I spent a couple years instructing HPDE with the ubiquitous Chatterbox wired intercom. While they still have some use for me, I'm moving to the Sena 20S-01 bluetooth intercom system this season. These are quite spendy, but they came highly recommended by my peers.
Here's some of the details. First, unlike a wired intercom, you need multiple head units. The Amazon link I have on this page is for the "dual" package, everything you would need to outfit two helmets, yours and your student's.
One of my first objections to the Sena when I heard it discussed was of course the price. To paraphrase Vincent Vega, "A five dollar shake better be pretty f***ing good."
My second objection is that it doesn't lend itself to "grab and go". You have to spend a few minutes with the student's helmet first thing in the morning to get it set up. You can make this part of your morning "interview" if that works for you. I suggest doing the installation sitting down, with the helmet in your lap or on a work surface.
My third objection is a combination of the first two: I often work with two students all day long. I don't want to be forced to buy three of these things, and I don't want to use tools to swap them back and forth multiple times a day.
Fortunately, there's a solution to this last one - you can just buy another bracket with earpieces and microphone for about a third of the price of a whole unit.
With the extra clamp kit, you can just move the electronics package (photo, right) from helmet to helmet between sessions.
It comes off of the clamp with a button push, no tools required.
Incidentally, this is the part you want to take back to your hotel room to charge at night. It charges via a USB cord that is provided, but the kit does not come with a wall wart, you have to use your own universal USB charger, like an Anker.
The photo on the left is the back side of the Sena 20S clamp, clamped onto a note pad for clarity. This is what you'll be doing to your student's helmet in the morning.
Sena provides each clamp with a 2.5mm "Ikea wrench". It's adequate to the task, but since it's something you'll use a lot, spend $7 and get yourself a proper 2.5mm ball point hex wrench with a comfy handle and throw it in your kit.
One of the reasons I built this page (besides being greedy and selling ads) was that I didn't really understand how the pieces went together, and what to buy. It wasn't until I had the first Sena 20S-01 in my hands that I realized you could probably just buy another bracket to solve my "two students" conundrum.
One of the first things you end up doing is connecting your Senas one by one to an internet laptop and update the firmware. You do this using a (Windows) Device Manager app that you download from Sena. Once you've updated the firmware, you can also use that app to configure some settings to your liking.
Another way to access settings is via a Sena smartphone app.
Since the Sena is marketed for much more than intercom use, the user interface gets a little fiddly. I naively thought I could just memorize the few things I needed to know, and then go use it. At one point in the day, my first student said, "I hear music." The Sena was playing music from my iPhone. Buckled up in a car, I wasn't really sure how to kill it. I finally turned bluetooth off on my phone, and that did the trick.
Sitting in the paddock in the car chatting with my student on the Sena, I was dismayed with the latency. The Sena adds 150-200 mSec (I'm guessing) of latency to the conversation. If you've ever been on a Telcon where somebody has two mics (i.e. laptop and headset) going, you've heard this before; it's an echo that makes everything very hard to understand. Fortunately once you're out on track, the ambient (direct path) part of the conversation is so far down in the noise mix it becomes irrelevant. All you hear is the intercom.
All in all, the clarity is very very good. The one time I had difficulty hearing my student, I looked over at him finally and found his microphone had slipped and was below and in front of his full face helmet. When I had him tuck it back in, all was well.
I have yet to try "car to car" communication with this, like coaching a lead/follow. I think that will be very useful for those rare times when you get the opportunity.
I'll need to do a bit more homework on all of the various modes, including voice commands. Check back later for more impressions.
Update: I continue to struggle a bit when I have two students. I did end up buying another complete headseat, and I try to outfit my two students with a complete headset at the beginning of the day. The challenge is in transitioning back and forth between them. I have heard "Intercom fail" a bunch of times. I'm relatively certain it's doable, but in the frenzy of running car to car, I have many times resorted to "F*** it, I'm shouting and using hand signals." I might also simplify my life by just moving the pod between student helmets and see how that goes.
Other Sena Headsets
One of the ACGG instructors who was a fan of the Sena system said he uses the 20S-01 for his own helmet, and outfits his students with the cheaper Sena SMH5's. I actually initially bought a pair of those to emulate his strategy. After I saw how the 20S-01's worked, I set the SMH5's aside as spares.
If you're an instructor at one of my events and need to borrow an intercom system, hit me up and try the SMH5's.
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