10. On The Graph And To The Ear

Naturally, our testing was done with one of our acoustic-coupling systems, since the artificial ear wasn't suitable. The Plug delivered response that was typical of the type of transducer used by Koss, with very linear bass and an attenuated upper part of the spectrum that showed various resonance peaks.

The best response curve we got with The Plug. You can see the linear bass, then a drop in the level in the high frequencies, with various resonance peaks. This curve correlates well with our listening and equalization tests, so we consider it accurate.

With a different coupling, the response curve changed, but kept the same overall appearance.

• PLUG PORTABLE STEREO...
• • ElectronicsPLUS
  • $15.89

The Plug's impedance was very regular, but low. Here you can clearly see a resonance peak at 4 kHz.

Inserting these earphones was simple and pleasant, and the parts that go into your ear don't hurt your ear canal because there are no hard parts - unlike competitors' sets. That's a positive point, but on the other hand, the acoustic isolation is not quite as good.

Our first impression from listening was fairly good, but we did quickly notice that the midrange lacked definition and the extreme highs were hidden. These two points can be corrected, at least partially, with a fairly simple adjustment of the equalizer. So if your player has one, you'll be able to get good sound. The Plug is worth making the effort, because its bass is quite good despite a certain lack of incisiveness. Once corrections are made, this becomes a very decent set of earphones at an attractive price.

This model can pump out very high volume without perceptible distortion, and it was also capable of delivering high decibel levels with a portable audio player. That's not surprising if you look at the response curve - you can see that it is rated at 125 dB / V over the entire lower part of the audio spectrum. That makes this a good choice if your player's output is a little weak, but you'll have to be reasonable if you don't want to destroy your ears...