It’s always a hoot when the guy making the most noise in the thread is the one who doesn’t have a clue what he’s talking about. I guess anyone who can Google to find the SPL of a vacuum cleaner is automatically an expert.
Really? Anything between 0 and 70 dB? If you had even a vague idea of what you’re talking about, you’d know that the background noise level of a recording studio is ~25 dB. Have you ever been in a recording studio? You really think you can operate a PA system lower than the background noise level in a recording studio?
60 dB, huh? You really think you can do a gig with your stage amp at 60 dB? Well, if you can operate a PA system lower than 25 dB, maybe you can.
Obviously, you’re the one who would have been smart to keep quiet about that. You don’t even have a SLM, do you? Never even used one, have you?
If you knew a wit about the physics of sound you’d know about the cumulative effect of multiple noise sources. Or didn’t you notice that when the restaurant fills up with patrons the din of conversation tends to get really loud?
In your dreams. Most likely the noise level in the room from all the chatting patrons was averaging well over 80 dB. If your rig was staying below that level out where the tables were (let’s say at ~20 ft. away), that means you were pushing probably 90 dB where you standing (assuming 2-3 ft. away from it).
If you knew anything about the cumulative effect of multiple sound sources, you’d know that each additional noise source adds about 3 dB (assuming all sources are calibrated to a reference SPL). The distance a SPL measurement is taken at matters as well; fortunately that's to our advantage. If the allowable SPL is 70 dB measured at ~20 ft, your rig would be measuring ~79-80 dB where you’re standing, probably 2-3 ft away from it. No problem, you can play at 80 dB and maintain 70 dB to the patrons, right?
No way. Let’s take the case of an imaginary band with three vocalists, two guitarists, bass and drums. If everyone in the band is generating 80 dB (measured up close to them), the sound level out at the tables (20 ft. away) is going to be something like 88 dB on passages where everyone is playing at the same time.
In order for our imaginary band’s total output not to exceed 70 dB out in the room, no single player or vocalist would be able to generate more than 62 dB (measured up close). Since I’m sure you have no clue how low that is, it’s about the same as a faucet running water in a sink.
And being bass players we have the added issue of the ear’s poor sensitivity of low frequencies at low SPL. I assume you’ve never heard of the Fletcher-Munson curves, so I’ll get you up to speed. Since the ear has poor sensitivity to low frequencies, that means the bass has to be turned up in order for it to be heard in a proper blend/mix with the rest of the instruments. That in turn means if the sound police are measuring the SPL of our imaginary band with C-weighting, you’ll easily exceed your 62 dB restriction. Oops. Hope your amp has a headphonejack.
I’ll let you do your own research to figure out the difference between C- and A-weighted SPL measurements and how it impacts the bass in music production or reproduction.
Regards,
Wayne A. Pflughaupt
Pedulla Club #45
Administrator, Tobias Club
Big Cabs Club #23
Pedulla Club #45
Wayne, you say you're an expert and you can't figure out how to turn a volume knob down????
Is that really your position? You're really stating that its impossible to turn a pa system down to any arbitrary level between its max output and zero? Really? That's laughable.
You've got a number of knobs to work with throughout the various gain stages, but if you are struggling with the knob concept, I guess gain stages are best saved for later.
So Mr. Expert, tell us what YOU think is the lowest you can turn an amp down to? How is it you can hit zero, but can't stop off anywhere between 0 and 70dB? I wonder where you'd be at if you started at an output of 100dB and turned the power amp attenuator down from the starting point 0dB (max) to -30dB.... I guess at that point if you pulled the PA main sliders down the PA wouldn't get any quieter? Is that how you think this stuff works?
Does the volume knob on my bass suddenly stop working once the amp is putting out 70dB of sound????? How do it know????
Hey, what DO all those numbers next to the little dB around the knob mean anyway??? You're the expert, school us. I'm sure the dB by the 0 can't possibly refer to decibels. School us, please, we want to know.
Not to burst your bubble, but F-M curves have been pretty common knowlege at least since I heard about them when I was a teenager and just getting into Hi-Fi stuff. Not rocket science. They've had "loudness" buttons to boost bass at low volumes on stereos to approximate a correction for that for at least 35 years since I bought my first stereo. I'm sure they go back even further, somehow I just bet they weren't discovered the day I started reading Stereo Review. Radio shack sells sound pressure meters, they're not secret military technology either.
But if you think it makes you sound like an expert to expound on them, go ahead.
Randy
