Date: 11 Jul 1998 22:22:31 GMT
From: rta4saabnopsamcom (RTA4SAAB)
Subject: Re: '93 9000 Stereo - no low end? Think again.

>Bass is not directional:that's why sub woofers work well at home or in >a car.You can put the sub anywhere and it'll sound great.All the >directional information is carried in the high frequencies My point is-depending on the crossover point and slope, not to mention harmonics, we CAN locate the point of origination. Most installers use 12db slopes at approximately 70-90hz as a low pass filter. This is great for Rock, Pop and Rap, but is not adequate for jazz or classical. Our ears are fairly sensitive to frequencies above 60hz and can locate those frequencies fairly well. A 70hz note decaying on a 12 db slope gives a sonic cue at 100hz at only 6db down. Now if this note originates from the back of the vehicle without proper time alignment, we will hear it from the back of the vehicle! Also, we have to take into account the transfer function of the particular vehicle. This can add to the lower and/or upper harmonics of the sub system, again allowing us to locate the source point. One needs to carefully design the enclosure, as well as select the proper X-over point and slope to have the sub blend seamlessly with the satellites. This is much easier to accomplish in the home as compared to an automotive environment. I have judged many cars on the IASCA circuit and have found only a handful that 1. Accurately reproduced the lower frequencies 2. Blended with the front stage 3. and sounded as if the pipe organs and the upright bass staged properly, that is, front and forward. These vehicles all had rear mounted subs crossed over on a 24db slope at or below 50hz (at least). Needless to say, their midbass drivers up-front were able to handle 40-50hz tones. Most 6"s cannot. Now, these are high end system with carefully planned and well executed installs, which most of us do not have the time nor resources for. Again, taken into consideration that most of the population thinks that 60hz is "sub", they probably could care less if the bass is coming from behind them. As an audiophile, I need the soundstage to be accurate. I do not enjoy listening to an automotive system with that kind of bass eminating from the rear of the car. But, then again, I am particlar about that kind of thing. Now, on to my car. I have a single 10" sub (PPI flat piston) in a 1ft3 sealed enclosure that will reproduce a 16hz organ tone-though barely. It is crossed over at 50Hz on an 18db slope with the polarity reversed for transfer function correction. It is located in the rear-and I can occasionally locate the source, depending on the music-but most of the time it is front and forward. It is complemented by a pair of 8" midbass drivers in the front band-passed from 40hz to 80hz on an 18db slope. The rest of the system is balanced out by a pair of Dynaudio System220MKII 2-way drivers crossed over at 75hz, again on an 18db slope. MUSIC MATTERS Real Time Audio

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