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Adding Impedance To My In Ear Monitors


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Disclaimer:  My testing is not rigorous nor scientific in any way.  Individual hearing is highly subjective and what works for me may not work for you.  As always your mileage may vary.

Detector: Minelab 7000 - HY, Normal, Sens 20, Volume max

Earphones:  Etymotic 4s  100 ohm impedance

Adapter: APureSound 75 ohm impedance 1/4 inch headphone jack conversion to 1/8 earphone jack.

Amplifier:  FiiO A3

I have always used the Ety earphones in all my previous GPX detectors.  Headphones are just too hot and cumbersome for me.  The Ety's are top of the line In Ear Monitors with balanced armatures.  Ety was primarily a hearing aid manufacturer and got into the earphone market for high end earphones.  The 4s cost in the neighborhood of $300.00.  Their 3 flange silicone ear piece is super noise isolating, but not particularly comfortable.  If you are worried about hearing snakes, cougars, bears and such, you won't like this much noise isolation. 

Until I went out with Lucky Lundy I was very happy with using the WM12 external speaker for all my detecting.  But after seeing his results with really good headphones, I was convinced I was missing some of the super faint targets.  I switched to another brand of earphone while I was out there at Rye Patch and was getting decent results but the audio was harsh giving me more of an audio fatigue.  

So, for the past couple days I've been playing around with different audio setups trying to find a good balance.  After locating a few undug faint targets, I switched back and forth between audio setups over these targets.  My results were interesting but not particularly life changing. 

Adding 75 ohms of impedance bringing my total impedance to 175 lowered the available volume sufficiently for my 62 yr old impaired hearing that I added the mini music amplifier to give me more volume.  My unscientific impression of adding more impedance felt like adding audio "smoothing".  The audio seemed a little more stable and less jittery.  Again, I switched back and forth over the same targets adding impedance and then without it.   I even switched between the wireless WM12 and a direct connection to the detector, which did not seem to make any difference in the quality of the tone.  I also ran Beats sports earphones with 27 ohms impedance.  The audio sounded really harsh with too much uncomfortable scratchy highs.  Adding the impedance made them tolerable, but not great.   Results: Running 175 ohms impedance produced a smoother, more stable background but lowered audio volume. 

The most significant thing I found in my testing was playing around with the Threshold.  I had been running Threshold at low 30's with the external speaker, but with the earphones that's just too much "noise" too close to the earbones.   With these In Ear setups I found that I could run the Threshold at 0 and get perfectly identifiable target tones over these tiny, tiny targets.  The best I can describe it is the detector has a rhythm of background beeps and bleeps, but over a tiny target the beeps stretch into a faint hum.   A good target will come through loud and clear without any confusion.

My target results are impressive.  The smallest nugget is .09 gram.  I found all these over the past 2 mornings in ground that I've been over dozens of times.  I am certain that the earphones with their noise isolation improved my results, but adding the impedance probably just made the audio a little more comfortable.  Bottom line, good aftermarket headphones already have between 100 and 200 ohms of impedance.  Frankly, I don't think adding more than that will produce much benefit.  Adding the mini amp helped me, especially running with 0 Threshold. 

 

Yuma new 003.jpg

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good detecting, Condor!

Detecting takes considerable concentration, you really have to pay attention to hear faint signals. From your results it appears you have found an excellent set-up for you. As you said your good sounds may be bad to me, too loud, too harsh or even not audible...we all have to find our own path in life and in detecting...

fred

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1 hour ago, fredmason said:

good detecting, Condor!

Detecting takes considerable concentration, you really have to pay attention to hear faint signals. From your results it appears you have found an excellent set-up for you. As you said your good sounds may be bad to me, too loud, too harsh or even not audible...we all have to find our own path in life and in detecting...

fred

Never a truer word spoken

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