Read about troubleshooting car audio problems.
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Q: I've been tinkering with different sub box designs for my '99 S-10 extended cab and haven't been able to make anything that was original enough and to my liking. I'm currently using two Audiomobile EVO 10's powered by a Planet Audio 2,500-watt Class D amp and was figuring on an internal volume of 0.73ft3. My big question is, would it be feasible to use a folded horn design ( la Cerwin Vega, Earthquake)? And how would that change the dimensions? I know I'm probably being pretty vague here, but any help would be appreciated.Thanks,Jason Raymond
A: I'd put this pretty low on the feasibility chart. Even if you had a full-size land yacht, there would not be enough trunk space to create a true tractrix-style horn. The actual cabinet that the speaker occupies will be fairly small, but the whole story to a horn design is based on everything in front of the speaker. Generally, the output of the horn will be related to the bass frequency range you want to reproduce, so numbers like 15' and larger start to enter the discussion. And since the length of the horn is proportional to the exit, it may be twice as long as it is wide.
That's for a true horn, but almost every speaker-based horn used in home audio is some partial design that uses the environment to finish the job. For instance, a "corner horn" manufactured by a few companies is meant to be placed in the corner of the room, using the adjoining walls as the continuation of a half-finished horn design. That is not too likely to work in a car due to the widely varying shapes.
Let's step back for a minute and look at why you are hooked on building a horn. Horns are not really speaker enclosures, but are more of an acoustic loading system that factors in as the sound waves leave the front of the speaker element, whether it's for a tweeter, mid or bass driver. As sound radiates away from the speaker, it immediately tries to disperse in an omni-directional pattern. Bass is pretty much fully omni-directional, and as frequency rises, the propagation becomes more directional. This is why you can stand behind a woofer cabinet and still hear most of the bass, but for a tweeter, you need to be close to directly in front of the speaker.
If you cup your hands in front of your mouth as you speak, your hands form a cone that helps the sound to stay together longer. The value to this is that the sound will travel further and with more sound pressure than if your hands were not near your mouth. The tradeoff is that you need to face directly toward the person you are speaking to, or they hear a lot less than if you didn't use your hands. In essence, you are making omni-directional sound more directional by forming a bit of a horn with your hands. Roll up a sheet of stiff paper into a cone and you now have a primitive megaphone, which keeps the sound together even longer, allowing it to leave the horn and proceed without wanting to spread nearly as much.
For high frequencies, the horn is proportionally smaller than for bass frequencies. A true horn, known as a fog horn on the rocky coastlines of many countries, can be 30' wide and 50' long to ensure that the bass tones produced travel a long way out to approaching boats.
What are the give and take tradeoffs with horns? You get increased efficiency, since the majority of the sound is being directed to the target. You also get some measure of control over where sound goes. You give up compact size, easy construction and sound quality. Horns are notoriously harsh to listen to unless they are carefully tuned, as a few minutes in front of the speaker stack at a concert will confirm.
With an S-10 pickup, I would be shooting for the most reasonably compact sealed cabinet I could manage.
Q: First, I'd like to say that I thoroughly enjoy your mag. The feature vehicles as well as the articles leave me always awaiting the next issue for MORE! I have a simple question: Someone out there must have measured the air volume of a 1998 Civic Hatchback's spare tire well. Assuming that I do not build any additional walls to raise the baffle from the car floor and I were to fiberglass the spare tire well, what would be the internal volume. I know of one trick which would involve filling the well with water to see how many liters would fit, but, hey, I'm sure someone must have done this already - why re-invent the wheel? Is there any reference that I can access for this type of information?Thanks,LoneRiderMontreal, Canada
A: You can bet that someone has measured the spare tire well volume of a popular car like a Civic, but since it is done so infrequently, nobody ever bothers to document it. And, since fiberglass spare tire wells are not an everyday installation project and, as far as I know, there is no database of recorded volumes that you can access, do what I do: Just pull out the water and a measuring container and start dumping in measured amounts. It takes 28.32 liters or 7.5 U.S. gallons to make a cubic foot of volume.
If you don't like the wet method, you can do the same thing using sandbox sand, and when you are finished, you simply vacuum out the spare tire well using a shop vac. Another possibility is to use unpopped popcorn kernels, since you can make them serve double duty as a snack after you finish the measurement. I have learned it's better to pop them before consuming...
Q: Hi, my friend and I are both really getting into car audio. We are constantly buying and installing new gear. The actual question I have for you is about RCA cable sound quality. We are in Maine and things are rough as far as professional installers and people who actually know what they are talking about, but how much of a difference does RCA cable quality make? Right now I have just regular old RCA that is probably 12-gauge single-coated wire. Would it really be worth spending $50 plus for better RCA wire or is what I have sufficient? Any help would be appreciated, thanks.JR Henderson
A: Welcome to the lunatic fringe and the many extreme debates about things like wiring in an audio system, but you can always count on basic logic to make the road to a decision a bit less rocky. As an analogy, think about the fuel system of your car - would it make sense to have an undersized or poor-quality fuel line between the gas tank and the engine? It might appear to work fine, but you won't know if there is a better result waiting for you.
Yes, I believe quality wire is important, but not the number one priority of the installation. As long as the wiring you select for both signal and power are appropriate for the gear it is connecting to, you should be happy. Ultra chic wire on a budget stereo system makes equal sense to a cheap hunk of wire on a premium audio system. Just look for the balance and you can feel good about the results.
I question what you describe as your regular old 12-gauge wire - there is no such thing as a consumer or professional 12-gauge audio signal wire of any type. The gauge measurement of a wire only considers the conductor, not the insulator. If you strip off the outer jacket, shielding and inner insulation, you will find that your RCA cable is really no bigger than a 20-gauge. If it is your standard, inexpensive RCA cable and you have budget car audio gear, then you are likely fine. Always design for the best component you have, so that you are always building and upgrading to a system with no limitations.