What's to chat about?

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Seth
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Re: What's to chat about?

#886 Post by Seth » Fri May 07, 2021 12:37 am

I was wrong.
I think.

Been scratching my head on this quandary. I put together a spreadsheet and things weren't adding up the way I thought they would/should. An SM58 microphone's sensitivity is rated "-54.5dBV/Pa" (1.85mV output while receiving 1kHz sine at 94dB SPL)

But when I calculated -54.5dB of 1 volt I was getting a value that was very close to twice the 1.85mV figure.

Search, read, search, read, search, read...

Then I came across this equation: dB = 20log(V1/V2) = 10log(P1/P2)

I noticed that the equations were different for calculating Voltage change from dB than it is for calculating power (watts) or SPL dB, in that the different equations account for and equalize the figures.

The relationship between +/-dB on a channel fader/attenuator or master fader are in fact 1:1 with speaker output. Which makes sense, because I didn't think I was hearing a 10dB change with 5dB of fader adjustment.

Which also put's to rest the quandary about the EQ too.

So, that's all settled, I guess.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

Bruce Weldy
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Re: What's to chat about?

#887 Post by Bruce Weldy » Sat May 15, 2021 3:55 pm

I've got something to chat about......This topic has come up a couple of times now at two different venues.

There's a venue that I mix in occasionally. It's an outdoor pavilion - open on all sides. It's got a QSC KLA system in it. Three boxes hung per side along with two subs per side. At one point, the owner decided to add a center fill at the stage along with a center fill further back and three additional boxes per side pointing out of the pavilion to cover the folks sitting outside of the pavilion. The reason for all the additional speakers was that they have Alex Meixner (acid polka player - really good show) play there a couple of times a year and it's a ticketed event. There were complaints that people couldn't hear with just the stage PA - thus, the extra speakers.

After all of this was installed, I went to mix a band in there and my first move was to utilize the scene on the speaker processor that only included the stage boxes. The owner nixed it and pretty much said, "I bought 'em, we are using 'em." Tried to explain that people who want it quieter will sit in the back, but that all the surround speakers were going to make it too loud.....he wasn't listening to me, so they stayed on for the next three years......and the volume complaints were ongoing to the point that it was frustrating for me and the bands being constantly told to turn down.

Fast forward to now....... the owner died last month. There were several problems with the PA - broken Powercons on the subs, non-working subs, and of course the issues with using the same scene for everything. The GM asked me to come talk to him about it all. Finally I had someone who would listen. I explained that the surrounds don't work with a "local band" where a good part of their crowd was only there to eat (should've mentioned - it's a restaurant first and foremost with inside, sorta' inside in the beer garden, and outside with the pavilion).

The volume of the PA from a mix position close to the stage obviously has to take into account the stage volume in order to get a good balance. However, at the back of the Pavilion, the fill speakers were hammering everyone with un-balanced sound as they were too far from the stage to get the mix of stage volume and the subs. Thus, they were getting a really crappy mix right in the face.

I went in last week and went through the different scenes with two of the managers......got rid of the surrounds and the rear center fill. They immediately heard the difference and think it will really help with the complaints. While I was there, another employee showed up and tried to explain to me that you have to have the surrounds so that you can keep the volume of the stage hangs lower.......and this is the issue I'm writing about.

What he said is absolutely FALSE when doing live sound. Recorded music - sure.....but then, why would you need a big PA up front? Just put the same speakers all over the place, set 'em to the same volume and there ya' go.....equal sound.

The Main PA has to be balanced with the stage volume in all but the biggest and loudest venues. Any surround or delay speakers should only be there as a supplement to the main PA, but not try to be as loud as the main PA.

I had this same conversation with another venue owner that has an inside space (about two blocks away from the place above). It took awhile to get him to understand that adding speakers all over the room won't let you turn down the main PA. Now that he's onboard with that notion, we are about to replace the old Driverack with a Driverack 260 that will let us add the two delay speakers to his room in order to gently supplement the volume, but not try to "level" the room by turning down the main PA. As with the other venue, we'll have separate settings on the processor based on what kind of show is happening. A big, loud show will get everything, while the smaller regular show will utilize the main PA only.

Anyway, that's a lot of typing just to say - adding more speakers WILL NOT let you turn down the main PA.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Grant Bunter
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Re: What's to chat about?

#888 Post by Grant Bunter » Sat May 15, 2021 4:33 pm

Yep

Sometimes you just can't tell people anything at all.
Such as "sound falls off at a rate of xdB every doubling of distance".

My current favourite is "I want to sit near the entertainment, but it's too loud. Can you tell the Sound guy to turn it down."
Sure Sir/Maam, but then the people further back won't be able to hear. "Not my problem, it's too loud".

Therein lies the argument for delay stacks, surrounds, whatever. Throw in a sales opportunity and it's then set in stone.

Doesn't necessarily mean it's the best solution though. The best solution would be for those that don't like the volume too loud to not sit near the PA.
Reminds me of the Funeral notice I saw the other day.
"We wish to advise all of the sad demise of common sense"...
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Bruce Weldy
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Re: What's to chat about?

#889 Post by Bruce Weldy » Sat May 15, 2021 5:13 pm

Grant Bunter wrote:
Sat May 15, 2021 4:33 pm

"We wish to advise all of the sad demise of common sense"...
Ha!

I just talked to my buddy, Mike, who mixed in the second venue I was talking about last night. This venue has a big open spot for the stage area, a bar area and a counter back by the kitchen. A guy came up to him who was sitting at the counter by the kitchen - pretty much as far as you could get from the stage - and wanted him to turn it up. Mike told him it would be too loud for the people in the actual listening area - the guy didn't believe him. So, Mike asked him if he was in the sound business. The guy said he was in the concrete business. Mike explained that he WAS in the sound business and understood the physics of sound. :bash:

The guy finally backed off. Of course, it doesn't hurt that Mike is 6'6" and about 280 pounds. :mrgreen:

Then a lady came up and said she couldn't hear the girl who was singing. The girl was all over the place on the mic.... close, far away, on the side. She had no idea of how to work a mic. He just sighed and told the lady that he'd work on it. :roll:

Yeah, common sense is not in play in the music world.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Bruce Weldy
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Re: What's to chat about?

#890 Post by Bruce Weldy » Sat May 15, 2021 5:15 pm

And you know.....it ain't just the audience.......hell, most of the venue owners/managers and a good portion of the musicians don't understand anything about sound either.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Seth
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Re: What's to chat about?

#891 Post by Seth » Sun May 16, 2021 2:33 am

Bruce Weldy wrote:
Sat May 15, 2021 5:15 pm
And you know.....it ain't just the audience.......hell, most of the venue owners/managers and a good portion of the musicians don't understand anything about sound either.
The musician's significant others... they know EVERYTHING about sound. LOL
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

Bruce Weldy
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Re: What's to chat about?

#892 Post by Bruce Weldy » Sun May 16, 2021 8:37 am

Seth wrote:
Sun May 16, 2021 2:33 am
Bruce Weldy wrote:
Sat May 15, 2021 5:15 pm
And you know.....it ain't just the audience.......hell, most of the venue owners/managers and a good portion of the musicians don't understand anything about sound either.
The musician's significant others... they know EVERYTHING about sound. LOL
YEP!!!

Although, after 44 years of following me around to playing gigs and sound gigs - if my wife tells me what's wrong with the mix while I'm on stage - I listen.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Bill Fitzmaurice
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Re: What's to chat about?

#893 Post by Bill Fitzmaurice » Sun May 16, 2021 9:52 am

Bruce Weldy wrote:
Sat May 15, 2021 5:15 pm
And you know.....it ain't just the audience.......hell, most of the venue owners/managers and a good portion of the musicians don't understand anything about sound either.
More than a few FOH guys don't either. They got the job as a friend of the band willing to lug gear for beer, and never actually learned the craft after the band became successful. :wall:

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Re: What's to chat about?

#894 Post by NukePooch » Tue May 25, 2021 5:40 pm

Seth wrote:
Sun May 16, 2021 2:33 am
Bruce Weldy wrote:
Sat May 15, 2021 5:15 pm
And you know.....it ain't just the audience.......hell, most of the venue owners/managers and a good portion of the musicians don't understand anything about sound either.
The musician's significant others... they know EVERYTHING about sound. LOL

You'll be fine if you just make sure to mix it in Dubly.

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Re: What's to chat about?

#895 Post by Seth » Thu May 27, 2021 12:23 pm

NukePooch wrote:
Tue May 25, 2021 5:40 pm
You'll be fine if you just make sure to mix it in Dubly.
Hahaha... now that's what I was getting at. The know it all GF's/Wives/SO's... Granted, in many cases they've heard the band in many venues and know what the band "should sound like", or usually sounds like. But when your 15-20 seconds into the first song without a soundcheck and they're gabbing over your shoulder about everything that's not quite right and telling the sound tech what needs to be done and how to do it... I haven't done a ton of work in multi member band mixing and it's only happened to me a couple times. The first time I got a little irked, which I try to take responsibility for. So, later I thought a little bit about more effective ways to deal with that sort of criticism/situation. Now, I compliment them on their keen observation and tell them they really have a good ear for this stuff.

Obviously, in Bruce's case, he's a knowledgeable guy and his wife is likely to know a thing or two. Not the case with anyone I've worked with.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

Bruce Weldy
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Re: What's to chat about?

#896 Post by Bruce Weldy » Thu May 27, 2021 3:36 pm

One thing I do after a few songs is to go ask the wives/girlfriend what they think. I'm also not afraid to ask other sound guys or musicians hanging around this question, "What would you change in the mix?" Sometimes, I get really good feedback from them. I don't really have an ego in mixing - bottom line is that typically the crowd either likes it or they don't......they don't know why.

But, like anyone, I hate the guy that comes up 15 seconds into the first song and give you some crap like - uhhh, you need some more compressor on the kick drum or ......can you cut a little 12k from the acoustic? Those are the ones I just ignore.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Seth
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Re: What's to chat about?

#897 Post by Seth » Wed Jun 02, 2021 12:58 pm

Been a little slow around here, thought I might share a couple easy calculations for you guys to play with.

To calculate the resultant power (watts) after 1dB increase multiply the initial figure by 1.2589. For a 1dB decrease, divide by 1.2589.

Example: How much power will it take to get a 1db gain if you're running 500 watts? 500 x 1.2589 = 629.45

To calculate 2dB you can just run that equation a second time, 629.45 x 1.2589 = 792.41. Or, if you know you want to know what 2dB (or any number of dB) will be, the formula is simply 1.2589 to the power of the number of dB you wish to calculate times the initial power figure (or the initial power figure divided by the product of 1.2589 ^ dB to calculate a reduction).

1.2589^2= 1.5848 x 500 = 792.41

Any number of dB... four and a half dB more than 500watts? (1.2589^4.5)x500= 1409 watts to achieve the 4.5dB gain.



The impedances of these cabs are similar enough for loose comparison. The two traces look to be about 6.5dB apart at 40Hz. If the T60 is on the limiter (800watts) at 40Hz, how much power would the JBL require to match it's output? 1.2589^6.5 = 4.4662 x 800w = 3573 watts for the 2x18 JBL to match the 2x12 T60's output at 800 watts (at that specific frequency).
Last edited by Seth on Wed Jun 02, 2021 4:05 pm, edited 3 times in total.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Seth
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Re: What's to chat about?

#898 Post by Seth » Wed Jun 02, 2021 1:20 pm

Another easy calculation. dB is logarithmic. So, it's pretty easy to calculate the dB increase of a particular power figure. Using a scientific calculator, or in windows calculator click the three bars (menu) on the top left and select scientific.

Enter a power number, press "LOG", then multiply by 10. The product is the increase in dB above 1 watt sensitivity.

So, if you know the sensitivity at 1 watt and you want to know what the SPL would be with a specific input power, this is your tool.

104dB average sensitivity at 150 watts input? 150 LOG x 10 = 21.76dB increase. 104 + 21.76 = 125.76 (126dB)

Easy peezy.

I know it's easy enough to just google or use an on line calculator. But, now you know how they work.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Seth
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Re: What's to chat about?

#899 Post by Seth » Wed Jun 02, 2021 1:24 pm

Any takers on an old school "word problem"? :mrgreen:


How much power would it take a speaker with 98dB average sensitivity to match the output of a speaker with a 102dB average on 125watts?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Tom Smit
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Re: What's to chat about?

#900 Post by Tom Smit » Wed Jun 02, 2021 9:56 pm

Seth, maybe I'll try later. I tried in Ubuntu but had a result of "malformed expression".
TomS

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