Return-Path: Received: from CMU-CS-ZOG.ARPA by CMU-CS-A.ARPA; 17 Sep 84 14:08:11 EDT Date: 17 Sep 1984 13:52-EDT From: Nathaniel.Borenstein@CMU-CS-ZOG.ARPA Subject: Car stereos To: Bovik@a, Nason@c Message-Id: <464291552/nsb@CMU-CS-ZOG> Here are the responses to my bboard post seeking advice on car stereos: Received: from CMU-CS-G.ARPA by CMU-CS-ZOG.ARPA; 12 Sep 84 21:58:01 EDT Date: 12 Sep 1984 21:59-EST From: Ivor.Durham@CMU-CS-G.ARPA Subject: Re: Car stereo advice? To: Nathaniel.Borenstein at CMU-CS-ZOG Message-Id: <463888787/id@CMU-CS-G> In-Reply-To: Nathaniel.Borenstein at CMU-CS-ZOG's bboard message of 12-Sep-84 19:19 I have a couple of articles in automotive magazines that might tell you something. I'll make you copies of the articles. There's also a pointer in one of the articles in the November '83 Car and Driver: ``"C/D Stereo Fitness Program," a low-cost, one-step hop-up for your tired original-equipment car stereo.'' I don't have that issue, but the Carnegie Library might. Ivor Received: from CMU-CS-A.ARPA by CMU-CS-ZOG.ARPA; 13 Sep 84 09:04:05 EDT Date: 13 Sep 84 08:56:43 EDT From: Bob Colwell@CMU-CS-A Subject: Re: Car stereo advice? To: Nathaniel.Borenstein at CMU-CS-ZOG You didn't mention whether or not you also want a cassette deck, but I assume you do, since I think they are invaluable on long trips (and when you get good and sick of the lousy FM programming available in many places). If so, I have had good results from my Pioneer deck -- their "supertuners" work very well. The cassette portion was initially very unreliable. Apparently Pioneer sent out a whole batch with a common manufacturing defect, since I traded the deck in three times (the cassette would sound awful due to poor tape speed regulation, then the deck would begin munching the tape). I eventually took the deck apart and found that the centrifugal governor contacts were never properly cleaned and weren't doing their thing. Of late I have grown enamored of the auto reverse feature in the deck that came in my Jeep. That is a really good feature to have in a auto stereo, since the driver never has to try to read the tape to see which way to put it in, and it doesn't have to be ejected in order to play the other side. The tuner is not as good, though, which leads me to another point. The antennae that are inside the front windshield aren't worth crap. I mounted a standard whip antenna on the fender and improved the FM reception quite a bit. (There is an "antenna match" adjustment inside FM stereo radios, often accessible by removing the tuning knobs and using a small screwdriver, which can have a large impact on reception too). Another feature to be careful of is a "DX/Local" switch. In my opinion, Pioneer blew it on that one. What happens is this: the tuner automatically switches between stereo and mono reception depending on the signal strength. (Stereo is noisier and requires a better signal). In a city like Pittsburgh, where hills and valleys abound, that signal strength can vary quite a bit. This makes the tuner switch back and forth a lot. Stereo/Mono is not so bad in itself, but the frequency response is also automatically adjusted on the principle that noise is worst in the high end, so highs are cut way back in mono. It really sounds like the drums' cymbals are turning off and on. Very Disconcerting and unpleasant. Pioneer should have traded that useless DX/Local switch for a Stereo/Mono switch and done away with that freq response adjustment. A final note: a friend in Portland Oregon tried to forestall any possible problems by buying the best. He spent several hundred dollars buying a Sony deck that has more computing power than the VAX. The result? Tuner works like a champ; deck has some kind of peculiar affinity for the transmission rumbles of his Porsche and often makes the cassette warble in a truly creative manner. I guess they're right: money can't buy happiness. Bob Received: from CMU-RI-ISL2.ARPA by CMU-CS-ZOG.ARPA; 13 Sep 84 09:56:59 EDT Date: 13 Sep 1984 09:53-EST From: Ingemar.Hulthage@CMU-RI-ISL2.ARPA Subject: Re: Car stereo advice? To: Nathaniel.Borenstein at CMU-CS-ZOG Message-Id: <463931624/iaeh@CMU-RI-ISL2> In-Reply-To: Nathaniel.Borenstein at CMU-CS-ZOG's bboard message of 12-Sep-84 19:23 I don't know much about car stereos myself, I am just starting to look into the matter. I know however from researching regular recievers that the sensitivity can be defined and is specified for good recievers and I know from experience that it makes a difference. THe sensitivity is even more important for a car reciever. The antenna also matters, the regular antennas gives a better signal than those fused into the windshield. Speaking of Bovik is there a convinient way to read bovik if you don't have an account on A. Received: from CMU-CS-GANDALF.ARPA by CMU-CS-ZOG.ARPA; 13 Sep 84 10:01:17 EDT Date: Thursday, 13 September 1984 09:47:17 EDT From: Charles.Krueger@cmu-cs-gandalf.arpa To: borenstein@cmu-cs-zog.arpa Subject: car stereo Message-ID: <1984.9.13.13.30.38.Charles.Krueger@cmu-cs-gandalf.arpa> I owned an audio electronics repair business that ran in conjunction with a stereo shop for 4 years before coming to CMU. After a while it was obvious which brands were good and which ones were junk. As far as I am concerned Alpine is the only brand worth paying money for. Many of the other decent brands, such as Jensen, are made by Alpine but are quite as good as the products that are sold as Alpine. Brands such as Sanyo, Craig, Kraco, MetroSound and Pioneer are really trash and are likely to cause you troubles. Concord is not bad. If you have any questions about specific brands I will be glad to offer my opinion. If you have the money to burn my suggestion would be to get a tuner/tapedeck, seperate graphic equalizer, seperate power amp with 25-40 watts power per channel. 4 speakers offer far superior sound over 2. The two speaker in the back of the car should be able to handle bass (6 inch round or 6x9). The two speakers in the front of the car are not as crucial. Co-axial speakers are OK if designed properly, but tri-axials are in general stinky-poo. Charlie Received: from CMU-CS-G.ARPA by CMU-CS-ZOG.ARPA; 13 Sep 84 10:26:30 EDT Date: 13 Sep 1984 10:21-EST From: Joshua.Bloch@CMU-CS-G.ARPA Subject: Re: Car stereo advice? To: Nathaniel.Borenstein at CMU-CS-ZOG Message-Id: <463933296/jjb@CMU-CS-G> In-Reply-To: Nathaniel.Borenstein at CMU-CS-ZOG's bboard message of 12-Sep-84 19:19 I own an Alpine and I like it. Other good brands are Concord, Blaupunkt and Kenwood. Speakers are somewhat trickier. Don't make the same mistake I did and get suckered into buying a mediocre pair. (Clarion) Sony makes very good, reasonably priced speakers. If you want to spend a bit more, I hear that Boston Acoustics is the brand to look at these days. It can be hard to fit some speakers into little hatchbacks, and that might limit your choices. Although CR hasn't published any ratings recently, various audio enthusiast publications have. I remeber reading one last summer. Josh Received: from CMU-CS-IUS2.ARPA by CMU-CS-ZOG.ARPA; 13 Sep 84 10:51:08 EDT Date: 13 Sep 1984 10:56-EST From: Leonard.Hamey@CMU-CS-IUS2.ARPA Subject: Re: Car stereo advice? To: Nathaniel.Borenstein at CMU-CS-ZOG Message-Id: <463935368/lgh@CMU-CS-IUS2> In-Reply-To: Nathaniel.Borenstein at CMU-CS-ZOG's bboard message of 12-Sep-84 19:28 I'm very happy with our Kraco. It's not an expensive model by any means, but has 7 watts max per channel which is more than enough to beat road noise. I find the digital tuning very handy - seek and scan make it easy to find a station when travelling. The FM reception seems to pretty good - we were picking up a station in Lynchburg when we were 40 miles away. It has DX/LO switch which improves reception of distant stations. If you don't want to spend a lot, the David Weiss catalog has a good selection of Kracos at very competitive prices. Leonard Hamey Received: from CMU-CS-A.ARPA by CMU-CS-ZOG.ARPA; 13 Sep 84 12:08:49 EDT Date: 13 Sep 84 11:54:40 EDT From: Craig Everhart@CMU-CS-A Subject: Car stereo, camera To: Nathaniel.Borenstein at CMU-CS-ZOG I have a Polaroid at home, bought for our son's surprise appearance. I will try to bring it in tomorrow (Friday) unless you tell me otherwise. You might try High Fidelity or Stereo Review; they have reviewed some car stereos recently. A decent library will have the relevant back copies (within the last year). I trust you have some of the basic concepts. The FM receiver of course has several metrics/design choices. One thing it has to do is generate the broadcast frequency. Most models generate the frequency in an analog fashion; you turn the knob to vary the frequency; it's continuously variable, and you have to match frequencies yourself, by ear. AFC helps here, but you have to get it started with a good frequency match. Some models generate the frequency using crystal-controlled oscillators; they generate only the proper multiples of the relevant base frequency (e.g. 200KHz). The analog tuners will usually have an analog dial and the digital tuners a digital dial, but some analog tuners have a digital dial, presumably to look like they're digital tuners (which are much more accurate). Some home-use digital tuners have a numeric keypad on which you enter your frequency, but most car digital tuners have a scanner and simple increment/decrement frequency controls. Of course, getting the base frequency right is only part of the job. The next job is to filter out the adjacent channels; this is the ``XX rejection'' specification, measured in how many dBs down the adjacent frequency channel is. Extracting the stereo signal is the next part. Problem is that the stereo signal (the left minus the right channel) is inherently noisier than the basic mono signal (left plus right); as the signal strength goes down, the difference signal gets noisier much sooner than the sum signal. Many tuners have a method for compensating for this--they fade out the difference signal (making the reproduction more mono) as its strength goes down. You can see this in action in a graph of stereo separation w.r.t. signal strength. Of course, there's also the base sensitivity rating, usually given in radio frequency power (from the radio transmitter) necessary to achieve a given signal-to-noise ratio. This applies only to receiving a mono signal. There's a great hack that Sony has in one or two of their better car units-- the facility to have an extra FM antenna mounted on your car. The idea is that as you drive, especially through the city, you pass through regions of strong and weak signal very rapidly, like every three feet. It's just a radio signal interfering with its own reflection off buildings and things, but it's still annoying. The idea is that you mount two antennas on your car, separated by several feet, and connect them both to the Sony unit. It samples them both continuously, and switches to the one with the stronger signal on the frequency to which you're tuned. Works like a charm, according to the review I saw (in one of the magazines I mentioned). And, a basic issue in quality of car stereo sound is the quality of the installation. I have a great radio/tape player (a Doug Jensen resale item), but its sound is often noisy. I attribute this to a bad installation; the guy doing the job picked a very noisy source for the unit power. (Particularly since the noise comes and goes.) I will one of these days have to go in and try to fix this, but you know where all the spare time goes. There are acoustic installation issues also, but those have much more to do with speaker installation than electronics. Best of luck. Hope you find the product reviews, and that you find them useful. Craig