o scope gain setting

[ncc74656 2]

i have a 2nd post similar to this but not as on point so ive made this one to nail down some questions and make things more searchable in the future.

coworker was setting gains on an amp the other day and what he was doing got me thinking. if you follow mecp and set gain off a 40hz tone wouldn't the power output of that amp change drastically if the box were tuned to say 29hz or 55hz (something 1/2 or more octave above/below the frequency you are generating? or transversely if the box were tuned at 40hz...) the thermal handling of both amp and sub (assuming that's one thing you do such a procedure to keep in check) would change drastically while playing music. so wouldn't you have to select a (few) particular frequencies to run this o scope test on in order to be at all effective in such a manor? rather than a generic 40hz tone?

 

second is source of tone: ive always been of the school of thought that you use customers music and sources when setting up their radio, so you can hear the distortion the customer will be putting out and you can (maybe) prevent him smoking his subs/speakers by turning shit down and epoxying over the gain/bass boost controls. however the coworker was using Bluetooth to a customers boss radio off a 50hz youtube video for his test tone... reguardless of what one is trying to accomplish here there is no way it could be accurate given the source, i don't know what kind of compression youtube would have at 50hz but I'm sure its pretty crap quality. i don't see any reason to have done this procedure, it was a total waste of time right?

 

you ought to be able to use a test tone and o scope to know what to total maximum output of your equipment from input to output is. so you can have a pretty good idea if your trying to give right up to the limit of thermal handling but not to the point of damage? this could be done with a voltage measurement and some math tho right? no scope needed?

i thought of another use that i have not done before while working on my engine over the weekend - i had a fueling issue caused by noise on a PWM sensor to the ECM and found/fixed this with my scope. one should be able to see interference down a wire run, say RCA's going too close to an EMI source or ac ripple going into an amps power section and with this you should be able to ensure maximum audio quality and know if you do or do not need more expensive/shielded rca's or more voltage on the rca's. again ive never seen nor heard of ANYONE using a scope this way in my shop or others in my area but i cant wrap my head around why not? any input there?

Edited March 19, 2018 by ncc74656

[Tirefryr 1,742]

The power output  changes with every frequency.  The tune of the enclosure does not affect the amplifier at all.  Well, back EMF, but we won't even begin to get into that.    You also speak of being near thermal limits, which is good thought, but don't forget mechanical.  Either one of these, or both, could spell doom.

 

I like that you're thinking here, but to what end does this stop?  You can scope every wire, every frequency, at every power level, and every magnitude, etc, and you're going to get a different result every time.    Also, the scope may show interference, or some other abnormalities, but if it's inaudible or causing no harm, what do you do then?  Your ears say everything if fine, but you saw something on a screen.  What does it truly mean?

I realize it's difficult to digest that everything you've been taught by "industry professionals" and all the marketing behind this stuff may be false, but just think . . . .   How did we ever set anything up before all these "tools" and information were available en masse?

[ncc74656 2]

i was thinking about concerts ive been to and i have never seen anyone using a scope to setup the stage, its always using the mics/instruments through the system and adjusting off the sound. got me thinking about all this more

[///M5 2,833]

Haha.  I was a sound engineer for 5 years.  Made gain adjustments in mid song ALL the time.  

[Notorious97200 339]

I can only understand the need of an o'scope for fine tuning in competitions.

But for my daily listenings habits, I don't need nothing to set the gain on my amps, except my ears and some music (or tone eventually).

If I feel it sounds bad, or weird, I turn it down.

Sorry for that speach, OP !

[Randal Johnson 544]

I learned a long time ago that an amplifier gain is not a volume control. If you want more volume and the amplifier you have doesn’t put out without jacking the gains, get a stronger amplifier. Simple.

[///M5 2,833]

While your intent with the comment was right Randal, it wasn't on topic as stated.  OP is confused at how to set the gain in the first place and while your comment is true that a gain knob is not a volume knob, he thinks he needs an oscope to find out where the baseline should be...that is completely pointless.

[Notorious97200 339]

On other forums or facebook pages, people swear by o'scope or all those s mdd -1 tools to set the gain. They say if you don't use those, you can't have it set right !

That is confusing if you don't know about car audio.
 

[///M5 2,833]

Average person on facebook is an idiot, so what do you expect?

[Randal Johnson 544]

What’s funny is that I’ve seen them use the dd-1. And all they do is turn gains down to a “tuneable” level which is where someone with audio common sense would set them in the first place. Same shit with an O-scope. sad really

[Abo raya 111 0]

In that case what is the right way to set the gain 

[Randal Johnson 544]

6 hours ago, Abo raya 111 said:

In that case what is the right way to set the gain 

Simple really. You HAVE to know what you’re doing. 

[ncc74656 2]

you know what ive been thinking about...   some how in the audio industry we have gotten to the point of selling a 400W amp for a 400W sub, always trying to match the sub to amp rms.  then we take the o scopes and meters to try and get max output from the amp with out any real consideration for voltage amps going to the voice coils.   way back when i worked with home audio we would sell amps that had head room, 150w amps with 80 or 100w speakers and we would set them up by playing music and some times using microphones to setup time alignment. we never had them maxed out tho, in car audio we are always trying to push distortion and max out power but i never did this in home audio. i also do not ever remember anyone talking about going from tv to receiver to speakers to measure things with scopes.

i think most of the blown subs i see at work are from pushing the subs past their thermal capacity because we always setup the equipment to operate at 100+% of its rated values.

Edited March 27, 2018 by ncc74656

[Abo raya 111 0]

Randal can you tell me exactly how to do it. Suppose i don't know what I am doing. I just want to know

[Randal Johnson 544]

34 minutes ago, Abo raya 111 said:

Randal can you tell me exactly how to do it. Suppose i don't know what I am doing. I just want to know

Nope. I know nothing about you in tha audio word and I have no plans to get trolled.

 Please use your search generator for info. Start your own topic and  Post up what you are working with and your specific questions and I’m sure you can get help on this forum. 

Hope you understand brother. Nothing personal.

[Randal Johnson 544]

Ok, after taking my own advice and doing some research on you, I found out that you’re a Zapco guy. Awesome, something to work with. Now after reading your post, I really don’t see where you would need help setting your gains brother. I’d like to see your setup.

[Abo raya 111 0]

Believe me iam not a troll at all. My previous knowledge that scope will do the jop but you guys do not agree and i want to learn the right way to do it. I consider my self a begginer that's why i joined this forum to learn. I always search before i ask but all i found is oscope and dd1 and by ear lool. Thanks randal and sorry if i came as troll because this is not me. 

[ncc74656 2]

in the industry and training you get, you are told you must use an oscope to ensure clean signal from your source and to match your gains to the input voltage. you also use this on the output of your amps to find max output. you can not setup a car audio system with out taking these steps.

i don't buy into this anymore, i don't know why this is taught but i do know that it does not prevent blown speakers, it does not ensure better quality audio by itself, and it seems a waste of time and money to buy the multi thousand dollar o scopes required for this

[Xrc6 0]

Whatever the case, outside of competing, I fail to see the point for turning audio in a car to rocket science. You're listening to music you enjoy while driving A to B and all the basic information from gauge of wire to buy to the use of fast rings is shoved in your face before you even enter your credit card info anyway . Why anyone would max out their volume and push every watt they can I don't give a crap to know but for whatever it's worth, I have a cheap $50 O-scope and 10x probes. Aside from the millions of other handy uses such a thing has,  I use -5 db 1000khz tone for fronts and -10 db 40hz tone for subs to use as a foundation to start with. Find the distortion level on my HU which becomes my max volume, set gains on amp then adjust by ear listening to my loudest music tracks. Top it off with a little time alignment, a sprinkle of EQ adjustment and ending it with a f***it by keeping my volume within moderate levels, loud enough to drown out traffic but not so loud that I can't hear EMS/Cop vehicles and turning it down when I"m at a stop light or in my neighborhood. Basically just common sense use of music listening without being a douschebag.

I further that by not showing off my system or telling anyone I have anything. I added Clark Synthesis tactile transducers attached to my front seats just to augment my subwoofer so I don't feel the need to push my subs so deep that everyone within sight can spot me out but I can reap the benefits of feeling it more with less SPL. The fewer people that know I have something expensive in my car, the longer I get to keep it because it's for my audio pleasure only. But it sounds really nice inside the car without having to reverse engineer sound waves and attempt to bend the laws of physics to achieve it.

[///M5 2,833]

3 hours ago, ncc74656 said:

in the industry and training you get, you are told you must use an oscope to ensure clean signal from your source and to match your gains to the input voltage. you also use this on the output of your amps to find max output. you can not setup a car audio system with out taking these steps.

i don't buy into this anymore, i don't know why this is taught but i do know that it does not prevent blown speakers, it does not ensure better quality audio by itself, and it seems a waste of time and money to buy the multi thousand dollar o scopes required for this

It is taught because the average installer doesn't have the capability to pass the GED.  Weakest link theory.  The alternative requires thinking and comprehension which no matter your capability in life should be tried at every possible moment.

[Randal Johnson 544]

8 hours ago, Abo raya 111 said:

Believe me iam not a troll at all. My previous knowledge that scope will do the jop but you guys do not agree and i want to learn the right way to do it. I consider my self a begginer that's why i joined this forum to learn. I always search before i ask but all i found is oscope and dd1 and by ear lool. Thanks randal and sorry if i came as troll because this is not me. 

I use a Zero bit track and my ears (and a small screwdriver of course) to tune my gear. Listen for the hisssssss ...... 

works every time.

[Randal Johnson 544]

8 hours ago, ncc74656 said:

you can not setup a car audio system with out taking these steps.

Listen to your system. Learn and train your ears for a FLAT EQ. Learn left and right separation, stage and image, and most of all power, dynamics, and headroom.

your system will tell you where everything thing needs to be set. 

Look for the Chesky Records Disc Sampler to use for your test and tune. Learn it, live it, and know what you are doing. 

People say that’s cool to have a loud and clear system, but they trip the fuck out when they actually hear what a real dynamic, well tuned system sounds like.

Own that shit bro !!!

Edited March 28, 2018 by Randal Johnson

[Tirefryr 1,742]

17 hours ago, Xrc6 said:

Whatever the case, outside of competing, I fail to see the point for turning audio in a car to rocket science.

 

 

You sir have won the car audio internet today! 

[Abo raya 111 0]

Randal that's the first time i heared about that. Thanks for the input 

[Randal Johnson 544]

49 minutes ago, Abo raya 111 said:

Randal that's the first time i heared about that. Thanks for the input 

No Problem