(Extremely Rare) Rotel RH-930 Back Electret headphones with adapter

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titana

titana

Forerunner
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These are very rare & AFAIK I am the only owner of this unique headphone.
I am quoting my own impressions so that people can get an idea about these headphones since the information about these is nearly non existent on web.

Here is a rather unique & rare planar headphone : Rotel RH-930 back-electret headphones.
This is an OEM version of Toshiba ?HR-910.?
The wikiphonia entry suggests 910 but the pics on this japanese site are suggest hat it is OEM version of HR-810.

The transformer is built into the TRS plug & so it can be used with usual dynamic amplifiers.
The driver is 65 mm. No backwave damping here.
Most electrets are considered infereior to the 'electrostats' but back-electrets are a bit different. Check this wikiphonia link for electret driver principle:

From an engineering standpoint, the ideal diaphragm material is a polyester called boPET, biaxially-oriented polyethylene terephthalate film, aka Mylar or Hostaphan or Melinex. Problem is, boPET doesn't make a very good electret. So an engineer must either accept a compromise in the sound, or he can re-engineer the typical electrostatic headphone layout by metallizing a boPET diaphragm and applying the audio signal to it and relegating the electret material to the stators where its inferior mechanical properties won't matter. This inside-out or back-electret design was used by only two manufacturers: Toshiba (most notably the HR 910; Rotel also marketed an OEM model) and Audio-Technica (the ATH-8, aka the Signet TK33).
Click to expand...

About the Sound :
The first thing that struck me was how smooth they were in mids & treble. I can't seem to pick any major peak/dip in there frequency response.I can play them as loud as I can from my amp & they don't get shouty.
The Treble is very extended & without a hint of that plasticky sound that seems to bug most dynamic cans.
In the stock form they have significant bass roll-off starting from 175 Hz & lower meaning that one would miss the mid-bass & that the male vocals sounded a bit thin.
I improved the backwave seal of the cans & that has cured the vocals. The bass still rolls off but most of it is now in sub-bass region & doesn't hurt the the timbre of most instruments.
Pressing a bit on the earcups improves the sub-bass too which suggest that experiments with better sealing earpads are in the order.
Click to expand...

Head-fi thread about back-electrets

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Price : Rs. 7k + shipping

This should be of special interest to people who have been wanting to try out electrostatic headphones but have been put off either by price or by the need for a separate electrostatic amplifier/adapter.
 
^ Looks tempting ! :D Will an Audinst HUDMX1 on high gain setting be able to drive them ? Does the bass atleast have a little kick and thump ? Also a comparison to any mid-high end headphones would be really helpful to know where exactly they stand . As in I would like to know if these would be better than a modded AH-D5000 ,Grado SR225i or should these be of interest to me because they are eletrostats and offer a different sound sig ?

Hope you don't mind answering the questions of a curious mind ;).
 
The adapter has 3 settings : low , medium & high.

On the low setting any decent headphone amp should be able to power them( I have tried them on xonar stx apart from EHHA)

Electrostats are known to not have bass thump unlike dynamic headphones & this one is no different. What they do have is a incredibly smooth, grain free sound.

The treble is among the best I have heard in any headphone regardless of price. Mids are crystal clear too. Bass is tight & textured but the sub-bass is rolled off which does affect the timbre of bass instruments.

Apart from the bass, I liked them enough to decide that I must have a full electrostatic rig of my own to complement my orthos. My wallet isn't thankful though & that's why some of these recent sales. :(
 
WOw a 1975 Head Gear...you surely must be the one of very few owning them in India,if only. (Got a confirmation from a person from Mumbai under userid gurubhai on head-fi.org who has this in India)

Anyways can you tell the minimum amp required to drive these beauties.

Interested hence asking..
 
gurubhai is not from mumbai, I ought to know. :)

I already answered the amping requirements query when I replied to Faheem. Check it a above.
 
titana said:
gurubhai is not from mumbai, I ought to know. :)

I already answered the amping requirements query when I replied to Faheem. Check it a above.
Click to expand...

This is BECAUSE YOU ARE GURUBHAI !!!!!!I got confused from PM from YOU ARE THE ONLY OWNER OF THESE...:D :D :D

i WANT THESE..!!!!!Please allow my stupidity!!! I actually got confused between 2 forums PM from AudioForums.com and head-fi.

Give me a day to research..! I am sooo interested i cannot tell...

Edit/Add: What kind of amp will it require to power on high settings.I mean woulnt it defeat the purpose if one buys this and always keep this on low setting.Its like buying a Ferrari and never getting past 1st gear.And please you audiophile freaking grease monkey :) talk english that i can understand. My Audiophile knowledge is limited to onboard motherboard .
 
For High gain setting it should be a powerful speaker amplifier.

I have tried the high setting on my marantz AV receiver & the bass does improve a bit from its Low gain setting.Someone with a power amp would probably get even better results.

Apart from the bass roll-off, these sound pretty exceptional since such smoothness & clarity is never seen in this price bracket.

However, if you are planning to run these of onboard HP outs then I wouldn't recommend these to you.
 
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