BMW 733i Speaker Size

Front Kick Panel Speaker

Rear Deck Lid Speaker

BMW 733i Speaker FAQ

What speakers should I replace first in my BMW 733i?

Replace the front kick panel speakers first. The 4 x 6 inch speakers handle most vocals and mid-range frequencies you actually hear while driving. Rear deck speakers mostly fill in bass and ambient sound. Front speakers carry maybe 70-80% of what makes music sound clear versus muddy. The kick panel location also means easier access - rear deck replacement involves removing trim panels that might crack on older BMWs.

Can I install component speakers in the BMW 733i rear deck location?

Yes, but it's probably overkill. The rear deck accepts 5.25 inch coaxial, component, or full-range speakers. Component speakers separate the tweeter from the woofer - great for front staging but less critical in rear positions. You'd need to mount the tweeter somewhere else anyway since most people sit in front seats. Coaxial speakers work fine here and cost less. Save the component money for front upgrades.

Why does my BMW 733i have different speaker sizes front and rear?

The 4 x 6 inch front speakers fit the kick panel space constraints, while 5.25 inch rear speakers utilize the larger rear deck area. Different sizes doesn't mean worse sound necessarily. The 4 x 6 speakers actually handle mid-range frequencies well - that's where vocals live around 1kHz to 3kHz. Rear 5.25 inch speakers can push more air for bass response below 100Hz. BMW probably designed this to balance space efficiency with frequency coverage across the cabin.

What power handling should I look for in BMW 733i replacement speakers?

Aim for 50-75 watts RMS for the front 4 x 6 speakers, maybe 75-100 watts for the rear 5.25 inch units. Most factory BMW head units from this era push around 15-20 watts per channel. If you're keeping the stock radio, almost any aftermarket speaker will be underpowered anyway. The impedance should be 4 ohms - that's standard for car audio and matches what the BMW 733i electrical system expects. Higher wattage ratings just mean the speakers won't distort if you add an amplifier later.

Do full-range speakers sound better than coaxial in the BMW 733i?

Full-range speakers use a single driver for all frequencies, while coaxial speakers add a separate tweeter for highs. Coaxial usually sounds better because dedicated tweeters handle frequencies above 3kHz more efficiently. The BMW 733i cabin is fairly large, so you need that tweeter to cut through road noise. Full-range speakers might work okay in the rear deck where high-frequency clarity matters less. But for front speakers, coaxial gives you better vocal definition and cymbal detail.