Hallo allemaal,
Mijn naam is Edwin Heesbeen, 29 jaar en geluidstecnicus van beroep.
Ik heb jullie discussie over de Behrinnger Ultracurve gelezen intressante gespreksstof.
De Ultra Curve is een apparaat wat ik persoonlijk nooit zal gebruiken om een aantal simpelle redenen.
De headroom van dat ding is 0.0000, het uitgangs signal van een beetje mengtafel is al dusdanig hoog dat de Ultra Curve in vervorming treed.
De D/A convertor die er gebruikt wordt vind ik zeer maar dan ook zeer slecht, met dynamische klanken hoor je hem rekenen.
Het enige wat redelijk werkt is de speqtrum analizer, met pink noise sturing.
Maar wat als ik nu eens zeg dat ELKE graphic eq tussen een systeem, of dat nu een p.a. of hifi is juist negatieve effecten heeft??
Ik ben in de 11 jaar dat ik nu proffesioneel technicus ben al in heel wat zalen en hallen tenten geweest, en daar ook de nodige aucoustic problemen voor de kiezen gehad heb.
En ook ik HAD een graphic eq in mijn rekje zitten een BSS FSC-960, een dure jongen.
En toch elke keer als ik een correctie deed gebeurde er vreende dingen met het geluidsbeeld, ik kreeg niet wat ik deed.
Onlags ben ik er achter gekomen waarom.
Kijk eens naar het plaatje hieronder, dat is wat een eq doet met jou geluid, hier hoort een uitleg bij die ik onder het plaatje heb gezet.
Jammer genoeg in het engels, ik had geen zin om heel zo'n verhaal; te gaan vertalen.
Veel maar dan ook echt veel beter is een bv 4 delig parametric eq, omdat deze een lage q factor heeft en veel nauwkeuriger werkt.
IK WEET HET, HET EEN potjandriedubbeltjesIN LANG VERHAAL, MEER ECHT DE MOEITE WAARD OM TE LEZEN!!!!!!!!!!
Dit is wat een Graphic eq doet met jou geluid.
Frequency response of a 9 band EQ.
Imagine 31 bands instead of 9...
Uitleg waarom!!!!!
Maintaining Sound Integrity
In our quest for superiour sound quality we repeatedly stumble over shortcomings in sound equipment. Since a chain is only as strong as its weakest link, every device in the audio chain has to be of undoubtful quality, to maintain maximum possible sound purity.
Unfortunately, as our tests often reveal, lots of wellknown and well accepted mixers, amps, and equalizers don't meet the necessary quality standards. Sometimes, the outcome is really shocking. There is no doubt that the more expensive models often show better results, but this is no hard rule. Even some very expensive models of established brands would prove very dissapointing as well.
However, we discovered a rule of thumb which is technically quite logical, but unfortunately far from common practice:
Simple (pure) solutions generally yield the best results.
Complicated tone-controls such as EQ's as well as crossovers showed the worst results. Therefore, we will try to make our point using one example, but we realize that a lot of good sound engineers will raise their eyebrows reading...
The 31 band Equalizer:
Present in every PA-system, as monitor anti-feedback tool and as FOH equalizer. We will stick to the FOH application. Why is a 31 band EQ present in a FOH chain?
1, Because decades ago microphones as well as loudspeakers had a far from perfect frequency response. Heavey EQ-ing was necessary to compensate for this.
Ok, once upon a time that was the case. Now it isn't (or it shouldn't be...)
2, Because an EQ is necessary to compensate for room characteristics.
Not ok, a 31 band EQ is probably the worst choice for this task!
3, Because everyone has one!
True!
Let's look closer to the above three answers:
1, Nowadays, the frequency response of microphones and speakers can be excellent, if you buy the proper ones.
Tone controls in your mixer will be fully adequate to deal with the corrections necessary. If they don't, something has to be disposed of, hopefully it's just your mike...
2, Room characteristics can emphasize or reduce higher or lower frequencies, depending on the used materials and the presence of more or less people, furniture, curtains etc.. Room equalizing is best done using wideband filters, like the shelving tone controls on a old fashioned mixer. Sharp high-Q dips and peaks in the room response are always the result of interfering room reflections. These dips and peaks will be extremely different for every listening spot. A carefully worked out 31 band EQ setting may be ok for one particular spot, but will be a dramatically wrong setting for other spots.
3, Correct, everyone has one. So what? Let's investigate what a EQ does do:
As you see on the above graph, a graphic EQ is actually quite a lot of narrow band filters, each of which can be boosted or cut. Imagine when four adjacent bands are boosted; the result is not a smooth four band area boost, but the boosted area shows 4 peaks and three dips in between. Far from ideal. The same -however inverted- problems occur when the EQ is used to cut certain frequency bands.
There are designers that tackle this problem by lowering the Q, so that adjacent filters blend into each other. Allthough, this generates a new problem; the interference between adjacent filters will have the effect that the amount of one filter is influenced by the setting of its neighbours. In other words, the scale of the slider will be seriously incorrect. This kind of graphic EQ is visually incorrect; what you see is not what you get...
But the worst is still to come; an electronic filter is not phase-linear. Phase shifts below and above the centre frequency of every EQ filter. The higher the Q (31 band EQ) the more phase shift will occur. Every band that boost or cuts adds its phase distortion to the end result.
Just as you think it can't get worse; it can! Steep filters have another flaw; the ringing effect. A high Q bandfilter (an EQ stage) uses input energy to slowly get into resonance, and when the input signal vanishes, the bandfilter will use the stored energy to resonate a little further. To illustrate this just take an empty beer bottle; blow over the top to get the whooo resonant sound of the bottle. You will notice that the tone will slowly rise in volume and when you stop blowing it will slowly die out. It is impossible to start and stop this resonant tone abruptly.
Well, the electronic equivalent -the 31 band EQ- shows the same problem 31 times...
Analizing the 31-band EQ makes you wonder how it is possible that it's output still produces something that resembles the original signal. Especially when you notice the following; every EQ stage uses at least one Op-Amp (IC-amplifier stage). Then there's an input stage and an output buffer necessary to complete the job. There are at least 33 op-amps involved in a basic EQ. And every op-amp adds its own noise and smeer to the end result. Because besides handy and clever little electronic devices, op-amps are also imperfect. Their architecture resembles that of an audio power stage, with most of its problems. Noise, cross-over distortion, transient intermodulation (TIM distortion), they all appear in an op-amp. That's why we have a motto: Op-amps are super, but use as few as possible in the signal path...
Still seeking for the best sound quality? Here's what you could (or should) do:
Use short signal paths; avoid unnecessary devices. Solve problems at the source, don't mask them with an extra device.
Avoid steep filters as much as possible. Use low-Q tone controls. Even a handy single band parametric tone control needs many more op-amps than a simple hi/hi-mid/low-mid/low tone control. Bypass tone control sections whenever possible.
Use excellent microphones and speakers. They will solve a lot of problems before they even become a problem.
The more complicated a device (more op-amps, steep filters), the more money you have to spend to maintain signal integrity. A good 31 band EQ needs extremely high quality op-amps, impossibly accurate capacitors, and a superb design, and still it will be a box full of compromises. And don't think a digital EQ is better. The worst EQ's we worked with were digital! So invest serious money if you need to buy that 31-band EQ! Only then it will hold up with the rest of a high quality, straightforward PA-system.
It is no coincidence that the above philosophy is quite similar to the one used by High End stereo designers. Less is more (quality). Ok, we know that a live stage performance cannot be compared 1 to 1 with listening to your high end stereo, there are a lot of extra challenges to meet. But when you look for best audio integrity in your PA, the same physics are valid.
The above is completely rubbish if you use a lousy PA system; you would welcome the possibilities your EQ offers to "solve" some of the peaks and notches of your PA. This setting would be used as a doubtful preset to start from...
But with the sonic performance of a System One Audio PA you will mercylessly reveal all weak links in your audio chain. So bypass all unnecessary stages; time to enjoy music in its purest form!
Groet
Edwin
