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RAAL requisite CA-1a Headphone Review

Rate this headphone:

  • 1. Poor (headless panther)

    Votes: 169 82.4%
  • 2. Not terrible (postman panther)

    Votes: 24 11.7%
  • 3. Fine (happy panther)

    Votes: 7 3.4%
  • 4. Great (golfing panther)

    Votes: 5 2.4%

  • Total voters
    205

Maiky76

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This is a review, listening tests and detailed measurements of the RAAL requisite CA-1a "true ribbon" headphone. It is on kind loan from a member and costs US $2,500.
View attachment 235714
While the RAAL SR1a required a massive power amplifier, the revised transformer can be driven from a high-power headphone amplifier which is a major improvement. The CA-1a feels more comfortable in hand but looks primitive and more like a prototype than real production. The pad especially gives that feeling as it looks like cheap open cell foam that would fall apart if left in the sun for a few days! Two sets of pads are provided: one provides full seal and the other has slots above and below.

Headband only has two sets of adjustments. While this mostly fit my head, it may not be enough range for everyone. Comfort was good except the pad was a bit rough against my skin.

RAAL CA-1a Measurements
I set up the headphone a few days ago and compared the two pads:
View attachment 235715

Both responses look terrible but at least the closed one has more conformant bass response. I think the company positions this for "gamers" and the open slot one for music.

Tonight I made a few more refinements and got ever so slightly response with closed pad which I use for the rest of the tests:
View attachment 235716

What on earth were they thinking here? That such a large chunk of the response should be taken out from 1 kHz to nearly 5 kHz? What research led them to thinking this is correct? Maybe that is why they thought the open pads sound better as the bass will overwhelm the response in treble region.

Relative response shows the large correction you need with a shape that is not easy to replicate with a parametric EQ by eye:
View attachment 235717

Distortion in bass and even midrange was extremely high:
View attachment 235718

But extremely low in higher frequencies:
View attachment 235719

Feels like a tweeter that is being told to play full range.

Drivers are slanted which may be the reason for the very messy group delay:
View attachment 235720

Given the transformer box, I did not attempt to measure its impedance. But did test for sensitivity:
View attachment 235721

Still a hungry headphone but so much more efficient than SR1a. The Topping A90 had no trouble driving it to 94 dBSPL using low gain so this is good.

Raal CA-1a Listening Tests
I used my RME ADI-2 Pro to drive the Topping A90 which in turn drove the Raal. Lack of high frequency response was so bad that it smacked you in the face! It became even more obvious when I compensated for it with EQ and then turned it off:
View attachment 235722

Without EQ, it sounds like someone stuffed some towels between it and your ear. Fortunately, EQ highly elevates the response even in the simple form I have above. Spatial qualities are excellent and high frequency detail was extremely clean and enjoyable. With the bit of bass boost I added, there was plenty of that region as well. Fidelity was very nice now and I was anxious to experience more of my reference library.

I was worried about distortion and it is indeed there. It comes in the form of ticks and then messiness/grunginess in response. Fortunately you get plenty of volume before that happens and the onset is gradual. You just don't have extra headroom on top of that to blast your ears and shorten their life. :) Max usable volume with Topping A90 in high gain was 12:00 o'clock.

Conclusions
The objective measurements show a very faulty response. Given the extra box, one would think that they could put in a passive equalizer in there to compensate but they have not. The sound as such is horrid with somewhat limited dynamic range. Add a bit of EQ though and the CA-1a wakes up to something wonderful. Angled drivers provide very good spatial qualities and lack of distortion in the comfortable range for the driver provides very good fidelity.

As is, I can't recommend the Raal requisite CA-1a. But if you have to have it, use the EQ above and you will transform it to sound excellent. Whether that is the right thing on top of spending so much money is up to you.

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

I think the EQ is missing one biquad when compared to the graph.

Here are some thoughts about the EQ.

Notes about the EQ design:

  • The average L/R is used to calculate the score.
  • The resolution is 12 points per octave interpolated from the raw data (provided by @amirm)
  • A Genetic Algorithm is used to optimize the EQ.
  • The EQ Score is designed to MAXIMIZE the Score WHILE fitting the Harman target curve (and other constrains) with a fixed complexity.
    This will avoid weird results if one only optimizes for the Score.
    It will probably flatten the Error regression doing so, the tonal balance should be therefore more neutral.
  • The EQs are starting point and may require tuning (certainly at LF and maybe at HF).
  • The range around and above 10kHz is usually not EQed unless smooth enough to do so.
  • I am using PEQ (PK) as from my experience the definition is more consistent across different DSP/platform implementations than shelves.
  • With some HP/amp combo, the boosts and preamp gain (loss of Dynamic range) need to be carefully considered to avoid issues with, amongst other things, too low a Max SPL or damaging your device. You have beed warned.
  • Not all units of the same product are made equal. The EQ is based on the measurements of a single unit. YMMV with regards to the very unit you are trying this EQ on.
  • I sometimes use variations of the Harman curve for some reasons. See rational here: https://www.audiosciencereview.com/...pro-review-headphone.28244/page-5#post-989169
  • https://www.audiosciencereview.com/...pro-review-headphone.28244/page-6#post-992119
  • NOTE: the score then calculated is not comparable to the scores derived from the default Harman target curve if not otherwise noted.
Good L/R match.

I have generated one EQ, the APO config file is attached.

Score no EQ: 27.8
Score Amirm: 52.3 missing one Biquad
Score with EQ: 78.0

Code:
Raal requisite EQ [email protected] 96000Hz
October102022-110032

Preamp: -12.7 dB

Filter 1: ON PK Fc 54.96 Hz Gain 3.44 dB Q 0.60
Filter 2: ON PK Fc 144.59 Hz Gain -2.12 dB Q 0.62
Filter 3: ON PK Fc 1057.79 Hz Gain -2.64 dB Q 2.02
Filter 4: ON PK Fc 1750.51 Hz Gain 3.74 dB Q 2.03
Filter 5: ON PK Fc 2869.24 Hz Gain 12.08 dB Q 1.05

Raal requisite EQ Design.png

EDIT:
FUll EQ: score: 93.5

Code:
Raal requisite EQ Full [email protected] 96000Hz
October102022-115904

Preamp: -11.7 dB

Filter 1: ON PK Fc 52.46 Hz Gain 3.71 dB Q 0.42
Filter 2: ON PK Fc 146.18 Hz Gain -3.25 dB Q 0.51
Filter 3: ON PK Fc 1097.64 Hz Gain -6.44 dB Q 1.02
Filter 4: ON PK Fc 1777.35 Hz Gain 2.06 dB Q 1.81
Filter 5: ON PK Fc 3053.21 Hz Gain 12.94 dB Q 0.40
Filter 6: ON PK Fc 5232.39 Hz Gain -7.52 dB Q 2.73

Raal requisite EQ Full.png
 

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Toni Mas

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Reading this and so many other headphone reviews, it looks like manufacturers do not really take target matching as a mandatory requirement... Bass is almost always lacking, and as for the rest of the response situation is even worse... It even seems that many manufacturers don't care a damn about target matching...

I consider myself happy enough with my Beyer DT880 600 ohm, though I thought their top of the range Tesla models might bring an improvement... But condidering the awfull measurements shown by some reviewers, I wonder what kind of "improvement" i can exactly expect from such "upgrade"...
 

Robbo99999

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Reading this and so many other headphone reviews, it looks like manufacturers do not really take target matching as a mandatory requirement... Bass is almost always lacking, and as for the rest of the response situation is even worse... It even seems that many manufacturers don't care a damn about target matching...

I consider myself happy enough with my Beyer DT880 600 ohm, though I thought their top of the range Tesla models might bring an improvement... But condidering the awfull measurements shown by some reviewers, I wonder what kind of "improvement" i can exactly expect from such "upgrade"...
Well, you can't force all manufacturers to target the Harman Headphone Curve for all or indeed any of their headphone models - in fact it might be a bit silly if every headphone out there was tuned to the Harman Curve at stock, as for one it wouldn't satisfy the different bass levels that people could prefer in their headphones, as the Harman Research showed that people generally liked the Harman Curve but with different bass levels, although most did prefer the bass level of the Harman Curve, which is why they chose that as their target curve....it was just that the level of bass was the main difference in preference between their test subjects. Most headphones acknowledge at least the very general shape of the Harman Curve, like most have somekind of a rise at 3kHz when measured on the GRAS rig. I'm a bit undecided if I'd like to see all manufacturers target the Harman Curve, eventhough I do EQ all my headphones to the Harman Curve, I'm just a bit undecided on whether I'd want them all to target it.......I don't think I would, I think I'd like to see them retain their freedom and own ideals, if their ideals do coincide with the Harman Curve, then sure they should produce them to variations on the Harman Curve (like variations in bass level, and perhaps also subtle variations in the 3kHz hump).
 

Toni Mas

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Well, you can't force all manufacturers to target the Harman Headphone Curve for all or indeed any of their headphone models - in fact it might be a bit silly if every headphone out there was tuned to the Harman Curve at stock, as for one it wouldn't satisfy the different bass levels that people could prefer in their headphones, as the Harman Research showed that people generally liked the Harman Curve but with different bass levels, although most did prefer the bass level of the Harman Curve, which is why they chose that as their target curve....it was just that the level of bass was the main difference in preference between their test subjects. Most headphones acknowledge at least the very general shape of the Harman Curve, like most have somekind of a rise at 3kHz when measured on the GRAS rig. I'm a bit undecided if I'd like to see all manufacturers target the Harman Curve, eventhough I do EQ all my headphones to the Harman Curve, I'm just a bit undecided on whether I'd want them all to target it.......I don't think I would, I think I'd like to see them retain their freedom and own ideals, if their ideals do coincide with the Harman Curve, then sure they should produce them to variations on the Harman Curve (like variations in bass level, and perhaps also subtle variations in the 3kHz hump).
I am also recently giving a try to DSP eq my DT880, and I admit that for the moment it sounds at least interesting. Trouble is that to do so, I have to trust someone else's measurements and Eq choices, which I find a bit frustrating. After all not all units have to sound the same, (especially on any head/pair of ears), I also changed the ear pads for "equivalent" ones but not really the same as originals, it is also obvious the the sound changes depending on how I wear them, etc... And btw, I also own other headphones that sound different too, but are also enjoyable...
 

Robbo99999

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I am also recently giving a try to DSP eq my DT880, and I admit that for the moment it sounds at least interesting. Trouble is that to do so, I have to trust someone else's measurements and Eq choices, which I find a bit frustrating. After all not all units have to sound the same, (especially on any head/pair of ears), I also changed the ear pads for "equivalent" ones but not really the same as originals, it is also obvious the the sound changes depending on how I wear them, etc... And btw, I also own other headphones that sound different too, but are also enjoyable...
Yes, you hit on some of the variables & limitations of using EQ's, and indeed also if you change the pads.
 

deafenears

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Reading this and so many other headphone reviews, it looks like manufacturers do not really take target matching as a mandatory requirement... Bass is almost always lacking, and as for the rest of the response situation is even worse... It even seems that many manufacturers don't care a damn about target matching...
Well, you can't force all manufacturers to target the Harman Headphone Curve for all or indeed any of their headphone models - in fact it might be a bit silly if every headphone out there was tuned to the Harman Curve at stock, as for one it wouldn't satisfy the different bass levels that people could prefer in their headphones, as the Harman Research showed that people generally liked the Harman Curve but with different bass levels, although most did prefer the bass level of the Harman Curve, which is why they chose that as their target curve....it was just that the level of bass was the main difference in preference between their test subjects. Most headphones acknowledge at least the very general shape of the Harman Curve, like most have somekind of a rise at 3kHz when measured on the GRAS rig. I'm a bit undecided if I'd like to see all manufacturers target the Harman Curve, eventhough I do EQ all my headphones to the Harman Curve, I'm just a bit undecided on whether I'd want them all to target it.......I don't think I would, I think I'd like to see them retain their freedom and own ideals, if their ideals do coincide with the Harman Curve, then sure they should produce them to variations on the Harman Curve (like variations in bass level, and perhaps also subtle variations in the 3kHz hump).
At the same time, it is limited in terms of tools available to tune headphones, IIUC. Making changes to say boost one band may and more than likely affect another, or the others. Then there's reflections. This is where Dan Clark's AMTS comes in, it's a true game changer and really innovative approach to tuning.

Also, as @Robbo99999 points out, different people have different preferences. Far easier to make it up to the user to EQ to taste. Of course, I would say to try match a target, be it Harman or the manufacturer's own house sound/target as best as you can and leave the rest for EQ.
 

Robbo99999

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At the same time, it is limited in terms of tools available to tune headphones, IIUC. Making changes to say boost one band may and more than likely affect another, or the others. Then there's reflections. This is where Dan Clark's AMTS comes in, it's a true game changer and really innovative approach to tuning.

Also, as @Robbo99999 points out, different people have different preferences. Far easier to make it up to the user to EQ to taste. Of course, I would say to try match a target, be it Harman or the manufacturer's own house sound/target as best as you can and leave the rest for EQ.
Yes, I don't think it's particularly easy to tune headphones, although of course it might be easy for manufacturers once they know how to model it (I guess they do), but I think for sure it's not easy to delicately manipulate all areas of the frequency response to the exact response you're after, which is like you say where Dan Clarke's Stealth & Expanse seem particularly innovative in being able to do this.
 

xnor

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It shows again that the audibility of hamonic distortion gets usually overestimated, would be interesting to see some multitone distortion comparisons with better HD measuring headphones as my guess is that those might correlate better with audibility.
FR, as always, dictates sound over other metrics by a long shot.
 

GaryH

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That shows again that the audibility of hamonic distortion gets usually overestimated, would be interesting to see some multitone distortion comparisons with better HD measuring headphones as my guess is that those might correlate better with audibility.
Actually the opposite was found in blind listening tests by Steve Temme and Sean Olive:
there appears to be some moderate positive correlations between the amount of THD measured in the headphones and their sound quality rating
in these tests multitone distortion was not a good predictor of audible distortion in the headphones
Although neither showed high correlation:
none of the headphone distortion measurements could reliably predict listener preference ratings based on audible distortion
The most promising was actually non-coherent distortion (which I believe could be measured with the Audio Precision Analyzer) using real music as the test signal:
non-coherent distortion based on music appears to be more correlated with listeners’ preference ratings than the THD, IM and Multitone
 
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thewas

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Actually the opposite was found in blind listening tests by Steve Temme and Sean Olive:
I was sure that paper would come ;), the problem is that IMD/multitone distortion is not easy to standardise, so you can have several spectra and metrics with very different values.

This video shows that components which are further from the masking band are more audible and this usually happens at transducers more with multitone than with HD https://www.audiosciencereview.com/...-distortion-components-in-loudspeakers.38183/

The most promising was actually non-coherent distortion (which I believe could be measured with the Audio Precision Analyzer) using real music as the test signal:
Which is non harmonic distortion, as mutltitone components are.
 

xnor

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Actually the opposite was found in blind listening tests by Steve Temme and Sean Olive:
Although neither showed high correlation:
They didn't eliminate variables like differences in weight, clamping force, padding, headband... did they?
Because if not, then a test with just 5 headphones that doesn't show anything other than perfect correlation is gonna be pretty useless.
You could probably find non-sound quality related features with stronger correlation to sound quality rating using such a test configuration.

The most promising was actually non-coherent distortion (which I believe could be measured with the Audio Precision Analyzer) using real music as the test signal:
A transfer function measurement is not gonna help if you want to analyze distortion.
Also, this result refutes the conclusion that the correlation was due to a causal relationship between distortion and sound quality ratings: artificial test signals like multitone signals can make distortion products far easier to perceive than music. Also, music is gonna highlight deficiencies in FR due to reflections, resonances ... (that cannot be entirely eliminated with EQ) much more strongly than a multitone signal with a "sparse" spectrum.

Both points support that the opposite of the opposite is more likely true. ;)
 

xnor

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Regarding IMD standardization, measurement, audibility:
How to calculate IMD is well-defined. Testing can be done with just two fixed tones. Either one can be swept. Audibility can be maximized / masking can be eliminated by choosing the frequencies appropriately. All the info can be found in 20+ year old psychoacoustics research.

Also, HD and IMD basically share the same underlying causes .. all that's different are the proportions. Where there's HD there's also gonna be IMD.

But as always, when talking about distortion, people ignore that e.g. 1% 2nd HD is not audible at high SPL but clearly audible at low SPL ... and since HD is proportional to SPL in most audio devices, audibility is usually a non-issue.

That's why FR is king. Always has and always will be.
 

GaryH

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I was sure that paper would come ;), the problem is that IMD/multitone distortion is not easy to standardise, so you can have several spectra and metrics with very different values.

This video shows that components which are further from the masking band are more audible and this usually happens at transducers more with multitone than with HD https://www.audiosciencereview.com/...-distortion-components-in-loudspeakers.38183/


Which is non harmonic distortion, as mutltitone components are.
IMD, multitone distortion, BSR...none of these metrics matter to sound quality unless a correlation with audibility in blind listening tests has been demonstrated.
 
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GaryH

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They didn't eliminate variables like differences in weight, clamping force, padding, headband... did they?
The different headphones were presented virtually to listeners via binaural recordings of the headphones reproduced through a calibrated low-distortion reference headphone, Stax SR-009. This virtual headphone test method minimized headphone leakage effects, and removed the influence of nonauditory biases (brand, price, visual appearance, comfort, etc.) from listeners’ judgment of sound quality.
;)
A transfer function measurement is not gonna help if you want to analyze distortion.
https://www.aes.org/e-lib/browse.cfm?elib=14381 ;)
 

xnor

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GaryH

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That was the method used to measure the non-coherent distortion in the paper I originally linked.
 
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Actually the opposite was found in blind listening tests by Steve Temme and Sean Olive:
I wouldn't put a lot of weight on a limited one-off test like that. Unlike linear frequency response errors, hearing non-linear distortion requires skill. Proper testing usually involves listening training and filtering out those who do not have critical listening skills. In addition, there is infinite variation in distortion in headphones. And such distortion may very well be level dependent. So let's not run with the conclusions there.
 

thewas

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IMD, multitone distortion, BSR...none of these metrics matter to sound quality unless a correlation with audibility in blind listening tests has been demonstrated.
That they are audible at some amount is undoubted, what is missing (same with HD) is a precise model and metic regarding the audibility limits.
 
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