Suggestion for volume values - change to 1-100% to make it layperson friendly and less blown speakers

I have heard recently of a lot more blown speakers for proffie users. And I would like to make a change in an attempt to prevent that.

Proffie os uses a volume value range of 0-3000 for the config. I suggest that its switched to a range of 0-150. So it makes more sense to a layperson working on a config. 0- 100% this scale can be multiplied by 20 in the code so that 1= 20, 100=2000, 150 = 3000. This would encourage users to stay in a zone of under 2000. It would be easy enough to handle in the code. just be volume times 20. where ever the volume int is called upon.

So while you can go up to 150% its highly encouraged to stay at 100% for the max level.

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It’s an interesting idea.
I’ve avoided making claims about what a “safe volume” is because I don’t actually know, and the 3000 max isn’t actually a max, it’s just a value where I’m fairly certain that it’s going to sound bad if you go higher.

The origin of the volume calculation in ProffieOS is actually in the dynamic compressor. When I wrote that code, I ended up with a multiplication in it, sort of like:

output sample = \frac{input sample * volume}{\sqrt{\sum{|input samples|}}}

The range of this volume is basically determined by this equation, which is why it ended up the way it did. Initially we started with volumes around 1000, and people have been experimenting with higher and higher volumes ever since.

If the volume is really high, what tends to happen is clipping. The output sample has a min/max of +/- 32768, and if you try to go beyond that, you just get 32768. A little clipping doesn’t matter. A lot of clipping alters the sound significantly, which can be good or bad depending on what you prefer.

Now, proffieboards have a 3 watt amplifier. However, it should be noted that those three watts are calculated on a sine wave with a 1% THD (total harmonic distortion) at 5 volts, with a 4 ohm speaker. 1% THD means that there is a very small amount of clipping going on, so the sine wave basically goes to +/- 32768.

However, things gets complicated…

  • Proffieboards use 5.1 volts instead of 5 volts, which would result in ~3.25 watts of output.
  • People don’t always use 4 ohm speakers. Speaker ohms vary over frequencies and are seldom well documented.
  • If you output a square wave instead of a sine wave, the total amount of energy output doubles to 6.5 watts.
  • The dynamic compressor (outlined above) creates a non-obvious relationship between the waveform and how many watts are being output.

Now, when there comes to speaker-killing, there are two distinct ways to kill a speaker (using an amplifier):

  1. heating/frying the magnet coil
  2. shake it apart

The first one is generally caused by putting too much wattage into the speaker. However, there is an additional detail that complicates things: The Proffieboard uses a class D amplifier. Class D amplifiers don’t actually output analog signals. Instead, they output very fast digital signals. The amplifier used on Proffieboards output a 400kHz PWM signal and relies on the coil in the speaker to act as a filter to smooth things out. It does this because of efficiency. A regular analog amplifier heats up a fair amount because of acting like a variable resistor, letting just the right voltage out to the speaker at any given time, class D amplifiers don’t have that problem, but dumps that problem on the speaker coil instead. I don’t really know how much extra stress a class D amplifier puts on a speaker, but the energy that gets filtered out by the coil has to go somewhere…

In the case of “shaking things apart”, the problem isn’t so much about how much energy there is. It’s more about how steep the curves are, and sometimes, it’s about resonance. Steep curves in your audio means that the speaker membrane has to move fast, which means higher forces on the speaker, which means more chance of ripping it apart. Obviously steep curves at high volumes are worse than steep curves at low volumes, but I don’t have any math for any of this, so I don’t know how much. In some cases, particular frequencies are easier for the speaker to play because of resonance. It can be a nice thing, because it produces more sound, at least at that frequency, but it can also mean more stress on the speaker membrane. Possibly causing it to break.

Now, probably none of the stuff written above matters.
In practice, most of us are running our speakers far beyond what they were meant to handle, and we just keep some spare speakers around if they break. IF we managed to calculate safe volumes , in spite of the complications above, I suspect that they would be much lower than what people would actually want, which would take us right back to square one again.

As an alternative to all the math above, we could just sit down and do a bunch of speaker testing to establish limits. That would be time-consuming and somewhat expensive, and it would have to be done explicitly for each kind of speaker. (And it could be rendered useless if the manufacturer changes anything in their speaker construction.) It’s possible to do, but unlikely to actually happen I think.

Maybe the best we can do is to build some sort of database where people can enter what fonts, volume and speaker and if they have had any problems with distortion or dead speakers?

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Another thing to consider too, is now that proffie OS6 has a built in Frequency Filter, in theory one may be able to push the volume up ever so slightly if they set this filter to roll off lets say 150-200hz.

It always seems to be the low end is what first causes issues with blowing speakers or speaker cone distortion. Low end frequencies are generally not easily “heard” (to the ear), but they are the most active in wave forms and cause the damage if over used.

All of that is fair. I agree that shaking apart the speaker is the cause. I was just trying to KISS the number. A Keep It Simple Silly. To put it into a range that makes sense 0 to 100%, and for those that may want to go to 11. You have upto 150% which there are very few use cases that can handle it. And while it may not be 100% safe for speakers 0-2000 in the current range is where most people have their volume set. Like you would not want to put a 1w speaker at 2000. It was a these numbers range are most often used. Heck if you want to play it safe you can do it by a mulitple of 15 instead of 20 so that it can go up to 200%

And a database would be also a good idea to understand what these speakers can handle or not handle. then we can get a better understanding of the ranges for each speaker.

Also we have learned recent some of the font makers like blue force have extra amplification gain in the font of -3 dBs. which we both know as ewww thats a lot.

For me that’s especially true. I have low end hearing loss. Low end does nothing for me. :laughing: :laughing:

Low end can be as much about feeling it as hearing it, if there’s enough…

i did play around with this exact thing.
i have a speaker that can handle more than double what the amp will supply and anythig over the 3000 threshold i encountered clipping from the amp.
so yes it does sound rather bad.

but to be fair running at 3000 volume is very load.