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jeffreybehr 31st December 2012 10:11 PM

My car-audio system, rather a DIY project
Bought a 2010 Ford Escape XLT last August. It contained the standard CD-radio, 4-speakers-in-the-doors Ford system. Being a hi-end audiofool...cough, cough... :o
...that system wasn't nearly good enough--all the music came from around my knees, the speakers sounded gritty, the system had no low bass, etc. So first, new door speakers.

I again chose the SonicCraft 6-1/2" drivers I've bought literally by the several dozens over the years...
[That CC speaker had 4 of those in its bottom, too, for a total of 10. That system didn't last long. :-( ]
...and installed them in the 4 doors...

Then, after installing and finding unsatisfactory a pair of top-mount tweeters, I installed a pair of Polk home-system TL1 Sat speakers atop the instrumentpanel. This got the orchestra in front of me, finally, and improved the overall sounds considerably. All this was still driven by the stock CD-radio.

Also around this time I rewired the rear-door speakers in series and then wired them across the rear-channel-positive-only speaker leads. This of course reproduces only the difference between the 2 channels. They're somewhat low in level and rather 'phasy' and spacious, and this added a bit of spaciousness to the overall sound.

For bass, and not wanting to add any kind of box that'd be in the way too often, I installed a Lanzar one-piece powered SW under the RF seat.
That added the missing midbass and some bottom-octave bass.

BUT...I felt things could be better still and started investigating poweramps. After a highly trusted audio 'guru' told me that I really wouldn't like the sounds of modern digital car-stereo amps and a long-time friend agreed and pointed me at the old Apine V12 series of amps, I found on eBay and bought an Alpine MRV-F303 amp in excellent condition for only $146 delivered. It's rated (14.4VDC in, 4 Ohms out) 50 Watts, continuous, times 4 channels. It had the hi-pass filters that would eliminate overdriving both the front-door and Polk TL1 speakers with too much bass, and under the LF seat it went*. I chose Audioquest cables for the front speakers--Type 2, 4-solid-long-grain-copper-conductor cable for the instrument-panel Polks and G2, a stranded type for the frontdoors.

WOW what a difference, all good. Then within the Polks, I removed the cheap 300uF 'lytic cap in series with the 'bass'/MR driver that was used to limit bass and increase power handling. Also replaced the cheap 'lytic in the tweeter network with my last of the great-sounding BlackGate NonPolar caps, and the sounds got even better. The system now sounds quite good on an absolute scale.

Of course, being an incorrigible tweak, I can't leave well-enough alone, so I bought another 'F303 amp and a Service Manual and started scheming on how to improve the sonic quality of the poweramp.

Input/output end.

Controls end.

Decided to limit myself somewhat on this project and NOT replace about-every 'lytic cap in it. :o In channels 1 and 2, driving the Polks, I've replaced the 4 coupling caps--all cheap polarized 'lytics--per channel with SoniCap 'propylenes. Also am removing all PS-rail-bypass caps in the preamp and output sections with combinations of large and small SoniCap 'propylenes.

I hate working on PC boards, especially those full of small stuff, so my goodbuddy is doing this work. I'll add some pics later.

* Meanwhile I had purchased a new Soundstream REF4.400 poweramp, but it was too long to install.

jeffreybehr 3rd January 2013 10:15 PM

Wow, 170 views and not ONE comment? Not even 'boring!'?

Perry Babin 3rd January 2013 10:34 PM

I don't help with amp mods unless there is a reliability issue.

You stated that you wanted to improve the sonic quality but didn't mention what you thought was lacking.

osburnsw 3rd January 2013 10:41 PM

Ha, I will give it a thumbs up.

jeffreybehr 4th January 2013 06:01 PM


Originally Posted by Perry Babin (
I don't help with amp mods unless there is a reliability issue.

You stated that you wanted to improve the sonic quality but didn't mention what you thought was lacking.

1. Well, I didn't ask you to help, Perry; aren't you glad? :) This forum is so full of amp-repair threads, I thought I'd add something more general.

2. I find often that I didn't know what goodness was missing until it appears or I didn't know what badness was present until it's gone. In home audio equipment, these kinds of mods reduce edginess...grittyness...and hence the music sounds more like music and less like hi-fi equipment.

Osburnsw, TY.


Got the amp recapped.
In the powersupply, replaced both pairs of 'chicklet'-type 0.047uF and 0.056uF bypass caps with 0.047/100 MultiCap RTXs ('styrenes). Was tempted to replace a pair of 330uF/35s 'lytics bypassing the output-stage rails with maybe hi-Q Nichicons, but didn't.

Preamp section:
1. Replaced all 4 coupling caps, cheap 'lytics, in channels 1 and 2 with 0.47/200 SoniCap Gen.2 'propylenes.
2. Replaced all 8 DC-rail-bypass caps, 4.7/50 'lytics, in all 4 channels with 4 7.5/200 SoniCap Gen.1s bypassed with 0.47/200 SC Gen.2s.

Output stage:
1. Pulled all 8 DC-rail bypass caps, 0.47/50 'lytics, in all 4 channels. Replaced with 4 5.1/200 SC Gen.1s bypassed with 4 0.47/200 SC Gen.2s plus 4 more of the latter on the board.
2. Replaced all 8 emitter resistors with 5W Mills MRA-5s, noninductive wirewounds.

Just for kicks, and every time I did something like this in this car-stereo amp I laughed at myself, I replaced all the magnetic, brass-plated-steel speaker- and power-wire hold-down screws with nonmagnetic stainless-steel screws and lockwashers and brass flatwashers.

Pics! We've got pics!

Closer on the output stage.

Controls end.

If anyone wants bigger pics, e-mail me at jeffreybehr(at)cox(dot)net and tell me how many pixels wide you want them.

The amp worked instantly, and no smoke escaped! :D

My goodbuddy Pat did all the work, as I don't do well with circuitboards with tiny components and traces.

jeffreybehr 13th January 2013 10:03 PM

Am still playing with balances, etc.
Of course we all realize that the more flexible (= adjustable) a system is, the easier it is to seriously maladjust it!

Was still not satisfied with the level and quality of mid- and bottom-octave bass and overall system warmth--that being the sense of high energy in what one of my GEA-goodbuddies calls the power region of the orchestra. Moved the Polks' HP filter down to 75Hz and was pleased with the level and quality of mid- and upperbass from those tiny 'bass'/MR drivers.

Then got a little brainwhiff* and instead of running the frontdoor speakers full range--I'd started weeks ago driving them thru a 50Hz HP filter--I decided to drive them with bass only. Switched on the LP filter for those channels and started with 50Hz. Changed that quickly to 75Hz at a lower level. Now have more mid- and upperbassbass, and warmth, without turning the sounds thick, muddy, syrupy. Hmm...this may work. :cool:

Also, 'decoupling' the frontdoor speakers from the Polks seems to make it easier to get a more-pleasing left-right balance.

* Some of us have brainstorms; I have brainwhiffs.

Brams96 26th February 2013 09:50 AM

What improvemnets did adding the Sonicaps make to the overall ambience & clarity of the sound?

jeffreybehr 26th February 2013 10:04 PM


Originally Posted by Brams96 (
What improvements did adding the Sonicaps make to the overall ambience & clarity of the sound?

Brams, I believe the clarity...detail...of the sounds improved, while the edginess decreased. Of course, since I'm no golden-eared audiofile able to hear and describe the most-subtle of sonic differences, my impressions may be more wishful thinking than anything else. What I do know is that this is now the best-sounding auto-stereo system I've ever heard.

BTW, one thing I plan to do is install a 1- or 1.5-Ohm resistor in series with the Polks' tweeters to reduce their output a bit. That way I won't have to run the treble control at -1 or -2.

Brams96 1st March 2013 12:14 PM

That's good to know, thanks for the info.

MatthewS 3rd March 2013 07:16 PM

Free bump for a masterpiece :)

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