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Author Topic: Recommended Sub amp for my system?  (Read 20043 times)

Luke Geis

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Re: Recommended Sub amp for my system?
« Reply #50 on: November 14, 2017, 09:10:22 PM »

I don't think 3 per side of the SB100's will be particularly better performing than only 2 per side. It will take a minute load off the subs system as a whole, with of course the high expense. It takes 2X the power or 2x the number of boxes ( with the same power each ) to increase output by 3db. Some will say that adding another set of 4 subs would add 6db, but that is dependent on a couple factors.

The hard truth is that the subs you currently have are ( on paper at least ) more efficient and louder than the SB1000's would be. At this point if you must have more, you would probably be better off at investing in power amps. With an amp that is pushing 2x the wattage you would still be in a safe place and you would get +3db.

I was saying before that you can get tricky and eek a little more out of the subs if you really want to. Sounds like you may be running subs on an aux and doing so is one such trick. The next thing would be crossing the subs over at a slightly lower frequency to save some headroom, but that is dependent upon where you are currently at. The last thing is compression / limiting. You can squash the signal going to the subs a little to reduce the crest factor which will give a higher perceived output and allow a little more output before clipping.

I have a saying though as a caveat. " Too much of a good thing is still too much ". If you go trying to eek every last drop out of the subs to get as close to that supposed 141db per box, you stand that much more of a chance of damaging them. I think that you can realistically get the continuous 135db per box out of them. This would give you a theoretical real world peak SPL of around 144db - 147db!!!!! Now this would be cooking with gas.

My prescription for this would be to run subs on an aux and run a crossover somewhere between 60hz and 80hz ( probably closer to 80hz since the tops are only good down to 65hz ). Next would be to get a set of amps that can push 4000 watts per channel at 4 ohm's!!!! The amp will be a tough one since not many can do that affordably. Then using a bit of compression / limiting on the aux subs signal, you can get the crest factor down enough to gain another 3db of perceived SPL. Between all that you should be able to get close to 135db per sub in real world output at 1 meter! While I won't guarantee that YOU will, I know it should be at least possible with a competent user.

These numbers DO NOT factor distance losses, so keep that in mind. Also be aware that separating the subs as you have in the picture above will reduce potential output at least in some of the listening area. There are several deployment methods and all have a trade off. If you need more than what 4 2X 18" subs can provide for a hobbyist type job, I would say you may as well quit your day job and just go head on into sound support. By the time you invest the money and the typical setup energy, you will never get paid enough to do it as a hobby.
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Rob Spence

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Re: Recommended Sub amp for my system?
« Reply #51 on: November 14, 2017, 10:56:52 PM »

I got a PL6.0 available


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Scott Holtzman

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Re: Recommended Sub amp for my system?
« Reply #52 on: November 14, 2017, 11:35:10 PM »

GASP... I'll need more than 4 - SB1000? Holy smokes, I see a divorce in the future. ;)

I thought going with 4 (2 per side) SB1000's was going to sound great or at least a bigger improvement over my current TRX sub cabs. Please do keep in mind that 70-80% of the shows I provide sound for, I ground stack my current subs then stack 1 to 2 mains per side.

Would you recommend 3 SB1000's per side to keep up with the mains then?

They are meant to couple in groups of 4.  I think 4 aside will get you close to where you want to be. 

They stack well in storage <g>  You get four guys, get a corner up and then push to stack (this is defacto with any big sub). 

You have to double to get your next jump up.  Going fro 2 to 3 won't be noticeable.  Going from 2 to 4 is.  Especially with these subs that the mouth opening is designed to couple in groups of four.
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Scott AKA "Skyking" Holtzman

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Mac Kerr

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Re: Recommended Sub amp for my system?
« Reply #53 on: November 15, 2017, 12:13:52 AM »

They are meant to couple in groups of 4.

Where is this information from? AFAIK the EAW subs that are meant to be used in blocks of 4 are the bass horn series, the now legacy KF940, BH760, and LA400.

Mac
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Stephen Kirby

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Re: Recommended Sub amp for my system?
« Reply #54 on: November 15, 2017, 12:31:45 AM »

The Sb1000 is more of a bandpass cabinet, but sort of looks like a tapped horn.  Even real tapped horns don't really couple the way LA400s or Labs do.
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Scott Holtzman

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Re: Recommended Sub amp for my system?
« Reply #55 on: November 15, 2017, 04:16:15 AM »

Where is this information from? AFAIK the EAW subs that are meant to be used in blocks of 4 are the bass horn series, the now legacy KF940, BH760, and LA400.

Mac

Mac is right, it is the KF940 I had in mind and it doesn't even look the same. 

With the 4 dual 18's and the MX processor you will be more than pleased.

Sorry for the confusion.
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Scott AKA "Skyking" Holtzman

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Pat Semeraro

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Re: Recommended Sub amp for my system?
« Reply #56 on: December 23, 2017, 11:57:00 PM »

Sam, may I make a suggestion? 

With no measuring equipment except your ears, play some pink noise through the 650s at low/comfortable level and walk in front of them back and forth.  (Too loud and you'll load up the room which makes this test more difficult.) You should hear no change in sound as you move between the two top boxes.  With the 650z cabinets, EAW recommends 12" between them in front with the rears touching - in practice that is a good place to start.

From the picture it looks like you have the two top boxes mostly pointing in the same direction.  If that's true, then you will hear significant comb filtering as you walk side to side in front of them.  Rotate the fronts away from each other until the pink noise doesn't change as you walk back and forth. 

Two 650s over two double 18's is a very useful combination and I've done it many hundreds of times.  In practice I've achieved smooth box to box hand-off by pointing the outer box straight ahead and rotating the inner box 25 to 30 degrees to the center, it usually end up being around 10" to 12", just as EAW suggests.

This only takes a few minutes and could improve your house sound more than you might expect.  If no front-fills are being used then a more aggressive angle to the center on the inner box and adjust as necessary on the outer box would give more even coverage on the dance floor area.  Season to taste...

*caveat* My use of KF650z has always been tri-amped via UX8800, which gives very clean and distinct pattern edges.  Non "z" boxes, bi-amping and non UX8800 processing might give different results, including less defined pattern edges which would be more forgiving with cabinet placement.

Cheers,
Pat



Here's a pic from one of our events in Northern California recently where I ran the 2 EAW KF650's and 2 TRX sub per side.


« Last Edit: December 24, 2017, 12:12:03 AM by Pat Semeraro »
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Mark Wilkinson

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Re: Recommended Sub amp for my system?
« Reply #57 on: March 28, 2018, 08:59:52 PM »



If you're good with a soldering iron, I suggest ordering the PL2 capacitors from QSC.  (PLX is same amp but with half of the power supply capacitance) The tone is absolutely more solid and the power draw is more even.  You'll get a few hundred extra watts of output each amp as a bonus.  Costs very little per amp, and makes a big difference.



Hey Pat, great tip.
Which PL2 model should I ask QSC about, to get the the caps?   Or do you know the cap values that could be obtained elsewhere?   
Thx,  Mark
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Pat Semeraro

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Re: Recommended Sub amp for my system?
« Reply #58 on: March 30, 2018, 03:05:53 PM »

Hey Pat, great tip.
Which PL2 model should I ask QSC about, to get the the caps?   Or do you know the cap values that could be obtained elsewhere?   
Thx,  Mark

There are three cap values - 200v first stage, then 55v and 90v in the second stage.  Single rail models use only the 90v.  Lower powered models also skimp out on the 200v caps - I always fill empty parking spaces in the 200v section also.   PLX3402 = PL236 but PLX version has strangled power supply.  It seemed impossible that mod could make any difference but in practice it was a big deal.  I converted many of the cx1102 version to PL236 spec and they would power dual 18" subs at war volume pretty well if the AC was stout.  (Don't try that on a 15 amp circuit...)
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Mark Wilkinson

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Re: Recommended Sub amp for my system?
« Reply #59 on: March 31, 2018, 09:53:20 AM »

There are three cap values - 200v first stage, then 55v and 90v in the second stage.  Single rail models use only the 90v.  Lower powered models also skimp out on the 200v caps - I always fill empty parking spaces in the 200v section also.   PLX3402 = PL236 but PLX version has strangled power supply.  It seemed impossible that mod could make any difference but in practice it was a big deal.  I converted many of the cx1102 version to PL236 spec and they would power dual 18" subs at war volume pretty well if the AC was stout.  (Don't try that on a 15 amp circuit...)

Gotcha, and thx.

I peered into a PLX3402 and a PL340, and see the 3 banks of caps.
I see the 3402 uses caps of 2200uf for 200v, and 470uf for 90v & 55v.
..and the  pl340  uses 3300uf for 200v, and 1000uf for 90v & 55v.
Same number of caps on all banks, both boards....boards look very similar.

Do you think it would be a worthwhile benefit to replace just the 6 big 200v caps?
That seems a lot more doable than also changing the 20 caps for 90v & 50v....
I have no issues with the plx3402 other than it dropping out on intense sub peaks...

Curiosity also peered into a PL380....it has two 6-cap banks of 3300s for 200v, but no other banks....
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Re: Recommended Sub amp for my system?
« Reply #59 on: March 31, 2018, 09:53:20 AM »


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