Hello, I’m trying to make a DIY wired bone conduction headphones for music listening/production to replace my Aftershokz bone conduction headphones.
I have a couple of small transducers (15mm) attached to a makeshift headphone case. I currently use this together with an audio interface.
I want to improve the sound quality and loudness - but I’m new to this and I’m not sure what I’m looking for. The sound currently has a lot of bass and high frequencies, and needs more midrange.
I was thinking it needs some sort of amplifier to increase the gain and an EQ (maybe a high pass filter/low cut filter).
I would appreciate any advice/tips on where to start - I also have a limited amount of experience with electronics. I’ve attached a photo of my current prototype. Thank you.
Awesome project idea! Most complex digital audio sources (computers and smartphones) will have a digital EQ built-in you could play around with that to see how you go.
If you want to take a more scientific approach you’d need a proper sound level metering setup so you can plot the frequency response of the drivers - or at least be methodical about playing with the audio response qualitatively.
Here’s a great research paper with some details on audio perception through bone conduction:
Once you’ve got something a bit more locked in, you coud set up a hardware EQ to improve the sound from the headphones
i was thinking of a active e.q of some description …browse the web for a 12 volt preamp…there are many out there that don’t cost the earth and there quite small devices in most cases.
.but i was wondering of your output audio level voltage if you know this …it would help in your equation
weather its simple low level or speaker voltage … …if it is speaker level and your just driving them to hard without realizing .i`d suggest put a 10 k resistor in the audio lines to cut the level down you may have to increase your input voltage somewhat,… but also try different values like 8.2 k or go higher etc…etc… just have a play around with the levels… you may find this an easier alternative…
Thank you Oliver! That research paper is excellent.
I’ve tried using digital EQ. Whilst it helped, it was changing the eq of the music rather than the headphones. A hardware eq could be more like what I’m after.
Do you mean to have sound level metering to measure the frequency response coming out of headphones? Just for further background, I currently use BAHA (bone anchored hearing aid) for daily use and don’t hear sound through air.
Thank you for the reply Brian, I’m going to look for active EQs and preamps.
I don’t quite understand the output audio level voltage though. Wouldn’t turning down the volume prevent it from driving too hard? Is there a benefit to adding a resistor in the audio lines?
Your project looks very cool!
From my understanding, the resistor will limit the current to the transducer and hence the power (speakers and transducers have a max-rated power that you have to take into consideration when designing the circuit).
Turning down the volume would prevent it although having extra safety factors is always good.
Thanks Liam, that makes a lot of sense.
I am curious about headphone impedance, and was wondering if it is important to know when making the headphones.