[tractorguy]

I am new to this forum and being not very electronically savvy I was hoping with all of the experience out there someone could help me with my project.  I spend a lot of time on tractors mowing and brush-hogging fields and given the noise of the diesel engine and the mower deck I always wear ear protection.  I also like to listen to audio-books during this somewhat mind-numbing work and presently use custom molded ear inserts with transducers that I also use in my race car.  The ear molds alone are not enough to protect my ears from the noise from the tractor so I also use a set of muffs over them.  The problem is that after many hours on the tractor my ear canals become quite uncomfortable.
 
So I thought I would make a headset using a comfortable, industrial type earmuffs ( Howard Leight, Leightning Thunder T3 : NRR=30)  into which I inserted a set of old Sony Walkman type speakers (24 Ohm impedance).  These work great at low noise levels but at higher levels, when the tractor is at mowing rpm, I cannot quite hear the audio-book despite turning up the MP3 volume to the maximum setting.  I am playing the audio-books on a Creative ZEN Mosaic EZ100 MP3 player.  I could not find any specs on the output of the MP3, but I do have the ability to limit the volume on this player and have made sure that it is set to the max.  I suspect that I need speakers of a different impedance...presumably something under 24 Ohm.  Of course, I do have the ability to turn down the volume setting on the MP3.  I also assume that these speakers, as with most out there, are designed such that you cannot make the music that they normally play too loud.  I think I read somewhere that they are limited to 82dB given the output of the normal Walkman, iPod, MP3 , etc.
 
Any recommendations for speakers that would get the job done?

 

[khbaur330162]

I'd suggest a pair of IEM's or canal phones such as the TDK EB750 ($13 on Amazon), or something similar. Not only are they noise isolating so they should help block out even more noise from the tractor when worn underneath your earmuffs, but they are also relatively sensitive (they get loud at lower volume settings on your MP3 player) so they should give you quite a bit of headroom. I believe the chord on the EB750 is reportedly short, so hopefully you keep your MP3 player in a shirt pocket, or worn in an armband. The chord should make it to your pocket since you'll be sitting, but I guess taller individuals had issues when standing. I have the TDK IE-500's and like them quite a bit.
 
If you're not used to canal phones they will probably hurt your ears after a while. Give it a week, your ears will become acclimated to this.
 
GL!

 

[bootdsc]

I have built something similar with some 3m hearing protectors, just remove the drivers from any full size double ended(cable goes into each side) headphone and carefully unsolder the the wires. Drill holes in each side just big enough for the cable to pass through then feed it in and solder the wires back into place. Mount the drivers inside the ear cup of the hearing protector(remove the foam insert) with a dap of epoxy. 
 
Now by the time your done with all of that you will probably have noticed you can just buy ready made active noise canceling hearing protection for shooting with built in headphone.

 

[tractorguy]

That's exactly what I did (see initial post).  The problem is that I can't get enough volume through the speakers I used to hear my audiobook over the din of the tractor..  My wife found a set of 3M WorkTunes http://www.amazon.com/3M-WorkTunes-Hearing-Protector-Compatible/dp/B0013092CS which seem to work pretty well.  The NRR is only 24 as compared to 30 but they are MP3 compatible with a detachable stereo mini cable, and it has a pretty good radio. They are also quite comfortable.  I would still like to replace the speakers (24 Ohm) in my home-made set with ones of the correct impedance.  I just don't know what I need to get a little more volume.

 

[bootdsc]

Okay well its not the impedance its the sensitivity per mw that matters, 24ohm is harder to drive then 50ohm headphones but those 24ohm headphones could have a better sensitivity rating so they will get louder. You might just need to get a better pair of headphone drivers, i like the philips hdj 1000 series because they get plenty loud straight out of a cellphone and have a nice mid and bass with a mostly flat treble. I have 3 or 4 pairs of the drivers around i haven't used in projects yet. If your in the usa i could send you a pair for $20 shipped.