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Tag: measurement

To bass manage or not

That is the question. A serious one indeed. As you might recall, we purchased a complete JBL LSR 6300 series stereo and surround monitoring into 3 of our studios. Since then we always try to reach the best settings so that we can really trust the whole system. This might seem like an easy task, as we already has pretty well treated studios acoustically, but still, when you dive into this topic, believe me, you’re going to spend crazy amount of time adjusting, measuring and tweaking. At every stage, you’ll be surprised how much work is going into some very tiny detail which makes the whole system more smooth, more punchy and more balanced, and still, there’s still room for improvement. As you discover the next step, you realise that your knowledge is lacking, so you dive even deeper, discover new things, and this circle just goes on and on and on.

Right now, we are at a stage where we seriously considering to use bass management, but not only in surround. We try to achieve a so perfect state that even the stereo system can be a 2.1 “bass managed” system. Why is it so important to use the sub? Because we deal with every aspect of post production daily, and a huge part of this is music. Music in almost every genre you can possibly imagine. With this in mind, I would like to have systems that properly “tell” me what’s going on in every area from 20Hz up to the human hearing limit. Of course the hard part is that it’s not that easy to properly integrate the sub so it is truly supplement the stereo and the surround system (bass management) and still have a powerful LFE in surround when we need it. Frankly it’s somewhat good that I didn’t know this much about this topic, because if I did know this, I would probably tried to make it someone else’s responsibility. The problem is my deep utter obsession, which doesn’t let me leave things alone. This obsession leads to long and thorough research, practice and many failures and re-starts. But the reward at the end is well worth this long and gruelling journey. I’ve learnt lots of things about room acoustics, acoustic treatment, loudspeakers, positioning, adjusting, testing, and measuring things with Smaart (phase, magnitude and how to treat things).

Although a not so sophisticated simple SPL measurement can make your system better, if you’re serious about a proper monitoring system, some kind of more sophisticated measurement system is a must. We chose Smaart as we have experience with it. My live sound experience was a huge help in this area. This is almost like tuning a PA system, but in a much more controlled environment, at lower volume, and generally you have to be more precise. But the fundamentals are the same. First we started with simple RTA measurements to find the problem spots. Because our rooms are properly treated acoustically, we only had one or two, but I really wanted to get rid of them. We had some problems in the 60Hz area (a peak) a dip in the 100Hz area and a wider peak at around 170Hz. Up from that point, everything was pretty smooth, I would say it’s like a perfect studio. After identifying the problematic areas, we switched to Transfer function measurement to check phase/magnitude relations, adjust angles and positions with the help of a laser measure. While it might sound a bit to geeky to make a fuss about a few centimetres, believe me, it has a huge impact on sound. After carefully adjusting every position and angle, the phase response of the system improved considerably. Of course, listening to sweeps and pink noise is not really an enjoyable thing, so at this point I switched to some very well known test material. My “Soundcheck” playlist contain many genres of selected songs and albums which I know intimately, heard them on many systems both at low and high SPL.

plot1

The music listening test proved that our efforts improved the whole system. Only adjusting the angles and playing with the positions (only by a few centimetres) made the stereo and surround much more defined. When using the stereo system, we gained a very strong and convincing phantom centre, all the tiny panorama changes become very obvious, and the system suddenly properly painted a 3 dimensional sonic field with detailed effects. Improving the phase relations also made the transient response much better.

Huge part of these measurements depend on the data you gather through Smaart, so you must be very familiar with what you see on the screen. It’s not enough to measure and capture data, you have to understand what you see, and, obviously, always check the adjustment with music, use your ears. It’s very important to remember that all the scientific measurements are there to help you, but at the end of the day, you simply cannot trust your life on these data.

phaseplot

Next we tried to eliminate all the frequency peaks and dips. We used the JBL’s room correction feature to get rid of the lowest problems (the 60Hz area). Constantly measuring with Smaart while adjusting the dip switches and the rotaries. One friendly advise: wear some ear protection while doing these adjustments. It is very tiring to listen to pink noise at this level for long time, and it is completely unnecessary while you’re adjusting the system. Spare your ears stamina for the actual listening tests. The room correction perfectly treated our first and biggest problem. The next two problem areas were treated with some minor EQ adjustment. These peaks and dips were so tiny (within 3–5dB) that we found that this is the easiest way to deal with them. After smoothing out the whole system I double checked the levels both with the stereo and the surround system and made some adjustment to be as exact as possible. As I said before, leave enough time to do these things. This process took more than 8 hours of work! After this period, no matter how cleverly you try to protect your ears, you need rest. Seriously. Don’t make huge decisions at the very end of a day like this.

The last day

After a good night sleep, it’s time to check what we did with actual test material. To really test the system, in my opinion you need dialogue, effects (mixed), music (many genres), and full film mix. If your system is properly adjusted, all the different material will sound as it should. Original film mixes will sound punchy with great dynamic range, compressed modern music will sound, well, compressed, original score music will have real 3d depth, and in surround you should feel that the sound really give that additional depth of field. When I was listening to carefully selected test material, I tried to focus on the well-known properties of the test music, I gladly found that the system is better than ever. These measurements helped us to re-adjust the whole stereo and surround monitoring to make it a proper, trustable system.

While the listening test made every one of us very happy, the last and most important test was awaited for us, real work on the system, and then check how our new “perfect” system translates to the real World! We produce material for TV, Radio, Cinema and Web. So the next few mixes become our reference. Written on CDs and DVDs, copied to pen drives and hard disks and checked as many different places as we could.
Finally, our last tests showed that this JBL system translates amazingly well! Better than I assumed. So for now, we’ve been using the bass managed 2.1 system, and the bass managed 5.1 system ever since, and very happy with it.

I know that this system still has room for improvement, but unfortunately that would require much more time. This is the way it goes: now we have really tiny error spots which would take incredible amount of time to solve, or at least improve a bit. But right now, this system serve us so well, translate so perfectly that we all think this is not only good enough, but a joy to work on.
Please be aware of the difficulties when implementing a bass managed system. It’s far from easy, and you can easily make your system more misleading if you’re not careful. If you don’t have ample time to do the measurements and adjustments properly, or you don’t have the necessary knowledge or equipment to do so, hire a professional. It might cost you some money, but in my opinion it would cost much more if your mixes won’t translate well, and every director, conductor and musician would be miserably surprised to hear the final mix at other places. Invest the time and energy, or the money into this process, it’s worth.

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Spot serious problems with gadgets

While the World is changing rapidly you can still hear the same old story again and again that you need expensive professional equipment for everything worth mentioning. Well, I know that there are situations where you definitely need the highest quality equipment in order to be able to do the job properly, but there are situations where the gadgets can help you, even solve problems that needed serious equipment few years before.

Trust your ears, but test your beliefs with equipment

In our broadcast studio we have different types of monitors from small to fairly big, so anyone can check the mix on a variety of references. I think it is vital as we mix here live broadcast shows for TV and Radio, and do a fair bit of post production here too, from editing to final mix. So, versatility is what we need. But monitoring, being our sonic microscope, must be as accurate as possible, or else the mixes won’t translate well to the ether.

Few of us thought that we have a spot on small and near-field monitoring, but we felt that the mains are off for some reason. With those being “off” I mean listening to them was always made me feel uncomfortable with the mix. At first obviously I thought it is a mix problem, but then I started to think that we have problem with our mains as all the smaller speakers confirmed that I have a proper mix, which by the way translates very well. So I decided that we need to do something. The problem is though, it is very hard to change anything in a place which is used by many engineers, many of them being guests from different places, and most of them seems to like the monitoring just as it is.

Fortunately it turned out that I’m not the only one who felt that something is not right. So in a little downtime we decided to try to make some corrections. Next problem, we don’t have the necessary equipment available at the moment to make proper measurements…but, maybe, because we have an iPad Mini and and iPhone (call me an Applefan :)). So, let’s try it with what we have and we’ll see soon enough if it’s possible to achieve anything.

iGadgets and apps for the audio geeks

The first app that helped us in our endeavours is Studiosixdigital’s AudioTools with the Smaart module inside. Not only you have a generator in it, but have a very neat dual-window setup to analyse the data.

smaart module

As we didn’t have any other viable option, the built-mic had been used during he measurements. To my surprise it was fairly accurate. Obviously it is not as good or professional as a multi thousand dollar equipment, but good enough to spot problems and try to make corrections based on the data it provides. The little iPad app is fast enough on the new mini, and the fact that you can save different measurements and compare them makes the whole process a very enjoyable and productive effort.

measurements

Between the different measurements we tested the changes with a selection of classical, jazz and rock music which was right there on the iPad, only a gesture away after the current measure. From the start, we used different measurements to see what is our problem in the room. First things first, all the speakers calibrated to the same level, so if you switch to a different speaker set, you’ll hear the material at the very same level.

Just to make sure we are not fooling ourselves the levels were checked again. After this we were ready to jump in and make some more serious measurements. Tried sweeps and pink noise. Pink noise proved to be more useful in this case so we continued to make measurements with that. In a minute we spotted two problems, one peak at 160Hz and a quite big dip at 80Hz. According to the original room modes these frequencies are problematic in this room from the start, but treatment has been made to correct these errors. However, it turned out that the 80Hz dip is caused by an unfortunate over-treatment with tuned traps. At least now we know what to change in order to get a more flat response.

We also adjusted the speaker angles and checked the first reflection points, those still need a little work. For these things we also used some app. For the first reflection checking we simply used the built-in iPhone camera to precisely check the positions, and for the angle adjustments I love the SpeakerAngle app where you can reset your null position, hold or put your iPhone on the top of the speakers and start turning the speaker. When you reach the proper angle, the red box turns into green. In the box you can see the actual value too, but this colour change is very helpful during the process. With this utterly clever little app you can easily tune the angle of your stereo or even surround set of speakers within a minute.

speakerangleapp

We played about two hours and frankly managed to improve the monitoring in the room so much that even an untrained ear would spot the difference in a before-after game. Does this mean we don’t need expensive measuring equipment any more? Obviously no. For absolutely precise serious measurement you’ll still need high-quality equipment which is really accurate. Long-term decisions should be made after careful analysis has been made based on accurate data, and for this, you still need the expensive instruments. But the point is that with some clever gadget and a few apps you can spot and correct some errors very rapidly without spending huge amount of money.

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