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X12 placement

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Hobbyist2004 View Drop Down
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    Posted: 14 December 2004 at 12:36am

Hi everyone,

My rig is a live band setup, 1 - X12 and 2 - X1's per side. I was curious about room coverage with just one X12 per side. Would it be better to place 2 X12's per side with the inside edges touching to form a wider pattern? The X12's sit on top of 2 stacked X1's. Two X12's shouldn't be to much for the 2 X1's should they?

 

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hiphei View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hiphei Quote  Post ReplyReply Direct Link To This Post Posted: 14 December 2004 at 7:00am
Hi!

I've never used (or heard) such speakers, but generally dB/w/m values suggest me that you would need two of such subs/ each top cab (eg. SD 740N is 111dB/w/m according to data sheet, two X1 subs would be around 105-106 dB/w/m.). I don't really know how big bass levels your band needs, but low frequencies always eat a lot of power (eg. miced kick drum, or DI'ed bass.. I have gotten away with 2x18" commercial subs sharing 1400W in small places though they were pretty poor design). If it's vocal only, then there's really no need for subs..

Yes the coverage will be better, but then you need to be more careful in speaker placement to avoid POTENTIAL stage feedback problems.. (though with good speakers, as Rog's designs seems to be, i've rarely had feedback-problems. In such case the culprit has usually been too loud stage volume, meaning loud monitors, etc..)

These are just 2cent thoughts.. If there is better knowledge, please correct me! (I'm not PRO in any means.. but as you know it's always easy to give some advise.. )

Regards,
-hiphei-
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Centauri View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 14 December 2004 at 8:08am
Originally posted by Hobbyist2004 Hobbyist2004 wrote:

Would it be better to place 2 X12's per side with the inside edges touching to form a wider pattern?


Bad idea, as two cabinets side by side will cause comb filtering interference patterns which will actually decrease your coverage area - this configuration only works with speakers that have a very tight and defined dispersion pattern ie: waveguides.  The coverage provided by the 12s should be plenty, but maybe changing the HF horn to a 90 degree slot loaded CD type will give wider coverage across the top end.

Cheers
Graeme
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hiphei View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hiphei Quote  Post ReplyReply Direct Link To This Post Posted: 14 December 2004 at 8:37am
Oh yes! (Thanks Graeme for correcting!)

I shouldn't have made assumptions.. (assumed these horns are 90deg or less.. silly me! )

-hiphei-
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Hobbyist2004 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hobbyist2004 Quote  Post ReplyReply Direct Link To This Post Posted: 14 December 2004 at 4:46pm

Thanks for the information.  So comb filtering interferance patterns are created by an example of 2 - X12's placed with the inner walls touching(parallel) to each other. Creating a fan like shape, right?

If you just placed them next to each other, both facing the same direction(forward), does this still present a problem?

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hiphei View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hiphei Quote  Post ReplyReply Direct Link To This Post Posted: 14 December 2004 at 5:58pm
Yes it does. Combing occures where two 'speaker patterns' overlap (and when the speakers are reproducing same signal.). By turning 'beams' apart overlapping zone (where combing occures) will be narrower. That situation is slightly different in real room which is full of reflections from walls, floor, ceiling, etc..

Great place to find such information is 'study hall' at www.prosoundweb.com.. Check that out!

..excuse my strange english! It's been a while since i was in school..

-hiphei-

p.s. watch out their forum 'netiquette' very carefully. They have own forum for newbies, band members, etc.. (like me for example ) called 'LAB lounge'. I have learnt a lot just by following that site..


Edited by hiphei
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mobiele eenheid View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 14 December 2004 at 11:25pm

Quote but generally dB/w/m values suggest me that you would need two of such subs/ each top cab (eg. SD 740N is 111dB/w/m according to data sheet, two X1 subs would be around 105-106 dB/w/m.).

Sensitivity is one thing, powerhandling is a second factor. If you're comparing speakers or matching look at the SPLmax, not just sensitivity (or powerhandling).

For instance a 80 Wrms, 111 dB/w/m driver will get a SPLmax of about 130 dB. While a 2000 Wrms 105,5 dB driver will get to 138,5 dB. In such a case sensitivity didn't tell a thing.

Btw. Manufactures will show the sensitivity at the frequency the driver is most sensitive for. Average sensitivity will be lower, you can see this by looking at the graphs given by the manufacturer himself. And in this case the double 12" will be the limiting factor, thus limiting the SPLmax of the SD 740.

Cheers



Edited by mobiele eenheid
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hiphei View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hiphei Quote  Post ReplyReply Direct Link To This Post Posted: 15 December 2004 at 8:49am
Thats true that one needs to take powerhandling into account. I realize now that i made an error thinking that subs handle a lot less power (Of course the powerhandling doubles when two are used.. Also impedance halves and more power is drawn from [the same] amp..).

-hiphei-
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