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Limiter / Protection for HiFI?

Lambda

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In the PA and and professional speaker world it is common to have various sorts of limiter to protect the speakers (and listeners)
Different speakers (frequency ranges) have different power rating Usually Lowe frequency has the highest power handling.

So it would make sense to have Per frequency range RMS as well as Peak limiting to avoid "over excursion" "Mechanical Peak over power" and "RMS over power from Thermal effects".
Lots of "smart speakers" do something Like this by automatically reducing gain or only low frequency gain.
Lots of Active monitor speaker have also some sort limiter and automatic gain reduction to allow peaks to pass but limit long contentious tones.

Is there something like this in the HIFI world?
Ideally you would of cause never need this... but to make the system "idiot" proof?

On way would be to have Extremely overpowered speakers that can Handel what ever the amplifier can output indifferently at every frequency
And an Amplifier with so little gain that it would never clip.
 

Kal Rubinson

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Is there something like this in the HIFI world?
It is built into most active systems. It can also be done in software but it is really not necessary. In general, the user/operator is the listener and is not isolated from the actual sound. Human feedback does the job.
Ideally you would of cause never need this... but to make the system "idiot" proof?
Don't let idiots use your system.
On way would be to have Extremely overpowered speakers that can Handel what ever the amplifier can output indifferently at every frequency
And an Amplifier with so little gain that it would never clip.
Sure but, in practice, only misuse is a problem.
 
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Lambda

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It can be done in software
Sure it can but is there some software?

Human feedback does the job.
I'dont think i fast enough to turn down the volume in cases some digital stream decides to send 0dBFS 4Khz Square wave...
Wen i have my volume all the way up because i was listening to verry low and dynamic track before.
If the source is youtube, twitch, soundclud,mixcloud, vimeo... or something you cant be sure what your getting is "save"

Don't let idiots use your system.
But i'm an Idiot...
 

DVDdoug

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but to make the system "idiot" proof?
That's rather tricky. The best solution is to keep teenagers & drunk people away from the volume control! :D

On way would be to have Extremely overpowered speakers
Yes, speakers with a high power rating. Over-powering is what you're trying to avoid. ;) Or, an under-powered amplifier.

And an Amplifier with so little gain that it would never clip.
Limiting the gain doesn't help if a hot-loud signal gets fed-into the amplifier. You have to limit the amplifier output.
 
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Lambda

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That's rather tricky. The best solution is to keep teenagers & drunk people away from the volume control!
This is not relay the question here. What if i’m a drunk teenager?

Commercial Products have solved this problem. Lots of Powered speaker you cant relay kill no matter what input signal you send them.
(well within reasonable limits... of cause high voltage would kill the input)
under-powered amplifier.
An extremely under-powered amplifier. is an easy way to keep everything save. but you don't have mush power.

Limiting the gain doesn't help if a hot-loud signal gets fed-into the amplifier. You have to limit the amplifier output.
The input signal for me Would be a DAC so it is limited
 

maverickronin

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The quick and dirty way is to find a pro sound style DSP box which has a limiter function and then calculate the maximum output to set on it based on your system's gain staging and whatever sounds too loud to you. Off the top of my head, something like the Behringer DEQ2496 could probably do it.

If you want to make it really bulletproof, you'd need something with different limits at different frequencies to make sure no signal can blow your tweeter.

This is kind of a PITA to do after the fact in an existing system.
 

brimble

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Good topic.

I started worrying about this very recently.

My solution, which works fine so far, is to make sure there are two volume controls in my system. The first one (in my DAC) is set low enough that even if I turn the second one (in my amp) all the way up the output won't be enough to blow holes in my expensive electrostatics.

Last time I was shopping for an amplifier (side note - it arrived just today and is lovely - a Teac A-H500i) I deliberately got one that doesn't have a built-in DAC, to make sure that I wasn't tempted to leave my external DAC out of the signal chain and lose my volume limiter.
 

restorer-john

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In my experience, there is no product that is totally "idiot proof". And that's the way it should be! Keep the idiots away from HiFi. Let them ride jet-skis in swimming pools, shopping trolleys down hills and trail-bikes up escalators. That's their area of expertise.

If you want to turn it up to 11, drink vodka shots all night and play AC/DC into a 6.5" 2 way bookshelf speaker- you deserve all the smoke and flames that come from that idiotic behaviour.
 

Doodski

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Teac A-H500i
Sweet looking amp!
s-l1600.jpg
 
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Lambda

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In my experience, there is no product that is totally "idiot proof".
Try braking Sonos speaker or Boses or JBL, Bluetooth speaker like this....
Or any modern products that has to provide Warranty and is marketed at idiots.

And that's the way it should be
Not in my Design philosophy...
And there are not manny if at all consumer products that will almost instantly physically brake if you enter the wrong settings.
 

Frgirard

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In the PA and and professional speaker world it is common to have various sorts of limiter to protect the speakers (and listeners)
Different speakers (frequency ranges) have different power rating Usually Lowe frequency has the highest power handling.

So it would make sense to have Per frequency range RMS as well as Peak limiting to avoid "over excursion" "Mechanical Peak over power" and "RMS over power from Thermal effects".
Lots of "smart speakers" do something Like this by automatically reducing gain or only low frequency gain.
Lots of Active monitor speaker have also some sort limiter and automatic gain reduction to allow peaks to pass but limit long contentious tones.

Is there something like this in the HIFI world?
Ideally you would of cause never need this... but to make the system "idiot" proof?

On way would be to have Extremely overpowered speakers that can Handel what ever the amplifier can output indifferently at every frequency
And an Amplifier with so little gain that it would never clip.
If you are clumsy or playful at the one who kills the watt, I recommend it. I know someone who blew up their b & w diamond's tweeter. Another destroyed the tweeters of his yamaha nsx 1000.
 

NTK

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Here is a link to the setup guide of the LevelMAX limiter in the Crown I-Tech 5000HD amp.

As can be seen, to properly setup the peak limiter parameters in not a job for a typical idiot. You need to enter parameters on the instantaneous voltage limits, short term power limits, long term thermal limits, and their time constants. Otherwise, you are either not utilizing the speakers' full capabilities, or the speakers aren't fully protected, or both. Below is an example list of parameters for the JBL Pro speakers they usually drive.

levelmax.PNG


It is highly unlikely that you can get these info for any consumer speakers. The lowest common denominator approach will be to get a 2 W SET amp.
 
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Lambda

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You need to enter parameters on the instantaneous voltage limits, short term power limits, long term thermal limits, and their time constants. Otherwise, you are either not utilizing the speakers' full capabilities, or the speakers aren't fully protected, or both. Below is an example list of parameters for the JBL Pro speakers they usually drive.
My approach would be to turn up the volume as loud as i like it and as loud as i would trust my speakers to play with out getting damaged.
And then using a wide section of "normal" music as test signal adjusting the level for each protection parameter so they almost kick in.

I’m not worried about the limiter softly limiting and gradually limiting without distortion.
I see it more as an "emergency shut off" it shuld never kick in during normal operation and so if it doses its ok if this not as gradually as possible and if the releases time could be lower.
 

gene_stl

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My approach would be to turn up the volume as loud as i like it and as loud as i would trust my speakers to play with out getting damaged.
And then using a wide section of "normal" music as test signal adjusting the level for each protection parameter so they almost kick in.

I’m not worried about the limiter softly limiting and gradually limiting without distortion.
I see it more as an "emergency shut off" it shuld never kick in during normal operation and so if it doses its ok if this not as gradually as possible and if the releases time could be lower.
If the above is your use case put some inline fuse holders in series with the speakers. Start out with lower fuse values and if they pop , increment them upwards.

The problem with idiot proofing stuff is you always underestimate the idiots.
At my old place you had to go down to the basement to turn on the power amps. One morning my I came into the living room to find my nieces boyfriend attempting to turn on the stereo.(they were guests) I asked him if he had a license to drive that thing. That went over his head. Fortunately I knew he would have no luck starting the system. If I had found him operating it without arthurization it would have been an issue.
"A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools." D. Adams

At my new/current digs it will all be in one room and I may put a key switch or other idiot foiling system into place. even though I don't expect many idiots. (was the case at the old place too. the idiot in question was an MD)

The Crown DSP input amplifiers have thermal history modeling which can be programmed into their limiters. The DSP system introduces about one millisecond of latency. I think others have thermal modeling too. iirc you tell the software , the rms and program ratings for the driver and it sets the limiting for you.
 
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Lambda

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If the above is your use case put some inline fuse holders in series with the speakers. Start out with lower fuse values and if they pop , increment them upwards.
I don't think this is gonna work.

since the max current is very frequency dependent.
At very low frequency over excursion damage will happen before Thermal damage.
At low frequency there is a lot of power handling so i would need high current and slow fusses
At very high frequency the tweeter gets damaged with way less current then the bass driver.

But behind the crossover this can work an JBL did something similar
750-SK3_detail2.jpg.auto.webp
 

gene_stl

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That of course is a tungsten lamp whose resistance characteristics vary with their thermal history. This is why tungsten lamps always burn out in a flash when you switch them on. When they are cold their resistance is low and when they are hot it is higher. This is called a "tungsten load characteristic" in design of electrical wiring. Of course it is not seen so much anymore. They pop when the switch closes at the peak voltage which causes a giant current rush that explodes thinning filaments. Tungsten and halogen lamps last longer when operated on dimmers that have "zero crossing detection". They don't start feeding current until a zero crossing so the current increases sinusoidally. Or a dimmer that ratchets the current up slowly.

If you are worried about the differences in characteristics between wooofers and tweeeters then fuse them individually.
I don't think you have to worry much about excursion damage unless you are really pounding the speakers. Ocassionally hitting the stops wont probably hurt things. It is hitting the stops when the voice coil is hot already which causes the voice coil to unwind. Or go up in smoke.

A tungsten lamp in series reduces damping factor which I would find unacceptable.
Tweeters get damaged when amps clip and the crossover routes high frequency components to the tweeter.

If you have these concerns your system might be under designed. These concerns are also things which recommend multi amping.
Makes me wonder 1) How big is your listening room ? 2) How loud to you normally listen? 3) What kind of program material are we taking about?
Perhaps you need some high output headphones. You shouldn't really need to operate in the voice coil unwind, surround rip, voice coil fire zone.

Why do you think you have more power handling at low frequency? Why do you think you will get excursion damage before thermal damage?
I would never use a sloblo fuse on speakers. The damage happens almost instantly. You want an undersized fuse so that the voice coil does not protect the fuse. If it pops you can always upsize the replacement.
 
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