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[Luke Geis]

The subs you have are solid performers, but there are only two of them. It is a huge ask to have two subs smack your pants. With another set of subs, you will find that you get that little bit closer to what you are looking for. Not knowing exactly how much more you want, how many more pairs of subs you need is a big Q mark. Usually doubling whatever your current count is will get you just enough to go from meh to OK. If you want hell F-N yeah, you will need multitudes more.

For a budget amp, the Behringer NX series is pretty darn good. Hard to beat for the money for sure. Although asking 1 amp to do enough work to make you go hell yeah is again a huge ask. The general rule of thumb is to have at a minimum, 2X the amount of power allocated to subs as you do to your mains. So if you have 3k watts for tops, you want at least 6k for subs. Which means you need the number of subs that can eat that amount of wattage.

[Mike Sircee]

The subs you have are solid performers, but there are only two of them. It is a huge ask to have two subs smack your pants. With another set of subs, you will find that you get that little bit closer to what you are looking for. Not knowing exactly how much more you want, how many more pairs of subs you need is a big Q mark. Usually doubling whatever your current count is will get you just enough to go from meh to OK. If you want hell F-N yeah, you will need multitudes more.

For a budget amp, the Behringer NX series is pretty darn good. Hard to beat for the money for sure. Although asking 1 amp to do enough work to make you go hell yeah is again a huge ask. The general rule of thumb is to have at a minimum, 2X the amount of power allocated to subs as you do to your mains. So if you have 3k watts for tops, you want at least 6k for subs. Which means you need the number of subs that can eat that amount of wattage.

So you're saying I would need to run a single NX6000 amp per VRX918 sub?

[Jeff Lelko]

So you're saying I would need to run a single NX6000 amp per VRX918 sub?

I think what Luke is saying is that you need more subs for a properly balanced system.  To address your original question, I'd buy more of the same versus tossing in yet another different product series to the mix.

Laying out the tops this way the pattern would now be 50º horizontal / 90º vertical.  placed 8' off the ground with a slight downward pitch.

I've seen this done before and it won't really help you.  To begin with there's a lot of acoustic energy that'll end up firing in useless directions.  Beyond that, you're still going to have comb filtering issues among other problems.  You really want to get all your speakers as close together as possible and arrayed so as to minimize overlaps in coverage.  I personally wouldn't have a gap between subs.  If it were me I'd just put a single speaker on each end of the truss angled outward and be done with it.  If the PRX boxes aren't enough output then replace them with something that is.  It might sound counterintuitive, but adding more speakers into the mix won't necessarily help and can sometime be a step back.  Good luck!

[Luke Geis]

What I am saying is that if your current subs require 3,000 watts between them ( they can't and or don't need any more wattage than that ), then to get to the next level, you would need another pair of the same subs that also utilize another 3,000 watts. This would mean you have double the subs and double the power that you currently have.

You can see how trying to get a little more thump and bump can get really expensive. Another pair of subs and another amp is not exactly cheap. If you need more than that to get a smiley face, then you would need to double up your subs and your power again! Remember I said in general 2X is needed, but oftentimes it will take 4X to 6X the amount of power for subs over that of your mains to get the impact you really want.

For example and with easy math, let's assume you have two mains that require 500 watts each ( so you have 1000 watts of power for them ). Now let's assume you have two subs that also each require 500 watts apiece, for an equal 1000 watts of power as the mains. You will likely need at the very least another pair of subs that you have yet another 1000 watts deligated to, for a total of 2000 watts and 4 subs. You may need 4X the initial number to get the thump and bump you need though? To go to the next logical step up, you would double down again. So you would have 8 subs and 4000 watts of amplification for those 8 subs.

You can see now how quickly your budget and your truck will get used up. This is why we generally advocate buying the most expensive subs you can. The cost of the sub generally aligns with its output. A sub with 3-6db more output will gain you a lot of ground, perhaps allowing you to use half the number of subs of a lower cost and less efficient sub.

[Mike Sircee]

What I am saying is that if your current subs require 3,000 watts between them ( they can't and or don't need any more wattage than that ), then to get to the next level, you would need another pair of the same subs that also utilize another 3,000 watts. This would mean you have double the subs and double the power that you currently have.

Ok, think I'm following you now.  We are more interested in active speakers just because of the application and use.  The two passive vrx918s subs are the exception.  So what are your thoughts, if we were to double up as you said, then we would be doing that by adding the SRX828sp.  Of course there are more expensive Subs out there. I was also looking at the Bassboss VS21.  Definitely not cheap at $4,599 ea and not even sure if it would play well with the vrx subs.

Yeah, I had no idea I would be opening up a huge can of worms when I jump on board this project.

[Mike Sircee]

I've seen this done before and it won't really help you.  To begin with there's a lot of acoustic energy that'll end up firing in useless directions.  Beyond that, you're still going to have comb filtering issues among other problems.  You really want to get all your speakers as close together as possible and arrayed so as to minimize overlaps in coverage.  I personally wouldn't have a gap between subs.  If it were me I'd just put a single speaker on each end of the truss angled outward and be done with it.  If the PRX boxes aren't enough output then replace them with something that is.  It might sound counterintuitive, but adding more speakers into the mix won't necessarily help and can sometime be a step back.  Good luck!

Thanks Jeff,    I appreciate the feedback..... we're evaluating the entire setup, of course there's always the issue of $$$. The output of the four prx612's sounded great.  Of course we didn't have anyone there with Sound engineer ears ;-) But for the average person partying at an outdoor event the output was sufficient for our budget. But if we are able to achieve the same output level with two tops and not have the the sound issues explained in the responses then I would be open to making those changes.
 I don't think we would have a problem selling the four prx612's. We just picked them up w/ flight cases a few weeks ago and they're in great condition, I'm sure we can get $1,700 for them and would apply that to something more compatible, like two SRX812 tops.

[Mike Sircee]

What I am saying is that if your current subs require 3,000 watts between them ( they can't and or don't need any more wattage than that ), then to get to the next level, you would need another pair of the same subs that also utilize another 3,000 watts. This would mean you have double the subs and double the power that you currently have.

Ok I see what you're saying.
Are you going by peak or continuous watts?

[Matthias McCready]

Mike

What SPL are you trying achieve here?

What is the area you are trying to cover?

[Luke Geis]

Peak or continuous, it doesn't matter. If you have an amp that will provide 3,000 watts to two subs regardless of their wattage rating, and you have the same 3,000 watts going to your mains, you will need at the very least to double the amount of subs and the power you have for them.

Going down the powered road: Let's assume you buy a pair of SRX-828 subs and a pair of SRX-815 mains. They have the same total power each. Each model touts a 2,000-watt peak amplifier. So if the one pair of 828's do not do it for you, you will need yet another pair, or possibly 4X as many of them.

Watts do not = Volume. The difference between 2,000 watts and 1,500 watts with the same speaker is about 1db.

Eluding to the question Matthias asked, there is a way to mathematically guesstimate how much amplifier power you need based on the speaker specs you have to come to a potential peak SPL level ( volume ) and at what distance you can achieve a desired SPL. If you don't know what volume you want at X distance, then looking at watts, speaker sensitivity, and a number of subs or speakers is of little use. Most " sound guys " go by gut if you will. They use X gear once, twice, several times and get an idea of what it will do. They then use that experience to guess if what they have will do the task they are asked to do. This is often what gets them into trouble. They can bring too much and waste time, energy and destroy the aesthetics of an event, or they can bring too little and not make anyone happy either way.

Doing sound is more about physics more so than " I think I can ". A good system designer can tell you pretty much exactly what you can or can't do with what is available, and integrate a system to perform to an above-average standard without doing much work at all. Doing a lot of the math and planning ahead of time can save you money on purchases, setup time, labor, storage, and transportation costs. Heck, even insurance costs can be reduced by smart purchases and more methodical systems design.

I can't tell you if you need 2X or 4X more subs and if adding X sub to your current setup will achieve what you desire. I can tell you that if what you currently have isn't enough for you, then you will need more. How much more? Well, that depends on what your target is. Knowing the goal is a large part of the equation. If you don't know what the goal is, then it becomes a moving target. And what you feel today may not be what you feel tomorrow.

So to shorthand this. You can do a couple of things. If you don't have the amount of bass you want, you can reduce the level of the mains to acquire the balance/ratio of bass you desire, but your volume limit will be dependent upon what the subs will allow. If the subs start clipping, you have no more volume to give. Or you can throw more subs at the problem. Ideally, you want the same brand and model, but that isn't always in the budget. Having different brands and models of speakers makes calculating the actual gains a little more challenging, but you can come to a reasonable expectation.

[Mike Sircee]

Mike

What SPL are you trying achieve here?

that's a loaded question for a guy who's not a sound engineer. I can tell you that I have gained quite a bit of knowledge and have a new found respect to the guys behind the curtain. 
 
The coverage area would be 30'w x 40'L .  We also found that with the DJ's up on the top deck, 10', people tend to dance and gather a good 10' from the base of the stage. right about where they can see the DJ, opposed to looking up at the bottom of the decks. with the 4 prx612's the volume levels were perfect. Just was missing that extra umf on the lower end and Luke Geis pretty much explained why that is.

There was a lot of talk about comb filtering, yet I may have an untrained ear and have a bit of tinitus from years working in the nightclub industry,  after a lot of reading on comb filtering I haven't really noticed it. We will be setting up the system this week and will run several tests to now that I have a better understanding.

[ProSoundWeb Community]