AHB2 Mono v Stereo - what is audible?

[restorer-john]

If nothing else, the thread has introduced a number of members to ABXing.

I wonder how both files' sha1 can be different, but still play fine...

Both files get a new hash when Foobar uses "replay gain" to level match them for the ABX. If you don't use replay gain, the hashes will be the same as the unmatched file and not level matched. That is my understanding.

 

[Pdxwayne]

If nothing else, the thread has introduced a number of members to ABXing.



Both files get a new hash when Foobar uses "replay gain" to level match them for the ABX. If you don't use replay gain, the hashes will be the same as the unmatched file and not level matched. That is my understanding.

View attachment 136235

My initial thought was the same as you.

I just downloaded the files to Ubuntu box and checked the sha1 of both files.

The sha1 are the same as those shown in your original results and a few other results from today.

Since all of the results shown replaygain adjustment, it meant replaygain is not changing the SHA1 of the test files IF it was applied when doing ABX.

Regarding my results from yesterday, which had different SHA1....I think it was because I applied replaygain to the files separately，before I ran ABX.

 

[preload]

If nothing else, the thread has introduced a number of members to ABXing.

More like how NOT to do ABX. If the two files were captured in such a way that audible artifacts like wind noise are added, it completely invalidates the results.

 

[pjug]

More like how NOT to do ABX. If the two files were captured in such a way that audible artifacts like wind noise are added, it completely invalidates the results.

Some of us (me at least) hadn't tried Foobar ABX at all before this, though. It isn't too late to try to get captures of speaker voltage. I'd be happy to make a filter approximating the AHB2 response with Stereophile's simulated speaker load and what I guess the mono response would be, if anyone wants to try doing this just with computer generated files.

 

[restorer-john]

My initial thought was the same as you.

I just downloaded the files to Ubuntu box and checked the sha1 of both files.

The sha1 are the same as those shown in your original results and a few other results from today.

Since all of the results shown replaygain adjustment, it meant replaygain is not changing the SHA1 of the test files IF it was applied when doing ABX.

Regarding my results from yesterday, which had different SHA1....I think it was because I applied replaygain to the files separately，before I ran ABX.

That makes sense.

 

[restorer-john]

More like how NOT to do ABX. If the two files were captured in such a way that audible artifacts like wind noise are added, it completely invalidates the results.

By all means present your similar recording efforts for our scrutiny. I'm sure they will be superior in all respects.

 

[preload]

By all means present your similar recording efforts for our scrutiny. I'm sure they will be superior in all respects.

There are plenty of examples of abx files for use with foobar abx comparator on ASR. I also wouldn't design an experiment to test two amps using a mic anyway. As another member suggested, recording the signal/music/whatever at the speaker terminals would generate a more precise set of files.

 

[pjug]

Attached is a filter for Audacity, approximating the AHB2 response into the Stereophile simulated speaker load. A think the difference between this and flat should be about the same as the difference between AHB2 stereo and AHB2 mono. So apply this filter to a track and see if you can tell the difference in an ABX test. Here is the spectra delta of two files where I applied the filter to one. It pretty much gives the filter shape as confirmation. File difference is about -70dB so seems it will be tough to hear a difference but maybe someone can do it. I used a 2L music file for this but you can apply the filter to music you are familiar with.

 

[Blumlein 88]

Attached is a filter for Audacity, approximating the AHB2 response into the Stereophile simulated speaker load. A think the difference between this and flat should be about the same as the difference between AHB2 stereo and AHB2 mono. So apply this filter to a track and see if you can tell the difference in an ABX test. Here is the spectra delta of two files where I applied the filter to one. It pretty much gives the filter shape as confirmation. File difference is about -70dB so seems it will be tough to hear a difference but maybe someone can do it. I used a 2L music file for this but you can apply the filter to music you are familiar with.

View attachment 136241

For someone younger than myself and with good clean gear I think that might be just noticeable on an ABX test with at least some types of signals. It isn't going to sound a night and day difference.

 

[preload]

Attached is a filter for Audacity, approximating the AHB2 response into the Stereophile simulated speaker load. A think the difference between this and flat should be about the same as the difference between AHB2 stereo and AHB2 mono. So apply this filter to a track and see if you can tell the difference in an ABX test. Here is the spectra delta of two files where I applied the filter to one. It pretty much gives the filter shape as confirmation. File difference is about -70dB so seems it will be tough to hear a difference but maybe someone can do it. I used a 2L music file for this but you can apply the filter to music you are familiar with.

View attachment 136241

What parameters did you use to simulate the ahb2? Just output impedance? Also did you by chance add in LCR parameters for a simulated 12ga speaker cable?

 

[pjug]

What parameters did you use to simulate the ahb2? Just output impedance? Also did you by chance add in LCR parameters for a simulated 12ga speaker cable?

I just tried to copy the curve from the Stereophile AHB2 review. I don't think this considers cable. We could make our own curve for real speakers and include cable since Soundstage showed output impedance vs freq.

 

[restorer-john]

I just tried to copy the curve from the Stereophile AHB2 review. I don't think this considers cable. We could make our own curve for real speakers and include cable since Soundstage showed output impedance vs freq.

Cable is considered:

"The output impedance, including a 6' speaker cable, was a low 0.09 ohm at 20Hz and 1kHz, rising slightly to 0.22 ohm at 20kHz. As a result, the modification of the Benchmark amplifier's frequency response due to the interaction between this impedance and that of our standard simulated loudspeaker was just ±0.1dB (fig.1, gray trace). "

"and as the two channels' output stages are in series in this mode, the output impedance, again including the 6' of speaker cable, was higher than in stereo, at 0.14 ohm at 1kHz. "

 

[pjug]

Cable is considered:

"The output impedance, including a 6' speaker cable, was a low 0.09 ohm at 20Hz and 1kHz, rising slightly to 0.22 ohm at 20kHz. As a result, the modification of the Benchmark amplifier's frequency response due to the interaction between this impedance and that of our standard simulated loudspeaker was just ±0.1dB (fig.1, gray trace). "

"and as the two channels' output stages are in series in this mode, the output impedance, again including the 6' of speaker cable, was higher than in stereo, at 0.14 ohm at 1kHz. "

Ah, didn't realize. Then my assumption that the flat vs filtered difference would be the same as Stereo vs mono difference is not quite right?

Maybe better to make another EQ file using the Soundstage measured AHB2 output impedance, and the impedance curve of the Revel speakers used in the OP recording?

 

[Pdxwayne]

Ah, didn't realize. Then my assumption that the flat vs filtered difference would be the same as Stereo vs mono difference is not quite right?

Maybe better to make another EQ file using the Soundstage measured AHB2 output impedance, and the impedance curve of the Revel speakers used in the OP recording?

Please do. I would like to try it out. : )

 

[pjug]

Please do. I would like to try it out. : )

OK, I will try to do it tonight. My plan is to use VituixCAD trace to get the data from the Soundstage ABH2 output impedance curve and Amir's impedance curve for the F208. Then do the calculations in a spreadsheet, make the EQ file taking a few numbers from that. In case you or anyone else want to do it before I can get to it.

 

[Pdxwayne]

OK, I will try to do it tonight. My plan is to use VituixCAD trace to get the data from the Soundstage ABH2 output impedance curve and Amir's impedance curve for the F208. Then do the calculations in a spreadsheet, make the EQ file taking a few numbers from that. In case you or anyone else want to do it before I can get to it.

I will let you handle it. : )

Would like to see how it is different than your first version.

Thanks!

 

[pjug]

Here is what I am getting. I included 10 feet of 12 AWG cable (20 ft round trip). Since the AHB2 has a high damping factor at low frequencies, the cable resistance is the main cause of the deviations of FR (the bigger difference is at high frequencies, where the AHB2 DF comes down and the F208 impedance is also lower than with the simulated speaker). So not much difference between mono and stereo except at higher frequencies. The delta is what should be applied as EQ for an ABX test (correct?), but I can't imagine there is any audible difference in the bass, which is the OP claim. I think any bass difference would have to be from something else besides output impedance effects. I am not sure doing ABX with a filter made from this FR delta is worthwhile to do. Recording speaker voltage would be better.

edit: remade the chart to see effects better

 

[Pdxwayne]

Here is what I am getting. I included 10 feet of 12 AWG cable (20 ft round trip). Since the AHB2 has a high damping factor at low frequencies, the cable resistance is the main cause of the deviations of FR (the bigger difference is at high frequencies, where the AHB2 DF comes down and the F208 impedance is also lower than with the simulated speaker). So not much difference between mono and stereo except at higher frequencies. The delta is what should be applied as EQ for an ABX test (correct?), but I can't imagine there is any audible difference in the bass, which is the OP claim. I think any bass difference would have to be from something else besides output impedance effects. I am not sure doing ABX with a filter made from this FR delta is worthwhile to do. Recording speaker voltage would be better.
View attachment 136362

Good job providing the differences!

Stereo is brighter. To match the brightness of stereo with mono, let's say at 10khz, the mono overall volume from 1khz and down would be 0.5db higher as compared to stereo. Would that give a sense of stronger bass?

 

[pjug]

Good job providing the differences!

Stereo is brighter. To match the brightness of stereo with mono, let's say at 10khz, the mono overall volume from 1khz and down would be 0.5db higher as compared to stereo. Would that give a sense of stronger bass?

I am doubtful, because the delta is still just 1 dB at 17KHz. But it is possible you are right. I will make an EQ filter from the delta in a little bit.

 

[Pdxwayne]

I am doubtful, because the delta is still just 1 dB at 17KHz. But it is possible you are right. I will make an EQ filter from the delta in a little bit.

According to benchmark article at
https://benchmarkmedia.com/blogs/ap...KwHM2ZqkqRlb7LVNrQNXnHOC2-OKx3nRoCMagQAvD_BwE....

0.2db is at the threshold of audibility. 0.5db gives "red" color in the example Excel worksheet.

So, "just 1db" supposed to be so obvious that no abx is needed, at least for those who can still hear 20khz.... : P