Recording levels

Discussion in 'Location Recording' started by tomu, Mar 25, 2012.

  1. tomu

    tomu Active Member

    I record live orchestral concerts using a Tascam DR-100 and Tandy/Realistic PZMs. I have to use these mics for various reasons including the layout of the venue and the need to carry both musical instrument and recording gear. Mics have 1/4 inch jacks and are connected to the DR-100 using XLR adapters. Recording settings WAV, 16 bit, 44.1 sampling frequency.

    Whilst the sound is fine, the recording level is very low, even with mic gain set at High and input level at max, and needs normalising before burning CDs. I've had these electret mics for 20+ years; will there have been any deteriorisation in performance in that time? If so, will it manifest itself in any other ways, eg noise of any description? Example via link to a short (1 minute) excerpt,

    (Expired Link Removed)

    Thanks for any help/info offered.
     
  2. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    Since you're better off running a little low than a little high that level seems reasonable. It's a lot easier normalizing a recording than it is to fix clipping.

    What adapter are you using from 1/4" to XLR? A quality transformer might be better than a simple passive adapter. Also, it's fairly common to convert the output of those mics to XLR.
     
  3. tomu

    tomu Active Member

    Thanks for the reply Bouldersound. I'm using a RadioShack 274-017C, which has a high impedance unbalanced input (1/4 inch jack) and a low impedance XLR output. This worked ok with Tascam's DA-P1 DAT recorder. I do feel a bit dubious about the recording level needing to be cranked up to max yet still requiring normalising. Perhaps there is a bit of less-than-optimum compatibility somewhere. Too low a level wastes a lot of the available bit capacity, does it not?

    I'm going to take the kit around to a friend's house and we'll record his electronic organ, which ought to produce a healthy level of sound, and see whether we can replicate any of the problems I have been getting. He also has the advantage of knowing what he's talking about, having worked in the audio industry; I have quite enough to cope with playing in the band!

    There may be various rogue factors contributing to the noise problem, given that the mic leads are not screened. We play in a church by Waterloo Station, with electric trains constantly passing and plenty of fire/police/ambulance traffic too. I'll must also make sure that it's nothing as basic as oxzdisation on the jack plugs.

    Watch this space!
     
  4. JoeH

    JoeH Well-Known Member

    Those unbalanced mics are notoriously quiet. If they're the ones I THINK they are, I have a schematic around here somewhere for converting them to phantom power, which helps somewhat....

    One solution might be to put a preamp right at the mic, keeping the unbalanced lines as short as possible.

    As for the normalizing and gain adjustment, I would think you're bringing up a lot of hiss/hum and general noise along with the signal, yes?

    I hope you find some more info with your friend when you take the mics over there. Keep us posted.
     
  5. Boswell

    Boswell Moderator Distinguished Member

    It wasn't clear whether the jack-XLR adaptor you are using is a straight piece of wire or a step-down transformer. Here is a short article about converting the output of the Tandy PZM to XLR, and a more extensive mod to use phantom powering instead of battery power to cope with greater sound levels before overload.
     
  6. RemyRAD

    RemyRAD Well-Known Member

    I still have 8 Radio Shaft Pressure Zone Microphones also from about 20 years ago. They are still in an absolutely perfect operating condition and sound marvelous. Their output level is as a healthy as any other modestly priced condenser microphone. There are a couple of simple things you can do to actually improve them for the cost of next to nothing. Those RadioShack transformer converters you are talking about that go from 1/4 inch to XLR is actually knocking your level down by more than 10 DB! It's completely counterproductive to do that. The little schematic that was included with that microphone indicates it already has a balanced output transformer. They unbalanced the output of the transformer and stick on the 1/4 inch connector. You merely cut off at 1/4 inch connector. Once you strip your wires back, you will find a red, white & wrapped shield ground. Shield goes to pin 1. Red goes to pin 2 and white goes to pin 3. Then you can actually run that cable 1000 feet/333 m. (Since I don't have them in front of me at the moment I might be incorrect on the phasing of the red and white? It might be white to pin 2 and & red to pin 3? You'll have to check the phasing against a known source factory built balanced output microphone of any type.)

    Then, while some folks of converted their's to phantom power, I did not find it to be an acceptable modification. So the easiest thing to do, is to either obtain 2 Eveready batteries. These batteries produced 6 V each and are one half the size of a AA battery. This will help to lower the noise floor and increase headroom and output levels. I even modified a couple with a pair of 9 V battery adapters and run a couple of those at 18 V. The batteries should be removed after each use regardless of the on-off switch and they are good for hundreds of hours of use. So that's what you should be doing to those. All you need is a couple of XLR connectors and 4 batteries for a pair of microphones.

    The reason why you're adapters aren't working properly is because the microphones are a low-level, low impedance output already. You're feeding them to a high impedance input and converting them to low impedance again and that's where you're losing 10 DB worth of level. If the adapter had no transformer in it, it would be modestly viable but still not balanced and so you would still be restricted to approximately 25 feet/8 m and it would still be susceptible to all sorts of RFI & electromagnetic interference since it would still not be balanced. But the microphone is actually balanced and it was unbalanced for consumer use yet, everything you need is inside the little plastic box that includes a balanced output transformer.

    As to their longevity, Radio Shaft utilized the same condenser microphone capsule from the company in which they licensed the PZM from which was Crown. And it's the same capsules listed in my $375 Crown Pressure Zone Microphone. So provided they haven't been sitting in a bucket of water, or left outside in your garage in the wintertime, the summertime, spring and fall, you should be fine. They were one of the greatest bangs for the Bucks. I also obtained less residual internal noise from utilizing the batteries as opposed to the phantom power modification. Those half size AA compatible 6 V batteries from Eveready were rather costly and general-purpose 9 V alkaline batteries are a lot less money. So, the simple modification to utilize two 9 V batteries is much less costly for the batteries. Even though it makes those little plastic boxes a little larger by having the external 9 V battery clips on either side of the plastic box. They sound even more incredible when you can deliver more than 1.5 V from a single AA battery. And they won't blow up. I've never had one fail yet in 20 years.

    I love those things!
    Mx. Remy Ann David
     
  7. JoeH

    JoeH Well-Known Member

    Wow.....more info than I ever knew about these things. (I did the Mods that Boswell listed, but Remy's sound like they're worth another look-see. I still have at least two of the Radio Shack, and two of the original Crown. Maybe I'll bust up the RS versions and play around with 'em.)

    Great responses, folks!
     
  8. RemyRAD

    RemyRAD Well-Known Member

    Thanks Joe. I'm a plethora of useless information. Pretty funny about those Radio Shaft PZM's eh?
     
  9. tomu

    tomu Active Member

    Thanks everybody. I took my kit round to my friend's house, where in addition to a pretty powerful electronic organ he had a drawerful of XLR plugs courtesy of his days at Decca! We did the rewiring suggested by Boswell and Remy and got an immediate increase of at least 12dB in the recording level once the adaptor had been taken out of the equation. I say "at least" because I had the limiter on and was getting a level of -2 dB and don't know whether the limiter holds it there or 0 dB. Prior to that the same input settings were giving -12 / -14 dB. Absolutely no deterioration in sound quality.

    Didn't do the phantom power mod, as the 2 x 6v battery setup is fine for me.

    Now I just have to wait until my next gig and see how they cope with Charles Ives and Saint-Saens 3.

    Can anybody think why Tandy didn't fit XLRs in the first place?
     
  10. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    Because their usual customer had equipment with 1/4" inputs and would be annoyed to have to buy an adapter.
     
  11. tomu

    tomu Active Member

    Just recorded a string quartet concert in my local Tudor(!) church, with the mics taped vertically to the front of the front box pews - one mic either side of the aisle. Got a really splendid sound with high recording level and plenty of bite to the strings' attack, especially in the Shostakovich no 9 (quartet, not symphony), so no need to normalise. What was particularly pleasing was that, even though the mics were relatively close to the players, the ambient sound was well captured.

    Fingers crossed that the new configuration works as well with a full orchestra.
     
  12. RemyRAD

    RemyRAD Well-Known Member

    That's an interesting technique/concept. Makes me think that what you have created, technically, is something akin to PZM microphones which I still like and still utilize. There always will be more than one way to skin a cat. OMG! I love kitties and I certainly miss mine. What fabulous little kitty people they were. I'm thinking about getting a new kitty more than I'm thinking about a new piece of equipment. It's the only love you can buy.

    RIP Cleo & Pookie because I can't without them
    Mx. Remy Ann David
     
  13. JoeH

    JoeH Well-Known Member

    I'll bet that sounds pretty good!

    At the risk of being a spoil-sport, I'd be concerned about recording an orchestra this way. (Quartets are ONE thing...a full-out orchestra is quite another! :cool:)

    You may get a lot of whatever is right in front of the mics, and likely more detail from the nearest instruments than the rest of the orch. Your "near" instruments may force you to gain-ride based on a skewed level.

    For mic'ing an orch with just a stereo pair, you should have some height on the mic array, ideally directly above the conductors head (5-10 feet or so, if you have the right kind of stand or can fly them), to capture it the way he/she hears it.

    You could also try making a variant of the Jecklin disc, then put it on a stand, front and center (again, as high as you can get it), and see what THAT sounds like.....

    Good luck; and interested in hearing what you get!
     
  14. tomu

    tomu Active Member

    These were recorded with PZMs. First the Quartet with the mics on the front of the box pews. This is just the last few minutes of the piece:-

    (Expired Link Removed)

    and then then the last movement of Sibelius 2nd Symphony. For orchestral recordings I tape the mics to the front of the balcony that runs across the back of the church (most amateur orchestra concerts are given in churches!) about 12 feet above floor level. You're quite right JoeH - the mics have to be back from the band or the balance would be totally screwed. Health and Safety rules and regs mean I can't put a stand in the central aisle, so this is the best Plan B. This was recorded with the old configuration, using adapters with inbuilt transformers, to fit the mics to the DR-100, and so needed normalising. Still, it gives you some idea.

    (Expired Link Removed)

    Files have been converted from WAV to MP3; I don't know what Dropbox will do for the overall scheme of things.

    In case you're interested, I'm the bass trombone in the Sibelius. Talk about multi-tasking!
     
  15. JoeH

    JoeH Well-Known Member

    I like the quartet recording! Sounds wayyyy better than it has any right to with just 2 PZMs. I'm not a PZM hater like some folks, but I never expect much from them, and am always surprised when they sound this good. Actually, I've revived an old pair of Crown (original) PZMs and am re-using them as needed inside some pianos in larger ensembles, mainly for detail/touch-up. They still sound good.

    On the orchestra recording, though, I have to be honest and say it sounds a bit too distant and watery for my taste; not enough detail, but I understand what you're dealing with, in terms of position, levels, etc.


    I'm bummed to hear you're getting grief about mic placement. That old standby about "health/safety" issues is just total BS, in my opinion. I"ve often stood my ground at the 11th hour with a conductor or stage manager, and said: "It's your money. Do you want it recorded properly, or NOT?"

    Very often, it's a small(minded) person with a napoleonic complex (or simply doesn't understand the process) who didn't get the memo that a professional recording is happening along with the concert, and balks at the mere sight of a tall mic stand in the middle of the performance area. I don't think twice about it now, after over 25 years of doing it. THAT's where it goes, period. We'll lower it for picture-taking beforehand, but in 99% of the church aisles where we've set up, the footprint is small enough that technically, it's not blocking ANYONE's egress. We tape down all wires so there's no tripping hazard, and we'll often mark the base area with white gaffer tape, sometimes even protecting it with kneelers so no one trips or bumps into it.

    Besides, it's not permanent, and as long as people can get through, I think you're being snowed. (And if it's a recording session and not a concert; don't even try to stop me! ;-)

    In most cases with us, the hall/church is being rented by the client, and when push comes to shove, the client takes responsibility for ticket-taking, ushers, basic straging & setup; chairs, stand placement, etc., while the venue is accountable only for general things, like no fires, roof leaks, explosions, etc.

    I've found that as long as everyone is nice up front, uses common sense and wants it all to go as smoothly as possible, we're in and out in 4-5 hrs total, and no one's the poorer for it. smoke
     
  16. tomu

    tomu Active Member

    Glad you like the quartet JoeH. I'm not a stringy person, really, but the complete performance of the Shostakovich was a revelation to me.

    As far as the Sibelius is concerned, I agree about the lack of instrumental detail. You ought to hear the sound in the church itself though - it's got appalling acoustics, and I'm glad to be in the band and not the audience! I improve matters somewhat by changing the pick-up pattern, as the little Tandy manual suggests, by fixing a strip of carpet along the top and outer edges of the mics. A full house helps too. Still, as the church is one of four (Matthew, Mark, Luke and John) built in London to commemorate the end of the Napoleonic wars and not to accommodate a symphony orchestra, I don't suppose I should complain too much. I did once play a concert in the Madeleine in Paris, where there was a reverberation time of at least 15 secs, and the old, pre-domed, Royal Albert Hall was once described as the only place where some composers would get to hear their music for a second time.

    In an earlier venue I was able to use the pretty conventional system of a crossed pair of Sennheisers (originally feeding into a Revox A77!), but we lost that church. It is also pretty amazing how many audience members did contrive to walk into a stand, notwithstanding tape, borrowed traffic cones... and it's frustrating to watch that happen whilst sitting at the back of the orchestra.

    A very important consideration in central London is shipping too much ironmongery around without a car. And given that a) there is precious little convenient parking space and b) I wouldn't be able to have a post-performance-pint if I did drive, I will stick with what I currently use and travel on the good old red bus.:smile:
     
  17. RemyRAD

    RemyRAD Well-Known Member

    Ha! So I nailed it or rather taped it down. Yes, putting those PZM's on the back of the front of the pews would provide adequate surface area for that low-end response.

    From the rear balcony in the back, those PZM's did provide for a nice stereo ambient recording without any real true directionality. Just a beautiful wash of stereo ambience. In a situation such as that, if one had the opportunity to utilize a dual capsule, figure of 8 condenser microphone in combination with a middle/forward facing shotgun condenser microphone, a more direct sense of intimacy may be attainable, utilizing MS. It might get you closer but the stereo effect would still be one of mostly ambience. Still, it's beautiful to listen to. So it's still 100% enjoyable.

    3-4 m tall collapsible aluminum stands are what most of us use and when collapsed, for travel, they are only about 1 m in length. And I might add extremely light weight with their tripod bases. I used to take a pair out with me along with a portable VHS video recorder and a Sony PCM-F1, a couple of microphones and 200 feet of cable on my motorcycle. And that was back in 1983/84 when I think I was the world's only digital, 2 track, 2 wheel remote bike. Of course we cannot forget the large clunky KOSS Pro4 Double A's. Thankfully one didn't need more than 2 VHS tapes either. And yeah, I also used to utilize my REVOX A 77's. Those were way more portable than my Scully 280 B in a portable cabinet.

    You mean the good old double-decker red buses?
    Mx. Remy Ann David
     
  18. tomu

    tomu Active Member

    Ho hum. There's lots of kit that would be nice from a recording aspect, but, even though I'm impressed by the amount of gear you managed to get onto your motorbike, I notice that it doesn't include a trombone (try playing that with 'phones on) or a concert wardrobe! Glad that the Sibelius gave pleasure; it's one of my favourites to play. Just check with anybody in the National SO or the Philly band and I bet that even a hardened pro will agree.

    Yes, I do mean the red double-deckers. They have been brought up-to-date so that they now accommodate wheelchairs and baby-buggies, but the colour remains the same. A couple of tourist, sorry "Heritage", routes still have some hop on/off Routemasters running. Route 9 is one http://en.wikipedia.org/wiki/London_Buses_route_9_(Heritage) and it goes past the Royal Albert Hall, where your St Louis Symphony is playing one of the BBC Proms this year.:smile:
     
  19. RemyRAD

    RemyRAD Well-Known Member

    A couple of my parents family friends were the principal bass and cello instrumentalists in the Detroit & Baltimore Symphony Orchestra's. The bass player used to get his huge double bass into a VW beetle back in the 1960s. Mario was the cellist and he had one of those tiny, I think Italian automobiles, where the only door was the front door containing the steering wheel and he used to get his cello into that automobile LOL. These were totally amazing feats with these tiny tires and huge instruments. John Matthews the bass player, whose wife was the principal harpsichordist for the BSO used to transport her full-sized, and double manual custom-made harpsichords into a VW bus which was also a tight squeeze. I loved John Matthews because he was also an audiophile. He sold me my first pair of studio condenser microphones which were the Syncron AU7A's, which were the first American made FET Neumann imitations. He also sold me a Lesher tube reel to reel, 10.5 inch reel capable audio recorder. Professor Lesher had been a mathematics professor at the University of Michigan back in the 1950s/60s. I still have those collectibles to this day, more than 40 years later. It's a shame though as I'm going to have to sell the Lesher recorder as I no longer have the space to keep it. John never used it much and neither did I so it's nearly a museum piece in nearly unused condition. It's certainly a blast from the past. Years ago I got rid of my Ampex 350's when I got my Scully's. I also don't have my Presto 800 any longer which was designed and built by the forerunners who built the first Scully's for Larry Scully.

    Just a little more equipment trivia
    Mx. Remy Ann David
     
  20. tomu

    tomu Active Member

    Well, that's telling me! Sounds like your friend's Italian job was an Isetta, the original bubble car. I remember that one of my tuba partners deliberately chose to buy a Mini so that he couldn't get roped into giving other folk a lift home after concerts. Tubas, double basses and harps are instruments for which you also ideally need a driving licence.

    Carting harpsichords around sounds a decidedly dodgy business; retuning them in the concert hall must have been a nightmare.

    It would be interesting to hoist my A77 down from the top shelf in the cupboard, see whether I can still remember how to load the tapes and whether there is anything still on any of them. Perhaps next year...

    tom
    diddlydoo
     
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