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Amp/Speaker Questions

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5 replies to this topic

#1 of 6 OFFLINE   Phil McC

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Posted May 18 2007 - 01:15 PM

Ok I am on the beg for some help! I have a 98 Jeep Grand Cherokee Laredo which I will be shortly be giving to my son as his first car. It had a factory head unit with four factory speakers. One of the rear speakers is dead (checked by switching it for a front and it does not work there either!). So I decided to "ICE" it up a bit for him! I put a new head unit in it which works fine, and a colleague at work gave me a new 550 watt 2-channel amp with 4 new three way 6 34" speakers which will fit the Jeep. He was clearing out after his son left for college and told me to get them fitted quick before his boy comes home for them - nice! I also have a slightly used Pioneer 12" sub in a box. The sub is rated 800 watts peak power (150 watts nominal). The four speakers are rated 135 watts peak each (50 watts RMS). I know I can run the sub on it's own in bridged mode on this amp. I also know I can parallel off the pairs of speakers (left and right) and use this amp for them, albeit that I would lose fade control front to back. I have also seen a wiring diagram somewhere for using the two channels for the speakers and also bridging for the sub but this seems dodgy. I think therefore that I need another amp. My questions are as follows:- If I can use a 2-channel for the door speakers should I use the one I have or would I be better using that for the sub and getting another one for the speakers bearing in mind the ratings of everything? Is the 550 watts enough to drive the 4 door speakers? Would it need to be a four channel for the door speakers to give me the fade control back? Will the fade even work if I am using the low level RCA output from the head unit to the amp? If I use this one for the door speakers, do I just need another bridgable two channel amp for the sub woofer rated at up to 800 watts peak output? Anyone know where I can find a formula for all this stuff (and the money to finish it now I started it? :-) Thanks in advance - if you can't answer all of them at least answer some of them!!!! Cheers.

#2 of 6 OFFLINE   Robert_J


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Posted May 21 2007 - 01:24 AM

Give us some band names and model numbers. A 550 watt amp from Pyramid is really only about 20 watts of clean power. A 550 watt amp from JL Audio is 550 watts of clean power and can easily smoke some door speakers. The bridging issue can also be answered with model numbers. -Robert

#3 of 6 OFFLINE   Greg_R



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Posted May 21 2007 - 11:14 AM

550 clean watts is a ridiculous amount of power for door speakers (we're talking about daily drivers, not competition cars). Let's assume the 550W amp is decent... it will drive the sub nicely. You then have a few options: 1) Take the 550W amp (or other 2ch amp) and hook it up to the front and rear speakers (each side in parallel). This will work but you won't be able to fade between front and rear. 2) Get a 4 channel amp and hook up each speaker... this will allow you to fade. 3) Use the amp in the head unit. This will drive the speakers but an amp upgrade will be noticeable. Be sure to talk to your kid about appropriate volume levels and hearing loss. A lot of my friends who were into car audio as kids now have hearing damage.

#4 of 6 OFFLINE   JLAudioCavalier



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Posted May 22 2007 - 02:31 AM

so just to simplify what im reading here...
your sub will handle 150 watts RMS(peak power is going to be next to useless when setting things up here).
Your speakers will handle 50 watts RMS
You have a 2 channel amp that puts out a currently unknown amount of power per channel... find out what the RMS output per channel is at 4 ohms, 2 ohms, and bridged into 1 channel at 4ohms(it most likely is not stable down to 2 ohms when bridged).
These few things will greatly help determine just how usefull that amp is realy going to be.

Lets assume the amp is of good quality and give u decent clean power...I would say a safe bet would be to find a 50-100 watt per channel(RMS at 4 ohms), 4 channel amp for the speakers(although i could get into a frontstage rant about ditching rear speakers and upgrading everything, but that clearly is not your intention), and then bridging the amp to the sub.

But another good point along those lines... what is the voice coil configuration on the sub? if it is single 4 ohm or dual 2 ohm coils you are good to go, if it is single 2 or dual 4, that amp wont be able to do it for ya.

At any rate
-What model is the amp? RMS output at each impendance?
-What is your total budget for this project?
-What is the listening taste and style of the end user?

ALSO: for quicker replies and more people able to help in this area check out CarAudioForum.com try to get past the immaturity and outright annoying people... there are quite a few of us on there that are eagar to help and know what we're talking about. Posted Image

#5 of 6 OFFLINE   Phil McC

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Posted May 28 2007 - 05:50 PM

Thanks for all your advice despite my complicated first post! Here's what I did just for interest. I wired the 550 watt amp 4 ohms bridged to the sub. This gives me 220 watts rms to the sub which is plenty. The 4 door speakers were rated 140 watts max at 50 watts rms. I purchased a 4 channel amp rated 110 watts per channel (55 watts rms at 4 ohms). All installed and working and sounds pretty decent considering I got most of it for nowt! Spent some time wiring the door Molex's to finish the wiring properly, and had to redrill the mounting holes for each door speaker as they would not fit the factory mounts. Greg, I note your concern about noise levels and as one who is partially deaf myself (mainly to too much exposure to naval gunfire!) I will certainly be having that conversation with my boy. Thanks again!

#6 of 6 OFFLINE   yinger



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Posted May 29 2007 - 02:23 PM

The bridging issue can also be answered with model numbers.

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