About 8 years ago, I started learning to play bass by playing in a Christian band on Friday or Saturday nights in our Church of Christ (believe it or not). I had purchased a used Carvin 2x10 and a GK MB200 amp. We played what our lead guitarist/lead singer called an "acoustic" set with his guitar, his voice and another guitar player going directly through a small Behringer PA that consisted of a mixer/amp and 2 speakers. I used my 2x10 and the drummer wasn't miked. It was fairly loud in the room we were "allowed" to lead a praise and worship hour in. A few months after we had begun, we were invited to play for a youth revival in a large school auditorium. That was my first experience performing where drums were all miked, both guitar players used their amps that were miked and a DI was used on my bass. I still had my 2x10 on stage behind me. All of us had a small monitor with a 12" woofer and horn. Apparently, the sound guy that had "volunteered" for this event had his monitor amp go out so he ran the monitors directly off the main mix amps. For many of you, that's enough said. For those that haven't experienced this, the woofers in the monitors were flapping the entire show from the kick drum (and me). I couldn't hear my bass from the monitors AT ALL, and not much of anything else. I cranked up my amp on my 2x10 to try to hear, and I pretty much trashed the woofers in my 2x10 that day. From what I'm told, we sounded pretty good to the audience, but I couldn't even enjoy playing much less worship because I was so mad the entire hour we played. That was the first time I had ever played that I REALLY couldn't hear myself so I was very unsure about my playing. After that, I decided I would always be prepared!
I acquired quite a bit of equipment now, and I try to have more than needed because like others have said, you can always turn down; but as I've experienced, you can't always get enough. I almost always tell the sound guy not to put my bass in the monitors. I can take care of me and the drummer hearing bass on stage. I've noticed many sound companies save their money on their monitors so my "solution" works.
Here is my arsenal of amps and cabs: GK MB200, Aguilar TH500, Sansamp RBI, Peavey IPR 3000 DSP, Behringer NU3000DSP, Carvin 2x10 with replacement Eminence BP102 woofers, Markbass 102P, my custom made 2 ft3 box tuned to 37 Hz with a Faital Pro 12PR300A woofer, Trace Elliott 15, Seismic Audio 2x15, Ampeg SVT18, and my custom made 8 ft3 box tuned to 30 Hz with a Selenium 18SWS800 woofer. And I'm always wanting more!!! Oh, I forgot to mention I play a 5-string, and I LIKE to hear/feel that low B 30 Hz fundamental, not just the 2nd harmonic and overtones. Also, when you played with a lead guitar player/lead singer that is deaf in one ear...let's just say I have to use earplug in practice or indoor performances, and I never need my own monitor because I can hear everything just fine from his 10-15' away!
I've attached pics of my custom cabs.