help, amp speakers crisis

[tomchennells]

ive just bought a numark dimesion 3 amplifier for use on large discos and shows etc :o

for thoose of you who arnt familiar with it heres the spec...

 

Both Dimension 3 and 4 amplifiers feature:

 

Front Panel volume control with output meter display and clip indicators, 5 Way Binding Banana plug and 3 Speakon® outputs, internal crossover for subwoofer with 20-200Hz frequency adjust, 30Hz and 50 Hz low frequency roll off filters, internal Compression limiter with electronic protect for short circuits, 2x dual speed fans coupled with heat sink cooling.

 

Dimension 3

2 ohms stereo 650w

4 ohms stereo 475w

8 ohms stereo 300w

8 ohms mono bridged 930w

4 ohms mono bridged 1300w

 

anyway to cut a long story short I also own two pairs of 15" cabs <_<

 

the first being soundlab 3 way cabinets

and the second are "diy" eminence drivers with horns (so just 2 way)

 

all four speakers are rated at 300w

 

:D

 

- what is the best way to connect them - daisychain ?

- how loud will they all be run at ?

- is there any scope for damaging any of the above equipment ?

 

thanks guys

 

tom

 

ps - yes im a lighting guy who dosnt know too much about sound, altho I am a 2nd year electrician and I still dont understand! - I think all the speakers are 4ohm - thanks again

[James]

I dont like running mismatched speakers on the same amplifier channel.

 

So if you want to run all 4 speakers at once and don't want to buy a new amplifier then I would run the amplifier in 2 channel mode, and your rig in mono. Run the pair of soundlabs in parallel off one channel and the diy boxes in parallel off the other.

 

Be careful about coverage, most of the soundlab boxes I've seen have high horizontal dispertion characteristics. which means they wont array next to each other well without having phazing issues, I wouldn't be suprised if the hf horns in the diy boxes are similar, so be careful with positioning, perhaps you can use one pair as balcony delays or something?

 

As far as volume, you haven't given an indication what 300W represents, is this peak power handling? or RMS or what?

 

Assuming this is RMS you should be fine, just set a reasonable level coming out of your desk, wherever you normaly mix to, I normaly aim for about -6dBu (-12dBu for digital), I then nock it down by another 6db for safety at this point and bring up the gains on the amplifiers to what I think would be the maximum level I would want through the rig for the event.

 

This gives me 24dB headroom on the mixer which should be more than enough, and by setting the amps for the room I'm not mixing somewhere 80dB down, right in the middle of the noise floor of the mixer.

 

Hope this helps.

 

James,

[Matt]

he's using it as a dj rig mate... all he really wants to know if its safe or not to run 2 speakers off of one channel on the amp without risking underpowering the speakers and damaging them

 

and if you ran the diy's off a different channel wouldnt you likely to have an imbalance in the channel volume left to right anyway...??? would have thought it best to equal the speakers out on each channel ???

[tomchennells]

confused ! yes 300w rms not peak

 

it sais 300w on the name plate

[James]

Thanks Matt,

 

there I go rabbiting on about nothing at all and I didn't even answer the question properly.

 

1 what is the best way to connect them - daisychain ?

2 how loud will they all be run at ?

3 is there any scope for damaging any of the above equipment ?

 

1 Parallel, same make of speaker together.

2 depends on sensitivty of speakers and how hard you push them

3 always there is scope if you dont know exactly what you are doing, however there is not that much scope, listen for any audible distortion, (amplifier, speaker or mixer) and be prepared to act, check for overheating of speakers and amplifiers and be prepared to act. Watch out for feedback etc. Watch out for drinks and children.

 

Good Luck.

 

James

[Matt]

didnt asnwer it at all corsding to tom on msn anyway heh heh sry for dropping you innit, thanks for thanking me, I feel wanted now

 

and one would have thought it be better to run one soundlab and one eminence on each channel... so you have balanced sound output, but also depends on placement of speakers...

 

plus its only a disco ** laughs out loud **

 

 

 

 

ps: hope I get nominated for the speel clunker award again this year, lmao I think I have made mroe spelling mistakes, though I have been oging back and editing them afetrwarsds tho, yes I admit it I CANT SPEEL! (notice slight on purpoose mistake)

........................................^^^^mistake not meant here

[tomchennells]

thats helps cheers guys

so how come ill be better off running the two pairs on seperate channels not 1 of each on each side ?

wont that mean the amp will be unbalanced ?

 

the speakers are just gonna be stacked ontop of each other either side of by disco soundlabs on teh bottom diy cabs above - its only a disco so a few crossing waves dont bother me too much

 

thanks - tom

[bruce]

The amp being unbalanced shouldn't really be a problem.

 

The problem is that your 2 different types of speakers - although both nominally 300w and 4 ohms - will have different electrical and sonic characteristics. If you drive them in parallel - ie from the same side of the amp - there's no way to tell what the "balance" will be like, without trying it.

 

And then there's no way to adjust it.

 

If you drive the Soundlab units from one side of the amp and the home-brew ones from the other, you can at least adjust the relative volumes. You may even be able to add different EQ to each.

 

But you lose stereo.

 

Bruce.

[tomchennells]

right so what you guys are telling me in effect is, if I plug them in with one of each on each channel keep it low and listen and the cabs both sound the same volume I can keep stereo in effect ? but this is somewhat unlikely ?

 

but if either is louder its better to split them off and run one pair as left and one pair as right ?

 

im really concerned about this whole underpowring thing ive been told about too, cant afford to wreck the speakers, im a student and a little bit strapped for cash to buy a few more pairs!!

 

my 1300w amp isnt gonna give me 1300w of volume isit ! (infact not even close from the way u guys describe it)

 

tom

[James]

Forget stereo.

 

You have absolutly no way of doing stereo with the equipment you have available anyway

 

Trust me.

 

HiFi people talk about the "sweet spot" With stereo, if you are running a disco you could have 10% of your audience in the sweet spot with better than mono sound and 90% with worse than mono sound.

 

With different impedances I wouldn't care to estimate how the relative loading would work out across the two speakers, Ugh if one has Pizzos with a high inductive content ant the other more resistive you end up building a seriously bad crossover between you speakers. (Did I say ugh?)

 

James

[IanG]

Forget stereo.

 

You have absolutly no way of doing stereo with the equipment you have available anyway

 

Trust me.

<{POST_SNAPBACK}>

 

Indeed - James is spot on here. It really isn't worth it.

 

Out of interest what is between the DJ mixer and the amp? Any processing? If not you'll need a way of monoing the output of your DJ mixer.

[paulears]

Forget Stereo?

 

we're talking disco - so we are also talking popular music.

 

Wide spaced loudspeakers = no or little real imaging, especially centre - but that isn't what 60's to current pop music is about at all. hi-hats flipping left right playing 8's or 16's effects ping ponging - hard left and right panning - all the tricks really, get zapped when mono'd. A two channel (not stereo) rig works better every time. Most clubs have speakers placed all over the place. No attempt at real stereo, but the effect is hugely greater than summing everything to mono.

 

 

If the amp can handle the resultant low impedance of paralleling the cabs, fine BUT if they use different drivers, internal crossovers, baffle designs then volume wise, one type may be much louder than the other. Boosting LF may make one sound better, but may over excursion the other, even though it doesn't appear that loud. Best tool is a good ear and back off as soon as you hear signs of strain. From time to time I've had to run combinations of different brands and to be honest, it never sounds that good to me.

[bruce]

HiFi people talk about the "sweet spot"

 

<{POST_SNAPBACK}>

 

They also talk about directional cable and gold-plated mains plugs. But that's another story....

 

Bruce.

[Tom Baldwin]

I normaly aim for about -6dBu (-12dBu for digital),

<{POST_SNAPBACK}>

 

Forgive my ignorance, but I really "don't do sound"...

 

Why the extra headroom allowance for digital - something to do with digital clipping being "harder", and thus potentially more damaging than the "softer" clipping an analogue system would produce when gently overrun?

 

Tom

[tomchennells]

kinda confusing guys you all seem to have diffrent ideas

 

if I try the stereo way nice and quiet when the amp arrives, see if the cabs sound unbalanced I cant go wrong can I ?

 

if they do sound unbalanced I run them in two pairs as left and right and if they dont then I can stick with that technique

 

out of curiosity, from the amp spec on my first post could any of you tell me if the amp would blow one pair on their own into oblivion ?

 

if I can get away with using one pair I will, obviously the whole point of me having the new amp is to get more volume, regardless of if I use one pair or two

 

thanks

 

- tom