A Sonic Stunner: The Koss SP330 On-Ear Headphone Measurements


Click on graphs image to download .pdf for closer inspection.

Raw frequency response measurements show an ear pad that varies some with bass placement. In listening tests it became apparent that the actual ability to seal and deliver bass response was much worse in real listening situations. (I guess I try to be careful when taking the measurements. I think it would be very difficult to have the goal to recreate real-world listening performance when positioning the headphones, as opposed to trying for best seal in each position.) If these headphones don't seal reasonably well, bass response is compromised.

Compensated FR plots, other than a few modest bumps and wiggles, seems very, very good to me. A nice bass rise with good extension. Bass rise appears to start at 300Hz, which is a bit high, but compared to the level between 400Hz to 1kHz, you could say the bass rise starts at 200Hz. I like 150Hz, so that's close, but the truth is because of the likelihood of somewhat poor coupling you are likely to get less bass that what is measured.

Compensated response from 400Hz to 4kHz might be considered spectacular. Almost all headphones tend to fall off in this region, the SP330 is essentially flat to 4.5kHz. In listening, this made them sound very present, first row seating. Normally I'd be wary of that as things might get strident, but I didn't hear that. They were just strongly present—lacking in any sense of veil.

The only problem area is the mid- and upper-treble where we see two distinct bumps at 10Khz and 20kHz. I did tend to hear treble transients as just a little metallic, but that's not quite the right word.

A glance at the 300Hz square wave shows what might be the origin of the slightly off treble, slightly excessive undershoot after the first spike. I've mentioned it before, a very clean and regular ring on the front end of the 300Hz square wave is often quite benign. In listening, though cymbals were accentuated a bit, they remained remarkably clear and natural sounding.

30 Hz square wave response is near ideal with small shoulder on the leading edge and a long, straight, waveform top following. Looking at the THD in the bass shows an unbelievably low amount of distortion for a headphone of this type.

Speaking of distortion, the THD+noise plot is very, very good for an on-ear headphone. Not only is the bass distortion almost unbelievably low, but all measurements are below 1%, and the 100dB curve remains below the 90dB curve for almost its entire length. This is a clean sounding headphone, and it will play clean even at loud levels.

Impulse response leading edge is quick, but a couple of resonances mar the immediately following response. Fortunately, these problems die rather quickly.

Impedance and phase plots show a well behaved 35 Ohm headphone.

Isolation is remarkably good at 19dB broad band—I have to think, however, that in real-world use the seal will be significantly less effective.

With an efficiency of 51mVrms the SP330 will play to solid listening levels on portable devices.

Koss Corporation
4129 N. Port Washington Avenue
Milwaukee, WI 53212

Seth195208's picture

..this doesn't get "you know who" started again. Wow! Outstanding measurements!

Argyris's picture

I've been waiting for this review for quite a while, ever since I saw these mentioned in the gift guide. Thanks for taking the time to write this up, Tyll.

Wow. I figured these would be pretty good when I saw the measurements, but of course there's no substitute for actual listening. Based on your impressions, these sound right up my street. Koss might well be getting some of my banked up Amazon gift card credit in the near future...

...except that the SP330 has been out of stock on Amazon for weeks now. Looking at the review section on the SP330's Amazon page, I can surmise that Koss made sure a lot of people got free samples to review (ideally favorably), and that's where most of Amazon's initial stock went.

Personally I don't have a problem with consumer review programs (as long as there's proper disclosure, and in this case there is), but I do think that Koss might have inadvertently shot themselves in the foot here by not having the SP330 in stock on one of the largest retail sites in the world during holiday season. Dozens of positive reviews of an unavailable product might just infuriate prospective buyers and drive them elsewhere, since the "deadline" (Christmas) is less than a week away now. I really hope this doesn't happen.

Incidentally, I'm still trying to decide whether to wait for the SP330 or shoot a bit higher up the price chain for the V-MODA XS. If you don't mind me asking, Tyll, how would you say they compare SQ-wise, and which do you overall prefer and why?

Thanks for taking the time to read this.

zobel's picture

They list 5 pairs currently available tonight (Dec. 20th).

Argyris's picture

A belated thanks for the heads up on that. By the time I got around to checking, they were gone. However, by quite a stroke of luck, about half an hour ago at time of posting this they had one...ONE...in stock, which I promptly snapped up. It arrives Dec. 30th, alongside an NAD HP50. Pretty stiff competition, if what I've read on IF and elsewhere holds up.

fzfan's picture

I am a long time follower and first time poster.
I have a pair of 1970s vintage Koss Pro 4AAs I have owned and used since acquiring them new "back in the day". I have never seen a review of vintage headphones that could compare them with todays models. I find the Pro 4AAs somwhat dark (pronounced bass with recessed upper mid/treble).
I'm curious if IF has done vintage can reviews, specifically, the Pro 4AAs. I would be interested to know how these measure, etc. as well as another's objective/subjective opinion.

Sweden's picture

This FR reminded me a bit of the Fostex TH-900.
Yeah I agree that Koss best bet is in the budget segment.
But why make the design so boorishly unsexy? This won't fly with kids dammit.
I think that what we are seeing is headphone evolution at work. The companies who can't produce nice looking portable headphones will go extinct. It doesn't matter how good the sound is, if they look clownish or to bland on your head people between 13 and 40 won't buy them.
I'm my country has the fabulous sounding Visio HP50 sold very poorly. They look a bit weird when worn unfortunately which is my best bet for their lack of success.

Personally I'm hoping for an updated electrostatic headphone. Something with the sound more in line with the Stax SR-507, but with much better comfort and a price tag around 500.
Skip the amp this time Koss unless you can hire a guy like Birgir as a designer.

forkboy1965's picture

Thanks for including the link to the article. Nearing 50 rapidly my experience with Koss is just as you describe... a stroll down Radio Shack memory lane.

What I found slightly disturbing from the article was how dismissive Koss seems to be of design flair. Personally, I find Beats and their like unattractive... more like kids toys than audio equipment. But that doesn't mean it hasn't worked for them and others.

To ignore that fashion has a decided influence on headphone design seems to be sealing your fate for failure. They don't have to be flashy, neon, plastic-shiny colors, but some sense of modernity and design couldn't hurt.

After all, quality sound and an attractive housing aren't mutually exclusive. Maybe it is time to trade-in that bow tie for something different?

Argyris's picture

I agree completely. I think something Koss hasn't considered is that Beats et al. became so successful so quickly because they offered (at least in appearance) something different from the bargain bin, blister pack, fashion-last products that, quite frankly, the likes of Koss and the big box brands had been offering consumers as the only choice for over a decade. Making the same kind of stuff consumers feel they've finally escaped from, even if the guts sound better now, isn't likely to be a winning strategy in the long run, IMO.

I agree with Koss that chasing pure fashion is probably a fruitless endeavor, and celebrity endorsements are not only expensive but are likely to be seen as "me too" efforts to compete with Beats. (One wonders how many rebadged PRODJ100s Tony Bennett's endorsement moved...)

However, there's a big difference between making an all-fashion, no substance product, and making something that has at least some modicum of style and is durable, has good ergonomics, and performs well. Protip: When in doubt, make it metal. Also, a quirky advertising campaign might not hurt.

I think Koss is absolutely capable of pulling off something like this, but the company would need to be willing to shift focus away from just raw performance and value. They should look at products like the HD25, the DT1350, or pretty much anything from V-MODA for inspiration--all represent good (though different) balances of style, build, ergonomics, and performance--then make something similar that targets a lower price range. If they made it perform as well as the SP330 is reputed to, and offered it for around $100 USD (maybe a bit higher, especially if there's a lot of metal in the construction), I think they'd have a bona fide hit on their hands.

tony's picture

Koss needs a bit of help, thanks. I'm from Wisconsin so what you do for these souls you do for me, in a kind of way.
I'll buy a pair to gift, I'll buy a matching JDS from St.Louis too, a nice little "Fly-over Country" music system.

Tony in Michigan

ps. if it ends-up being as good as you suggest, I'll get one of these little systems for myself - to show-off: "see, we make stuff like this in the Midwest"

Thanks for the nudge

Long time listener's picture

Tyll, you mention that cymbals were overly accentuated, and attribute that to the region at 10Khz and above. But it seems that in your other comments, you've already identified the problem: "the SP330 is essentially flat to 4.5kHz. In listening, this made them sound very present, first row seating. Normally I'd be wary of that as things might get strident..." I think you're right. I bit more of a dip around 4.5 Khz would be appropriate. Cymbals do have sonic content at that frequency that will be heard. It seems to me that the response at and above 10Khz is about the same as we've seen in millions of other headphones. Even though there's a small peak at 10Khz, it's still lower than the midrange, and the response drops off sharply above that. My opinion is that there isn't likely to be a problem there.

Jim Tavegia's picture

With the "25gift" promo code an even better buy.

Stillhart's picture

How would you say they compare to the M80, Momentum On-ear and the venerable Creative Aurvana Live? I consider all these to be in the same price point and in direct competition.

I've owned the MOE and CAL and I prefer the sound of the CAL by a lot. The build quality leaves a lot to be desired, however.

JRAudio's picture

I friend of mine and I just bought this headphones (one for each) and must say, yes for the price, it is a good sounding over the ear closed headphone (if you attached it correctly to the ears) but,

even without a real use, both headphones have mechanical problems on the rotating mechanism of the left channel (where the cable is connected to).

The rotating mechanism on the right channels is working fine, so it has concrete end points for and does not get loose,

but that of the left channels, you can rotate “endless” and it gets loose and fall off just after 3 to 4 slowly + / - 45 degree rotations.

Can someone, who also owns this headphones, can comment, if this is also the case?

We will send both back and hope for betters ones next.

Best Regards

Guitarist9273's picture

compare to the best on-ear headphones? Regardless of price. Like the v-moda XS, the Beats Solo 2, etc.

iraweiss's picture

I have had a pair of Pro 4AAA Stereophones since the 1970's. About a year and a half ago I called them as the ear cushions had died. Low and behold I was able to purchase a new pair of cushions for $5. This kind of support (with the rare exception of a few companies like Definitive Technology or oppo) is unheard of these days.

They were easy to replace and the phones still sound great. Their isolation is perfect for watching TV or a movie or listening to music while on the treadmill.

I too would love to know how these vintage headphones compare to contemporary models.