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Zoom F4 Limiters (& I guess, F8 Limiters)
Old 3rd February 2017
  #1
Zoom F4 Limiters (& I guess, F8 Limiters)

The Zoom F4 thread is so full of garbage that I figure that I needed to start another. SIGH!

In that other thread I stated that it appeared that all 4 channels pre's, A/D's, and Limiters are in one IC chip. And that I thought the limiters while digital adjusted the pre-amp gain. And that the design was such that over driving the A/D's seemed unlikely.

Anyway to cut to the chase, I asked a Zoom Rep on another forum about that. He confirmed that I was pretty much correct in my surmise. That the limiters knock down the analog gain in the pre-amp up to 10db. And while the recorder can clip with the limiters on it is unlikely if used sensibly.

It is kind of nice to be proven correct (grin).
Old 3rd February 2017
  #2
Gear Head
 

I really don't mean to offend, but I've never considered "pretty much correct" as proof (and I have no dog in this fight whatsoever), also, that "pretty much correct" would bear extra scrutiny when it is coming from someone who benefits from such an answer.
Old 3rd February 2017
  #3
Lives for gear
 

I'd be interested in some real-world experience of how this works in practice, esp re dialog with wide dynamic range (whisper>surprise shout) etc. Many things that work fine when things are going "sensibly" work less well in more chaotic and unpredictable situations. That said, we lived and dealt with the terrible audio input stages of video decks for years and years, and got away with it mostly. They were not in the same league as the F8 at all, and I see a lot of indie drama soundies driving F8s: would love to hear from them.
Old 3rd February 2017 | Show parent
  #4
Quote:
Originally Posted by pmsounds View Post
I really don't mean to offend, but I've never considered "pretty much correct" as proof (and I have no dog in this fight whatsoever), also, that "pretty much correct" would bear extra scrutiny when it is coming from someone who benefits from such an answer.
That was me, covering my....
Old 3rd February 2017 | Show parent
  #5
Gear Head
 

Quote:
Originally Posted by graywolf View Post
That was me, covering my....
I just reread my previous post, and noticed it might not be clear. When I wrote,

Quote:
...also, that "pretty much correct" would bear extra scrutiny when it is coming from someone who benefits from such an answer
I was referring to the zoom rep. I hope I didn't cause any confusion with that.
Old 4th February 2017
  #6
Well then we're both right - you're correct that the limiters act in the analog domain rather than the digital (and that's a good design). And I'm right that it's possible to overdrive the A/D because the amount of gain reduction is limited.

I appreciate you finding out exactly how the limiter works, and I agree that for nearly all applications it should be sufficient.
Old 4th February 2017
  #7
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celticrogues's Avatar
 

Could you copy and paste here the text of what you posted on the other forum, as well as the Zoom rep's reply? I'd be interested to read it.

-Mike
Old 4th February 2017
  #8
Gear Addict
Here's a comparison of the F8 and an SD 633 illustrating the action of the limiters.

https://www.youtube.com/watch?v=xSRXba4CoQs

Fran
Old 4th February 2017 | Show parent
  #9
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Bruce Watson's Avatar
 

Quote:
Originally Posted by Fran Guidry View Post
Here's a comparison of the F8 and an SD 633 illustrating the action of the limiters.

https://www.youtube.com/watch?v=xSRXba4CoQs

Fran
That pretty much answers the questions as far as I'm concerned. One of the reasons to get a pro-level mixer is to get pro-level limiters. They really are worth it IMHO.

My wife dropped (from a just a few cm up) a glass mixing bowl on a granite counter top at a cooking demo I was filming for her. She didn't break it, but the resulting sound was loud enough in my headphones that I literally jumped even though I saw it when it happened and knew what it was. I'm just sayin' it was loud. I figured the sound there was toast and I'd spend quite a bit of time working it in post. But my MixPre-D's limiters handled it with ease; the only way I knew what happened was by watching the video. The sound was perfectly smooth without any clipping or artifacts at all. The limiter's compression was perfectly natural. Zero post work because of that mistake.

A couple of those and the mixer is paid for in the lack of post processing time. This is why I tell people that pro-level limiters are worth the cost. Because they have been to me.

Of course YMMV.
Old 4th February 2017
  #10
Here for the gear
 

Doubt much is going to get past the mixPre-D considering it has an input stage limiter and an output stage limiter. Pretty much as ideal a set up as one could want.

Still, I bet if you set the threshold of the f4 or f8 below the default of -2 dBFS the limiters would have a little more time to react and adjust the gain of the pres. According to the manual it has a threshold range of -2 to -16 dBFS, so I bet those limiters are a bit more versatile than they're being given credit for so far.

In the end, it does do dual channel recording for safety takes, as long as you don't mind using up an input channel.
Old 4th February 2017
  #11
Actually the limiter on the F4, maybe, should be called a hybrid limiter.

Hybrid, because while it acts in the digital domain, it acts on the analog stage as well.

There is a lot of headroom available if you are not trying to, stupidly, record at 0dbFS. Remember that 0dbFS means the digital signal is all ones, and a digital signal is only zeros and ones. 16, or 24, ones is all you can get.

If you are recording film dialog 16/48, and set your recorder for -12db (0dbVU in that case) You have 12db of headroom at your loudest normal recording. If your limiter is set at -6db soft-knee as mine is the sound starts rolling off at -6db and by the time it reaches 0db there is no more gain to cause clipping.

Normally, it does not reach the limiting stage, but if it does it sounds like you are using a compressor on the signal, not great, but nowhere near as harsh as clipping or the default -2db fast-knee overload limiting.

Now, no one who has these recorders is claiming they are as good as ones that cost 5+ times as much, but they are better than the old school recorders that only a few years ago cost 2 or 3 times as much.

Another point, hidden in the noise of the other thread, are a few posts by people who own these recorders, none of them are complaining about the recorders performance. All those complaints seem to be by people who "know" how things used to be. REMEMBER that a lot of those people were telling us the recorders were junk months before they were available even to reviewers, how could they know that?

In another couple of years there probably will be better recorders at this price point. At the moment, I consider the F-Series Zooms to be the bottom level professional recorders out there.
Old 4th February 2017
  #12
Test the limiters with gunshots. Then you will know if they are truly effective. A 9mm or .223 about ten feet away is a good test. If you can still hear conversations and no clipping on the gun shots at 140~150 db, it's working good.

If your recorder fails that test, you are then equipped to end it's life quickly.
Old 4th February 2017
  #13
Lives for gear
 

And the "jangling keys" test.
Old 4th February 2017 | Show parent
  #14
Quote:
Originally Posted by Fran Guidry View Post
Here's a comparison of the F8 and an SD 633 illustrating the action of the limiters.

https://www.youtube.com/watch?v=xSRXba4CoQs

Fran
After looking at Judd's article, I want to talk more about recording levels.

I took my Zoom F4 out to the park when I first got it to try it out. I used my blimped Audio Technics AT4073A (for those who do not know that old shotgun mic, it is probably one of the most sensitive mic's ever made).

Wow, terrible, I set my gain levels for a nice strong signal. Cars driving by on the road a 1/4 mile away drown out the sounds I was trying to record. Then, sitting on one of the park benchs, I pointed the mic at a jet flying miles above me up in the sky and it recorded quite clearly.

At that point I realized I had the gain set way too high, because I could not hear that jet with my ears. I turned the gain down, down, down. Somewhere about -32dbFS the extraneous sounds quieted down and the sounds I wanted became dominant.

The point here is that normally film types are not recording in a sound proof studio, but out in the real world. We can not record at maximum levels or we pick up too much garbage.
Old 4th February 2017 | Show parent
  #15
Quote:
Originally Posted by Jim Williams View Post
Test the limiters with gunshots. Then you will know if they are truly effective. A 9mm or .223 about ten feet away is a good test. If you can still hear conversations and no clipping on the gun shots at 140~150 db, it's working good.

If your recorder fails that test, you are then equipped to end it's life quickly.
I wonder? With unprotected hearing on the range a 9mm is annoying, a .223 hurts, when the guys get out the bigger stuff I want to be more than 10 feet away even with hearing protection. I hope you are using a nice cheap low sensitivity dynamic microphone.

And, it doesn't matter if gunshots clip anyway, they are already square waves. So if you can hear the conversation, and the gunshots do not damage the equipment is what I guess you are saying.

The loudest noise I have ever heard is a Harrier jet hovering about a thousand feet from the grandstands at an airshow. Record that and play it back at live levels in your living room and you will be replacing your windows and maybe your plaster. That was maybe 150db and went on seemingly forever, although I guess he only hovered out there for about a minute or there would have been lawsuits for hearing loss, it did leave me with a headache.

Once again, I am making a point here. You can always exceed the capabilities of the equipment if you do not know what you are doing. If you do know what you are doing your can do pretty darn well with rather modest equipment.
Old 30th November 2017 | Show parent
  #16
Here for the gear
 

Quote:
Originally Posted by graywolf View Post
Once again, I am making a point here. You can always exceed the capabilities of the equipment if you do not know what you are doing. If you do know what you are doing your can do pretty darn well with rather modest equipment.
I agree with this 100%. Knowing your gear is the most important part. I have gotten away with delivering professional-quality audio from the Zoom F4 because I gain properly (12-18dBFS of headroom) and prepare for each take. If something unrehearsed happens, it is not my responsibility because I communicate clearly before the production that the technical side of things can only work well, if it is prepared. It's crazy how much time and effort is spent on lighting and the perfect picture compared to audio preparation (rehearsing properly before shooting). So I have every right to ask for a retake if the production is interested in high quality and a mistake happens, that I could not prepare for. And while buying a device 5x the price does count as preparation on MY side (good limiters) it is so much cheaper to me to communicate properly, prepare every take properly and work with what I have as equipment. But that's just my way of doing things.

BTW, people have been posting Curtis Judd's "Analogue vs Digital Limiters" video as "proof" that the F Series limiters "suck". There is an update from Curtis:

YouTube

This is nothing new to the people in this forum who understand the principle of "hybrid limiters" but it shows again, let's get to know our gear perfectly so that we can get great results from it.
Old 30th November 2017 | Show parent
  #17
Gear Guru
 
jwh1192's Avatar
Quote:
Originally Posted by Behemoth1702 View Post
I agree with this 100%. Knowing your gear is the most important part. I have gotten away with delivering professional-quality audio from the Zoom F4 because I gain properly (12-18dBFS of headroom) and prepare for each take. If something unrehearsed happens, it is not my responsibility because I communicate clearly before the production that the technical side of things can only work well, if it is prepared. It's crazy how much time and effort is spent on lighting and the perfect picture compared to audio preparation (rehearsing properly before shooting). So I have every right to ask for a retake if the production is interested in high quality and a mistake happens, that I could not prepare for. And while buying a device 5x the price does count as preparation on MY side (good limiters) it is so much cheaper to me to communicate properly, prepare every take properly and work with what I have as equipment. But that's just my way of doing things.

BTW, people have been posting Curtis Judd's "Analogue vs Digital Limiters" video as "proof" that the F Series limiters "suck". There is an update from Curtis:

YouTube

This is nothing new to the people in this forum who understand the principle of "hybrid limiters" but it shows again, let's get to know our gear perfectly so that we can get great results from it.
thx for the link .. just watched .. interesting concept for the limiters !!!
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