers so you'll only have 50 watts a side no matter what. Using both tweeters and mids doesn't lower the impedance of the load shown to the amplifier as each is nominally 4 ohms operating in it's own unique frequency range.

As for the sub, if it truely is a dual 2 ohm voice coil you have two options, both if which will provide the SAME power:

a) wire the voice coils in series for a 4 ohm load and then hook that to two bridged channels of the amp (effectively a 2 ohm load to the amp, so you'll get 200 watts in theory to to the sub)
b) wire each 2 ohm voice coil to it's own amp channel so each puts out 100 watts (a total of 200 watts) to the sub

You CANNOT run that amp with the voice coils of the sub wired in parallel and the bridge the amp; this would give you a 1/2 load and the amp will surely shut down or simply blow up.

I used a similar Precision Power amp in a similar setup a few years back and it sounded ok, but it definately wasn't especially loud. If you want SPL I'd suggest bridging your amp for the just the front speakers and adding a class D mono sub amp.


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PostPosted: Tue Feb 23, 2010 11:46 am 
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Joined: Mon Feb 22, 2010 11:35 pm
Posts: 26
Location: Vancouver Island, BC, CAN
The front speakers are pretty sensitive (91dB). Looks like I'm in the market for a Mono amp.
Quote:
if it truely is a dual 2 ohm voice coil

I honestly don't know what this means. The instruction booklet is lost in shipping... all I can gather from the box is
"12 in 4 ohm subwoofer"

Quote:
I'm not sure why you think you'll have 2 ohms on the front speakers...they're 4 ohm speakers so you'll only have 50 watts a side no matter what. Using both tweeters and mids doesn't lower the impedance of the load shown to the amplifier as each is nominally 4 ohms operating in it's own unique frequency range.

Yes. I was wrong, who knows what I was thinking.

Thanks for letting me know. I was about to install this system as is, you just saved me from blowing something up (a fuse or otherwise).


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PostPosted: Tue Feb 23, 2010 12:55 pm 
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Joined: Tue May 19, 2009 7:51 am
Posts: 58
Location: ottawa, ON, CA
I've got a 77 280z.... good luck getting all that in there!
:lol:


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PostPosted: Tue Feb 23, 2010 12:59 pm 
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Joined: Mon Feb 22, 2010 11:35 pm
Posts: 26
Location: Vancouver Island, BC, CAN
I'm thinking of fibreglassing two kick pods by the driver/passenger feet area, as well as one larger enclosure for the 12" in the spare tire well.
I just ordered some bucket seats (to comply with harness regulations at the local track), and don't think I can mount any of the other hardware to the back of the seats... this will be intersting, actually. I always figured I would just bolt the EQ and Amp to the back of each seat.
Now I have a second amp and can't use the seat's...

-- 27 Feb 2010 03:35 --

Can anyone else tell me that it is not a good idea to run this system "as is"?


If the speakers can only handle 70W per channel, then is it really a good idea to supply them with 200?

Why not supply 50WRMS to each speaker, and bridge the rears for 200WRMS?
A little underpowered, but is it really something to be concerned about?


From the amp spec sheet for the Powerclass 4400
50 WRMS x 4 @ 4ohm per channel
100 WRMS x 4 @ 2ohm per channel
200 WRMS x 2 @ 4ohm bridged


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