My Setup

[xtc250 0]

right im new too all this business and that but just want to chack i have all my equipment setup properly so here we go...

 

i have my numark CDN22 CD Decks connected to my Numark 200FX Mixer then out of my mixer my balance outputs (left/right) going to channel 1/2 of my amp

 

so this is were i need help

 

My speakers are 200RMS 400Peak @ 8ohms (pro sound 12" 400)

 

My Amp is 250RMS Each Channel 1000Watt Peak (prosound 1000) chaep but all i can afford atm

 

i have a speaker on each channel and they take the amp to full with no distortion :| am i right in saying that the way i have this setup that my speakers are getting 8 ohms each and 250 rms even tho they are 200rms

 

and will this damage my speaker or amp ? nay advice or help im very greatfull thanks

[Gary 0]

Hi and welcome to the forum.

 

There's just one extra piece of info that we'll need, in order to give you a full reply.

 

Along with the amps wattages, there should be some details (on the back of the amp perhaps) of what impedence (ohms) the amp is at those wattage ratings eg: A sticker on the back of the amp might say "1000watts @ 4ohms" or "250 watts @ 8 ohms" etc.

 

If you can provide that info, it'll save a fair amount of replies coming back to you with "if.....then...."

 

In the meantime, I'd be careful with the amps attenuation ("volume") setting - keep it about halfway for the mo...

[Tonsk 0]

Just had a look on the Maplins website who sell the ProSound range and it looks like it is 250w at 8 ohms - This means that you are putting more into your speakers than they can comfortably handle...

 

50watts isn't a massive amount extra which is why you haven't experienced any problems - YET.

 

It is not good for the speakers though so turn it down a little....

[xtc250 0]

rite o thanks 4 the replys i was planning on upgrading to the 15" version of mine they are 250rms @ 8ohms so would suit my amp better but heres the spec of my amp

 

1000W Power Amplifier

 

Manufacturer: ProSound

 

Specifications:

4Ω 2 x 400Wrms

8Ω 2 x 250Wrms

Max power 1000Wmax @ 8Ω

Frequency Range: 10Hz-20kHz

S/N ratio: >95dB

THD: >0.5%

Dimensions 485(w) x 88(h) x 400(d)mm (inc. handles)

19 inches x 2U x 15 inches

Weight: 18kg

Connections

Output: 2 x Speakon

Input: 2 x 1/4 inch jack

 

[jeffwall 0]

agreed

 

your amp can deliver a little more than your speakers can handle, so beware and take it easy....dont run the amp at max......3quarters max i would reccomend

 

apart from that, you have no problem here

 

good luck in your new carreer!!

 

 

[norty303 0]

50watts isn't a massive amount extra which is why you haven't experienced any problems - YET.

 

It is not good for the speakers though so turn it down a little....

 

Nonsense. 50 watts will be barely discernable to the speakers. You could damage the speakers as easily with 250w as 200w IF YOU ABUSE THE AMP.

 

Just make sure that the amp doesn't clip and you'll be fine. You could use a 400-500w amp under those conditions and be fine.

 

And remember that whilst you can control the amps gain, it is still possible to put the full power of the amp through the speakers by driving the input harder (i.e. turning up your mixer)

 

 

People have their own opinions on what is/isn't safe to drive into a speaker however this is their opinion and the way they prefer to work. I just wish they wouldn't present this as fact or scaremengering. The reality is that you can drive a speaker harder than it's rms rating because music is a dynamic signal and the rms it receives is far less than the peaks the amp supplies. If your amp can supply 250w max then it will only ever be able to supply this at its peak (providing no clipping). The average will be somewhat lower.

 

Speakers are given their rms rating by running constant tones for periods of time until they break (normally a melted or broken voice coil). The level at which they don't break when run for the designated period is their rms rating.

 

There are a number of threads on the board about why/why not to run a bigger amp. Please search them and read what people have taken the time to write regarding this subject, including the pros and cons experienced by both.

 

Just had a look on the Maplins website who sell the ProSound range and it looks like it is 250w at 8 ohms - This means that you are putting more into your speakers than they can comfortably handle...

 

50watts isn't a massive amount extra which is why you haven't experienced any problems - YET.

 

It is not good for the speakers though so turn it down a little....

 

There is a certain amount of misinformation in this post, so please read for yourself and make up your own mind. If you want to read up in more detail about speakers and power then I'm happy to go further or point you in the direction of resources that will help.

 

 

Edited August 13, 2007 by norty303

[rictic 0]

i have always been taught make sure your amp is bigger than your cabs.

under running a cab can be fatal.

under running an amp is cool.

for tech details look elsewhere.

but i am sure i am right.

[bedfordft 0]

i have always been taught make sure your amp is bigger than your cabs.

under running a cab can be fatal.

under running an amp is cool.

for tech details look elsewhere.

but i am sure i am right.

 

hi i work for maplin's and am aware that the set up you have is the one on offer this month, this is a package deal put together by the company so if you have any doubts about its cappablities might i sugest that may be you go back to your store and ask them to contact the product support team who would be able to give you the right answers.

 

although i my self have always used the rule that i would never turn the amp up fully but keep some in hand to cut out the distortion rate, when i started in 1974 i had 125w amps but i would never go over 75w as then i had power in hand for heat and distortion.

 

although your amp does have a cooling fan.

 

hope this helps

 

regards

[Andy Westcott 0]

Quote Rictic:

"under running a cab can be fatal."

 

No, that's incorrect. (Pet hate of mine, that one! )

Technically, all cabs are under-run, unless you are burning the voice coils, right? Feeding a cab with only 50% of what it can handle will simply result in a cooler motor and a far (infinitely?) extended speaker life. There are such things as volume controls, and these allow you to 'under-run' a cabinet to an infinite degree, if you understand the point I'm trying to get across.

 

However, you can and probably will get away with running a certain cab with an amp up to 3 times the speaker's rating, but only because the average power contained within the music signal is a lot less - perhaps only a third - of what the amp is capable of putting out continuously, but this is a dodgy practice as certain material may contain large amounts of almost continuous bass signal - Rhianna's 'Pon De Replay' is one such track, and this is when things may start to smoke.

 

Ultimately it all depends on how you intend to use your equipment, but I don't think any tech on here would suggest that doing what I'm currently doing - running 600 watt bass drivers with a 300 watt amp - is dangerous to the drivers.

[norty303 0]

although i my self have always used the rule that i would never turn the amp up fully but keep some in hand to cut out the distortion rate, when i started in 1974 i had 125w amps but i would never go over 75w as then i had power in hand for heat and distortion.

 

How do you know you were putting out 75w?

 

Also, as Andy says in his post, the gain controls only control what gets fed to the amp stages, so you can clip the amp on 1/4 turn of the pots.

 

If an amp can't run at it's stated load, with less than 1%thd, at full chat all night then you really want to be looking at another amp (imo)

 

Ultimately it all depends on how you intend to use your equipment, but I don't think any tech on here would suggest that doing what I'm currently doing - running 600 watt bass drivers with a 300 watt amp - is dangerous to the drivers.

 

Nope, absolutely not - but it's the twist on that thought that gets thrown about by people - i.e. underpowering drivers is damaging - but they don't quantify what they mean by it. It's often regurgitated from a half read forum thread with little understanding of why someone might have said having too small an amp is dangerous under certain conditions. Equally, the 2x amp size isn't often qualified, with explanations of HOW you should be running a system with an amp that size.

Edited August 13, 2007 by norty303

[xtc250 0]

k thanks for your replys im planning on getting the 15" version that are 500watt peak 250RMS witch is the rating of my amp im sure i am ok with this setup ? as it matches my amp.

[cookiecat 0]

And remember that whilst you can control the amps gain, it is still possible to put the full power of the amp through the speakers by driving the input harder (i.e. turning up your mixer)

 

How?

If you only have your amp at 1/2 putting up your mixer is not going to put up the gain of the amp.

Or am I wrong?

Surely if that was the case you could make a 500w amp 750 by turning up your master. :shrug:

 

 

 

 

 

I'll get my coat :djuhi:

Edited August 13, 2007 by cookiecat

[norty303 0]

Notice that i said 'full power of the amp'

 

Having the pots at 1/2 does not guarantee you only getting half the power.

 

 

Try it for yourself, put the pots at half (with no speakers connected if you like) and turn up the mixer as far as it'll go, you'll be able to make the clip lights flash.

Edited August 14, 2007 by norty303

[bedfordft 0]

How do you know you were putting out 75w?

 

i would work on the rule that a full turn of the master pot was equal to 125w per channel +/- may be 10% so just over half way was good!

 

but i don't understand the need for all this power i use the maplins 200w amp and the small pro sound speakers, the importaint bit is i also use stands and make sure that the speakers are above head hight thus the human body absorbs less of what i m pumping out and the sound travels farther we have to watch out for the dreeded sound clipping metering now in many halls althought i am told a condom works well!!!

[norty303 0]

i would work on the rule that a full turn of the master pot was equal to 125w per channel +/- may be 10% so just over half way was good!

 

 

But as the majority of pots used on amps are log pots, how does your theory work there?

[jeffwall 0]

The way i see it.....

 

Your mixer can send the amp a nominal signal at say 0db....this is not clipped and the gains will be at normal level

 

With this signal, the amp is fine and the speakers are fine (providing you keep the amp within the speaker capabilities)

 

If you clip your signal from the mixer.....ie.....have the gains turned up high and send the amp a "clipped/distorted" signal........this is when the damage can occur, because the amp will magnify the clipped line level and send the speakers a clipped speaker level....thus damaging speakers or amp?

 

May be wrong but even if you dont believe this.....keeping it from happening will ensure long life on ya gear i reckon?

[xtc250 0]

The way i see it.....

 

Your mixer can send the amp a nominal signal at say 0db....this is not clipped and the gains will be at normal level

 

With this signal, the amp is fine and the speakers are fine (providing you keep the amp within the speaker capabilities)

 

If you clip your signal from the mixer.....ie.....have the gains turned up high and send the amp a "clipped/distorted" signal........this is when the damage can occur, because the amp will magnify the clipped line level and send the speakers a clipped speaker level....thus damaging speakers or amp?

 

May be wrong but even if you dont believe this.....keeping it from happening will ensure long life on ya gear i reckon?

 

 

i agree with that i keep my mixer at 0db witch is just under red line-ing so i will keep it at that thanks 4 your replys

[superstardeejay 0]

But just because the mixer isn't clipping doesnt mean the amp isnt! Most mixers these days will gleefully give the amps enough level to clip them without actually clipping themselves...well into the red. An amp clips when the power stage runs out of room, leading to damaging transients on the outputs.....a well covered topic in itself.

 

I once had to inspect a newly installed system at a nightclub installed by a local DJ shop. The installers' solution to prevent clipping / damage was to turn the gains on the amps down to 3/4 of the way and stick gaffer tape over the knobs! The DJ's of course just whacked up the mixer gains and kept blowing drivers until the system was pulled out after only 2 years.

 

 

I've read and re-read all these posts and Norty as usual is the one in the right from an engineers point of view. And I agree that the Maplin package is correctly specified. If you can't run the system loud enough without clipping, burning or overheating, then you need to save up for a bigger system or do smaller venues!

 

Regarding the ProSound specifically, you could always add a couple of extra speakers or bass bins as funds allow, (Maplin do the matching ones) giving the amp a 4 ohm load and nearly doubling the wattage developed. Dont forget the vouchers in the Maplin catalogue are valid for larger purchases like this!

Edited August 15, 2007 by superstardeejay

[xtc250 0]

 

Regarding the ProSound specifically, you could always add a couple of extra speakers or bass bins as funds allow, (Maplin do the matching ones) giving the amp a 4 ohm load and nearly doubling the wattage developed. Dont forget the vouchers in the Maplin catalogue are valid for larger purchases like this!

 

thanks for that advice....

 

am i right in saying that if i add two prosound 15" 500w speakers to each channel of my amp (making 4 speakers all togther 2 x 12" 400w and 2x 15" 500w) they would get 4 ohms and if i removed one from each channel (leaving one speaker per channel ) they would get 8 ohms again as there is only one speaker on each channel

 

 

if this is the case i may have to get the 15" version.

 

could i then link the up all 4 speakers to my amp as each channel would have 450RMS but would this damage my amp as its only rated at 250rms per channel. or would i have to just use the 15" version alone and not with the 12" version joined togther

 

 

i know this may be a little confusing but im not very good at explaining things too well sorry

 

thanks

 

 

[Grazey 0]

I'm pretty sure this is how it works...

 

Wiring your amp like this will put 250W RMS into each side/speaker and will run the amp and speakers at 8Ohms

 

Speaker--------AMP--------Speaker

 

 

While wiring them like this will put 400W RMS per side, split evenly between the speakers, so 200W per speaker, the amp running at 4Ohms, but the speakers at 8Ohm

 

Speaker -------- Speaker --------AMP--------Speaker--------Speaker

 

 

Hope this makes a bit of sense :)

[xtc250 0]

yeh that makes alot more sense

 

ok now thats sorted i have one more question for you teckies.

 

i decided to buy the 15" version of mine so im planning on putting all my 4 speakers on my amp like:

 

http://i10.tinypic.com/4tg8pqb.jpg

 

as you see if i set it up like this im putting 450rms in two each channel were as my amp will only put out 250rms per channel. Would this now overload my amp or would it comfortably handle this setup.

 

if it results to it i will just stick with the 15" speakers on each channel which i have no problem with.

 

thanks one again

 

Dave

Edited August 16, 2007 by xtc250

[Grazey 0]

Putting 2 speakers on one channel of the amp will make the amp run at 4 ohms, so in the example you list the amp will put out 400W rms a side, equally split between both speakers, so each speaker will get 200W each.

 

eg: a picture of 1 side of the amp, bare in mind the same will happen if you wire it up the same the other side. So your amp will put out 800W RMS in total.

 

AMP--------Speaker (getting 200W from Amp)--------Speaker (getting 200W from Amp) = 200W+200W = 400W per side

 

 

whereas if you run the amp with a single speaker per channel the amp will deliver the 8ohm load to the speaker eg:

 

AMP ------ Speaker (getting 250W from Amp)

 

 

The size of the speakers doesnt change the amount of power the amp will distribute.

 

 

You can illustrate this yourself if you connect the output of one speaker to the input of the other speaker connecting the first speaker to the amp. I was confused at first when i did this, but they run at similar volumes off only one channel of the amp.

 

Hopefully thats helped!

[Grazey 0]

so the answer to your question would be no, it wouldnt overload the amp (providing you dont run too high a signal through it) But all 4 speakers per channel would share the 4 ohm load between them rather than the 8 ohm output.

 

IE:

total 4 Ohm load for the amp is 800W / 4 Speakers = 200W each

 

Rather than

 

8ohm load for the amp is 500W / 4 Speakers = 125W each

 

 

[old soul 0]

Personally I'd want to use a bigger amp, but I come from that school of thought which says give the amp the headroom, others may, and will disagree. What you're describing there though, could lead to problems unless you are very disciplined when using it, it's very easy to get carried away with a room full of bodies, and pay for it later. (so speaks the voice of experience)

[norty303 0]

so the answer to your question would be no, it wouldnt overload the amp (providing you dont run too high a signal through it) But all 4 speakers per channel would share the 4 ohm load between them rather than the 8 ohm output.

 

IE:

total 4 Ohm load for the amp is 800W / 4 Speakers = 200W each

 

Rather than

 

8ohm load for the amp is 500W / 4 Speakers = 125W each

 

Ok, to be clear here, if you attach 4 8ohm speakers to 1 channel of the amp you present a 2ohm load (2 x 8ohm speakers in parallel = 4ohms, 2 x 4ohm loads in parallel = 2ohms)

 

This will kill a lot of amps, even amps that are rated for 2ohm loads will run hot and the damping factor decreases significantly, and if you're using thin speaker cable (