Help A Rookie

[peteclarkson 0]

Hi all,

 

I'm new to the forum, and also to the PA gig.

 

I'm having trouble getting the most out of my speakers. I have an 800watt amplifier, which I at first took to mean 400watts per channel, which would power my 400watt (max) speakers perfectly. But my amp has 4ohm min impedence, and my speakers are 8ohm each.

 

How is best to connect them? I am currently running a speaker off each channel, but would I get the same output by connecting them in parallel, leaving the other channel free for 2 more speakers? If i'm right I should be able to have 4 speakers instead of 2, meaning more headroom and better surface area, so I don't need to crank the volume so much, so I can boost the bass a bit.

 

Right?

[MintyDave 0]

Hi peter

firstly welcome to the forum, you have come to the right place for some great advice and pleanty of support.

 

amp and speaker wise i see you problem. An amp rated at 800w usually means at its minmum impedance output so when you connect a pair of 8ohm speakers you may only be getting 400w in total (200+200). bearing in mind that the specs are not precise and you cant guarantee 100% efficiency this figure may not be realsitic.

 

connecting both speakers in parallel into 1 channel will give you an overall impedance of 4 ohms and greater vol but the problem is that you may loose stereo imaging. the ideal sloution would be to have a second pair of 8ohm cabs and use all four.

 

bass bins are usually 4 ohms and some have a crossover designed in a way that irrespective of what is linked up top the amp sees an impedance of 4 ohms. daft as it may sound 4ohm + 8 ohm = something like 3.2 ohm

 

hope this helps and do post back for more info as there are some very skilled members on here who not only djs but work in electrical engineering

 

Reagrds

[peteclarkson 0]

Hi,

 

Thanks Dave for your reply and warm welcome! I'm glad I found this forum and do have lots of questions to ask. I will appreciate your (collective) advice and insight, and in months to come I'm sure I'll be able to bring another rookie on in turn!

 

Okay, back to business! All sound advice dave, but a few questions. What do you mean by stereo imaging? And also, if I was to get bass bins would I wire the to bins in one channel and the tops in another or one in each channel?

[MintyDave 0]

Your cd players etc all have stereo outputs which in turn run through a mixer etc then in to left and right channels on your amps. if you just connected one side you would in effect loose half of your music. You could use the bridge mode on your amp if you have one which sends the full signal out of the dedicated bridge output.

 

For bass bin connections you could use bins on one side and tops on the other as this would give you volume control between the two. however getting back to the stereo issue, you may find that the majority of vocals and drums etc run through your bins and guitars and synths go to the tops. Obviously every track is mixed differently at source and the effect would vary. Some of the original beatles recordings were panned hard with no guitar appearing on the left or right channel at all or john lennon on one side and george harrison on the other.

 

Ideally you would connect your bins to either side then link your tops into them. If you have some spare cash then a second amp and an active crossover would be the perfect option. The mixer would supply a signal to the external crossover which would filter the frequencies and sent low to the bass bins via an amp and the mid tops via an amp. More complex but better sound quality. Sometimes its not about getting more volume but better clarity coverage and dispertion.

 

Reagrds

 

Dave

[peteclarkson 0]

I'm looking at a Behringer Europower EP 4000 amp. But to afford it I'm going to need to chop in my IMG 800w. If I get an active crossover, can I break the frequency and send them to different channels on the same amp?

 

If I can, I will still lose stereo imaging to a degree, so is there any way I can convert the signal to mono?

 

That way, I get the full image (albeit not stereo), and retain the ability to adjust the bins and tops volume independantly.

 

PC

[MintyDave 0]

I wouldnt recommend doing that. You say your speakers are rated at 400 w max - whats the rms value what size drivers are they. There are various threads about speaker and amp matching for more advice.

 

I would avoid running mono and do things right, by all means get a bigger amp that suits your speakers and adding a second set of 8 ohm speakers will give you greater coverage. You dont need to control bins independantly to the tops as the passive crossovers that are built in sort things out, especially if you use bins and tops from the same manufacturer.

 

I recently sold a set of 4ohm 350w peavey hisys speakers on ebay for £120 and they sounded awesome

 

Nobody has the cash to get the best straight away and we all have to build up slowly. I started using a ancient pioneer karaoke amp and am saving up to get a set of rcf actives

 

Going to 4000w is a bit ott and if you are not carefull you could easily blow your speakers to bits.

 

 

 

 

[Dream Catchers 0]

Again you need to read the specifications carefully before thinking you have something that will power a stadium on its own.

 

 

Output Power - EP4000

 

RMS @1% THD (sine wave), both channels driven

8 Ohm per Channel - 550 W

4 Ohm per Channel - 950 W

2 Ohm per Channel - 1250 W

 

RMS @1% THD (sine wave), bridged mode

8 Ohm - 1750 W

4 Ohm - 2400 W

 

Peak Power, both channels driven

8 Ohm per Channel - 750 W

4 Ohm per Channel - 1400 W

2 Ohm per Channel - 2000 W

 

Peak Power, bridged mode

8 Ohm per Channel - 2800 W

4 Ohm per Channel - 4000 W

 

In real terms it is a 550w + 550w RMS amp, as in most cases you will be running it with a 8Ω speaker on each side.

 

Jim