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QSC K12 & KW118 vs JBL MRX512M/515 & MRX528S

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Robert Chafe:
I too consider a MRX system to be sideways move as far as sound quality.  My main complaints with our current system are the KW118's.  They just don't "thump" as I've heard a single MRX528 with a XTi4000.  Also now that I'm getting up to (8) seperate cabinets plugging in (3) cables per cab (in, out and power), cabling is getting a little overwhelming. 

I know the srx system would be a nice step up but the cost (40% more per cab) vs what I would use them for doesn't make sense to me.  Having (4) MRX512's I can arrange (2) per side to cover a wide room with 140 degrees of coverage.  Or (2) for mains and (2) for monitors on smaller trio gigs. Etc. etc.


Rob Spence:

--- Quote from: Robert Chafe on January 25, 2011, 10:53:12 pm --- My main complaints with our current system are the KW118's.  They just don't "thump" as I've heard a single MRX528 with a XTi4000. 

--- End quote ---
I think you mean KW181 but what ever...
I had an interesting discovery last weekend when my pair of KW181s were not thumping like I thought they should...
Close inspection showed me that one of the subs had the polarity switch pushed in so they were canceling each other  :-[

Also, consider when you heard other subs pounding... what was the rest of the system and the skill of the engineer?

Robert Chafe:
Yep KW181's.

Comparing a pair of KW181's to a single MRX528S powered by a XTi2000 bridge and crossover @ 100hz with program music - IE current dance stuff.

Here are the specs between the three boxes I'm contemplating.  +/- 3db Frequency response MRX518 = 45-200Hz, SRX718 = 34-220Hz, KW181 = 40-112 Hz.  Maximum SPL MRX518 = 133db, SRX718 = 130SPL, KW181 = 135db.  So an I correct in taking this to mean with adequte power to the JBL's - the frequency response of the KW181 is only slightly worse than the SRX718 and the KW181 is capable of being 5db louder??

George Dougherty:
The max output spec is largely theoretical BS.  It's calculated rather than measured and it would take a cool driver with brief bursts of max power to achieve.  Anything that's already warmed up will quickly move into power compression on the driver and the actual max sustained output would be much below that.  Some drivers will cool better than others and will also give more output than others as a result.

The K12 will not have the bottom end of a 15" loaded cab, but it will also likely have better midrange dispersion and response.  One thing you can try is letting the sub cross higher and reinforce the low-mids a bit in the 100-120Hz range.  "Thump" typically requires strong output in the 80-120Hz range. 

The JBL MRX system may have more low-mid harmonic distortion adding to the appearance of more thump, it may have had a bit of a bump in the system EQ, the subs may have been running hotter, they may have had a Sonic Max-crapalizer patched in that was boosting harmonics adding to the appearance of more thump but muddying up the bottom end as well, they may have had a better engineer mic'ing, EQ'ing and compressing the kit and bass.   Lots of different reasons for why you heard more thump from the one setup vs your typical setup.

Bob Kenton:
Another thing to consider, according to the Crown gurus on the Crown forums the XTi amps are not really designed to run hard bridged.


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