mattyfish Posted February 8, 2007 Share Posted February 8, 2007 Hi folks, I regularly run PA at my church and the company who installed our PA added a Behringer Feedback Destroyer Pro PRO DSP1124P. I hate it! I really don't think that it works, just reduces the signal making it harder to make a good sounding mix. I have spoken to several pro engineers who have worked with and with out them and they prefer with out. To make this worse, the guy who is "in charge" of the PA, loves them and has bought another two for our 4 fold back channels! Thankfully, they (FBQ2496) have a by pass button on it so when I am in control that is straight on! (if you ask me, he should have spent the £300 on getting some pa training!?) If mics are positioned correctly and your monitor settings are also correct then you should not get feedback. As far as I know, there is only one other manufacture other than Behringer that manufacture them! What are everyones views on feedback destroyers? Has anyone worked with them? Do they really work, or do they just make it harder to mix? Link to comment Share on other sites More sharing options...
Bobbsy Posted February 8, 2007 Share Posted February 8, 2007 If you use the search function to look for "Feedback Destroyer" you'll get plenty of bedtime reading. What you'll find is that there are few items of gear that provoke so much debate pro and con. Some people swear by them, others swear at them. Personally, I'm not a fan of feedback destroyers and don't often use them. However, they shouldn't be as bad as you describe. One point that should be made is that you should never leave them in "automatic" mode during the show (or service in your case), otherwise they soon start to notch out way too many frequencies, including things like sustained guitar notes. The proper way to use them is to do a sound check where you drive the system to the onset of feedback and let the FBQ notch out up to, say, four frequencies...then lock it out at this setting for the actual performance. Feedback destroyers certainly aren't a "magic bullet" and cannot fix the impossible. You're always better off going back to basics and tweaking things like mic and speaker placement as the first step in the fight against feedback. However, where ops are inexperienced and not able to quickly identify feedback frequencies, destroyers can be a useful too. Finally, although I've posted it in here before, it's worth mentioning THIS LINK to a simple feedback trainer you can download and use for your ops to practice identifying the frequencies they need...good practice and fun as a sound op game! Bob Link to comment Share on other sites More sharing options...
Simon Lewis Posted February 8, 2007 Share Posted February 8, 2007 As far as I know, there is only one other manufacture other than Behringer that manufacture them! Bobbsy has neatly summed up the major issues. I would just add that you get what you pay for... The Shure DFR system and the larger Sabine units seem to work pretty well. However, you still need to use them as a tool, not rely on automatic operation. The Behringer Sharc appears to be considerably poorer than the Destroyer. If you have a church situation where hitting the bypass button gets you by, then that seems a pretty pragmatic solution. If you want to challenge the politics and personalities involved, then get reading James 5:16 ;-) Simon Link to comment Share on other sites More sharing options...
handyandi Posted February 8, 2007 Share Posted February 8, 2007 Finally, although I've posted it in here before, it's worth mentioning THIS LINK to a simple feedback trainer you can download and use for your ops to practice identifying the frequencies they need...good practice and fun as a sound op game! Bob Thats a great program bob, something to while the boredom away with & become pitch perfect at the same time! Shows up the extreme poor freq response of my PC speakers!! Cheers Andi Link to comment Share on other sites More sharing options...
mattyfish Posted February 8, 2007 Author Share Posted February 8, 2007 Very funny Simon! Church politics- oh dear...! Thanks for comments guys, that program is good Bobbsy. Link to comment Share on other sites More sharing options...
cedd Posted February 8, 2007 Share Posted February 8, 2007 Alto also manufacture a feedback destroyer at the lower end, and the DBX Driverack PA has one on its spec sheet too. The Alto one may be slightly better for auto mode as once the feedback has gone, it "unsets" the filter so it lets that frequency through again. Not sure if the BEhringer does. Worth a look though. I'm not normally a Behringer fan, although it's far too tempting when loking for, say a 24 channel mixer, to eye up the behringer at £400 against the Soundcraft LX7 at nearer a grand. It's just having the guts to step out and do it! Link to comment Share on other sites More sharing options...
dbuckley Posted February 8, 2007 Share Posted February 8, 2007 Feedback destroyers pretty much rock, BUT, (a) Bobbsy already did the autromatic mode stuff, and (b) use appropriately, which is almost never on the main mix, so any loudspeaker manager with built in anti-feedback (so DriveRack etc) - not useful, and © you have to work with them, not fight them. Most pro sound engineers have no truck with them. Their loss, in my opinion. Link to comment Share on other sites More sharing options...
Rob_Beech Posted February 8, 2007 Share Posted February 8, 2007 I've used the units and with the criteria stated above they do a job. But they're not for me, Maybe it is my loss, I'm not saying they're useless just that they're not for me. Link to comment Share on other sites More sharing options...
SteveB Posted February 8, 2007 Share Posted February 8, 2007 Anyone that owns a Behringer feedback destroyer is not alone. According to figures published by the FCC in that little run in they had in the colonies, between 2002 and 2004 over 11,000 were bought in the US alone. Based on what I have read in various internet discussions, a good percentage of those that own one have over optimistic expectations regarding its capability and/or are not willing to put in much work to get the best out of them. At the risk of repeating what has been said... The usual advice is to ditch the feedback destroyer and buy a 31 band graphic. If you do consider the advice which then follows regarding the use of a graphic to ‘tune’ a system? Generally it is to pull down no more than 4 bands to reduce feedback. Go back and apply the same principle with the feedback destroyer in manual mode and it will give you a lot more control than a graphic. If you want to simplify things use the single shot mode and use no more than five filters. Putting 12 filters, which are capable of reducing large chunks of the audio frequency by 48dB, is asking for trouble, and basically it just ends up reducing the level to compensate for the level being pushed up on the mixer. If the 1/3 octave graphic is an axe then the feedback destroyer in parametric mode goes from scalpel to chain saw. I own two of the early versions which I bought as cheap parametric eqs. Apart from being a bit noisy they work well as parametric equalisers. At best they’ll gain you an extra few dBs of gain before feedback. Just don’t expect it to work miracles on an inadequate system. Steve. Link to comment Share on other sites More sharing options...
dbuckley Posted February 8, 2007 Share Posted February 8, 2007 Putting 12 filters, which are capable of reducing large chunks of the audio frequency by 48dB, is asking for trouble But that's not what it does; the filters are all very narrow, much more so than the filters on a graphic, on some boxes 1/60th of an octave is possible. A graphic will alter the sound (as in tonality) of the system far more than a FBE with notch filters. Here's a device I'm thinking of getting: The Samson D-3500, a digital parametric EQ http://www.samsontech.com/images/productimages/D-3500-web.jpg Link to comment Share on other sites More sharing options...
SteveB Posted February 9, 2007 Share Posted February 9, 2007 But that's not what it does; the filters are all very narrow, much more so than the filters on a graphic, on some boxes 1/60th of an octave is possible. Not sure about the Samson, but with the Behringer (mentioned in the original post), not only is the frequency and gain variable, the bandwidth is too. According to my manual the bandwidth is variable between 2 octaves and 1/60th. In auto mode, “the width and depth of the filter are still being adopted to the feedback frequency”. Pushed to its limit you have 12 filters of 2 octave bandwidth and -48dB gain. Maybe it is just me, but that is a lot of altered sound. One thing a lot of people complain about is that the device suppresses sustained notes. The manual warns about this and also explains about varying the feedback sensitivity. Steve. Link to comment Share on other sites More sharing options...
Shez Posted February 9, 2007 Share Posted February 9, 2007 I seem to recall that Behringer's claims of very narrow cuts are rather optimistic. Manually setting them to their highest Q, yielded a far wider cut that it should have done last time I had a play with one. So they have potential to alter the wanted sound rather more than you might expect.I believe a lot of folks use them in home cinema set ups simply as a parametric EQ - maybe that accounts for some of that sales figure. Link to comment Share on other sites More sharing options...
Simon Lewis Posted February 9, 2007 Share Posted February 9, 2007 For those of you with Smaart (or similar analysis packages) it is worth looking at the transfer function for your GEQs, PEQs and feedback eliminators. For example, the Alesis MEQ231 provides about 2mm of fader travel that does anything useful. 1kHz on the front panel has an actual centre frequency of 1.16kHz. The Q varies dramatically with gain. The Behringer Sharc introduces 11ms latency. What a unit claims to provide and what it delivers can be two very different things. Looking at how a feedback eliminator actually behaves may well enable the user to stop the more extreme problems associated with these devices. Link to comment Share on other sites More sharing options...
paulears Posted February 9, 2007 Share Posted February 9, 2007 The biggest problem with these kind of things is that you need to let them feedback, in order for the filters to work - so in live work when you've not had a chance to really sort out the foldback properly, the only way they will work is to wait for feedback to start, and then let them stop it. Gently pushing a fader up to get the last ounce of volume, without the ringing turning into ear-shattering feedback isn't any use at all. That, for me is the issue. Most of my feedback problems happen when things didn't get sorted before. Like suddenly seeing one of the band move their mic stand 3 feet to the right, very close to the wedge of the person next door! These types of events don't get handled very well. A theatre near me who have no 'proper' sound man, bought a pile of feedback suppressors and slapped them on the lavalier radio mic channels. They were surprised when they seemed to make the problem worse! Link to comment Share on other sites More sharing options...
Steve_Hole Posted February 9, 2007 Share Posted February 9, 2007 I have 2 of the Behringer units in my church. They are OK, but as others have already said, you have to work with them, not fight them. I normally use them as a parametric eq rather than a an automatic feedback destroyer. When I do use them to find feedback, I only use a maximum of 4 filters, as using more then this I find alters to sound too much. Also I use them in single shot mode, once set, that's it. I often let them find the feedback and the use the parametric function on the same frequency and play with the gain / bandwidth to try and reduce the overall effect on the sound. Steve :D Link to comment Share on other sites More sharing options...
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