dian1511

I recently installed Polk DX6s into the front doors and they do sound better than the stock Bose speakers. However, as many of you know, the high end is cooked to the point of over brilliant cymbals, etc. Toning down the treble just does not get rid of it.

I believe that I have to install two more Polks in the back and then amplify these speakers and bypass the EQ, as has been discussed before.

I'd like to know from those of you who have kept the stock unit, bypassed the EQ, and used Line Out Converters to connect to amps: Have you been able to do this without introducing any new hiss or distortion into the system? From the threads I've read, it seems that folks have developed unwanted noise with usage of LOCs.

Can you bypass the EQ, keep the stock unit and use anything else besides LOCs that would not introduce unwanted noise into the system.

Any help would be appreciated.

miwa

sometimes.. extra hiss is due to the amplifier gains being set too high. a lot of people use the gains to make things louder (myself included in the past) when the gain should only be used for 'matching' the output of the source if you are attempting to build a system aimed at sound quality.

Southbound

I know what you mean about the over emphasized highs from the stock EQ.

I've got a spare pair of DX-6s and know that they would sound better than the BOSE in the rear, but I'm hesitant to do it without bypassing the EQ first. I have found that I have gotten used to them in the front and usually live with the treble centered most of the time now. OF COURSE I HAVE 50 YEAR OLD EARS that probably have dropped off some at the high end. I do still hear 15,750KHZ from screaming video monitors though.

Your key here is to not drop the level too far from the stock headunit before feeding the new amp. Try to keep things as close to unity gain as you can. If you dropped the stock head unit's signal down from say 2Volts to 200mV, then you have just dropped 20db. This means that you need 20db more gain out of the new amp just to get back up to where you were. You WON'T get 20db of gain for FREE... It will have some noise associated with it. Like I said, I'm not familiar with today's LOCs and current car audio amps. BUT if the LOCs have an attentuation range, then you would want to set them for minimum attenuation, and set the aftermarket amplifier voltage gain for minimum. That's the best you can do with regard to noise immunity. However, you may have to compromise. You want enough gain out of the final amp to drive it all the way to clipping with a variety of music just at the end of the volume control. You also don't want to have to drive the stock unit up to where its internal limiting circuit kicks in (and distorts) before you drive the aftermarket amp to full level. Idealy, you'd probably want to attentuate the stock unit by about 6db and then set the following amp gain to 6db plus whatever extra gain its capable of providing before it clips. 6db would be four times the power, so if the aftermarket final amp had a total gain of 12db, (6db to get back up to unity, plus 6db for the extra voltage swing that it can provide)it would be able to put out around 50wattsRMS. If you have a power amp capable of providing more than 50watts rms, then you would need to set its gain a bit higher.

Hope some of this jibber jabber makes sense.
Southbound

miwa

wow.. an actual frequency for that sound. it never occurred to me to look it up but its a nice 'marker' of how high my hearing still goes... thanks

Southbound

NOT TO BE A GEEK!!!! JUST BECAUSE YOU SEEMED INTERESTED... The horizontal sweep frequency of COLOR television is 15,734Khz.

The 15,750Khz was the old Black and White standard. I was just rounding things off. NOT that it matters. BUT, yeah it can be an indicator as to how high your hearing still works. Usually you can only hear this frequency by turning your head around in a specific direction. High frequencies are defitnitely very directional, and this pushes the limits of a lot of ears. Sometimes when you can really hear it loud, you are just hearing the laminations of the flyback transformer vibrating the frequency and producing a lower freq. beat. BUT when only you can hear it by turning your head in certain directions, and other older people can't... You're hearing the real oscillator. I used to be able to walk into department stores, like K-mart, etc and be driven out by their 19Khz alarm system... If you can hear that, you definitely have a good set of ears on you. I still have a friend that can hear up that high, and he will cover his ears and scream while in these stores... (NOT THAT I SHOP AT K-MART IN MY TL-S!!!) and I'm saying "What sound"...

dian1511

Could not fit anymore names.

You are some of the guys who either have kept the stock head unit or given advice on this process.

Please help. Southbound has given great info on the theoretical how. I am interested to know the outcome. How did your installs end up? I know that Allanc45 was struggling with some noise. Anyone else? Which worked: Line level or speaker out? (Is this correct?) One of the posts stated that line level was cleaner?

Brewboy

I have tapped the pre-EQ signal from the HU and routed it to aftermarket amps for my fronts and sub. The rears remain on the EQ'd HU signal as stock. I have no noise to speak of. All taps were soldered.