Sound Devices MixPre-6 II (second generation)

You can delay audio on selected inputs/tracks on the PixE LR recorder, perhaps the MixPre 10 has this capability
Cheers

Yes, it has “delay” per channel, but what does that mean? The AVX is already late to the table with its audio delivered to the camera or recorder 19msec behind the video. For the AVX ‘clap’ to match the video of the clapper closing, you need to have its Timecode recorded with a value 19msec earlier. That’s simple I suppose for tracks if everything is from AVX mics.

Once you add wired mics where the audio ‘clap’ already matches the video of the clapper closing, you need to delay recording that audio for 19msec to match the AVX in a mix track.

Maybe a mix isn’t allowed if one or more tracks have different delays. I’m just not aware what is physically happening in the MixPre.


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Yes, it has “delay” per channel, but what does that mean? The AVX is already late to the table with its audio delivered to the camera or recorder 19msec behind the video. For the AVX ‘clap’ to match the video of the clapper closing, you need to have its Timecode recorded with a value 19msec earlier. That’s simple I suppose for tracks if everything is from AVX mics.

Once you add wired mics where the audio ‘clap’ already matches the video of the clapper closing, you need to delay recording that audio for 19msec to match the AVX in a mix track.

Maybe a mix isn’t allowed if one or more tracks have different delays. I’m just not aware what is physically happening in the MixPre.

I can't speak to the mixpre series with first hand knowledge, but what you do with other systems is the following.

1. track 1 has 19 ms of latency.
2. track 2 has 15 ms of latency.
3. track 3 has 10 ms of latency.
4. track 4 has 0 ms of latency.

You would set the track delays as follows.

1. track 1 : 0 ms delay
2. track 2 : 4 ms delay
3. track 3 : 9 ms delay
4. track 4 : 19 ms delay

This ensures all the audio tracks are in sync with each other.

Next you adjust the audio tracks as a whole to be in sync with your cameras. Or, you adjust the cameras to be in sync with the audio depending on how you look at it.

this will get everything in sync within roughly +- half a frame with timecode. To do better than half a frame you need genlock.

Thanks Dan, that was what I was going to suggest. The PixE has the opposite issue, with Audio arriving before the video, since the PixE records audio and video together. You delay each track as required to be in sync with the video from the camera (which is delayed).
Cheers

Dan, that’s what I was expecting to get all audio reflecting the same time on the audio tracks and any mix tracks. In your example, let me just reference 1 and 4 to ask a question. Assume all devices sync to the MixPre via Tentacles on the camera.

Don’t worry if my math is off in this question, it’s rounded only for illustration ignoring audio subframes. Assume 50 fps video, or one frame every 20msec, so 19msec will round to 1 frame for this question.

Actual video Timecode clip for all cameras:
start value 00:00:00:00.

External audio start Timecode recorded in MixPre with no delay assigned:
Track 1 AVX (19msec delay) 00:00:00:01
Track 4 wired mic (no delay) 00:00:00:00

External audio Timecode with delay assigned:
Track 1 no additional delay so Timecode 00:00:00:01
Track 4 added 19msec delay, Timecode 00:00:00:01

Does this seem correct? When synced in DaVinci Resolve the very first video frame won’t have any audio and all video except the AVX will be ahead a frame. I think that’s wrong so internally in the MixPre, the audio track is written with the first audio frame starting at 0 and the delayed tracks have their Timecode adjusted as applicable for their mic delay so they all start at 0 too.

External audio Timecode corrected for delay assigned:
Track 1 no additional delay Timecode 00:00:00:00
Track 4 added 19msec delay Timecode 00:00:00:00

My terminology may be incorrect, but is that what happens, you don’t have any audio gap at the beginning of a clip?


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@rick.lang The following is just my educated guess, so take it with a grain of salt.

Altering the timecode inside the recorder can't be what they are doing, because that wouldn't work with the stereo mix, and poly wav files you can generate. It also won't work when the recorder is used as a usb audio interface.

All these recorders offer pre-roll functionality. To support pre-roll, they have to be buffering the input in memory. I think they use oversampling for level monitoring, and that also needs a buffer. In relativity they are probably using several buffers along the processing chain to support various features.

Since the recorder has some amount of data buffered at all times, it can use a simple offset when reading from the buffer to get everything in sync. This would work with all forms output.

Makes sense, Dan. Minimum 5 seconds pre-roll on the MixPre II and up to 10 seconds for lower frequencies. I think they must have this all figured out and it just works. Will be so nice not to have to manually sync video and audio next year.


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Yes, they delay the recording of the delayed tracks, to have them all time correctly. On the Pix, the audio tracks are actually buffered, and then the sync recording is delayed by the amount of offset (delay) set for that track. The MixPre II should be doing the same thing. This gets all the recorded tracks matching, which is the goal, so any internal mixes will not have a track delay, which you would hear in the monitor.
Cheers

Decision made: Today, I shall order the Sound Devices MixPre-6 II rather than the Mix-Pre-10 II. Besides more inputs the only advantage that might matter to me is the balanced audio out on the larger model to feed the camera. I think I’ll not use that option trying to save several hundred dollars and just record audio in the MixPre-6 II. The cameras will use scratch audio only.

Today also ordering a single additional Tentacle Sync E so I can use the Tentacles to sync Timecode on both the URSA Mini 4.6K and BMPCC4K. Any statements about the reliability of using the internal clock to maintain a jammed clock have lacked specificity and I don’t trust warm and fuzzy when I need things to work easily in post.


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Mine's en route, due to arrive tomorrow.

How long did it take to get from when you ordered. Did you order from a local supper directly from Sound Devices?


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I ordered from Sweetwater Sound yesterday, shipped via Fedex 2nd day.

My dealer is sold out! Need for late September!!!


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My dealer is sold out! Need for late September!!!

D'oh! Check with Sweetwater?

I might have lucked out there, because my rep at Sweetwater held one for me so that I didn't have to worry about getting scooped.

I’m in Canada and ordered from a small authorized Vancouver BC dealer that will talk to me; the authorized large Vancouver dealers don’t waste time on little people like me.


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That's one reason that I get most of my audio gear from Sweetwater... they treat us little guys quite well

What I don't know is whether or not Sweetwater can ship to you up in BC... but it's worth a shot?

Decision made: Today, I shall order the Sound Devices MixPre-6 II rather than the Mix-Pre-10 II. Besides more inputs the only advantage that might matter to me is the balanced audio out on the larger model to feed the camera. I think I’ll not use that option trying to save several hundred dollars and just record audio in the MixPre-6 II. The cameras will use scratch audio only.
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Rick, you can still send an unbalanced output from the MixPre to the Picket 4K Camera, with the MixPre’s 1/8 TRS stereo out. This will get you a better scratch audio, unless you are going to leave the Tentacle TC jam connection to the camera.
Cheers

What I don't know is whether or not Sweetwater can ship to you up in BC... but it's worth a shot?

A good source for audio gear in Canada is Studio Economik here in Montréal; they ship everywhere in Canada. I get all my audio equipment from them and they're great to deal with.

Brad and Rakesh, Sennheiser Canada must handle sales in Canada. The Sennheiser US is not licensed to sell to Canada. If Sennheiser Canada did not exist, then Sennheiser US cannship to Cansda. I’ve run into this before.

And in Canada the retailer must be here as they don’t sell direct to customers. I could go with Montreal of course as I’ve done but Vancouver has been giving good advice. Thanks for the advice, guys.

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The question of power. I can order the ac/dc power supply or order the sled that takes two large approved Sony L-series batteries and order a charger. For those who care to comment are you ordering both large sled and power supply or just one of those? I want to be ready to shoot all day if needed. The included four batteries are only good for emergencies. Not for a day’s shoot.

Most times I shoot interior with power available but battery much more convenient and sometimes may be the only option.

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I have one of the dual battery sleds, which I plan on moving to the new mixer when it arrives. With a full charge on both batteries, it can keep the mixer going for a weekend.

Do you use a pair of the approved XL-B3 Li-ion batteries?


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Okay ordered the L-series sled and dual XL-B3 batteries and ordered the power supply unit as well. That’s the way I usually shoot so I’m prepared for any power eventuality. I’ll provide my own 128GB SDXC Card and USB thumb drive for backup.


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Today also ordering a single additional Tentacle Sync E so I can use the Tentacles to sync Timecode on both the URSA Mini 4.6K and BMPCC4K. Any statements about the reliability of using the internal clock to maintain a jammed clock have lacked specificity and I don’t trust warm and fuzzy when I need things to work easily in post.

Are you asking about the accuracy of the MixPre-6 II, Tentacle Sync E, or URSA Mini 4.6K and BMPCC4K internal clocks?

Personally I'd put them in this order from most trusted to least.

1. Tentacles
2. MixPre-6 II
3. URSA Mini 4.6K
4. BMPCC4K

Okay ordered the L-series sled and dual XL-B3 batteries and ordered the power supply unit as well.

I have both as well. The only thing to be careful of with the power supply unit (unless this changed with the second generation) is that it uses a USB-C input and mine disconnected a few times when I was moving the recorder around. For that reason whenever I use it plugged in to AC power I keep a set of batteries in the sled so it can instantly switch to battery power if the plug disconnects.

Yes that’s the plan; thanks.


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Thanks, Dan. I’ll use a master Tentacle to jam the MixPre II and the other Tentacle and leave the two Tentacles on the two cameras and live happily ever after!


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I’m thinking 192KHz may not be required though for an indie narrative film so may record 96KHz. Appreciate any feedback on that rate since I don’t know what is typical for these things.

I recall having worked at 96kHz only once in my career (for audio-post, music is different), and it annoyed me and I told the producers to record at 48kHz moving forward. That was for a radio soap opera. It didn't need the higher sample rate for "quality" purposes, nor for processing purposes. It was just a waste of drive space and taxed the (now decommissioned) computer to the edge.

Every single time other than that I've received audio at 48kHz for location sound and adr/narration. Music and fx have originated as 44.1kHz or 48kHz.

I don't know of anyone that works at a rate higher than 48kHz except for sfx guys. I can see how some doing music would prefer it, but I can also see how many won't care.

One thing to consider is just where post is being done and just how "indie" it is. The lower the budget I'd assume the "lesser" the space/gear. It doesn't necessarily mean poor gear, but it might mean that instead of a fully decked out PT HDX system you'll have someone mix on a native system instead, and it might be fine running at 48kHz, but at twice that rate CPU demands start getting out of hand. So speaking of noise reduction one thing I would imagine would be problematic is running iZotope RX plugins in real time in the post session. Not saying everyone will or should do it, but they can be quite resource hungry and bumping everything up to 96kHz might force the audio people to make some annoying choices (I.e. route differently or process offline).

I'd ask those doing post for the film if they have a preference, if possible. 96kHz is fine I guess since it can always be down sampled by the post people if needed. But if you're recording only dialog then I have a hard time believing anyone would even raise an eyebrow over it being 48kHz.

Mattias, thank you for your well-informed advice. For the feature narrative film, I have been recording at 48KHz except for some SFX at 96KHz. With using 96KHz, I thought I was trying to strike a balance between the 44.1KHz on a CD or MP3 players and the 192KHz that Neil Young felt was needed for his Pono music player (which never really caught on). But for the narrative work then, I’ll stay with 24bit 48KHz. I didn’t realize that the audio in a movie theatre would be 48KHz, but of course with a lot of speakers.

I’m shooting a music video near the end of September. The music will be intimate acoustic and it’s not a convert hall orchestral symphony. Would you then also recommend I stay with 48 KHz then too. I’m going to assume you would!


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Mattias, thank you for your well-informed advice. For the feature narrative film, I have been recording at 48KHz except for some SFX at 96KHz. With using 96KHz, I thought I was trying to strike a balance between the 44.1KHz on a CD or MP3 players and the 192KHz that Neil Young felt was needed for his Pono music player (which never really caught on). But for the narrative work then, I’ll stay with 24bit 48KHz. I didn’t realize that the audio in a movie theatre would be 48KHz, but of course with a lot of speakers.

I think a DCP allows for either 48kHz or 96kHz, but Atmos for example specifies pretty limited response at 40Hz-16kHz for non-sub channels.. unless I read the specs wrong. Additionally distributors like Netflix and a bunch of networks all require deliveries of audio at 48kHz.

So at the end of the day it seems to me that most finished content is delivered at 48kHz, and even if it was 96kHz the actual monitor chain won't reproduce much above 20kHz anyway, let alone from there on up to 48kHz. I get that it'd allow for gentler filter slopes though, but still...

I’m shooting a music video near the end of September. The music will be intimate acoustic and it’s not a convert hall orchestral symphony. Would you then also recommend I stay with 48 KHz then too. I’m going to assume you would!

Again I'd say it's probably best to talk to those doing audio after you to see what the preference is. Music tends to be a bit different and I'm betting it's far more common there to use higher rates than in audio post (minus sfx). And believe me; there's quite the debate among many about the merits of at least capturing and processing at higher sample rates regardless of playback...

So in this case I'd probably just ask.

Mattias, I’m the audio guy as well as most of the other technical functions. I’m happy to record audio on the MixPre in 24bit 96KHz for the music video. Capturing is one thing where it might be good to get more detail, post another. I could still deliver 48KHz. I think this deserves another thread! You don’t have to repeat your remarks under the new Topic.


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Do you use a pair of the approved XL-B3 Li-ion batteries?

Yes, I think those are the ones. The kind you usually see on Sony camcorders. Since the recorder itself is so small the batteries seem pretty big by comparison.

Thanks, Rakesh. I bought almost everything except their branded 32GB SDXC UHS-I Card. I’ll use my 128GB WIse UHS-II Card for now in compatibility mode. I’m sure it does 90MB/s or whatever their branded card does.


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Should do the trick. I've been using a 32GB SD card that I repurposed from an older camera. 32GB has been plenty for film production. We've done full shoots without remembering to format the card from the last shoot.

It might not work Rick. I got a larger, faster CF card for an older SD recorder, exceeding SD specs, and it did not work, it wanted the 32GB cards on their list.
Cheers

Ouch! Okay I’ll add the SD branded 32GB card tomorrow morning. Thanks for the tip!


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The SD card support for the Mixpre first generations are in the same mess as the ones for BMPCC/BMMCC.
Many works great, unless you aim to record all channels at highest bitrates. Then barely no other cards works.
Sound Devices branded smallish 32GB (which is the online they list as approved media) do work anyway as well as Integrals UltimaPro 128/256/512 GB cards.(Same ones that works good in the Micro Cinema)

Sound Devices management is in the loop and up to date with the problem - at last - but if they will be able to find a solution is still a question.

If this still is a problem for the MixPre II or not is not known yet.
There have been no information about any changes to the hardware or firmware regarding the SD-card problems.

I’m the audio guy as well as most of the other technical functions.

There's a famous underground filmmaker who routinely recorded sound by holding the 16mm camera with one hand on his shoulder and in the other a small stereo tape recorder with sync pulse and a mic pointed at the talent.

That aside, 6" of microphone placement will have more effect on dialogue quality than the difference between 1990s semi-consumer analog equipment and recording dialogue at 192Khz with the latest in 2019.

In a word, if you want good sound, hire a sound person. Or at least some reasonably capable person who does nothing but sound.

In a word, if you want good sound, hire a sound person. Or at least some reasonably capable person who does nothing but sound.

That's always been my preference also!

But some of the folks that do sound on productions I work don't own their own sound gear. They know what they're doing, so I just provide them the gear and let them do their job.

John, thanks. I’m using my AVX MKE2 lavalier mic going into the MixPre for the principal singer so that will be 6-8” away. Using the MKH416 to record the youth singers in the chorus.

But I am thinking today that I need that MKH416 on a boom and connected to the MixPre as well rather than on my camera. Considering ordering the EW 500 analog system that includes another MKE2 lavalier or will support the MKH416 plugged into the transmitter with its phantom power. Arranging for a sound person as well. When I said “I’m the sound guy, I was referring to audio post processing.

Apologies if I go off topic, but anyone care to recommend a boom that they like to use? Carbon fiber or aluminum? With cable or without? If I have the EW 500, I don’t need a boom with cable as it’s wireless.


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Update on the Sennheiser EW 500 Boom G4: I ordered this today from Vancouver and will have it delivered Monday. I’ll be using it with the Sennheiser MKH416. Just need to find a boom locally in a hurry.


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Wouldn't your location sound person already have a boom? If you're recording singers, a microphone stand or c-stand might work instead of a boom. I have to say, the MKH416 would not be my first choice for recording a chorus; a better choice would be a stereo pair of omnis or a stereo pair of cardioids in ORTF or some similar configuration; if you're going to use the shotgun mic I'd keep it pretty far back from the chorus otherwise it's just going to pick up individual voices. And for that you wouldn't need a boom, just a mic stand.

Good advice Brad so thanks. I’m using what I have. The MKH416 isn’t really narrow and picks up wider than real shotguns. After reading your comments, I’ll keep the children quite close together though so it will work. The room is a fairly large living room and I think I can keep that mic back sufficiently.

What mics would you use?

My sound guy doesn’t have a boom. For the first scene in the movie, we used tape and held a C-stand folded and extended!


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Oh, lord, don't use the 416 for a chorus. Any cheap music/vocal mic would better.

Oh, lord, don't use the 416 for a chorus. Any cheap music/vocal mic would better.

John, would a Shure SM58 dynamic work on a boom or us this for really up close singing rather than a small chorus?


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The 58 is usually for a single voice. For ensembles, and using only one mic, I'm not sure. I think you want cartoid condenser. The worry with the 416 is that it could give you a strange result, given the pickup pattern and the shotgun design where there are lots indoor reflections.

One of my favorite cardioid condensers is the Rode NT-1. It's dirt cheap, but doesn't sound at all like a dirt cheap mic... great sound, next to no noise. I've used it as a supplemental mic for room recordings.

Thanks, Rakesh. I’ll see if I can find it locally and I suspect I can.


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I'd expect so. Any shop that carries Rode products probably has some floating around.

What mics would you use?

Rakesh's suggestion will probably work out for your upcoming shoot, but if you do more of these types of shoots in the future an affordable option would be a couple of mics from Line Audio, a Swedish maker that has a representative in Manitoba or Alberta named Nicholas Hayes. Their CM-4 cardioid (formerly the CM-3) has been compared very favourably to Schoeps mics that cost 10 times as much (the CM-4 is around $200 Canadian). There were some independent blind tests where experienced audio engineers couldn't tell them apart, or preferred the sound of the Line Audio to that of the Schoeps. Two of those CM-4 mics on a stereo bar in ORTF should capture a chorus well; another good option is Line Audio's OM-1 mics, which are omnidirectional and would be also good for a chorus if you're in a nice-sounding space as they'll pick up much more of the room sound.

In general for a chorus you'd want to record in stereo with two mics (at least), but if you only have one mic it'll work if you set it far enough back...you can put headphones on and experiment to find a place where it sounds the best.