BMW 318is Speaker Size

Rear Door Panel Speaker

Front Door Panel Speaker

BMW 318is Speaker FAQ

What speakers should I upgrade first in my BMW 318is?

Start with the front door panel 5.25-inch speakers. These handle most of your music's critical midrange frequencies and vocals. The front speakers in the BMW 318is typically receive more power from the head unit - around 15-20 watts RMS. Upgrading here gives you the biggest immediate improvement in clarity. Rear speakers can wait since they mainly provide fill and ambiance.

Can I install component speakers in my BMW 318is rear doors?

The rear door panels support both coaxial and component types, but coaxial might be more practical. Component systems need separate tweeter mounting locations. Your BMW 318is rear doors probably don't have dedicated tweeter spots unless you're working with a 1991 model. Most aftermarket 4-inch coaxials will fit the 1992-1997 rear locations and deliver decent sound without major modifications.

Why does my 1991 BMW 318is have different rear speaker sizes?

BMW changed the rear door panel design after 1991. The 1991 model used 5.25-inch speakers in the rear, then switched to 4-inch for 1992-1997. This might be related to cost savings or interior redesign. The 5.25-inch setup potentially offered better bass response in the rear. If you have a 1991, you've got more upgrade options since 5.25-inch speakers typically handle lower frequencies better than 4-inch.

What impedance should I look for in BMW 318is replacement speakers?

Stick with 4-ohm speakers for your BMW 318is. Most factory BMW systems from this era were designed around 4-ohm loads. Going with 8-ohm speakers might reduce volume levels since the head unit expects the lower impedance. 2-ohm speakers could potentially stress the amplifier circuits. Component speakers often come in 4-ohm configurations anyway, so you should have plenty of options.

Do I need an amplifier for aftermarket speakers in my BMW 318is?

The front 5.25-inch speakers might benefit from additional power, especially if you choose components. Factory head units typically push 10-15 watts RMS, which works for basic coaxials but leaves component systems underutilized. A small 4-channel amplifier running 25-50 watts RMS per channel would wake up your BMW 318is sound system. The rear 4-inch speakers are less critical for amplification unless you're chasing serious volume levels.

Will 6.5-inch speakers fit in my BMW 318is front doors?

No, the front door panels are specifically sized for 5.25-inch speakers. The mounting holes and speaker grilles won't accommodate 6.5-inch drivers without significant modification. You'd need to cut metal and possibly relocate other components. Stick with quality 5.25-inch speakers - there are excellent options available that will dramatically improve your BMW 318is sound quality without requiring bodywork.