The 3 rules of car audio.

Bochek · Post by **Bochek** » July 13th, 2006, 4:11 pm

These are not the only rules, but 3 main things to remember when looking at buying car audio equipment.

Rule #1 DONT GO BY THE BOX (or label for that matter)

Just because a deck is rated at 50x4 (200w) DOES NOT mean that is what it will actually put out, same goes for amps, just because its rated at 10,000 watts, does not mean it will put out 10kw. Il explain how you can tell what a amp actually puts out later.

Rule #2 You don't always get what you pay for when it comes to car audio.

Perfect example, i was at a unnamed department store not a while ago, and they had a car audio amplifier rated at, 10,000 watts mono (it was a 2 channel bridgeable amp), the thing was probably 2.5 to 3 feet long. The amplifier sold for $1200 Canadian. I looked up the specs on this amp, it was 10,000 peak watts, with a RMS rating of only 400 watts (at 2 ohms bridged). Which means it actually is only 100 watts per channel at 4 ohms stereo.

So that works out to about 3$ per watt, and a lot of missing trunk space.

On the other hand, the amp i have powering my subs (orion HCCA 225) is rated at 25x2 thats right only 50 watts. But thats at 4 ohms stereo. The quality of that amp allows it to have extreme loads placed upon it and still function properly. So basically you can bridge the amp and get 50 watts @ 8 ohms. The amp is “0.5 ohm stable” meaning you can load it down to 0.5 ohms of resistance. OR you can actually get 1x800 @ 0.5 ohms bridged. BTW this amp retailed for ~$800 back in 1980 something.

That works out to about 1$ per watt. And its a SMALL amp, granted it does get hot.

Rule #3 It takes a lot to get a little.

It takes double the amount of power (watts) to gain 3db. So if your making 100db of noise at 100 watts, it takes 200 watts to make 103 db of noise, and 400 watts to make 106db of noise.

See my point.

When ever you buy a speaker or sub woofer somewhere on the box or label it will state the speakers efficiency. This number is measured in the units of db. measured at 1 watt of power, 1 meter away from the speaker. Efficiency is one of the most important parts of a speaker. If you spend a little more money on a speaker with higher efficiency then you can save quite a bit more money by buying a less powerful amp.

For example. A speaker with a efficiency level of 90db compared to a speaker with efficiency of 100db and you want a system that can hit 120 db.

1 watt 90db – 100db
2 watts 93db -- 103db
4 watts 96db -- 106db
8 watts 99db -- 109db
16watts 102db -- 112db
32 watts 105db -- 115db
64 watts 108db – 118db
128 watts 111db – 121db
256 watts 114db
512 watts 117db
1024 watts 120db

as you can see, the more efficient speaker reached the same sound level as the less efficient speaker, using 896 less watts. BIG DIFFERENCE EH!

Well thats it for now, i will post another article on creating a balanced audio system, proper components to use, proper wiring and other stuff later.

Bochek

verzutiko · Post by **verzutiko** » July 14th, 2006, 10:34 am

Looking forward to it, especially as I'm in the process of buying stereo components for my car.

Vanished · Post by **Vanished** » July 14th, 2006, 2:59 pm

Hey man, defantly a start on a good thread, could be very usefull good job..

hahaha...it's funny that your still running your el-cheapo setup in your car hah...

Bochek · Post by **Bochek** » July 14th, 2006, 3:05 pm

Vanished wrote:Hey man, defantly a start on a good thread, could be very usefull good job..

hahaha...it's funny that your still running your el-cheapo setup in your car hah...

lol it will stay like that for a while, even tho it looks cheap, and well, it is cheap, it sounds good and its more then loud enough for me, ask fierromx3, i think he heard it at the MMM.

i might upgrade the subs to clarions soon. but thats probably it.

Bochek

reaper of souls · Post by **reaper of souls** » July 14th, 2006, 6:03 pm

you forgot one rule (ok it's not really a rule but ) unless you take the time to tune your car your not going to get anything good out of it.

my system makes is making great sound it not the el cheap o system but it's not look at me i sell drugs and own a civic and spent way too much money only to recreate on NOTE from my entire system kind!!! either. start off with a good head unit and go from there if your sending a crap signal you'll get crap sound!!!!!!

Cy · Post by Cy » July 15th, 2006, 12:21 am

i'm building a Deckless sound system from Fshop for under a grand.. Ipod Powered via Line-Out dock.

starting off with what i bought today.
Panasonic 6.5inch 3-ways... They're a bit perky but nice sound and once i kill most of the bass out of them they'll be fine..

Next some 6x9's mounted in the rear then a 4x100w Amp and an EQ..Who needs a Deck when I could get a digital signal processor and get 5.1 from my Ipod

...

jschrauwen · Post by **jschrauwen** » July 15th, 2006, 3:24 am

Cy wrote: I could get a digital signal processor and get 5.1 from my Ipod ...

You'll need a 5.1 signal processor also. It's unlikely you'll stay under $1,000 if you factor a cost for that signal processor at approx 500 to 600 for a psuedo good one + cost of IPOD + cost of speakers.

PATDIESEL · Post by **PATDIESEL** » July 15th, 2006, 5:08 am

The next subject should touch on amp class ratings (means alot more about the power quality and stability of the amp) The more expensive amps are usually class D or A/B and the watt ratings of these amps are much more accurate. The amp does not fluctuate watts as much if rated. example, a bass heavy song at high volume will drain most amps of power and they will drop in watts. A CAP will help, but it will be a much smaller drop still if you use a rated amp.

Read up before you buy. There are tons of stereo magazines and just like you wouldn't spend 1000 on struts before getting some feedback, you shouldn't buy any stereo equipment before checking some professional opinions. EX: I just bought a new headunit to replace my 10 year old Pioneer. I almost always buy the second best of a brand line so that I get the newest tech, but not all the expensive features. I had a Kenwood that was about 6 years old, but it only lasted about 3 years and I replaced it with the Pioneer that I took out to put the Kenwwod in! It sounded better than any headunit I have ever heard, but at 500 bucks I expected it to last longer than 3 years. Come to find out that Kenwwod produces an awesome product bt many pors find that they don't last long. (wish I had done my research the first time..)

reaper of souls · Post by **reaper of souls** » July 15th, 2006, 4:05 pm

you will do always need a signal prossecor but you would need a deck for it you can wir up a speaker mono between the two front speakers and make a fake center channel but don't mess with your balance or you'll lose the speaker

also running your system off your ipod is not a good idea your going to be lossing a lot of power and as soon as you get to a good enough volume it going to be compleatly distortion and you ipod wont put out enough of a signal to the amp . for the price of the i-pod dock and the eq you can get either a kenwood or jvc or sony head unit with eq setting bulid in and a line in on the front of the deck face (jvc and sony only kenwood runs a set of rcas on the rear of the deck) you'll end up getting better sound aswell a amp wouldn't be required, depending on the amp you can hook it up to amp the speakers but see as it's probley only 100w peak you would be better off running it for only the front door speakers.

As for amps

Here is what I look at when choosing an amplifier, and in their order of preference:

1. Power. I know, this is where MOST people look first, but it's the very reason you are buying an amp, right? Also knowing Ohm's Law, and knowing that I will almost always load an amplifier with the maximum specified impedance (impedance - 4 ohms or higher, NOT load - 4 ohms or lower), I need to know exactly how much power I am looking at to start with. When loading an amp with a higher impedance, the amp will make less power, so I have to keep this spec in mind the whole time. My speakers are almost always chosen before I decide to start looking for an amplifier, I know the impedance and efficiency numbers when I start. This will help me decide how much power I need or want for that particular driver compliment. I will NEVER look at "Max Ratings". They are often worthless, generally overinflated, selling tools, designed by old-school, low-end amplifier companies, originally made to sell product. (You remember how it went (and still goes today)... This 800 watt amplifier is only 200 dollars, but the Nakamichi 160 watt monoblock is 1300 bux for the pair. Which were (are) YOU going to buy?) Ahhhh, the power of advertising... Classic Nakamichi, Alpine, Linear Power, Orion, Eclipse, etc., THEY never posted "Maximum Power" numbers, did they? Unfortunately, even the good products of today will state maximum power output, I just disregard the numbers posted.

2. Signal to noise ratio. This one I place a bit more weight on, especially when the amplifier is going to be used in a mid-bass (important), mid-range (more important) or highs (MOST important) application. The higher the better, and there is no exception to this rule for me. Amps with tube stages are typically less capable than their solid state stablemates in this area, but I do make exceptions for tube amps. It is NOT a terribly important spec for a bass amp, so when shopping for a bass amp, don't bother with this number. Dedicated bass amps, BTW, usually offer awful SNR numbers.

3. Efficiency. Here's where you will be able to tell a decent manufacturer from the crap. Let's say you are looking at an 250 watt (RMS) amplifier. The first physical thing I look at, is how big a fuse do they recommend (or what size fuse is in the end of the amp)? I know right now that 250 watts OUT will demand (and I use 50% efficiency to keep it simple) 500 watts in. 500 watts in, divided by the (car running) battery voltage (14.4v) is about 35A. If I look at the end of the amp, and see a 20A fuse, I'm walking away, as there is no way that amp can make 250 REAL watts, continuously. 14.4v times 20A, equals 280 watts in. 250 watts out, divided by 280 watts in, translates to an 89% efficiency. In a class A/B amp, this is an impossible number, and it even stretches the imagination for digital amps, as well. The theoretical MAXIMUM efficiency for class A/B is 66%, (95% for digital) so someone is lying. I don't care WHO the manufacturer is, if these numbers don't add up, I will start looking elsewhere... Now, if all the other specification look good, AND I can get in the vicinity of the RMS power I am looking for, I will buy an amp that's efficiency number might be stretching the truth a bit.

4. Terminals. A frequently overlooked part of an amp, this is a very important part of an amp to me. A car is a place frought with vibrations. A cheap or cheezy feeling connector in power or speaker terminals and most ESPECIALLY in the RCA inputs, will often cause problems in the future. Setscrews for power, quality terminal blocks for speaker outputs, and Tiffany style RCA connections (the type attached to the chassis, rather than a block of plastic soldered to the PC board.) The quality of the I/Os can be a direct indicator of the attention to detail paid to the rest of the piece. Translation? Overall Quality.

5. Heat sink. This one is simple. How does it look? I eventually chose Eclipse gear, because it looked like jewelry. Fine finish and appearance. Also, heatsink size and quality can be another indicator of quality of the amplifier as whole. A heavy heatsink will also provide better thermal stability, a nice thing in an amp.

6. Damping Factor. I used to place more emphasis on this spec, but my research recently (over the last few years, really) has, while not proven to me it is a useless spec, has not proven to me it is an extremely important spec. This is why this particular spec is a little further down the list. While I place a bit more emphasis on it for a bass or mid-bass amp, I, admittedly, place less weight here than I used to...

7. Price. Money rarely means much to me in an amp, it's something I am going to be keeping for a long time usually, so I will save if necessary to get EXACTLY (or close to) what I am looking for.

These are the things I look for when trying to decide on an amp. OBVIOUSLY, there are going to be VERY few amps on the market that will make me happy across the board, but then some of the physical characteristics listed above can be made to fit me and my desires with a little time, a couple extra bux, and some careful use of a soldering iron. All of the above things will cost more, but it will ADD more to the finished product as well...

Reaper