Car Stereo Folks - Advice request

[JHZR2]

Hello,

I have two euro cars which i am looking at doing an audio upgrade upon, to help improve their sound quality.

Money is not an issue, but I know Ill have deminishing returns because of my guidelines, so Id appreciate insight on how to do it properly.

Both cars have headunits that only have left and right channel outputs (the cars have 4-speaker systems, but they are split at a rheostat fader that ill take out of the loop.

So, here is the deal - headunit has a left and right out. Ill be amping this signal, then sending it to the four corners where Ill have newer, better speakers installed.

My major question is, given that the system was set up as is, and thus I have only one set of inputs to the amp, am I better off using a 2-channel amp that takes those two channels in, amplifies the signal, and then set my speakers up in parallel, or should I use an RCA splitter to feed front and rear channels on a 4-channel amp, and then wire up the speakers individually?

I realize that Ill not be able to fade with the 2-channel setup, but I only have 2-channels going to the amp in reality, and I never fade anyway...

So, what do you reccomend, given that I have two channels coming from a factory headunit? 2-channel amp with 4 speakers wired in parallel, or split the headunit output into 4 channels and then have 4 in and 4 out?

Thanks!

JMH

P.S. If I have a speaker level to RCA converter, should I split the speaker level output before or after the converter? I could splice a second converterinto the line out from the head unit, or I could just use an RCA splitter, and I suppose turn up the gain a bit. Any preference? I want to optimize sound quality...

 

[MysticGold04]

I'd run the splitter, unless you can find an amp which will do 2 ohm loads, and then you can run them parallel. I'd just use the splitter though, to make it easier and

on!

 

[JHZR2]

got it, thanks!

It seems that most amps give a power rating at 2 ohm, so running any decent amp in parallel would be OK, but I agree it does seem easier...

Thanks,

JMH

 

[rjundi]

I am a little unclear on what your doing but it sounds like your converting speaking level output to RCA level?

These setups typically have noticeable hiss as your essentially taking the distortion of the head units output and only amplifying it. There is no way around it.

Before you spend your hard earned money and go down this path, go to a reputable stereo shop and have them demonstrate their product.

I was far from impressed so I stuck with my ok sounding but matching the OEM dash head unit as I cannot find any head unit with a 6 disc changer built in that is not ugly.

 

[kkreit01]

I'm assuming your HUs are factory? If so, you will be much better off using a Line Output Converter to convert your high speaker-level inputs to RCAs.

On to your other question... I would not power the rear speakers. I would just run them off deck power. Just like at home, or concerts, you want your strong sound stage to be in front. The rears are used for fill-in. In this case, you can easily add your 2-channel amp. If you wish to add a sub later, buy a 4-channel amp now. You can then run your front speakers off 2 channels, and bridge the remaining two for the sub.

Depending on your current HU, the OEM deck is often the weakest link in the system. But, it's smart to start with speakers -- and go from there.

 

[Tosh]

You could also shop for higher-than-average sensitivity speakers and run them directly off the existing head unit and fader. An extra 3dB is equivalent to doubling your power. Car speakers usually have a sensitivity around 87dB/W*m, so if you can find some that are over 90dB, then they'll be louder without extra amps.
Then you could add amps later: Get two separate stereo amps with built-in high level inputs for front and rear. Then you could still keep the fader...

 

[shortyb]

Start with the better speakers first, you may be pleased with just doing that. If not, then go onto an outboard amp. There are several companies now marketing products aimed directly at what you are trying to accomplish. They understand that folks want to keep their H/Us for various reasons (usually aesthetics) but need better sound. The progression of sound quality in an OE application usually runs (worst component to best component) speakers, amp, H/U.

 

[Papa Bear]

I agree with shortyb whole heartedly...

I think Billy Joel said it best: "You'll get more mileage from a good set of speakers"

 

[rpn453]

Quote:

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You could also shop for higher-than-average sensitivity speakers and run them directly off the existing head unit and fader.

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Just make sure everything else is good about the speaker if you're looking at sensitivity values! It's measured at 1khz only, so speakers that are overdone at that frequency may have high sensitivity values but sound horrible.

 

[Master ACiD]

not that it REALLY matters but id like to get a bigger picture. what make model and year car are we talking about.

youre going to use the FACTORY headunit? and it has left and right output, and 1 set of pre amp outputs?

what kind of music (or noise if you say rap) is going to be played, and at what volume levels.
how big is the trunk and where are the speakers located, dash, door lenals, kick panels, rear deck, etc.

why do you feel that you need an amp for the speakers.

 

[JHZR2]

OK, here we go:

First car: 1991 BMW 318i. No eplacement headunits look anywhere near proper or a clean install in this car... just isnt going to work.

5 1/4" speakers all around, fronts are in the kickpanel, but have a built in crossover that feeds tweeters on the sail panels in the door. Rears are on the parcel shelf.

The car has two headunits, the one in it when I bought it was the so-called 'premium' headunit, which utilized a rheostat fader in the dash, and only has a left and right channel (the fader splits it). The other has two sets of outputs, front and rear left and right, and was actually the correct headunit for my car OE, however it just kicked the bucket. When I got the car, the 'premium; headunit was hooked up, with both speakers in parallel to the single left and right out.

The other car: 1985 MB 300D: replacement headunits look OK, but they are too techy for the style of this car. I prefer an original look to my cars, especially since this one is older, so the Becker Europa (upgraded with direct ipon input, NOT modulated) stays.

This car has 4" speakers in the dash and 5 1/4" speakers on the rear deck. This headunit has a left and right channel out, and passes the signal to a rheostat ader which splits it and biases it front to rear.

Neither headunit has any pre-outs. For that I plan to use a PAC trunc-LOC, which also creates a 12V trigger to turn on the amp.

The speakers that I plan to get are MB Quart (I know MB has nothing to do with Mercedes, in fact, this brand is owned by rockford fosgate). The sensitivity on the speakers is 85-87. I would like to use an MB Quart amp too, as they are very compact, and I dont desire to have a lot of power or play too loud.

As for music, tower of power is my favorite band. Usually Ill have on the oldies station or that sort of music... blood sweat and tears, earh wind and fire, steely dan, bruce springsteen... though I do like some hard rock and country every now and again.

Funky bass lines are great... though I cant make that great of bass from any 5 1/4 speaker, and Im OK with that... no rap though...

Thanks,

JMH

 

[Master ACiD]

heres what i would do if i were you.
if you stickin with those oem headunits, do what you suggested and grab an amp, get a 4 channel even tnough you only have 2 channels. try to find an amp with a built in high pass crossover so that you can filterout the low frequencya from the main speakrers. if one isnt available you can make a passive crossover out of a few capacitors wired in parallel with the speaker. i cna explain this later if you like. its super simple and radio shack has all the parts. cost is a few bucks. use the speaker level inputs to split the 2 channels into 4,
to the right channel would be hooked up to channel 1 and 4 of the amp. the left channel goes to 2 and 3.

wire the amp to have its output going to the 4 speakers, forget the tweeters on the bmq. if you change the factory speakers to aftermarket and try to use the stock tweeters it throws the sound out of wack. my sister has a 91 325i convert with the same exact setup and thats what we discovered after many weeks of screwing around.

so far that applies to both the benz and the bmw.

next part is optional but HIGHLY recomended. get a subwoofer. the 4 channel amp you used for the main speakers probably has a pre amp output. connect this to the preamp input of the subwoofer amp. grab youreself a nice but highly compact sub, somthing like a single 8 in a sealed box. these are cheap and good enough for rock and the type of music you like. nearly all music is made for the full spectrum of frequencys. this includes subwoofer frecuencys. even classical music has sub frequencys. most people think they dont need a sub, but if they hear their music played on a decent stereo with a sub, all the sudden you hear sounds and gituar notes you never heard before. its like discovering the music over again for the very first time. i cant stress this enough, suwoofers are NOT just for rap and shake youre butt to the base. lots of rock including the bands you mention have low frequencys in their music that most people miss out on. if you try a sub you wont ever go back.

im sure patman will chime in here to back me up. i dont how loud you like youre music but if you have a high pass crossover on the main speakrers set at 200hz for instance, and the sub is set for a low pass crossover at 220hz, then the main speakers can very very loud before distorting. the sub takes care of the lows, and you can have a very loud but clean sounding system for not much money or time.

best of all with the highpasses on the mains, youve got no risk of blowing the speakers from listening too loud. its just a win win situation.

this is how i have my car setup and its just fantastic. i have a rule in my car, no rap allowed! but everyone who hears my stereo agrees the subwoofer is incredible for rock music.

little 5.25's and 6x9's etc are not made or capable of reproducing low frequencys at any level. theres alot of music missed out on by not having a sub, its hard to stress this enough wihtout sounding like a jerk but its the truth. best of all you can do this for very cheap.

dont worry about bridging and other autophile technical jargon. you just need a couple of simple parts and to spend a bit of time wiring the system with quality connectors and wire and youll have a great setup.

 

[shortyb]

+1 for T.O.P., I have about every CD they have released. I play "What is Hip" about every other day. Saw them live at Wolf Trap about 8 years ago with B.B. King. Awesome.

Master is on the right track and has lended some very good info, especially in regards to band-pass filtering/crossovers. One place I suggest you ring up is Bavarian Soundworks. They specialize in upgrading German machines and are VERY competent. They also have Rainbow speakers which until I heard a set, didn't think they could top MB or my personal fave Boston Acoustics. I was wrong. So smooth and rich sounding (from a stock H/U no less!). Another option that I have seen and heard is the Basslink II sub from Infinity. The one with the built in 4 channel amp. I'm usually not a big fan of self amplified subs, but they did their homework and have been the only ones I've heard to input speaker level signals and NOT produce any noise/distortion etc. Relatively small unit with a 10" active driver and 10" passive. Built in crossovers with pretty steep slopes of dropoff. Crutchfield has them for ~$400 right now and that includes the amp for "free". Worth a look.