Advice on Purchasing Amp & Speakers

[Paul Forsyth 0]

Cheers Mikee

 

Will go have a look and play

 

the speakers don't sound damaged (thankfully)

 

Vinnie

[Paul Forsyth 0]

RTFM

 

Read the flipping manual

 

THe mixer (Citronic CDM10:4) has an output of 0 dBu (775mV rms)

The amp has input of 0dBu (1.0 V rms

The mixer doesn't have switchable output settings.

 

 

PS this is all beyond me http://www.dj-forum.co.uk/html/emoticons/fear.gif

 

Vinnie

[ChrisPointon 0]

There is a small amount of mismatch between the Amp and speakers, although it is opposite to what would overload the Amp.

 

For instance, your Citronic will produce signal beyond its rated 775mv but in doing so will introduce more distortion into the signal chain. It is always a good idea to make sure that all of your audio components are matched. For example, A 775mv output from mixer should ideally be plugged into an amp with a 775mv input sensitivity.

 

775mv ratings are often the standard, although 1.2v is commonly used on US manufactured equipment.

 

The above is purely for advice, since I don't think its causing your described problem, although it may account for a slight loss of quality when approaching the Amplifiers rated power levels.

 

How about your bass control on the mixer?. A high bass setting can cause the amp to clip at lower power levels. Try reducing the bass on the mixer eq to see if this makes any difference.

 

The more obvious advice is to turn your amp controls upto 80 or 90% of their travel and then lower the volume from your mixer. My guess is that your mixer output is clipping, and driving large amounts of distortion into your amp.

[Paul Forsyth 0]

Cheers guys - have been going through the manual for details.

 

will have a play with the kit tonight as I am not giging.

 

Am I right in my assumption that the rms of the speakers is 250W from the 500W program & 1000W peak figures as I can't find a rms figure anywhere in the manual for the speakers

 

Vinnie

[ChrisPointon 0]

QUOTE

Also what would be the best way to get more volume - mainly all age functions / weddings - would I be better off getting another pair of matching speakers and link them or adding sub woofers ? or would I be better off buying a more powerful pair to run on their own?

 

First of all, replacing your existing speakers with higher wattaged ones will NOT increase the power level of your amplifier at 8 ohms.

 

The amplifier will only deliver its 8 ohm rating to the speaker, regardless of whether the speaker is rated at 200W or 600W. The amplifier dictates the power output not the speaker!!.

 

So for instance if your amp said something like:-

 

400W RMS @ 4 ohms

270W RMS @ 8 Ohms

 

Your amp would only deliver 270W into an 8 Ohm speaker regardless of whether the 8 ohm speaker itself was rated at 300W or 800W.

 

So if your amp will only deliver 270W @ 8 Ohms (as in the example), you won't magically get 800W from the amp simply by connecting a higher RATED 800W speaker.

 

The only way that you'll get more power from your existing amplifier is by connecting another pair of 8 Ohm speakers alongside your existing speakers. So effectively you'll be using 4 speakers - 2 per channel, which will lower the impedance (load) on your amplifier from 8 ohms per channel to 4 Ohms per channel. Thus giving a slight increase in overall power output.

 

Again don't be fooled into thinking that it'll double your volume, because it won't , sadly the human ear doesn't work like that and as i've said before, in real terms 500W does NOT sound exactly twice as loud as 250W. Yes It will sound louder, but not twice as loud http://www.dj-forum.co.uk/html/emoticons/smile.gif .

 

Sadly, if you are clipping your amp on a regular basis, and non of the solutions work, or there is no obvious fault with the Amp / Mixer, then you need to consider an upgrade to a more powerful system.

 

 

[ChrisPointon 0]

There is a maths formula to work out watts figures accurately, but the rule of thumb is that Program is twice the continuous rating of RMS.

 

Ignore any peak or PMPO ratings, as this is the absolute maximum rating that the speaker withstood in the testing lab before it destructed. http://www.dj-forum.co.uk/html/emoticons/whistling.gif

[Paul Forsyth 0]

Cheers Chris

 

Checking through some of the stuff you guys have suggested I think I may have been panicing a bit - fortunately the clipping (red) led light hasn't been lighting up but I have been running at the top of the amber ones.

 

The amp has a limiter to stop the output sending a clip signal, as I mentioned before it also has a low cut filter to remove ultra-low frequency which I have now switched on.

 

Following Mikee's advice and turning the amp volumes right up, I can take the master volume up to 7 with the line volume up to 10 (max) without the amp clipping. (I have disconnected the speakers to avoid damage (both to them and my ears)

 

On the upgrade side the amp runs

300W rms @ 8ohms per channel (stereo)

475W rms @ 4ohms per channel (stereo)

650W rms @ 2ohms per channel (stereo)

 

The speakers as I mentioned run at 500Wpower / 4ohms 1000W peak

(how do these guys get away with not putting rms ratings on their literature)

 

I was kind of thinking of just linking another pair of the samefrom the speaker backs?

 

Vinnie

 

 

[Paul Forsyth 0]

PS would a pair of 500W rms 4ohm speakers be a bad combo with the amp running at 475W @ 4ohm?

 

Cheers

 

Vinnie

[ChrisPointon 0]

 

Occasional peaks into the red, where the clip light illuminates briefly during loud music bursts are not considered a problem. Providing that the light isn't a continuously lit beacon, then don't worry about it!.

 

 

QUOTE

would a pair of 500W rms 4ohm speakers be a bad combo with the amp running at 475W @ 4ohm?

 

Not at all, provided you followed the advice above and kept the levels below long term illumination of the peak light, then it should be a reasonable combination. You still have a small safety margin of headroom.

 

QUOTE

(how do these guys get away with not putting rms ratings on their literature)

 

It's not a legal requirement, but since RMS has always been the industry standard power output measurement for continuous speaker ratings, you perhaps have to ask yourself why are they misleading people with bigger and better figures!. Most manufacturers have taken the plunge and now list RMS figures, however the American Manufacturers have yet to follow suit.

 

[WhiteShark 0]

Oh dear. http://www.dj-forum.co.uk/html/emoticons/sad.gif After reading the posts in this topic, I am now concerned about my setup. The rating of my speakers, below, are actually PEAK ratings and have no program or rms figures on them.

 

2x Skytec 12" 200W speakers (8 Ohms)

2x Skytec (2x12" drivers) 300w speakers (8 Ohms)

 

I run them with 2 speakers per channel.

 

The amp.....

 

SoundLAB G097M Amp

 

...has the following rating....

 

Stereo 650w @ 4 Ohms

400w @ 8 Ohms

Mono Bridged 1000w @ 8 Ohms

 

Is my assumption that my speakers are actually very weak and are being heavily over driven by the amp a correct one? I always ensure that no clipping occurs during use and have kept the amp volume fairly low, (although the mixer has been pushed a bit), but with bigger gigs fast approaching I'm going to need to increase the volume somewhat.

I've just had to turn down a gig because I felt I didn't have sufficient power. http://www.dj-forum.co.uk/html/emoticons/sad.gif

 

I have a second question. I have been looking into buying some Peavey Messenger Pro 15's (2x full range & 2x bass bins). These speakers are rated at 4 Ohms.

If I buy them, would my current amp be sufficient to run them without fear of damage?

 

Thanks in advance for your help.

[ChrisPointon 0]

The actual RMS values of your speakers are as follows:-

 

Skytec 12" 200W - 125W RMS (200W Peak)

Skytec 2x 12" 300W - 175W RMS (300W Peak)

 

Total (both speakers connected) :- 300W RMS @ 4 Ohms

 

Amp Power:- 650W RMS @ 4 Ohms

 

Yep, you have some potential problems here, with the Amp actually being capable of delivering more than twice the RMS power of the speaker ratings. Even if you take into account the Peak figures of the speakers there is still a 150W difference. You will have to excercise quite a bit of care not to overdrive them.

 

Always compare RMS figures of speakers to RMS figures of Amplifiers, ignore the peak, maximum and PMPO figures they are meaningless in this industry and are just used to make things look better than they really are.

 

The Speakers you have are not really suitable for the Amplifier, I would upgrade as soon as finances allow.

[WhiteShark 0]

Thanks Chris. You've comfirmed my worst suspicions.

 

Do you think my amp could cope with 4 peavey pro 15's, with each cab running at 250w continuous at 4 Ohms?

 

Don't want to go and blow more money on some more unsuitable speakers.

 

Cheers.

[ChrisPointon 0]

Even with 2x 250W RMS Cabs you are still treading a fine line, although certainly not anywhere near the risk you are running with the Skytec's. If you feel that you can excercise a little control with regard volume levels and not drive the Amp into clipping then you should be okay with 2x Peaveys per channel, or invest in a compressor - limiter and physically set it so that you can never clip the amp.

 

Ultimately I would be more comfortable with 2x 300W or 2x 350W cabs running from a 650W Amp which results in speakers which are neither underpowered nor overdriven, however you'll probably be okay with the Peaveys - just keep that red clip light OFF http://www.dj-forum.co.uk/html/emoticons/smile.gif (as indeed you should with any Amp / Speaker combination).

 

As far as the Soundlab goes, well they are good Amps and use MOSFET transistors, as well as being fully protected, so you shouldn't run into any issues with that.

[WhiteShark 0]

Chris, you are indeed a true gent and scholar.

 

Yet again I bow down with gratitude for your help.

 

 

Thanks again.

 

http://www.dj-forum.co.uk/html/emoticons/biggrin.gif

[funkymook 0]

just read through all these and noticed a few comments about amps clipping - isn't this sometimes due to the signal from the mixer being too high and overloading the amps input ? and isn't the PFL meter here to help you measure this and reduce it if necessary? I thought the PFL was there to help you present the highest cleanest signal to your amp and that sending a distorted signal from your mixer to your amp can damage your speakers as well ...not sure where I got this from and could be wrong so any comments most welcome...

[ChrisPointon 0]

QUOTE

just read through all these and noticed a few comments about amps clipping - isn't this sometimes due to the signal from the mixer being too high and overloading the amps input

 

Correct, however if the P.A had the capacity to handle the size of venue comfortably, then the mixer would not need to be pushed to beyond its 0db level (usually around 0.775v or 775mv). However once the signal gets pushed beyond that point then the Amplifier will clip.

 

Another common occurance of this is when a mismatched system is used, say a mixer with a nominal output of 1.3v or 1.44v is connected to an amplifier with an input of 0.775v - that threshold of clipping will be reached on the amplifier at a far lower level on the mixers faders.

 

Also, has the output voltage from the mixer rises, so does the level of distortion from it, so once you go beyond the 0db level then you stand a good chance of the audio sounding less sharp, or even getting some levels of distortion into the signal chain. For this reason it is not a good idea, to turn your amplifier gain controls down, and push your mixer to full power. Ideally neither the Amplifier of Mixer's gain controls be cranked to the Max.

 

Everybody idea's on this vary, but I personally leave the amplifier gain controls at around 8, and never push the master faders on the mixer beyond about halfway. I also have a compressor Limiter on the system which will prevent levels of above 0db from reaching the amplifier - causing it to clip.

 

QUOTE

isn't the PFL meter here to help you measure this and reduce it if necessary?

 

Actually the LED VU Meter type bargraphs shouldn't be relied upon, since they can be well out of accurate calibration. In fact i've run mixers and amps (with the same input sensitivity of 0db) and had the VU meter on the mixer indicating -8 and feeding the amplifier which indicated the level was -4db http://www.dj-forum.co.uk/html/emoticons/533.gif . In fact some are so inaccurate that they are little more than decoration.

 

[funkymook 0]

Cheers Chris - thems lights are pretty though!

[heretochill 0]

Having read through this topic, I am amazed at how little some of you guys will settle for .. the rules are simple .. you just can't get a square peg to fit in a round hole!! If ya want to play bigger rooms .. get some power for goodness sake. As for the latest comments about Peavey Messengers, They have a passive x-over built into the subs and this does NOT alter the impedance of the rig at all. Therefore, if you link the mid/tops to the subs using the high-out on the subs, the rig still only imparts a 4ohm resistance back to the amp (not 2 ohms as you may think). These cabs are very conservatively rated by Peavey and the Black widow drivers in the subs alone will easily handle 500 watts each without melting the voice coils! I think 650 watts a channel to the MEssengers will result in a lovely crisp sound .. just be sureto use some decent processing at pre-amp or they have a tendency to sound all mid-range. You should all check the "slew rate" of power amps too as a poor response from this will result in major losses of power to heat if driven hard. This gives the impression (correctly) that high volumes cannoit be achieved as the night progresses (not what you want at all). I myself messed with loads of different configurations before settling for JBL concert Subs (1200 watts per cab @4ohms) These are driven by the excvellent Audiohead amp 1200x1200 @4ohms . Mid toip is taken care of by an awesome pair of Peavey Hysis4's (700watts RMS per cab) driven by Studiomaster 800x800 @4ohms. I use a Electrovoice x over to control the subs, and a 30 band equaliser to make sure the whole lot stays in check.

[C.S 0]

Hi and welcome to the forum heretochill,it would be nice if perhaps you could give us a little intro into who you are in the new member section, See you know what you are talking about and also saw you were asking for a gig in another section of the forum so we need to know a little more about you. Regards Chris S. Sorry to take this off topic guys

[haggis 0]

Hi Guys this is my first post so hopefully nobody will say "read all the other messages on this topic!"

 

I have inherited an InterM R300 amp - 2 channels with "stereo" or "bridged mono" and the minimum impedance is stated as 4 Ohms/channel for Stereo or 8 Ohms bridged.

 

I also got 2 x RCL LPA EM1260 400 Watt 8 Ohm speakers.

 

The main purpose will be for large family gatherings of 80 - 90 people. My wife has lots of sisters (sorry, all spoken for!). Obviously we rent fair sized rooms for such a number and I wondered if someone could advise:

 

a) Is the amp/speaker combination suitable?

 

b) How should I use the amp - Stereo or Bridged Mono?

 

c) Any other suggestions or comments?

 

Thanks in advance for any help.

 

Haggis

 

 

[DJ Marky Marc 0]

run the amp in stereo......

[haggis 0]

Thanks for the fast resposne .....

 

If I added two more 8 Ohm speakers that would let me get more out of the speakers as long as I run them in stereo?

 

I think!!

 

Is that right?

 

Haggis

[DJ Marky Marc 0]

think of it this way.

 

your amp is infact two mono amps in one box.

 

each mono amp can work at 4 or 8 ohms....

 

if you use one channel eg the left speaker connection with one speaker you will be running an 8 ohm load...

 

add the other speaker to the right channel for stereo...

 

ok now the teky bit

 

two 8 ohm speakers on one channel would be 4 ohm load...

 

you could infact run 4 speaker if they are all 8 ohm ones.....

 

now for bridging, to keep it simple when you bridge your two mono amps to Make one big mono amp , you get more power but lose the ability to run 4 ohms or two speakers in your case....

 

keep it stereo... and run 2 or 4 speakers......

[otronics 0]

QUOTE

Actually the LED VU Meter type bargraphs shouldn't be relied upon, since they can be well out of accurate calibration. In fact i've run mixers and amps (with the same input sensitivity of 0db) and had the VU meter on the mixer indicating -8 and feeding the amplifier which indicated the level was -4db  . In fact some are so inaccurate that they are little more than decoration.

 

Some mixers add around +3db or more on their master outputs. This is for use with long cables etc.

[huracain 0]

hello i am totaly new just setting up my equipment read all about ohms law fweeeee il give it a miss and just ask the question

 

i have

gemeni xpm 1200 amp

ohm rw 5 350w 8 ohms speakers

 

are these ok .or am i under running them or over running the speakers

i oviously can turndown the power on each channel from the amp.

 

thank u for any help