BMW 635CSi Speaker Size

Dashboard Speaker

Rear Deck Lid Speaker

BMW 635CSi Speaker FAQ

What speakers should I replace first in my BMW 635CSi for the biggest sound improvement?

Replace the rear deck lid speakers first. The 6.5 inch speakers in the rear deck handle most of the full-range audio and typically show more wear after 30+ years. These coaxial or component speakers around 50-75 watts RMS will give you the most noticeable upgrade. The 4 inch dashboard speakers can wait - they're mainly for mid-range fill and won't dramatically change your overall sound quality. Focus your budget on quality rear speakers first, then upgrade the dash units later if needed.

Can I install component speakers in the BMW 635CSi rear deck location?

Yes, the rear deck lid accepts both coaxial and component 6.5 inch speakers. Component systems might give you better imaging since you can position the tweeter separately. However, coaxial speakers are simpler to install and still provide good sound quality. If you go component, you'll need to mount the crossovers somewhere accessible but protected from heat. The BMW 635CSi has decent space behind the rear deck, though routing tweeter wires to optimal positions requires some creativity.

What power rating should I look for in 6.5 inch speakers for the BMW 635CSi?

Target speakers that handle 20-75 watts RMS continuously. Most aftermarket head units push around 15-25 watts per channel, so you don't need speakers rated for 100+ watts unless you're adding an amplifier. The factory speakers were probably around 10-15 watts, so even modest 40-50 watt speakers will be a significant upgrade. Focus more on sensitivity ratings - speakers around 88-92 dB sensitivity will sound louder with less power from your BMW 635CSi's stock system.

Are the 4 inch dashboard speakers in the BMW 635CSi worth upgrading?

Maybe, but they're not your priority. These full-range speakers mainly fill in mid-frequencies and vocals. The improvement tends to be subtle compared to upgrading your main 6.5 inch speakers. If your dash speakers are cracked or blown, sure, replace them. Look for 4 inch speakers with good midrange response around 500Hz to 4kHz. Don't expect much bass from these locations - the BMW 635CSi dashboard mounting just isn't designed for low-frequency reproduction.

What impedance should I choose for BMW 635CSi replacement speakers?

Stick with 4-ohm speakers for both locations. Most car audio systems, including the BMW 635CSi, are designed around 4-ohm loads. Using 8-ohm speakers will reduce your power output by roughly half. Some installers use 2-ohm speakers for more power, but that can stress older head units and potentially cause overheating. The 4-ohm rating gives you the best balance of power transfer and system stability, especially important in a car where the electrical system wasn't originally designed for high-power audio.