Understanding Headphone Specifications, & Home Made Blast Limiters

[Hawk66]

Just to confirm from the manual PDF anyone can DL

"7.10. Audio Output
The Sovereign GT has a built in speaker so that the operator can hear the threshold and
target signals. It is however recommended to use headphones as these will allow the
operator to hear faint targets better and cut out environmental noise such as traffic,
others talking or the wind.
The audio output of the Sovereign GT is available through either the in-built speaker or
via a 1/4" stereo headphone jack. When a pair of headphones is plugged in, the
loudspeaker is disconnected.
Headphones are recommended for serious treasure hunting for several reasons: they are
more sensitive to slight target signals than the loudspeaker and their use will increase
battery life. The socket will accept most stereo headphones with a 1/4" jack. If your
headphones have a "Stereo/Mono" switch, set it to "Stereo". Minelab recommends
headphones to be between 32 and 100 Ohms."

To me it reads that 32 is the min required for normal operation, not the only recommended level.

 

[kered]

Look at it like this, Regardless of what the detector is sending to the headphone jack, depending on whats plugged into it will detemine the sound, just like plugging a 15v bulb into your car brake light and it will be dim, try a 9 volt and it will be bright for all the output to the lightbulb socket remains the same, also depending on the amp draw the fuse might blow or worse, melt some wires.

On the White dual field the threshold is directly tied to sensitivity, from the manual

T-HOLD
The T-HOLD is used to adjust the background hum (threshold). The threshold is the low hum you hear
when you are not detecting a target. The T-HOLD should be adjusted so that you can hear a slight hum
(edge of sound). If the hum is set too loud, it may mask some of the deeper targets. If it is set too low,
some of the deeper targets may not be heard. The T-HOLD also functions as a sensitivity control.
Setting it for silent operation will reduce sensitivity eliminating noise from nearby detectors or other
electrical sources, however, some reduction in detection depth can be expected.

So it seams that the engineers can do what they wish, the controls can do a number of things and have a double effect

 

[Rick(ND)]

The headphone I use for my Sovereigns and give the best tones and the most volume for me is the Timberwolfs Lobo, Predators and the FWD (I think that's their name), these are 150 Ohm set, but yet on my Explorers they are not as loud so I have a set of the Troy Pros which are the same 150 Ohms that I use on the Explorers and are loud enough on the Explorer, but not on the Sovereigns.. I also bought a set of 32 Ohm for $100 that are loud enough on the Sovereign, but the tone quality is not real great.
If i had normal hearing and not so deaf I feel the Sun Ray Pro golds would work good on the Sovereigns and the Explorers as to me they sound as loud on either detector.

 

[kered]

I use the sunray golds for both sov and etrac and don't notice much in the volume in general, what i do notice more on the sovereign is when the limiter cuts in, i run both machines at full volume and on the phones too, never had a blast that hurts, maybe i'm going deaf.

 

[Birdseed]

I like Kered's light bulb analogy, this says it all in the most simple terms. Think of impedance as resistance, (it is not really that different). Put a high resistance light bulb into a circuit and it will be dim and inefficient, put in a low resistance bulb and it will be very bright, but may overload the circuit and blow a fuse or melt something. With headphones on the GT as I said in my earlier post, anything from 32 Ohms to 150 or a bit more would probably be indistinguishable. Lower than 32 Ohms will start to progressively overload the detector.
The other thing to bear in mind is the efficiency of the phones themselves. Very efficient HiFi phones can cost an arm and a leg and will, in a quiet listening environment, reproduce the quietest of sounds. On a noisy beach these phones would be useless. I use a set of helicopter phones with the boom mike removed. These are about 150 Ohms but the gel filled ear pads and high quality electronics used make up for any slight inefficiencies of the higher impedance. In short if you find something that works for you, stick with it. Keep away from very light airy units as these may be good in the living room but won't cut it on the beach. The rest is up to you.

Peter downunder

 

[razorhoof]

So you are saying that my jolly rogers at 16 ohm is not good for my GT?

 

[Birdseed]

Razorhoof
At 16 Ohms your GT audio amplifier is delivering twice the current to your "Jolly Rogers" than they would to a set of 32 Ohm phones. The GT may be able to withstand this for a long time, maybe for the life of the detector, but it is outside the design specification of the detector. If you plug in too many appliances into your home power outlet you may get away with it for years, also you may have a hotter than normal day and get a melt down. Minelab say 32 to 100 Ohms, believe them. If Ford say don't rev your engine above 7000 rpm there may be consequences if you rev to 12000 rpm. But you may just get away with it. The choice is yours.
Learn a bit about Ohms Law. Current = volts/impedance.


Peter downunder

 

[otlew]

Copied from my post in New GT Video thread.

OK, being bored to tears in my hotel room I decided to do some research on speaker impedance and refresh my memory on electrical/electronic calculations.

Subject:
Impact of different speaker impedance on performance of a set of detector headphones.

Output Power is calculated as P=V2/Impedance

Impedance Ohms Yields Output Power in Watts

16 = 12 Watts
32 = 6
64 = 3
128 = 1.5

As can be seen doubling impedance halves the power output. It also lowers power consumption, which is why your batteries last longer if you use headphones as opposed to the speaker on the detector.

So the lower the impedance higher the possible volume but also higher power consumption.

Dynamic frequency range I think, is at least partially, a function of the quality of the speaker used in the headphones.

So does more power at the speakers make it easier to hear faint deep signals? Anyone know? I know the maker of the Rat Phones has big dissertation on this, but I can't seem to find the web page.

 

[w6pea]

If I spent all the time it takes me to read all of these posts and links I might be here in front of this computer 24+ hours a day.
Very good information and thank you for posting the links.

 

[Tony in FL]

I found an interesting set of headphones at Newegg - 32 Ohms, in-line volume control, cheap, and has good reviews:

http://www.newegg.com/Product/Product.aspx?Item=N82E16826179034

If I pull the trigger on a GT I may pick up a pair of these.

 

[otlew]

I found an interesting set of headphones at Newegg - 32 Ohms, in-line volume control, cheap, and has good reviews:

http://www.newegg.com/Product/Product.aspx?Item=N82E16826179034

If I pull the trigger on a GT I may pick up a pair of these.

These headphones should work fine, but apparently come with and adapter for 1/8" (3.5mm) to 1/4" (6.3mm) and I doubt the cord is coiled.

As opposed to the Detector Pro Treasure Ears that are also 32 Ohm and have individual volume adjustments, a 1/4" plug (the size on the GT), a cord that is coiled and is 6' (1.8 m) in length. They sell for $45 shipped from a forum sponsor. I find I need the coiled cord and like the individual volume control.

 

[Sven]

values of parts need to be changed if using different ohm speakers.
My orig headset I built for my Musketeer a number of years ago sound identical to the speaker out put
using Sony MDVR-200 headphone speakers (32 ohm). Then eventually made another set using 600
ohm speakers.

 

[Critterhunter]

values of parts need to be changed if using different ohm speakers.
My orig headset I built for my Musketeer a number of years ago sound identical to the speaker out put
using Sony MDVR-200 headphone speakers (32 ohm). Then eventually made another set using 600
ohm speakers.

 

[otlew]

I bought the Treasure Ears and I like the sound. Just one problem, they don't fit my ears, my earlobes hang out the bottom about a quarter inch, consequently they have about 3 hours use, total. I guess it is true that our ears and noses never stop growing.

They would be fine if I had smaller ears.

I am going to put them in the classifieds and keep looking for another pair of 32 Ohm per the Sovereign spec, this time I will try before I buy.

 

[Twinkies]

My GT arrived a few days ago and I sure dont like the Eagle Headphones that came with it, need to find something better.

 

[Critterhunter]

If I was looking for a cheap pair I'd got for those Treasure Ears. If I was wanting a limiter then I'd go for the Sunray Pro Golds, though they are about twice the price.

 

[w6pea]

I like my Grey Ghosts that I got with my Sovereign GT. Head Phones

 

[Critterhunter]

The Grey Ghosts I tried were flat as a blown tire to my ears. I've heard enough people praise them to wonder if I had a bad pair or something, because I was given them for free and I gave them back because they simply stunk on my GT. Like listening to music through a tin can.

 

[synthnut]

So I bought a set of the SunRay Golds which were really nice headphones , but were just not loud enough .....The limitter worked well , the tone was pleasing , but didn't give the "raw " tone that I was looking for to take a targets tone apart ......They were really comfortable and fit nicely on my head .....Had to send them back .....Then I got the Black Widow's and they came defective , and I had to send them back .....So I said " What the heck " and bought a pair of the Sony MDRV 150's that Crazyman was talking about , and I'll be darned if these phones are not some of the best sounding phones I've heard yet for my ears !!....I'm gonna order a couple more sets to have as backups !!....Heck , who would have thought that $20 headphones would sound so good on metal detectors ....They are not like the expensive phones that will work on just the Sovereign , or just the E Trac ......They work GREAT on both machines !!..... Now if I just had a limitter , I'd be all set , but I don't really need one on the E Trac .....I will need one on the Sovereign though if it hits anything like the GT .......Jim

 

[Critterhunter]

Bumped up this thread as somebody wanted to know the model # of the $20 Sony headphones from Walmart that several of us like for their excellent sound quality and comfort (they are medium sized or "studio" phones). Sony MDR V-150. Read the thread for more info...