Sony sound processing....

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I finally got the brakes done on my 63 falcon. Yea!!

:D


So I was at walmart the other day and could not pass up a $60 deal on a sony head unit with 4 speakers. I spent a day custom fabing a new glovebox ( the old one was cardboard anyways :xeye: ) out of wood, complete with space for my head unit as well as a little storage. I figured for $60, I could at least learn how to properly wire a head unit.

I went through my electrical system very carefully before deciding where to add wiring, and nothing was spliced in. Im fortunate enough to own one where someone has not botched the wiring in this car, its all completly original. I ran a 12g wire from the ignition accessory line to the head's acc, and a 10g wire from my battery term to the amps main. I figured 10g was enough for my head since real power output is about 18wpch rms, so the cable should be fine. Everything was done cleanly using wire crimps and cable connects. I only had to run two wires, which I did right and then used sheathing to clean it all up ( even did some of the stock wiring under the hood to clean it up!


The kit came with some pretty good 6x9's and some 6" as well. I will not mount the 6 inchers yet, as I am NOT going to install them in the doors, and I need to fabricate something for them to go in the kick panels. I'm honestly thinking about going with 3" or 4" in the k/p's anyways.



So, I had some cheap duraband's in the rear before, powered by a 15 watt/channel RMS car amplifier that I built using a TDA72xx chip ( I have to look it up again!)

Aside from only having whizzer cones for high and mid, they sounded downright impressive! Without fabric covering them they were fine, but with fabric over them the whizzer cones just didnt do a good enough job and it sounded muddy. The speakers are around 91db efficient, so their not too bad. The bass out of them was incredible though, with my cars good sized trunk and cabin. With some good 6x9's and a good amp, who honestly needs a subwoofer?


Anyways, when I bought the sony head unit, I was expecing the slightly better power output ( ~20wpch to my 15 wpch, I looked up the chip it uses, which is made by philips.)

Well I have everything professionaly wired now and it looks very good, with the stereo in the glove box no one will be tempted to break into the car ( car has a radio delete plate in the stock radio place)

Heres my main problem:

Sony's sound processing!! The unit sounds ok I guess, but seriously lacks low end bass, and seems to exaggerate the bass around 60-70 hz so it sounds boomy, no matter what eq setting you use. It has adjustable low, mid, and high, but the only eq adjustment thats worth anything is the high!

I'm beginning to suspect sony cuts off the bass at a certain point to make you think you need to go out and buy a sony subwoofer....

My amp built has better definition also, the bass is a whole lot better, even with the durabands.

The sony has a selectable subwoofer output at 78hz or 125hz for x-over frequencies. I decided to try somthing. Since my car originally had a single 6x9 in the center of the package tray, why not use one of my durabands in the middle, and hook it up to one channel of my amp, and that in turn to the sony's subwoofer output?

So I do this, and set the sub level to about 7, and crossover @ 78hz. I used the aux in, since the cd player on this unit just isn't great at all, and I mainly use my mp3 player, which sounds a whole lot better. The sound? Incredible! one 6x9 as a subwoofer, powered by a 15 watt amp!

But.......

I still had about the same amount of bass I had before with my two channel amp and the durabands, except for the extra midbass punch from the xpolods ( which is a nice addition.)


So my question is: is Sony actually doing this on purpose? and are there any head units that put out true fullrange sound without modifications to the EQing? I even tried using the aux outputs on it, and they still did the same thing, even with my amp that I built, showing that it is all in the sony's sound processing section. I have not tried unsoldering the input capacitors and running my mp3 player directly to the sony's amplifier yet.

Any ideas? :xeye:

Also, if I can't fix this problem I have a few other routes I can go. I am getting the car professionally restored in the spring/summer months, so I will probably get another head unit and some better speakers then.

I have 5 openings in the package tray. The two larger square ones I have 1"wood adaptor boards mounted in for the 6x9's, and they fit perfectly. The two square ones on the outside might be able to fit a 6x9 ~ at an angle, but would probably be better suited for 6"s. Heres my I idea: Useing a low pass filter on my amplifier, I could use either the sony 6x9's or the durabands run in paralell for 2 ohms. My amplifier is capable of about 27 watts RMS before clipping into 2 ohms, which would probably be more than enough. I could set them up as 'subs' and maybe put the 6"s in the outer holes?
 
Another question: with two 6x9's run in paralell ( 2 ohms)

would it be the same as running two 4 ohm amps @ 15 watts rms, or one 2 ohm amp at 30 watts rms?

I mean, would their be any real difference? I was thinking about using the tda7396 or 7391 amplifier for this purpose. The tda7396 will do about 35 watts RMS into 2 ohms @ 1% THD. It does around 20 watts RMS @ .06% THD. Since this would be for a subwoofer aplication, I would not notice the distortion as much correct? Most of these chips have their distortion in the second and third harmonic areas, so the distortion goes up with frequency. How much distortion can you get away with in a subwoofer before it becomes noticable?

I know I'm squeezing watts here, as it only translates into 1 or 2 db difference in overall sound, but the bass will hit harder without as much distortion with a few extra watts to spare before clipping.
 
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