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Church and H.O.W. Forums for HOW Sound and AV - Your Displayed Name Must Be Your Real Full Name To Post In The Church and HOW Forums => Church Sound Archive => Topic started by: Russ Buck on June 15, 2010, 12:09:09 pm

Title: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: Russ Buck on June 15, 2010, 12:09:09 pm
Still trying to figure out speakers for my church.  My latest idea is to find some decent mains to fly and then a powered sub.  Was wondering if anyone has anything to say about these powered subs?

Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: Dick Rees on June 15, 2010, 01:31:42 pm
Here's a link to a search of the PSW for QSC Ksub:

http://www.google.com/#hl=en&source=hp&q=QSC+Ksub+%2 B+site%3Asrforums.prosoundweb.com&aq=f&aqi=&aql= &oq=&gs_rfai=&fp=2f8bff4900875437

I have only heard these on the showfloor of my local pro sound shop.  They were running with the K10's or K12's.  Being engineered as a set, I suspect this is using them to their best advantage.

What they would sound like in an open sanctuary is only a guess for me.  They did seem nice and "tight", but I've heard comments along the lines of "one note wonder" and "kick drum box" as opposed to a genuine sub.

I must say that I do not favor using subs in open sanctuaries.  I think they bring more problems than benefits.  But that's just my opinion.

DR
Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: Justin Bartlett on June 17, 2010, 11:21:21 pm
Dick Rees wrote on Tue, 15 June 2010 12:31

Here's a link to a search of the PSW for QSC Ksub:

 http://www.google.com/#hl=en&source=hp&q=QSC+Ksub+%2  B+site%3Asrforums.prosoundweb.com&aq=f&aqi=&aql= &oq=&gs_rfai=&fp=2f8bff4900875437

I have only heard these on the showfloor of my local pro sound shop.  They were running with the K10's or K12's.  Being engineered as a set, I suspect this is using them to their best advantage.

What they would sound like in an open sanctuary is only a guess for me.  They did seem nice and "tight", but I've heard comments along the lines of "one note wonder" and "kick drum box" as opposed to a genuine sub.

I must say that I do not favor using subs in open sanctuaries.  I think they bring more problems than benefits.  But that's just my opinion.

DR


I'm curious what you mean by "open sanctuaries."
Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: Dick Rees on June 17, 2010, 11:35:46 pm
Justin Bartlett wrote on Thu, 17 June 2010 23:21

Dick Rees wrote on Tue, 15 June 2010 12:31

Here's a link to a search of the PSW for QSC Ksub:

  http://www.google.com/#hl=en&source=hp&q=QSC+Ksub+%2   B+site%3Asrforums.prosoundweb.com&aq=f&aqi=&aql= &oq=&gs_rfai=&fp=2f8bff4900875437

I have only heard these on the showfloor of my local pro sound shop.  They were running with the K10's or K12's.  Being engineered as a set, I suspect this is using them to their best advantage.

What they would sound like in an open sanctuary is only a guess for me.  They did seem nice and "tight", but I've heard comments along the lines of "one note wonder" and "kick drum box" as opposed to a genuine sub.

I must say that I do not favor using subs in open sanctuaries.  I think they bring more problems than benefits.  But that's just my opinion.

DR


I'm curious what you mean by "open sanctuaries."


Lots of cubic feet of space rather than low ceilinged room.
Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: George S Dougherty on June 18, 2010, 10:47:49 am
Russ Buck wrote on Tue, 15 June 2010 10:09

Still trying to figure out speakers for my church.  My latest idea is to find some decent mains to fly and then a powered sub.  Was wondering if anyone has anything to say about these powered subs?




On the sub end, check out the Bill Fitzmaurice designs.  It's usually not too difficult to find someone in a church with decent woodworking skills and most anything in his stable will far outperform a little box like the ksub.  Find a decent amp on Craigslist and you're all set.
Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: Robert Sims on June 19, 2010, 01:37:13 am
Russ,
Sorry for the late reply was in Smaart class all week. I have K12's and KSubs in the youth room. The K12s are actually nice sounding for the money. The Ksubs are a good compliment but I wouldn't use any of these in a main sanctuary except maybe using the K12s as a powered monitor. They can get loud and the subs will keep up in a smaller room (40x30). It's a quick set up and no speaker processing is needed since they are already processed and crossed over on board. (i havent check aligment - surely they wouldn't pair the 2 without aligning??)  The subs are tuned a little high for me so I just run an aux feed and EQ the feed. When I do that I switch the tops to the low end boost to covered what I pulled out of the subs. (again, that's going to affect alignment but is it worth buying a processor, kids don't seem to mind.)

You don't say what your room size or program material is so my review is based on my application.  
Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: JAOgann on June 22, 2010, 10:45:43 pm
Powered Subs are good. They usually have the crossover installed as well. Parts Express sells a lot of them. We use an EV S-18 and a 500watt amp (half of a stereo amp) and crossover and rattle the walls in a 600 seat room. Two keys we have learned. 1. Get a crossover with a high pass filter and turn it on.   2. Fly the sub as well. When we flew our sub it made it 100 times better.

You could get a JBL JRX118SP Powered 18" from Parts Express for $750 (Sku 245-818) and be done. It has the amp, crossover etc. Just plug and play - - but fly it up there with your mains and you will really love it.

Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: George S Dougherty on June 24, 2010, 01:38:36 pm
Jim Ogann wrote on Tue, 22 June 2010 20:45

Powered Subs are good. They usually have the crossover installed as well. Parts Express sells a lot of them. We use an EV S-18 and a 500watt amp (half of a stereo amp) and crossover and rattle the walls in a 600 seat room. Two keys we have learned. 1. Get a crossover with a high pass filter and turn it on.   2. Fly the sub as well. When we flew our sub it made it 100 times better.

You could get a JBL JRX118SP Powered 18" from Parts Express for $750 (Sku 245-818) and be done. It has the amp, crossover etc. Just plug and play - - but fly it up there with your mains and you will really love it.




Unless you can put it somewhere where you trade boundary loading with the floor for boundary loading with a solid (not drop) ceiling, I'd recommend against flying a sub since you put it into free space and lose output capability.  Flown subs need to obey the same rules of placement as ground stacked subs.

Rules of thumb, put it near a wall or corner if at all possible.  Place the radiating source within 2ft of a boundary or further than 8ft.  A boundary needs to be 14ft+ in length to really be considered a boundary in the low frequency regions.  Keep multiple subs within 2ft (radiating sources) of each other for coupling or further apart than 56ft to avoid interference in the passband.

If you're crossing over a sub in the <100Hz region, placement of the sub within the rules above won't impact sound quality except for evenness of coverage due to variations in volume over distance.  If they're crossed higher, a large distance between subs and mains will allow listeners to locate the low mids with the subs instead of the highs.  Time alignment of the subs to the mains can also have an impact on output so it may be that flying your sub solved issues with location and alignment.  None of that is anything that couldn't have been solved with the sub located on the floor and not hanging over anyone's heads.

The only possible advantage flying a sub might have is locating the source further away from the listeners resulting in more even coverage over the listening area as the -6b loss distance increases the further you are from the source.  In a room with the audience located right up next to the stage, a short stage and decent ceiling height flying a sub to get it away from the front row could be a good option.
Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: Brad Weber on June 26, 2010, 01:59:36 am
Jim Ogann wrote on Tue, 22 June 2010 22:45

Powered Subs are good. They usually have the crossover installed as well. Parts Express sells a lot of them. We use an EV S-18 and a 500watt amp (half of a stereo amp) and crossover and rattle the walls in a 600 seat room. Two keys we have learned. 1. Get a crossover with a high pass filter and turn it on.   2. Fly the sub as well. When we flew our sub it made it 100 times better.

You could get a JBL JRX118SP Powered 18" from Parts Express for $750 (Sku 245-818) and be done. It has the amp, crossover etc. Just plug and play - - but fly it up there with your mains and you will really love it.

The JRX118SP are intended to be ground stacked or mounted on a pole or stand, neither it nor the EV S18 have integrated flyware or are intended to be flown.  While flown speakers can often have benefits, you want to avoid flying speakers over people's heads without using speakers intended for that purpose, using proper rigging hardware and techniques, having someone properly qualified verify the connectivity to the building structure and having the installation performed by a qualified party or firm.


George S Dougherty wrote on Thu, 24 June 2010 13:38

Unless you can put it somewhere where you trade boundary loading with the floor for boundary loading with a solid (not drop) ceiling, I'd recommend against flying a sub since you put it into free space and lose output capability.

I generally agree with your other comments but have to disagree on this one.  Experts such as Dave Gunness and Pat Brown have addressed this topic quite well an d found that the 'boundary loading' traditionally attributed to ground stacked subs is a fallacy.  One of the issues is that the floor boundary is somewhat shared by the receiver (the listeners) and thus the related gain for that boundary is present regardless of the speaker locations.  Instead, the perceived increase in loudness attributed to ground stacked subs is greatly due to in increase in the indirect sound.  The level of the sub direct to the listeners does not increase that much since they share the floor boundary, however the sound from the subs hitting the walls and ceiling and then reflected to the listeners does increase.
Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: Tim Padrick on June 27, 2010, 08:01:09 pm
Brad Weber wrote on Sat, 26 June 2010 00:59


I generally agree with your other comments but have to disagree on this one.  Experts such as Dave Gunness and Pat Brown have addressed this topic quite well an d found that the 'boundary loading' traditionally attributed to ground stacked subs is a fallacy.  One of the issues is that the floor boundary is somewhat shared by the receiver (the listeners) and thus the related gain for that boundary is present regardless of the speaker locations.  Instead, the perceived increase in loudness attributed to ground stacked subs is greatly due to in increase in the indirect sound.  The level of the sub direct to the listeners does not increase that much since they share the floor boundary, however the sound from the subs hitting the walls and ceiling and then reflected to the listeners does increase.


I disagree.  Case in point: In one club at which we play regularly, our stacks (including subs) have to set about 4 1/2' from the side walls (owing to the DJ system).  Usually I cut a bit of 60Hz from the subs, but here, owing to boundary cancellation, not only do I not need the cut, EQ at 60Hz makes very little discernable difference.  http://www.padrick.net/LiveSound/CancellationMode.htm
Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: Brad Weber on June 28, 2010, 12:09:18 pm
Tim Padrick wrote on Sun, 27 June 2010 20:01

I disagree.  Case in point: In one club at which we play regularly, our stacks (including subs) have to set about 4 1/2' from the side walls (owing to the DJ system).  Usually I cut a bit of 60Hz from the subs, but here, owing to boundary cancellation, not only do I not need the cut, EQ at 60Hz makes very little discernable difference.  http://www.padrick.net/LiveSound/CancellationMode.htm


I'm not sure what you are disagreeing with.  The discussion was about boundary or space loading where the concept is that the source is close enough to the boundary to have coherent summation of the direct and reflected sound at all locations and for all frequencies of interest.  You seem to be discussing almost the opposite, where the path length difference from a reflection is sufficient that it does affect the response within the frequencies of interest.

The interaction of the direct and reflected signals is based on the path length difference between the two signals at the receiver (listeners).  If the difference is one half wavelength then destructive interference or cancellation occurs, if it is one quarter wavelength or less then some level of constructive interference or summation occurs and if there is no difference (both signals in phase) then there is full summation.  The idea of boundary loading is that the source is physically at the boundary, thus any reflection has no path length difference from the direct sound and sums for all frequencies.  The same applies to a receiver, if the receiver is located at the boundary then that also causes the reflections from that boundary to be coherent with the direct sound.  So whether the source or receiver is at the boundary, you get the same resulting summation, but only for one or the other.

It gets more complicated when the source is close to but not at a boundary.  In that case you have to look at the relative paths for the direct and reflected sound and how those relate to the wavelengths of the frequencies of interest.  With subwoofers you have a limited frequency of interest and one that relates to longer wavelengths.

If a listener was at the subwoofer then any boundary interaction would be be based solely on the distance from the subwoofer to the boundary.  However, the listeners are not usually at the subwoofers, thus you have to consider the path length differences for the listeners.  Look closer at the typical floor boundary or 'floor bounce' condition and you will find that for a subwoofer one usually does not have to be that far from the sub for the resulting path length difference between the direct and reflected sound to be less than one quarter wavelength. Basically, even though their ears are not at the floor, the listener does not have to be that far from the sub to start sharing the effects of the floor boundary.  But that does not necessarily hold true for more distant surfaces, those may create reflections with a much greater path length difference, or for higher frequencies with much smaller wavelengths.
Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: Darin Brunet on June 28, 2010, 01:41:49 pm
Russ Buck wrote on Tue, 15 June 2010 12:09

Still trying to figure out speakers for my church.  My latest idea is to find some decent mains to fly and then a powered sub.  Was wondering if anyone has anything to say about these powered subs?




I have used the QSC K-10 and K-12 self-powered speakers and think they represent a good value and sound quality. The KSub is a bandpass design and many feel this design style as one-noted or boomy. I wholeheartedly disagree with this mentality.

In many instances they are less able to be localized due to the acoustic filtering of harmonic distortion products that cannot be reduced with a crossover, whether passive or active, and it cannot be EQ'd out. On the other hand, a poorly designed bandpass can suffer port compression heard as "chuffing" or air turbulence caused by the air passing over sharp/un-radiused edges (also a problem with poorly designed reflex systems). I have designed many bandpass systems that are very musical and play to very high levels.

Point is, there are terrible products out on the market that utilize many different design styles, whether bandpass, reflex, sealed or TL. I cannot dissuade anyone from using any particular design as long as the design compromises are understood and dealt with.

If used properly, I think the KSub is a quality unit and will serve you well. Perhaps several of them will be required to meet your output needs.
Title: Re: QSC KSub - Dual 12" 1000 Watt Active Subwoofer
Post by: Darin Brunet on June 28, 2010, 01:52:00 pm
Jim Ogann wrote on Tue, 22 June 2010 22:45

Powered Subs are good. They usually have the crossover installed as well. Parts Express sells a lot of them. We use an EV S-18 and a 500watt amp (half of a stereo amp) and crossover and rattle the walls in a 600 seat room. Two keys we have learned. 1. Get a crossover with a high pass filter and turn it on.   2. Fly the sub as well. When we flew our sub it made it 100 times better.

You could get a JBL JRX118SP Powered 18" from Parts Express for $750 (Sku 245-818) and be done. It has the amp, crossover etc. Just plug and play - - but fly it up there with your mains and you will really love it.




Perhaps you mean the JBL VRX918SP self-powered sub. The JRX118SP is not meant for flying.