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    The Computer Audiophile

    Taking The RAAL-requisite SR1a and SR1b Headphones to the Pinnacle

     

     

    Audio: Listen to this article.

     

     

    Members of the Audiophile Style community are well aware that I absolutely love my RAAL-requisite SR1a true ribbon headphones. I was floored by them in my initial review, and fell in love with them even more after using an FIR correction filter developed by Mitch Barnett (@mitchco) of Accurate Sound. Two years later, I believe we're at the absolute peak of SR1a and SR1b performance because of a new FIR filter just released by Accurate Sound. 


    Earlier this Spring I was exchanging emails with Mitch Barnett about the RAAL-requisite CA-1a headphones and the fact that I was using a new product (TI-1b) from the company that enabled me to use a "traditional" headphone amplifier, rather than a full blown loudspeaker amp with the inefficient power amp to headphone interface box. During this conversation I mentioned to Mitch that I could also use this new TI-1b interface with the SR1a headphones, but the configuration required use of additional open baffle compensation adapters. After trying this I was somewhat underwhelmed with the sound quality. 

     

    That's when Mitch told me he wanted to get the SR1b headphones in to measure and that this would enable him to develop a filter with open baffle compensation built-in. Whoa, talk about a giant win-win. This would open up the SR1a and SR1b to the world of high end headphone amps without the need for the less than stellar OB adapters! A couple weeks later Mitch received the headphones from Danny at RAAL-requisite, and went to work.

     

    In early May, Mitch sent me some filters to test. He made sure to remind me that developing filters was an iterative process, and that a couple of them were probably on the edge of acceptability. In other words, in addition to a neutral filter, he wanted to create one that would extend the SR1a/b's bass a bit further and the only way to know when a filter has been taken too far, is to take it too far. 

     

    A couple days ago I finally had time to sit down with four new filters that Mitch designed. After some critical listening and listening for pure enjoyment, it was easy for me to select the two winners. The new neutral filter and the one Mitch calls neutral plus bass extension, were easily the best. Don't take that solely from me, Mitch had settled on those two as well, but didn't tell me until after I rendered an opinion. The two filters that didn't make the cut, pushed the bass beyond the limits of my own taste and likely beyond the taste of everyone except the guy who rattles my house when he drives by every day. 

     

     

    Raal SR-1b frequency response Red measured Green and Blue corrected.jpg

     

     

     

    Where It's At

     

    To recap where we're at, I'm using the new SR1b neutral convolution filter that has open baffle compensation built in. This enables me, and anyone else, to use the SR1a and SR1b headphones with the TI-1b and almost any high end headphone amp, without using the open baffle adapters. Based on my personal experience, this is a huge deal! Let me tell you how I came to this conclusion. 

     

    My current headphone setup is absolutely stunning. A full review of components is coming after the Munich show. I'm using the full dCS Lina stack, including the Lina Network DAC, Master Clock, and Headphone Amplifier to feed the RAAL-requisite SR1a and CA-1a headphones. The TI-1b enables the Lina to drive these headphones perfectly. Feeding power to all three dCS Lina components is a new Shunyata Gemini Model-4 high performance power conditioner and advanced ground noise reduction hub. I just received the perfectly-sized Gemini and have only enjoyed the power conditioning to this point. I look forward to taking advantage of the ground noise reduction in the coming weeks.  

     

    I loaded the new neutral SR1b filter into Roon, connected my SR1a headphones and let the Boston Symphony Orchestra's performance of Shostakovich Symphony No. 1 rip. WOW! The sound is not only "Next Level" it has reach the pinnacle. No more loudspeaker power amp(s), speaker interface box, or XLR open baffle barrel connectors required. Removing these devices is truly removing impediments to better sound quality. Baffle compensation built into the new convolution filter, combined with a summit level headphone system, delivers performance at an Everest level. 

     

    I conducted far too many A/B/C comparisons between the new neutral filter and the "old" ways of doing SR1a business. Every time I put either the OB XLR adapters into the Lina system or went to a system using the speaker interface box, I was extremely let down by what I heard. Keep in mind that the speaker interface box and some top quality loudspeaker amplifiers brought my listening to new heights a couple years ago. Now that I've heard these headphones at their peak performance, I can't un-hear the coloration and dynamic range constriction of the open baffle adapters or the speaker interface box. I never want to go back to system with these physical barriers to better sound. Such is life. The best system is only the best until something new knocks it off the hill. 

     

    BSO.jpgListening to Andris Nelsons / Boston Symphony Orchestra performance of Shostakovich Symphony No. 1 through my headphone system with the new SR1b filter, delivers an unforgettable experience. From the opening horns and delicate strings to the bombastic percussion that ranges from low to booming levels, with varying degrees of transient attack, it is all reproduced with as much perfection as I've ever heard. I've literally listened to the 9:27 Allegretto - Allegro non troppo fifteen times in the last few days. It offers everything from delicacy to texture to tone to transients that open one's eyes. This new custom filter designed by Mitch Barnett is what enables me to hear each aspect of this recording individually and as a whole, on a level I can only call the pinnacle. 


    Details: The new filter works with both the SR1a and SR1b. It's available now for $200. Lucky listeners who previously purchased the original SR1a filters from Accurate Sound can pick up the new filters for $50. Reach out to Mitch and he'll take care of you.

     

    Here's a link to the new filters at Accurate Sound (link)

     

     

    SR1a-SR1b-Filter-OB-Built-In-HERO.jpg




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    Particularly interested in your findings with the dCS Lina Network DAC. Especially as a DAC/Streamer combination. Steve Huff in his review preferred the internal streamer of the Lina vs. going external via the Grimm Audio MU1! dCS has its stuff in order.

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    The new Tl-1b adapter gets you closer to the very best RAAL SR1a sound, which is with the RAAL VM-1a tube headphone amp. The TL-1b is extremely good and much better than the old RAAl adapter box. I use the TL-1b with a CODA #16 and a modded PeachTree GAN1 (great amp). You can also run very long cable from the amp to the TL-1b and then have a short headphone cable to the phones. My long wire is 25-foot and the headphone cable is 6-foot. All these cables are from RAAL so I know they will work for the intended purpose.

     

    I have Mitch's filters but do not use them with the VM-1a. I used to use them with my old adapter box. I will consider them again with the CODA#16 and the PeachTree.

     

    A nice DAC/streamer combo with the SR1a or CA-1a is the Lumin X1 DAC/Streamer. I am in the process of upgrading that DAC and streamer to the Playback Designs Dream DAC and PBD Stream-IF streamer. The Stream-IF is the best streamer I have owned. A bit better than the Sonore OpticalRendu and Lumin X1 (both used fibre). Though I am not even using the very best part of the Streamer-IF, the fibre optical Plink. The SPDIF to my Benchmark DAC3B is amazing via the Stream-IF.

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    @mitchco, why is the FR of the SR1a so much different from the SR1b above 3k? My understanding is that these two headphones only have minor differences like the grille and a bit of silver wire.

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    11 hours ago, adornoWest said:

    @mitchco, why is the FR of the SR1a so much different from the SR1b above 3k? My understanding is that these two headphones only have minor differences like the grille and a bit of silver wire.

     

    Mitch answered here

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    12 hours ago, adornoWest said:

    @mitchco, why is the FR of the SR1a so much different from the SR1b above 3k? My understanding is that these two headphones only have minor differences like the grille and a bit of silver wire.

     

    Just to complete the answer here: The SR1a was measured with open baffle compensation in the circuit, so it is not going to look the same as the raw response I measured without the baffle step in the SR1b. So the attached graph is what is added to the SR1a raw measurement versus without open baffle comp of SR1b. If I “convolve” the SR1b measurement with the open baffle compensation, it comes within 1 dB of the original measurement I made of the SR1a’s two years ago. Says a lot about the quality of engineering and manufacturing of the drivers from Raal. Also, the horizontal scale is different in the two measurement charts. So not exactly an apples-to-apples comparison.

    Raal SR-1b baffle step compensation only.jpg

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    3 minutes ago, cfisher said:

    Chris, thanks so much for writing about Mitch's new filters. It's hard to believe that there was more clarity and detail to wring out of the SR1a. That is undoubtedly the best $50 I have ever spent on my stereo. Thanks, Mitch, for keeping at it!

    Isn’t it just crazy? Crazy cool that $50 can get you an upgrade larger than some that cost $50,000. 

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    1 minute ago, The Computer Audiophile said:

    Isn’t it just crazy? Crazy cool that $50 can get you an upgrade larger than some that cost $50,000. 

     

    Without question, it is a component-level upgrade. Being, by profession, on the frugal side of Hi-Fi, I really appreciate it. 

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    Chris, you are using the filters in Roon despite the apparent tap bug? Have you compared how the filters sound in Roon and HQPlayer?

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    Is it possible to use the filters in HQP along with the DCS Equipment?

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    14 hours ago, cfisher said:

    Chris, you are using the filters in Roon despite the apparent tap bug? Have you compared how the filters sound in Roon and HQPlayer?

    Yeah, still doing it with Roon despite the bug. I need to get HQP 5 and test. 

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    Just now, The Computer Audiophile said:

    Yeah, still doing it with Roon despite the bug. I need to get HQP 5 and test. 

     

    I just tried with an evaluation version of HQP 5 (still on 3) and it didn't seem like Roon was corrupting the filter in any way. Obviously, don't want to get into a Roon vs. HQP discussion.

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    1 hour ago, mitchco said:

    Hi @cfisher I agree. I listened to the SR-1b FIR filters in Roon's convolution engine, HQP, JRiver, and HLC. I could not hear a difference,

     

    I wanted to take it a bit further and measure Roon's convolution engine to see if the filter is being corrupted in anyway,

    The short answer is no.

     

    I used REW to generate a "sweep" file that could be played in Roon. A 5 Hz to 22,050 Hz, 44.1 kHz sweep file was played in Roon with no convolution (or any other DSP) applied. I used BlackHole as a virtual loopback driver to route the output of Roon back into REW's input to be measured. This is a "control" test to see that we get the "expected" flat frequency and phase response:

     

    Roon control test - no DSP.jpg

     

    Sure enough, perfectly flat frequency and phase response.

     

    Next I loaded a "test" high resolution headphone FIR filter at 65,536 taps into Roon's convolution engine. I noted that while the sweep was playing Roon displayed the "bug" of 22K taps:

     

    Roon convolution.png

     

    Of course, it should be displaying 65,536 taps or 66K in Roon speak. And the measurement:

     

    Roon convolution engine test FIR filter.jpg

     

    I made the test headphone filter complex to test any inconsistencies. Lets compare using another convolver.

     

    I setup a test where the output of Roon is going into BlackHole, but the output of BlackHole is going into the input of Hang Loose Convolver (HLC) and the output of HLC, using another virtual audio driver called Ground Control, routes the output back into the input of REW. I loaded HLC with a Dirac pulse 65,536 tap FIR filter, which is a "do nothing" FIR filter so we can see that again, as a control test, we get  the expected flat frequency and phase response:

     

    Roon with no DSP feeding into HLC with Dirac pulse FIR filter.jpg

     

    Sure enough.

     

    Now loading the same test FIR filter, we see HLC correctly reporting 65,536 taps:

     

    HLConvolver.png

     

    And the measurement result:

     

    Roon with no DSP feeding HLC with test FIR filter hosted in HLC.jpg

     

    Looks the same as Roon's convolver test. Lets make sure by overlaying the results. Frequency response:

     

    Roon convolution vs HLC convolution.jpg

     

    Identical.

     

    Phase response:

     

    Roon convolution vs HLC convolution Phase.jpg

     

    Identical.

     

    Conclusion: While Roon may have a convolution bug of some sort, it is definitely not affecting or corrupting the frequency or phase response of these high resolution headphone FIR filters.

     

    Back to listening to music.

     

    I’m glad my ears were right for once :~)

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    Hi all.
    I have a RAAL Sr-1a with Jotenhiem amp for sale .... PM if interested.
    +972-54-9333389

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    Jacob, hope you are ok. I'm catatonically refreshing my Haaretz feed here in the US. What are you replacing the RAALs with?

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