Dolby? dbx? Which is best? What do you want to know?
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Thursday April 20, 2023
David Mellor
David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of Adventures In Audio.
@ratscoot: I had a Technics tape deck with Dolby B, C and DBX. The latter gave the best sound. Downside is that a tape that’s recorded with DBX can’t be played on a system without DBX, it sounds weird. And also very few tape decks/car stereo devices had DBX noise reduction.
@gregorykellerman3876: After a quick perusal I don't see that anyone mentioned the dbx 3bx, I used it extensively to increase the dynamic range of vinyl back in the day. I have a recording of Star Wars and Close Encounters by the Boston Pops, on one track it pushed the signal down 20 db and then suddenly up by 12 db. I'm guessing the total range must've been about 90 db. If you weren't expecting the sudden change you DID jump! :-)
@SO_DIGITAL: How about DNR, Dynamic Noise Reduction? LM1894 DNR System. Any good?
@AudioMasterclass replies to @SO_DIGITAL: DNR was single-ended and worked only on playback. Perhaps it was a useful compromise for some but for me I could only accept a system that encoded then decoded. Having said that, modern single-ended systems, like Cedar, can work amazingly well. DM
@akaFrits1: A bit obscure noise reduction system was DNR by Philips: Dynamic Noise Reduction. It was a relatively simple one that didn’t require any coding on the recording. It just reduced high frequencies at (almost) silent parts of the music, based on the idea that at those parts your ability to hear high frequencies was worse anyway. It would reduce the tape noise by approximately 10dB and was used on cassette decks like the N2510. It did a decent job, within it’s limitations.
@AudioMasterclass replies to @akaFrits1: An early attempt at a single-ended noise reduction system. It was never going to work perfectly. Some people, including me, thought that single-ended noise reduction would never really work, but then along came CEDAR https://www.cedar-audio.com/ DM
@fernandouribe2644: I rec on Dolby b and play on Dolby c, i think very good results , with nakamichi high com II it's very impressive. What do You think about this
@AudioMasterclass replies to @fernandouribe2644: If Ray Dolby were alive today he'd be spinning in his grave. DM
@jetphone1974: Does Dolby SR actually fight against the principle of saturation?
@graemejwsmith: dbx is interesting because it can still "improve" the dynamic range of some vinyl - even though it was not recorded with the encoding. And some - where the frequencies recorded don't fit "the model" it doesn't do anything meaningful for - or even "shifts" the frequency levels around in unintended ways.
@Wised1000 replies to @graemejwsmith: Well not really, dbx noise reduction didnt expand dynamic range that wasn't there already. DBX expanders did. The theoreticl signal to noise of the system was greater than most readily available vinyl (45 RPM audiophile recordings had about the same). however it could easily copy every nuance of the record since it's theoretical limit was greater. If you want to learn more about the system download the Teac C3 users manual. It was one of the few cassete recorders to ever have it. It was more common on reel to reel. Masters recorded with rival the fidelity of digital 24/96.
@editingsecrets: Channel content suggestion: You lived through the transition from home recording being rare, expensive, difficult to get right, occasionally spectacular, up to today when tossing it all into a laptop DAW at home is routine.
I'd be interested in your analysis of the production used for things like Face Value, Boston's albums, etc. that were super high end home recording for the time which was transferred to a big format for major label release. The fact that they were done at home either totally hidden or part of a gee whiz marketing campaign.
Leaving out rented mansions, Bob Dylan, Bruce Springsteen, Phil Keaggy, Timbuk3 among those who mentioned that parts recorded at home made it to the final record when this was exotic.
I'm not including Prince, Glen Ballard (for Alanis), Peter Gabriel, Vangelis, or Enya since they had fully pro level studios where they lived.
Now, nobody thinks it's that unusual that Selena Gomez sang in Charlie Puth's closet for "We don't talk any more."
Some of the greatest rock music could never have happened at home, like Bowie's "Heroes," Thriller, Appetite for Destruction, Faith, Hysteria, Escape, Songs from the Big Chair. No bedroom or living room setup could have made those possible in the 80s.
How much great music has been lost without the use of a dedicated work space and team to support with arrangements, gear, coffee or tea right there.
@jfmartins1971: What about HighCom and HighComII. My Telefunken CC20 has it and it's brilliant.
@redrobbosworkshop: Always preferred Dolby B if used which was the least intrusive. However, my choice of cassette decks back in the 80s was JVC which used their own proprietary system, ANRS. Basically a clone of Dolby B but has a 'super' ANRS option which introduced HF compression and expansion similar to the later type C and S. However it suffered from horrible modulation noise.
I still have a good collection of decks today and like to record to tape occasionally but my choice is to run a nice 3 head machine using pure chrome tape without NR. yes the noise floor is a bit high but no intermodulation and pumping issues.
@johnhricko8212: As u mentioned, s/n & dynamic range are so great, we now filter that through 'simulators': mic sims, console sims, cabinets, tubes, etc. We learned we really like compression, at least a little, and especially professionally done, recordings. The history, development, and understanding of compression, over the years, is a good lesson. (explains the "loudness wars").... (I had a 234. Go Tascam!) (...has anyone said u look a bit like Sir Paul?....)
@ralfschmoll8701: DBX is more interesting to me because I don't have any experience with it. Also would like to know your opinion about Hicom (Telcom). Tested it and never got satisfied, although the noise reduction was good.
@peters7949: In the early 1980s we toured a 3 screen video projection music/video album called “TV Fetish” by Question-mark Productions. Using a pair of synchronised high-band Umatic video recorders and a 2kW Turbosound PA.
The audio was recorded on the Umatic’s stereo analogue tracks using DBX noise reduction (can’t remember if I or II) it sounded very impressive, that said a lot of care was taken pre-equing & level setting the audio recorded to ensure optimum DBX decoding.
@editingsecrets replies to @peters7949: I would have enjoyed that. My U.S. high school in the 80s had occasional assemblies of a synchronized multi-projector slide show program with modern music, with exciting inspiring themes. I don't remember now what company came through town with those touring shows for schools. Is TV Fetish available on Youtube now? Kind of surprised your show used 3/4" + dbx, rather than timecode to drive an outboard audio deck, or another VO 5800 or whatever with digital audio through a PCM-F1.
@peters7949 replies to @peters7949: @@editingsecrets hi, it was a long time ago (1983), but I suspect that cost & complexity were the main factors. While timecode synchronisation was available: Q-lock, Maglink, Adam Smith 2600. These were expensive & required a skilled technician to set them up, whereas a 2 machine Umatic editing suite could be set up quickly & easily by the guys who created the program. Due to the production editing stile used, picture/video timing was critical; by having the audio on the main player this was always locked bang on. The two side screens showed the same image to support the main program (one screen being reversed scanned) so being within 1 frame of the main screen was perfectly acceptable.
Also the reason for the tour was to try & recoup some of the production costs, and University Student Union mid week fees were quite small at the time.
I’ve never found the whole thing on the internet, but this link is to an article about the project, although mostly about a slightly later incarnation when one of the creators made a more intimate show “Pycomobile”. It includes some of the videos.
https://goldenapplesofthesunradioshow.wordpress.com/2022/04/22/lufthanzer-girl-and-patrick-d-martin/
@editingsecrets replies to @peters7949: @@peters7949 Looking forward to reading all about it! Thanks!
@GeirBakkenVestfold: This reminds me of when I had Sanyo Super D noice reduction system. It was perfect for copying CD's. No noise and excellent dynamics the 5 first times i played back on my casettes. Then dynamics started too fall apart too quickly for my taste.
@MartinMaynard: I ran a medium size cassette duplicating plant from 70s till 2000 making a lot of the independent labels tapes like Rough Trade and all the early Oasis tapes. We often had the request not to use Dolby and this lead to some upsets which lead to complaints that the tapes sound dull. We found that people liked the tight bright found that dolby comparison added to the sound and listened to with the dolby replay switch turned off. Later on our Dolby encoder was used as an outboard compressor as an effect, great on vocals and strings.
@Seiskid: Dolby - C and S. Your thoughts on how well they both perform on WELL CALIBRATED recordings. Dolby-C is interesting because it has the anti saturation feature it applies to strong high frequency signals - but this also leads to significant mistracking if there's the slightest calibration error. Get it right and to my ears it sounds amazing, but interested in your experience.
@MrSlipstreem replies to @Seiskid: I've never had Dolby S, but I have a blueprinted, slightly modified and accurately calibrated Teac V-1050 cassette deck that's flat within 1dB from 20Hz to 20kHz with a cheap TDK FE Type I tape when using Dolby C. This tape formulation performs terribly without it, so spectral skewing is definitely working its magic on them.
@Soso-km8er: A sound comparison between Dolby A, SR and telcom C4 would be fun.
@AudioMasterclass replies to @Soso-km8er: And probably costly. But who knows what the future holds... DM
@editingsecrets replies to @Soso-km8er: @@AudioMasterclass I think you have enough pros and vintage gear collectors that if you put out a call, you could get the use of plenty of old tech for the purpose of demonstration.
@ThaVoodoo1: A Video on Dolby S would be great.
@RobertWilliams-kw5dl: I'm interested to learn more about the unwanted effects of using dbx on prosumer muktitrack tape recorders such as Fostex B,E,G18, Tascam recorders.
@AudioMasterclass replies to @RobertWilliams-kw5dl: I could go into more detail, but the main point is that narrow track widths cause excessive noise. dbx has its problems but it's better than noise. Fostex used Dolby Type C. Tascam used dbx and later Dolby Type S. DM
@octopuscorsica4839: Interesting topic. I run my cassette decks through an external hardware denoiser, a Behringer SNR 2000. Unlike Dolby and DBX, this is a single-ended system so there is nothing encoded on the tape itself. The result is quite impressive and I wouldn't go without the device anymore. Would be interesting if you could cover this type of single-ended noise reduction systems.
@MrSlipstreem replies to @octopuscorsica4839: I could be wrong, but I think that may have been based on the HUSH SSM2000 IC. They used to be readily available to the public for relative peanuts back in the late 90s. I designed and built a PCB that sits inside my 1977 JVC KD-720 cassette deck with a switch on the back to select 6, 10 or 20dB of noise reduction on top of the Dolby B the deck has already. It's nowhere near transparent in operation at higher noise reduction levels, but I'd say it's certainly good enough for recovering cherished old cassette recordings or audiobooks on tape at 6 or sometimes 10dB.
@John-381: dolby and dbx
@sam_64: A video on Dolby HX Pro would be nice too
@editingsecrets replies to @sam_64: Agreed. The description of A, B, and C is great. Operation of S and HX Pro a bit mysterious to me.
@sam_64: a comparison of Dolby B and DBX
@grantbovee: dbx
@stevenewtube: I’d be interested to know if there’s a suitable plugin to decode Dolby pro formats, A, SR and so on. I have a a bunch of 2” and a machine to transfer the recordings but no noise reduction units. I looked into this a couple of years ago but didn’t really find anything though I could have missed somethings. Any thoughts for your up coming video ?
@AudioMasterclass replies to @stevenewtube: There are plugins that mimic Dolby Type A in record mode to provide a kind of enhancement to the signal, which is a reasonable use if you like the sound. Whether they can mimic playback I don't know but I doubt it. My thinking is that it should be possible to mimic Type A digitally. I'd start by splitting the signal into four bands like the original. Then it's a matter of compression thresholds and ratios. Getting the attack and release times to match would be tricky. What would be important though is whether the end result sounds reasonably good with no audible problems, if not exactly like a genuine Type A. SR would be a lot more difficult. Of course, there's always eBay. DM
@paulpavlou9294: Hi David, My old Nakamichi 600 tape deck has three noise suppression options which included the obligatory Dolby NR, I..M Suppression as well as MPX of which I used all because I didn’t know what I was doing back in the early eighties. Dolby works for me in my surround sound receiver or my surround sound processor otherwise it’s irrelevant to me these days. I’ve never used or had any equipment that had or used dbx in its implementation. I love you work and videos thx.
@teashea1: very interesting
@Chunksville: The pumping breathing effect on DBX was annoying especially on quick quiet to loud passages on recordings because of this I would question the relevance of the stated achievable dynamic range.
@MrSlipstreem replies to @Chunksville: Agreed. I had the same problem with a home-built DBX system based around NE571 ICs back in the early 90s. The only easy fix in the end was to reduce the 2:1 compander ratio to 1.5:1 giving me a far lower dynamic range of around 75dB, but that was still a massive improvement over no noise reduction at all. As I was only using it for my own recordings, it didn't matter that they were incompatible with everyone else.
@MichaelBeeny: Dolby B worked OK on a brand-new cassette deck. New, clean heads, everything in perfect calibration. After quite a short time, the heads ware, get dirty, different brands of tape, what do you get. -6dB @ 5 k So people turned it off. So now it still has no HF but lots of noise.
dbx in domestic form was a joke. The range was far too high. You could hear it working. Try recording a low level piano, you could hear the noise level mixed with the piano harmonics mixing together. Sounded dreadful. Ohh I almost forgotten the very audible pumping effect.
The biggest issue with Dolby B and C was that if worked well on a new deck when recorded and played back on the same deck but when tapes were played on another deck, the Dolby system NEVER tracked the same.
Add differences in tape bias, azimuth, levels and it seldom sounded good. Prerecorded cassettes with Dolby B always sounded very lacking in HF.
@florianm3170 replies to @MichaelBeeny: Well, that's the difference between a normal user and an enthusiast who knows what to do to maintain and calibrate his decks. And in every user instruction book for a deck there is a recommendation to regularly clean the tape heads, or not? Dolby tracking was an issue as often decks were not set up correctly already in the factory (hey girls, just adjust every potentiometer to 2 o'clock) Using old , dusty, overheated (in the car) cassettes never helped much either.
@morbidmanmusic: We would sometimes record with DBX in, and then turn it off on playback for select channels.
@editingsecrets replies to @morbidmanmusic: I haven't heard of that. Why did you do that? Which instruments or voices got switched in or out?
@jhuc2869: Metal tapes on a good deck with no NR was the answer… but for the cost you might as well have bought an original copy.
@florianm3170 replies to @jhuc2869: depends if your source was a CD you'd easily beat any commercially released cassette from the record labels (excepting perhaps some small hifi-labels like MOFI)
@jhuc2869 replies to @jhuc2869: @@florianm3170 Yeah, I think there must have been some sort of gentleman’s agreement between the recording industry and tape manufacturers. The price of blank type iv tapes always sat only just below that of a pre-recorded tape. Granted on a good machine with CD as the source you could easily beat a pre-recorded tape, but for the price of the blank metal tape you were halfway to buying the CD. It’s a shame that metal tapes didn’t lend themselves to high speed dubbing or we’d have had pre-recorded titles priced somewhere between a standard formulation pre-recorded tape and a CD. Would have all been academic as MP3’s came along and blew everything to bits and we’re still dealing with the confusion to this day (evidenced by the vinyl revival).
@editingsecrets replies to @jhuc2869: @@jhuc2869 "some sort of gentleman’s agreement between the recording industry and tape manufacturer" blank tape tax actually, perhaps a good video topic here
@markcolegrove: I had a dbx II 122 when I was in college paired with a Teac cassette desk. The noise reduction was amazing but you could hear some "pumping/breathing" effects with some music. I assume the compression and expansion circuits were not a perfect mirror image of each other and that was the result. Did this plague the professional gear as well or was this just an artifact on the consumer grade stuff? And... if my diagnosis accurate or are there other reasons for the issues I heard?
@tirregius replies to @markcolegrove: Definitely an issue with DBX. I had the same artifacts that were especially annoying with very dynamic stuff like drum hits against a quiet background....
@cliffh2103: When I came into audio as a teenager in the early 80’s Dolby B was common, and C was new. Dolby C was much better, but my car decks (where I used these cassettes) were only B rated and a ‘C’ tape didn’t sound right in a ‘B’ deck. My question is what were the technical differences between the two and why weren’t they backward compatible?
@SO_DIGITAL replies to @cliffh2103: The ONLY Dolby C cassette I've ever seen in the wild was a classical album from Deutsche Grammophon
@MrSlipstreem replies to @cliffh2103: The Wiki article has the answers you seek... https://en.wikipedia.org/wiki/Dolby_noise-reduction_system The spectral skewing technique used by Dolby C (and later Dolby S) was the biggest hurdle to backwards compatibility, but it did greatly improve high frequency performance of all tape types at high signal levels, especially Type I "Normal" tapes that could give very close performance to expensive Type IV "Metal" tapes with it. Dolby C saved me a small fortune when I no longer needed to buy Type IV tapes.
@tirregius: In high-school and college in the mid-late 80s and early 90s, I was obsessed with the challenge of reproducing CD-quality sound on cassettes, etc. I had Denon equipment with Dolby B/C and a rackable DBX box... Ultimately, Dolby C was the most "lossless" NR to my ear. The insanely low noise floor with DBX was really cool, but the super aggressive compression resulted in artifacts that made it a no-go for my ear. I was disappointed, having spent so much money on my quest and coming up short. I was sure DBX was going to be the holy grail of noise reduction. Oh man was I wrong. I was totally disillusioned at one point and thought my only options were to go to big reel-to-reel high IPS tape, or stay in the digital realm which was so expensive back then ... I would usually settle on Dolby C and a touch of "Dolby Chris"🤣🤣 as I called it, where I'd boost the highs further, then take them out on playback with a very nice EQ. Every cassette I recorded also had the EQ graph showing exactly how I altered the sound for accurate playback ... looking forward to your video on that subject! Brings back so many memories (and frustrations!).
@editingsecrets replies to @tirregius: "Every cassette I recorded also had the EQ graph showing exactly how I altered the sound for accurate playback" I would've enjoyed having you as a buddy in high school!
@SO_DIGITAL replies to @tirregius: I was shocked when my Dolby HX Pro capable deck produced essentially CD-quality playback with Dolby S on plain old C-90s. Bloody hell! But, I had severe print-through problems too.
@stanguay169: There was vinyl released specially for dbx decoder owners... But i guess it failed.
@martineyles: Psychoacoustics in noise reduction. What noise reduction shares in common with lossy compression. I got a glimpse that they might have more in common than we realise, but I think there is probably much more than I realised. Also, does dolby C help give you more treble on non-metal tape. I read something about an anti saturation network but didn't really get it entirely.
@editingsecrets replies to @martineyles: "What noise reduction shares in common with lossy compression." Two different things really. Dolby and dbx boost both signal and noise when recording. Both signal and noise get a complementary reduction on playback. If equipment was perfect, the noise would be completely gone while the signal restored to its original level. By comparison, lossy compresssion throws away some of the signal, in hopes that you won't miss it because it was perceptually masked by some of the remaining signal. This change in the frequency content creates new noise and distortion. If algorithms were perfect, that additional non-signal content would be at an unnoticeably low level given the listening scenario.
@eaustin2006: If you're having to resort to any of these it's too late. You're working with a hopeless system. Give it up now and do something that has fidelity.
@AudioMasterclass replies to @eaustin2006: This wasn't an option in the heyday of cassette. The alternative was reel-to-reel, most of which wasn't much better and too costly/inconvenient for the mass market. However your point raises the question whether we can think of an equivalence between noise reduction and today's lossy compression. Are systems, i.e. the internet, hopeless because they require lossy compression to a) make streaming even possible for people with a slow connection, and b) make economic sense for the providers? Perhaps we need an internet that has fidelity, and if we need it enough perhaps one day we will get it. DM
@joesmith4443 replies to @eaustin2006: @@AudioMasterclass Please make a video on How to restore (as best as possible) dynamic range when it’s been compressed so much in digital? Thanks 🙏🏻
@AudioMasterclass replies to @eaustin2006: @@joesmith4443 I could say that this is impossible but I'd love to be proved wrong. I will say however that once we believed that it was impossible to separate instruments out of a stereo mix, and now we have iZotope RX, RipX and others that do it amazingly well. So at some point in the near future, AI will be our friend. Either that or our digital overlord. DM
@joesmith4443 replies to @eaustin2006: @@AudioMasterclass Thanks for the reply. Haha, the simple solution is to stop overproducing, limit the digital plugins and processing. I think the idea of being frugal was one advantage of the analog era. You couldn’t run the the signal too “hot” and you were limited by multitrack master tape machines. This is one of the reasons (perhaps) why many people today believe analog sounds better.
I did find a “relative” solution using a BBE maximizer but does produce artifacts. The problem also is that when the mix is slammed so much there’s a ton of noise and distortion on the track and there’s NO way to get rid of it!
The real solution comes down to how the mastering is being down, I would imagine that many sound engineers have no choice but to do what the Artists and record labels believe would sell more.
It’s just so hard to listen to mixes that are so loud and distorted that kills the benefits of digital audio. It’s equally frustrating when you like the music/artist but the record production is unlistenable.
Again, Thanks for the reply. I really learn a lot from your videos and enjoy them!
@editingsecrets replies to @eaustin2006: @@joesmith4443 "I think the idea of being frugal was one advantage of the analog era." Behind the scenes videos of Yes "Owner of a Lonely Heart" and Bowie "Heroes" reveal that the phased bass was baked into the recording from the start. Today we'd have a dozen tracks for clean, phased, reverse phased, overmodulated reverse phased, and blow up the dilithium crystals versions of the bass, through eight different amps, with any actual decision pushed off till the stems were brought in to mastering.
@sonic2000gr: No experience with dbx. Dolby B was ok, C was very sensitive and would be a problem if played on a different deck than the one recorded on. S was really good but way too late on the game, tapes were already phasing out. I have one of the last Sony decks with Dolby S here, not one of the high end models though. It's good for what it is but cannot compete in sound quality with the MD that I bought back then. I would really like to hear your experience with the various Dolby systems.
@mondoenterprises6710: This may not be the matter at hand. But broadly, I would ask, as a listener and Sony ES avr owner, What is the point of all these filters? Am I supposed to listen to stereo or multi channel movies thru them? Will they sound better if I fiddle about with them? What about the stadium, church, and jazz club settings, etc? Am I supposed to use those to listen to U2 Live so that it sounds better? Haven't all these issues already been taken care of by the engineers in the original recordings already and aren't I best set to pop the cd in and let the avr figure it out and present like it always does on its own w/o me fiddling with a bunch of presets or filters? I do notice slight or audible difference with the settings, but usually the auto mode sounds best anyway.
@marleypumpkin4917 replies to @mondoenterprises6710: U2 are 💩.
@florianm3170 replies to @mondoenterprises6710: This is not the theme here (as you said yourself). Dolby had noise reduction for cassettes, reel to reel to reduce the hiss in the tape recordings. You are talking about Dolby surround/Dolby prologic. Those are systems which reproduce multichannel sound. and you have correctly noted that for stereo recordings à la U2 from vinyl or CD you don't really need them. But if you use a DVD/Bluray U2 concert video with Dolby (or DTS for that matter) encoded multichannel sound then it does make a big difference if you are using the stereo mode or a multichannel mode. Of course you'll need to have the additional speakers set up too.
@editingsecrets replies to @mondoenterprises6710: "What about the stadium, church, and jazz club settings, etc?" All gimmicks to impress the punters in the shop. Useless or counter productive given that the original producer would have put their own choice of reverb on the original mix.
@doctortubes1: Wich one ? A ? B ? C ? C+HX ?SR ? Type l ? Type ll ? DbxDisc ? They all need the right setup to perform good.
@AudioMasterclass replies to @doctortubes1: I'm thinking B, C, S, or dbx Type I or II. I'd be happy to mention dbx for disc and if anyone has any experience good or bad that would be useful. DM