The current sound system in my 190E consists of a basic Kenwood head unit, 4" speakers in the dash and 5.25" speakers in the rear shelf (both aftermarket). In those cars, the doors had some "mini-subwoofers" powered by an amp in the trunk. But as you can guess, the amp is toast and the "mini-subs" are probably dry. That part doesn't work now and it never worked for as long as I owned the car. The sound is terrible. There is absolutely 0 bass and as soon as you turn up the sound just to hear the music on the highway, the speakers sound like they are going to explode. The wiring is 30 years old and the rear Sony Xplod speakers surrounds are cracked. I put the dash speakers in a few years ago, they work somewhat good but with their small size you cannot expect incredible results.
I am piecing together a basic system that I think will give me better sound. I never played with car audio much, so I don't know all the details. I looked around on FB marketplace and purchased 2 items:
1- 6x9 Pioneers for the back, circa 1992 or so:
2- Sony XM-450 4-channel amplifier, circa 1996-ish:
Both are somewhat old, but in good condition. I thought it was kinda cool that they were somewhat period-correct for the car.
I am planning to use the amp to drive the front dash speakers and the rear Pioneers and remove the door "mini-subs". I will run 100% new wiring. I thought about using the amp to drive the "mini-subs" and the rears and drive the fronts off the head unit, but I have a feeling I will get better results by not using the so-called mini-subs
The problem is that the amp only has the "RCA" low-level inputs. The head unit has one set of RCA outputs, but the manual says it's a "subwoofer preput". Is the signal coming out of that output the same as it would be for speakers or has it already been conditioned for a subwoofer? Could I use this to drive the rear speakers and use a line-out converter to convert the front speaker signal? Or should I get a 4-channel LOC and convert both speakers output to low-level and use that to drive the amp?
What model is the Kenwood? If it is full range output from the line-level outputs then you could avoid using the line-level converter that you mentioned. I personally would rather use that existing line level output instead of adding a level converter but it seems like there might be one inf your future otherwise.
If your head unit only has a subwoofer preout then it more than likely has plenty of wattage to drive full range speakers. If it were mine to do I would replace all the speakers with new speakers that offer better sound quality and buy a small stand alone powered subwoofer to mount in the trunk. I would also consider getting a new head unit too.
I know you want to remain period correct but simply put audio equipment wears out and nothing offered in the 1990s comes close to the sound quality you can get today.
The HU is a Kenwood KDC-138. Here's a screenshot of the page in the instruction manual where it describes how to wire it. The "front preput" is for another model, I don't have it.
I just noticed it says "rear preput/ (or) subwoofer". It's probably fine then. I'll use a LOC for the front speakers.
I don't absolutely want it to be period correct, I just stumbled upon the speakers and the amp for cheap! But at the same time I don't want to put hundreds of dollars in that, so I'm trying to use what I have. I'll start with those parts and I'll replace if I think it is not enough.
Funny thing is that I pieced together a home system with all 80's components and it plays way better than I expected it to. Big Kenwood KL-5050 speakers, Technics amp and Dual turntable. It can play incredibly loud and the sound quality is excellent. The only "new" item is the needle on the turntable. I guess car audio degrades over time since it's always exposed to extreme temperature changes...
Information from here: Kenwood KDC-138 CD receiver at Crutchfield
Makes me believe that the receiver has pretty good power for speakers and the pre-amp out is at minimum full-range and might also offer a selectable subwoofer-only low frequency output.
If you don't think you need a front to rear fade function then you could run the amp off of that pre-amp output and not need the "LOC". OR you could just use the internal amplifier and not bother with the external amp unless/until you decide you want a powered sub in the car as well. That's probably what I personally would do because it's simple and I'm pretty basic about such things.
it look like xm450 is a 4 channel with crossovers all you should need is a set of rca Y cables to turn you 2 channel out put into 4 channel output. if you NEED fading you can get a rca level fader or just put amn rca level controller on one set.
Then hipass the fronts and lopass the rears.. the only thing that would make it easier for you is if you could use one set of rca inputs to drive both pair of outputs. (internal Y) or high level inputs
your headunit is full range OR subwoofer (already lopass filtered)
My answer is... head units never have enough power. That's not just me saying more is better, they seriously stretch the imagination when they try to suggest that a head unit that is the size of two packs of cigarettes can actually make the power numbers they are claiming. When you push it even vaguely close to those power numbers, it's so dirty and it never sounds right... especially with aftermarket speakers.
Here is what you need to know about matching speakers to amps. It's like matching engine size and torque to vehicle weight. Speakers get their power handling capacity from the size of the magnets and coils. Trying to drive high-capacity speakers with a head unit is like trying to power a school bus with a motorcycle engine. Not enough oomph to effectively move the speakers. If you hook up your new speakers to just the head unit, I think you will be incredibly disappointed. You want to somewhat closely match the rated watts of the speaker to the rated watts of the amp. Now, in the opposite direction, giving the speakers too much power is like putting a big block in a go kart. If you floor it, you'll rip the go kart in half... but the beauty of that situation is that you don't need to floor it. You can always overpower a speaker because you control the volume and gain knobs. You don't have to turn it up to 11. You don't have to extract all 2000 watts from some mega-amp. My current home theater is giving 130w per channel to speakers that are rated for 50w.
Here is a basic generalization. As you turn up the volume, the signal distortion increases. Since a given speaker at a given frequency range can provide X decibels of output, it is usually the case that with big power only turned up to 5 will produce a much cleaner sound than a small amp turned up to 10, but both of those situations will have the same dB.
Those Pioneers are probably about 40wrms (rated wattage). That amp looks like a 50w x 4. That is bloody perfect. I looked up the manual. It appears that you need two sets of RCAs to get all four channels? Kinda odd. Dig into it here: W0012834M.pdf (sony.com) but normally you have the option. If you use two sets of RCAs (front and rear) then you can still use the head unit's fader to adjust front/rear, or if you just use one set of RCAs, you just set the fader to rear and all four get the same juice. Doesn't look like that amp will do that.
The head unit needs some investigation as well. If the RCA outs are just subwoofer, then that means it's just sending low frequencies out. If that's the case, you'll need to line-level convert every speaker output to get RCAs for the amp. Not the end of the world, but 4 LOCs might cost as much as finding another inexensive amp that has speaker-level inputs. Just a thought.
I say, run the speakers off the amp and ditch the wee subs. The wee subs in the door are a lost cause anyway. Free-air small subs are the worst possible environment for them to be working. Sending them power to try to sound better is like painting a house that has already collapsed. If you find you need more bass later, repeat what you did today by buying another cheap amp and a cheap 8" sub, and put it in a $10 yard sale box.
Curtis73 (Forum Supporter) said:
You don't have to turn it up to 11.
Your lips are moving, but I don't understand what you're saying here.
SkinnyG (Forum Supporter) said:
Curtis73 (Forum Supporter) said:
You don't have to turn it up to 11.
Your lips are moving, but I don't understand what you're saying here.
What if I'm at 10 already and I need 1 more?
But thank you all for your answers. I read the manual for the head unit again and it seems like the output can be used for either "rear" or "sub". You can select which one you need in the menu. I will run a pair of RCA's to the back of the car and I'll split them so I can connect to both inputs on the amp. I don't think I'll need the fader.
In reply to Loweguy5 (Forum Supporter) :
You're welcome to disagree. My point is that you set the gain of the amplifier to match the output you need so that turning up the volume doesn't exceed the excursion or wattage rating of the driver. A 50w amplifier with the gain at 7 might send the same current as a 2000w amplifier with the gain at 1. Hence why I added the comparison of dB.
But I agree.... if you try sending 2000w to a 50w speaker, yes. If one tries to listen to a speaker while it's trying to eject the voice coil, one is an idiot. If you use your ears and don't want to listen to rattles and smell smoke, it doesn't matter what the noise floor is.
The point is, if he wants to use a 100w amp on 50w speakers and turn down the gain a bit, it is fine, and has the added benefit of not driving the amp in a realm where electronic distortion is high. This is preferable to using a 25w amp on a 50w speaker and having to crank things up where distortion becomes a problem in an attempt to get the same dB.
Higher wattage + lower gain = more dB before electronic distortion. Notice I said electronic distortion. That has nothing to do with the physical properties of the speaker and whether or not the cone/driver offers physical distortion. Also notice that I didn't say it was impossible to overpower and damage a driver. Been there, done that. I said it's OK to overpower a driver if you adjust volume and gain accordingly.
