Search This Blog

Wednesday, March 19, 2014

NuForce Primo 8: The firstborn

Disclaimer: Data presented here have been acquired with a pair of stock silicone sleeves inserted at 3mm away from the reference plane of the occluded ear simulator, unless stated otherwise.

Primo 8 is the very first quad-driver in ear monitor from an American audio manufacturer, NuForce. While NuForce's technological expertise have been verified repeatedly with their high quality Class-D amplifiers, their reputation as a headphone/IEM company still seems to be quite equivocal to enthuasists. Consequently, this first born child shall serve as a showcase of what the manufacturer is capable of.

PRO: Excellent channel-matching, low distortion, and properly aligned polarity.

CON: Dampers are not exchangeable. With the stock silicone sleeves, there is a risk of bandwidth cut-off above 10 kHz due to the IEM's high acoustic output impedance. Using a stock Comply sleeves, which have a tapered bore, should solve the issue.

ON SECOND THOUGHT #1: As stated by the manufacturer, unlike other quad-driver IEMs, such as Shure SE846, Ultimate Ears UE900, or Westone 4, Primo8's phase response is quite linear. Whether the audibility of such phase anomaly is still very questionable, it can at least safely be assumed that the quad-drivers inside of Primo 8 are behaving more in unity in terms of time-domain than its competitors, thus offering more natural sound. By coupling a pair of pre-packaged dual balanced armature drivers, NuForce is able to minimize any complications in the crossover network design while distributing an sufficient number of drivers throughout the frequency spectrum.
NuForce's proprietary phase-coherent crossover technology
Although Primo 8's phase coherent technology helps solve the phase-related problems, there is still a bit of pre-ringing present; Since physical phase-shift compensation(wavelength offset) is virtually impossible for woofer drivers within a small housing unit, such overlapping of time alignment is inevitable for any multi-driver IEMs.

ON SECOND THOUGHT #2: Securing a deep fit is vital for this IEM for securing both frequency response linearity and treble extension. When inserted shallow, the peak at 7 kHz, which is possibly caused by the quarter-wavelength resonance of the IEM, joins the second wavelength resonance of the ear canal, causing harshness.

ON SECOND THOUGHT #3: Ideally, Primo 8 requires a source device with output impedance less than 1 Ω due to how its impedance characteristic is shaped. With a source impedance of 33 Ω, the output at 10 kHz is attenuated about -11 dBSPL relative to that of 1 kHz. Even with 10 Ω, Primo 8 loses about -6 dB at 10 kHz relative to 1 kHz. However, it is important to note this fact: Since almost all of the smartphones and digital audio players currently available in the market have very low output impedance, only at few ohm values, such impedance interaction shall not affect portability of the IEM itself in practice.

ON SECOND THOUGHT #4: Unfortunately, altering acoustic damping design of the IEM is not possible as the stock dampers are not exchangeable. Instead, acoustic resistive materials may be inserted between the nozzle and the ear sleeve for DIY modification.

ON SECOND THOUGHT #5: As stated above, Primo 8 becomes a lot more linear in the treble simply by equipping a pair of stock Comply(T-100) sleeves, or any other ear sleeves that has a smooth tapering at the tip of the bore.

ON SECOND THOUGHT #6: Even though Primo 8's frequency response doesn't quite fit to the conventional diffuse-field reference, according to the new in-room headphone response target of Dr. Sean Olive of Harman International, Primo 8 is doing extremely well except for a little dip below 100 Hz.

IN CONCLUSION: NuForce Primo 8 is a solid product with an unique tonal quality, which enables the IEM to compete among other the other top contenders in the market. Of course, just like any other consumer products, Primo 8 isn't without its flaw especially with the impedance characteristic and insertion depth-related issues. Yet, in terms of electroacoustic performance, Primo 8 owns its quad-driver competitors when compared in stock configuration with an insertion depth at 3 mm away from the reference plane. A lot of research effort has been put into the development of this firstborn, and is definitely paying off.

For more information, please visit:


  1. measurement looks quite bad....a lot of resonance...extension is pretty bad...

  2. The impedance is a big drawback though as it would really require a dedicated amp to get more linear response, in particular, in the treble region. It really beats the idea of portability because of that flaw (much like the case of the TF10).

    1. The fact is that mobile phones and most small amp that dealt with IEM has extremely low output impedance rather than the other way around. As a matter of fact, iPhone 5 is 3 ohm, iphone 4 is 1 ohm, Samsung Note 2 is 0.97 ohm.; now I just grabbed some numbers on big amps: Beyerdynamic A1 is 98 ohm, SPL Phonitor is 10 ohm, Gram Slee Voyager is 33 ohm.

    2. Well it's the problem of most manufacturers not disclosing enough measurements I suppose. Unfortunately for most consumers (like myself) who don't have the ability or equipment to measure things it's really a hassle to get a decent portable source. Still, it's good to see that idevices have vastly improved through the years. As for the amp though, my only choice as of the moment is the O2.

  3. Hello Rin, I have a question about multi-driver IEMs and distortion measurements.
    Suppose you had a single driver IEM and a 4-way, 4-driver IEM that measured the same in terms of distortion throughout the spectrum at 100dB. Now, I don't know how exactly these measurements are carried out. Are they carried out using pure sine tones? If so, would the 4-driver IEM have less distortion playing music in practice because of the load sharing among the 4 drivers? (i.e. the maximum distortion would only be the summation of 1/4 the spectrum for each driver, vs summation of the whole spectrum for the fullrange driver in the single driver IEM)

    Or not?

  4. Welcome back! Could you provide a difference graph between Olive-Welti and In-room?

  5. Thanks for the measurements Rin. Some interesting stuff, especially in regards to the pre-ringing and impedance curve. I'd like to ask, do you have an email I can contact you on? I'd like to discuss using your graphs in my video reviews (with proper attribution to you and your website of course).