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Old 2nd October 2012, 10:38 PM   #11
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Location: Sheffield
Replace the driver with something from Eminence or similar - messing about with more relatively-low-quality stuff will just result in more blown drivers.

Eminence 1000 W Kilomax 15 Speaker (8 Ohm) | eBay

Eminence DELTA-15LFA 15" PA/Disco Chassis Speaker | eBay

You'll struggle to kill either of those - Eminence drivers are generally known to be difficult to kill (and I've tried), and a driver alone at ~70 is going to be of far better quality than the bass driver in a pre-made cab of the same cost.

Just avoid the Alpha 15.
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Old 2nd October 2012, 11:49 PM   #12
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That is a damn good idea.

not only might it solve our problem (for now)- but it will also appease the bands vocalist- whos main contribution to our rig has been the PA speakers.

Thanks for the heads up- with a name like kilomax I doubt anything will kill these drivers- but won't they fry my amp?
At the mo it runs at 12 o'clock and thats plenty loud- but its rated at 250wrms/channel - and its running speakers that are rated at 250 wrms. won't the Cabs pre-existing passive crossover get confused by the new speakers.

Or would it just be a matter of restricting the amp-making sure we don't turn it too high.
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Old 3rd October 2012, 05:11 PM   #13
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It looks like you still haven't understood speaker vs amplifier power ratings.

I'm going to try to stick to the basic side of ohm's law: V=IR, where V is voltage across the resistor, I is the current through, and R is the resistance.

P=IV is the other one you'll need - Power = amps x volts.

I'm not going to bother with RMS voltages etc, because they mostly confuse things, and I want to go to the pub later so won't have enough time to explain them sufficiently well.


Lets say your amplifier can do up to 50v output, with enough current to drive 4ohm speakers to full power.
This would be 12.5A.
This would mean the amplifier will give out up to 625w into a 4ohm load.

The amplifier does not know or care how much power the speaker will actually stand. All it sees is the resistance of the speaker (ie, if the amplifier puts out a certain voltage, how much current passes).

The Eminence driver is 8ohm.
Given the above amplifier, you'll be passing 50v => 6.25A into the speaker.
That would be 312.5w into the Eminence, which it will stand all day, every day, and carry on working.
If you wire another identical speaker in parallel, they each see 50v, so each will draw 6.25A.
The amplifier gives out 625w, and (because the current is equal for each speaker) each speaker sees 312.5w.

In terms of how far up you turn it, amplifiers are (generally - there are, of course, exceptions) voltage devices - if you turn it to 12 o'clock, the amplifier might give a gain of 20x. So if you put 1v in, 20v comes out.
Put a bigger signal in, bigger signals come out. Put a small signal in, and increase the gain, bigger signal comes out.

My point is that the position of the volume control is largely irrelevant.


The Eminence Kilomax will stand over a 1000w continuously. The metal thing on the front is there to get rid of heat more effectively.
There is no chance of you killing it, especially with other lesser drivers in the system - I can guarantee that (so long as the Eminence driver isn't defective) the others will die first.

The pre-existing crossover shouldn't pose a problem - both of the drivers above have a reasonably benign midrange response (no massive peaks to worry about) so should pretty much drop in.

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Old 3rd October 2012, 05:35 PM   #14
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Thanks Chris- But physics is a long forgotten subject to me.

I did phone the place i bought the amp today and managed to speak to someone who seemed in the know (which is unusual for ***lins!)

he told me the output levels don't matter to the amp, and as long as the impedance is right I should be okay with that big driver - plus your new advice i'm now confident i'm doing the right thing by fitting this driver. I have seperate volume controls for each channel so I can fit the kilomax to repair the one side- keep that sides level a bit lower (?)-and pan the bass player so he only comes out of that one side- Sorted

Thanks to all who've contributed to this thread!!
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Old 4th October 2012, 03:31 PM   #15
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Hi Im also fairly new to this too so with your help would be kindly appriciated.

I have currently 2 Skytec speakers and their spec is as follows:

Model Passive Peak power 600W Output power 300W Impedance 8 Ohms Frequency response 40Hz - 18kHz SPL @ 1W/1m 98dB SPL max 126dB Woofer 15" Horn 1 3/8" Titanium Compression Driver Top Hat Yes Supplied Single Dimensions 460 x 510 x 755mm Weight 20kg
I have just orderd an Amp to power these speakers and the amp spec is as follows:

Behringer iNUKE NU3000
Delivers 2 x 1600 Watts into 2 Ohms; 2 x 900 Watts into 4 Ohms; 3000 Watts into 4 Ohms (bridge mode) and weighs less than 7 lbs.

Now that i have already orderd this Amp without knowing about matching the Amp with the Speakers, will this work? is the amp way to powerful? will the speakers get damaged or the amp?

I also have 2 RCF speakers and their spec is as follows:

RCF ART 300 speaker system
Impedance: 8 ohms
Power: 300W

Currently i have these RCF speakers running of an Alan & Heath PA12 mixer with a built in amp (not sure what size). So we decided we wanted to expand and buy 2 extra speakers and will need to buy an external amp to power these skytec speakers up.

So can you guys give me the best way in powering these speakers up? can all four speakers be used on only the Behringer iNUKE 3000 and still match the omhs? This is where i need the professional help.

Thanks Guys
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Old 4th October 2012, 08:06 PM   #16
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Right, if your set-up is mono, put the two RCFs in parallel on one of the amplifier channels, and the two others in parallel on the other amplifier channel.

That way, you can use the volume control on each channel to compensate if one of the speaker sets is louder than the other.

If you're running stereo (preferable in, say, a band situation with more than one guitarist), put one of each speaker on each amplifier channel (wire the speakers in parallel), stack each pair of speakers vertically (eg, one RCF one Skytec per side, RCF on top of the Skytec).

The amplifier will be fine. Just make sure you don't clip it.

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Old 6th October 2012, 01:30 PM   #17
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Hi Chris- Its me again!....

I ordered the kilomax and will fit it next week. In the meantime I forgot to cancel my bid on two new 3way 8ohm speakers-and won them on ebay!. I WAS going to add these to the set-up to spread the load, until 'sreten' suggested that using pairs of PA speakers on each side of a stereo set up caused problems with interference. I'm assuming this is because they aren't identical.
My question is- couldn't this be overcome by putting the two new identical 3 way speakers on the right side (auna 1522s-8ohm 400wrms each) and the two old speakers on the left (Both phonic 715s 8ohm originally both 250 watt each but one will now have the kilomax driver in it making it more like 1050 watts rms) Given i have seperate volume controls for each channel then I can level them if necc. I admit this is a bit of frankenstein set-up but in theory it should work?? as long as we don't turn it up too loud?
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Old 6th October 2012, 01:35 PM   #18
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I forgot to mention that the amp were using (prosound 1600) outputs either 2 x250watts rms at 8 ohms or 2 x 500watts rms at 4 ohms per channel...
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Old 6th October 2012, 03:40 PM   #19
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Sreten was quite right about interference.

The problem is that, when you have two sources radiating the same sound, but are different distances to your ear, cancellation will occur when wavelengths are small (ie, in the treble).

Larger wavelengths mean the difference in distance from source to you is small compared to the wavelength, so cancellation isn't a problem.

Connect them up as you said above, then walk around and have a listen.
Ideally, you'd have the tweeters as close together as possible.

Turn it up as loud as you like, so long as the amplifier doesn't clip (pretty sure there's a clipping indicator). The speakers are rated sufficiently to run the amplifier at full power.

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Old 7th October 2012, 12:05 AM   #20
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I bow to your knowledge-

what your saying is that the high frequencies will arrive 'in ear' at very slightly different times because the sound sorces creating them are slightly different...creating a 'guitar phaser effect'?

Will it sound dodgy do you think i'm wasting my time- the rig is only for practising/writing -its not for recording

the amplifier has overload/shutdown circuitry- so thats not a worry.
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