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 $15 (+ $10 shipping) that came with a 6.3mm tip left stereo plug and a 300 Ohm pair utilizing the older TDH-39 elements for $9.99 (+ $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 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 and TDH-49P 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 and its cousins the TDH-49P and TDH-50P were originally designed for and are 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, replacement parts can be hard to get as only medical/audiometric supply companies carry them and they are not cheap. This is probably a symptom of the overall cost problem of the medical industry (think EpiPen and Insulin). Parts are expensive because they can be due to very little competition. A set of TDH-39 headset audio cables (M745TL, CO-19B, CO-19R or CO-19TR for example) that should probably cost around $15 sell for $40 and up because the price will ultimately be borne by the patients and the insurance companies. In fact, a Google search shows new Audiocups without TDH-39P elements range from $295 up to $350, with one list priced at $1467.45 (I’ll be happy to sell you one of my pair with TDH-39P elements for only $1000, shipping included!). Compare this to used eBay prices with TDH-39P elements which usually run in the range of $25 to $40 with shipping. Some medical supply vendors do not even post prices. You place your order with them and they invoice you for the total price.

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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 for $6.95 each (free shipping).

	10 Ohm Telephonics TDH-39P Headset Madsen branded Audio Cable TDH-39P 296D000-1 Elements MX-41/AR Cushions, NSN 5965-01-331-8708 This is a 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). As with the TDH-49P above, the elements are removed from the HB-7 headband and are installed in the Audiocups assembly. Refer to the Audiocups assembly instructions for more information. This TDH-39P headset was acquired on eBay for $16.99.

	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). As with the other headsets above, the elements are removed from the headband (by removing the ear cushions) and are installed in the Audiocups assembly. Refer to the Audiocups assembly instructions for more information. This MAICO MA20 TDH-39P headset was acquired on eBay for $1.25 + $5.66 shipping.

	10 Ohm Maico AR-100 “Auraldomes” Headset with TDH-39 Elements This is a Maico AR-100 “Auraldomes” headset with 10 Ohm TDH-39 elements. The old worn out cushions were replaced with new David Clark 18316G-02 Foam Ear Seals. 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 1mm hex wrench is required for the set screws. The patent describing the “Auraldomes” headset can be viewed here. This “Auraldomes” headset was acquired on eBay for $21.49 + $13.00 shipping.

	300 Ohm AR-200 “Auraldome II” Headset with TDH-39 Elements This is an 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. This “Auraldome II” headset was acquired on eBay for $25.00.

	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-196F 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 /AR for 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 and are lighter in weight.

Links To Other Resources

A PDF document about various commercial headphones I have

Last modified May 20, 2023