Monday, September 4, 2017

Koss SB-45 Headset and Sample Receive Audio

Koss SB-45 Communications Headset (click to expand)

Earlier, I posted a review of the IRIVER IGH-L20 headset for Ham radio use -- a good performing bargain headset.  A number of people expressed their sadness that IRIVER headset is only for sale in Asia, and has to be imported to other countries.  Wouldn't it be better to post a review of a headset that is both inexpensive and easy to find in countries like the USA?

Here's one for your consideration:  The Koss SB-45.

View into the earcup
The Koss SB-45 is sold for about $25 plus shipping on Amazon, and some Wal-Mart stores.  It is said to be a rebranded/slightly modified version of the Yamaha cm500, which gets incredible reviews from users on Eham.  You can read reviews of both headsets, and you'll see comments about how they're considered sounding identical and interchangeable at a contesting station.  I did notice, however, that Koss also sells an SB-40 version which looks more like the Yamaha cm500, but contains a dynamic mic.  The SB-45 reviewed here is the condenser mic version, which works with ICOM radios (the dynamic probably will too, but likely would require high mic gain settings). The Koss SB-40 and SB-45 look different, to me.  This makes me wonder how similar the SB-45 is to the more expensive, and highly-regarded Yamaha cm500.  I don't own the cm500, so I do not know.

I will say that the Koss SB-45 appears to be a good ham value, for the price.

1.  Very comfortable headset, even with long-term use.
2.  Generally very nice build quality (thin cord an exception)
3.  Attractive
4.  Adjustable microphone
5.  Very clear audio for DX sound
6.  Perfect weight
7.  No problems wearing with glasses
8.  Excellent outside noise blocking, but not overly so

1.  Thin cable
2.  Had same earpad material on my Sony headphones, and it began flaking severely within 2 years.  Radiosport material socks can fit over to extend life.
3.  Microphone lacks much bass.  My Icom 7300 settings are Bass +5, Treble 0.
4.  Receive sound is a bit bright, but very clear
5.  Need to remove wind screen and add a few layers of electrical tape to back of mic to remove room noise.  This is a :30 second fix, and highly recommended.

When I first purchased the Koss SB-45, I have to say I was a bit disappointed.  I felt they were far too bright on RX, and accentuated background HISS too much.  I am happy to say that I have since found a sweet-spot for listening, with the SB-45's.  These are some very sensitive headphones!  After a few weeks of use, I learned that I simply needed to adjust my ICOM 7300's bandwidth filtering a little to trim the highs, and to turn the AF GAIN/volume down (not a bad thing, given how headphones often damage hearing over time).  I live at a very noisy QTH, the noise can get to me. Radios tend to attenuate the hiss/highs a bit, with the volume down, and I find these headphones still allow the voices to come through clearly, after that AF Gain is lowered.  In the end, I'm pretty happy with the purchase.

8-Pin MIC/Headset Adapter HS-01C for ICOM 
The electret microphone of the Koss SB-45 is also extremely clear.  It's one negative, in my opinion, is that it lacks in bass, and that you need to remove the foam wind screen and add a few layersvof electrical tape covering the back side hole of the mic (easy).  Without doing that, you pick up more room noise.  What you get in return after this :30 second fix, however, is crystal-clear mid and high-level audio.  I found that some EQ-ing was in order, but reports have been pretty incredible with the ICOM 7300's transmit bandwidth set to my adjustments of WIDE 100-2900, or  MID 300-2900.  I've never been a fan of ICOM's jump to 500hz as the next choice on the bottom end for the NARROW setting, so I rarely use it.

My last article also left some people confused as to how you get headphones like this to work with the ICOM 7300, or other radios.  The trick is to search Ebay for your radio, and look for "headset patch cable" or something similar in the search string.  If you are wanting to buy this headset for the ICOM 7300, and need a patch cable, HEIL makes them.  I suggest you contact Bob Heil through his site, or use his website to determine which patch cable is right for you.  I added a photo of the one I purchased on E-bay, from K6VHF, for about $15 plus shipping, which I found to be cheaper.  It works well, and I have no issues with stray RF.  You can also build your own.  I will provide pin-outs for that in the following graphic, but if you use a dynamic mic, you need a 1uF non-polarized tantalum capacitor in series with mic lead.  This is according to Bob Heil, who also said you can get by with a .68F or a .47uF, but anything less will not pass good speech.  You don't want the blocking cap for an electret mic, however :

Sony earcups after 2 years
Link to Bob Heil's info on the Icom 7300 and mics:

As for the build quality of the Koss SB-45, it is generally excellent.  The only negatives here are the quite thin, and looong cabling, and the material used for the ear cups.  The material is comfortable, but it's that very paper-thin fake leather stuff often found on cheaper headsets.  I know from experience with my $20 Sony headphones, it will flake off within two years, and begin sticking to the sides of your face.  I do not know if replacement ear pads are available from Koss, but Radiosport headphone earpad socks work.

I have added an over-the-air recording of the Koss SB-45's, taken from my friend, HL1ZII's cell phone.  It will give you a good idea of how these headphones sound on-air.  As mentioned in the Pros/Cons, the microphone is very clear, but a bit lacking in bass -- what you hear is NOT with +5 Bass (it was +2).  I have since had to make some EQ adjustments to get it closer to where I prefer it (+5 Bass, and 0 Treble).  I would say this headset lends itself well toward contesting and DX work, if you prefer audio that cuts well, or local chat, if you add the Bass.

Enjoy, and give the Koss SB-45 a good look.

Below is the audio, and please FF to :49 seconds to hear what true live sound with the Koss SB-45's is like (the first 30 seconds are recorded CQ'ing).  I must mention, if you hear me cut out during the contact, and say, "I had a short," the problem was actually that I mistakenly pulled-out my PTT switch attachment -- operator error, not the headset's fault!:


  1. Hello -

    Quick Question: How do you key the mic?

    Thank you!

  2. The patch cable has two leads. One is for the headset mic, the other is a PTT button input. You need either a PTT petal, or hand button (or you can use VOX, but I find a button is much better). The headset earphone part still plugs into the radio jack where earphones always plug into.

    1. Hello, I am using a PC 350 Sennheiser, also excelent. But notice that all headset makers never mentions what type of microphone (electret or dynamic).

    2. I would venture to say that most are elecret mics. Eham reviews are a good resource for this information. Sometimes the Ohm statistics of the microphones are printed with the box, and that can be a tip as to whether the mic is dynamic, or electret.

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