QSC K118 subs

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MIXMASTERMACHOM

DJ Extraordinaire
Oct 16, 2011
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My friend bought the latest QSC subs and they are better than the KW subs. You won't be disappointed for sure!
 

prodjay

DJ Extraordinaire
Dec 13, 2009
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Bossier, Louisiana
Sorry I'm so late on this review,

Yes, I would say that they out perform the KW181's, They will definitely put out a large amount of bass. I used them in 1/2 of a convention center with about 100 people attending a Christmas party and 2 of these was over kill for this event. I never got them much over 30% and that was all that was needed.

Now let me add that I did not know that these subs will not cross over and send only a high pass signal, they will only pass a full range signal and this is not what I was looking for in a sub as I use different tops and some of them do not have any type of crossover in them. Now at this event I was using my K-12's and used them in the with sub mode.

Over all easy to move around and load, tons of bass with extra headroom, so if you don't need better processing that these provide, then you would be happy with these.
 

steve149

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Sep 26, 2011
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Sorry I'm so late on this review,

Yes, I would say that they out perform the KW181's, They will definitely put out a large amount of bass. I used them in 1/2 of a convention center with about 100 people attending a Christmas party and 2 of these was over kill for this event. I never got them much over 30% and that was all that was needed.

Now let me add that I did not know that these subs will not cross over and send only a high pass signal, they will only pass a full range signal and this is not what I was looking for in a sub as I use different tops and some of them do not have any type of crossover in them. Now at this event I was using my K-12's and used them in the with sub mode.

Over all easy to move around and load, tons of bass with extra headroom, so if you don't need better processing that these provide, then you would be happy with these.
Not sure if you use K12 or K12.2, but on the K12.2, if you use the "80 Hz KS" option in the Sub Menu, it should work properly coming off the subs thru outputs. On the K12, use the "EXT SUB" setting and it'll work, though the rolloffs are slightly different (80Hz vs 100 Hz).
 

prodjay

DJ Extraordinaire
Dec 13, 2009
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Bossier, Louisiana
Not sure if you use K12 or K12.2, but on the K12.2, if you use the "80 Hz KS" option in the Sub Menu, it should work properly coming off the subs thru outputs. On the K12, use the "EXT SUB" setting and it'll work, though the rolloffs are slightly different (80Hz vs 100 Hz).
I was using the older K12's and the Ext sub is the setting I used. I prefer that the crossover be in the subwoofer and just jump to the tops as I can do with my RCF 705's. But the KS118 will not do this. Like I stated I use other tops with my subs and some of them do not have any crossovers built in them.
 
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steve149

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I was using the older K12's and the Ext sub is the setting I used. I prefer that the crossover be in the subwoofer and just jump to the tops as I can do with my RCF 705's. But the KS118 will not do this. Like I stated I use other tops with my subs and some of them do not have any crossovers built in them.
There is a crossover in the subs .. just not a high pass to the tops .. but the QSC tops have that as an option on their input, so it works out to be basically the same thing. Only discrepancy is the one in the sub is at 80Hz, and the one in the older K is at 100.
 
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prodjay

DJ Extraordinaire
Dec 13, 2009
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Bossier, Louisiana
I see. Why not stick with RCA and go with the 708's? Is your system mixed already?
I have both QSC and RCF speakers and I had the chance to demo the KS181's so I thought I would give them a try, and I have a connection for QSC and can get a much better price for them, but the NO high pass on the QSC will make me look else where as I sometimes have to mix different brands of tops and bottoms depending on the event.

Oh well no harm, the QSC KS181 did sound great but just won't fit my needs.
 

TJS

GetSomeJuJu
Nov 8, 2018
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I'm a newbie when it comes to a lot, especially sound. I found this thread as I'm looking for subs for my QSC K12.2 speakers. While I most certainly will go with QSC subs, I'm curious as to what is meant by high pass and crossover in subs and how that relates to one another when it comes to subs and speakers.
 
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steve149

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I'm a newbie when it comes to a lot, especially sound. I found this thread as I'm looking for subs for my QSC K12.2 speakers. While I most certainly will go with QSC subs, I'm curious as to what is meant by high pass and crossover in subs and how that relates to one another when it comes to subs and speakers.
For any driver or speaker, the goal is to push the appropriate frequencies to the appropriate driver(s). For a sub and top combo (we'll forget about what's internal to the top), that means sending the subs the frequencies between say 35Hz and 150Hz (depending on size, type, etc.) and the tops get the signals above say 80Hz to 150Hz. The trick is maintaining a consistent frequency response and output level when the frequencies fall close to the region between the sub and top.

So let's assume we have a 15" sub that does say 40Hz-140Hz and a 12" 2-way top that's rated for maybe 60Hz-16KHz (or whatever).

Starting with the input signal, we want to eliminate frequencies below 35Hz (probably closer to 40 or 45Hz on a 15) before the sub, so we use a 40Hz high-pass filter (passes signals higher than the rating) before the sub so it doesn't get frequencies it can't handle well. Then we want to make sure the region between the sub/top is as clean as possible, so we need to pick a crossover point to pass signals to the top only and for a 15" sub and 12" top, that's probably around 100Hz. So we set up a crossover between those 2 where we ramp down the signal to the sub as we approach the 100Hz mark and start ramping it up to the top at the same time.

This chart shows a similar crossover and high-pass internal to say the 12" top, where it's high-passed around 50Hz and crossover point is around 2,000Hz.

1586441285889.png

The actual frequencies for a crossover will vary, but in general I would start with 90Hz for a 15" top, 100Hz for a 12", 120Hz for a 10" and somewhere between 140-150Hz for an 8".
 

TJS

GetSomeJuJu
Nov 8, 2018
315
322
54
Ankeny, IA
www.jujulab.rocks
For any driver or speaker, the goal is to push the appropriate frequencies to the appropriate driver(s). For a sub and top combo (we'll forget about what's internal to the top), that means sending the subs the frequencies between say 35Hz and 150Hz (depending on size, type, etc.) and the tops get the signals above say 80Hz to 150Hz. The trick is maintaining a consistent frequency response and output level when the frequencies fall close to the region between the sub and top.

So let's assume we have a 15" sub that does say 40Hz-140Hz and a 12" 2-way top that's rated for maybe 60Hz-16KHz (or whatever).

Starting with the input signal, we want to eliminate frequencies below 35Hz (probably closer to 40 or 45Hz on a 15) before the sub, so we use a 40Hz high-pass filter (passes signals higher than the rating) before the sub so it doesn't get frequencies it can't handle well. Then we want to make sure the region between the sub/top is as clean as possible, so we need to pick a crossover point to pass signals to the top only and for a 15" sub and 12" top, that's probably around 100Hz. So we set up a crossover between those 2 where we ramp down the signal to the sub as we approach the 100Hz mark and start ramping it up to the top at the same time.

This chart shows a similar crossover and high-pass internal to say the 12" top, where it's high-passed around 50Hz and crossover point is around 2,000Hz.

View attachment 50798

The actual frequencies for a crossover will vary, but in general I would start with 90Hz for a 15" top, 100Hz for a 12", 120Hz for a 10" and somewhere between 140-150Hz for an 8".

Thanks Steve!
So do I need to manually set the crossover and high pass filter in both the sub and top no matter what? Are there factory settings typically already set for this sort of thing? For example, if I buy a QSC 18" or 15" sub to go with my QSC K12.2 do I still need to adjust settings since each sub and top are still "different" in their specs even though it's the same manufacturer OR does all of this actually only come into play when you're mixing brands between subs and tops?
 
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steve149

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Thanks Steve!
So do I need to manually set the crossover and high pass filter in both the sub and top no matter what? Are there factory settings typically already set for this sort of thing? For example, if I buy a QSC 18" or 15" sub to go with my QSC K12.2 do I still need to adjust settings since each sub and top are still "different" in their specs even though it's the same manufacturer OR does all of this actually only come into play when you're mixing brands between subs and tops?
Depends ...

Normally you "split" the signal via a crossover in one of the boxes and send the modified signal to the other (usually done in the sub). In the case of some of the QSCs, you can also split the signal in the top and only send the low part of the crossovered signal to the sub. It's cleaner wiring wise if you do it in the sub so you aren't sending 2 signal cable up to the top.

As far as settings .. it depends on a series of variables. If the units have settings for the other component, use that. If not, you can normally accommodate most brands with the built-in x-overs of most current DSPs without needing an external unit (crossover or driverack).
 
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steve149

Shine on you crazy diamond
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Ah, I see. I think that makes sense. A lot to learn sometimes...We have to wear many hats to do a passion :pillbiggrin:
Still a lot easier now than when everything was manual. Or you can be like Mix and just ignore the proper things to do .. :)