Threshold - What is it, and do you use it?

[Iron Buzz]

The title is pretty much what I'm asking. What is the purpose of the threshold setting? I was under the impression that it was just an obsolete thing that was put in for the sake of old-timers, but I'm hearing hints of things that make me think it may be more useful for faint, deep targets than I realized. Can somebody talk to me about it?

 

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[OBN]

Here is a good reply from Rudy over on the other forum..

Confused about Threshold vs Volume?

---

Many newbies go out and buy a detector that has an adjustable, audible threshold and are confused by its function or proper use. The situation gets even more confusing if the detector also has a volume control. Oh wait, you also bought a nice set of earphones and they also have a volume control. What to do, what to do.

Ok, first, lets look at what is this so called threshold and what purpose an adjustable threshold serves. Then we can tackle what to do with the volume control. Setting both properly maximizes your ability to get as much depth as you can from your detector.

Not all detectors sold now a days have an adjustable threshold that you can hear. These latter machines are termed "silent search" detectors. Basically, they are quiet running until you sweep over a target and then they beep at you.

You can think of the threshold as a type of squelch control as found on a CB or short wave radio. Without a squelch control circuit on a radio, the speaker would be putting out a constant stream of hizzing noise when you are not tuned in to a station. This can be annoying. By dialing up on the squelch control, we are basically telling the radio that we don't want to hear a signal until it reaches a certain strength. The hizzing noise coming from the speakers is suppressed because it is low energy background noise and the radio is quiet until you tune in an actual signal. By the way, on some detectors the manufacturer calls the knob that adjusts the threshold a "tuning" knob. Now you know why.

If you dial in even more squelch, you'll start to miss some of the weaker signals from far away stations.

This is exactly how the threshold control works in a metal detector!

With a silent search machine, the "squelch" control is factory set to suppress the small signals and allow signals with a strength above the threshold setting to get through and make a "beep". If you bought a detector with an adjustable threshold (good for you!), you want to set it such that you can barely hear the threshold sound on your earphones. The sound is hard to describe, but it sounds like bees buzzing your ears. By having the threshold at this setting, right on the edge, you are guaranteeing that very weak signals (like from deep targets) will be able to get through the threshold control. This gives a machine with adjustable threshold a slight depth edge over a silent search machine, everything else being equal. This is because a very weak signal may not get through the "squelch" setting of the silent search machine.

You don't want to make the threshold any louder than what you can barely hear. If the threshold hum gets too loud, you'll miss the real small signals again. This time because they are drowned by the louder threshold buzz.

If like some other folks you can't stand that constant low level buzzing sound of the threshold, you can always back it down a hair until it is not audible anymore. Essentially, you'll be running the detector as if it was a silent mode machine. But you pay a price for doing so. First, you'll lose some of that depth advantage you had over a silent search machine. If you back off on the threshold to just make it inaudible and no more, then you haven't lost much depth. Second, you'll lose some potentially valuable information. You see, when you go over a ferrous item, the threshold sound will usually null (will go quiet) momentarily. When this happens, your detector may not detect a valid target for some time after that. This elapsed time is called the recovery time and varies by the detector model used.

When you hear the threshold null out, you know you went over a ferrous item and you need to slow down and or change your sweep direction lest you miss a valuable target buried nearby the ferrous item. With a silent search machine you won't know it's happening.

Ok, now that we understand threshold, lets look at volume. This is again, just like a radio. Your detector may or may not have a volume control (separate from the threshold or tuner). If it doesn't have one, you definitely would want earphones with volume control. If you have volume control in both the detector and the earphones, then set one at max volume and set the other one to actual use conditions.

My MXT does not have a volume control but it has a very powerful (read that loud) audio amp. So, I set the volume control on my earphones to produce as loud a beep as I can without it being painful. I do this by just dropping my digger on the ground and sweeping over it and advancing the volume control until it as loud as I want, without hurting my ears.

Then I set the threshold control until I can barely hear the buzz. As a side note, if the threshold is erratic instead of stable, the Gain is too high for the ground you are sweeping. Back off on the gain until the threshold is stable.

That's it! Hope you found this useful. For information on understanding the sounds your metal detector makes you might want to look at


__________________
HH, Rudy

I could not find what I find without the threshold. Deep faints in PP that many others have walked over....

Just a break, small bump or a disruption of the threshold....tells me dig..

 

[Iron Buzz]

Great explanation by Rudy! I think I understood everything I read there (until I can get out and actually practice it, I'm never sure) but I'm confused by something that you said: "Deep faints in PP that many others have walked over...." PP... is that PinPoint mode? You put the detector into pinpoint mode to work with threshold?

 

[wallrat_1975]

Yes, basically what he is saying is that using threshold he was able to hear the "disruption" and by using pinpoint, was able to find the target. I think you are getting the picture. I personally rarely use it, however that is due to my hunting situations and not going crazy. Certain situations definitely make it an awesome tool to have!

HH
-Bill

 

[sgoss66]

Iron Buzz --

I would like to respectfully disagree with some of what Rudy said, as, with all due respect, some of it is not correct information with respect the Equinox specifically.

To clarify...what Rudy said there is correct, if you are running a machine that employs a TRUE threshold. HOWEVER -- the Equinox DOES NOT employ a true threshold, except in the Gold modes (on the 800).

In all of the other modes on the Equinox -- and this is also true on the CTX 3030, E-Trac, Explorers, etc. -- the threshold employed is NOT a "true" threshold. It is considered a "reference" threshold. And there is a very important distinction that should be understood, between a TRUE threshold, and a REFERENCE threshold. I won't describe how a "true" threshold works, as Rudy described it quite well for a machine that employs such a threshold.

HOWEVER, Here's how a "reference" threshold works, on the Equinox (again, the type of "threshold" that is employed when running in Park, Field, and Beach modes, and on the other above-mentioned Minelab machines).

When your machine's coil is sweeping over bare ground, and you have the threshold volume set to an "audible" level, you will of course hear the steady hum of the threshold. This threshold, really, is simply there to allow you to, basically, know that your machine is "running" i.e. not "turned off." That's really the main purpose, and is why it is called a "reference" threshold. It allows you a "reference," at any time, to know that your machine is indeed "turned on" and "running," as long as you are hearing that threshold hum.

IF you have ZERO discrimination applied, on your Equinox, i.e. the horseshoe button pressed thus allowing all targets to be "accepted," then you will hear a constant, continuous threshold hum at all times, UNTIL you pass over any metal target. When you pass over ANY target (since ALL targets are "accepted"), the audio you hear will quickly switch from the background threshold hum, to the appropriate "tone" for that target, and then will quickly revert back to the hum of your "reference threshold" once your coil has passed the target. In other words, the threshold hum is essentially continuous, except for the brief instances when your machine is reporting the audio for a target that is under the coil.

IF, on the other hand, you have some discrimination applied -- i.e. NOT all VDI values are "accepted," then things change a bit. In this case, every time you pass your coil over a DISCRIMINATED target, you will hear the threshold "drop out" briefly -- i.e. it "blanks" or "nulls" or "goes silent" for a moment. This period of "silence" lets you know that your coil has passed over a target that you have chosen to discriminate. The period of "silence" of the threshold hum, corresponds directly and exactly to the period of time that the machine WOULD HAVE BEEN reporting the target's tone, had you not discriminated that target.

THAT IS ALL THAT THE REFERENCE THRESHOLD ON THE EQUINOX (or the other Minelab machines that I mentioned) DOES -- again, the exception being on the 800, when running in Gold mode. And so, from this perspective, Rudy's statement that "Setting (your threshold) properly maximizes your ability to get as much depth as you can from your detector" is NOT TRUE, on the Equinox, when running in Park, Field, and Beach modes -- because, again, the threshold is NOT a "true" threshold, but simply a "reference" threshold when running any of these 3 modes on your Equinox.

In GOLD mode, on the Equinox, the threshold is a TRUE threshold. In other words, it functions in accordance with what Rudy described; it is similar to the "squelch" on CB -- it sets the level that a "signal" that is received by the unit is strong enough to "break through" that level, and report to you. As I said, I won't go into "true" threshold here, since this post is already more than long enough, and Rudy already described it well.

I know that was long-winded, but hopefully I wrote it clearly enough so that it can be understood.

In short, and to repeat, you DO NOT gain a depth advantage on an Equinox in Park, Field, or Beach mode by running your threshold audibly, because the Equinox in those modes is employing only a "reference" threshold, NOT a "true" threshold. You can safely run your Equinox's threshold volume at "zero" (i.e. silent) if you so choose, and NOT risk missing any "weak" targets...

Thanks!

Steve

 

[wallrat_1975]

I didn't know that, however it makes sense. Again, I don't really use it here as you know our ground around here, but when I do this is great info. Thanks Steve!

 

[ColonelDan]

Iron Buzz --

I would like to respectfully disagree with some of what Rudy said, as, with all due respect, some of it is not correct information with respect the Equinox specifically.

To clarify...what Rudy said there is correct, if you are running a machine that employs a TRUE threshold. HOWEVER -- the Equinox DOES NOT employ a true threshold, except in the Gold modes (on the 800).

In all of the other modes on the Equinox -- and this is also true on the CTX 3030, E-Trac, Explorers, etc. -- the threshold employed is NOT a "true" threshold. It is considered a "reference" threshold. And there is a very important distinction that should be understood, between a TRUE threshold, and a REFERENCE threshold. I won't describe how a "true" threshold works, as Rudy described it quite well for a machine that employs such a threshold.

HOWEVER, Here's how a "reference" threshold works, on the Equinox (again, the type of "threshold" that is employed when running in Park, Field, and Beach modes, and on the other above-mentioned Minelab machines).

When your machine's coil is sweeping over bare ground, and you have the threshold volume set to an "audible" level, you will of course hear the steady hum of the threshold. This threshold, really, is simply there to allow you to, basically, know that your machine is "running" i.e. not "turned off." That's really the main purpose, and is why it is called a "reference" threshold. It allows you a "reference," at any time, to know that your machine is indeed "turned on" and "running," as long as you are hearing that threshold hum.

IF you have ZERO discrimination applied, on your Equinox, i.e. the horseshoe button pressed thus allowing all targets to be "accepted," then you will hear a constant, continuous threshold hum at all times, UNTIL you pass over any metal target. When you pass over ANY target (since ALL targets are "accepted"), the audio you hear will quickly switch from the background threshold hum, to the appropriate "tone" for that target, and then will quickly revert back to the hum of your "reference threshold" once your coil has passed the target. In other words, the threshold hum is essentially continuous, except for the brief instances when your machine is reporting the audio for a target that is under the coil.

IF, on the other hand, you have some discrimination applied -- i.e. NOT all VDI values are "accepted," then things change a bit. In this case, every time you pass your coil over a DISCRIMINATED target, you will hear the threshold "drop out" briefly -- i.e. it "blanks" or "nulls" or "goes silent" for a moment. This period of "silence" lets you know that your coil has passed over a target that you have chosen to discriminate. The period of "silence" of the threshold hum, corresponds directly and exactly to the period of time that the machine WOULD HAVE BEEN reporting the target's tone, had you not discriminated that target.

THAT IS ALL THAT THE REFERENCE THRESHOLD ON THE EQUINOX (or the other Minelab machines that I mentioned) DOES -- again, the exception being on the 800, when running in Gold mode. And so, from this perspective, OBN's statement that "Setting (your threshold) properly maximizes your ability to get as much depth as you can from your detector" is NOT TRUE, on the Equinox, when running in Park, Field, and Beach modes -- because, again, the threshold is NOT a "true" threshold, but simply a "reference" threshold when running any of these 3 modes on your Equinox.

In GOLD mode, on the Equinox, the threshold is a TRUE threshold. In other words, if functions as according to what Rudy described; it is similar to the "squelch" on CB -- it sets the level that a "signal" that is received by the unit is strong enough to "break through" that level, and report to you. As I said, I won't go into "true" threshold here, since this post is already more than long enough, and Rudy already described it well.

I know that was long-winded, but hopefully I wrote it clearly enough so that it can be understood.

In short, and to repeat, you DO NOT gain a depth advantage on an Equinox in Park, Field, or Beach mode by running your threshold audibly, because the Equinox in those modes is employing only a "reference" threshold, NOT a "true" threshold. You can safely run your Equinox's threshold volume at "zero" (i.e. silent) if you so choose, and NOT risk missing any "weak" targets...

Thanks!

Steve

I agree with Steve. I run my EQX 800 in 0 threshold on the beach. I prefer it and haven't seen any adverse effect in terms of depth when compared to a slight threshold. But as I always say, that's just what I prefer and what I've seen works for me on the beaches I hunt. Your preference and situation may vary.

 

[sgoss66]

Bill,

Yep -- since you don't run with your threshold audible in the first place, none of what I wrote (i.e. whether the Equinox is using a "true" threshold, versus a "reference" threshold) makes any difference, for you.

For what it's worth, I was not trying to be pedantic with that post, so I hope it didn't come off that way; I was just hoping to maybe help clear up some misunderstanding, as it's a misunderstanding that has come up before, with Minelab's FBS machines (and now Multi-IQ) -- in that what is being called a "threshold" by Minelab, in these cases, is really not a "threshold" the way long-time, experienced hunters have come to understand threshold. And as such, the "rules" that the old timers have learned, regarding how to "maximize depth" on their machines through effective understanding of threshold, DO NOT APPLY to FBS and Multi-IQ operation. In all reality, FBS/Multi-IQ "threshold" should not even be CALLED "threshold," IMO, because by calling it that, the concepts it calls to mind for experienced users of machines that DO employ a true threshold, are misleading. It should, in all fairness, be called "reference hum," or something like that, as opposed to "threshold," so as to not muddy the waters with misunderstanding.

Steve

 

[OBN]

Iron Buzz --

I would like to respectfully disagree with some of what Rudy said, as, with all due respect, some of it is not correct information with respect the Equinox specifically.

To clarify...what Rudy said there is correct, if you are running a machine that employs a TRUE threshold. HOWEVER -- the Equinox DOES NOT employ a true threshold, except in the Gold modes (on the 800).


Thanks!

Steve

My Minelab excalibur is the same, the threshold is only usable in PP to hear the faint disruptions. In discriminate that method does not work. And remember Rudy wrote this in 2012 I believe.

 

[sgoss66]

OBN -- OH! If Rudy wrote that in 2012, thus obviously not with the Equinox in mind, then that makes total sense; he was writing about "true" threshold (and without any reference to any specific machine).

Meanwhile, it sounds like the Excal ALSO uses a "reference" threshold, as opposed to a "true" threshold (aside from PP mode). Interesting!

Steve

 

[OBN]

OBN -- OH! If Rudy wrote that in 2012, thus obviously not with the Equinox in mind, then that makes total sense; he was writing about "true" threshold (and without any reference to any specific machine).

Meanwhile, it sounds like the Excal ALSO uses a "reference" threshold, as opposed to a "true" threshold (aside from PP mode). Interesting!

Steve

I just looked it up//2008, sorry about that..

 

[Iron Buzz]

Bill,

Yep -- since you don't run with your threshold audible in the first place, none of what I wrote (i.e. whether the Equinox is using a "true" threshold, versus a "reference" threshold) makes any difference, for you.

For what it's worth, I was not trying to be pedantic with that post, so I hope it didn't come off that way; I was just hoping to maybe help clear up some misunderstanding, as it's a misunderstanding that has come up before, with Minelab's FBS machines (and now Multi-IQ) -- in that what is being called a "threshold" by Minelab, in these cases, is really not a "threshold" the way long-time, experienced hunters have come to understand threshold. And as such, the "rules" that the old timers have learned, regarding how to "maximize depth" on their machines through effective understanding of threshold, DO NOT APPLY to FBS and Multi-IQ operation. In all reality, FBS/Multi-IQ "threshold" should not even be CALLED "threshold," IMO, because by calling it that, the concepts it calls to mind for experienced users of machines that DO employ a true threshold, are misleading. It should, in all fairness, be called "reference hum," or something like that, as opposed to "threshold," so as to not muddy the waters with misunderstanding.

Steve

No, it did not come off at all pedantic, Steve. That clarified a lot of my confusion. Thanks for taking the time to write all of that.

 

[dirtlooter]

great question that truly helps several of us understand the difference with the ML detectors. great explanations on both parts to what they pertain to. Thanks to all

 

[vferrari]

Agree with everything Steve posted regarding threshold as it applies to Equinox in the non-gold modes.

One minor thing. Some users (including myself) have experienced threshold blanking in AM mode without a ferrous or non-ferrous tone registering. Not much is confirmed regarding this phenomenon, but it is therorized that the Equinox is indeed registering a faint target but it does not meet the "threshold" to enable it to get processed by the detector. This may be due to the fact that AM on Equinox is not "true" all metal either. The raw target signals are still subject to some level of signal processing and "discrimination" ecpven in AM, so something that gets detected but not processed may trip the threshold blanker. Not clear if this is a useful feature, but it definitely exists.

 

[OBN]

LOL, I just noticed this was on the Nox's forum. I was trying to figure out the reason the Nox was mentioned so much..I'm Getting old fast...

 

[sgoss66]

LOL, I just noticed this was on the Nox's forum. I was trying to figure out the reason the Nox was mentioned so much..I'm Getting old fast...

LOL! I understand, OBN!

Steve

 

[sgoss66]

Agree with everything Steve posted regarding threshold as it applies to Equinox in the non-gold modes.

One minor thing. Some users (including myself) have experienced threshold blanking in AM mode without a ferrous or non-ferrous tone registering. Not much is confirmed regarding this phenomenon, but it is therorized that the Equinox is indeed registering a faint target but it does not meet the "threshold" to enable it to get processed by the detector. This may be due to the fact that AM on Equinox is not "true" all metal either. The raw target signals are still subject to some level of signal processing and "discrimination" ecpven in AM, so something that gets detected but not processed may trip the threshold blanker. Not clear if this is a useful feature, but it definitely exists.

vferrari -- I know exactly what you are talking about. I HAVE heard a very brief "blanking" of the threshold, at times, EVEN THOUGH I run with nothing discriminated. That, in theory, should NOT happen, as the only "blank" or "null" in the threshold should occur when passing over a discriminated target. It doesn't happen often, and it's brief, when it does, but what you suggested -- i.e. a very weak signal that is "strong enough" to initiate that "pause" in the threshold, and yet NOT strong enough to allow the machine to assign and report a target tone -- is a logical conclusion. The ONLY other thing I thought it might be, is a temporary, very brief drop-out in headphone audio (i.e. not a threshold "null" per se, but a brief Bluetooth or wireless "glitch," to where you hear no threshold hum for a fraction of a second). Not sure...

Steve

 

[sgoss66]

Agree with everything Steve posted regarding threshold as it applies to Equinox in the non-gold modes.

One minor thing. Some users (including myself) have experienced threshold blanking in AM mode without a ferrous or non-ferrous tone registering. Not much is confirmed regarding this phenomenon, but it is therorized that the Equinox is indeed registering a faint target but it does not meet the "threshold" to enable it to get processed by the detector. This may be due to the fact that AM on Equinox is not "true" all metal either. The raw target signals are still subject to some level of signal processing and "discrimination" ecpven in AM, so something that gets detected but not processed may trip the threshold blanker. Not clear if this is a useful feature, but it definitely exists.

vferrari --

I know exactly what you are talking about. I HAVE heard a very brief "blanking" of the threshold, at times, EVEN THOUGH I run with nothing discriminated. That, of course, in theory, should NOT happen, as the only time a "blank" or "null" in the threshold should occur, is when passing over a discriminated target. I don't know about your experience, but for me it doesn't happen often, and it's brief, when it does. But, what you suggested -- i.e. a very weak signal that is "strong enough" to initiate that "pause" in the threshold, and yet NOT strong enough to allow the machine to assign and report a target tone -- is a logical conclusion. The ONLY other thing I thought it possibly could be, is a temporary, very brief drop-out in headphone audio (i.e. not a threshold "null" per se, but a brief Bluetooth or wireless "glitch," to where you hear no threshold hum for a fraction of a second). Not sure...


Steve​

 

[cudamark]

Agree with everything Steve posted regarding threshold as it applies to Equinox in the non-gold modes.

One minor thing. Some users (including myself) have experienced threshold blanking in AM mode without a ferrous or non-ferrous tone registering. Not much is confirmed regarding this phenomenon, but it is therorized that the Equinox is indeed registering a faint target but it does not meet the "threshold" to enable it to get processed by the detector. This may be due to the fact that AM on Equinox is not "true" all metal either. The raw target signals are still subject to some level of signal processing and "discrimination" ecpven in AM, so something that gets detected but not processed may trip the threshold blanker. Not clear if this is a useful feature, but it definitely exists.

I notice that too, as I hunt in all metal almost all of the time......and I like to run some "threshold" hum as I have always done. I just can't get used to silent search. Anyway, I just assumed (rightly or wrongly) that the momentary blanking was the change in ground matrix/mineralization and the machine's adjustment to it. I doesn't bother me in the slightest, in fact, I kind of like it. It gets me to slow down a bit and listen more carefully.

 

[Iron Buzz]

... and I like to run some "threshold" hum as I have always done. I just can't get used to silent search.

LOL! As I said in my original post, "I was under the impression that it was just an obsolete thing that was put in for the sake of old-timers"