DBX GoRack - field report

[almeriastrings]

Have mentioned these before, but last night we hit a real 'situation'. Arrived at a gig to find that the contractors who were supposed to have finished renovating and rebuilding the stage area had, in fact, only just started... and we were faced with literally bare concrete walls on all sided, a marble floor, and hard, low ceiling. It was an acoustic nightmare waiting to happen. Worse, we now jammed right at the end of a room that most closely resembled a concrete tunnel. On top of that, we had our friend Gibb Todd (from the Kerries, Celtic Connections, and who has recorded with Tim O'Brien and Alison Brown, etc) as our special guest, and Gibb does like some on-stage monitoring....

This is where you need a Plan B and I always carry what I call my "bad room box" which consists of some mics and a few other items that I have found to work really well in dire situations. I added a DBX GoRack to that box some months back, and last night it got a real work-out.

Basic setup was a single main QSC K10 and I used a QSC K8 as a floor monitor. Mixer was a QSC Touchmix 8. Two vocal mics - EV PL80a's, which are a really tight hypercardiod pattern and sound very good even in 'challenging' situations like this. The AKG D5's are also good. One instrument mic, in this case I used my 'old faithful' Shure SM94 - another mic that can work well just about anywhere. Gibb likes to DI his instruments (I had an Orchid dual active DI box set for him), but I wanted to avoid plugging mine in, so I stuck with the stand-mounted SM94 and just worked it really close.

Initially, during soundcheck, the room was ringing like a bell. The Touchmix has some very good EQ options though, and it was possible (surprisingly) to tame most of it. Even so, if anyone moved off a mic, the back wall just reflected so much sound straight at them that the beginnings of feedback were evident. OK. Out comes the little Go-Rack. I set this to dual independent channel mode, and sent the AUX 1 Monitor feed through one channel and the main feed to the K10 through the other. The only active processing was was the auto feedback suppression. This is a very simple box... the one thing it does not have that I wish it did was some indication of how many filters it is using... you can hear them latch on, but there is no actual indicator. Regardless, it was really excellent at grabbing any incipient feedback before it got going. It was very transparent too. Very clean. I had the vocal and instrument mics gated (via the Touchmix) once soundchecks were over, and performance started. That also helped. Bottom line is that the little DBX unit did a really good job. A few times when anyone moved off axis, it automatically detected and notched that feedback right out far more rapidly that I could have managed manually, and it did it without carving huge chunks of adjacent frequencies away with it (the notches are super-tight). It was not any easy room... but at the end, everyone was happy and the sound was good (considering the difficulties). I was really glad to have that little box with me and I can genuinely recommend it as something to consider as for the silly low price these things are, they are an incredibly useful addition to anyone's "bad room" kit.

[lloving]

Thanks for a great write up. One question: How does the DBX GoRack compare to the DBX AFS2 feature built into the Soundcraft Ui Series mixers? Our little group find our "backs to the wall" a lot and need all the help we can get with feedback suppression.

[almeriastrings]

Very similar. You do have more control on the AFS-2 as built into the Ui, as you can set fixed + "live" filters independently, and you see a readout of the frequencies being notched out. The basic algorithm is the same. They are both very effective. The standalone 19" rack AFS2 has even more filters and a lot more options, but is substantially more costly and bulky, of course. I'd say all three - the GoRack, the AFS-2 as provided in the Ui's and the rack mount model all work well and really make a difference. They are all very transparent and (to my ears) you don't even notice they are there and doing their job (except for the dramatic reduction in feedback). For comparison:

[TonyP]

Yes great write up. But to us type A personality wannabe sound guys it read like a horror tale. One only the person having to deal with the nightmare could take in at a glance. And the rest of the band is looking at me with "what's wrong? isn't this a great place to play!" and all I can see is a sonic cluster looming.

One of the biggest leaps fwd for me was the addition of dbx AFS to my kit because I can't function without some kind of monitors. And that you can buy one in a little stand alone AFS for $50 is just amazing. It would be a little disconcerting to not have some kind of indication of how many "slots" you have left. But for $50 how can you not be happy? I do have to say though the AFS built into the inputs of the Line6 m20d are completely seamless and don't seem to "hunt" like dbx. It is fantastic there are so many affordable options that WORK!

[almeriastrings]

The AFS in the M20D is hugely powerful as it is channel specific. It is like having a whole bunch of totally independent 19" rack AFS units with you....rather than just a couple across the monitors or mains. That said, there are only two main settings on the M20D - vocal or 'universal' and they are global, whereas the lowly GoRack does offer three different notch widths and sensitivities. All of these are good, and they each have pros and cons. Once you get to know them, they are all capable of making a huge difference with relative ease. I know some kind of sneer at them... but then, they did at the printing press and mechanized loom! For me, they work, and in really difficult venues, save a lot of frustration!

[Charlieshafer]

Nice to hear! I have to admit I like small units like this more than piling on a zillion features into mixers. Not that all those features aren't great, but (take your pick here) I'm either a guy who likes things really simple, or I'm not bright enough to figure out all the added gizmos on the new mixers. A box like this is perfect for someone like me: when I don't need it, it's out of sight and when I do need it, I'm actually physically plugging it in, so I know it's in the food chain.

I'll grab a couple. BTW, when it's working, does it have any effect on slight clipping at all, or just all feedback suppression?

[TonyP]

It's all about feedback, but I wouldn't be surprised if the clipping is effected because it often causes feedback.

I'm totally with you about simplicity. So for me it's way easier to carry one box(mixer) than patch stuff in. I had to do the patching before because that's all that was available. But now I've gone digital, it would be a big let down to have to go back.

The huge variable is software. I'm not a fan of tiny screens and buttons that do 15 different things, I didn't grow up with it so it just bounces of my Teflon brain. So I bought the lowest dbx DriveRack that I could plug a laptop into it, the 260. Being able to see on a lap top screen instead of the little screen on the unit was amazing but you didn't just intuitively navigate it because it was geared toward the sound engineer and that one rack space unit replaced probably 10 or 15 standalone units. And the GUI was not made for noobs. After some guidance I learned it and as time went on I realized 90% of what it did, I didn't need. And I learned how to read what the little screen could could tell.

But bottom line to me is its far easier to leave the AFS in the m20D active on global, then have something change after we've started playing(noisy crowd, or a member who was sandbagging in the sound check and now is Pete Townsend, Etc) and try to patch it in later. It is not a destructive "process", it's totally dormant until something goes sideways. YYMV, NFI blah blah.

[almeriastrings]

If you are using the M20D, Tony, you probably don't need a GoRack. I don't use any external AFS when using that mixer. Same with a Soundcraft Ui - they have good AFS built in if you need it. The main value is for those mixers that don't - the QSC Touchmix 8 and 16 (the new TM32 does have its own AFS), the Behringer X-Air series or with a small analog console such as the A&H ZED's. Here, the GoRack really adds something useful. It does not do anything in respect of clipping. It simply sets narrow filters if feedback is detected. There is a separate compressor included (that you can have either on or off and can do a 'one knob' type adjustment) but it is not a limiter and most good quality active speakers these days have their own internal DSP and limiting (i.e., QSC K series). Indeed, you also have a limiter capability in the M20D itself if you need it.

The main advantage of the GoRack is that it is small, cheap (I have seen them for as little as $29.55 which is completely crazy), it is very fast and easy to set up and use, and it sounds really excellent. It does not audibly degrade the signal passing through. So if you are using, say, a Touchmix or A&H ZED it is a great way to add some high quality AFS for very little money.

[TonyP]

Yup, sorry, I wasn't trying to hyjack.

Being a dbx AFS fan, some form of AFS was a major concern when I decided to go digital. If I didn't have AFS already the GoRack would be a must have.

[fiddleround]

Almeriastrings: Thanks for the info. At that price (or slightly more at Amazon) I probably have to buy one. But one of the reasons I bought the Touchmix 16 and powered speakers was to avoid additional pieces of equipment so I have a couple of questions first.

I had some feedback at an outdoor wedding recently and ultimately resorted to lowering sound levels. After some research I added delay as one of the four available on-board effects in the mixer in case of future feedback. Have you tried using the delay effect to control feedback? Any thoughts of that as an alternative?

You only had two speakers to control, so had a channel for each. Assuming two independent mains and two independent monitors (Aux 1 and 2) how would you use the Go-Rack? Both channels for the monitors? As an effects loop for the mixer? Or just buy two?

Thanks much for any thoughts.

[almeriastrings]

A delay is not a direct solution for feedback but using carefully set times and precisely placed speakers further back down the room the "Haas" effect can mean you can reduce levels near the stage from the FOH which might help with feedback. It does require careful setup and if you don't get it exactly right, it can really mess things up. Normally, you run the checklist of anti-feedback measures (mic position, monitors, room EQ and so-on) and you next best line of defense is a good AFS system. The Touchmix 16 does not have this included, unfortunately, though the new Touchmix 32 does. So, with that, you could run a pair of mains in mono (daisy chained) though one channel of a Go-Rack and a monitor, independently, though the other channel. Obviously if you need more monitors you then need more AFS units..... it can also depend on what is causing the feedback. You can. for example, use a GoRack as a mic preamp and the signal then goes MIC>GORACK>LINE INPUT on the mixer. If you only have a couple of mics, this can then cover the entire system. On possible flaw here is that the GoRack in mic pre mode does not supply phantom power, however, but it does work well with self-powered mics (electrets with battery), dynamic mics, or regular condenser mics if you run them through a phantom power supply, though that is beginning to get a bit messy and you have yet more boxes and connections. Given the price of the GoRacks, if I was running two AUX sends to monitors, I'd just get another one and dedicate it to that using another for the mains if necessary. I have a couple of 19" rack DBX AFS2 units and an older dual channel Peavey Feedback Ferret D that I can use if I need to cover multiple speakers, but if I didn't, I would certainly get another GoRack or two.

[pops1]

If you use the XLR output from the Gorack does that still need to go into a line input? I have just put it into the mic input on the PA and it seem to work fine. I keep the input volume and output volume fairly low. I would have to use 1/4" to go into a line input. If that is the case why do they put XLR outs on it? Thanks almeriastrings for all your knowledge.

[almeriastrings]

Yes. The XLR output is a true line-level output (max +14dBu), though some mic preamps do have a very high headroom and might just cope fine. It depends on their design. If a pad switch is available, I'd engage it, however. I think they probably put the outputs on XLR's to match the typical output sockets on a mixer. Usually you would be going from a cable with XLR(F) to XLR(M) straight into a powered speaker. If instead you are plugging it into a line input on a mixer, you would use a XLR(F) to TRS 1/4 jack cable.

[fiddleround]

A delay is not a direct solution for feedback but using carefully set times and precisely placed speakers further back down the room the "Haas" effect can mean you can reduce levels near the stage from the FOH which might help with feedback. It does require careful setup and if you don't get it exactly right, it can really mess things up. Normally, you run the checklist of anti-feedback measures (mic position, monitors, room EQ and so-on) and you next best line of defense is a good AFS system. The Touchmix 16 does not have this included, unfortunately, though the new Touchmix 32 does. So, with that, you could run a pair of mains in mono (daisy chained) though one channel of a Go-Rack and a monitor, independently, though the other channel. Obviously if you need more monitors you then need more AFS units..... .

My Go-Rack arrived today along with some free Halloween candy (thanks Sweetwater). It looks impressive enough to use as a mixer for a two piece band, and easy to carry along for emergency use. One concern: The box suggests the feedback eliminator works only with "microphones using patented dbx AFS technology". I don't remember seeing any such limitations when I researched it on line. I am pretty sure my microphones lack any such technology. Are we sure it's going to work when I run into feedback at a gig? Usually the culprit is me and my ATM 350 fiddle mic getting sideways with the monitors and/or mains.

[pops1]

I believe the Go-Rack is using the patented dbx AGS technology, not the mic's.

[almeriastrings]

Pops1 is correct.

There are no special microphone requirements. Note, however, it does not supply or pass +48v phantom power. So with an ATM350 you would need to use a separate phantom power supply between the mic and the GoRack. Also make sure the button for mic/line level on the back is set to 'mic'.

If your mixer has channel inserts, that would be a better method.

Alternatively, use in between your monitors and mains - this is the generally recommended method as it covers all inputs and eventualities.

If using it as a 'standaione' two-channel mini mixer, obviously, it is not exactly 'full featured' for this, but in an emergency would work - provided you use mics that do not require phantom power. So, all dynamic mics are OK, so too are electret condenser mics that can run off a battery (e.g., Shure SM94, AT MB4K, AKG C1000S or Rode M3). If you do want to use a mic that needs +48v, then you will need a separate phantom power supply.

Also note the EQ applies to both channels.....

Personally.... as an emergency back up this is what I carry:

1) A small A&H Zed 10FX (you could use any similar small console, such as an Alto or Behringer)
2) Gorack

That works really well into powered speakers and you get nice mic pres with +48V plus FX plus good anti-feedback. Very small and light. It all fits into a laptop case... if a digital console ever failed (it has only happened to me once) that is just enough to keep the show on the road.

[fiddleround]

[QUOTE=almeriastrings;1529824]Pops1 is correct.


I am happy to report the GoRack worked well for feedback this weekend at a noisy bar, where space limits us to using our mains as monitors as well (they are slightly behind us).
I set it up between the mixer and the two powered speakers as suggested.

I heard the pre-feedback whine one time, but then it stopped and did not return.

Thanks for the suggestion.

[derbex]

Rather irritatingly, they seem to about 3 times the price in the UK -£80 vs $30

[Br1ck]

I use mine between my Bartlett mic and my amp or PA. I wanted something quick to plug in at open mics when you never know what to expect. I did have to get a stand alone phantom power supply but I found a small case at an antique store that houses everything in an easy package. Really, for $29 everyone should have one.

[almeriastrings]

I am happy to report the GoRack worked well for feedback this weekend at a noisy bar, where space limits us to using our mains as monitors as well (they are slightly behind us).
I set it up between the mixer and the two powered speakers as suggested.

I heard the pre-feedback whine one time, but then it stopped and did not return.

I am pleased that has worked out for you. Yes, they really are very effective. Takes a lot of the stress out of the job if you are performing and running the sound. They jump on that incipient feedback very quickly indeed, and do not seem to have any audible artifacts or other negative effect upon the overall sound.

You can adjust the 'sensitivity' and notch width using the AFS button and control wheel (see user manual). The number '2' setting seems best suited to typical acoustic music performances in my experience.

Derbex - totally agree. The best prices I have seen in Europe have been around €89.... since we both need the higher voltage PSU and 'correct' plug for our regions, rather than the US PSU, we don't have much choice. They have come down to that price though, from €140 a few months ago, so maybe they'll come down again...if they do, I'll probably pick up another one as they are so useful.

[almeriastrings]

Update... I checked the box and PSU and indeed, it is 'universal' - so will run from 110-230v. Even better, a full set of international plug adapters is included... so, on that basis I grabbed another one from a US dealer offering them via Ebay at $29.95 via the 'Global Shipping Program'. This added $13 shipping to Spain (very fair, I thought) and another $10 in import costs with nothing more to pay.

I used my existing one twice this week. Once in a really 'hard' (reflective) room with one channel looped through to the mains, and the other to a single foldback monitor, and it did a stellar job. The other time was for a larger gig and this time, I used it just on the two AUX outputs to a pair of QSC K8's serving as wedges. Again, it did a great job. Literally 'set and forget'. A performer moved a condenser mic at one point and you just (barely) heard the feedback start... then near instantly notched out and gone. Much faster than I could have done it! A second one will be useful for when I'm using the QSC Touchmix 8, allowing one on the mains if necessary, plus one for a pair of foldback speakers, or alternatively, four channels of AFS on the AUX outputs. The entire thing, mixer + pair of GoRacks will also fit in one laptop case...

One of my regular gigs is in a very nice restaurant on the third floor of a shopping centre... and the more compact and light everything is, the better...hauling 19" rack ups there is no fun at all.

[banjoboy]

Thanks almeriastrings for all of the info. I just ordered two dbx go rack units from Sweetwater. I'm assuming that it is best to have two units...one for mains and one for monitors. Hopefully they are as easy to use with my QSC Touchmix 8 as you've reported. I'm looking forward to feedback free gigs. Can't say that I'll use the other features much as the QSC should cover those areas, or do you use the other features?

[pops1]

Thanks almeriastrings for all of the info. I just ordered two dbx go rack units from Sweetwater. I'm assuming that it is best to have two units...one for mains and one for monitors. Hopefully they are as easy to use with my QSC Touchmix 8 as you've reported. I'm looking forward to feedback free gigs. Can't say that I'll use the other features much as the QSC should cover those areas, or do you use the other features?

They can handle two mic's or mains and monitors in one unit. Two is nice to have tho, I have two.

[banjoboy]

Well the only have two inputs into outputs. So if you're running two separate speakers and two separate monitors you would have to have two units. Right?

[Br1ck]

If you have separate sends and returns for both mains and monitors, you could use one GoRack. Chances are you won't use anything but the anti feedback and maybe the gain on these units.v