Speaker & room calibration

I was lucky enough to pick up a Behringer Ultracurve Pro DSP8024 for a mere £50 on eBay recently. It turned out to have a buggy OS version (1.2), and Behringer very kindly sent me a replacement EPROM with a new 1.3 OS on it, which works just fine. I now have it installed between my Soundcraft mixer and my Wharfedale active monitors. I used its “Auto-Q” calibration routine and put up with some quite loud pink noise to calculate a room correction curve. Because it knows the spectrum it’s generating, it assumes that what it gets back has been altered by the combination of speakers, room and microphone, so it can calculate an eq map to compensate for it. It’s quite fun to watch as it has a nice big LCD screen to display the 31 1/3 octave bands – the initial spectrum is fairly peaky, but as it iteratively applies corrections you see (and hear) it flattening out. It’s also very obvious that my monitors don’t put out much below 50Hz (it analyses down to 20Hz), but that’s to be expected from a moderately sized box with a 6.5″ driver. The results are really pretty good, sounds lovely and smooth, but the real surprise is when you’ve been listening to it for a while and you switch out the EQ – it’s really quite a shock to hear the uncorrected version. Lots of purists don’t like room correction by EQ, saying it’s better to fix the room in the first place, and also that EQ calculated like this is highly dependent on the listening position (which it is). I have a lots of bookshelves facing my speakers; they make fantastic diffusers, and I have some Universal Acoustics absorber tiles on the sloping ceiling above my listening position. The longest room mode will be fairly undamped (I’m not about to start hanging duvets around the walls!), but the resulting EQ is below 6db in either direction across the whole range – I’ve heard of rooms with 24db peaks! Anyway, after all that, it sounds lovely, and I’m happy!


I’ve had a little Behringer UB802 mixer for some time and found it very frustrating to use as a front-end to my computer system. There’s nothing particular wrong with it (clean audio, good functions, simple, reliable), it’s just not very well suited to the job, mainly because its routing is not flexible enough to be used for audio input at the same time as output. One big problem I had was that the mic I use for audio input (mainly for Skype) routed to my speakers too; a recipe for feedback and poor input level.
In order to resolve all this, I’d been contemplating a Soundcraft Compact 10 as it seemed to have much better routing options. Last week I managed to pick up the smaller Compact 4 for a mere £30 on eBay (I figured I could live without the extra size and inputs for that price). What a difference! It achieves its wonders by having an additional “recording” mix buss. It also has separate routing for monitoring. Each channel has a button that when pressed, routes that input to the recording buss and removes it from the main mix. Similarly there is a monitor button that routes it to the monitor buss. if neither are pressed, it goes to the main mix, which you can conveniently route back to the monitor mix too. Multiple mix busses are par for the course on bigger mixers, but almost nobody does it for small mixers, yet there are tons of n:2 small mixers around that are used in this role, suggesting there are a lot of frustrated users that don’t know there is a way out. As Soundcraft’s manual says:

Why don’t other manufacturers design consoles like this ?
a) Because they are out of touch ?
b) Because they are not very innovative ?
c) Because they don’t have the experience ?
d) Because they don’t listen to their users ?
Who knows 🙂

The upshot of all this is that I can route the microphone to the computer’s audio inputs without having it also appearing on the mix bus going to the monitors. As far as I can tell, this routing flexibility makes the Soundcraft about the only small mixer that’s actually designed for this role. Most seem to gloss over this routing problem, or not want to “confuse” users with the concept of an additional mix buss. As an added bonus, it has two headphone outputs that are independent of the mix output, so I can turn my speakers down without turning down my headphones. The Behringer tries to do this, but only by giving you main and monitor mix levels, but as far as I can see you never really need the main mix outputs, only the monitor mix. The only real workaround for simple n:2 mixers is to have a separate mixer for input and output, which is quite a reasonable proposition when you see the price of things like the Behringer Xenyx 502, but I’m much happier having it in one box. Behringer make bigger mixers that have more busses (I think the cheapest is the Xenyx 1222FX), but they are also bigger, more complex and more expensive – overkill for my application.
It’s also interesting to contrast the marketing. Behringer describes the 802 as having 8 inputs, which is technically true – 2 mono, 2 stereo, and a stereo return – but in reality that’s only 5 independent inputs (total of 10 input channels). Soundcraft go the other way – the Compact 4 has 5 independent inputs at a push, but you can actually squeeze 8 channels into it in total, and you can actually get 16 channels into the Compact 10. British understatement at work?
The Behringer is still a great little mixer, and I’ll miss its diminutive size, the aux send, and a couple of extra inputs (which, now I’m firmly in software-synth land, isn’t really a problem any more). Anyone want to buy my UB802?