Q: Hello, first let me say I really enjoy the magazine, and I look forward to each issue. I work at a high end install shop near the Los Angeles area. One of the things we always do when installing a high end system is to make sure the speakers have similar pathlengths to the listener, and we also pay close attention to getting the speaker cables exactly the same length for the left and right channels. This is done to prevent phase shift in the sound, and provide proper stereo imaging. We’ve noticed that this is a fairly uncommon practice, and a competitors shop says we’re wrong, and it won’t make any difference. This whole thing was my idea, and I’ve been doing it for years, and I don’t think I’m wrong. Can you set the record straight, and explain to him why phase is so important?
A: Okay, this is a case of good intentions, but misapplied physics. You are correct, phasing is important in the re-creation of a stereo image. If you add delay in one channel, it can result in pulling the center image to the opposite channel. This is why many people work so hard on getting the pathlengths from the left and right speakers to the listeners ears as equal as possible. Unfortunately, in 99% of vehicles there is always still some compromise, and we have to decide which seat position should get priority. That part of your process is on the right track. Now, getting back to your wiring method, I’m sorry to have to be the bearer of bad news, but your competitor is correct. You cannot significantly add delay to a speaker system by varying the length of the wire. The reason behind this is quite simple. Sound travels through air at approximately 1130 feet per second, which means that at 1kHz, speaker pathlength differences of about 1 foot can cause the sound to be almost completely out of phase with the other channel. On the other hand, the electrical signal from the amplifier travels through the cables at something a bit less than the speed of light. To put the speed differences between the two mediums in perspective, this means that if you wanted to shift a stereo image as much as moving the speaker 1 foot does, you’d need about 186,000 MILES of wire to achieve the same thing. So don’t worry about one set of cables being a few feet longer than the other, I promise no one will hear the difference. Thanks for writing.
Q: Hello. This might be a funny question for a magazine that is all about the aftermarket, but I want to buy a new car that has a great stereo system from the factory. I want excellent clarity, and very good staging and imaging. I also want it to have enough bass to be able to really boom when I cruise. I don’t want to cut up my new car with a bunch of aftermarket stuff, and have the warranty possibly become void. I also don’t know how to begin to choose from all the brands and models, so I am hoping to take the easy way out. Can you tell me who has the best factory OEM sound systems for what I want?
Cashman - via E-mail
A: Hey Cashman, the short answer to your question is… nobody! I’ve heard the best of these systems, and not one of them will do everything you are really looking for. While some of the systems in very high-end luxury cars are indeed getting better, they are still a long way from being competitive with good aftermarket gear, and that’s the simple truth. Excellent clarity can be had in the best of these systems, in cars typically costing upwards of $50K. You want good staging and imaging, but that is achieved through speaker placement, and no one is building cars with that goal in mind. And then you want some bump in the trunk, and very few OEM systems have any decent bass at all, and certainly not enough to roll the windows down and impress the ladies.
My advice to you, is to find a reputable, knowledgeable dealer, and explain what you want, and how you want to perform and look. Getting great sound isn’t all that complicated once you know the end goal, and have a budget. The cars warranty will not be voided by the installation of an aftermarket system, if it’s done properly by professionals. Before spending any money, ask to see similar cars they have done, or systems with similar design goals. Check out their work, and talk to the people who spent their money already. Then pick a good shop, and have fun designing your system with them. Thanks for reading and writing, and don’t rely on the OEM system for your tunes! Life’s too short!
Q: Dear Sir, I’m troubled by what appears to be a common problem in amplifier power ratings. I have an amplifier that is supposed to have 100 watts of power into 4 ohms. But then it also says that it has 180 watts of power into 2 ohms. I did the math, and one of these numbers has to be wrong. If it does 100 watts into 4 ohms, it should do 200 watts into 2 ohms, if my math is correct. Or if the 180 watts into 2 ohms is right, then isn’t the 4 ohm power only 90 watts? I’ve seen a lot of amps rated like this, and it’s really confusing! What gives?
Confused, Captain Calculator - via E-mail
A: Hello Confused, or is that Captain Confused? There is nothing wrong with your math, and there is actually nothing wrong with those specs either. The part you’re missing in the equation is the amplifiers output voltage drops at lower impedances, which is caused by an imperfect amplifier power supply, and inevitable internal losses. A theoretically perfect amplifier would follow your math exactly, but alas, that amp doesn’t exist. All electronics have some losses, and we have to deal with them until a room temperature superconducting material is developed.
What happens, is that when the amp is driving the 2 ohm load, the current requirements basically double in comparison to the 4 ohm load. This additional current makes the power supply work harder, the cars electrical system work harder, in fact every component from the alternator to the speakers has to work harder. Losses occur, and the result is a lower output voltage at the amplifier, which results in a bit lower output than the math would indicate. This is normal, and happens on all kinds of amplifiers, all the time. So don’t worry, the specs are real, and probably pretty accurate.