Audio Systems/Vintage Headphone

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QUESTION: I have just bought a vintage pair of headphones, hybrid dynamic and electret, according to the manual they are rated at 2 X 8 ohms. Does this mean that they are 16 ohms?
The reason I ask is that my headphone amplifier manual says that the minimum headphone impedance is 16 ohms and below that could overload the amplifier output stage.

ANSWER: If they are really old/vintage, then perhaps they are not stereo, but mono and we would presume, then, the driver in each ear is wired in parallel giving a final impedance of 4 ohms.

If they are stereo, then it's likely each driver is 8 ohms or 8 ohms/channel. Then the driving amplifier should be able to drive into a 8 ohm or higher load.

But, either way, the load on the amplifier is less than 16 ohms. So, I would say you need to change the headphone amplifier.

If you could give me the model numbers for the phones and the headphone amp; thus allowing me to look up their technical specifications.  Then, we can get a definitive answer.

I look forward to your update on the amp and headphone so I can investigate more precisely.

Cheers.



---------- FOLLOW-UP ----------

QUESTION: The headphones are 80s Monarch ES 500s designed in America, made in Japan (they seem to be fairly rare, not much info about them), the headphone amp,a xDuoo Ta 02, with an upgraded, 4 amp regulated power supply.
I do have a rechargeable amp that would be compatible impedance wise, in theory, a Fiio E6, though it may not have enough power!
so will try that first, I also have a 75 ohm impedance adaptor, I could try, that plugs inline with headphones.
The headphones have not actually arrived from America yet, I am in the UK. They are due any day now.
I only paid $20 for them.
Thanks for your help.

Regards

Iain

ANSWER: The headphone is stereo with stereo connector at end of cord.  Therefore, as with most headphones of this era they use an 8 ohm coil in each ear piece.  Hence the load to the amp is rated at 8 ohms.  The electret tweeter element used for high frequencies is a higher impedance so they aren't an issue.

The tube amp is rated at 16 ohms but since it is a tube product loading it with an 8 ohm load should not be so bad. Long term it may cause some heating up of the tubes a small amount and the distortion might increase an imperceptible amount but, again, I don't see a problem with that.

Conclusion is while it may not be technically correct I think it will be safe for the tube amp to connect to the Monarch headphones. If it were a transistor amp the conclusion would have been 'no way'.

The 75 ohm impedance adapter does not sound like a good idea since these types of products are often not true high fidelity and may introduce deterioration of sound quality.

Let me hear back if you have further questions and let me know if you get good sound with the system!

Cheers.



---------- FOLLOW-UP ----------

QUESTION: The amp is a hybrid one, so it has a tube first stage and transistor output in Class A. So will not be compatible. The impedance adaptor does use audio grade components and I think it would be the safest option. It was designed to reduce the background noise when using low impedance In Ear Monitor headphones with a headphone amp. Which it does well.
I bought the headphones as I liked the look of them, getting them to work would be an added bonus.
My main full size headphones are an AKG Q701, a Jecklin Float Model 2 and a Precide Ergo Model 2.

Thanks for your help.

Regards

Iain

Answer
Wow, you are really into headphone listening.

Are the outputs transistors or FETs?  But, Maybe you have it backwards as it makes more sense  for the tubes to be at the output stage because audio purists don't like transistor sound.  Anyway, I am of the opinion you can drive the Monarch headphones without any particular trouble. Especially even if the outputs of the amp are FETs.  And the current draw is not so big so there is not high dissipation from heat.

And, Class A operation means the heat generation remains constant pretty much during music episodes so the potential degradation due to the impedance mismatch is not large.

But, if you are a true purist and want to be 100% right then swap amp/driver with one that is rated for 8 ohm loading.

Best wishes.  

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Cleggsan

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Audio Design Engineer; systems, loudspeakers, cd/dvd players, etc. I am knowledgeable in all high end audio equipment and installations. MAKE SURE YOU GIVE A MAKE AND MODEL NUMBER AND CAR IF IT IS AN AUTO QUESTION. Note: I am getting some who ask good questions that take a lot of time to research but then the questioner fails to read the answer. Please don't ask questions unless you are seriously looking for an answer. If you find an answer to your question otherwise then let me know with your reply. Thank you.

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Have been associated with audio design, standards, testing and component systems for over 40 years.

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Life Fellow Member of Audio Engineering Society Life Senior Member of Institute of Electronic and Electrical Engineers

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Review technical manuscripts for IEEE Spectrum Write occasionally for high-end audio publications

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BSEE/MSCS/MBA

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Past Employee/advisor to several well known audio products manufacturers

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