Seppeku

Sorry for the total noob question, but here goes...

If you want the amp to run all 4 speakers and a sub, do you need a 5-channel amp?
Can you let the amp run the front two speakers and the sub, then let the HU run the back two speakers and just buy a 3-channel amp?

This weekend I'm installing a new HU, 6.1 Perfects up front, and an amp to run them. I want an amp with the option of adding a sub and/or quality rear speakers later. What kind of amp do I need to buy? Any opinions on brand and/or model???

Any help is greatly appreciated!!!

Kame

Yes to both questions.

I've got an alpine 4 channel amp running the fronts and 2 channels bridged to run the sub. I just left the bose amp in to handle the rears.

I've heard it's best to use separate amps instead of using a 5 channel to run everything, but I don't know too much about car audio.

Good luck with your install.

bastard

Your amp choice depends on which sub you plan to get, so until you know that, it would be difficult to decide. If you use a 4 channel amp with one pair bridged to run a sub, you are limited in what subs you can use.

Most bridgable amps are good for 2 ohms stereo (not bridged) and 4 ohms mono (bridged). When bridged, this limits you to 4 ohm (or higher--wasteful) impedance subs. You can obtain 4 ohms by using:
- 1 single 4 ohm voice coil subwoofer.
- 1 dual 2 ohm voice coil sub wired in series.
- 2 dual 4 ohm voice coil subs wired in a series-parallel configuration.

If one uses a so-called "monoblock" amp--either a single channel amp (hence "mono") or the 5th channel of a 5 channel amp, it will minimize these considerations since the mono channel should be capable of driving a 2 ohm load at least.

One must also take power ratings into account. The RMS power of an amplifier should be very close (preferably a bit higher) than the subwoofer's RMS power requirement. Peak power or "Music Power" ratings are practically irrelevant. Use RMS power as a guide.

Another consideration that is often ignored is the efficiency of an amplifier. Some of the high current amps use a lot of amperes to make their power. Class AB amplifiers aren't very efficient either. Look for a class D subwoofer amplifier. Some 5 channel amps have a class D sub channel and use ABs for the 2 stereo pairs. AB amps are more desirable for full-range applications.

Basically: Choose your sub, and then decide on the amp for it.

Good brands include: JL Audio, Soundstream, Zapco, some Phoenix Gold, etc. I recommend the JL Audio amps without reservation.

Seppeku

Good info Bastard, thanks...

So, with all that, I think I'm reading just to buy the amp right now to run the front and rear speakers. Then when I decide on a sub, get another amp just for the sub? Two amps total???
I just can't get the sub right now, but I wanted to set it up for a sub later. Is running one amp for everything a bad thing or can I go with a 3 channel for front speakers and sub?

Thanks for all the input...

bastard

A single amp system isn't a bad idea. I was just pointing out that a 4 channel amp bridged into 3 channels (2 fronts and a sub) will limit what subwoofers you can hook up to it because bridging doubles the safe load--a 2 ohm stable stereo amplifier is only 4 ohm stable when bridged. This rules out any speaker that will be a load lower than 4 ohms when connected to a single channel.

Depending what subwoofers you would be considering, you could buy a 3, 4, or 5 channel amplifier now and install the sub later.

An amp I have heard to be quite good is the JL Audio 500/5. it gives 100x2 for the fronts, 25x2 for the rears, and 250 watts for a sub, which is more than adequate for an average subwoofer. Another JL that might work is the 450/4 which has 150x2 and 75x2. Bridging the 150 watt channels gives you a single channel with 300 watts for a sub, and still gives 75 each to your front speakers.

There are many good subwoofers in the power range of these two amplifiers.

www.jlaudio.com

Seppeku

The 6.1 Perfects are rated at 100W RMS, is 75W going to be enough?
How many watts should I try to pump into a sub? Say if I just went with a single 8" or 10"...

Could I get by with a 3 channel, one for each speaker in the front and 1 for the sub. Do they make an amp that puts out that kind of power on all 3 channels???

Thanks again for the info...

dczoner

iTrader: (1)

If you want to make your money stretch as far as possible I would advise going with a 2 channel right now, but installing your fuse box and running the wires to add a dedicated subwoofer amp down the road. That way when you purchase your sub amp and sub; all the wires will be there. Literally your amp install ought to take like 12 minutes.

I like the JL products, but they are expensive. 300/4 (I think... that might be an old model...) means 75 x 4 @ 4ohm... MORE than enough to run just about any speakers.

Figure RMS does not actually mean RMS for speakers. A speaker under normal listening levels (ie above road / wind noise) will require roughly 5-18 watts of power. At higher volumes and more complicated, especially bassy parts in your music; your speakers requirements will go up. 75 watts is basically saying "you CAN throw 75 watts at me all day long and I'll play it without distorting. - but you really won't want to."

And to answer the subwoofer question the answer tends to lie in what type of music you listen to (although not 100%, just another good rule of thumb). If you like Hip hop / rap, go 10"-12". If you want to offend neighbors / get noticed - 12"'s no doubt. Rock music and country music tends to perform better with 8-10". If you're all over the spectrum, a single 10" ought to work fine.