Jump to content

SDC Threshold Question


Recommended Posts

Hey everyone,

 

First post here - Well, I'm about to take the plunge and use my hard earned savings to purchase an SDC 2300. By the way, thanks a bunch Steve for all your posts and reviews - I've probably spent a decent 24 hours reading through everything you've written about them.

 

I've also been heavily researching how to get a really good signal from them without using a booster.

I've heard from a few blokes recently who have been using 300-600 ohm headphones, and it appears they are hitting twice as many targets by using this high ohm range - due to its extreme sensitivity and how other headphones or boosters cannot pickup these subtle sounds.

 

I'm just wondering if there is any possible credence or theoretical/mechanical basis to these claims? If so, should I be looking for headphones like the Sennheiser HD 600 (300 ohm) or the Beyerdynamic DT880 (600 ohm) Headphones?

I've also heard great reviews about the Sunray Pro-Golds, but they seem lacking in this 'ohm' department according to my recent research..

 

Thoughts anyone?

 

Jimmy 

  • Like 1
Link to comment
Share on other sites


I've been curious about the actual audio output and speaker quality on metal detecting headphones as well.

I think most of the emphasis manufacturers place on their headphones is ruggedness and just make vague claims about the "faintest whispers from nuggets can be heard".

I'd like to know if anyone's done any research like you're asking about specific ohm ranges that are compatible with our metal detectors that output the best signal.

I mean it's not like we're trying to listen to rock music coming out of our Minelab's. We're listening to electronic tones the machine is spitting out based on what the electronics inside are trying to tell us.

I've had a pair of Sunray Pro Golds I've been using for a few years now that work fine and I've found some nice gold with. But I've been wondering if the $120 headphone "connection" I have with my $10k detector can be improved at all.

 

By the way Jimmy I don't know where you're located but I'm selling a used SDC 2300 if you're interested. Drop me a message if you'd like.

  • Like 1
Link to comment
Share on other sites

Sounds dubious to me, especially the doubling of finds part.

 

Unless I'm misunderstanding something, attaching 600 ohm headphones to a circuit designed for 4-8 ohms is going to make it quieter, might even actually need to get a booster to bring it back up to normal loudness, though maybe the SDC has robust audio control already, dunno since I don't have one. But electronics gurus please correct me if I'm wrong there...

 

Also, the amps in detectors aren't designed with nearly the frequency response that high dollar audio amps are made with, which is what those sorts of headphones are intended for. It's like hooking a $300 pair of headphones to a Walkman from 1984...except probably worse. Or trying to listen for frequencies on a 60 year old record that just aren't there to begin with.

 

Though I bet the sound deadening capabilities on a set of nice studio headphones are excellent, that is one positive that could make a difference.

 

Gladly change my opinion given new evidence to the contrary though.

  • Like 2
Link to comment
Share on other sites

Seems to me the "gain" knob is mis-named. It should be named "loss". 

 

With the initial settings for "gain" on my GMT marked at 7 1/2 I have only found "loss" to be the setting that will produce the best steady hum, usually having to run gain at 2 - 2 1/2 in ground where I hunt.

 

This "gain" setting, on the GMT, (7 1/2 ) is where ferrous is nulled - it's just a  bench mark.

 

When trying to balance the "gain" and the SAT on my GMT in order to keep a quick Thold recovery, swing speed is very critical. These two functions, gain and SAT,  must be balanced and an adjustment to swing speed is necessary or you will get lapses in Thold recovery. (this is the "steady" part)

 

In really mineralized ground, the hunt is slowed way down, especially if there are cold rocks in the matrix. These cold rocks cause the machine to think harder and take longer for the electronics to respond, forcing swing speed to be the end adjustment.

 

Low and slow, coil to the soil, snails pace hunting . zip, zip! Did ya hear that!

Link to comment
Share on other sites

Bado 1,yea i run my sdc with very little threshold also,but good headphones really help. Maybe not the deepest running machine for the money but if your looking for specimen gold or porous it works for me.

I have found some nice spongy gold fairly deep running very quiet, couldnt have heard them without headphones though,my ears are bad also.

  • Like 2
Link to comment
Share on other sites

Sounds dubious to me, especially the doubling of finds part.

 

Unless I'm misunderstanding something, attaching 600 ohm headphones to a circuit designed for 4-8 ohms is going to make it quieter, might even actually need to get a booster to bring it back up to normal loudness, though maybe the SDC has robust audio control already, dunno since I don't have one. But electronics gurus please correct me if I'm wrong there...

 

Also, the amps in detectors aren't designed with nearly the frequency response that high dollar audio amps are made with, which is what those sorts of headphones are intended for. It's like hooking a $300 pair of headphones to a Walkman from 1984...except probably worse. Or trying to listen for frequencies on a 60 year old record that just aren't there to begin with.

 

Though I bet the sound deadening capabilities on a set of nice studio headphones are excellent, that is one positive that could make a difference.

 

Gladly change my opinion given new evidence to the contrary though.

 

Makes sense to me. If the source (detector) isn't requiring high-end studio headphones like a $10k McIntosh amplifier might then we should be fine just using the regular detector headphones that are on the market.

  • Like 1
Link to comment
Share on other sites

Sounds dubious to me, especially the doubling of finds part.

 

Unless I'm misunderstanding something, attaching 600 ohm headphones to a circuit designed for 4-8 ohms is going to make it quieter, might even actually need to get a booster to bring it back up to normal loudness, though maybe the SDC has robust audio control already, dunno since I don't have one. But electronics gurus please correct me if I'm wrong there...

 

Also, the amps in detectors aren't designed with nearly the frequency response that high dollar audio amps are made with, which is what those sorts of headphones are intended for. It's like hooking a $300 pair of headphones to a Walkman from 1984...except probably worse. Or trying to listen for frequencies on a 60 year old record that just aren't there to begin with.

 

Though I bet the sound deadening capabilities on a set of nice studio headphones are excellent, that is one positive that could make a difference.

 

Gladly change my opinion given new evidence to the contrary though.

 

Jasong you are correct in your assessments of loudness v impedance matching and frequency response of amplifiers v the loudspeaker (headphone).  

 

http://www.soundonsound.com/sos/jan03/articles/impedanceworkshop.asp

 

This link is way more than a detectorist may need to know, however this article (for musicians and studio people) is well written and accurate.   

  • Like 1
Link to comment
Share on other sites

My understanding is that it is not a case of more is better but that the ohms should match the instrument.

 

Correct in the situation of a single loudspeaker (headphone) into one amplifier output.  

 

Very high impedance headphones were developed for and have a "better" attribute when plugged into console of parallel connectors from one amplifier and your goal is to just "monitor" the audio without affecting the power delivered to the more critical main loudspeakers.    Not the detectorists' application at all. 

  • Like 1
Link to comment
Share on other sites

Thanks for the responses guys - Re Headphones and high ohms - not that important, in and of itself  :)

 

I'll certainly be checking out the link you posted wirelessguy - and try to make sense of it.

 

I reckon at this stage I'll probably get one of those Sunray Pro-Golds, as the majority seem to use them and relish them.

 

But, if anyone else has a differing point of view - aka. high ohms works, I'd still be interested in hearing your potential theory behind that notion

 

Jimmy

 

@ Tortuga - I'd probably be interested in your SDC! However, but I'm based in Australia - so purchasing here :)   

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...