Intercom headset with telecoil

ShowNet

Member
I'm hearing-impaired, deaf in one hear and a behind-the-ear hearing-aid in the other.

I'm finally biting the bullet and looking at ordering/making a custom Clearcom/Telex headset that includes a telecoil, which feeds the audio directly into the hearing aid, bypassing the speaker/microphone and resulting in much clearer sound.

I have three somewhat related questions:

- Has anyone ever added a telecoil to an existing headset? I'm looking at scavenging a telecoil from an existing telecoil-only ear piece (like these: https://www.amazon.com/dp/B000TJUOVM/?tag=controlbooth-20). I'm hoping I can solder it in parallel to the headset speaker. Any thoughts why that wouldn't work? Perhaps it would add too much resistance or something?

- Any favorite lightweight, single ear headsets that completely fit over the ear. Most lightweight headsets sit directly on the ear, which doesn't work for me - my hearing aid microphone is "above my ear," as it were. I know typical medium-to-heavy weight headsets do fit, but they are, well, heavy.

- Last resort, I'm looking at converting this Plantronics H251 phone headset that already has a telecoil embedded. https://headsetplus.com/product1693/product_info.html
However, I'm 90% sure that headset has an electret microphone, while I believe intercom headsets use dynamic mics. Using the dangerously little electronics knowledge I have, I'm hoping to follow the conversion steps listed here: http://www.matgoebel.com/projects/headset
Any thoughts why that might not work?

Thanks for any help!
 
It should work and is worth a try. Choose a telecoil that does not have a coiled cable. Coiled cable wires are extremely difficult to solder. The simple and fast way to do this would be to solder the telecoil cable into the headset's XLR connector. Disconnect one side of the headset speaker by de-soldering and insulating it with tape or heat-shrink tubing. Don't try to drive both the speaker and telecoil at the same time because it will drop the load impedance.

Telecoils are made in mono and stereo, and the plug shows what type it is. A mono one will have a two conductor, tip-sleeve plug. Since the beltpack is mono, you can use a neck loop, which would be more convenient than coils on both your ears. Mono will be easier to wire.

On a stereo telecoil, you'll find that both coils share a common connection to the plug's sleeve, and the other side of the coils go to tip and ring. For the beltpack's mono output, wire the telecoil's tip and ring together to one side of the amp and the sleeve to the other.

The only potential problem I see is the output impedance of the amplifier in the belt pack. The telecoil could be fairly low impedance, like 8 ohms, which takes a fair amount of current to drive. The amplifier is happiest when it is the same impedance or lower than the load. The manufacturers don't list the output impedance of their beltpacks, but I see a few headsets specified to be 40-300 ohms, which means the amplifier impedance could be too high to drive an 8 ohm load well. If you can't get the telecoil to be loud enough, or the sound is distorted, then buy one of the amplified models, which requires a battery.

If you want to get fancy, have an understanding of circuits, and good soldering skills, consider getting a switching jack to match the plug on the telecoil, either tip-sleeve mono, or tip-ring-sleeve stereo. Buy a jack that can fasten inside the beltpack case with a nut and washer. Wire it so it disconnects one side of the amp from the headset XLR jack when a plug is inserted. That way, unplugging the telecoil makes the system work normally. If the XLR is board mounted, it will require cutting traces on the circuit board. I try to do this sort of mod so it can be undone with minimal harm, by scraping varnish off the cut trace and bridging with fine wire and solder.
 
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Check with ProIntercom http://prointercomllc.com/ They are a smaller company that make a lot of cool clear-com compatible gear at great competitive rates. They used to be known as Production Intercom. They make a midweight headset with a fairly large wrap around earpiece that might work for you.

But that's not all, my dealings with them have been great and I just have a feeling they might be willing to help you adapt one of their products to work with a telecoil. Maybe not, but they seem like the kind of people that might. I would give them a call and ask if they have ever considered creating a telecoil compatible product and say that you are thinking about trying to build your own and just see if there is anything they can do to help you through the process

If that doesn't work stick around and be friendly to my @FMEng above he's a pretty cool helpful guy who knows his electronics and can probably help you through this if you get stuck.
 
Check with ProIntercom http://prointercomllc.com/ They are a smaller company that make a lot of cool clear-com compatible gear at great competitive rates. They used to be known as Production Intercom. They make a midweight headset with a fairly large wrap around earpiece that might work for you. My dealings with them have been great and I for some reason just have a feeling they might be willing to help you adapter one of their products to work. Maybe not, but they just really seem like a pretty good company that might. I would give them a call and ask if they have ever considered creating a telecoil compatible product and say that you are thinking about trying to build your own and just see if there is anything they can do to help.


If that doesn't work stick around and be friendly to @FMEng above he's a pretty cool helpful guy who knows his electronics and can probably help you through this if you get stuck.
@ShowNet and @gafftaper Posting in full agreement and praising Production Intercom from their original incarnation.
Toodleoo!
Ron Hebbard
 
Thanks @FMEng ! Greatly appreciate the response. I think there might be a discrepancy in how we're visualizing it, but it doesn't change the fundamentals.

My thinking was to ideally implant a telecoil component inside the actual headset, directly above the headset speaker (literally just the coiled copper part). If I'm following your description properly, it sounds like you were envisioning doing the wiring down by the XLR connector. Since I need the telecoil directly by my hearing aid, millimeters away, I think your're suggesting I take the telecoil ear piece I linked to on Amazon, and run that as an entirely separate cable, then patch it into the XLR. Does that sound right? That would work, but isn't the most elegant and I actually hate those ear hooks (snagging the cable is liable to slice my ear off).

Either way, it doesn't change one concern I had, about driving both a speaker and the telecoil simultaneously. It sounds like it's unlikely to work -- is there a way it can be made to work? The optimal audio device for me changes based on a variety of factors, the most obvious being times where telecoil mode picks up too much interference and I have no choice but to rely on speaker. Is having the speaker and and telecoil wired in parallel not feasible even with circuit modifications? Perhaps I could run 6 conductor cabling to the headset, 2 for mic, 2 for speaker, and 2 for telecoil. Somewhere, possible a second empty beltpack, I could add a battery, amp, switch, etc to drive both, either switched or simultaneously. Does that seem plausible?

Just to clarify a few things, I only need one mono telecoil (just one hearing aid), and everything I'm doing is upstream of the theater's beltpack (which changes depending on venue, wired, and wireless beltpacks). Also using a neckloop is an option, but at the moment I'm looking into adapting a neckloop setup for use with Motorola radios, which is a whole 'nother project...

@gafftaper Thanks for the ProIntercom suggestion! I knew there was a company that was well regarded and had changed names/hands, but couldn't remember their name. I will reach out to them! The one concern I have is how they can test their work without having a hearing aid laying around, but perhaps an audio company would have something that can be made to work.
 
Good Luck @ShowNet and keep us posted on how it goes. It's kind of surprising that there isn't already a solution. There are a lot of stage hands out there who have spent way to many hours working on concerts without any hearing protection, you are far from the only person with this need.
 
Now I get your idea of mounting the coil in the headset. That changes things a bit. Rather than making the connections in the XLR, I would do it in the headset speaker. Try wiring the telecoil in series with the speaker, which will reduce the load on the amp. It will reduce the maximum volume a bit, but it might be plenty.

It's hard to know how well it'll work so it might be a good idea to scab it together to test it in such a way that you can restore the headset to normal, before doing something like drilling a hole for the cable, applying glue and such.
 
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Now I get your idea of mounting the coil in the headset. That changes things a bit. Rather than making the connections in the XLR, I would do it in the headset speaker. Try wiring the telecoil in series with the speaker, which will reduce the load on the amp. It will reduce the maximum volume a bit, but it might be plenty.

It's hard to know how well it'll work so it might be a good idea to scab it together to test it in such a way that you can restore the headset to normal, before doing something like drilling a hole for the cable, applying glue and such.
@FMEng @TimMc As a poster who knows only enough of hearing aids to be dangerous I have the following queries and train of thought.
1; If a normal in-ear hearing aid includes a tele-coil feature, will it automatically switch if / when in a venue with a magnetically coupled induction loop or does the wearer have to consciously switch to the tele-coil then remember to switch back again?
I guess my query #1 is really are the only choices either / or OR is there an auto-switching option AND is there ever an occasion when both choices are simultaneously active??
Which brings me to query #2, my REAL query.
2; If @ShowNet proceeds with his plan to house a tele-coil transmitter (source induction coil) within the housing of his ear enclosing headphone, whether he connects his coil in series (preferred) or in parallel with his headset's normal acoustic driver / diaphragm is there any need to pay attention to relative polarity of the two sources to ensure there's no, or minimal, cancellation between them??? @FMEng @TimMc @JohnD @MNicolai @NickVon @jayvee ??? Have any of you any thoughts????
Toodleoo!
Ron Hebbard
 
#2, my REAL query.
2; If @ShowNet proceeds with his plan to house a tele-coil transmitter (source induction coil) within the housing of his ear enclosing headphone, whether he connects his coil in series (preferred) or in parallel with his headset's normal acoustic driver / diaphragm is there any need to pay attention to relative polarity of the two sources to ensure there's no, or minimal, cancellation between them??? @FMEng @TimMc @JohnD @MNicolai @NickVon @jayvee ??? Have any of you any thoughts????
Toodleoo!
Ron Hebbard

That's an interesting question. I assume the hearing aid has a switch to activate telecoil mode and disable its mic. If so, does the hearing aid pick up anything from the headset when in telecoil mode? If so, there's enough of a magnetic field from the headset speaker to worry about phase cancelling. From there, it's a matter of testing with the polarity of the connections both ways.

Another thought is maybe telecoil mode would work with induction from the speaker, without any modifications.
 
@FMEng @TimMc As a poster who knows only enough of hearing aids to be dangerous I have the following queries and train of thought.
1; If a normal in-ear hearing aid includes a tele-coil feature, will it automatically switch if / when in a venue with a magnetically coupled induction loop or does the wearer have to consciously switch to the tele-coil then remember to switch back again?
I guess my query #1 is really are the only choices either / or OR is there an auto-switching option AND is there ever an occasion when both choices are simultaneously active??
Which brings me to query #2, my REAL query.
2; If @ShowNet proceeds with his plan to house a tele-coil transmitter (source induction coil) within the housing of his ear enclosing headphone, whether he connects his coil in series (preferred) or in parallel with his headset's normal acoustic driver / diaphragm is there any need to pay attention to relative polarity of the two sources to ensure there's no, or minimal, cancellation between them??? @FMEng @TimMc @JohnD @MNicolai @NickVon @jayvee ??? Have any of you any thoughts????
Toodleoo!
Ron Hebbard
I honestly don't know. I'm following because I'm nearly in the same situation as the OP - I am completely deaf in one ear and the other ear has tinnitus and loss that has become untenable. I'll be getting a hearing aid for Early Christmas and would love to be as functional as possible for work so I can see it as a boon and not a hindrance.
 
1; If a normal in-ear hearing aid includes a tele-coil feature, will it automatically switch if / when in a venue with a magnetically coupled induction loop or does the wearer have to consciously switch to the tele-coil then remember to switch back again?
I guess my query #1 is really are the only choices either / or OR is there an auto-switching option AND is there ever an occasion when both choices are simultaneously active??

Hearing aids will not normally automatically switch into telecoil mode. There is a "telephone" option some have where they automatically switch if they sense a phone is by the ear. I've left that option off, as I prefer manual control.

My hearing aid has 5 different programmable programs I can select from and customize. My programs include normal, T-coil only, t-coil with microphone, and a couple others customized listening settings. If I'm using t-coil, 90% of the time I want both t-coil and microphone together, because if I'm in t-coil-only I ONLY hear the t-coil. Even too-snug completely noise-blocking headsets can be problematic. The only time I want t-coil-only is usually in very loud scenes or concerts. Fun fact, it's entirely possible for me to use a phone in front of a stack of speakers at 120dB. Not so great for the person on the other end of the line though...

2; If @ShowNet proceeds with his plan to house a tele-coil transmitter (source induction coil) within the housing of his ear enclosing headphone .... is there any need to pay attention to relative polarity of the two sources to ensure there's no, or minimal, cancellation between them???

That is an interesting question.. @FMEng is right, there is a magnetic field from the headset speaker that my hearing aid *sometimes* picks up. Usually it's too weak for me to do anything with it. Cell phones are an easy case where there would be both an active speaker and an active t-coil, and in thinking about it there's few if any times I've used a phone in the combo mode setting; if it's loud enough I need the telecoil for a phone call, it's usually easier to just switch to t-coil-only mode. This will take some experimenting on my part to see how well both together work.

@jayvee As of tomorrow, I will have a brand new Oticon Dynamo - https://www.oticon.com/solutions/dynamo
 
Thanks for your help and interest everyone! An FYI, I'm about to start load-in on Monday (I really should have started this project a month ago). I've ordered a Pro Intercom headset, I've also ordered a simple Telex basestation and beltpack off of Ebay. And last week I received the Plantronics H251 phone headset with built-in telecoil. That's actually going to be the first thing I'm going to try, as I don't expect the Pro Intercom headset until next week sometime. I will, of course, posts what does and doesn't work...
 
Hearing aids will not normally automatically switch into telecoil mode. There is a "telephone" option some have where they automatically switch if they sense a phone is by the ear. I've left that option off, as I prefer manual control.

My hearing aid has 5 different programmable programs I can select from and customize. My programs include normal, T-coil only, t-coil with microphone, and a couple others customized listening settings. If I'm using t-coil, 90% of the time I want both t-coil and microphone together, because if I'm in t-coil-only I ONLY hear the t-coil. Even too-snug completely noise-blocking headsets can be problematic. The only time I want t-coil-only is usually in very loud scenes or concerts. Fun fact, it's entirely possible for me to use a phone in front of a stack of speakers at 120dB. Not so great for the person on the other end of the line though...



That is an interesting question.. @FMEng is right, there is a magnetic field from the headset speaker that my hearing aid *sometimes* picks up. Usually it's too weak for me to do anything with it. Cell phones are an easy case where there would be both an active speaker and an active t-coil, and in thinking about it there's few if any times I've used a phone in the combo mode setting; if it's loud enough I need the telecoil for a phone call, it's usually easier to just switch to t-coil-only mode. This will take some experimenting on my part to see how well both together work.

@jayvee As of tomorrow, I will have a brand new Oticon Dynamo - https://www.oticon.com/solutions/dynamo

Oooooooooooooooooooooooo
 
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Thanks for your help and interest everyone! An FYI, I'm about to start load-in on Monday (I really should have started this project a month ago). I've ordered a Pro Intercom headset, I've also ordered a simple Telex basestation and beltpack off of Ebay. And last week I received the Plantronics H251 phone headset with built-in telecoil. That's actually going to be the first thing I'm going to try, as I don't expect the Pro Intercom headset until next week sometime. I will, of course, posts what does and doesn't work...
I'm really enjoying following this discussion. Good luck!
 
@ShowNet , I talked to the people from Pro Intercom at LDI. They are resellers of Listen Audio's wireless devices. She (the owner of P. I.) said that Listen makes a loop that she was pretty sure you could use with their wired gear. Give them a call for details of what products and how.
 
@ShowNet , I talked to the people from Pro Intercom at LDI. They are resellers of Listen Audio's wireless devices. She (the owner of P. I.) said that Listen makes a loop that she was pretty sure you could use with their wired gear. Give them a call for details of what products and how.

Thanks @gafftaper ! Appreciate it! I'm in the midst of tech now, so have been slow to respond. As it turns out, the Pro Intercom SMH310 has a pretty strong telecoil affect un-modified. I'd like to see if it can be stronger, but it's pretty good for now. Wearing it for hours at a time isn't too comfortable, so I still intend to try with the lightweight telephone headset I purchased (with built-in telecoil).

In related news, I have my Motorola XPR 7550 radio working via bluetooth to my wireless "streamer" device - I'm wearing a loop device that is a bluetooth receiver and streams directly to my hearing aid. It sounds fantastic. It's not perfect - I don't have volume control. But it's way better than a traditional remote mic (which I still use for the microphone portion).

All-in all, I'm 85% of the way to what I'm looking for. Once we're out of tech and rehearsals I'll take another stab at different headsets.

Thanks!
 
*bump* How's this project going? I'll be getting fitted for a Phonak CROS B in the first week of January and am curious about how this is going!
 

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