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Testing audiophile claims and myths - Page 158

post #2356 of 3206
Quote:
Originally Posted by analogsurviver View Post

I expect quite a hoolaballo after the above statement, with numerous "proofs" by tons of distinguished members of the audio community, who claim absolute phase to be inaudible.

Yes, absolute polarity (not phase) should be inaudible. When a difference is heard, it can be traced to non-lineararity in the loudspeakers or headphones. The driver cone behaves differently pushing out versus pulling in.

It sounds like you play the trumpet? Can you record yourself playing whatever you believe illustrates a difference in polarity, and post the file? I'd like to hear an example of a file that sounds different forward versus backwards, and analyze it to see what's going on.

--Ethan
post #2357 of 3206
Quote:
Originally Posted by EthanWiner View Post


Yes, absolute polarity (not phase) should be inaudible. When a difference is heard, it can be traced to non-lineararity in the loudspeakers or headphones. The driver cone behaves differently pushing out versus pulling in.

It sounds like you play the trumpet? Can you record yourself playing whatever you believe illustrates a difference in polarity, and post the file? I'd like to hear an example of a file that sounds different forward versus backwards, and analyze it to see what's going on.

--Ethan

Well, all I can play is - audio gear :atsmile: - be it reproduction or recording side of it.

 

I merely chose the trumpet as the most commonly known brass instrument. Given that I am a recording engineer, I will ask a/some member(s) of the brass section of the symphony orchestra scheduled for the recording in next 10 or so days to play for this experiment the same tune from much closer than I usually record, from the regular position for recording the orchestra and as far away from the back of the hall as possible. The resulting files should be illustrative enough.

 

Unfortunately, I can not record in the correct AND out of phase absolute polarity ( both channels 180 degrees out of phase ) - for reasons I do not wish to disclose. My mics etc  are wired so to produce positive going voltage when input is positive pressure. You can play the files back with any of the possibilities to invert the absolute phase; in digital domain, trough an additional analog inverting stage, by simply changing the speaker wires with BOTH speakers - simply choose the one you are most comfortable with, preferably the one that can be A/B'd by the flick of a switch.

 

Original files will be DSD128. If you do not have native DSD playback, I can convert them for you into desired PCM - with reduced sonics. But any decent PCM should still be perfectly usable for this test.

post #2358 of 3206
Quote:
Originally Posted by stv014 View Post
 

 

More dynamic and overall "bigger" sound with punchier drums is what slightly higher volume subjectively sounds like. :normal_smile : It also affects the perceived frequency response, because at higher volume, bass and (to a lesser extent) treble become relatively more audible.

 

+1

 

 

Quote:
Originally Posted by analogsurviver View Post
 

Well, all I can play is - audio gear :atsmile: - be it reproduction or recording side of it.

 

I merely chose the trumpet as the most commonly known brass instrument. Given that I am a recording engineer, I will ask a/some member(s) of the brass section of the symphony orchestra scheduled for the recording in next 10 or so days to play for this experiment the same tune from much closer than I usually record, from the regular position for recording the orchestra and as far away from the back of the hall as possible. The resulting files should be illustrative enough.

 

Unfortunately, I can not record in the correct AND out of phase absolute polarity ( both channels 180 degrees out of phase ) - for reasons I do not wish to disclose. My mics etc  are wired so to produce positive going voltage when input is positive pressure. You can play the files back with any of the possibilities to invert the absolute phase; in digital domain, trough an additional analog inverting stage, by simply changing the speaker wires with BOTH speakers - simply choose the one you are most comfortable with, preferably the one that can be A/B'd by the flick of a switch.

 

Original files will be DSD128. If you do not have native DSD playback, I can convert them for you into desired PCM - with reduced sonics. But any decent PCM should still be perfectly usable for this test.

 

secrets, secrets, secrets.....  oh well.

post #2359 of 3206
Quote:
Originally Posted by upstateguy View Post
 

 

+1

 

 

 

secrets, secrets, secrets.....  oh well.

Nothing to do with the absolute polarity - merely stating why there will not be recordings in correct and 180 degree opposie polarity. The test or its validity will be in no way influenced by what I prefer to keep under wraps.

post #2360 of 3206
Quote:
Originally Posted by analogsurviver View Post

You can play the files back with any of the possibilities to invert the absolute phase

Yes, of course, I don't need two versions. What would be the point anyway? You can't have two microphones in the same physical space, so that alone would account for a change in sound quality (mainly frequency response).
Quote:
If you do not have native DSD playback, I can convert them for you into desired PCM - with reduced sonics. But any decent PCM should still be perfectly usable for this test.

I do not have a way to play DSD files, so you'd have to convert them. But why do you think DSD is superior to PCM? PCM gives a perfect replica of what it recorded, within the limits of its own accuracy. PCM is also easier / less expensive to edit, so I never considered DSD. These days even mid-level converters are audibly transparent, so I don't see how anything could be "better" than transparent. But that's another issue. I'll be glad to play around with your trumpet files. Though all I really need is one file that you believe sounds different when the polarity is reversed.

--Ethan
post #2361 of 3206

I'm puttin a five spot down on no difference, anyone want to spot me on that?

post #2362 of 3206

I thought is was well established that asymmetric waveforms with tons of even harmonics can be audibly distinguished by polarity of playback - our ears only produce nerve discharge pulses on positive pressure excursions - does get wiped out above a few kHz but is quite well known, can be seen in probes of animal auditory neurons

 

for visualizing polarity/asymmetric waveforms consider sawtooth waveforms - no DC component necessary - you can see if the fast edge goes up or down

 

but most agree that speaker distortion can interfere with demonstrating the effect, and at best it doesn't appear to very audibly significant


Edited by jcx - 3/1/14 at 9:24pm
post #2363 of 3206
Quote:
Originally Posted by EthanWiner View Post


Yes, of course, I don't need two versions. What would be the point anyway? You can't have two microphones in the same physical space, so that alone would account for a change in sound quality (mainly frequency response).
I do not have a way to play DSD files, so you'd have to convert them. But why do you think DSD is superior to PCM? PCM gives a perfect replica of what it recorded, within the limits of its own accuracy. PCM is also easier / less expensive to edit, so I never considered DSD. These days even mid-level converters are audibly transparent, so I don't see how anything could be "better" than transparent. But that's another issue. I'll be glad to play around with your trumpet files. Though all I really need is one file that you believe sounds different when the polarity is reversed.

--Ethan

What I meant were two recordings from the same microphone in the same position - one in correct, another in inverted absolute polarity. That is why some equipment with XLRs allows for pin "inversion" - I do not have this capability. 

 

DSD is superior to PCM in time domain/pulse response - whichever you prefer. PCM is just plain too slow - DXD included ( I have no DXD recording capability at the present ) . Time permitting, I will use signal generator and record precisely defined pulse(s) using various resolutions of DSD and PCM - with real machine(s) - not rosy picture versions from proponents from either of the camps - and post the photos of the actual output on the oscilloscope; if the digital storage of my oscilloscope will prove to be too slow/low resolution, I will try to catch the photo from the analog display.

 

I agree PCM is easier / less expensive to edit ; however, I am delighted at the request of the pending recording, where performers explicitely demanded NO EDITING - we will make XY? number of takes - and release the take the performers will be most comfortable with. Sort of modern day equivalent of Direct to Disk recording, with the benefit of the possibility to record music in any reasonable lenght of time, without having to play the programme for the duration of entire side of a LP in one go, if you prefer to call it that way. Thus, the full fidelity of DSD128, without conversion to PCM for editing, will be available to the final consumer for the very first time.

Initially, CD will be released, with planned later availability as DSD128 download. As u$ual, $ problem$ ...

 

I did Direct to CD-R http://www.folketc.si/04Glasba.html recording with no editing whatsoever ( save for compression performers finally opted for because of the radio / infamous loudness wars ) in the past this way - we merely selected the best take of each song.

post #2364 of 3206
Quote:
Originally Posted by jcx View Post
 

I thought is was well established that asymmetric waveforms with tons of even harmonics can be audibly distinguished by polarity of playback - our ears only produce nerve discharge pulses on positive pressure excursions - does get wiped out above a few kHz but is quite well known, can be seen in probes of animal auditory neurons

 

for visualizing polarity/asymmetric waveforms consider sawtooth waveforms - no DC component necessary - you can see if the fast edge goes up or down

 

but most agree that speaker distortion can interfere with demonstrating the effect, and at best it doesn't appear to very audibly significant

I would appreciate if you can point to some referene(s) regarding our hearing mechanism and absolute polarity - I can hear it, but it would be nice to see confirmation in print.

 

I agree sawtooth can be used - and it is audible one way or another;  but as it is next to nonexistant in real world, I prefer to use real instruments.

 

Speaker AND headphones/IEMs DO interfere with demonstrating the effect. That is why I prefer using full range headphones or speakers, as any crossovers that are higher than the first order 6 db/octave (insufficient in most real case scenarios ) introduce phase or polarity troubles. The best are electrostatics ( either headphones or speakers ) driven by high voltage DC coupled amplifiers - followed by SINGLE full range dynamic drivers, be it headphones or speakers. I eschew multi driver approch whenever possible - I would NEVER use multi driver IEM like Shure SE 530; In pulse response, it can be clearly seen that  initially, its treble goes to negative and after a while the rest picks up into the correct polarity : http://www.innerfidelity.com/images/ShureSE530.pdf  Please note SE530 is a VERY benign example of this polarity problem - some speakers do go from positive to negative etc 5 times in 20 Hz to 20 kHz bandwidth. Needless to say, these are utterly useless for demonstrating the effects of the correct and/or inverted absolute polarity - as well as for music reproduction; despite their frequency response being almost ruler flat ...

 

Please note that quite some (most?) Stax models as delivered from the factory produce inverted absolute polarity

 

http://www.innerfidelity.com/images/StaxSR009.pdf

http://www.innerfidelity.com/images/StaxSR003SA1993.pdf

 

I will present how I practically deal with absolute polarity issues in real life at some later stage.


Edited by analogsurviver - 3/1/14 at 11:49pm
post #2365 of 3206

So I finally got around to the doing the first round of testing today, specifically: the Quad 99 monoblocks vs Onkyo receiver. I might do another couple of rounds when I get some more free time, to compare Onkyo vs Inter-M and Inter-M vs Quad, but seeing the results I got today, I'm not sure it's worth bothering about.

 

My multimeter's battery decided it had enough, so I had to use a dB meter to match volumes from each amp. I won't make a very long post about it, as only the result interest me and I don't like to get into page-long reviews of gear.

 

Material used:

 

Sine wave @ 60Hz (120s long) for dB matching the speakers.

An el-cheapo dB meter, that still did the trick to match levels within 1dB.

Lossless CD rips with foobar and WASAPI, digital out by optical from Emu 1212m soundcard.

TOSLink glass optical cable (1m) to Benchmark DAC-1.

DAC-1 balanced XLR out to Singlepower MPX3 tube preamp/headphone amp. (With a pair of Cardas XLR to RCA converters plugged into the DAC, and Cardas 300b micro RCA interconnects between DAC and preamp).

Singlepower MPX3 has 2 pairs of RCA outputs:

1) No name RCA interconnects to Quad 99 monoblocks

2) No name RCA interconnects to Onkyo receiver

Tubes used: Sophia Electric 6SN7 matched pair as output tubes, Ken-Rad black top 6SN7GT as the driver tube.

No name el-cheapo speaker cables were used for both (for comparison's sake, not that I believe different cables would change anything)

Dynaudio Audience 62 floorstanding speakers

 

 

Music used (I only bothered with what are to my ears good enough recordings to highlight the differences, unless specified otherwise):

 

Prodigy - Mindfields

Massive Attack - Teardrop

Bill Withers - Just The Two Of Us

Chic - Good Times

Curtis Mayfield - Pusherman

Marvin Gaye - Inner City Blues

Otis Redding - Dock Of The Bay

Ray Charles - Georgia On My Mind (poor recording)

Stevie Wonder - Uptight

Busta Rhymes - It Ain't Safe No More

DJ Shadow - Fixed Income

M.O.P - Ante Up

Nujabes - Lady Brown

The Roots - The Next Movement

Art Blakey w/ Thelonious Monk - Blue Monk

Art Pepper - Jazz Me Blues

Bill Evans - Danny Boy

Chick Corea - I Don't Know

Dinah Washington - Salty Papa Blues (poor recording)

Duke Ellington - Love You Madly

Erroll Garner - Someone To Watch Over Me (poor recording)

Hiromi Uehara - Place To Be

John Coltrane - Giant Steps

Keith Jarrett - Koln Concert part C

Marcus Miller - Power

Miles Davis - So What

Nina Simone - I Put A Spell On You

Phineas Newborn Jr - Harlem Blues

Sidney Bechet - Original Dixieland One-step (poor recording)

Toots Thielemans - Oh Suzannah

Weather Report - Birdland

Weather Report - Teen Town

Deftones - Digital Bath

Iron Maiden - Running Free

Metallica - Hit The Lights

Nirvana - Where Did Your Sleep Last Night (unplugged)

Smashing Pumpkins - Rocket

Soundgarden - Rusty Cage

Gladiators - Hearsay (poor recording)

Black Sabbath - Lord Of This World (poor recording)

Bob Dylan - Highway 51

Buffalo Springfield - For What It's Worth

Captain Beefheart - Zig Zag Wanderer (poor recording)

Creedence Clearwater Revival - Ramble Tamble

Dire Straits - Sultans Of Swing

Dire Straits - Money For Nothing

Howlin Wolf - I'm The Wolf (poor recording)

Iron Butterfly - In A Gadda Da Vida

Jimi Hendrix - One Rainy Wish (poor recording)

Johnny Cash - Walk The Line

Lightnin Hopkins - My Babe (poor recording)

Pink Floyd - Time

Pink Floyd - Wish You Were Here

Queen - We Will Rock You

Supertramp - Bloody Well Right

Taj Mahal - Statesboro Blues (poor recording)

The Doors - Love Me Two Times

The Police - Reggatta De Blanc

The Who - My Generation (poor recording)

Van Halen - Hang Em High

 

All recordings are FLAC lossless CD rips. No SACD or otherwise were used, to keep things fair (although since some of these are really bad recordings, things weren't exactly fair).

 

I realize the list is much too extensive for what I was testing, but I wanted to try alot of the music I listen to frequently to make sure things didn't vary too much from recording to recording. Keep in mind I didn't necessarily listen to the song in its entirety, more often than not the switching was done by a third party in the middle of a song.

 

Set up:

 

I don't feel comfortable posting pictures of my living room (thus showing how the speakers are placed, etc) but I figure it doesn't matter much considering they don't move from the spot they're in anyway. I sat about 7 meters away, in the middle with the speakers slightly tilted towards the middle point (me). I was blindfolded, and a third party switched between the preamp outputs at will. This was PARTIALLY flawed as the switch can slightly CLICK if you're not careful to switch slowly, but after a few tries she could switch between the outputs without me hearing the click.

 

We agreed on 2 switches per song maximum (sometimes 1, sometimes none, without my knowledge), without me knowing which output was used when the song started. I would simply speak up whenever I felt I heard a noticeable change, there was no warning when switches happened and it was never up to me.

 

Results:

 

I'll keep these short, as I didn't bother taking notes for every single song used. I'll just describe what I heard on the most obvious ones (the better recordings/the more dynamic ones):

 

Out of all the songs listed above, there were only 3 where I couldn't tell any obvious difference: Lightnin Hopkins - My babe, Sidney Bechet - Original Dixieland One-step, and Dinah Washington - Salty Papa Blues. Honestly, I blame the quite awful quality of the recordings.

 

For every other song on there, the difference was audible, for the particularly dynamic/good recordings (the Dire Straits, Supertramp, The Police, Weather Report, Coltrane/Davis, and a few other songs in particular), the difference was quite important, so I'll stick to describing what differences I heard primarily for these.

 

I'm not very well versed in audiophile vocabulary to describe sound signatures, so bear with me:

 

There were all in all two aspects which really weren't subtle differences: soundstage and dynamics.

 

Soundstage was alot wider using the Quad monoblocks, and I don't mean slightly either. The music really opened up with the Quads compared to the Onkyo where instrument separation was less distinct, soundstage had less space/air. Dynamics on the Quad were much more in your face and clear. I could tell the difference within the first second the drums joined in, which pretty much was the biggest difference between the two. I will spare you the two-page paragraph describing every cymbal crash with vocabulary taken from culinary reviews and just say that this test pretty much confirmed what I heard before right down to the detail. I might or might not do a couple of other rounds as said above, depending on interest.

post #2366 of 3206
Quote:

Originally Posted by elmoe View Post

 

Sine wave @ 60Hz (120s long) for dB matching the speakers.

An el-cheapo dB meter, that still did the trick to match levels within 1dB.

 

It may sound like nit-picking, but 1 dB accuracy is not good enough. A level difference of 1 dB is definitely audible. Also, for acoustic level matching, sine waves can be problematic, because the measured level will vary with the location of the SPL meter, due to room acoustics; however, I do recommend the more accurate and reliable voltage measurement method (preferably testing the voltage under load) anyway. It would also be useful to find out the output voltage at your listening level. Additionally, it is best to make sure that individual channels (left and right) have accurately matched levels between the amplifiers.

 

By the way, would it be possible to skip that tube pre-amplifier ? It might not make any difference, but it is better to have fewer variables that could potentially affect the result in some way.

 

I see the Onkyo has tone controls and is a multi-channel amplifier. Make sure that it is set up to work as a transparent stereo amplifier, if possible at all (flat frequency response - which it may not even be capable of if the tone control is badly implemented, no surround sound processing, etc.).

post #2367 of 3206
Quote:
Originally Posted by stv014 View Post
 

 

It may sound like nit-picking, but 1 dB accuracy is not good enough. A level difference of 1 dB is definitely audible. Also, for acoustic level matching, sine waves can be problematic, because the measured level will vary with the location of the SPL meter, due to room acoustics; however, I do recommend the more accurate and reliable voltage measurement method (preferably testing the voltage under load) anyway. It would also be useful to find out the output voltage at your listening level. Additionally, it is best to make sure that individual channels (left and right) have accurately matched levels between the amplifiers.

 

By the way, would it be possible to skip that tube pre-amplifier ? It might not make any difference, but it is better to have fewer variables that could potentially affect the result in some way.

 

I see the Onkyo has tone controls and is a multi-channel amplifier. Make sure that it is set up to work as a transparent stereo amplifier, if possible at all (flat frequency response - which it may not even be capable of if the tone control is badly implemented, no surround sound processing, etc.).

 

Yes I should've been more accurate: the levels were matched to the exact dB (my dB meter doesn't show fractions of dB). That said, I don't think a 1dB difference would make that much of a difference in the soundstage, perhaps slightly for the dynamics, but again 1dB really isn't enough for the clear difference heard. I was told in this thread to use a sine wave, but if you want I'll use something else for the next round, please specify what you think would be better. I will also change the battery in my multimeter for next time, although I'm pretty sure the dB meter did just fine. I'll also take note of the voltage under load once I have an operational multimeter, and check the individual channel levels for everything as well.

 

Yes, I can hook the DAC straight to the power amps I'm pretty sure that will work just fine. 

 

The Onkyo is indeed multi channel (5.1) but I had it set as stereo with no tone control/EQ whatsoever. As to whether or not the tone control was properly implemented though, I'm afraid I have no idea.

 

edit: the problem with using the DAC only is that I cannot switch between outputs like with the tube preamp, just realized this. So for a DBT it won't be effective.


Edited by elmoe - 3/2/14 at 7:24am
post #2368 of 3206
Quote:
but again 1dB really isn't enough for the clear difference heard

1dB IS 'the clear difference heard' .

It doesn't matter that 'I don't think a 1dB difference would make that much of a difference in....'

That 1dB IS the difference in blablaba .

post #2369 of 3206
Quote:
Originally Posted by bufferoverflow View Post
 

1dB IS 'the clear difference heard' .

It doesn't matter that 'I don't think a 1dB difference would make that much of a difference in....'

That 1dB IS the difference in blablaba .

 

But the difference wasn't really 1dB, the dB meter read the same for each amps. It just doesn't show decimals.

 

And no, a 1dB difference will not show any significant difference in soundstage, that's just a ridiculous claim.

post #2370 of 3206

'soundstage' is a ridiculous' term .

 

And since your 'dB-meter' is only accurate to one dB there could easily be more than 0.2dB level-mismatch

between the 2 amps - And that IS audible, you just won't perceive it as 'louder' but better - 'soundstage' for example -

 

 

http://productionadvice.co.uk/level-matching/

 

I  am not the one claiming anything here, there is general agreement that levels must be matched to less than 0.2dB

or the louder kit will sound better (or be reliably recognized in a blind-test - But they are probably also 'ridicoulous' ??) .


Edited by bufferoverflow - 3/2/14 at 8:36am
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