BillFitzmaurice.info

Your brain is masterful at compensating for what isn’t there but thinks should be. Sound. Color. Motion. Like if you walk down the scale on a guitar, then play the harmonic instead of the root at the bottom. Your brain helps you hear the note that never played.

Seth wrote: ↑Sat Apr 10, 2021 2:47 pm At what point do you guys stop perceiving the presence of a tone?

My headphones don't go down that low for me to discern. However, years back I tried out "Woofer CD" in my vehicle while listening to my 15" wide Autotuba, and found that I could hear the tone of 30 hz but not lower. The lower-than-30 hz notes were just sensations for me.

himhimself wrote: ↑Sat Apr 10, 2021 3:25 pm Your brains helps you hear the note that never played.

Absolutely true. I do this little walk down of the bass notes while playing a D chord. The last note before the Root D is the open low E string, but since I can't play the D, I wrap my thumb up there and hit the F# along with the D chord. You'd swear you hear the low D....even though it's not there.

The brain will definitely fill in what it expects......without the walk down, you probably wouldn't hear the low D, but the walk down sets you up to expect it.....so, it's there.

AntonZ wrote: ↑Sat Apr 10, 2021 1:47 pm A weird way of how I came to realize that this is indeed the case is when I completed my T18, many years ago. I had never heard this type of subwoofer before and these folded horns have a way of naturally filtering out harmonics. There probably still is some left, but much reduced in level compared to more common types of sub cab. I thought I knew what 40Hz sounded like before I completed my modest T18. After completion I knew that I had no idea what it actually sounded like. A clean and proper 40Hz is actually quite a bit lower than most people think it is.

A similar thing happens when people start designing their own bass cabs. They read on the internets that the fundamental frequency of a low E on bass guitar is 41Hz. So they want to build cabs that reproduce that 41Hz. What we typically hear when a bass guitar plays low E is mostly 82Hz and higher harmonics. Few systems other than properly big and well designed PA's in larger rooms will reproduce the real 41Hz with authority. Let alone the 31Hz of low B on a 5 or 6-string bass. And it doesn't even remotely sound like bass guitar at all.

A clean and proper 40Hz is absolutely luscious! I have my SLAP/T39 system tuned to a calculated (not measured) response curve that is roughly 15dB hotter at 40Hz than it is at 125Hz (except I have a 24dB high-pass set at 45Hz). Playing bass through that is a treat. Smooth, effortless, visceral bass. And even though the high pass is set at 45Hz, it puts 40Hz electronically down about -5dB and another -2dB or so acoustically (cab response), it's still 9-10dB hotter than the frequencies carried by the SLAP. That doesn't quite keep up with equal loudness, but the low E fundamental is indeed very apparent on this set-up.

We had a little jam session in the family room (about 40'x40') a few weeks back, I corner loaded the T39. There were a few nulls in the room, but fortunately none where the performers were. As jam sessions go, it wasn't very loud. No drummer, no guitar/bass amps. Everything DI'd. Just a reasonably elevated volume. The amplifier (Ashly NE1600PE, 450wpc) was indicating blips of -10dB on the channel that was driving the sub (sooo... what's that? 45 watts?). The heater vents and other fixtures were rattling with the lower notes. But again, not what I would consider loud. For the most part, I sat on the couch playing the part of Sound Tech and noodling a little bit on my little U-Bass (not plugged in) trying my best to follow along. One of the guys there primarily plays Double Bass, but was playing his guitar through a bass emulator pedal. It didn't sound half bad, actually. At the end of the session, everyone was packing up and the bass player asked if I could plug the U-Bass directly into the mixer. I did, and his eye's lit up when I played a little walking bass line. I'm sure it's largely due to the shock of such a sound coming from such a little instrument. But, the fundamentals come through so well with the T39 tuned the way I have it, that the air moves in the room and you can easily feel it, even at relatively low volume. I'm sure that had a larger impact on his surprise than he knows.

I agree, few systems will reproduce 40Hz with authority (or aren't tuned to do so). It's a real treat. Having experienced it, I find it a little saddening that commercial Bass cabs don't reproduce the fundamentals well. I get the practical reasons not to. But, still... it's such a huge benefit to the physically perceived experience of listening, to have those fundamentals faithfully represented, or even embellished.

Grant Bunter wrote: ↑Fri Apr 09, 2021 4:26 pm No, it's sound travelling.
At the speed of sound.

It's the reason one might expect to see delay stacks.

Is there a component of reaction time as well, well, hard to know, the human mind is extraordinarily adaptive...

Yup, that's what I thought too. Pretty neat to see a visual representation of sound traveling. Not sure if you saw them in the video, but they were running delay stacks. Perhaps that's what had you mention them.

Over in his SLA build thread, Bruce said:

Bruce Weldy wrote: ↑Sat Apr 10, 2021 10:31 am Side note......seems like every time I have to mix on a powered system - someone has engaged the MIC button on the input instead of LINE. I guess because the MIC input is louder they think it's better.....but, it just distorts much quicker. Too many options in the hands of the un-educated is a bad thing. Did a show two nights ago where every monitor was switched to MIC. Another reason why I like an amp rack and not powered speakers for most applications.

I run and maintain an outdoor "install".

When the gear first turned up, it quickly became evident that pretty much every time the pair of PRX615's used for FOH were put away, the Mic/Line button would be pressed.

I didn't realise this for a few days, and someone mentioned it. I actually like the Mic setting better.
Why? It was warmer and smoother. Hmmm, how could this be?
So I went back to the response charts and noted the chart is flat. Hmmmm how can that be?

It occurred to me the only way that could be true was internal filtering. Much like so many self powered cabs have a live/jazz/recorded or whatever setting to "EQ" the cab, the Mic/Line button does the same thing, ie alters EQ and gain.

Discuss...

Grant Bunter wrote: ↑Mon Apr 12, 2021 4:26 pm Over in his SLA build thread, Bruce said:

Bruce Weldy wrote: ↑Sat Apr 10, 2021 10:31 am Side note......seems like every time I have to mix on a powered system - someone has engaged the MIC button on the input instead of LINE. I guess because the MIC input is louder they think it's better.....but, it just distorts much quicker. Too many options in the hands of the un-educated is a bad thing. Did a show two nights ago where every monitor was switched to MIC. Another reason why I like an amp rack and not powered speakers for most applications.

I run and maintain an outdoor "install".

When the gear first turned up, it quickly became evident that pretty much every time the pair of PRX615's used for FOH were put away, the Mic/Line button would be pressed.

I didn't realise this for a few days, and someone mentioned it. I actually like the Mic setting better.
Why? It was warmer and smoother. Hmmm, how could this be?
So I went back to the response charts and noted the chart is flat. Hmmmm how can that be?

It occurred to me the only way that could be true was internal filtering. Much like so many self powered cabs have a live/jazz/recorded or whatever setting to "EQ" the cab, the Mic/Line button does the same thing, ie alters EQ and gain.

Discuss...

At mic level, the signal would typically go through a pre-amp, wouldn't it? Perhaps it's the pre-amp that's changing the sound quality. I know Midas has been famous for the "warmness" of their pre-amps, which I wanna say I read somewhere had something to do with a third harmonic or something to that effect. Maybe you're hearing a similar effect?

Moved an off topic post I made in another thread to discuss here. The author of that post "moved" it back.

This is now a "deleted post"

Seth wrote: ↑Mon Apr 12, 2021 10:26 pm

Grant Bunter wrote: ↑Mon Apr 12, 2021 4:26 pm Over in his SLA build thread, Bruce said:

Bruce Weldy wrote: ↑Sat Apr 10, 2021 10:31 am Side note......seems like every time I have to mix on a powered system - someone has engaged the MIC button on the input instead of LINE. I guess because the MIC input is louder they think it's better.....but, it just distorts much quicker. Too many options in the hands of the un-educated is a bad thing. Did a show two nights ago where every monitor was switched to MIC. Another reason why I like an amp rack and not powered speakers for most applications.

I run and maintain an outdoor "install".

When the gear first turned up, it quickly became evident that pretty much every time the pair of PRX615's used for FOH were put away, the Mic/Line button would be pressed.

I didn't realise this for a few days, and someone mentioned it. I actually like the Mic setting better.
Why? It was warmer and smoother. Hmmm, how could this be?
So I went back to the response charts and noted the chart is flat. Hmmmm how can that be?

It occurred to me the only way that could be true was internal filtering. Much like so many self powered cabs have a live/jazz/recorded or whatever setting to "EQ" the cab, the Mic/Line button does the same thing, ie alters EQ and gain.

Discuss...

At mic level, the signal would typically go through a pre-amp, wouldn't it? Perhaps it's the pre-amp that's changing the sound quality. I know Midas has been famous for the "warmness" of their pre-amps, which I wanna say I read somewhere had something to do with a third harmonic or something to that effect. Maybe you're hearing a similar effect?

Bored last night, did a little more snooping on the pre-amp theory. Makes more and more sense, the more I look into it. Whacha think Grant? Do you think it could explain the difference in what you heard, or does it seem more like an actual different EQ profile for the different input settings?

Seth wrote: ↑Wed Apr 14, 2021 11:50 am
Bored last night, did a little more snooping on the pre-amp theory. Makes more and more sense, the more I look into it. Whacha think Grant? Do you think it could explain the difference in what you heard, or does it seem more like an actual different EQ profile for the different input settings?

Grant's asleep right now, so I'll chime in.

There is certainly a preamp in mixers to push up the gain for microphones. That's why there is an XLR connector that goes through the preamp and a TRS line in connection that bypasses the preamp.

I'm guessing it's somewhat the same for a powered speaker, although I doubt they are the good preamps that go in mixers.

The reason that using the MIC input setting probably sounds fuller is that it is LOUDER. Switch to LINE and turn it up - it should be about the same on a powered speaker. However, that increase in gain using the MIC setting is what will overdrive the front end of those powered speakers if you crank 'em up.

Thus, always run a line signal into a line input. Run a mic into a mic input. On a good mixer, you can get by with a line input running through a preamp (XLR) as those will typically be a much better preamp with the ability to control the gain, but always try to keep things where they belong. On older high-end mixers, you'd have a MIC/LINE switch so that you could use the XLR input for either one.

- This message is brought to you by the Old Geezer's Soundman Club.......however, the author is known to wire crossovers incorrectly - so take it all with a grain of salt.

In my experimenting, and it was just that, I would turn the master volume on the PRX down if using the mic setting, and up to the +4 setting if using line, so the volume seemed to be much the same.
I wasn't doing it for louder, so it must be preamp.
I didn't put an SPL meter over both volumes though, so I guess it's a qualitative volume estimate. Maybe I was wrong there...

Thought I'd bring this to the table for discussion...

Random thought for the day;
What is the correlation between dB attenuation on a channel or main fader on the mixer and output at the speaker? Is it 1:1?

I did a quick googling and it looks to me that attenuation dB is dB of volts. If that's the case, any increase or decrease on the board should be doubled in SPL at the speaker. A 3dB increase in voltage equates to a 6dB increase in power (watts)... +3dB on the board should be +6dB measured SPL.

Does that seem correct to you guys?


If it is correct, then what about EQ?

Hmmmm
(wish we had in emoji for stroking the chin or scratching the head)

Seth wrote: ↑Wed May 05, 2021 9:46 pm
Random thought for the day;
What is the correlation between dB attenuation on a channel or main fader on the mixer and output at the speaker? Is it 1:1?

Most guys just think about naked women......

Correlation would depend I would think, there's lots of variables.
eg input sensitivity setting on the amp if it's adjustable, output settings on say DSP or EQ, eg -10dB or +4dB (or is that -4 and +10, anyway, you get the picture). Unity on different mixers sometimes means different things in terms of a value. A channel strip fader at unity might suggest 0dB but it won't be if the gain is trimmed low. A single light in a strip on masters meters, like an LED bargraph, might have a 1-2dB differential before it moves up (or down) to the next light.

You would have to take all of those consideration into equation, then work it out.

Good quality user manuals should tell you;
An amps multiplier value in the output stage compared to input sensitivity.
What unity means on the mixer.
But we all know most manuals aren't that good.
-10 or +4 is a 14dB swing in itself, quite significant.
And so on.

mmmm naked women...

Grant Bunter wrote: ↑Thu May 06, 2021 3:50 am Correlation would depend I would think, there's lots of variables.
...
You would have to take all of those consideration into equation, then work it out.

I don't think any of that would change the relation of fader dB to dB SPL... would it? Obviously, it all relates to what actually comes out the loud end. But, for any setting, any gain structure, any preamp input gain... any signal path condition... the fader would/should be -dB (in volts) of any particular condition and speaker output should (unless I'm missing something) measure double any adjustments to the fader level.

Totally discussion worthy if you guys think that's off base.

But, if it's correct, is attenuation and gain in an Equalizer also in volts? If so, and we mirror a speakers native response curve to get a flat response (or calculate a desired response curve from the measured response curve)... would we actually be overshooting the desired result?

Bruce Weldy wrote: ↑Wed May 05, 2021 10:35 pm Most guys just think about naked women......

Grant Bunter wrote: ↑Thu May 06, 2021 3:50 am mmmm naked women...

I love that you married guys are (still) thinking in multiples