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Amp & Speaker Advice - Ohms!

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I've been doing wedding disco's for friends/family for a year or so and I'm using a combination of some second hand equipment from a mate, and a few bits I've bought on their advice. From reading a few discussions online I'm now a bit concerned that my speakers and amp may not be the correct match for impedence and/or watts.


I've had a few occasions now where the sound has suddenly cut out. So I turn everything off, wait for about a minute, turn it all back on and the sound comes back. I thought it was because the Amp was up too high so I've since been trying to limit to just turning it up about half way (but it's not really loud enough like this). But the last gig I did the sound did still cut out at one point!


Friends & family are quite forgiving but I want to start doing paid gigs so I really need to get this sorted out.


This is my set up:

I'm using Virtual DJ on a Laptop with Windows 7

Mackie ProFX8 mixing desk

QTX Sound PRO1000 Amplifier

2x Peavey Pro-15 (4 Ohms Impedance)

2x Wharfedale SVP-X12 (8 Ohms Ipmedance)


I use XLR to the 1/4" Line in from Mixer to Amp

Then Speakon cable from the Amps Left Speaker-out going to one of the Peaveys Inputs, and then Speakon cable from the Peavey Output to one of the Wharfedale Inputs...

...and mirror this from the Amps Right Speaker out to the other Peavey, and then to the other Wharfedale.

(I think this is called Daisy-chaining?)


I've been trying to work out the Impedance to see if it's right for this amp but I'm not entirely sure how it works? Is 4 Ohms + 8 Ohms in a daisy chain 2.66 Ohms Impedance?


The amp spec is Power Max 4 Ohms: 2 x 500w

Power Rms 4 Ohms: 250w



So firstly please can someone tell me if this set up is ok, or am I on the verge of frying my amp or speakers?

Secondly, can anyone suggest what is causing the sound cut outs - and is there a solution? Am I being cautious with the Amp levels for no reason?


I'd be really grateful for any advice.







Sorry all, I should have included the following info from the back of my speakers:


Peavey Pro-15's

Impedance 4 Ohms

Power 600 Watts Program


Wharfedale SVP-X12

Continuous: 150 Watts

Program: 300 Watts

Peak: 600 Watts

Impedance: 8 Ohms


Thanks again


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yes, sounds like you're overloading your amp. You risk damaging it with such a low impedance. The impedance of the speakers must be equal to or higher than the amp. Since your amp is only rated to 4 ohm, you are over the limit at 2.66R. The amp is also way too low powered for the speakers. It's a shame to have nice Peavey speakers, a nice Mackie desk..and then a bargain basement small amp like the QTX.


The problem is that most amps won't go to 2 ohms or so, at least not at the budget end. So the solution is either a set of matched speakers that will work together to give you a 4R load, or else get an extra amp and drive the bass & top cabs seperately.

Edited by superstardeejay


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or else get an extra amp and drive the bass & top cabs seperately.


That's how I run my PA, (along with an active crossover) and the difference in power and quality I found has been amazing. I would 100% recommend this.



Dance Sounds Disco


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Ok great, thanks for the advice.


I've been looking into getting a couple of powered speakers to replace my 12's - to use for smaller gigs so I don't need to take an Amp.


With this in mind could I use the Amp I've got to power my Peavey 15's and also connect a pair of powered 12's at the same time for bigger gigs?


My Mackie mixer has the XLR outputs on the back and also has Main 1/4 Outputs. Is there a better way round of connecting these if the above scenario is ok to do? (ie. which output to use for the powered speakers and which to use for the Amp)


Thanks again for the help!

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It doesn't matter...whatever's more convenient to you. The mackie will have more than enough signal to drive any number of amps/powered speakers, either daisy chained, or via special splitter leads, or by the way you said, ie 2 leads out on the XLRs and 2 out on the 1/4in jacks.


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