Pros:  Stellar build quality, excellent price, comfortable, fantastic quality cable, excellent clarity, good bass control, balanced signature

Cons: Hard to drive, average soundstage

List Price: £99 ($129)

Acknowledgment

The RHA CL750 was provided to me in exchange for running the UK leg of the RHA world-wide tour for the release of the DACAMP L1, CL1, and CL750.

Introduction

I’m getting to be a bit of an RHA veteran. I’ve known folks at the company for a couple years and have reviewed their products for almost as long. They are a good crew and they make products with some of the best build quality you’ll see, period, not just in their price range. They are unique among manufacturers in standing by that build quality with 3 year warranties.

I’ve had a few firsts with RHA: first Christmas card from a manufacturer (others do this also, but not all), first piece of swag (RHA have the coolest t-shirt), and first ever review sample in the s500i. That’s a good little headphone—aggressive and crunchy with a demand for power that is surprising. I personally like them, but I haven’t been a big fan of a couple of their units. The DACAMP L1 fell short for me whilst I understand it’s appeal; I didn’t like the crimes that the CL1 commits in the mids; and the T20 is just too friggin’ sharp in the treble.

Last year, RHA asked me to manage the tour of the DACAMP L1, CL1, and the CL750. It was the first tour I’d run. I’ve run two since and have one more coming—stay tuned. It wasn’t stipulated to me that I even had to review these—I’m not sure other tour leads necessarily did, but here I am, finishing out a trio where the first two didn’t really do it for me. We’ll see if the CL750 sounds better than its release mates.

Usability: Form & Function

Unboxing

The CL750 is well packaged, like every single item I have ever had grace my reviewing desk from RHA. These guys do not mess around with bad packaging. At the £99 price point we don’t get the fancy boxes of the CL1 or DACAMP L1, but we do get a nice card sleeve with good colour printed graphics, full description of the contents, and an admonition that you need an amplifier for this sucka. Inside the card sleeve the two earpieces are nicely presented. It very much reminds me of fiddle-heads. If positioning of headphones in a package can have a lyrical quality, this positioning does. Behind the IEMs we have the carrying case—it fits the CL750 better than the CL1 but is the same case. The carrying case includes a tip holder and plenty of tips: six pairs silicone single flange (S/M/L), two pairs double flange tips (M/L), and three pairs of Comply Tsx-200 foam tips (S/M/L). A clothing clip is also included.

Build Quality

I’ve not yet run into an RHA product with bad build quality and the RHA CL750 is no exception. The cable is soft and supple with an excellent chin slider, the shells are sturdy and shiny stainless steel, everything exudes class. These IEMs also come with a three year warranty. You can really rest easy with these.

Ergonomics

As mentioned above, the cable on these is very comfortable. The horn shape of the IEMs also easily slides into my ear and stays securely. RHA have made another comfortable headphone. I’ve found each and every one of their headphones very comfy.

Usability

The CL750, like its big brother, likes some juice. All the DAPs that play well with the CL1, also work for the CL750. Here are sources that I’ve tried the CL750 with and had success: Aune M1s, Shanling M2s, Echobox Explorer, TheBit Opus #3, Aune S6 (review in process), Questyle CMA600i, and of course the RHA DACAMP L1. The only unsuccessful pairing was the FiiO X5iii as its amp is a bit weak-sauce. I’d wager that Onkyo and Pioneer DAPs will have problems too, as they have comparable amps to the FiiO X5iii.

Audio quality

The CL750 has a balanced albeit a bit forward signature, with a little bit of emphasis in the bass and the treble. The bass has good depth and body but doesn’t have stellar definition and comes off as a bit slow and with some bloom compared to other iems in my possession. The mids are lightly pushed back, but I wouldn’t call them recessed. Vocals still have energy and passion. Electric guitars have nice crunch. Overall the sound is energetic and engaging. The treble has good energy, but not overwhelming energy like it’s stable-mate the CL1. The treble has good detail retrieval for the price, and a soundstage that is about par for this price level. Some percussive elements of the treble sound a bit more metallic than is natural.

Comparisons

Comparisons were volume matched using an SPL meter to approximately 78.2 dB. I use a home-made coupler for IEMS and white noise for matching. The reason I use white noise is because it reduces the potential for frequency response to affect how loud a headphone plays at. If I’m comparing two headphones and use a single tone to set volume, and these two headphones have different response at that frequency, then I’ve biased my comparison from the start. One headphone will be louder than the other due to frequency response curve. With white noise there is equal intensity at all frequencies, it’s like using the whole frequency spectrum to volume match. Because white noise is random, levels will vary while observing, as the figure at right shows, so the volume matched numbers below are subjective averaging of levels observed over approximately 20 seconds. I use 78.2 dB as this is generally enough volume for headphones to reach their full dynamic power, and it is well within safe listening levels. I’ve done enough volume matchings now that I can get within 0.5 dB of 78.2 by ear most days now, but the measurements are still important.

RHA CL1

The CL750 has most of the same characteristics of the CL1, but because it doesn’t have as high a treble spike, at volume-matched levels it sounds more balanced, with more true mids. The CL1 will play better with more sources as they are significantly less bright sounding and more natural sounding than the CL1. The soundstage is a little smaller than the CL1 and it doesn’t catch as many little details, but it also doesn’t amplify vinyl hiss or mastering noise from loudness warred tracks that wouldn’t be as pernicious without the big treble boost of the CL1. The CL750, provided it is driven properly sounds excellent with most material. I did comparisons for both using the copper cable, as I’m pretty sure this is exactly the same cable, with the only difference being whether it is detachable.

On 2Pac – God Bless the Dead, the vocal is further back in the stage and a bit duller sounding on the CL1 compared to the CL750. The mids are more energetic and enjoyable on the CL750 playing out of the Aune S6. The bass is a bit bigger on the CL1. The CL1 has a wider sound stage, and similar depth and height. The CL1 creates the illusion of greater depth by having recessed mids.

Listening to The Beach Boys – Sloop John B (DSD64), the bass is more linear on the CL750. The tinkles of the triangle are not overly emphasized and have nice detailed presentation and good tonality. The CL750 does a good job of letting all the varied instruments in this track shine. This is a precisely mastered stage with elements spread all over the stage in a variety of frequencies. The CL750 images everything well. On the CL1 the treble is sharper on the triangles and there is hiss from the recording that is inappropriately amplified. In addition, the mids are sucked out. It is not a natural sound. The image cast by the CL1 is a bit wider. Bass presentation of this track is pretty similar between the two IEMs.

The presentation of the CL1 is more restrained, due to the recessed mids, when listening to Infected Mushroom – Becoming Insane. Some may find this appealing as it allows lower treble elements and bass elements to separate from the mids a bit in space. The CL750 is more in your face and aggressive on this track.

As I’ve previously mentioned, the CL1 does a terrible job on Eagles – Hotel California (DCC Gold). The vocals are sucked out and lacking energy. They sound dull. The airplane in the intro is lost in the mix. It sounds more normal with the CL750.

UERR (Ultimate Ears Reference Remastered)

The UERR is a neutral reference IEM, so this comparison is probably the most important for nailing down the signature of the CL750. Looking at the frequency response charts from RHA, it looks like a mild V-shaped signature. Now we’ll see how it sounds.  In the past I’ve observed that at the same measured SPL, the UERR always sounds louder. To compensate for this I’ve dropped the SPL threshold on the matching to approximately 76dB on the UERR. In past comparisons, this has seemed to create an equal footing in past reviews.

On Massive Attack – Angel, the UERR drops deep and has good extension. The vocals sound natural and weighty. In contrast the vocals on the CL750 sound a bit sharper, but also clearer. Cymbals sound a bit splashy on this track with the CL750, whilst the UERR has a more shimmery and accurate presentation. The bass drops low and has good body on the UERR. The UERR has more focused and powerful bass than the CL750. Overall the bass is more satisfying on the UERR. For those who like a bit of bass bloom, the CL750 will give you this. The overall sound is clean on the CL750 and a little bit thin. There is some metallic crunch that is reminiscent of the s500i. More bass, and more upper mids would improve the tuning.

RHA s500i

The RHA s500i has a similar tuning with nice crunch on electric guitars, but it doesn’t like to be listened to at 78db. At that volume it is doesn’t accept tracks from outside the loudness war spectrum well. It sounds veiled in the mids and suppressed in the bass on quieter masterings. Both headphones have some metallic elements in the treble above and beyond what the instruments offer naturally. The s500i has a smaller sound stage that is confined to the head with limited depth and height. The image is good, but quite intimate. With PCM tracks, you can turn on volume levelling to minimise the effect somewhat in desktop players and some portable players, including some music apps on phones.

The CL750 has a clearer presentation, no veil at all here, and a taller and wider stage. Treble is a bit more complete sounding. The s500i sounds like it is giving you an emphasis on the metal strike and not enough on the tone of metallic treble instruments. More of the tone comes through on the CL750. Bass is also more present.

It’s quite amazing going back to an under $50 headphone that you loved after more than a year and a ton of additional headphone experience. The RHA s500i is good at it’s price, but there are more competitive headphones, albeit without it’s build quality. At $100 to $150 you hit the sweet spot for IEM value. There are too many good options, including the RHA CL750.

Specifications

Specifications
List Price	£99
Drivers	CL Dynamic
Impedance	150Ω
Sensitivity	89dB
Frequency Response	16Hz – 45kHz
Rated/Max Power	10/50mW
Cables	1.35m double-twisted OFC
Accessories	Carrying case, stainless steel eartip holder, 3 pairs Comply (S/M/L), 6 pairs single flange silicone tips (S/M/L), 2 pairs double flange silicone tips (M/L), clothing clip
Weight	35g
Warranty	3 years

Conclusions

The RHA CL750 has a pleasing balanced signature with good performance across the frequency spectrum. It doesn’t have the biggest stage or the most detail, but it is engaging and a lovely listen given sufficient power. The build quality is to RHA’s ridiculously good standard. These things are built like a brick house. Mighty mighty. The IEMs are comfortable and come hard-wired with an excellent copper cable. The cable and the headphone are wonderfully ergonomic. If you have a DAP with decent output levels and are hunting for a clear, nicely balanced driver with stellar build quality and ergonomics. At £99, I don’t hesitate to recommend the RHA CL750 and think they are quite a bargain.