Car Audio DIY - Tips and Tricks

[Boclive]

So I bought an eleven year old Dodge p/u 4x4 and the cassette deck appears to play a little fast. It's not too bad, maybe only 1 to 1.25. I only own one cassette that I bought about 22 years ago in Saudi Arabia. This is not what I want to talk about.

I have fallen into a used PHOENIX DIGITAL PD-394 (PD394)
4-Channel 1000W amplifier w/ Fan Cooling System mounted on a box with two pioneer 12's:

This unit slides into the trunk of my 10 year old '01 Monte Carlo perfectly and with the rear seats down it looks like this is the car for which it was designed:

The Chevy has the stereo it came from the factory with and there is an amplifier mounted under the rear deck. That sounds pretty good already although I regret not having an input jack.

My question is this: should I try to hook the new amp up using existing wiring or should I hook it up independently (power) with parallel audio?

Basically, I'm looking to avoid WORK here. I am strongly considering hiring a younger criminal to hook it up for me.

Anyone on TideFans interested in Car Audio?

 

[cbi1972]

So, you currently have the factory head unit, with an amp in the back powering 4 main speakers?

Since there is already an amp installed there, you could try piggybacking off that cable, but if it is too thin, you will either get bad sound, or your headlights will dim when the bass hits, or both.

If it were me, for a 1000W amp, I would run a fat 2 or even 0 gauge cable from the trunk, up to the battery, with an inline fuse, and hook both amps up to a distribution block. But I like to do things right, i.e. more work, more expense, but much better results.

Depending on your existing amp, you may not have to run any more signal cable. My main amp has an RCA passthrough output that I use as input to my bass amp. If your amp doesn't have one, I make a sad face for you

You mention a Dodge pickup and a Monte Carlo.
What are you installing this in?

 

[Boclive]

It's going in the car, thanks for asking. The old truck doesn't even have working air-conditioning.:frown:

I believe it's going in as you suggest; power from the battery, with an inline fuse, and only power the two subs off of the amp, leaving the factory installed amp and four speakers alone.

There are no RCA out jacks on the factory installed amp, whether there is any audio out available from that amp I don't know... the plan is to include an aftermarket RCA pass-through block of some kind particularly if I don't get a new head unit. I'm paying a kid the $70 to do the install. The kid says it will sound good, I'm not sure with one small amp powering the four factory speakers and one big amp powering the two subwoofers. Still debating on getting a new head unit and how much I might be willing to pay for one.

 

[cbi1972]

It's going in the car, thanks for asking. The old truck doesn't even have working air-conditioning.:frown:

I believe it's going in as you suggest; power from the battery, with an inline fuse, and only power the two subs off of the amp, leaving the factory installed amp and four speakers alone.

There are no RCA out jacks on the factory installed amp, whether there is any audio out available from that amp I don't know... the plan is to include an aftermarket RCA pass-through block of some kind particularly if I don't get a new head unit. I'm paying a kid the $70 to do the install. The kid says it will sound good, I'm not sure with one small amp powering the four factory speakers and one big amp powering the two subwoofers. Still debating on getting a new head unit and how much I might be willing to pay for one.

Does the amp at least have RCA input? I guess you could use some Y splitters there.

What is your concern about one small amp powering four main speakers, and a large amp powering subs? That is a fairly standard setup. Main speakers need a LOT less power than subs, and unless your speakers are really good or your amplifier's gains are set so high that they clip signal badly, speakers will start introducing distortion long before amp distortion would be noticeable.

I looked up the amplifier you mentioned, and it seems like a real cheapie. It may say 1000W, but I would be surprised if you got good clean signal at rated power.

The main thing you would get from a new, inexpensive head unit is probably coolfeatures. Playing MP3s, having a better assortment of inputs and outputs, playing from USB stick, things like that. I would totally disregard power ratings on head units if you are going with external amplification.

I also look for a high signal to noise ratio and total output voltage, along with good reviews, but these tend to correlate strongly with higher price. The purpose of S/N ratio and total output voltage is to get clean, loud sound. If you start with a 2 volt preout signal and a low S/N ratio, by the time you're done bumping it up to a loud volume with more amp gain and volume control, you have introduced a lot more noise. With high S/N and say, 5V or 8V out, with lower amplifier gain, you have much less noise, and can listen louder without it sounding harsh. It can be surprising how great music can sound at loud volumes if it is still clean.

In most audio systems, you will get the most bang for your buck buying good quality speakers. The best components will ultimately sound bad if the speakers are not good.

I would place components in the following order of importance:
Speakers
Amplifiers
Install quality
Head unit

Unfortunately, one of the factors that makes the most difference is the least under your control, and that is the construction of your vehicle. The system I am currently using sounded incredibly awesome in a BMW 3-series convertible, but when I transplanted it into a Lexus GS400, the solid trunk construction practically killed the bass. I have new gear ready to be installed, but I am seriously considering saving it for another vehicle.

 

[Boclive]

Does the amp at least have RCA input? I guess you could use some Y splitters there.

You know, it has a plastic wiring harness connector PLUG into the amp. As you suggest and as I'm now learning separate amps are fairly standard.

Everything else you say makes perfect sense, too. The factory speakers still sound fine to me, the car itself is real quiet on the highway without rattles, squeaks, or hums. Just as you say, an aftermarket head unit will bring my mp3 player and XM radio into play AND will include RCA outputs to the new (used, free) subwoofer amp.

It appears as if I'll be driving this car another couple of years so I am strongly considering a new head unit like this one:

 

[cbi1972]

It appears as if I'll be driving this car another couple of years so I am strongly considering a new head unit like this one:

Looks like a decent unit. I recommend reading all the reviews you can find.

Things I like about it:
1) 98dB CD S/N ratio is high, on par with my Eclipse that cost a lot more 5-6 years ago.
2) USB input
3) Aux input on the front so you can plug in anything without doing dashboard surgery.
4) 2 preamp outputs

Things that would bother me that may not matter to you:
1) 2.5V output voltage is low for high volume/high sound quality applications ($$$$), but perfectly adequate for normal listening. You would absolutely never notice this with factory speakers.
2) Double DIN form factor is large for a unit that doesn't have GPS or touchscreen. It may limit what you may put it in, if you ever change vehicles.
3) CD tray is exposed, so will get dusty over time. My faceplate flips down for CD changing.

 

[Boclive]

2) Double DIN form factor is large for a unit that doesn't have GPS or touchscreen. It may limit what you may put it in, if you ever change vehicles.

Might not fit in THIS vehicle. I'm taking it in tomorrow to have the subs hooked up and if they have a new head unit that suits me, that too.

I'll let you know what I think about it after I listen to it some. Thanks for the input, and thanks for not getting too small with the cross-over math.
(although I imagine that stuff probably has a direct effect on how it sounds). :smile:

 

[cbi1972]

Might not fit in THIS vehicle. I'm taking it in tomorrow to have the subs hooked up and if they have a new head unit that suits me, that too.

I'll let you know what I think about it after I listen to it some. Thanks for the input, and thanks for not getting too small with the cross-over math.
(although I imagine that stuff probably has a direct effect on how it sounds). :smile:

Crossover is a sort of a confusing name for a frequency filter.

I play with crossovers by how it makes my music sound, which is totally subjective. No math.

Your speakers have a frequency range at which they perform optimally. At the edges of that range, they won't be able to reproduce the sound well. Your subwoofers also have an optimal range. The crossover frequency is where you decide to shift the burden of sound reproduction from main speakers to the subwoofers.

It can be a subtle difference where you have overlap between their capabilities and good sonic matching between speakers. Somewhere around 80-100 Hz, you will probably find a sweet spot. If you try to make 5 1/4 inch speakers play loud at 40 Hz, you will get poor results. Similarly, if you try to make 12 inch subs play 150 Hz, you will be wasting amp power and getting minimal sound.

If I try to go too loud with low frequencies out of my main speakers, they will ultimately distort because they cannot effectively reproduce low frequencies at high volume. That's what the subwoofer is for, relieving the strain of trying to play bass on speakers that are too small for it.

The crossover frequency controls how much low frequency I allow my main speakers to reproduce. The smaller my subs, the more I can offload from the mains and still get a good sound. However, the larger my subs, the lower frequencies I can reproduce.

I currently have two 10" subs, and notice a dropoff on some really low frequencies in some songs by Sublime (New Song and April 29, 1992) and 2 Live Crew (Hoochie Mama). But everything else I listen to sounds good.

I have some 12" subs waiting, that wouldn't fit into the car I had when I originally built the system. If I install them, I may have to lower the crossover setting to match them with the main speakers, which would affect how loud I could play my mains and still sound good. The best thing would be to have a pair of 12s and a pair of 8s, but that's not the easiest thing to do, of course costing $$$$ and complicates the install. For now I am willing to sacrifice a few low notes in a few songs for the sake of loud and clear sound overall.

 

[rizolltizide]

1000 watts. That's pimp, yo.

 

[Boclive]

1000 watts. That's pimp, yo.

This is more or less the position Mrs. Potato Head has taken on the subject. :rolleye2:

 

[cbi1972]

This is more or less the position Mrs. Potato Head has taken on the subject. :rolleye2:

Play something you both like when she rides with you. Make it sound good.

 

[Bama Reb]

Basically, I'm looking to avoid WORK here. I am strongly considering hiring a younger criminal to hook it up for me.

Two things to think about. 1. For every problem, there is a quick, easy, cheap, wrong solution. 2. It's easier to do it right the first time than to have to go back and do it all over again.
JMHO