conan Posted September 8, 2009 Share Posted September 8, 2009 Hi, I was at an event the other day and noticed the PA used was db technologies DVA system. It sounded ok to be honest I was quite impressed. I then noticed there were 3 subs either side of stage and the middle one of the 3 was turned round and after asking apparently it was phase reversed. Why Is this and what would it do to the sound? Ta Link to comment Share on other sites More sharing options...
Simon Lewis Posted September 8, 2009 Share Posted September 8, 2009 Why Is this and what would it do to the sound? Probably an attempt at low frequency beam steering. The idea is (through cancellation over a fairly small range of frequencies) to modify the bass stack radiation pattern, thus reducing the bass levels on stage and (hopefully) providing more even bass coverage in the audience area. Searching the web for "cardioid bass arrays" will give you some homework to read up on... Link to comment Share on other sites More sharing options...
james.sealey Posted September 9, 2009 Share Posted September 9, 2009 I was at an event the other day and noticed the PA used was db technologies DVA system. It sounded ok to be honest I was quite impressed. I then noticed there were 3 subs either side of stage and the middle one of the 3 was turned round and after asking apparently it was phase reversed. Why Is this and what would it do to the sound? Have a read of http://www.ratsound.com/cblog/ in particular the bits about the Vortex sub design/layout. Link to comment Share on other sites More sharing options...
Bobbsy Posted September 9, 2009 Share Posted September 9, 2009 +1 on Dave Rat's blog...scroll back to near the beginning of the Blink 182 tour part. You'll find lots of thought-provoking info and theory on controlling the coverage from subs. Bob Link to comment Share on other sites More sharing options...
will_i_am Posted September 10, 2009 Share Posted September 10, 2009 reference to some good material there::: http://forum.speakerplans.com/how-tocardio...s+arrays#295199 A concurrent post has been automatically merged from this point on. reference to some good material there::: http://forum.speakerplans.com/how-tocardio...s+arrays#295199 http://www.squatjuice.com/phpBB3/viewtopic...00&start=30 Link to comment Share on other sites More sharing options...
sleah Posted September 11, 2009 Share Posted September 11, 2009 Hi, I was at an event the other day and noticed the PA used was db technologies DVA system. It sounded ok to be honest I was quite impressed. I then noticed there were 3 subs either side of stage and the middle one of the 3 was turned round and after asking apparently it was phase reversed. Why Is this and what would it do to the sound? Ta I'm reading this thread with just a passing interest. However, could someone kindly confirm what is meant above by "it was phase reversed"? I know what it actually means, but it's the context I'm not clear on. Was the phase reversed electrically, by swapping the terminals or by a piece of outboard, the cab is then spun round, so the speaker is still then physically pushing air in phase with the main stacks? OR Phase reversed by litterally spinning the cab so the speaker is pushing air out of phase with the main stacks? Hope you understand what I'm asking!! Link to comment Share on other sites More sharing options...
RustyBrooks Posted September 11, 2009 Share Posted September 11, 2009 Was the phase reversed electrically, by swapping the terminals or by a piece of outboard, the cab is then spun round, so the speaker is still then physically pushing air in phase with the main stacks? OR Phase reversed by litterally spinning the cab so the speaker is pushing air out of phase with the main stacks? Hope you understand what I'm asking!! Tend to point a speaker the "wrong way" so its firing away from the audience, cancelling the noise generated behind the stack, thereby creating a certain amount of directionality... d&b s J sub, and infra subs do this by having three drivers in a box, two forward, one back, makes life easier when building a pa, but the spin a box aproach also works well... the rat sound ideas look interesting, but there are very few opertunities in the real world to carry that much gear, and get that amount of space in the air, but maybe with some development, a solution like the j subs may present a compact(ish) steerable sub array. Oh, by the way, its not quite as simple as just turning a speaker around, there are all sorts of signal/time/polarity/pixie magic adjustments o be made to the signal to make it work Jon Link to comment Share on other sites More sharing options...
Chappie Posted September 11, 2009 Share Posted September 11, 2009 The reason for turning one of the boxes round and polarity-reversing it is to physically displace the drivers in one box from the others. This coupled with delay and level control creates the cardioid effect. It can be achieved in exactly the same way by placing multiple subs in a row, accurately spaced, one behind the other. Using 3 or 4 subs in this configuration can produce some quite amazing results with regard to rear cancellation. The practical downside of this method being it takes more space and time (not to mention more cabinets) to set-up and requires specific distances between cabinets. Being able to roll in a stack of cabinets already in position and correctly aligned in a processor saves a lot of time. Link to comment Share on other sites More sharing options...
RustyBrooks Posted September 13, 2009 Share Posted September 13, 2009 It can be achieved in exactly the same way by placing multiple subs in a row, accurately spaced, one behind the other. Using 3 or 4 subs in this configuration can produce some quite amazing results with regard to rear cancellation. The practical downside of this method being it takes more space and time (not to mention more cabinets) to set-up and requires specific distances between cabinets. Being able to roll in a stack of cabinets already in position and correctly aligned in a processor saves a lot of time. Have heard the rows of subs behind each other, and hve to say, on axis sounds really quite good, though seems to loose a lot of its control and smoothness off axis, ie at the mix position with subs very widly spaced, but the more we play with sub arrangments the better the results... Im still not convinced about the horizontal row of subs all over the front of the stage, yes the audience side sounds great, but everyone hates you for filling the pit with big speakers, and seem to get a lot of ooofff coming back onto the stage... they are a bit of a swine subs, need them, but so much hassle to get "right" Link to comment Share on other sites More sharing options...
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