Specific Info:32ohm headphones for Xterra 705

[GTzer]

Argyle's response in the "Koss headphones" thread caught my eye-reguarding his opinion on using -specifically-32 ohm headphones for the xterra.

"the cheap twin volume control RPG phone at 32ohm are the most perfectly suited to XTerra's, any detector for that matter. The cord is far too long so you have to shorten it and pop a new plug on. Or attach a curly-cord if you prefer them, the cups click off very easily.
If you want to get the most out you're 705, especially if you'll be using the threshold, or in prospecting mode, you will gain inches in depth by using phones that suit, as the right phones can pick up wavering changes that the higher ohm's cannot.

Always be on the lookout for some of those old second hand 8ohm and 32ohm phones from 30 years ago too, and keep a collection of them, as some are fantastic for our units."

I'd sure like to hear more about this info.
Is it to match the output?
Is battery life affected?

If 32ohms is the best match-why do the expensive headphones have such a higher ohm rating?

In many cases you get what you pay for-BUT sometimes that just isn't true.

My priority list for the high end phones are (or would be):
1-limiter for loud signals
2-Tie for weight,comfort,durability,warranty and exterior noise cancellation
3-quality/sensitivity of signal sound and volume controls

So are there any 32 ohm phones with a limiter? (just asking-I'll keep looking)

Any input would be appreciated.

 

[argyle]

Battery life cannot be affected, and you won't need a limiter unless you run an amplifier and live on the threshold. Any phone that is clear with pleasing tone to you're hearing will suit.

 

[BADBAJA]

Minelab reccomends 32ohm on the 705. Not sure about the others but they are in the same line.

 

[GTzer]

Thankyou for the replies.The audio 200 phones that came with my 705 have a connection problem-at only one angle-since I reinforced the plug. So I am looking for a replacement.

I have always run MD's with a barely audible threshold. I was also intrigued by the recent "threshold challenge" thread. So I want to keep it as low as possible.

Minelab does recommend 32ohms.
Argyle's info & advice makes perfect sense.
My research has found a variety of info::
-matching ohms is efficient and a good choice.
-ohm load and resistance affect power requirements-(draw on the battery.)
-a limiter is use full in controlling unwanted-loud peaks of sound (w or w/o an amp)

So I ask again--why do the high end headphones all have such a high ohm rating? There is a plethora of threads filled with a multitude of testimonials regarding the qualities of these phones BUT very little on-specifically- the ohm compatibility with the 705.

705 has a power regulator-so my battery draw question probably doesn't matter much. It also has a volume control for the phones so having independent volume controls on the phones would just be a personal choice. (I only use these controls when there is an abundance of loud surface signals in a given spot-since i don't have a limiter) Then I put them back -where I usually keep them-full volume.

I don't have a great understanding of electricity But I get the concept that proper load and resistance = efficiency.

While I look into this further I think I'll pick up a set of light weight 32 ohm phones from Kellyco -as a back up and for the summer heat.

Any other input would be welcome.

Thankyou


.

 

[argyle]

Not many like the Lightweights GT, as they move around a bit and you never get a true sound with them as they don't cup the ears properly. Kelkyco? Is that the mob that sell long range locators and the like ? I wouldn't be buying from them on the principal that we should be men and have no dealings with those that rip off the mentally challenged.

 

[GTzer]

Argyle- I'll probably end up with the RPG's and a light weight pair. The drawbacks you mention are known to me. Sometimes I'll use them anyway. Usually at quiet, open places that I can return to when it's not as hot .
Kellyco has been good to me. I went 29 yrs with my Whites before even looking at a detector so I wasn't really up on dealers and such.

Long range-dowsers and the like-not my choice-but seem to be a product that people seek and buy. Business wise-I guess it would make sense to carry items that people would buy.

Any way-I surely appreciate your info on the 32ohm phones. I wish some more folks would weigh in on the question I had about the expensive headphones using ohm rating of 100+.

Thanks,
GT

 

[argyle]

Those American made Detector Pro phones really are sweet, and the XTerra tones are nice to boot anyway so the match for you amongst the would be the ones that give you more pleasing sound to your hearing. When working with tone ID alone for shallow coins and jewellery in the first six inches, and if I don't think the area has any deep targets, I'll use one of Pro phones, another one, the Widow, I'll use in deep mushy ground like 100 year old disused and abandoned picnic grounds, usually by river and creeks. The reason for the higher ohm's use there is that ground is so quiet and so deep that its a pleasure to use the quality ones, as the threshold give is no different at depth between higher and lower ohm phones.
However, when I'm living on the threshold in very highly mineralized ground, which takes in most of my detecting, the RPG's rule. I've had hundreds of pairs if different phones over the years, the closest I came to RPG's was an old heavy pair of 8ohm's that were magical to use, but sadly lost them or left them somewhere.
It'd be good if you found a dealer that let you hear each phone, to pick the one that's sweet to your hearing.

 

[GTzer]

Thank you for the reply.
My ground is medium to highly mineralized. So it looks like the RPG's.
I'm also a full time musician so I'm into the tones and I'm learning the threshold tricks. Probably the best aspects of the 705. I was spoiled by the VID and depth accuracy of the Whites analog. On the 705 they are just an extra tool to use with the tones. I can deal with the TID but I wish that the depth was a little more accurate. Never needed a pinpointer with the Whites either.
Being familiar with compression, as a musician- I was intrigued by descriptions of a limiter. Perhaps in the future.
Thank for your time and info.

 

[n3umw]

An archived ratphone post lists the X70 as 230 ohms, I assume the 705 has not changed....

Here's Ratphones vs. the above. They are constant though the entire
audio spectrum:
<graphic>

Then there is Minelab. Their machines working better on low impedance
headphones is not correct. They ship Koss UR-30 phones with their
machines that say they are 100 ohms. Well since they are stereo that
means each speaker is 100 ohms. Minelab machine jacks connect stereo
phones in series. That means you are connecting 200 ohms to the machine.
So where is the low impedance?

Here is an impedance plot of Koss UR-30 headphones as connected to a
Minelab machine:
<graphic>

So it seems they ship 250 ohm headphones with their machines!


However, impedance matching alone does not make a good sound. If all
other variables are exactly the same, yes matching the machine gets you
more volume.
However, to increase impedance, you need more wire. This increases the
magnetic field with less current, but more wire means more weight in the
speaker diaphragm and you may end up with less volume. Then there is
magnet strength, diaphragm size and materials to consider.
In other words, he final judge will be your own ears. Some customers
actually like a loud distorted screech.

*KNOWN OUTPUT IMPEDANCES (OHMS)*:
Here is some machine impedances we have verified by either schematic or
testing:

_FISHER:
_1260: 220
1210: 100
CZ-70: 470
F-75: 274
ID Edge: 500

_TESORO: (Most all 150)
_CUTLASS II/BANDITO II uMAX: 150
SILVER SABER PLUS: 150
Silver saber: 150
GOLDEN SABER: 150
ELDORADO (NON-uMax): 180
GOLDEN uMax: 150

_TROY:
_SHADOW X2: 150
SHADOW X3/X5: 277

_Minelab_
Xterra: 230
Explorer SE: 150 (Varies from 130 to 170 with frequency)

NAUTILUS
150 ON HIGH CHANNEL, 47 ON LOW CHANNEL.

_WHITES_
6000DI: 470
3900: 300
GM III: 168
CLASSIC I: 220
MXT: 230
M6: 230

So let's review a few points:

1) Matching headphone impedance to machines is just a theoretical guideline.
2) Mono detector phone speakers are in parallel. So 150 ohm speakers
will make 75 ohm phones, on ANY machine.. Minus a little (or a lot)
wasted by the controls.
3) If you use true stereo phones, this is a special case. The speakers
STILL end up in parallel, however the manufacturer will spec the
impedance in ohms per side. On machines other than Minelab or Garret,
100 ohm per side stereo phones will end up at 50 ohms seen by the
machine. But on Minelab and Garret, the wiring in the machine puts
stereo phone speakers in series. In that case, 100 ohm per side stereo
phones will now become 200 ohm phones.


*Ratphones use 300 ohm speakers resulting in true 150 ohm total
impedance delivering more power to the speakers and match a wider range
of machines. They have less distortion and higher clarity. They will be
150 ohms on ANY machine at all frequencies. With our new wiring, the
controls do not load down the circuit at all. Note, this results in the
volume range of the controls to adjust from max down to about 1/4 volume
at minimum.*

 

[GTzer]

n3umw,
Wow-what a reply.Thank you..........let me digest this so that I may be able to give a better reply or ask some intelligent questions.
I'm obviously not a tech-but have sufficient knowledge when dealing with sound to utilize a proper ohm load for quality,efficient P.A. sound. I'll assume that the MD issue is more complex.

 

[argyle]

That's a load of theoretical nonsense. The lower ohm phone dominate on XTerra's. Just as they do on most detectors. You really have to watch making a quote like the one underneath. It's always amazed me that the more a man seems to know the theoretical side of something, the more helpless he is on practical application.

" Then there is Minelab. Their machines working better on low impedance headphones is not correct."

Hey n3umw....have you tried many various makes and models of phones in both the high and low ohms on any Minelab detectors, especially XTerra's? Have you ever actually used a metal detector ?

 

[MXTerer]

The higher the impedance of the headphones the less load on the audio circuit of the detector. Using a pair of killer bees at 150 ohms I can hear the threshold at "3". Using a pair of "32" ohm I have to increase my threshold to "8" in order to barely hear it. Circuit loading? Does it matter?

 

[Dingo Darnell]

The lower the impedance, the more efficient the 'phones, and the more battery life you'll get. If they want 32 ohms, I wouldn't go lower than 32 ohms. Besides, it might cause the amp to distort or run hot..