Audiometric Headphones

In the Fall of 2009, I picked up two pairs of Amplivox Audiocups headphones on eBay; a 10 Ohm pair utilizing TDH-39P elements for USD$15 (+ USD$10 shipping) that came with a 6.3mm tip left stereo plug and a 300 Ohm pair utilizing the older TDH-39 elements for USD$9.99 (+ USD$11.27 shipping) that came with a DB9 plug. I was interested in obtaining a pair of Audiocups because I was looking for a set of passive headphones that I could use in a very noisy environment for two-way radio communications. I figured anything that could provide a quiet environment for hearing tests could do the job and comments from others who have used them this way confirmed my assumption. As these were originally designed for use with audiometers, there are many different types of plugs and wiring configurations available so it was just luck that the first set had a common type audio plug. Some have DIN plugs for use with devices such as the Medelec/Teca Synergy EMG/EP Monitoring System. Some have a DB9 connector which is used with a Cadwell 5200A EMG unit. Some have a single 6.3mm stereo plug (wired either tip left or tip right depending on the audiometer it is to be used with) and others come with two 6.3mm monaural plugs, one for each audio channel (a Hosa YPP-117 adapter can be used to combine the individual monaural plugs into a single stereo plug). For the DB9 connector, it was a simple matter to make an adapter that converts the DB9 connector (pin 4 - left channel, pin 5 - right channel and pin 9 - common) to a 6.3mm stereo plug (tip left, ring right and sleeve common). I had considered removing the DB9 connector and replacing it with a 6.3mm connector but it is installed so well with heat shrink tubing around each individual DB9 connection that it seemed a shame to destroy it. Also, the DB9 connector connects securely and the configuration allows me to use different types of audio plugs by simply creating a new dongle with a DB9 connector. The Audiocups are indeed very quiet and I have found them to be quite useful in blocking out just about all exterior noise.

As noted above, Audiocups were designed for hearing testing and the Telephonics TDH (Telephonics Dynamic Headphone) series TDH-39, TDH-39P, TDH-49P and TDH-50P headset elements that are used with Audiocups have a relatively flat frequency response up to 8 kHz (see TDH series specifications). They work okay for music, and I have used them for that purpose, but commercial headphones designed specifically for listening to music would have better upper end frequency response. I should note that before they were adopted as the standard for hearing testing, the Telephonics TDH-39 headset was originally designed for and is still used on some aircraft for radio communications. The MX-41/AR (NSN 5965-01-331-8708) cushions used with these headsets were originally used on military aircraft with headsets such as the HS-23 and HS-33 (see MX-41/AR below).

Unfortunately, most replacement parts can be hard to get as only medical/audiometric supply companies carry them and they are not cheap. About the only part that has gotten relatively inexpensive lately is headphone cables for TDH-39 and TDH-49 elements. Cables with separate monaural connectors for left and right channels are now available for under USD$20.

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Headsets and Components

	10 Ohm Audiocups Headset Switchcraft branded Audio Cable: M745TL - Tip Left TDH-39P 296D000-1 Elements MX-41/AR Cushions, NSN 5965-01-331-8708



	300 Ohm Audiocups Headset DB9 Audio Cable: Pin 4 = Left, Pin 5 = Right, Pin 9 = Common (Originally used with a Cadwell 5200A EMG Unit) TDH-39 296D000-2 Elements MX-41/AR Cushions, NSN 5965-01-331-8708



	10 Ohm Medelec Co-Branded Telephonics TDH-49P Headset 5-pin 180° DIN Audio Cable: Pins 1 & 3 = Right, 4 & 5 = Left TDH-49P Elements 296D100-1 Telephonics 510C017-1 (Type 51) Cushions, NSN 5965-00-280-3607 The elements of the Telephonics TDH headset, such as this TDH-49P, are used with Audiocups. The elements are removed from the Telephonics headband and are installed in the Audiocups assembly. Refer to the Audiocups assembly instructions for more information. Two sets of these TDH-49P headsets were acquired on eBay in August 2009 for USD$6.95 each (free shipping).



	10 Ohm Madsen TDH-39P Headset Madsen branded Audio Cable TDH-39P 296D000-1 Elements MX-41/AR Cushions, NSN 5965-01-331-8708 This is a Madsen TDH-39P headset using a Wilfan Electronics HB-7 headband and Wilfan Electronics one-piece MX/41-AR cushions (standard MX-41/AR cushions are two-piece). This Madsen TDH-39P headset was acquired on eBay in September 2010 USD$7.99 + USD$9.00 shipping.



	10 Ohm Madsen TDH-39P Headset Madsen branded Audio Cable TDH-39P 296D000-1 Elements RadioEar item #8507196 Red and Blue Type 51 cushions This is a Madsen TDH-39P headset using a Wilfan Electronics HB-7 headband and RadioEar item #8507196 Red and Blue Type 51. This Madsen TDH-39P headset was purchased on eBay in October 2012 for USD$9.99 + USD$10.00 shipping.



	10 Ohm MAICO TDH-39P Headset for MA20 Audiometer MAICO branded Audio Cable TDH-39P 296D000-1 Elements Telephonics 510C017-1 (Type 51) Cushions This is a MAICO branded TDH-39P headset using a MAICO headband and Telephonics 510C017-1 (Type 51) Cushions (NSN 5965-00-280-3607). The elements are removed from the headband by removing the ear cushions and then removing the TDH-39P elements from the shells. This MAICO MA20 TDH-39P headset was acquired on eBay in May 2012 for USD$1.25 + USD$5.66 shipping.



	10 Ohm Qualitone TDH-39P Headset for Qualitone Acoustic Appraiser Audiometer TDH-39P 296D000-1 Elements Pierce-Roberts Red and Blue MX-41/AR Cushions This is a Qualitone branded TDH-39P headset using a Telex headband and Pierce-Roberts Red and Blue MX-41/AR Cushions. This Qualitone TDH-39P headset was acquired on eBay in June 2024 for USD$15.00 + USD$8.99 shipping.



	10 Ohm Maico “Auraldomes” Headset with TDH-39 Elements This is a Maico “Auraldomes” headset with 10 Ohm TDH-39 elements. The old worn out cushions were replaced with new David Clark 18316G-02 Foam Ear Seals and the dome filters with David Clark 24505P-02 Dome Filters. They do a superb job of blocking outside noise and I use them at my office when noise from the various servers in the office gets very loud. The audio cable is a standard TDH type cable and a 0.9mm hex wrench is required for the set screws. The patent describing the “Auraldomes” headset can be viewed here. A 1964 advertisement for Maico “Auraldomes” can be viewed here. This “Auraldomes” headset was acquired on eBay in February 2016 for USD$21.49 + USD$13.00 shipping.



	To make the “Auraldomes” shown above more comfortable and provide better noise isolation, KORE AVIATION Ultra Plush Silicone Gel Ear Seals were later used to replace the David Clark 18316G-02 Foam Ear Seals and an M745TL audio cable replaced the old worn out cloth covered cable.



	10 Ohm AR-100 “Auraldomes” Headset with TDH-49P Elements Several years after the Maico “Auraldomes” shown above were acquired, these newer Aural Research AR-100 “Auraldomes” were acquired new-in-box without audio elements or cable on eBay in June 2020 for USD$25 + USD$7.00 shipping. TDH-49P elements from one of my Medelec headsets and a M745TL tip-left stereo plug cable were added along with David Clark 40863G-02 Gel Ear Seals and David Clark 24505P-02 Dome Filters to replace the old parts that had deteriorated over 41 years of sitting on a shelf. Original AR-100 “Auraldomes” Installation Instructions that were in the box are available here.



	300 Ohm AR-200 “Auraldome II” Headset with TDH-39 Elements This is an Aural Research AR-200 “Auraldome II” headset with 300 Ohm TDH-39 elements. It is an upgraded version of the original “Auraldomes” headset above. It uses a DB9 connector that is wired for a Cadwell 5200A EMG Unit (Pin 4 = Left, Pin 5 = Right, Pin 9 = Common). Due to its age, the foam dome filters had turned into a sticky tar-like substance and required replacement with new David Clark 24505P-02 Dome Filters. The patent describing the “Auraldome II” headset can be viewed here. A 1978 advertisement for the Aural Research “Auraldome II” can be viewed here. This “Auraldome II” headset was acquired on eBay in September 2016 for USD$25.00 + USD$21.42 shipping.



	MX-41/AR Cushions (NSN 5965-01-331-8708) Standard black MX-41/AR cushions (NSN 5965-01-331-8708) as well as red and blue varieties used with audiometric headsets (click on the picture for a larger view). These are some samples that the Pierce-Roberts Rubber Company generously provided me so that I could repair two classic military headsets that had old damaged MX-41/AR cushions. One headset had the standard black variety and the other headset had one red cushion and one blue cushion. MX-41/AR is a Joint Electronics Type Designation System (JETDS) MIL-STD-196G designator; Unit indicator MX for Miscellaneous (equipment not otherwise classified in the JETDS), 41 for the forty-first unit designated as miscellaneous in the JETDS and equipment indicator /AR for Piloted Aircraft Radio.



	300 Ohm Telephonics TDH-39 296D000-2 Elements These are a pair of 300 Ohm Telephonics TDH-39 296D000-2 elements (NSN 5965-00-464-6191) that were removed from surplus equipment. It should be noted that these are the older metal TDH-39 elements. The newer TDH-39P elements have a plastic body instead of a metal body, which is a considered safer, and are lighter in weight. There was a concern that the metal shells posed a safety hazard which may be the reason these TDH-39’s have what appears to be a ground wire added to the metal components.



	TDH Element Grub Screws TDH series headphone elements use two grub screws to secure the headset cable to the element. A headset requires a total of four grub screws. Sometimes the screws get lost or the screw head gets stripped requiring replacement. Official replacements tend to be very expensive with the cheapest price found being USD$7.90 for a pair of two screws on AliExpress. However, they are nothing more than stainless flat-end M2 x 0.4 x 3 grub screws (2mm diameter, 0.4mm pitch, 3mm long). A pack of 50 can be obtained for less than USD$5.00. One can choose either slotted head, typically used with TDH elements, or 0.9mm hex head, used with RadioEar DD45 elements. Either one can be used with the other as they are interchangeable. The hex head screws are easier to work with and require an easily obtainable 0.9mm hex driver.

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Last modified August 16, 2024