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STAX SR-5 (1975) Headphone Review

Cuckoo Studio

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SR-5_2.3.1.jpg

Measurement Conditions Explanation And Chart Interpretation Of Cuckoo Studio Review​


Welcome to Cuckoo Studio Review. I'm Anzol,this is a program dedicated to reviewing audio products from the perspective of a mixing engineer.
We've received the STAX SR-5 from Sandaimao. I'd like to thank him for his support of the channel.Let's take a look at how these headphones perform.

SR-5_2.2.1.jpg


The STAX SR-5 was released in 1975, nearly half a century ago. Those familiar with the brand might know that the SR-1 was their inaugural model in 1960, and while the subsequent SR-2 and SR-3 had detail changes, They retained the vintage "big scissor" headband design. The most significant change in the SR-5, based on the SR-3, is here: the single-rod adjustment's exposed metal has been replaced with the now more common rectangular plastic casing with silver decorative patches, and it's marked with the minimalist MODEL SR-5
and "electrostatic earspeaker" labels.

Sr-1-768x1024.jpg

*old SR-1 (1960)
SR-5_2.27.1.jpg


* SR-5(1975) most significant changes.

SR-5_2.83.1.jpg


The original earpads are on the firmer side, and the internal space is not very large. Some modern headphones often overlook the addition of a bi-directional pivot design, which is not absent here, allowing for a better fit with the ears. With its weight under 300 grams and a moderate clamping force, the wearing experience becomes extremely comfortable when switching to third-party larger earpads. The black metal mesh is the open-back design of the SR-5, with the retro-style L and R indicators printed on each side.

SR-5_2.26.1.jpg

SR-5_2.23.1.jpgSR-5_2.12.1.jpgSR-5_2.9.1.jpgSR-5_2.8.1.jpgSR-5_2.22.1.jpg
The SR-5 provided by Sandaimao is surprisingly well-preserved; for a product that has survived nearly half a century, the white body has not yellowed significantly, and there are only a few scratches. The cable integrity is also not an issue. Although the initial SR-5 is not its last version, for me, it has reached a just-right balance of modern and vintage,looking very satisfying for collectors.

SR-5_2.82.1.jpg


Accompanying the SR-5 is the recommended pairing from that era, the SRD-6.
Compared to the headphones themselves, its rust-filled body shows its age. But this old-style electrostatic "amplifier" connection method requires, like passive speakers, to be connected to another amplifier. The front knob only switches between speaker and headphone outputs, and the gain level still needs to be adjusted by the preceding amplifier.So calling it an amplifier is not quite accurate.It is a Headphone Adaptor, an adapter for converting amplifier connections to electrostatic interfaces.

SR-5_2.28.1.jpg

SR-5_2.32.1.jpg

SR-5_2.30.1.jpgSR-5_2.31.1.jpg
Let's see how this product, which was priced at a steep $750 back in 1975, performs sonically.

Frequency Response:

With the Harman 2013 curve as compensation, when switching to third-party larger earpads, it shows an overall excellent flatness. There's about a 3dB gain between 300-500Hz, a small 4dB dip around 1-2KHz, and some airiness gain above 10KHz. Of course, to get closest to the original sound of these headphones, you'd need to use all the original parts, as earpads have a significant impact on sound. So we measured with the original earpads, but unfortunately, the firm pads did not maintain a good seal on the testing equipment, resulting in low-frequency roll-off due to leakage. And deliberately pressing the headphones for a mid-high frequency response also deviates from actual wearing.

However, by analyzing the existing data, we can still glean some information. For example, some of the airiness gain and mid-low frequency gain/mid-high frequency dip are likely due to the third-party larger earpads. If worn properly, with the original earpads or other types, we can achieve a flatter frequency response. This is a pair of headphones with high objectivity. Interestingly, the SR-5's sound vents are only arranged in the front half, directly facing the part that fits into the ear canal. Although different from some modern angled drivers, this is indeed a very useful detail (in fact, the SR-5 also has a slight angle). However, it's important to note that with this design, headphones must not be worn backwards, as the sound vents moving to the back of the ears will produce a completely different frequency response and sound odd.

SR-5  freq 大耳罩.jpg

SR-5  freq 原装耳罩.jpg

未命名_6.1.1.jpg

SR-5 raw avg大耳罩.jpg

SR-5 raw硬耳罩(泄露) 2.jpg


Harmonic Distortion:
The STAX SR-5 paired with the SRD-6 has OK distortion performance. At normal listening levels, low-frequency distortion is close to 1%, and the highest mid-high frequency distortion is around 0.3%. This level won't introduce too much audible harmonic distortion. However, compared to some modern well-designed electrostatic headphones, the parameter level is a bit higher. At louder volumes, low-frequency distortion significantly increases, but other frequencies remain below 1%, relatively clean. Under extreme testing, although other frequencies remain very clean, low-frequency distortion starts to get out of control, soaring above 10%.

dis SR-5 86DB&96DB&104DB L.jpg

dis SR-5 86DB&96DB&104DB R.jpg


This coincides with a compression roll-off in low-frequency response. Its maximum sound pressure level in the low frequencies is not very impressive. Regarding left-right distortion consistency, the right side has an additional mid-low frequency distortion peak, which may or may not be due to aging issues, but maintaining this level of sound quality is still quite remarkable.

SR-5 低频压缩 L.jpg


Cuckoo Studio mixing space:

demonstrating the sound with the third-party larger earpads. The slight midrange boost brings the main instruments and vocals forward, and the high-frequency airiness gain adds some volume to high-frequency percussion and breathy sounds. But the overall tendency towards flatness means the SR-5's soundstage doesn't deviate too much from an objective standard. The overall sound is still very close to an ideal flat playback environment. In terms of left-right consistency, there are some mismatches in the mid and mid-high frequencies with the larger earpads, but these are not present with the original earpads. Eliminating the variable of the larger earpads, the SR-5's left-right consistency is excellent, resulting in a solid central image.

SR-5-3D-Space-front-GIF.gif


Although the low-frequency performance is not great at high volumes, even producing compression roll-off, at normal listening levels, the controlled third harmonic distortion does not affect the cleanliness of the sound too much. Overall, the sound reproduction is very transparent and clean. Subjectively, it can produce a very dry and prominent midrange, with the sound hitting you “quickly”. The bass is not as cohesive as that of the newer HD600, appearing more brittle. To some extent, its very straightforward sound characteristics might even be more monitor-like (on a mixing level) than some modern monitoring headphones, fitting well with my imagination of the golden sound standard of that era.

SR-5-3D-Space-side-GIF.gif


The SR-5 did not continue to be produced for decades like some headphones, and in fact, I heard that STAX only produced about 25,000 units in the 20 years following its release, including subsequent models in this series. Newer models from the company have since relegated it to the sands of history. But this lightweight, minimalist in appearance, and flat-sounding SR-5 could have been considered top-tier in its day and even now, its sound quality doesn't seem outdated, carrying some advantages that seem to have been forgotten by some of today's similar headphones.
I heard that the original owner who passed the SR-5 on to Sandaimao had long since retired from the audiophile world, but fortunately, during those years of earnestly enjoying music, he really chose an outstanding headphone product.

SR-5_2.24.1.jpg


This is Cuckoo Studio Review.
I'll continue to explore the secrets of headphones with you.
 

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OP
Cuckoo Studio

Cuckoo Studio

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I really enjoy translating and sharing my reviews of interesting products from Chinese platforms on the ASR forum. Although there were some unpleasant parts in my last review of the MDR-Z1R, I will continue to share valuable content. This is because Amir and several key figures on the forum are very nice, and there are many people who look forward to these posts. I should ignore those who create unpleasantness without reason. I hope everyone enjoys reading them, and if there are any areas for improvement in language or technical aspects, I will continue to improve through friendly exchanges!
 
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Jimbob54

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Be interesting if you get any of the modern Stax offerings to compare.
 
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Cuckoo Studio

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Be interesting if you get any of the modern Stax offerings to compare.
In Amir's STAX SR-009S review, I shared the data for the SR-009 (without S) that I had tested before, which is another representative modern STAX device. It is indeed very clean.
 
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Cuckoo Studio

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Be interesting if you get any of the modern Stax offerings to compare.
Direct comparison for a better view.

SR-5 (3rd party earcups, can be better at midrange and LR consistency as mentioned above. )
SR-5 raw avg大耳罩.jpg

SR-009
STAX SR 009 raw 2.jpg


SR-5 harmonic distortion 104dBSPL
SR-5 dis perc.jpg

SR-009 harmonic distortion 104dBSPL
SR-009 dis perc.jpg
 
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solderdude

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Measured one too but with a self-biasing energizer. Converted that to a mains fed one as self biasing did not work that well.
This was measured with an early prototype of my fixture so not totally comparable.

Performance seems to be held back mostly by the small audio transformers.

sr5-srd-6.png


Aside from the bass response I was surprised how decent it sounded on music without bass in it.
 
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Cuckoo Studio

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Direct comparison for a better view.

SR-5 (3rd party earcups, can be better at midrange and LR consistency as mentioned above. )
View attachment 333112
SR-009
View attachment 333113

SR-5 harmonic distortion 104dBSPL @1KHz
View attachment 333108
SR-009 harmonic distortion 104dBSPL @1KHz
View attachment 333111
I didn't take apart the SR-5 for a photo shoot, but perhaps we can deduce some reasons for the elevated low-frequency distortion from the owner's descriptions: "Actually, the size of the SR5's driver is a bit smaller than the black mesh on the outside. If sir you are interested, you can actually see the driver after removing the ear pads and unscrewing the three small screws that are visible on the inside, which allows you to take off the inner shell. Previously, I noticed that the driver is only supported by three wires in the middle of an empty space. Therefore, when you pull on the headphone cord, the driver can shift slightly. Additionally, the dustproof film on the driver looks rainbow-colored under the light, which is quite attractive :D."
 
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Cuckoo Studio

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Measured one too but with a self-biasing energizer. Converted that to a mains fed one as self biasing did not work that well.
This was measured with an early prototype of my fixture so not totally comparable.

Performance seems to be held back mostly by the small audio transformers.

sr5-srd-6.png


Aside from the bass response I was surprised how decent it sounded on music without bass in it.
It looks like a compensated curve like Harman 2013 or 2018, right? I'm also curious about how the distortion performs on your headphones.
 

solderdude

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No target curve used.
Pure mic signal on pinnaless flatbed.

THD plot:
dist sr5.png

Don't have it anymore (measured it 10 years ago)
 

Ken1951

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I owned a pair of these back in the day. I was working for an audio chain that carried them and got an incredible deal. Kept them for about 6 months or so and enjoyed them quite a bit. Far better than any other headphone I heard at that time.
 

oleg87

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Listened to a pair of these a couple years back. No one familiar with Stax should be surprised that headphones this old sound as good as they do, but like most Stax I've tried, not really a headphone I'd want to actually own - didn't get a great fit, with a bass-lean and somewhat piercing sound for my tastes.
 

Rja4000

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I remember the Stax SR-5 very well.
They were the holy grail for me, at the time.
I couldn't afford them, so I bought the much cheaper SR-44 instead.
They were my very first transducers, long before I could afford any (decent) loudspeakers.
I still own them and they still work.
 

Theodore8

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Thank you @Cuckoo Studio for this very informative review! Wonderful to see the state-of-the-Art of half a century ago being measured.

If you have time, I would have two questions :

1. Where did you find replacement earpads?

2. Which modern day electrostats would you consider as roughly in the same class of performance ?

Thank you again!
 

peniku8

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Measured one too but with a self-biasing energizer. Converted that to a mains fed one as self biasing did not work that well.
This was measured with an early prototype of my fixture so not totally comparable.

Performance seems to be held back mostly by the small audio transformers.

sr5-srd-6.png


Aside from the bass response I was surprised how decent it sounded on music without bass in it.
Flat plate should be somewhat ok accuracy wise up to about 1khz. I'm surprised to see that channel mismatch in the bass in both of the measurements here, have you dug into the earpads to see if it was maybe a seal issue? If you can still remember :D
 

solderdude

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It was about 10 years ago ...
Could be pads (the thing was old) could be the transformer as well.
I did not investigate it further.
 

jgreen7756

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Hello...I'm new at this, but know that Stax is legendary....I purchased an SR-5/ SRD-6 adaptor set in fantastic condition......My question is- I'm in US, and the adapter has a European 3 prong plug...Is it as easy as just putting on a US plug? Do I need it to be a 3 prong type?....Any help would be greatly appreciated
 

solderdude

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yes, just put on a US plug for the SRD-6.
The mains cable is 2 wire so best to use a 2-wire plug as a 3-prong plug would suggest the metal enclosure is grounded, which it isn't.

Should you be replacing the mains cable then you can mount a 3-wire cable and connect the safety ground wire to the metal enclosure.
 

jgreen7756

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yes, just put on a US plug for the SRD-6.
The mains cable is 2 wire so best to use a 2-wire plug as a 3-prong plug would suggest the metal enclosure is grounded, which it isn't.

Should you be replacing the mains cable then you can mount a 3-wire cable and connect the safety ground wire to the metal enclosure.
Wow!...thanks for the quick response...thats a huge relief!...i also meant to ask how connect the adapter to an older 70's realistic amp?
 
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