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

[mitchco]

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.

[mitchco]

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:

 

 

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:

 

 

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

 

 

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:

 

 

Sure enough.

 

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

 

 

And the measurement result:

 

 

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

 

 

Identical.

 

Phase response:

 

 

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.