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PGibson



Joined: 12/02/13
Posts: 9
PA speaker advice needed
      #1033148 - 12/02/13 12:57 PM
I am a teacher and we have a band at school playing oldies mainly from the 60s and 70s.

At present we only put microphones through the pa. The mics go into an Allen & Heath PA12CP powered mixer. In the future I would like to put two guitars through the pa - not the bass guitar - to keep the stage volume down.

From the mixer an unpowered signal goes to my colleague's pa system (amp, sub and 2 tops). Also an unpowered signal is sent to powered monitors. At present the twin amps inside the CP12CP are not being used.

We have a bigger event coming up in a marquee (30m x 9m) and I reckon we will be underpowered on the pa. My thought is to get two passive pa speakers to connect to the PA12CP powered mixer to supplement our present pa.

The PA12CP delivers 2x500W at either 4 ohms or 8 ohms (switchable and full power is delivered at either 4 ohms or 8 ohms).

What I would appreciate is advice on the choice of speakers.

I am looking at 12" or 15" speakers. I had thought of getting two 8 ohm speaker cabinets - I could always get two more speakers at a later date and run two each side at 4 ohms. I had also thought that, as many cabinets are rated in the 250W to 350W range, I would necessarily be keeping the PA12CP well away from 'full blast'.

Ideally I would like to spend £250 to £400 on a pair of speakers, and ideally I would like them to not be too heavy: I am in my early sixties and veer away from heavy lifting nowadays.

I have had a good look at what's available (Wharfedale, Alto, Peavey ...) and am not clear on the best choice. Any advice would be much appreciated.

Thank you in advance.
Paul


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dickiefunk



Joined: 17/06/05
Posts: 2327
Loc: Cornwall, UK
Re: PA speaker advice needed new [Re: PGibson]
      #1033156 - 12/02/13 02:08 PM
I have heard good things about the Alto speakers being surprisingly good for the money! They have had excellent reviews and when I was inquiring at a few stores about buying a new rig last year some of them recommended the Altos over a few of the other brands costing at least twice as much!

I've got an Alto TS112a coming later today which I intend to use primarily as a monitor/keyboard amp and will eventually be looking to add a second to have a spare small pa which can be used for dry hire.

If you're using the speakers mainly for vocals then 12" speakers are generally better suited than 15" (though my Yamaha DXR15's have great vocal clarity).

The passive Alto TS112's cost around £299 for a pair and the actives are £438 a pair. If I were buying I would prefer to go active because I find them more useful. Also, if your amp was to ever go down on a gig it would be game over whereas if the amp in one active speaker went down you could still just about get through the gig with the other speaker!

The passive Alto TS115's cost the same as the TS112's at the moment (£299 pair) and the actives cost £499.

--------------------
www.richardpenrose.com


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chris...
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Joined: 12/03/03
Posts: 4616
Re: PA speaker advice needed new [Re: PGibson]
      #1033179 - 12/02/13 04:59 PM
Quote PGibson:

In the future I would like to put two guitars through the pa - not the bass guitar - to keep the stage volume down.



I'm slightly skeptical whether it makes sense to put electric guitars thru a PA this small. But I could be wrong.


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Sam Spoons
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Joined: 23/01/03
Posts: 1158
Loc: Manchester UK
Re: PA speaker advice needed new [Re: PGibson]
      #1033180 - 12/02/13 05:00 PM
Do you mean you want to mic the guitar amps or input the guitars directly into the PA?


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PGibson



Joined: 12/02/13
Posts: 9
Re: PA speaker advice needed new [Re: Sam Spoons]
      #1033184 - 12/02/13 05:23 PM
I was planning to mic the guitar amps, not input directly into the pa. I play lead guitar through a Fender Blues Junior; it may only be 15W but it has been plenty loud enough for a school hall with an audience of around 250. However, I am sure I would hear the vocals through the foldbacks much better if I reduced the volume of the amp behind me, hence the plan to mic the amp. I was thinking of cutting the volume of the guitar amp by, say, 40% and using the pa to get the volume right for the audience. Am I talking daft?


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Sam Spoons
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Joined: 23/01/03
Posts: 1158
Loc: Manchester UK
Re: PA speaker advice needed new [Re: PGibson]
      #1033195 - 12/02/13 06:30 PM
Quote PGibson:

I was planning to mic the guitar amps, not input directly into the pa. I play lead guitar through a Fender Blues Junior; it may only be 15W but it has been plenty loud enough for a school hall with an audience of around 250. However, I am sure I would hear the vocals through the foldbacks much better if I reduced the volume of the amp behind me, hence the plan to mic the amp. I was thinking of cutting the volume of the guitar amp by, say, 40% and using the pa to get the volume right for the audience. Am I talking daft?




No, you're talking sense, (I use an 18 watt 1x12 valve combo) keep the amp in it's it's sweet spot and mic it up. Work to the drums onstage volume and you won't go far wrong (as long as he's not a Metal God Drummer). I nearly always mic the guitar amp just to get a better spread of sound, 1x12 combos are vey directional, also put it on a chair/stand pointing at your ears. Trying to have just vocals in the monitors if possible (I'd guess that's what you're already doing), helps to keep the FB clean too.


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PGibson



Joined: 12/02/13
Posts: 9
Re: PA speaker advice needed new [Re: Sam Spoons]
      #1033233 - 13/02/13 07:26 AM
Thank you for all the advice people have given so far.

Can I ask please for comment on connecting a pair of 12" speakers which might be rated at 200W or 250W RMS to the Allen & Heath powered mixer which is rated at 2 x 500W. Is it risky to think in terms of using the above combination by keeping the output of the A&H amps within bounds?

Secondly, if others have recommendations on the choice of speakers I would be grateful to hear from you.

Paul


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Mike Stranks
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Joined: 03/01/03
Posts: 3709
Loc: Oxford, UK
Re: PA speaker advice needed new [Re: PGibson]
      #1033237 - 13/02/13 09:13 AM
Quote PGibson:

Thank you for all the advice people have given so far.

Can I ask please for comment on connecting a pair of 12" speakers which might be rated at 200W or 250W RMS to the Allen & Heath powered mixer which is rated at 2 x 500W. Is it risky to think in terms of using the above combination by keeping the output of the A&H amps within bounds?

Secondly, if others have recommendations on the choice of speakers I would be grateful to hear from you.

Paul



No; you'll be fine. The usual rule-of-thumb is that the amp should be rated at about twice the rated power of the speakers so your set-up is spot-on. However, there are some who don't agree with this as has been shown many times in these forums and may well be again.

You're more likely to damage speakers by using an underpowered amp driven too hard rather than an overpowered amp putting too much power into them. It's all to do with amps clipping the waveform and expecting the speakers to do gymnastics they're not designed for!

Another factor is the efficiency of the speakers which varies widely between manufacturers and models. In many ways the RMS figure without the linked efficiency is relatively meaningless.


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James PerrettModerator



Joined: 10/09/01
Posts: 10705
Loc: The wilds of Hampshire
Re: PA speaker advice needed new [Re: PGibson]
      #1033256 - 13/02/13 10:30 AM
There's one vital thing missing from the information that you've already given us - the make and model numbers of your existing PA components. Adding an extra cab may cause more problems than it solves.

James.

--------------------
JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net


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PGibson



Joined: 12/02/13
Posts: 9
Re: PA speaker advice needed new [Re: James Perrett]
      #1033324 - 13/02/13 05:46 PM
James, I have emailed my bandmate to ask about the make and model of his pa, but, in my ignorance, I am struggling to see how that relates to what I am thinking of doing. Let me clarify:

The current set-up is as follows: all the microphones go into the Allen & Heath PA12CP powered mixer; from there an unpowered signal is sent to my bandmate's pa power amp which runs one sub and two speakers.

What I was proposing was to 'beef up' the above set-up by using the PA12CP's power amps to drive two more speakers. In effect we would have 1 mixer feeding two 2 pa systems. Is that unwise?

Paul


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Mike Stranks
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Joined: 03/01/03
Posts: 3709
Loc: Oxford, UK
Re: PA speaker advice needed new [Re: PGibson]
      #1033338 - 13/02/13 07:10 PM
I think you'll be disappointed if you're hoping to beef-up your sound-system in the way you describe. Not only will the combined systems not be as loud as you're expecting - I'll spare you the physics - but also adding extra speakers into the equation can cause more problems than it solves. This is especially true when the two sets of speakers are different makes and models. Even with identical speakers phase cancellation between speakers can be a significant issue.

Bearing in mind that you seem to be suggesting that this is a one-off event (at least for the present) I'd be more inclined to hire-in a more powerful system - perhaps a couple of decent powered speakers with/without a sub depending on how good/powerful the existing sub is.


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James PerrettModerator



Joined: 10/09/01
Posts: 10705
Loc: The wilds of Hampshire
Re: PA speaker advice needed new [Re: Mike Stranks]
      #1033420 - 14/02/13 10:47 AM
At worst the sound will be much quieter thanks to the drivers in the 2 different types of speakers being in a different polarity while at best you will end up with peaks and nulls in sound level across the room because the speakers aren't designed as an array.

The only hope you have is that his system is designed to be expandable and, in which case, you would need to buy an identical set of speakers and amps to his.

James.

--------------------
JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net


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PGibson



Joined: 12/02/13
Posts: 9
Re: PA speaker advice needed new [Re: PGibson]
      #1033425 - 14/02/13 11:17 AM
Thank you Mike and James. I much appreciate your advice - I am learning!

I have yet to hear back from my bandmate as to what his pa system is. I suspect the weakness in his pa is in the top speakers. From what I recall I think they are 10" speakers and possibly only rated at 100w to 150w. I guess one option to consider is using his pa to only run the sub, not the tops, and to use the Allen & Heath to run two more powerful top speakers.

Mike, you mentioned the importance of speaker sensitivity. A speaker like the Wharfedale EVP-R12 is rated at 250w RMS with a sensitivity of 98dB.

May I ask one further question that arises from what you have said concerning phase cancellation: as the Allen & Heath powered mixer can deliver a full 500w each side at either 4 ohms or 8 ohms (switchable) I had assumed that an attractive option for the future was to have four identical 8 ohm speakers and run two each side at 4 ohms - are you saying that there might well be phase problems with such a 4 speaker set-up?

Many thanks again for all your help.
Paul


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James PerrettModerator



Joined: 10/09/01
Posts: 10705
Loc: The wilds of Hampshire
Re: PA speaker advice needed new [Re: PGibson]
      #1033428 - 14/02/13 11:35 AM
Quote PGibson:

I had assumed that an attractive option for the future was to have four identical 8 ohm speakers and run two each side at 4 ohms - are you saying that there might well be phase problems with such a 4 speaker set-up?





It depends on the design of the speaker - but you'll have more chance of success if they're identical.

I'm also not sure that your mixer will be powerful enough to handle more than one pair of speakers unless they have a fairly low power handling spec. Most modern speakers are 250-300W continuous which are a good match to a 500W continuous output amp. So, to match your amp, you would be looking at speakers handling around 150W continuous.

James.

--------------------
JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net


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