Saturday, February 23, 2013

Monoprice 9927: A seven-dollar-mystery

This IEM is owned by my dear friend, Inks. I should thank him for all the hard works.

Monoprice 9927 is a black version of the well-known budget IEM, Monoprice 8320. Priced at an eye-popping $7, 9927 comes feature-packed:  sturdy built quality, fabric cable, and most importantly, a 14mm wide electrodynamic transducer... How can you ever possibly go wrong with such value?


PRO: Monoprice 9927 is indeed a call for an equal headphile-rights movement. Not only the electroacoustic performance of this IEM is well worth of $7, it also exceeds that of many expensive IEMs. Well-matched channel, linear frequency response, low distortion, clean transient.. 9927 is the most bang for the buck in headphones, guaranteed.

CON: The resonances at 3 kHz and 5 kHz are quite audible. In addition, 9927's bulkiness makes insertion quite tricky.

ON SECOND THOUGHT #1: 9927 performs better when it's shallow-inserted.

ON SECOND THOUGHT #2: The resonant peaks in the high frequency range can be effectively tamed with adequate amount of acoustic damping. A microfiber handkerchief should be sufficient to kill off any harshness.

ON SECOND THOUGHT #3: Monoprice 9927 is heavily tuned with acoustic vents. While the rear vent deals with the mid-range, the front vent attenuates the bass & the peak at 4~5 kHz.

ON SECOND THOUGHT #4: As this IEM can be fine-tweaked by equipping with different ear sleeves and modifying internally, detailed sleeve comparison & modification tutorial will be provided separately.


  1. That looks spectacular~~Good thing I had two extra pairs stuck underneath the bed. Really surprised they would perform that well distortion-wise.

    Fit is a PITA though. Any chance of doing the tip-comparing measurements like you did with the W4s?

  2. May I link to your very thorough technical analysis?

    I am a reseller of these earphones and want to inform my customers of your work.


    1. As long as the link is not shown on the product description of your website. I won't allow it otherwise.

  3. im interested to see what improvements (or not) could are made if these were in a silicone earmold with the use of a long tube from a double flanged tip for a deeper impression....

  4. First of all, thank you for making in-depth investigations on how to improve the sound of inexpensive IEMs (like the 9927 and the MH1). Good work. I think we should try to identify all of the cheap ones that are worthy of modification.

    Acoustic dampers on the 9927, as expected, blunt the peaks and smooth the response in the treble. Put in enough damping and the short bandwidth will be more obvious. In your articles on BA IEMs, you've used series resistance to alter the electrical response. Obviously that won't work here. We want to know if you're opposed to using a capacitor as well. Say, R = 68 ohms and C = 0.33 uF for an initial guess. That will shelve the treble up and might work well with acoustic damping. It's not that much more complex than a resistor in series, and doesn't add much to the material cost.


    1. Thanks. Of course, all you need is a pspice to fiddle with LOL I'd like to defer such use of electrical Z modification as a last resort, as there's a high chance for the audiophilic snake oil to get involved..