ChazHS Posted March 21, 2009 Posted March 21, 2009 Right, I haven't posted on here in a while - mainly due to being too busy with work! I've had a search about and have accumulated some questions which don't seem to be answered anywhere on this forum yet so I'll ask them now! I'm using a PS8/LS400 system powered by Crown XTi series amplifiers. Now, firstly, I've noticed a lot of talk of people saying that the PS series are a 'single stick a side' system, meaning they don't respond well to clustering or arraying and you end up with 'dead spots' due to their HF dispertion pattern. My question is this, if I were to put two boxes next to each other something like this: http://www.pro-event-hire.co.uk/files/images/ps8_stacking.gif Would this cause the HF 100/50/100/50 issues? Or is that only if they are arrayed vertically? Please note: This would be a single stack system of 2 PS8s, not a double stack of 4 per side Also, the PS8 controller should provide all of the limiting protection required as long as the inputs are unclipped, is this correct? I'm using a Crown XTi 2000 for the PS8s (475W into 8ohm, Nexo reccomend anywhere from 200W-500W so I should be ok) - so if needs be I could turn on their clip limiters too, but wouldn't this confuse the PS8TD controller? Thanks.
Rob_Beech Posted March 21, 2009 Posted March 21, 2009 The PS8 (and PS10 and 15) are not boxes to be arrayed at all. Vertically is worse, but horizontally is also a bad idea. That's pretty much all there s to it. Feel free to try it.
ChazHS Posted March 21, 2009 Author Posted March 21, 2009 The PS8 (and PS10 and 15) are not boxes to be arrayed at all. Vertically is worse, but horizontally is also a bad idea. That's pretty much all there s to it. Feel free to try it. Is this due to their dispertion pattern? Will it cause a HF 'bleed' across the middle of the two cabinets in which there is the combined HF from both cabs and then where one finishes and the other is still covering you notice a reduction in this volume?
Rob_Beech Posted March 22, 2009 Posted March 22, 2009 In a way. Position of the listener is important. In it's simplest form, you never reall know what you're going to get from one seat to the next. You do really if you work it out, but generally speaking the response will change quite substantially as you move up and down left and right and forwards and backwards.
Killyp Posted March 22, 2009 Posted March 22, 2009 The easiest way to imagine it is like two pebbles being dropped in a pond - in some places the waves (sound waves) add up to create higher waves where the sound will be louder, and in other places, the waves meet to form a lower trough where there will be a drop in sound. This forms some very complex patterns and different frequencies add and subtract in different places. You really need boxes with tight dispersion patterns before you can start to array them.
ChazHS Posted March 22, 2009 Author Posted March 22, 2009 So basically, the cabinets won't array well and you will end up with merging sound wave issues. Isn't this true of nearly all non-line-array speaker cabinets though?
mervaka Posted March 22, 2009 Posted March 22, 2009 yep. you get a washy phase effect as you move between nodes/antinodes.
Rob_Beech Posted March 22, 2009 Posted March 22, 2009 Incorrect! The wrong end of the stick. A box design may have a "guide" to control dispersion down to a lower frequency. This is generally found in horn loaded mid/tops. It is often plastic moulded for compression drivers and smaller mid drivers but formed from the wood of the cabinet for the low mid drivers. However, this control takes more than just box design. A typical array using the correct type of boxes will give a uniform coverage. This DOES NOT HAVE TO BE A LINE SOURCE. Point source is EVERY BIT as good at this job as a line source. In some respects it's better as you can control horizontally aswell. 1 box on its own will not give its rated controlled dispersion at all frequencies. However arrays/clusters will get closer to this as we look at the entire array as a single.. point source. Line array does this in a similar way but the horizontal control is very limited. Below this frequency the dispersion is somewhat more un-controlled. A cabinet with a reflex mid driver will as a rule have a much less controlled dispersion, or rather it's control of dispersion does not go as low. This is what we see in your standard 12+1 15+1 etc reflex boxes. None of these are DESIGNED to array. Some will work better than others. Add an asymmetrical HF driver to the equation and you make things less happy together.
ChazHS Posted March 23, 2009 Author Posted March 23, 2009 Right, I understand arraying them isn't the best idea... Now... can anyone help with the PS8TD side of things? Cheers.
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