There is more bass from the left speaker than the right. They are not wired incorrectly.

First try swapping the cables and put the left speaker cables in the right hand amp output and the right speaker in he left output. If the problem stays in the right hand speaker and does not move to the left as I suspect should, then it is a problem with your speaker crossovers. You may have to open up the speaker and check the wiring and then crossover. If the problem changes and appears in the left hand speaker you have an amp problem.

yeah, you are going to have to cut off that factory speaker connection, but leave a few inches of wire on the end so you can re-attatch that connector later, should you sell the car, re-install the factory speakers and keep your after market speakers for another car. one of the wires has a stripe on them, (never mind the color) connect the stripe factory wires to the stripe speaker wires with 'wire-nuts', or twist the bared wire and tape them with electrical tape, the stripe wire to the positive speaker post. the other wire will of course go to the negative speaker post. once you have both speakers wired up, play some music with good bass, and move your speaker balance from one side to the other, if your speakers are connected properly you will hear more bass with both speakers than with the balance all the way left, or all the way right.

check your wiring

Here is the radio wiring.
2008 Dodge Ram 1500 Car Stereo Install Instructions
Car Radio Battery Constant 12v+ Wire: Gray/Red
Car Radio Ground Wire: Black
Left Front Speaker Positive Wire (+): Dark Green/Yellow
Left Front Speaker Negative Wire (-): Dark Green/Light Blue
Right Front Speaker Positive Wire (+): Gray/Yellow
Right Front Speaker Negative Wire (-): Gray/Light Blue
Left Rear Speaker Positive Wire (+): Gray/Light Green
Left Rear Speaker Negative Wire (-): Gray/Dark Green
Right Rear Speaker Positive Wire (+): Dark Green/Gray
Right Rear Speaker Negative Wire (-): Dark Green/Light Green

if these speakers are several years old, chances are that the left one is just blown. could be a loose wire, but if not, it would be cheaper to get new speakers than to get that one fixed

Check the balance, just to be sure. But, yes, most stereo's output more bass on one channel than the other. Bass is omnidirectional, so it doesn't need to be the same on both sides.

If you think it might be a speaker issue, swap the speakers and see if it stays the same - if it doesn't, you've got a speaker problem or a wiring problem. Make sure each speaker has the same length wire, and the same type/gauge.

On the back of the receiver you will find the connections for the right and left speaker, OR if it is surround sound you will find, right front, right rear, left front, left rear, and center or bass. The connections can be RCA type jacks or they can be wire clip type.

Depending on the connections on the receiver and on the speakers, the wire will have to match the connections on each end. The wire needs to be large enough to handle the power output of the receiver. Wire can not be too large but it can be too small. Larger wire is more expensive, so there is no benefit in purchasing excessively large wire. Packaging should designate the power handling capability of the wire. The wire should not be much longer than is necessary to place the speakers where you want them. Too long wire unnecessarily cuts down on the power to the speakers. Don

Please rephrase. "5.1" and "only ... front right and front left" are mutually exclusive. Look at manuals.

In general, bass is 'managed' by directing it toward or away from any speaker the user declares to be LARGE or SMALL, usually based on arbitrary cone sizes instead of bass handling capability. There 'managed' bass is rerouted to the presumed capable LFE/Bass/Subwoofer channel to avoid potential damage to bass-shy speakers. Therefore, if one lacks a subwoofer one has to tell that to the receiver and designate the other speakers as LARGE or the bass will get tossed in the bit-bucket

Hello pinkpimpin20,

Without knowing exactly what modifications were made to the factory sound system, it's difficult to point you to a particular fix. The number of channels on the "big amp" that you disconnected would help. Even the make and model.

But, from your description it's possible that the previous owner installed a multichannel amp to drive both the "extra bass speaker", usually referred to as a subwoofer, and the original vehicle speakers. In that case, the speaker wiring from the head unit (receiver) was cut and the receiver side of the wires was rerouted to the input of the aftermarket amp. The output of the amp was then connected to the other ends of the speaker wiring.

To restore to the original, you need to pull the stock receiver and resplice the wiring. If the previous owner cut the plug completely, it may be necessary to purchase a replacement from your BMW dealers service or parts department. It's possible, but not likely that the previous owner used both an aftermarket "harness" and an aftermarket "reverse harness" to avoid having to cut the wiring. In that case, all you'd have to do would be remove them and plug the radio harness back into the vehicle harness (or the back of the radio). But most DIY audio enthusists don't mind butchering the vehicle wiring. And you'll probably find that electrical tape was used to secure the wiring. After a year or so under the dash, it'll be a sticky mess to unravel.

The speaker wiring colors for the '93 318i are as follows:

Left Front Speaker Wire (+): Yellow/Red
Left Front Speaker Wire (-): Brown/Orange
Right Front Speaker Wire (+): Black/Red
Right Front Speaker Wire (-): Brown/Orange
Left Rear Speaker Wire (+): Yellow/Black
Left Rear Speaker Wire (-): Black/Orange
Right Rear Speaker Wire (+): Blue/Black
Right Rear Speaker Wire (-): Brown/Orange

Hope this helps.

A couple things to check on the no bass problem:
1) Make sure your center speaker is set for normal, not large.
2) Make sure your speakers wires are in phase (+ conn. to + and - conn. to -).