I've had this one sitting in my DAW and been meaning to look at it for nearly 18 months, ever since it was mentioned somewhere that the rear channels might be swapped - the recent chatter about this title in a couple of threads motivated me to finally get this one done, and the results were kind of surprising, though given the fact it was mastered by Peter Mew maybe I shouldn't have been.
I'll be covering the following things here:
Before I start I just want to have a grumble that because this album is stuck on SACD that I had to (and you will have to) convert it to PCM in order to make these changes. because there are no consumer-grade options for working with channel volume levels of .dsf DSD files.
I converted the SACD to 88.2kHz/24bit WAVs with the 'PCM Volume' setting at +3dB - if you're going to replicate these tweaks I strongly recommend not going any higher than this, because one of the tracks needs a +2.5dB output boost and anything more than +3dB boost on the conversion will push this change into the red.
1. LFE Issues
The headline here is that (at least on my rip and PCM conversiont) hat the LFE is one of the most egregious examples of the delay issue I first identified in 2021 that I've encountered so far, approximately 17.5ms out of sync with the full range channels.
The severity of the problem seems to be partially due to the fact that there's a chunk (about 6ms) of the Front Left channel duplicated in the LFE channel before the actual LFE content starts, as you can see in this screenshot:
Suffice it to say that fixing this unlocks a considerable amount of bass, especially if your front channels have bass management at all.
2. Channel Balance Issues
Loading this album into my DAW I was immediately struck by the fact that in the waveforms, the Rear Left (Ls) channel was consistently lower in volume than the other three channels, as you can see in this screenshot:
(LFE channel deleted just for visual clarity)
Now, I know from my earlier forays into this stuff (like the diagonal pans on the O'Jays Ship Ahoy quad SACD for example) the folly of making arbitrary changes to things when you don't know what the engineer's original intention was, but with this album, there seemed to be a simple answer to balancing the rear (and front) pairs. Despite being an SQ LP release originally, it breaks one of the format's cardinal rules: it has elements mixed to the center rear position:
The front channel balances were all really close to perfect (I tweaked a couple of them by 1dB) with major outlier: Track 6, Lazy. For some reason, the Front Left channel was a full 5dB louder than the Front Right, heavily skewing all the phantom center placements (lead vox, organ solo, etc.) to the left.
(Lazy waveforms)
I pondered this while looking at the waveforms for a good long while - how could this one track alone be so off from all the others? Then it struck me: they balanced the Front channels based on the organ improv at the beginning, rather than the actual full-band song itself. The reason this led to the 5dB skew to the left is that for the organ improv, the Front left channel should be quieter than the Front Right, and the evidence is right there in the rears: the Rear Left (Ls), which would be the "twin" of the Front Left, is considerably quieter than the Rear Right (Rs), (which would be the "twin" of the Front Right) in the intro.
You can see the imbalance of the fronts in this Voxengo SPAN screenshot:
(Light green is the Front Right channel, darker green is the Front Left channel)
This is during the organ solo - you'd expect some part of the frequency spectrum to overlap, but as you can see the front right channel is just uniformly quieter.
This is with the front left channel reduced by 5db:
Almost perfectly balanced.
Strangely enough, Lazy was the only track where the rears didn't need any tweaking, something I re-checked about 5 times in different places because all the other tracks needed the Rear Left boosted by 2-3dB
So having said all that, these are my adjustments for the whole album:
(LFE -17.5ms)
3. Channel Assignments
As I said off the top, the reason I first dug into this album was someone mentioned that the rear channels were swapped compared to the original SQ LP release. Short of having a photo of the master tape box, the only way to figure out if the channels are swapped is by ear (and by using my medium-sized intellect) and looking for things that either occur simultaneously in the front and rear speakers, or that move (pan) from one speaker to another.
I listened to the whole album on headphones, soloing various channels as I went, and the only usable occurrence of any of this on the whole album is, once again, the keyboard intro to Lazy.
It appears that they used 4 mics to capture this: one on the treble rotor of the Leslie speaker, one on the bass rotor, and a stereo pair some distance away to capture reverb or 'room sound'.
When the track starts, the treble rotor is in the front right, the bass rotor is in the front left, and the stereo room mics are in the two rear speakers. During the first bit of organ noodling, the two front mics slowly switch positions, crossing each other in the soundfield, until you now have bass rotor in the front left, treble rotor (with increasing distortion) in the front right, and the room mics behind you.
The next movement sees the two front channels slowly move to the rear to join the 'room sound' mics: the front left (bass rotor) moves to the rear left and the front right (treble rotor) moves to the rear right. This tells me that the channel assignments are correct, because if you swapped the rears, the treble rotor (the more audible of the two) would move from the Front Right to the Rear Left, which is impossible to do using a joystick panner because if you were doing that, at the point you were halfway between front right and rear left you'd also be halfway between front left and rear right, ie quad center, so you'd be hearing the sound coming out of all 4 speakers, not just the Front Right and Rear Left.
Now that isn't to say that the original SQ LP didn't have the rears the other way around, or maybe that it had both the fronts and rears the other way around (I don't know, I've never heard it) but it's my opinion, having checked my fair share of quad channel assignments, that the left/right relationships between the front and rear channels on this SACD are fine, as-is.
Simply put, as well, because (outside of that organ intro) there are no around the room swirls, diagonal pans or any other front/rear relationships in this mix, if you want to swap the rears because it makes the album sound better to you, you can with very little detrimental effect.
4. Observations on Differences in Track Duration and Instrumentation
First off, the Discogs entry for the SACD has the wrong runtimes for the multichannel (quad) layer - they've just been copied from the stereo layer. These are the actual quad runtimes:
I'll get Highway Star out of the way first because it's just minor: starting around 19 seconds in, there are several extra bars of the intro groove (totaling about three seconds) before the distorted keyboard and then cascading screams come in. Presumably the stereo version had this edited out after it was mixed down and the quad mixers just didn't notice.
I think it's pretty well known that some of the final guitar solo on Lazy was edited out ont he quad mix, but the specifics are a little more interesting than that:
Starting at 5:59 there are a few seconds of lead guitar fills present in the quad mix that aren't in the stereo mix. Then at 6:06 (for about 14 seconds, through 6:20) there's an entirely different guitar solo than the one in the stereo mix, lower in register and not quite as aggressive. Maybe this was the one cut live with the band and then later discarded in favour of the overdubbed one that appears in the stereo mix?
Finally, the section from 6:19.5 through 6:32 (12.5 seconds) in the stereo mix is completely missing, edited out of the quad mix. The two mixes join back up during a big drum roll behind the end of the solo. I was kind of surprised to discover that only twelve-and-a-half seconds of solo were excised - in my mind for some reason it was 30 or 40. I think the combination of getting to hear an alternate solo, and only losing that small amount of music makes the UK quad mix not nearly as much of a problem as it may have seemed, at least in my mind anyway.
Here's a screenshot of the quad mix lined up with the stereo mix and split to show where the missing solo section is, which I think also illustrates how small an amount of music it is:
Some might ask "why remove 13 seconds of a track at all?" The answer lies in the fact that when these mixes were done, EMI UK hadn't decided to release matrix quad LPs at all, so like the early RCA quad mixes of 1970, they were done entirely with Q8 release in mind. This meant often swapping tracks between the two sides (or programs) of the Q8, and in cases like Machine Head, editing out entire sections of music to try and get the running time of the two programs roughly equal. Other EMI Q8 releases also suffered from this - possibly the most egregious was Dark Side of the Moon, which had Money fade out halfway through the song at the end of Program 1 and fade back in to finish at the beginning of Program 2.
The (frankly, bonkers) tracklist for the UK Q8 of Machine Head shows you just how far they went in service of balancing the runtime of the sides, on top of editing Lazy:
Program 1
6:15 Highway Star
5:44 Smoke on the Water
7:11 Lazy (Original quad running time as per German LP: 6:40)
----
19:10 (or 18:40 with 6:40 Lazy)
Program 2
4:39 Space Truckin'
5:07 Pictures of Home
4:57 Maybe I'm a Leo
4:01 Never Before
----
18:44
If you made it this far I hope you enjoyed this deep dive into the quad mix. Despite its issues I love it - it has a lot of the flavour of the original stereo mix, but is still more than aggressive enough to please the discerning quad enthusiast. I think it's superior to the US quad mix, which sounds like it was mixed in Hollywood in 1974 (because it was) and the not-daring-enough 5.1 mix from the DVD-A.
I'll be covering the following things here:
- LFE issues
- Channel balance issues
- Channel assignments
- Observations on differences in track duration and instrumentation (just Lazy and Highway Star)
Before I start I just want to have a grumble that because this album is stuck on SACD that I had to (and you will have to) convert it to PCM in order to make these changes. because there are no consumer-grade options for working with channel volume levels of .dsf DSD files.
I converted the SACD to 88.2kHz/24bit WAVs with the 'PCM Volume' setting at +3dB - if you're going to replicate these tweaks I strongly recommend not going any higher than this, because one of the tracks needs a +2.5dB output boost and anything more than +3dB boost on the conversion will push this change into the red.
1. LFE Issues
The headline here is that (at least on my rip and PCM conversiont) hat the LFE is one of the most egregious examples of the delay issue I first identified in 2021 that I've encountered so far, approximately 17.5ms out of sync with the full range channels.
The severity of the problem seems to be partially due to the fact that there's a chunk (about 6ms) of the Front Left channel duplicated in the LFE channel before the actual LFE content starts, as you can see in this screenshot:
Suffice it to say that fixing this unlocks a considerable amount of bass, especially if your front channels have bass management at all.
2. Channel Balance Issues
Loading this album into my DAW I was immediately struck by the fact that in the waveforms, the Rear Left (Ls) channel was consistently lower in volume than the other three channels, as you can see in this screenshot:
(LFE channel deleted just for visual clarity)
Now, I know from my earlier forays into this stuff (like the diagonal pans on the O'Jays Ship Ahoy quad SACD for example) the folly of making arbitrary changes to things when you don't know what the engineer's original intention was, but with this album, there seemed to be a simple answer to balancing the rear (and front) pairs. Despite being an SQ LP release originally, it breaks one of the format's cardinal rules: it has elements mixed to the center rear position:
- Highway Star - lead vocals
- Maybe I'm a Leo - electric piano solo (2:24)
- Pictures of Home - bass solo (3:41)
- Never Before - organ solo (3:32)
- Smoke on the Water guitar solo (2:58)
- Lazy - lead vocals (this track was correct and didn't need adjusting in the rears)
- Space Truckin' - percussion solo (2:52)
The front channel balances were all really close to perfect (I tweaked a couple of them by 1dB) with major outlier: Track 6, Lazy. For some reason, the Front Left channel was a full 5dB louder than the Front Right, heavily skewing all the phantom center placements (lead vox, organ solo, etc.) to the left.
(Lazy waveforms)
I pondered this while looking at the waveforms for a good long while - how could this one track alone be so off from all the others? Then it struck me: they balanced the Front channels based on the organ improv at the beginning, rather than the actual full-band song itself. The reason this led to the 5dB skew to the left is that for the organ improv, the Front left channel should be quieter than the Front Right, and the evidence is right there in the rears: the Rear Left (Ls), which would be the "twin" of the Front Left, is considerably quieter than the Rear Right (Rs), (which would be the "twin" of the Front Right) in the intro.
You can see the imbalance of the fronts in this Voxengo SPAN screenshot:
(Light green is the Front Right channel, darker green is the Front Left channel)
This is during the organ solo - you'd expect some part of the frequency spectrum to overlap, but as you can see the front right channel is just uniformly quieter.
This is with the front left channel reduced by 5db:
Almost perfectly balanced.
Strangely enough, Lazy was the only track where the rears didn't need any tweaking, something I re-checked about 5 times in different places because all the other tracks needed the Rear Left boosted by 2-3dB
So having said all that, these are my adjustments for the whole album:
(LFE -17.5ms)
- Ls +2dB
- Ls +2dB
- FR +1dB, Ls +2dB
- FR +0.5dB, Ls +2dB
- Ls +2.5dB
- FL -5dB, Master bus +2.5dB (you need to boost the overall volume of this track because of the reduction in volume to the front channel to get the same vocal level as the other tracks)
- FR +1dB, Ls +3dB
3. Channel Assignments
As I said off the top, the reason I first dug into this album was someone mentioned that the rear channels were swapped compared to the original SQ LP release. Short of having a photo of the master tape box, the only way to figure out if the channels are swapped is by ear (and by using my medium-sized intellect) and looking for things that either occur simultaneously in the front and rear speakers, or that move (pan) from one speaker to another.
I listened to the whole album on headphones, soloing various channels as I went, and the only usable occurrence of any of this on the whole album is, once again, the keyboard intro to Lazy.
It appears that they used 4 mics to capture this: one on the treble rotor of the Leslie speaker, one on the bass rotor, and a stereo pair some distance away to capture reverb or 'room sound'.
When the track starts, the treble rotor is in the front right, the bass rotor is in the front left, and the stereo room mics are in the two rear speakers. During the first bit of organ noodling, the two front mics slowly switch positions, crossing each other in the soundfield, until you now have bass rotor in the front left, treble rotor (with increasing distortion) in the front right, and the room mics behind you.
The next movement sees the two front channels slowly move to the rear to join the 'room sound' mics: the front left (bass rotor) moves to the rear left and the front right (treble rotor) moves to the rear right. This tells me that the channel assignments are correct, because if you swapped the rears, the treble rotor (the more audible of the two) would move from the Front Right to the Rear Left, which is impossible to do using a joystick panner because if you were doing that, at the point you were halfway between front right and rear left you'd also be halfway between front left and rear right, ie quad center, so you'd be hearing the sound coming out of all 4 speakers, not just the Front Right and Rear Left.
Now that isn't to say that the original SQ LP didn't have the rears the other way around, or maybe that it had both the fronts and rears the other way around (I don't know, I've never heard it) but it's my opinion, having checked my fair share of quad channel assignments, that the left/right relationships between the front and rear channels on this SACD are fine, as-is.
Simply put, as well, because (outside of that organ intro) there are no around the room swirls, diagonal pans or any other front/rear relationships in this mix, if you want to swap the rears because it makes the album sound better to you, you can with very little detrimental effect.
4. Observations on Differences in Track Duration and Instrumentation
First off, the Discogs entry for the SACD has the wrong runtimes for the multichannel (quad) layer - they've just been copied from the stereo layer. These are the actual quad runtimes:
- 6:15 Highway Star
- 4:57 Maybe I'm a Leo
- 5:07 Pictures of Home
- 4:01 Never Before
- 5:44 Smoke on the Water
- 7:11 Lazy
- 4:39 Space Truckin'
I'll get Highway Star out of the way first because it's just minor: starting around 19 seconds in, there are several extra bars of the intro groove (totaling about three seconds) before the distorted keyboard and then cascading screams come in. Presumably the stereo version had this edited out after it was mixed down and the quad mixers just didn't notice.
I think it's pretty well known that some of the final guitar solo on Lazy was edited out ont he quad mix, but the specifics are a little more interesting than that:
Starting at 5:59 there are a few seconds of lead guitar fills present in the quad mix that aren't in the stereo mix. Then at 6:06 (for about 14 seconds, through 6:20) there's an entirely different guitar solo than the one in the stereo mix, lower in register and not quite as aggressive. Maybe this was the one cut live with the band and then later discarded in favour of the overdubbed one that appears in the stereo mix?
Finally, the section from 6:19.5 through 6:32 (12.5 seconds) in the stereo mix is completely missing, edited out of the quad mix. The two mixes join back up during a big drum roll behind the end of the solo. I was kind of surprised to discover that only twelve-and-a-half seconds of solo were excised - in my mind for some reason it was 30 or 40. I think the combination of getting to hear an alternate solo, and only losing that small amount of music makes the UK quad mix not nearly as much of a problem as it may have seemed, at least in my mind anyway.
Here's a screenshot of the quad mix lined up with the stereo mix and split to show where the missing solo section is, which I think also illustrates how small an amount of music it is:
Some might ask "why remove 13 seconds of a track at all?" The answer lies in the fact that when these mixes were done, EMI UK hadn't decided to release matrix quad LPs at all, so like the early RCA quad mixes of 1970, they were done entirely with Q8 release in mind. This meant often swapping tracks between the two sides (or programs) of the Q8, and in cases like Machine Head, editing out entire sections of music to try and get the running time of the two programs roughly equal. Other EMI Q8 releases also suffered from this - possibly the most egregious was Dark Side of the Moon, which had Money fade out halfway through the song at the end of Program 1 and fade back in to finish at the beginning of Program 2.
The (frankly, bonkers) tracklist for the UK Q8 of Machine Head shows you just how far they went in service of balancing the runtime of the sides, on top of editing Lazy:
Program 1
6:15 Highway Star
5:44 Smoke on the Water
7:11 Lazy (Original quad running time as per German LP: 6:40)
----
19:10 (or 18:40 with 6:40 Lazy)
Program 2
4:39 Space Truckin'
5:07 Pictures of Home
4:57 Maybe I'm a Leo
4:01 Never Before
----
18:44
If you made it this far I hope you enjoyed this deep dive into the quad mix. Despite its issues I love it - it has a lot of the flavour of the original stereo mix, but is still more than aggressive enough to please the discerning quad enthusiast. I think it's superior to the US quad mix, which sounds like it was mixed in Hollywood in 1974 (because it was) and the not-daring-enough 5.1 mix from the DVD-A.
