Question about PA system

Eggman

Hello.
I would like to know how/if I could add some subs/bass bins to my PA system.
I'll start by describing it. It's a passive system. We have a Behringer Europower PMX2000 mixer. On the back it says:
Stereo mode: 250 watt at 4ohm, minimum 4 ohms
Bridge mode: 500 watt at 8ohm, minimum 8 ohms
Then there are three speakon outputs. One says right/mono main, the second one says bridge, and the third says left/monitor. We currently have two Studiospares 248210 speakers. Here are the details for the back of one speaker:
It has a jack input which we use. Underneath this are two speakon inputs side by side, they are labelled as full range inputs. It says max power: 500w peak, 250W RMS(PROGRAM). Impedance: 8OHMS, Crossover 2000Hz
If I want to connect some subs:
What sort do I need? How would I connect them? What watts/ohms should I get?
I can't say I fully understand any of the information I provided , so any help would be much appreciated!  Thanks.
I can try to provide pictures if that would be helpful.

John_P

You have a few options depending on your budget and how much power you need.  

1 Add some passive subs that have a crossover built in so you go out of the mixer amp into the sub and out of the sub to each top speaker. 
Easy but you don’t get a huge amount of power. 

2 Add some active subs and go from a line out on the mixer amp to the subs and connect the top speakers as normal from the amp.     The down side is the top speakers are still getting some of the bass frequencies so the system isn’t as efficient as it could be.  

3 You could keep your mixer amp but use it just as a mixer and add a bigger power amp and then connect to passive subs and your current speakers like the first option.  

4 Keep the mixer amp as a mixer only and add active subs and tops.  

Sell it all all and buy a separate desk and active subs and tops - this is how I run mine so I can add in as many speakers as I need for the gig - last weekends gigs used one sub and two tops and another I used 6 subs and 4 tops.   

There are probably several other ways but those are the obvious ways that cone to mind.  

Eggman

Thank you very much for explaining it so simply. As I said, I don't really understand this stuff, so that's really helpful. I like suggestions one and two. I am not very keen to sell it, as we only bought it recently and it's quite good so far.

jpfamps

In my view the major advantage of having subs is that the bass can be kept out the tops, so the tops can amplify the vocals more clearly; adding subs without being able to roll the bass off into the tops could actually make your live sound worse.

Why did you want to add subs anyway?

ICBM

The amp looks like essentially a copy of the Peavey XR684 I use, with one more channel and very slightly more power.

I do John_P's '2' - I run mine with a pair of Celestion 1x10" cabs and a single Wharfedale 250W powered sub bass bin, which I simply connect to the main/mono output and let the frequencies take care of themselves. (With monitors driven from a separate small power amp, from the monitor mix output.) It works fine for the sort of level of gig you'll be using a system this basic at - it's not technically correct or quite as efficient as it could be, but when you get to the point that sort of thing really matters then you need a bigger and more sophisticated system anyway.

If you aren't using monitors, you could get a better mix by using the monitor output to send the bass instruments to the sub(s) and take the 63Hz sliders right down to fully cut on the main mix, which would stop the lowest frequencies getting to the top cabs.

You may only need one sub - they're not directional - but two would give you a self-backup system and allow you to mount both top cabs on the subs with simple poles, and not bother with stands.

(NB, I probably wouldn't get a Wharfedale - I made mine from two dead ones I was given! They are not renowned for reliability...)

Eggman

In response to jpfamps: I want to add subs because in my band we would like to mic up the kick drum, to give the sound more fullness/force. Also, it's sometimes necessary to mic up the bassist's amp (fender rumble 25), particularly at slightly larger gigs and outdoors. We occasionaly play with a keyboard, which makes the vocals sound a bit weak when it's all through the PA.

ICBM- thanks for your detailed response. We aren't using monitors (we tend to get by without, and at larger gigs we use the provided PA, not ours), so I like your second suggestion, especially  as I coild get a better mix.

What brand would you recommend? Is it a good idea to buy used (cheaper) or is that considered risky?

ICBM

Your bassist needs a bigger amp! The Rumble 25 is a very nice... home practice amp . I’m astonished it can even be heard without being mic’ed at any gig, to be honest.

If you’re not using monitors, definitely get a powered sub (or two) and run them from the monitor output with just the bass, keyboards and kick drum going through them, and cut the 63Hz in the tops.

I’m not actually that familiar with currently available brands, but I think your best plan is to buy a pair secondhand - cheaper, and if one fails you’ll get through the gig on the other. (Unless you’re unlucky, like the previous owner of my Wharfedales! And even those didn’t fail at the same time.)

Actually even Wharfedales are probably OK, and they’re fairly common and cheap.

jpfamps

Eggman said:

In response to jpfamps: I want to add subs because in my band we would like to mic up the kick drum, to give the sound more fullness/force. Also, it's sometimes necessary to mic up the bassist's amp (fender rumble 25), particularly at slightly larger gigs and outdoors. We occasionaly play with a keyboard, which makes the vocals sound a bit weak when it's all through the PA.

ICBM- thanks for your detailed response. We aren't using monitors (we tend to get by without, and at larger gigs we use the provided PA, not ours), so I like your second suggestion, especially  as I coild get a better mix.

What brand would you recommend? Is it a good idea to buy used (cheaper) or is that considered risky?

You'll need to keep any bass instruments out of the tops to keep the vocals clear.

What is your budget?

Eggman

ICBM said:

Your bassist needs a bigger amp! The Rumble 25 is a very nice... home practice amp . I’m astonished it can even be heard without being mic’ed at any gig, to be honest.

If you’re not using monitors, definitely get a powered sub (or two) and run them from the monitor output with just the bass, keyboards and kick drum going through them, and cut the 63Hz in the tops.

I’m not actually that familiar with currently available brands, but I think your best plan is to buy a pair secondhand - cheaper, and if one fails you’ll get through the gig on the other. (Unless you’re unlucky, like the previous owner of my Wharfedales! And even those didn’t fail at the same time.)

Actually even Wharfedales are probably OK, and they’re fairly common and cheap.

I like this idea. On ebay there are a few old, beaten up subs that look a bit shabby. They're often unbranded. Would it be a bad idea to get something like this?

For our smaller gigs (audience of one hundred and under) the rumble 25 manages on full volume. But the drummer isn't extremely loud, and I usually play through my Champion 100 at gigs. What size/watts bass amp would you recommend? We don't want anything too large. 

ICBM

100W with a single 15” speaker or 2x10” is about the minimum I would consider a giggable bass amp in almost any context. There are some modern amps which get a lot of volume out of very small speakers and cabs, but they’re more powerful (and expensive). The bigger and more efficient the cab, the less power you can get away with, but anything much under 100W is still going to struggle to give a good clean bass sound.

Really cheap PA gear is usually a waste of money, it will inevitably break even if it sounds OK. Wharfedale would really be the lower end of what I would bother with.

Eggman

We've got an old venus gem vg20 transistor amp, it's italian and from the 1970s. It's very loud, but has a few problems.

ICBM

Eggman said:

We've got an old venus gem vg20 transistor amp, it's italian and from the 1970s. It's very loud, but has a few problems.

Those are great - I had the reverb version a long time ago. If you just turned everything up full it sounded exactly like The Good The Bad And The Ugly .

It's actually a transistor preamp with a valve power amp. I wouldn't describe it as very loud though... I think we must have different ideas of what loud is, if you can gig with a 25W bass amp .