PA novice!

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student with too much free time!
Member Since: Apr 17, 2006

Hi people,

I've just bought a PA for playing small venues, with typically around 100 pax.

The set up I have is a Carlsboro Cobra 1100 (100w RMS @ 4 ohms) a pair of SoundLab P115BB speakers (150w RMS 8Ohm) I used it last night in front of about 90 people with a small band and thought it sounded pretty good.

I also have have a set of 250w Nippon speakers sitting idle at home.

My questions are......what is the maximum no of people I could play to with this set up?

Can I use both sets of speakers from a single amp.......the amp only has one set of outputs, but the sondlab speakers have two jack on the back, assume the second is for another set of speakers? Would using the second set of speakes be of any benefit whatsoever?!

Thanks in advance!

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The Czar of BS
Since: Dec 31, 2007

May 31, 2010 12:55 pm

This is not a question of wattage. This is a question of SPL and coverage.

In other words, how loud they are, and what the pattern of the box is. One thing that I harp on here, is that wattage has no bearing on how loud a box will be. Wattage is just how much power it takes to run a box.

Now, if your boxes will just to about 105 dB. and has a coverage pattern of 80 x 30 or greater. Then you should be fine. If these measurements are smaller, then you need to think about adding another box to each side. But, your amp is even to small for the boxes that your running now. I would suggest getting another amp that has a slightly higher rating then all of the wattage added together of each of the boxes that you plan to have on each side of the amp.

student with too much free time!
Since: Apr 17, 2006

May 31, 2010 01:51 pm

Hi Rob, thanks for the reply.

So ideally I should be looking at am amp with 400w or more to run both sets of speakers?

At the moment I can't really afford to do much more electronics shopping...With the set up I have at the moment am I likley to damage any of the equipment? Getting a decent volume out of the amp meant that the amp was at about 3/4 of its max output.

I have no idea what the coverage of the boxes are, or what the dB level is as I seem to have lost the user guide......cant seem to find a soundlab website either which is weird!

The Czar of BS
Since: Dec 31, 2007

May 31, 2010 04:17 pm

Yeah, sorry to put it to you like that. But, you are a little under powered just for the two speakers that you have now.

You should always have just a little more output then your speakers are rated for. This will help ensure that you won't square wave your speakers.

student with too much free time!
Since: Apr 17, 2006

Jun 01, 2010 02:23 pm

So I've been having a browse online at what's out there......and to be honest the more I look the more I realise I have no idea what most of the terminology surrounding PA systems means! Can you point me in the direction of any online tutorials that might help to educate me a little!?

Found a Cloud VXT 750 going cheap on eBay....
Here's a link to the user manual:

Is this the sort of thing I should be looking at or do I still need more power? Would it power both sets of speakers? Do I even need to use both sets of speakers?

I'm training in the army, and have stared a band within my platoon.....we're only going to be playing fairly low level gigs, however some of the halls here are quite large, so I'm thinking that a little bit of volume would be quite good.


The Czar of BS
Since: Dec 31, 2007

Jun 01, 2010 02:46 pm

If you can find that 1200, that would be better suited to your needs.

You have a speaker that handles 150 watts + a 250 watt speaker that you wish to add. Total wattage is 400 watts.

Now I am going to assume that the Nippons are 8 ohms as well? If that is the case, then you need an amp that can provide 400 watts at 4 ohms.

I don't know of any other web site out there for this type of information other than here. The only thing that I can suggest is the Yamaha Sound Engineering Handbook. It's about $35 US. And will tell you everything that you want to know about live set ups.

Since: Apr 03, 2002

Jun 01, 2010 02:50 pm

I remember years and years ago I bought a book from Radio Shack of all places, that explained the math and logic behind speaker construction, cabinet size, porting size and length, how ohms and wattage are figured and distributed around the speakers in the cab and all was a relatively inexpensive book, and obviously isn't complete because the complete science could fill volumes, but I found it to be a great resource, used it to build a half dozen or so speakers, choose components, select materials, figure sizes and such and they sounded pretty darn good.

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