GPZ 7000: Threshold Vs Sensitivity Vs Volume Vs Volume Limit (with Discussion On Audio Smoothing, Coil Control, Range Of Motion And Manual Ground Balance)

[Jonathan Porter]

On 2/25/2021 at 2:33 AM, jasong said:

And this is why I have said since 2015 that it's better to run in as high of Sensitivity as you can, and then to tamp it all down and control the mess with the audio controls.

I agree with just about everything you are saying as well as others in this thread so my comments are just my thoughts on the matter and not written in stone or anything like that. ? The rest that follows is not directing entirely at the quotation but your comments created a desire to put forward my POV.?

Sensitivity is very important to wring out an edge of detection target signal for sure but it can also kill faint signals if the control is overused. A good detectorist’s brain can get very good at picking out a signal from a busy background, the most powerful add-on to any detector is YOU after all.??

In essence I agree with the sensitivity first philosophy because it is a fundamental control, however I do not agree with Audio Smoothing use other than Off, IMHO that control should be limited to ZERO in ALL cases and all other adjustments made from there. Waving over a known target signal is not a good  approach to come to a conclusion about a target signal standing out or not, the reason being is the target signal is obviously breaking through the dead zone so of course it’s going to stand out if you damp down or filter out the background noise. But what about the signals that are right on the edge of detection, what happens to them when you introduce ‘dead Zone’ filtering?

I use the term dead zone because I’ve been corrected about my description of raising and lowering the noise floor filter through the use of Audio Smoothing. In essence it is the point where a target signal in relation to the threshold is allowed into the audio signal relative to the filtering, kind of like sensitivity of the threshold. Moving the dead zone relative to threshold dictates what can break through and what can’t. On the GPZ there is also a lot of other things going on at the same time when you introduce Audio Smoothing and is why I always use that control on OFF and will be recommending ML on any future models to not include it at all and instead mirror the way the whole concept has been approached on the GPX 6000.

The GPZ 7000 does not need Audio Smoothing, the electronics are so refined with regards to Sferic noise there is no need for it. It’s inclusion on the GPX series was as a measure of controlling Sferics noise which they are really bad for, and ML in their infinite wisdom allowed 50 billion control combinations to the detriment of the end user causing absolute confusion, everyone’s got a favourite set of settings to the point where Opinions are like backsides, everyone’s got one! To my mind it says the engineers do not have confidence in their ability to set some controls in stone instead relying on the operator to try and find the right combination. The Audio Smoothing is a carry over from a bygone era and operators just want to hang onto controls out of fear of change rather than sound reasoning associated with having a full understanding of the trade off.

Please do not take my wording personally, I’m passionate about the subject from my POV not about experienced operators opinions and what works best for them, I say this because this subject has come up before and my comments have left behind a lasting memory that I was unaware of. I am passionate about this but not insoluble. The GPZ is a very powerful tool and has the horsepower to be used in many different ways.

So everything else that has been said in this thread is pretty bang on the money especially Jasong and Goldhound’s comments. As I have said before the Gain levels on the timings are quite a bit different between Normal and Difficult, so it takes some mental flexibility to go from one to the other as the whole detector sounds different when you dance between them, another reason why I do not like test beds.

Assuming Audio Smoothing is turned off, you very quickly work out how much elevating sensitivity impacts on a target signal. Whenever you experiment on a ‘known’ target do not just wave over the target and make your call signal response, you need to walk away from ground zero and actually work the machine in the 50 square meter zone associated with the target and then come into the signal response and make your decision on any improvements. There is always a cut off on elevating sensitivity relative to ground signal, EMI and target signal and locations will be different. Only you can make the call on what ‘Actually’ works in your chosen location, so I recommend absolute honesty with yourself.

So cranking up sensitivity to excessively high levels then clipping that sensitivity by introducing Smoothing will indeed make the signals that make it through the filter stand out big time but the edge of detection signals, the ones that only just move the threshold pitch will be blended out too, they have to because you’ve filtered them out.

This then gets back to Range of Motion, a signal, depending on which direction you approach it, has a ‘lead in’ and a ‘tail out’. ‘Lead In’ is when your audio comes from a background ground signal behaviour that is averaged by the Semi-Auto GB just as the Threshold pitch starts to alter as the Rx of the coil starts to react to the field of a buried target, you then move the coil through the ‘Lead In’ section and pass over the loudest possible point of the target (dead centre or Ground Zero) this is where the target is at it loudest point assuming you have the coil over dead centre which is a whole different process of feeling around with the sweep direction and speed to find the true dead centre (Ground Zero).

‘Tail Out’ is as the target comes from peak volume back to background ground signal of the localised ground conditions. In all cases ‘Tail Out’ is twice as wide as the ‘Lead In’ this is because it takes time for electronics to recover. The ‘Lead In’ and ‘Tail Out’ is hugely affected by any sort of Motion filter and also swing speed. Elevating sensitivity to excessive levels can slurry up the ‘Lead In’ and ‘Tail Out’ information, adding Audio Smoothing makes them stepped where there is no partial information anymore but a significant step out of a filtered neutered background straight into a Pitch change, cranking sensitivity boosts the hell out of this giving a false sense of target definition, because the background noise is muted by the filter. It can seem like a cleaner signal but in reality you have distanced yourself from what is truly going on with the receiver by introducing filtering/dead zone.

This is all my opinion and I do not for a second want to seem like its my way or the hi-way as I find discussions like this very interesting and am always experimenting and trying different things. I use strong words because I’m passionate about what I do and believe in it 100%,  with the caveat of course being able to change my mind or have others change it for me.?

JP

 

 

 

 

[Gold Hound]

1 hour ago, afreakofnature said:

more on Volume Limit:

This is how I see Volume Limit.  It adjusts the maximum loudness (decibel) allowed out of the machine - OUTPUT.  You still have 20 increments to work with on the Volume (Audio Boost) control, no matter what you set your limit too.  It is just that each increment is exponentially greater based on increasing the limit you set.  I think this is why people see Volume Limit as a volume control because if you set your limit to 20 and set the Volume control at 8, but then lower your Volume Limit to 10 and leave your Volume on 8, you can see that it would be equivalent to a 4 back at the Volume Limit of 20.  Hence lowering the loudness heard.  It is completely relative to the Volume Limit set.  

 

If Volume Limit truly was a decibel cut off.  Then it would look like this below.  Where if you set your Volume Limit to 10 then on your Volume control you would have no change from 11-20.  But this is not true, loudness does still increase, even with a limit set.  Therefore the way I see it Volume Limit can lower the maximum volume (loudness, decibel) overall, but does not cut it off.  Think about it,  if you had a loud target cut off at 45 decibels but kept raising the volume regardless then even the faint sounds (and noise) could be as loud as 45 decibels.  Making everything sound the same.  This does not happen.  

In conclusion, like jasong has stated above.  This is all relative to YOUR hearing and not actual target strength (INPUT).

To me this is all making sense now.  I hope for others it is too, but I will still put my promo out there for videos of these controls in action ?  Keep'em coming!

Volume limit dose not modulate/compress the sound like your diagrams.

It mearly clips off the lowdest part of a signal that exceeds your setting what ever that is. Just like the Manual describes in its diagram.

[Gold Catcher]

1 hour ago, Jonathan Porter said:

 On the GPZ there is also a lot of other things going on at the same time when you introduce Audio Smoothing and is why I always use that control on OFF and will be recommending ML on any future models to not include it at all and instead mirror the way the whole concept has been approached on the GPX 6000.

Thanks for your valuable comments, JP, as always! I find your comment regarding the history of the smoothing feature on GPZ interesting (that it is some sort of relict from the past from operators who are afraid of loosing control). When the info about the 6000 started to appear, I wondered why there is no smoothing anymore, now I understand why. I have always advocated to use sensitivity wisely and control ground/target response conservatively via volume and threshold function in Normal, or eventually going to difficult but leaving smoothing off. For me personally, this means that I can go only so high with gain, perhaps to about 10 in Normal and 14 in difficult without loosing my mind after 8 hours detecting, or without compromising to hear faint targets (a more serious matter than just loosing my mind...). At least in the grounds I hunt these gain numbers are about as high as I can go-on good days. But IMHO, this is enough power to hear just every target the GPZ is able to find as long as no filters/processing is applied.

[afreakofnature]

36 minutes ago, Gold Hound said:

Volume limit dose not modulate/compress the sound like your diagrams.

It mearly clips off the lowdest part of a signal that exceeds your setting what ever that is. Just like the Manual describes in its diagram.

I am not saying that it modulates it just sets the maximum loudness limit of the volume control (well maybe I am calling it modulation).  If it truly did clip it and you set the limit to 1 then crank the volume up to 20 everything would sound the same from high signals to low signals and probably all of the noise.  But if you set the limit at 1 and crank up the volume to 20 you actually do get variations in the loudness still.  I could be wrong but other pieces of electronics out there that has Volume Limit describes it in this matter, Minelab could be doing there own thing but that's confusing.   IDK I can't test this yet, maybe we will get someone to try this in a video.

[Gold Hound]

31 minutes ago, afreakofnature said:

I am not saying that it modulates it just sets the maximum loudness limit of the volume control (well maybe I am calling it modulation).  If it truly did clip it and you set the limit to 1 then crank the volume up to 20 everything would sound the same from high signals to low signals and probably all of the noise.  But if you set the limit at 1 and crank up the volume to 20 you actually do get variations in the loudness still.  I could be wrong but other pieces of electronics out there that has Volume Limit describes it in this matter, Minelab could be doing there own thing but that's confusing.   IDK I can't test this yet, maybe we will get someone to try this in a video.

Im guessing that the clippers have a setting above the volume floor, it may start at say 5 who knows¿ the Ml tech that desighned the function obviously had the forsight to know that some one would run it at zero and wonder why the detector is not working lol. I can assure you that it dose not compress the sound in any way like you are thinking it might.

You are way over thinking this mate... just get out there and put some field time on your machine!

You probably need to do at least a full season detecting before you can write a manual, otherwise it is just ideas put together by some one who dose not have any field experince. 

I can guarantee you that JP, Jasong, Nenad, others and myself have gained our knowledge from our time in the field and willing ness to experiment! For example I detectct all day, clocking around 8 to 12 hours a day for 8 months of the year since 2 months before the official release of the detector. That is quite a lot of field time if you add it up? I wear through 4 pairs of military boots per year doing so.

Please do not take this the wrong way mate, I like your enthusiasm... its a rare thing these days lol, but I just want you to understand how we earnd our knowledge. And if you want to aquire it for yourself there really is no subsitute. You just have to get out there and earn it for yourself! 

[Gold Hound]

A tip for you mate.

You really need to experiment with different swing speeds and heights and be very controlled with it.

Perfecting your swing and undersanding its effect on targets and ground noise really is probably the most importaint part of becoming one with your detector.

Detetctors are like nice ladys... you need to learn how she likes to be swung, her curves and how to press her buttons.

[flakmagnet]

2 hours ago, Gold Hound said:

Perfecting your swing and undersanding its effect on targets and ground noise really is probably the most importaint part of becoming one with your detector.

A+ tip. One of the most overlooked but ultra-important aspects of detecting
especially with the GPZ

[afreakofnature]

3 hours ago, Gold Hound said:

You probably need to do at least a full season detecting before you can write a manual, otherwise it is just ideas put together by some one who dose not have any field experince. 

Just so you know my background.  I have been a field geologist for 20 years I have been prospecting for 18 years and detecting since the SDC came out.  I work full time so detecting/prospecting is a hobby.  I have used the GPZ for 3 seasons.  I have not used it to its full potential.  I am not writing a manual.  I have  been researching everything i can about this detector over the last 2 months, mainly from this forum and the other sources stated above.  I compiled a lot of information, I was willing to share it in an organized format but probably won’t now.  People can do their own.
 

I appreciate your comments on the controls and telling me how to detect but what I am seeking is technical specifics.  I want to know exactly what this is doing.  Others on this forum who have done the time same as you do give different opinions than how you have described it.  So you can understand my skepticism to only believe one person.

[Gold Hound]

On 2/25/2021 at 1:27 AM, afreakofnature said:

 

Yes, I have read the manual.  Over and over. Plus I have also done what Northeast has done and basically inserted a lot of DP, Knowledge Base and TreasureTalk articles based on a couple months of research.  I have used the Z for about 3 years now too.  I plan on posting this "revised" manual in the future for everyone to have.  I am hoping it will be kind of like a wiki that others would want to add to so all the content is in one PDF.  But before I do that I want to have a good "grasp" on how to adjust these controls for ZVT perfection (based on the ground you are in).

Hopefully some videos will roll in. Fingers crossed.

Sorry mate I didnt mean to offend or belittle you in anyway if it came across that way. Im mearly trying to stress the importance of the other things I was talking about, my dry aussie sense of humor dosent help either, went back and read my posts and can see how you could take offence from them sorry mate. I forget about the differences in aussie and yank comunication etiquette.

I thought from your post quoted above that you were compiling a revised more detailed form of manual. In my opinion injecting more detail and opinions into a manual just creates more confusion from any beginner who reads it. And after seeing your diagrams, that showed me you dont have a correct understanding of how the controls work. This prompted my post.

And videos are a lot of work to produce, so i wouldnt hold my breath waiting for them. I have over 1000 hours of recorded video of me  prospecting/ finding gold that will never see the light of day, as it is just to much work compiling and editing for no return for me to bother with. Hopfully others have more time and can produce one for you?

Or maybe you could produce them yourself?