Be Careful Who You Listen To
There seems to be a never ending stream of advice when it comes to car audio. Some of it is good but much of it is bad. Some of it is very bad. The real problem is those that need good information the most have the hardest time determining what is bad information. I've picked out some of what I believe to be the most common sources of bad information.

Car Audio Salesmen
The job of a car audio salesman is to get you to buy what the shop has to sell. And the more you buy the more money the salesman and the shop will make. On the other hand you want to spend as little as you can while still getting what you want. So right away you and the shop want different things. Some shops are very good at helping customers get what they want and value a long term relationship and referrals. Others just want to maximize that days profit. Clearly you want the first type. If you have friends that can recommend a shop like this that's a good way to find them. If you have the time you can also visit several shops to get a feel for the type of business they are. You should know within the first couple of minutes of talking to them if they want to help you or help themselves. Beware of statements like:

"A pair of these tens will hit harder than two fifteens." - Who's fifteens? What kind of boxes? With the same amount of power? That's a lot of surface area difference so how is it that these woofers will provide so much more output? There are a lot of factors in a subwoofer system and blanket statements like that need to be backed up or ignored.

"This is the best amp out there." - Based on what criteria? Is it the best in terms of price, sound quality, efficiency, cosmetics or is it just the best in terms of profit margin and commission? If the salesman doesn't know what's important to you then he's not going to be able to tell you what the best anything is for YOU.
"These speakers sound better than anything else you can buy." - Says who? Maybe they sound terrible to you or maybe they're out of your price range. Do they even fit your vehicle? Did the salesman even ask what you drive and then find out what fits?

Not all salesmen are bad of course and there are some that are genuinely great. But you need to watch out for the ones that only want to separate you from your money and talk more than they listen.
Companies
Car audio companies are no different than any other company whether they sell kitchen mixers or sports cars. They all claim that they make the best widget. But just like anything if the one making the "best widget" statement doesn't know what is important to you it really doesn't mean anything. The "most legroom" probably doesn't matter to you if you're 4'11" but if you have seven kids "most passenger room" would.

Often it seems that the people in charge of writing the car audio ad have no idea what they're dealing with. They get a spec sheet from the engineers and then transform that into an ad that is virtually meaningless to a consumer. What is a triple darlington output and why do I care if your amp has it? I've seen that listed over and over again as a feature but I have yet to see any company explain what it is and why you would want it (in an ad anyway). My favorite are the startup companies that place a full page ad in a car audio magazine claiming to be the best thing out there. Nothing to back it up. Just a few pictures of their product line over a cheesy background and it's clear the products are the same thing every other new company comes out with. Mostly the same Chinese made equipment that anyone can order with their logo on it.

Anyone can claim to have the best whatever. But find out if they back it up. How long is the warranty? What if you install it yourself? Does their web site have manuals, diagrams and other technical help on it? Do they even have a website? How long have they been in business? Are they going to be around in a year? These are all questions that you need to find out before purchasing this "best equipment". The best way to back up these claims is to put the old money where the mouth is. Several years back there was a company that offered you a thirty day satisfaction guarantee on their subwoofers. If you bought it and didn't like it then you could return it for a full refund (minus shipping costs I'm sure). Their subwoofers were excellent and their guarantee showed they meant it. FYI - that company was Audiomobile and their subwoofers were made by TC Sounds which I've written about in this article.

Forums
In my opinion the worst offender of bad advice comes from forums. On a forum you have no idea who people are, their background or what qualifies them to give any kind of advice. The number of stars by their name doesn't mean they know what they're talking about. It only means that they like to talk. They might throw their two cents in even when they're totally clueless on the subject. I'm sure you know people in real life that are just like that. Well those people have computers and an Internet connection too.

Always keep in mind that you almost never know who the person is behind the forum name. There are very few true experts on most forums. Mainly because they don't have time to fight with every know-it-all that chimes in with "the answer". There are plenty of posts that say things like "XYZ sucks. My friend built a box for two of their subs and it sounded terrible". Well, maybe your friend is an idiot. Did he build the box to the right size? Did he even know what size to build it? Did he brace and seal it properly? What kind of material did he use and how thick was it? No one tells you those details. They just say don't buy it and move on to crap on another post.

One of my favorites that I see come up again and again deals with fiberglass layers. It usually starts with someone asking "How thick should my fiberglass box be?". That usually follows with someone saying it should be 3/4" thick. Why did they say it should be that thick? Because somewhere along the line they were told that subwoofer boxes should be 3/4" thick. Well, that may be somewhat true if the enclosure is large and made out of MDF but it has nothing to do with fiberglass since they're two very different materials. And even with MDF that's just a guideline that varies with many other factors. Then someone else will come in and say it should be seven layers or twelve layers or whatever they used the one time they made a fiberglass box. That information probably has nothing to do with the project being discussed. The number of layers or thickness of a fiberglass enclosure depends on many things and answering the question without knowing these factors is a the same as guessing. FYI - I've written an article that discusses how thick a fiberglass enclosure should be if you're interested in that topic.

My other favorite is whether a subwoofer box with multiple woofers needs to be divided. There are guys who are absolutely convinced that a subwoofer box needs to be divided if there is more than one woofer in it. Others are convinced of just the opposite. So who do you listen to if you don't know the answer? The one who posts the most or the one who YELLS the most? If there are four answers and only one is right how would you know? What if they're all wrong? That's the problem with forums. You don't know who is right, who is wrong or even who anyone is. You get the most "rank" in a forum by posting the most responses and not for posting the most accurate responses. Keep that in mind when you feel compelled to believe someone simply because they have a bunch of stars under their made up forum name. If a member answers your question ask them to say why they think what they wrote. Hopefully there is some real information behind it and not just because "I heard it on another forum" or "some guy at a shop told me that".

For any source of information ask yourself what the person has to lose if they lie or are wrong. If the answer is nothing or very little then they may not be putting much effort or truth into the advice they're giving you. I think next time I'll answer the question about multiple woofers and whether they need to be divided in a shared enclosure. And I promise I'll back it up with real information.