Live recording

Moderators: rick, Mark Bassett, gigpiglet

Live recording

Postby Ben M » Sun Nov 06, 2011 9:26 am

Hi all

Anyone doing fairly serious live recordings? ie. for additional releases.

Interested to know how most people are interfacing with the live show. Do you use your own isolated splitters (any recommendations)? Or a combination of splits from the console and additional mics on stage.
What is your setup in general for live recordings.

I'm very conscious about not relying too much on what's setup for the live show (or interrupting this) and what's needed for my recordings. Being completely independent in this situation is obviously better. But it does involve a lot more equipment and setup.

Let me know your thoughts and setups.

cheers
Ben
User avatar
Ben M
Valued Contributor
Valued Contributor
 
Posts: 1920
Joined: Fri Jul 04, 2008 11:54 am
Location: Sydney and Kangaroo Valley, NSW

Re: Live recording

Postby Kurt » Sun Nov 06, 2011 11:39 am

I do live sound and recording, I guess that makes part of it much easier as I'm not working around somebody else.

I run a compressor in line on every channel, I patch in\out using xlr, leaving the trs out of each able to be plugged into my HDD recorder. I have a pair of 8 way trs looms numbered 1-16 I can patch it in very quickly. Even if the compressors are in bypass they act as splitters. The only hassle is that any fiddling with the compressors affects the recorded signal.

A while ago I was involved in a project called "Hard ACT to follow" which was an album of live performances by local bands. Several were recorded using my HDD recorder, another guys splitters and desk running sidestage, for all the extra complication I don't know that the results were any better, but at least I didn't have to worry about the recording part as well as FOH.
Kurt Neist
Chief cook and bottle washer - Metalworx
User avatar
Kurt
Valued Contributor
Valued Contributor
 
Posts: 1235
Joined: Sat May 07, 2005 1:02 am
Location: Canberra

Re: Live recording

Postby Ben M » Sun Nov 06, 2011 2:09 pm

Kurt wrote:I do live sound and recording, I guess that makes part of it much easier as I'm not working around somebody else.


Yes, much easier Kurt. Unless you start getting annoyed with your other self for getting in the way. :)

Kurt wrote:The only hassle is that any fiddling with the compressors affects the recorded signal.


I guess this is the main reason I want to be setup independently. So levels stay constant and any processing by the live engineer doesn't effect my recordings.

I guess if I want to be free from the inhouse system then the main addition to my setup would be a multi mic splitter. Does anyone know of any reasonably priced splitters (16 channels or more)?

I have a couple of large scale live recordings to do early next year and I guess I ultimately don't want to be patching out of someone's setup or being reliant in any way to the live production team.

Also I have a bunch of 2 unit vintage strip pre's (i don't want to lug these around with me) and other 2U pre's and would probably benefit from a couple of 1U or 2U 8 channel pre's. Any suggestions here?
User avatar
Ben M
Valued Contributor
Valued Contributor
 
Posts: 1920
Joined: Fri Jul 04, 2008 11:54 am
Location: Sydney and Kangaroo Valley, NSW

Re: Live recording

Postby mylesgm » Sun Nov 06, 2011 4:09 pm

I would definitely go out and hire stuff for the recording if it's a critical job. Good, reliable and portable gear is expensive, just check out the cost of mic splitters! On the other hand cost of hiring a mic splitter, multi-core and two 8 channel mic pre (like the jlm 8pre) DAV BG8 etc is probably pretty cheap for one nights recording. What will you be tracking to? Reliability over a longish recording can be a real issue as can quality of available power. Mat Robbins has an excellent setup of a Ta@#$% 24 track, 3x presonus m80 mic pres and I'm sure he'd be full of good info for this setup.

I just recorded some concerts at a major performance venue here is melbourne and though venue the spec looked good on paper the result was poor. Clicks and pops through out the recording post the 30minute mark, buzzes on long cables runs etc. was (and still is) a nightmare.
Myles Mumford
Producer/Composer/Engineer/Sound Artist
Making records in sunny Melbourne

www.mylesmumford.com
User avatar
mylesgm
Valued Contributor
Valued Contributor
 
Posts: 1963
Joined: Mon Feb 09, 2009 6:48 pm

Re: Live recording

Postby obutcher » Sun Nov 06, 2011 11:01 pm

If I'm doing live sound and recording the show, I'll try and pick up a system that is designed to do both. MUCH easier than relying on a separate computer and if the system is contained you don't have to carry extra gear. Also, unless you got to a venue super early, you don't always have time to set up separate live and recording systems. The usual live issues (hums, noisy sends, feedback issues) end up taking precedence over the recording as you've still got a band and room full of punters to keep happy.

That said, if it's something you NEED to have high quality, passive splitters and your own great pre's are pretty damn good :)
Owen Butcher
obutcher
Registered User
Registered User
 
Posts: 216
Joined: Wed Jun 30, 2010 4:35 pm
Location: Sydney

Re: Live recording

Postby gigpiglet » Mon Nov 07, 2011 2:38 am

oh my god my favourite topic!!!!!!!!!!!

so I've been live recording since it really started to be a "thing"
i was obsessed with my 4 track minidisc recorder in the 90s
and bought one of the first (Ta@#$%) CD recorders after that
and then the Ta@#$% MX2424 hard disc recorder
i did so many records/ DVDs/ live whatevers on those machines that you could say i was a worldwide expert on them...

these days i run racks with joeco black box machines - cause they are amazing (and super small/ light and use standard USB discs)

but whatever it is you are using to record, the fundamentals remain the same:

basically two ways to go about it
1 - split at the stage box and have a separate system with your own pres into you recorder (the right way)
2 - take (direct or bus or whatever) outputs from FOH console, plus audience mics! (the cheap way)


we have racks that have a 24 track recorder, and 24 ch of pre amps.
these work for 99% of our jobs
everynow and then someone want to take out the neves etc for a live show, and we can do that...

for splits i ALWAYS use CODA passive racks. not only are they amazing, the multi pin system is brilliant, and they are a cheap hire.

we have done an awful lot of this, including a lot that are simultaneous live broadcasts.
i love it! so ask away and ill answer anything i can.
Gareth Stuckey
gigpiglet productions:presents:recordings
gigpiglet
Valued Contributor
Valued Contributor
 
Posts: 1153
Joined: Tue Jun 01, 2010 4:10 pm
Location: sydney australia

Re: Live recording

Postby Ben M » Mon Nov 07, 2011 11:13 am

Awesome chaps.
I should’ve stressed that I’ve done my fair share of live mobile/location recording in the past however this is a bit different seeing I was contemplating taking splits from the venue’s FOH console and working in with an already existing system. Also I won’t be mixing the live sound. Just recording.

I’ve ultimately decided to set up a completely independent system to the in-house console splits. The only reason I was contemplating patching out of the in-house system was because they run a Yamaha M7CL and there are so many outputs on those things. The venue also has xlr patchbays everywhere, which I thought could be handy for me. But that is now crazy talk really. I will stay separate.
The venue is a 1000 seater regional entertainment centre, which is fairly new. I’ve recorded an orchestra a couple of times in this room but not with an audience or a live mix going on. I didn’t have any problems with power, noises, hum, etc… but I know what you mean.

Ultimately I’d like to put together a good/compact system to do more mobile live recording in the future because I’m getting more inquires about doing this sort of recording… and I really enjoy it. So perhaps purchasing 2 or 3 - 8 channel pre’s and then probably hire a good isolated splitter when I need it. The Coda splitters look great with the lundahl trannys. Do you know the hire price off the top of your head Gareth? Are these the particular splitters you mean? http://www.coda-audio.com.au/sales/dist ... stems.html

The band I’m recording will comprise of - Drums, bass, electric guitar, acoustic guitar, 2 x keys, piano, cellist, main vocalist, 3 BV’s, audience mics and possibly a 35 piece choir. (My head hurts already)
Vocalists will be using wireless shure mics. I’m not sure where the receivers are kept but I’d guess they would be side of stage. I'll find out soon.

ATM I have 3 choices for my recording rig (but no idea for a backup system ATM);
1. My old PT Mix system 24I/O on 888/24’s
2. My HD2 system with my Symphony I/O 16 I/O
3. or.. My mac book pro with Symphony 16 I/O
Straight up I think I’ll need as many tracks as possible so the Mix system will probably get a run on this. Still no backup system though???? eeeK!

Gareth could you tell me what your rack of 24 pre’s that you use is?
What do you run as a backup recorder? If your running a backup recorder what method do you use to chain these machines for signal. If I use my PT rigs and the first computer crashes then that would shut down the signal to the chained backup machine. I guess that’s why you use a dedicated live recording devices like the joeco. I must say they look perfect for this sort of work. Out of interest can you solo tracks while recording with the black box recorders? How do you monitor individual tracks?

Also, audience mics? In the past when I’ve done smaller live recordings I’ve put up an A/B pair so I’m capturing audience and FOH. Do you have any favourites when it comes to positioning these mics? I guess it would change from venue to venue but maybe you have a rule of thumb. I will only have one pair available for audience btw.
Anyway, I’m just starting to piece this system together so it’s great the flesh it out here before I go too much further.
Thanks for you input everyone.
Last edited by Ben M on Tue Nov 08, 2011 7:02 am, edited 1 time in total.
User avatar
Ben M
Valued Contributor
Valued Contributor
 
Posts: 1920
Joined: Fri Jul 04, 2008 11:54 am
Location: Sydney and Kangaroo Valley, NSW

Re: Live recording

Postby ftdrummer » Mon Nov 07, 2011 11:31 am

I have had good results using passive Y splits and a rack of Yamaha MLA8 pres which are a bargain! They are based on DM2000 pres. I haven't had issues thus far with ground loops or hums, but I've only had relatively short cable runs using my own multicore. There are some cheap transformer splits such as the ART S8, but a few ARX active units would nice! Try and avoid taking direct outs from FOH to maintain consistent gain levels.
ftdrummer
Registered User
Registered User
 
Posts: 42
Joined: Thu May 26, 2011 3:59 pm
Location: Melbourne, VIC

Re: Live recording

Postby mylesgm » Mon Nov 07, 2011 11:47 am

I've found the Klark Teknik splits to be noisy so I would avoid those.
Myles Mumford
Producer/Composer/Engineer/Sound Artist
Making records in sunny Melbourne

www.mylesmumford.com
User avatar
mylesgm
Valued Contributor
Valued Contributor
 
Posts: 1963
Joined: Mon Feb 09, 2009 6:48 pm

Re: Live recording

Postby Chris H » Mon Nov 07, 2011 1:28 pm

ftdrummer wrote:I have had good results using passive Y splits and a rack of Yamaha MLA8 pres which are a bargain! They are based on DM2000 pres. I haven't had issues thus far with ground loops or hums, but I've only had relatively short cable runs using my own multicore. There are some cheap transformer splits such as the ART S8, but a few ARX active units would nice! Try and avoid taking direct outs from FOH to maintain consistent gain levels.

......and I have had passive splits ruin a nights recording in a venue i didn't know. They had a common earth on one of their multicores and one lead was faulty sending crackles etc through other chanels. Was almast impossible to trace where the problem was. Passive splits are ok if you know the venue has good reliable gear and you have checked every line. The old Continental Cafe had passive splits on the stage box for monitor console operation from side stage. The shows i recorded had monitors from FOH so I used the stage box splits for recording with no problems. Don't try it at Ruby's Lounge in Belgrave. I'ts a dog of a PA system.
Chris Hallam.
https://soundcloud.com/hallamsound
Whatever floats your boat.
User avatar
Chris H
Forum Veteran
Forum Veteran
 
Posts: 2319
Joined: Mon May 09, 2005 11:20 am
Location: Off The Planet

Re: Live recording

Postby obutcher » Mon Nov 07, 2011 5:31 pm

I'm doing a live recording next week with 40ch of input, using passive splitters. The split is going to another room behind stage with an LS9-32 and an 8ch mackie onyx pre. Those pre's are then going into a Protools HD rig. The different bands will be run through the LS9-32 and have scene memories saved for them, while audience mics + presenter mics will be preset and run through the Onyx.

Should be good fun, there will also be a large band, choir, audience mics etc. Might even post some photos post-gig.
Owen Butcher
obutcher
Registered User
Registered User
 
Posts: 216
Joined: Wed Jun 30, 2010 4:35 pm
Location: Sydney

Re: Live recording

Postby Ben M » Tue Nov 08, 2011 6:21 am

obutcher wrote:I'm doing a live recording next week.....Should be good fun, there will also be a large band, choir, audience mics etc. Might even post some photos post-gig.


Great Owen! Will be cool to see how it all went. Keep us updated.

How many people run a backup recorder when doing their live recordings? I have a continuous 2 hour show to record. Although I've never had issues with using PT doing long recordings, the length of this show is worrying me enough to want to run a backup of some sort.
User avatar
Ben M
Valued Contributor
Valued Contributor
 
Posts: 1920
Joined: Fri Jul 04, 2008 11:54 am
Location: Sydney and Kangaroo Valley, NSW

Re: Live recording

Postby NathS101 » Tue Nov 08, 2011 7:39 am

jumping into this a little late as I've been flat out lately...

if you need 48ch of mic splitters, brad law from Cuepoint Productions has 6 klark technic 3-way splits as well as 6 audient ASP008 8ch preamps.
as for recorders, andrew crawford/jim monk from 11th hour studios have 2 Ta@#$% X48s in a portable rack plus DB25 cables. can either run together for up to 96 tracks or as master & backup (with DB25 passive Y-splits into each recorder).
stage boxes & multicores are easy enough to hire from a PA company.

ive used their gear and worked with them a number of times for live records including a 64 track live album recording last weekend at acer (allphones) arena with 96ch off stage + 16ch of audience into 2 heritage 3000s. worked well.

if it's a once-off show definitely have a backup, if it's a few shows you could risk it... I did a christmas show record last year without a backup but it was half a dozen shows plus rehearsals.


just my 2c...
NathS101
 

Re: Live recording

Postby Ben M » Tue Nov 08, 2011 7:48 am

NathS101 wrote:jumping into this a little late as I've been flat out lately...

if you need 48ch of mic splitters, brad law from Cuepoint Productions has 6 klark technic 3-way splits as well as 6 audient ASP008 8ch preamps.
as for recorders, andrew crawford/jim monk from 11th hour studios have 2 Ta@#$% X48s in a portable rack plus DB25 cables. can either run together for up to 96 tracks or as master & backup (with DB25 passive Y-splits into each recorder).
stage boxes & multicores are easy enough to hire from a PA company.

ive used their gear and worked with them a number of times for live records including a 64 track live album recording last weekend at acer (allphones) arena with 96ch off stage + 16ch of audience into 2 heritage 3000s. worked well.

if it's a once-off show definitely have a backup, if it's a few shows you could risk it... I did a christmas show record last year without a backup but it was half a dozen shows plus rehearsals.


just my 2c...


Thanks Nathan... This is a one off for this group (although I'll record again with them later in the year) and it will be filmed aswell. This is for a DVD. Backup makes a lot of sense in this case.
User avatar
Ben M
Valued Contributor
Valued Contributor
 
Posts: 1920
Joined: Fri Jul 04, 2008 11:54 am
Location: Sydney and Kangaroo Valley, NSW

Re: Live recording

Postby NathS101 » Tue Nov 08, 2011 3:48 pm

also if it's a professional multi-camera shoot (as opposed to a few handy-cams), try and get timecode and video black-burst from the systems techs to sync your master recorder.
that's what I did for the christmas show with the tascams; synced timecode, video black, word clock and MMC... worked without any dramas.
then in post all they have to do is spot those clips onto the timeline and it won't drift out out of sync with the video.
it's not essential but it helps
NathS101
 

Re: Live recording

Postby audioio » Tue Nov 08, 2011 11:01 pm

Ben M wrote:I have a continuous 2 hour show to record. Although I've never had issues with using PT doing long recordings, the length of this show is worrying me enough to want to run a backup of some sort.

Never had Pro Tools choke on a long continuous recording... either HD or lower. I've only had a weird thing recently using PT9 for multichannel playback (multiple cues, lots of start and stop) and it played two different parts of the timeline simultaneously!

Haven't been able to replicate that since.
David Rodger
audioio
Regular Contributor
Regular Contributor
 
Posts: 420
Joined: Wed Jul 28, 2010 4:05 pm

Re: Live recording

Postby Kurt » Tue Nov 08, 2011 11:22 pm

The 28, 000, 000 + results when one searches for "pro tools crash" suggests perhaps your experience is not the norm..

https://www.google.com/search?q=pro+tools+crash

audioio wrote:
Ben M wrote:I have a continuous 2 hour show to record. Although I've never had issues with using PT doing long recordings, the length of this show is worrying me enough to want to run a backup of some sort.

Never had Pro Tools choke on a long continuous recording... either HD or lower. I've only had a weird thing recently using PT9 for multichannel playback (multiple cues, lots of start and stop) and it played two different parts of the timeline simultaneously!

Haven't been able to replicate that since.
Kurt Neist
Chief cook and bottle washer - Metalworx
User avatar
Kurt
Valued Contributor
Valued Contributor
 
Posts: 1235
Joined: Sat May 07, 2005 1:02 am
Location: Canberra

Re: Live recording

Postby gigpiglet » Fri Nov 11, 2011 4:45 am

sorry for the no response guys... its been a busy week of big shows.
so sum up the above (in my opinion)

1: splits - the coda ones are amazing. and somewhere around $100/ 24 ch. cause they have no gain (unlike the klarks and XTA) you never have any hassle adding them into a system. e.g.: some international acts won't want you to add a split in front of their system

2: PT is not a live recording system. no matter what you think, or what your mates say... it "can" work ok "most" the time... but no way in the world would i record a live show to PT without some redundancy.

3: redundancy for us is just another of the same rack

4: re the joeco, i could go into detail, but maybe audio technology my review of it, covers a lot. there is a power fail safe loop out.. or i can take separate outs of my pres (analogue to one machine, dig to the other)

5: audience mics. at least one each side of stage, or even better a pair each side (in XY) i also often like to have a pair at the FOH position (facing away from stage) and often record this as a totally separate system to a CD burner. think of it like a "room mic"

mmm all for now - its late
Gareth Stuckey
gigpiglet productions:presents:recordings
gigpiglet
Valued Contributor
Valued Contributor
 
Posts: 1153
Joined: Tue Jun 01, 2010 4:10 pm
Location: sydney australia

Re: Live recording

Postby Ben M » Mon Nov 14, 2011 12:43 pm

Thanks for that Gareth. If I can think of some other Q's I'll post them up.

Thanks everyone. :ymhug:
User avatar
Ben M
Valued Contributor
Valued Contributor
 
Posts: 1920
Joined: Fri Jul 04, 2008 11:54 am
Location: Sydney and Kangaroo Valley, NSW

Re: Live recording

Postby Toddo » Wed Nov 23, 2011 12:23 pm

Once again I have to agree with Gareth. The Coda ones are great. Of course it depends on your budget, but splits to a backup record is recommended when you can. Also try recording to a hard drive array as it is a bit safer than a single drive (i.e. 2 copies simultaneous from the one source). Always back up after the gig too so you have at least 2 copies of the files from each rig. Hard drive space is so cheap these days, there is no excuse for not doing it.
Tod Deeley
Recording & Live Engineer/ Mixer/ Editor, Sound A/V Technician.
http://www.toddeeley.com.au
Toddo
Registered User
Registered User
 
Posts: 24
Joined: Tue Jun 22, 2010 1:00 am
Location: Sydney

Re: Live recording

Postby obutcher » Thu Nov 24, 2011 9:46 pm

Agree with Gareth, Protools is not an ideal live recording system but that was the equipment I was given to use.

As promised, here is a photo from the show. It was the end of year JMC showcase in Sydney (where I find myself working). The recording rig. Yamaha LS9 and a Mackie Onyx pre into a 192 + 2x96's. Notice the 2nd Mac Pro? I don't trust computers to not die!
Image

Ben, where on stage is your choir going to be? Ours was front and middle and got tons of spill from the drums and 8 piece horn section at were behind them! Eventually there'll be the recording from the show on youtube at some point (maybe even months away!), I can link it here if people wish to see it.
Owen Butcher
obutcher
Registered User
Registered User
 
Posts: 216
Joined: Wed Jun 30, 2010 4:35 pm
Location: Sydney

Re: Live recording

Postby Drumstruck » Fri Nov 25, 2011 9:03 am

Nice to see that you have a rear view mirror in case anyone is sneaking up behind you...... :-o
Ian Dare
Drumstruck
Valued Contributor
Valued Contributor
 
Posts: 1589
Joined: Fri Sep 17, 2010 12:37 pm
Location: NSW South Coast

Re: Live recording

Postby Ben M » Fri Nov 25, 2011 9:54 am

Thanks for posting Owen. Just what I wanted from the thread - pics and ideas of peeps setups in live/location recording.
As for the choir, it's not confirmed that they will be involved yet (recording is in March 2012) but placement will ultimately be up to me. Away from the drums will definitely be a good plan.
You guys have got me thinking about my recording medium on this job. I have used PT for live recordings before and with no problems (touch wood) but as I said this is a one off performance and feel I should maybe hire a dedicated live recording system, like Joeco. Gareth has put the fear of god in me with his comment about using PT. It's just going to put a dent in my budget.

Looking forward to hearing the mix of your recording Owen.

Cheers
Ben
User avatar
Ben M
Valued Contributor
Valued Contributor
 
Posts: 1920
Joined: Fri Jul 04, 2008 11:54 am
Location: Sydney and Kangaroo Valley, NSW

Re: Live recording

Postby obutcher » Fri Nov 25, 2011 7:43 pm

Drumstruck wrote:Nice to see that you have a rear view mirror in case anyone is sneaking up behind you....


Makes it easier to fix my makeup ;;)

Thanks Ben. Will let you know when it's up!
Owen Butcher
obutcher
Registered User
Registered User
 
Posts: 216
Joined: Wed Jun 30, 2010 4:35 pm
Location: Sydney

Re: Live recording

Postby NathS101 » Fri Nov 25, 2011 11:52 pm

Just came across this thread again.
I must be part of the minority that has never had any problems doing live recordings in protools... theres nothing special with the HD systems I've used, all run on macs with 6Gb RAM and recording to external hard drives via firewire 400 or 800. For the live record earlier this month we recorded 64 tracks to Tools as the main recorder and the tascams as a backup. After sorting out some routing problems in tools and replacing a munted external hard drive for the backup, neither skipped a beat during the recording. Today I was talking to a mate who recorded 96 tracks for 2 hours with a digi profile onto an internal 2Tb drive without any dramas...
As I said previously, as long as you have a reliable backup if running tools as the main recorder ;)
nath
NathS101
 

Re: Live recording

Postby NathS101 » Fri Nov 25, 2011 11:57 pm

here are some pics...

Image

Image

Image
NathS101
 

Re: Live recording

Postby AlCraig » Wed Nov 30, 2011 12:37 am

Ben
How many tracks are you planning to record?

And to the rest of you, does anyone need a good assistant to help with your live recording gigs? 35 years live broadcast experience has to be worth something to someone.

Ta
Al Craig
Al Craig
Black Inc Recorders
User avatar
AlCraig
Registered User
Registered User
 
Posts: 109
Joined: Mon Sep 20, 2010 5:28 am

Re: Live recording

Postby Damien » Tue Dec 06, 2011 10:07 pm

i have 3 options i use.
i usually do FOH for all the acts i record, or more accurately the acts i do foh for i record.
i also mostly use digidesign profile consoles with the HD AND FW options.

easy way. . plug my portable HD system into the HDX cards.. 96 channels.. hit record and im done.

harder.. limited to 18 channels... same console but use the FW option.. do some software patching and record 18 channels onto my laptop..

hardest...take the "live" rack. set up analogue splits and run seperate mic pres etc into HD system..

i have done 2 x live albums for leo sayer using option 1 and 2... it works and i have recorded most of this years shows this way.. another live release coming id say...
Damien Young
damienyoungmusic@gmail.com
0412 354 254
User avatar
Damien
Regular Contributor
Regular Contributor
 
Posts: 313
Joined: Sat May 07, 2005 5:02 am
Location: Melbourne

Re: Live recording

Postby gigpiglet » Wed Dec 07, 2011 1:31 am

just did one tonight... (mudhoney) in my usual fashion
splits from CODA
into my pre rack/ joeco
and splits out to my console where i mix the broadcast from (through a finaliser, which also feeds a CD burner)

tomorrow i have another where for a number of reasons - we will be using just a tools rig (digidesign console at FOH, no budget etc etc)
ill still be taking the finaliser/ CD burner rack and doing a matrix mix plus audience mics direct to CD as a "backup"
Gareth Stuckey
gigpiglet productions:presents:recordings
gigpiglet
Valued Contributor
Valued Contributor
 
Posts: 1153
Joined: Tue Jun 01, 2010 4:10 pm
Location: sydney australia


Return to Live Sound Forum

Who is online

Users browsing this forum: No registered users and 0 guests


cron