zahid@neptune.AMD.COM (Zahid Ahsanullah) (03/21/90)
Hi all, seems like I sent this off to the wrong person the first time. Hope this is the right address for rec.audio.high-end. -------------------------------------------------------------------- I have never heard a car stereo that I have liked. I'm not talking about Sony'ish or Alpine'ish stuff. I'm referring to stuff that costs thousands of dollars. My friend installed a $3000 system in his car recently that he is very proud of and invited me to listen to it. I was impressed, but not with the quality of the sound but the sheer sonic power. You could hear the boooooms and tisshhhh's for literally blocks but nothing of the midrange. There was nothing you could do to the equalizer to bring it out. The story is the same for a lot of other `expensive' sound systems I have heard. Maybe I am too critical but surely for thousands of dollars you should get a quality home stereo sound. Here is why I think that car stereo will never sound like a home stereo. Take for example speakers. A home stereo speaker is 8 Ohms, with light cone and flexible spider spring. A spider spring is what keeps the voice coil suspended over the magnet. It also has a light cone spring at the ends of the cone where it attaches the frame. The reason for this setup is because the speaker remains vertical for life. If you lay a home speaker down on its back or face for a long period of time the weight of the cone will make the spider spring stretch and make the voice coil sit at a position away from the optimal position. The optimal position for a voice coil to sit on a magnet is the top of the voice coil should be be flush with the top of the magnet. Any change from this position will result in loss of sound quality as happens with most old or fairly used speakers. A car speaker is designed to lie in its back and face outdoor abuse. For this reason the paper is thick, the spider is stiff so it'll hold the voice coil in place for a long time. The outer cone attachment is rugged and thick to support the cone and not let the spider do all the work. What all this does is that cone has terrible mid freq response and colored low response due to the paper not being allowed to move freely. The only way to make it move is by sheer wattage and since the travel is still limited and the mass considerable, the bass is colored due to cone momentum. Also 4 Ohms don't have much midrange response anyway. The tape deck is next being powered only by 12 volts. I have designed enough amplifiers to know that 12 volts aint never gonna cut it as far as frequency response is concerned. You need atleats 20 volts to get anything decent out of a preamp. Something about Bipolar transistors that it wants more than 12 volts. Maybe I'll analyze this problem if I ever get time to myself. I have tried subsituting top of the line tape decks of a couple high end systems in expensive car stereos but they all sound about the same. You are better off buying a slightly above average Sony or Alpine to get in the ballpark. That $500 difference is just too slight to notice. Finally the amplifier. Most amps are powered by 12 volts and thus the output stage can only handle a 4 Ohm load effectively. Some amps I think have invertors that raise the voltage to maybe 25 volts (some of you might know this better). But they still have the output stage designed to drive a four ohm load. All this does is that it concentrates the power on the lower end of the spectrum and distorts the high end so that it sounds pronounced. You can amplify a colored signal but all it'll do is make it loud with no image. If the signal has a small distortion in it it'll hurt the ears. Thus the boomy sound and abnormal sounding highs. To get the midrange out you need more voltage and the ideal power output design is a complementary output powered by a split supply of atleast 30-0-30 volts. A single supply like 0-25 has a simpler circuit and not a very good response. This is what I suspect is done for most car amps today. I may be wrong though. These people may claim that response is 20 to 20Khz at 0db but they are not telling the whole story. Did they test the output at one ohm and 150 ohms to see what it's like? not likely. The impedance seen by the output is not really 4ohm or 8ohm it is at least this much depending on the frequency. To make a long story short, to get a good quality sound in a car you need a home stereo system in the car. Several years ago my younger brother and myself did exactly this in our car. We designed a 30-0-30v invertor for a car battery and powered a STK022 based power amp of our own design. STK022,032,042...... are a series of thick film amps that are widely used in output stages of modern amplifiers. The '022 does something like 30 watts rms into 8 Ohms. Being limited by budget we couldn't buy an expensive tape player so we modified a generic panasonic for our needs. First thing we did was isolate the preamp power supply leads (12v) by cutting out traces from the pcb and feeding it with our own supply of 16 volts. The next modification we did was to introduce a negative feedback right from the output to increase frequency response. The line outs were tapped directly from the circuit board and the power transistors were disabled to reduce useless power dissipation. Our amps input was perfectly matched with the line out of the tape deck. The speakers were the smallest Denon available that fit on the floor of the back seat. These were rated at 80 watts and were a two way system. The results were amazing, the quality was so good the people used to peek into our dash to see what stereo we were using. Needless to say they couldn't understand how a cheapo tape deck we were showing could perform so well. You could play the stereo as loud as possible and it wouldn't hurt the ear near as much as these boommmm tisshhh's systems do today. Some of these systems make my ears flutter but I see the owners sitting right pretty and proud of the abuse. If you stand outside the car, you can hardly hear the singers' voice. It's like listening to a stereo with midrange equalizer turned down low. Our system never had an equalizer since we couldn't afford one but there was no need. We did however incorporate a loudness switch that came out of our amp. If you stood outside the car a little distance from it you could swear that the music was coming from a high quality home stereo from one of the houses. The singers voice use to jump out loud and clear like I've never heard in any car stereo. Whether you played Alan Parsons Project or Deep Purple, the reproduction was flawless. There was some hiss from the tape deck due it not having a dolby and being kind of generic and the configuration aggravated by the incomparable frequency response of the amp to the deck (try hooking up a car cassette recorder to a home stereo). But it didn't bother us that bad. Also, batteries would run out after a year but there were ways around it. Is there any system like this available out there? How come some car systems cost tens of thousands? Has anyone heard them. Zahid
chowkwan@aero.org (Raymond Chowkwanyun) (03/22/90)
> zahid@neptune.AMD.COM (Zahid Ahsanullah) writes: >is colored due to cone momentum. Also 4 Ohms don't have much midrange >response anyway. Why does mid-range performance correlate with the impedance of the speaker? Don't some highly regarded home speakers such as electrostatics (martin logan) or ribbons (apogee) have very low impedances? Yet these are speakers reknowned for their midrange. > The tape deck is next being powered only by 12 volts. I have >designed enough amplifiers to know that 12 volts aint never gonna >cut it as far as frequency response is concerned. You need atleats 20 >volts to get anything decent out of a preamp. Something about Bipolar Your point about lack of volts is taken. Can this problem be gotten around by stepping up the voltage inside the amplifier? I've recently seen an ad for a tube amp for cars in TAS. I assume he has to step up the voltage to operate the tubes properly. >sheer sonic power. You could hear the boooooms and tisshhhh's for >literally blocks but nothing of the midrange. There was nothing you >could do to the equalizer to bring it out. The story is the same for >a lot of other `expensive' sound systems I have heard. Maybe I am too Flat frequency response is ideal. No-one is going to challenge that. However, there is compensation in being surrounded by four speakers that produce a 3 dimensional effect that I find enjoyable. For the record: I used to have an alpine/ads/infinity/generic speaker system in my car (before the accident which is another story). Your idea of putting a home system in a car is an intruiging one. I'd like to try it out (I have a spare NAD amp). Can you email me more details: like how did you get the amp to fit in your dash? Was it just because you made it yourself that you could get it small enough? -- ray
mwarren@mips2.cr.bull.com (Mark Warren) (03/22/90)
In article <9003210057.AA17666@neptune.AMD.COM> zahid@neptune.AMD.COM (Zahid Ahsanullah) writes: >Hi all, seems like I sent this off to the wrong person the >first time. Hope this is the right address for rec.audio.high-end. > >-------------------------------------------------------------------- You got rec.audio.high-end all right, but I don't think that is where this belongs. IMHO the aim of high-end audio (accurate reproduction of sound, especially music) and the acoustics inside an automobile are completely incompatible. I'm redirecting followups to rec.audio. [This is one of the tough decisions. It's up to the readers to decide if auto-sound is appropriate. - tjk] -- == Mark Warren Bull HN Information Systems Inc. == == (508) 671-3171 (FAX 671-3020) 300 Concord Road MS820A == == mwarren@granite.cr.bull.com Billerica, MA 01821 ==
jgro@apldbio.com (Jeremy Grodberg) (03/22/90)
In article <9003211837.AA02671@mips2.cr.bull.com> mwarren@mips2.cr.bull.com (Mark Warren) writes: >In article <9003210057.AA17666@neptune.AMD.COM> >zahid@neptune.AMD.COM (Zahid Ahsanullah) writes: >[...] >IMHO the aim of high-end audio (accurate reproduction of sound, >especially music) and the acoustics inside an automobile are completely >incompatible. [...] > >[This is one of the tough decisions. It's up to the readers to decide if >auto-sound is appropriate. - tjk] > IMHO the aim of rec.audio.high-end is to provide a forum for discussing equipment and techniques of audio reproduction for those who take their audio seriously. Such people often drive cars and listen to music at the same time, so I think discussion of auto-sound is quite appropriate, provided that the discussion is concerned with high-end auto-sound. It is quite challenging to provide high-quality sound in a car, but it is a challenge I'd bet most readers of this group have undertaken. You can vote for rec.cars.audio if you want to have some place to throw the radio shack crowd to, but where else can we discuss car CD players and changers? At $1000 or more, most people in rec.audio are not interested. ---- Jeremy Grodberg jgro@apldbio.com "Beware: free advice is often overpriced!"
mwarren@mips2.cr.bull.com (Mark Warren) (03/22/90)
In article <3011@uwm.edu> jgro@apldbio.com (Jeremy Grodberg) writes: > >IMHO the aim of rec.audio.high-end is to provide a forum for discussing >equipment and techniques of audio reproduction for those who take their >audio seriously. Such people often drive cars and listen to music at the >same time, so I think discussion of auto-sound is quite appropriate, provided >that the discussion is concerned with high-end auto-sound. [and so on...] As I re-read my posting about the inappropriateness of auto-audio to this group, I realize it was a bit more caustic than I had intended. However, I still maintain that with present technology, no matter how much money one invests in a car stereo system, the sound quality is simply not going to approach the typical equipment discussed in this group. [I agree; however, car audio is where a lot of audiophiles get started. The same rigorous techniques apply. Let's just say, if it's related to build-it-yourself, and the same information could apply to home audio, it's appropriate. OK? -tjk] I agree that there is certainly merit in trying to obtain the best possible sound in a car. Since there seems to be such a large market based on this thought, perhaps a rec.audio.auto is appropriate. Are there any rec.audio readers who can tell about how much of rec.audio is currently concerned with car stereo? -- == Mark Warren Bull HN Information Systems Inc. == == (508) 671-3171 (FAX 671-3020) 300 Concord Road MS820A == == mwarren@granite.cr.bull.com Billerica, MA 01821 ==