Siblings in JBL's Studio series, so they share a family sound. It comes down to size, output and price.
| Area | Better | Why |
|---|
| Bass | B | JBL Studio 6 88LCR digs deeper - 43Hz against 58Hz. |
| Amplifier needs | B | JBL Studio 6 88LCR is more sensitive (96dB vs 90dB), so it goes louder on the same amplifier. |
| Size | depends | JBL Studio 6 88LCR is easier to place; JBL Studio 665C is bigger, which usually goes with fuller bass. Your room decides. |
| Type | depends | A Passive Center Channel against a Passive In-wall - a different job rather than a better one. |
| Cabinet | depends | Ported vs In-wall. |
| Price | A | JBL Studio 665C is cheaper - $400 against $1,600, about 75% less; arguably a different class. |
A JBL Studio 665C B JBL Studio 6 88LCR
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
The usual trade-off: JBL Studio 6 88LCR measures better, JBL Studio 665C costs about about 4x the price% less. Whether that gap is worth the money is the call only you can make - and in a normal room it is often smaller than the numbers suggest. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 58Hz anyway, which makes the cheaper JBL Studio 665C much easier to justify. In a large or open-plan room, JBL Studio 665C has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, JBL Studio 6 88LCR is the easier speaker to get right.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.