I’ve long advocated for protecting your hearing by limiting the levels you listen to. Long-term exposure to high sound pressure levels leads to noise-induced hearing loss (NIHL), which can greatly reduce your sensitivity to high frequencies and midrange frequencies that are fundamental to understanding speech. Another potential symptom is the constant annoyance of tinnitus (aka ringing in the ears), which can become permanent—and there’s no cure.
Puro Sound Labs addressed this concern with its PuroQuiet headphone, reviewed here, which is designed for children and limits its output level to protect them from NIHL. Now, the company has introduced an adult version of the same idea. The PuroPro purports to limit the sound pressure level reaching your ears while providing hybrid active noise cancellation, Bluetooth connection to your source device, and excellent sound quality. It’s remarkably successful in achieving these goals, with one minor caveat.
This review is part of TechHive’s coverage of the best headphones, where you’ll find reviews of competing products, plus a buyer’s guide to the features you should consider when shopping for this type of product.
The PuroPro is a lightweight, over-ear headphone made mostly of plastic with protein-leather-clad earpads and adjustable headband. The earcups fold into a compact form that fits in the included travel case.
Interestingly, the PuroPro is shipped in a wood box. The wood is very light; it reminds me of the balsa wood used in the model airplanes I used to build as a kid. The company touts its “environmentally friendly packaging,” but I’m not sure how environmentally friendly this wood is compared with cardboard.
Each earcup houses a 40mm full-range, custom-designed dynamic driver with a frequency response specified to extend from 20Hz to 20kHz with less than 1% THD. The rated power delivered to the drivers is 10mW, and the wired connection has an input impedance of 32 ohms. The company touts its Puro Balanced Response Curve (see Fig. 1), which is said to deliver clear, crisp vocals and full, dynamic bass within the volume limit imposed by the headphone.
Speaking of which, the PuroPro limits the sound pressure level of its output to help avoid—or at least reduce—noise-induced hearing loss. Unlike the PuroQuiet, you can select one of two limits: 85 or 95 dB SPL. The Occupational Safety and Health Administration (OSHA) specifies that workers can be exposed to an average of 85 dB SPL during an eight-hour day, while 95 dB SPL is safe for only 50 minutes. I guess Puro Sound Labs figured that adults can be responsible for time-limiting their exposure at 95 dB SPL, but I suspect that plenty of young adults will not heed that limit.
As with many wireless headphones, the PuroPro offers hybrid active noise cancellation (ANC) with four microphones (two per earcup) that pick up ambient sounds. The headphone’s DSP inverts the phase of those sounds and adds that signal to the original sounds, reducing the overall level thanks to phase cancellation. Interestingly, the PuroPro offers two levels of ANC: 32 and 15 dB. The word “hybrid” refers to the passive attenuation offered by the circumaural earcups.
Bluetooth 5.0 provides a wireless connection, and the PuroPro supports the high-quality aptX codec. The right earcup provides a 3.5mm analog audio connector for legacy devices, and the headphones come with a cable to connect them. Fortunately, the headphone doesn’t need the power to be on for this type of connection.
On a full charge, the 750mAh lithium-ion battery can power the PuroPro for up to 32 hours with Bluetooth on or 28 hours with Bluetooth and ANC on. It takes about two hours to charge the battery from an empty state by connecting it to a 5V/1A power source using the micro-USB port at the bottom of the left earcup.
If you pair the PuroPro to a smartphone, it can be used to answer calls and issue voice commands. A single, separate microphone picks up your voice for these functions.
The user interface is very simple. It consists of four buttons on the bottom of the right earcup. A power on/off button, which doubles as a music play/pause control and voice assistant activator, is located directly behind the 3.5mm audio connector. The ANC button is just in front of that connector. Pressing that button toggles between ANC off and 35 dB or 15 dB of attenuation, dubbed “ANC 1” and “ANC 2.”
An elongated rocker behind the power button adjusts the volume up and down, and pressing both ends together toggles between the 85 dB and 95 dB volume limit. Holding the “+” or “-“ end of the rocker skips to the next or previous track.
A tiny LED next to the micro USB port indicates charging status, while another tiny LED next to the 3.5mm audio connector indicates power and Bluetooth status. The ANC button has an embedded LED that indicates whether ANC is on or off.
When you operate these functions, you get an audible vocal confirmation, such as “Power on,” “Power off,” “ANC 1,” “ANC 2,” “ANC off,” “85 decibel max,” “95 decibel max.” When you power on the headphone, it also tells you the battery and Bluetooth-connection status. I like this much better than sequences of musical notes, which some products use.
When I first put the PuroPro on my head, it felt exceedingly comfortable—earpads large enough for my big ears, lightweight, and low clamping pressure from the headband. As usual, I played tracks via Bluetooth from the Tidal Master library of high-res audio files using my iPhone XS.
First up was “In My Bones” from Jacob Collier’s fourth album Djesse Vol. 3. This is a super-funky, pop-infused track that really gets down. On the PuroPro, the sound was slightly veiled, especially in the bass. I listened with the limiter set to 85 and 95 dB, and found that the 95 dB setting was quite a bit louder and somewhat less veiled, though still not crystal clear.
I also tried the ANC settings (32 dB, 15 dB, Off) and listened for any differences in sound quality. (I’ll discuss how effectively ANC cancels noise in the next section.) Happily, the tonal balance and volume didn’t change much at all from one setting to the next, but turning ANC on did increase the veiled quality. I ended up preferring the 95 dB limit setting with ANC off.
“Judas” from Emily’s D+Evolution by Esperanza Spaulding has lots of deep bass—she’s a bass player, after all—and I heard the same slightly veiled sound, especially in the bass. But her voice sounded quite natural and smooth.
Speaking of vocals, Sam Smith sounds fantastic on “Young” from his album Love Goes. This is a beautiful a cappella track in which the lead is completely natural, while the background chorus is highly processed, creating a very interesting effect. On the PuroPro, the sound was still slightly veiled but very smooth, which works well on this track.
I was a big fan of Yes in my college days; I heard them live on more than one occasion. So, when I found a new Yes album, The Royal Affair Tour (Live From Las Vegas), I listened to the classic “Roundabout.” Sadly, the playing is not as precise as in earlier days, and the mix is a bit strange with more rhythm guitar than I would have used. On the PuroPro, the sound was silky smooth but still a bit veiled.
For some solo piano, I played “Part XI” from Keith Jarrett’s Budapest Concert. This gorgeous composition sounded smooth on the PuroPro, though not as transparent as I would like.
The same was true of full orchestral music. I listened to the first movement of Franz Schmidt’s Symphony No. 2 as recorded by the Frankfurt Radio Symphony under the direction of Paavo Järvi on the album Franz Schmidt: Complete Symphonies. Schmidt is a woefully underappreciated late-romantic/early-modern composer, and his second symphony is a joy to listen to. As I had come to expect, the PuroPro sounded smooth but slightly veiled, and the low end was a bit congested. The orchestral sections were not particularly well-defined and sounded a bit smushed together.
ANC and volume limiting
To test the PuroPro’s noise cancellation, I took it out to my garage and ran the clothes dryer, which makes a nice broadband, steady-state noise. With ANC off, I was amazed at how well the passive isolation of the earpads blocked the noise, especially high frequencies. Turning ANC on to its high setting (ANC 1, 32 dB attenuation) dramatically reduced low and mid frequencies. The low setting (ANC 2, 15 dB) was also very effective, though I could hear more midrange frequencies. Still, it was much better than with ANC off.
As I mentioned earlier, setting the volume limiter to 95 dB resulted in a significantly higher level than the 85 dB setting. So, I pulled out my calibrated measurement microphone (an iTestMic), which is designed to work with the AudioTools iOS app from Studio Six Digital.
I used the SPL Graph module within AudioTools on my iPhone XS. The module measures SPL over time and provides various metrics, including Leq (average RMS level over the entire length of the measurement) and Lmax (maximum 1-second RMS level during the measurement).
For this measurement, I played “White Room,” by Cream, from an iPad. I cranked the volume to maximum and played the tune twice—once with the limiter set to 85 dB and again with the limiter set to 95 dB—while pointing the microphone directly into the center of the right earcup. The mic has a windscreen, so I let it rest on the inner surface of the earcup.
At the 85 dB setting, Leq was 73.3 dBA (A-weighted), and Lmax was 85.6 dBZ (flat). That’s barely above the 85 dB limit, and only momentarily. At the 95 dB setting, Leq was 82.5 dBA, and Lmax was 91.4 dBZ—a significant increase from the 85 dB setting, but it did not reach or exceed the 95 dB limit.
Comparison with the Cleer Flow II
These days, my reference for Bluetooth ANC headphones is the Cleer Flow II, reviewed here. And at $179.99, it’s in the same price ballpark as the PuroPro, so I listened to each of the tracks listed earlier on both headphones.
From the first note to the last, the Flow II sounded clean, clear, and open with no hint of the slightly veiled quality I heard consistently from the PuroPro. On the orchestral track, the sections were more distinct and the loud brass section was more sparkling. The only negative I heard was a slightly harsh, strident quality on the Keith Jarrett solo piano track.
In terms of comfort, the PuroPro is the clear winner. The Flow II is heavier, its earcups are smaller, and its clamping pressure is greater. On the other hand, the Flow II seems quite a bit more substantial, leading to its extra weight.
I also compared the noise cancellation of the two headphones. The Flow II has no passive isolation; in fact, when its ANC is off, it pipes ambient sound into the headphone to make sure you hear the surrounding environment—a great safety feature if you’re wearing them while you’re out walking around. With ANC on, the Flow II is about as effective as the PuroPro’s ANC 2 setting, which is to say it’s not quite as good as the PuroPro’s ANC 1 setting, but still very good.
The Puro Sound Labs PuroPro has a lot going for it. It’s supremely comfortable, and its hybrid noise cancelling is top-notch. I applaud the company for being concerned about noise-induced hearing loss and doing something about it by limiting the headphone’s output level. Increasing the level at the higher limit setting, however, is a strange choice IMO.
The sound quality is not bad by any means—it’s silky smooth, and vocals sound entirely natural. But it’s also consistently a bit veiled, especially in the low end, which leads to a slightly congested presentation.
By comparison, the similarly priced Cleer Flow II lives up to the company’s cleverly misspelled name—clear, clean, and open. And it feels more substantial, though that translates to being heavier. On the downside, it’s less comfortable than the PuroPro, with smaller earpads and greater clamping pressure. That’s not to say it’s terribly uncomfortable, just less comfortable, especially over long durations.
At $149.99, the PuroPro is quite affordable. If you place a high value on comfort, noise cancellation, and protecting your hearing, and you can tolerate slightly less-than-crystal-clear sound quality, the PuroPro is an excellent choice. On the other hand, if sound quality is paramount, the Cleer Flow II is the better alternative.
Updated shortly after publication to add an illustration of the headphone’s response curve, and to add the fact that the headphone supports the aptX codec.