When choosing an Amp / Speakers, firstly always find out the Wattage of both in RMS and not Peak, Music Power, or PMPO which are figures reserved for hi-fi equipment and very misleading!. Disco equipment outputs are measured in Watts RMS, so always go off these figures!.

The ratings of power amplifiers are usually based on Watts RMS into a 4ohm load (4 ohms is 2x 8 ohm speakers connected to one channel) so on the back of an amplifier you may see something like:- 2x 400 Watts RMS into 4 Ohms - 2x 275 Watts into 8 Ohms. This means that the amplifier delivers its full rated power into a 4 ohm load (or 2x 8 ohm speakers connected to one channel). The lower figure represents the output that you would get from the amplifier if you only connected one 8 ohm speaker per channel.

It is a common misconception that if you have a 400W per channel amplifier that you will always get the full 400W output. You won't unless you have the full 4 ohms of load connected.

Most speakers are rated at 8 ohms (You can get 4 ohm speakers but they are few and far between and often used for in car entertainment. Some manufacturers such as Ohm and Carlsbro offer the same series in either 8 or 4 ohm loads but it is usually safe to assume that a speaker is 8 ohms, but double check before you buy).

Always, make sure that your speakers are rated ABOVE the RMS output of your amplifier, since most amps are able to push above their rated output for milliseconds, during loud bass passages, or if you drive the amp to "Peak" or "Clip" - often indicated by a red led on the amp!.

For instance you can use 300 Watt Speakers with a 200 Watt Amplifier, but using 200 Watt Speakers on a 300 Watt Amplifier will cause you problems (and expense!)

Again, check the "Ohms" rating of the Amplifier and Speakers. If an amplifier has a rating of 250W at 4ohms and 150 Watts at 8 Ohms - you could reasonably connect a pair of 200W 8 ohm speakers to it since the amplifier will only deliver 150 Watts into them, and still give you a 50W safety margin!.

Even so, it is still possible to damage HF horns in speakers by over driving the amplifier, even if the speakers are rated above the amp. Occasional Clipping or peaking of the amplifier is acceptable, but if you find that this is happening on a regular basis, or if the clip led is permanently lit then it is time for an upgrade of the amp and speakers!.

Depending on your requirements, this is what we would suggest:-

Budget System:-

(1x) Soundlab SP500 (2x 250W @ 4 ohms Amplifier)
(2x) Soundlab 15-200 15" 200W 2- Way Loudspeakers
Leads

Price:- £290.00 + Delivery

Pro System:-

(1x) Soundlab SP800 Amplifier (2x 400W @ 4 Ohms amp)
(2x) Ohm RW3 15" 300W Loudspeaker
Leads

Price:- £599.00 + Delivery

Ohm System:-

Mc Gregor SS1000 Slave Amp (2x 500W @ 4 ohms amp)
(2x) Ohm RW3 15" 300W Loudspeaker
(2x) Ohm RWS 15" 300W Bass Bin (Matches RW3)
Leads

Price:- £1039.00 + Delivery

Of course, there are various other combinations that you can use to suit your requirements / budget, and these are just an example.

The specs on those "suggested" systems -almost- got confusing/worrying until I remembered your comment of "always assume that speakers will be 8ohms".

EG: Seeing a 300watt speaker on a 400watt amp. (poor ickle speaker! )

But when you take the impedence into account....you (and your speakers) can breathe a sigh of relief. As it was an amp offering 400watts @ 4 ohms, which is only 200watts into 8 ohms, so each 300watt speaker only gets 200watts pushed into it.

Safe...

yeah but dont forget u can damage a speaker too by under running them in terms of not enough wattage!! Obvioulsy this leads to distroting and can distroy the voice coils

Either way look for an even match in both speakers and amps wattage

Cheers

Rick

I have never quite got my head round this amp business Do I take it that per channel means both left and right side speakers?What if I wanted to take a cable from the back of my speakers that are on stands,to a couple of speakers on the floor.The other alternative would be to take two extra cables from the back of my amp to the floor standing speakers.Which would you suggest?My amp is a PV 8.5C
Perhaps you could explain - in laymans terms please-
425W RMS@4 ohms;550W RMS@2 ohms(per channel)
850W RMS@8 ohms;1100W RMS@4 ohms (bridged)

Okay:

A "Channel" on an Amplifier refers to the individual module or circuit inside the amplifier which takes in a signal mono low level signal and boost's it to drive a loudspeaker(s).

All Stereo amplifiers have 2 "Channels", one channel handles the left hand signal and speaker, the other obviously does the same for the right. Other than some amplifiers sharing the same powersupply, the internal Left and right "channels" or circuit boards are seperate, which means in the event of a loudspeaker problem or component failure the opposite channel should continue to work

Okay - the load which determines how much power your amplifier provides to the speakers is dependant on the actual number of speakers connected.

The load is called the impedence, and the level of impedence is measured in "ohms". Most amplifiers will only work to a minimum of " 4 Ohms" however some amplifiers such as your Peavey, and QSC etc will work into a 2 Ohms load (often refered to as being "2 Ohms Stable". However this is rarely encountered since it needs a lot of speakers to be connected to acheive this.

Working out Ohms:-

Most Disco and P.A loudspeakers are rated at 8 ohms, so connecting one 8 ohm speaker to one channel of the amplifier will present a load of 8 ohms to it.

Plugging in an additional 8 ohm loudspeaker into either the existing connected speaker or the second socket on the same channel of the amplifier (if fitted) will equal 8 ohm + 8 ohm = 4 Ohms load to the amplifier (not 16 like maths would suggest!).

To get 2 ohms you would need to connect:-

8 Ohms + 8 Ohms + 8 Ohms + 8 Ohms = a 2 Ohm Load, so to get 550 Watts from one of your amplifiers channels you need to connect (4x) 8 ohm speakers to it.

Given the fact that each channel is identical and seperate, your Amplifier has the capability of running 4 x 8 ohm speakers per channel! - a total of 8 speakers - which is why I said to ignore 2 ohm ratings when buying an Amplifier and concentrate on the 4 or 8 ohm wattage ratings!.

2 Ohms of load on the Amp can also be acheived by connecting (2x) 4 Ohm loudspeaker cabs to the same channel. Although 4 Ohm Speakers are usually used for Home Cinema or in car use, but some manufacturers such as Carlsbro and Peavey offer 4 ohm versions of some speakers.

So some common speaker combinations are below

8 Ohms load can be acheived by connecting either

1 x 8 ohm speaker

or

2x 16 ohm speakers (very rare nowadays)

4 Ohms load can be acheived by connecting:-

1x 4 Ohm speaker

or

2x 8 ohm loudspeakers

or

4x 16 ohm loudspeakers

or

1x 8 ohm and 2x 16 ohm loudspeakers

Bridge Mode

Okay "Bridge Mode" means combining both the two internal amplifier boards together to double the rated output. By doing this, your amplifier ceases to be a 2 channel or stereo amplifier, and becomes a Mono amplifier with the combined power output of BOTH the amplifiers into half the load.

For example your Peavey usually provides 2x 425 Watt into 4 Ohms of load, which means connecting 2 speakers per channel (A total of 4 speakers) to get this.

However if you switch the amplifier into "Bridge Mode", it will merge the output power of both amplifiers into a single output. This means that by having both channels work together you could get 1100 Watts of power into 4 ohms which means only connecting 2 x 8 Ohm Speakers. However the audio coming out would be Mono since you have combined both the Left and Right channels to work as one!.

Oh your so sexy when you talk technical LOL
I will admit to have never got my head around bi-amping

i always match the speaker handling with the amp's output,eg, a 300 w rms amp with 300w rms speakers, speakers usually get damaged when the amp clips, so under powering is definately worse ! + bi amping is the way to go mikee, one amp for the subs and one for the mid/tops.

Just a couple of questions on the amp/speaker subject. If I connect another couple speakers to the existing ones I have like DJTREV said then does that then not reduce the resistance and so increase the output of the amp or doesn't it work like that? The problem is I don't know what rating the other speakers are as they look homemade. Also is it better to buy some more cabs if I was to upgrade or put some higher wattage rated drivers in the ones I've got.

Thanks
Loz

Sorry Missed this post , unlike me I know but hey..it happens!.

Right, Most Power Amplifiers will only work down into a 4 ohm load, this equals 2 x 8 Ohm speakers connected to each channel. If you connect anymore speakers, then you will overload the Amplifier and either cause it to overheat or damage it.

If you are presently only using one speaker connected to each channel of the amplifier, then you can increase the power output by about 30% - 35% by connecting another speaker per channel - however make sure that the speaker is rated correctly.

With regard to upgrading, then it is advisable to buy a new pair of speakers rather than upgrade the existing ones. If you do upgrade then you will need to consider uprating the Tweeter / Horn and perhaps the crossover as well if fitted. It isn't really practical to upgrade only the main loudspeaker driver, since there is the other components to consider, and these could be damaged by excessive power.

Even if you upgraded your speakers, then if you keep your existing amp, then you wouldn't get anymore power from it, simply by upgrading the speaker , an 8 ohm speaker is an 8 ohm load regardless of whether you upgrade the driver from 200W to 400W. So basically what I am trying to say is that if you are only getting 200W from your amplifier into your existing speakers, then even if you put a higher rated speaker into the cabinet, the Amp will still only deliver 200W!.

The only way to get more output from your Amp is to:-

(1) If you are only using 1 pair of speakers, then buy and connect another pair, so that you are using 2 speakers per channel.

(2) Buy a higher wattage amplifier

(3) The Combination of (1) and (2) which will be required if your new Amplifier is rated above that of your existing speakers.

Thanks for the info Chris. Can we talk about cd players on this forum or is it just amp and speakers. I raised a question on the "introduction forum" and got a reply from Gary, but thats all so far.

Cheers
Loz

QUOTE (Loz @ May 19 2003, 10:33 PM)

Thanks for the info Chris. Can we talk about cd players on this forum or is it just amp and speakers. I raised a question on the "introduction forum" and got a reply from Gary, but thats all so far. Cheers Loz

No, you can talk about / ask advice on any D.J related equipment on this forum. However, I would ask that you keep it within the buying equipment area of the forum, and that you start a new thread

hi all,
great forum.

Just like to point out a mistake that Chris has put, now if im incorrect ! then im sorry.
but from the advice in telling people in the original post that its best to have the speaker system lower than the RMS of an amp is so incorrect.

eg, Martin Audio F12" speakers are rated at 300w rms, but they have a peak of 2000w rms, they recommend to run a nice clean signal of around 500w into them. Now i know of 2 of the largest PA companys that use the martin Audio F15s for sky sports events, and there rated at 400w and 2000peak and they stick 900w rms into them speakers.

Its always best to run a nice clean signal into a speaker. Obviously, if your going to take a cheap budget speaker that has its speaker ratings changed to make them sound good

eg.,
100 rms
200 prog power
300 peak power

and they state there speaker is 300w speaker when really its 100w rms then its best to not go above 300w rms amp power or the speaker will fry.

Also chris,
you have stated to get a 2ohm load out of one amp channel, you can add 4 x 8ohm speaker cabs to he load. This is incorrect, and please anyone who will feel like sticking 4 8ohm speakers to one channel of an amp will get a nice blown amp ( if using a cheap amp ! or into protection if using a good quality QSC or crown amp etc...)

you always half the load.

1 x 8ohm speaker = 8ohm
2 x 8ohm speaker= 4ohm
3 x 8ohm speaker = 2 ohm

adding a 4th will give problems.

the only time you can add a 4th speaker to per channel is if you have a 16ohm speaker, these are available, but only with pro tour series speakers or speical order.
After 10 years of working as a pro. DJ and sound and light engineer, people do need to know the proper way of doing sound and light....or BANG !


Ade

Even after reading all this thread and it's very helpful info and advice i still have a couple of questions.
I have a Warrior KT-600 amp which throws out 300w rms per channel (180w 8ohms, 300w 4ohms). I connect one 250w speaker into each channel no problem. If i connect a another speaker onto the same channel (making the output 4ohms) does it throw 300w to each of the 2 speakers, and if so wont it blow my 250w speaker. Also if i run the amp bridged it gives 600w, and if i connect only one 250w speaker per channel wont it blow the speakers as well.
I am gradually getting to grips with the technical side but still need help along the way.

Adrian - there are two schools of thought on the subject of matching amps to speakers. I believe that Chris's advice is wise given that many users are inexperienced in what they should or shouldn't be hearing.

I, like you, feel more comfortable with plenty of amp overhead, in the knowledge that the sound of an amp clipping is probably more insidious than that of a speaker becoming distressed. I would hope that any sober person would back off at the sound of overdriven speakers but it is all too easy to simply "wind it up"!

On the subject of impedance matching, I think you'll find that four 8 Ohm speakers in parallel, will indeed present a load of 2 Ohms. Imagine two banks of two speakers (resulting in 4 Ohms each). That will give you 2 Ohms.

I've been fishing about in the back of my mind for the long forgotten, (although simple) formula. Could it be (for three speakers) 1/8 +1/8 + 1/8 = 1/R? This would give 3.75 Ohms, which is about correct.

Thanks for backing that up Rob, I was 90% certain that 4x 8ohms Speakers = 2 ohms, but wanted to be sure before I posted again. It's been a while since Ohms Law and Speaker Impedence Formulas for me

I've found a couple of website's which give the Formula as in your post, so I think we'll take that as being a correct assumption.

What would be the best amp to drive a pair or JBL EON 1500's?

i would go for a nice crown CE-2000 amp to drive these, or if looking for something lower in price, maybe a Matrix UKP 1000

Ade

QUOTE (BigE @ May 30 2003, 08:26 AM)

Even after reading all this thread and it's very helpful info and advice i still have a couple of questions. I have a Warrior KT-600 amp which throws out 300w rms per channel (180w 8ohms, 300w 4ohms). I connect one 250w speaker into each channel no problem. If i connect a another speaker onto the same channel (making the output 4ohms) does it throw 300w to each of the 2 speakers, and if so wont it blow my 250w speaker. Also if i run the amp bridged it gives 600w, and if i connect only one 250w speaker per channel wont it blow the speakers as well. I am gradually getting to grips with the technical side but still need help along the way.

Your Amplifer will only Deliver a MAXIMUM of 300 Watts per channel in TOTAL into two speakers (4 Ohms).

Basically by connecting two 250W Speakers to one channel of your amplifier, you have the Capacity of 500W of power handling (2 x 250 Watt Loudspeakers). The maximum power that your amplifier will drive into two speakers is 300W, therefore delivering 300W into 500W worth of Speakers is perfectly safe .

For a safety margin, I would also recommend that each speaker is rated above the 8ohm power output of your amplifier. For instance your Amplifier is rated at 180 Watts into 8 ohms, so I would suggest that each connected loudspeaker is rated above 180W. For instance you could still connect 2x 200 Watt Speakers to one channel of your Amp (Total 400 W) and have a nice safety margin (300 Watts from the Amp, into 400 Watts power handling of 2x 200W speakers connected to it)

Thanks for that Chris, as always explained in a simple and easy to understand manner for novices like me to understand.
Now i feel a lot better as i thinking of purchasing a pair of bass bins for my mobile disco.
In your personal opinion is it in a mobile disco's interest to have bass bins as well as your normal speakers, for all types of functions.
Once again thanks for your help.

Haha what up doggs! Virgin poster here.

Ok... just out of curiosity, besides all this math and formula mumbo-jumbo... what companys/models do you guys recommend for amps and speakers. I live in the states soooo we may not have as good quality as you guys in the UK.

I'm looking for some good stuff to practice but also to play small gigs parties just for now. I heard somehwere you want to get a very good amplifier first and then you can always upgrade your speakers later. Is this true? Any suggestions?

Thx guys.

Max.

hi guys ... i need a bit of advice here...

my system includes 2x prosound 10 200w speakers and a prosound 400watt amp purchased as a package, mounted on stands.

i am curious as to how loud i can push these speakers,before they blast, genuinely as a new piece of equipment, i have anxiety towards the equipment, being my own, and not wanting to blast the speakers

can anyone give me any pointers as to this matter?

one other question...

i have noticed that on the front of the amplifier there are 2 knobs ... 1 for each chanel ... along with 2 peak LED lights.

i am aware that a peaking LED light means that the amplifier is being put under strain, but what is the purpouse of these 2 knobs on the front of the amp, and what position should they be at? (i curently have them turned to a little over half way on the dial)

take care for now

A lot of useful information here,
I thought I had this sussed by using the same equation as Adrian
1 x 8ohm speaker = 8ohm
2 x 8ohm speaker= 4ohm
3 x 8ohm speaker = 2ohm
1 x 4ohm speaker = 4ohm
2 x 4ohm speaker = 2ohm
But I’m unable to work it out, when it comes to using mixed Ohm speakers.
Can anyone tell me what the rating would be for 1 x 8ohm speaker with 1 x 4ohm speaker on each channel?

Firstly I don't recommend using mixed ohm loudspeakers on an amplifier, since occasionally it can become unstable, and you'll always have one loudspeaker louder than the other.

Here we go again!! I've been to buy a new amp today and was talking to the bloke in the shop about rating speakers with amps etc... and his view is that your amp needs to be bigger than your speakers to prevent clipping. He called it "headroom" he drew a diagram explaining about the sound waves and how if your amp does'nt give you enough signal then the sound waves are clipped, causing the sound to become distorted. I know this is pure insane but I left with a 2.6kw amp which I'm going to drive some 400w rms cabs, all the bloke said " be careful and it will be fine!!!

and did he go riding back to the ranch after giving this advice .

Any amplifier will clip - just crank up the volume on the mixer . However theoretically the guy was correct....you will never hear the amplifier clip since it will have blown your speakers long before you get there!.

That's nearly 2000w of headroom !!

Next purchase should be some speakers to match the amp I think

you must remember that a lot of power will be lost in heat.

I have another post similar to this one in the main DJ section of this forum.

It would have to be bloody hot to 'lose' 2000w !!

Even a class A Valve amp wouldn't Lose half that!. . Perhaps i'm going about it wrong, maybe I should sell 500W Amplifiers with PC Speakers as a package they'll be fine as long as you are "Careful".

I'll buy a set !!, active or passive ?

Yeh I know what you're saying, and I know it's very risky but the difference in price from a 1500w to a 2600w was only £60 so I thought it would be a good investment for the future. I did actually go with the intentions of upgrading my speakers but they were a bit expensive at the moment. I was offered some second hand speakers made by a company called "Pure concept audio" the guy said they were the best speakers he had in the whole room, has anyone ever heard of them and if so what they like?

900w for £60......What make from Japan is it

It's made by a company called Peavey which I think are American are'nt they?

What's the model number of the amplifier? (Usually tells you on the front or the specification plate on the back).

Sorry, never heard of Pure Concept Audio but I'm happy to confirm that Peavey are legit and (in my humble opinion) make good quality products.

I'd recommend some Peavey Messenger Pro 15's to compliment the amp but then I'm biased as they're what I use..................

Regards to all

Ian Stuart

The amp is a PV-2600 is that what you meant Chris?

I've seen the messenger PRO15 cabs, there is also the UL15 series as well, we listened to some of them yesterday and they do sound very punchy and clear. I don't know if to get the pro15's and the subs as well or pay a bit more and get the UL15s which are 500w rms

Okay I'm not a PV dealer but it was the one I thought , in which case there is good and bad news.

The good news is that your amplifier is only actually rated at 2x 900W RMS into a 4 ohm load, and NOT a 2.6kw as you originally stated. The bad news of course, is that you either jumped to the wrong conclusion as to its power rating, or that the salesperson misled you!.

Here are the PV-2600 Specs:-

I've heard of 'Audio Concepts' which could be the same company based, I believe, in the Cambridge area. I use one of their amps (AC5000) as a back up or if I tri-amp my system when I use it for the horns. I bought the amp second hand some 3 years ago and never had a problem with it.

If the speakers are anything like the amp then I would class them as a budget range rather than 'top of the range'

PaulS

Yep - A lot of manufacturers are guilty of this crime but it's the Americans who tend to favour over selling ratings the most! . Peak / Program are much the same figures. Always consider the RMS / Continuous figures since these are the figures which actually mean something.

Peak / Program / PMPO - are figures which can be handled by the speakers for very brief periods of time. What periods of time depend on the manufacturer but they never seem to openly give it away . On average it could be around a few second bursts such as loud peaks or heavy bass passages certainly never more than a few minutes and not an entire gig.

RMS / Continuous / RMS Continuous - Accurate figures that your speaker will handle continuously for indefinite periods of time without stress / damage or your tweeters overheating.

In short pay attention to RMS / Continuous ratings on the speakers and match that to the RMS Rating of your Amp. Therefore with regard to the PRO15's - if he has already got 400W RMS speakers he would (power wise) by downgrading to the 250W Rating of the Messengers!. They certainly may be a better sounding speaker with better SPL figures but at the end of the day he risks damaging them when driven from a 540W RMS Amplifier.

I've repaired speakers which have literally being overdriven so much that the power resistors on the crossovers have got so hot, that they've scorched the pcb and melted the solder contact from pad and the resistor has literally fallen off the PCB. This would usually be the result of connecting a 500W Program Speaker to a 500W RMS amplifier and running at full power all night .

With regard to this debate, it is a common conclusion that RMS are the more accurate figure which can be backed up from around the net on Car / AV / P.A Sites, some linked examples are below. Sites which state differently are usually manufacturer based, where they are trying to sell a speaker on its peak rating!.

LINK 1

Link 2

The More Useful link

Either way - don't believe what the salesman tells you - until you get the chance to check it out for yourself. It usually costs a small fortune in the long run, and remember that Speaker Warranties are a very grey area and don't cover damage caused by poor sales advice.

Thanks for that Chris, very imformative.

Ian Stuart.

Peavey seem to have a strange way of measuring the wattage of their speakers

My son has a pair of ST15’s these are rated as:
150w RMS
300w Program
600w Peak
Running these through a 2 X 120w RMS amp they sound great & they have plenty of output. I have read that some people regard a small system like this as “only good for a bedroom DJ-ing but this has handled groups of up to 250 with ease”

Their Pro 15’s are rated as:
250w RMS
500w Program
1000w Peak

And their UL15’s are rated at:
500w RMS
1000w Program
2000w Peak

Chris,
You stated that Program is the same as peak, are Peavey pulling a fast one with their figures ?

I would add Peaveys web site BUT I don’t want to raise Chris P’s blood pressure.

As above - always read the RMS Figures.

Running a 150W RMS Speaker from an Amp channel giving 120W RMS is perfectly okay and allowing 30W RMS headroom is a reasonable safety margin for this level of wattage.


Many people are under the impression that they need to buy an entire new P.A system to make their existing one louder and capable of doing larger venues. This is not always the case. Remember that you can add more power and flexibility to your system simply by adding another pair of 8 ohm speakers to your existing ones.

For instance an amp delivering 300W RMS @ 8 Ohms and 500W @ 4 Ohms. With only one pair of 8 ohm speakes connected, the total power RMS output is 600W. Add another pair of suitably rated 8 ohm speakers and the total power output is increased to 1000W RMS. Thats an increase of 400W RMS simply by adding an additional pair of speakers. The most efficient way of doing this is by using a pair of subs and 15" Full range cabs at larger venes. Then just using the Full range cabs on their own for smaller venues.

BUY POWERED SPEAKERS

Thanks for the Info Chris. I always get a little confused with the Ohms ratings,a dn power ratings. So have always got speakers that mach exactly to the amp. The info you have given helps me and might not need to buy another amp to run another pair of speakers to improve on power.
Cheers

OK - advice needed please!!!!

I am currenly running a pair of Peavey Eurosys 500xt's with a Numark Dimension 3 amp - With the amp volume at 50% and the mixer near full the amp is clipping.

The amp runs 475W RMS @4 ohms
The speakers 500W program / 1000W peak (No RMS rating given - but I suspect they might be 250W RMS)

The amp does have a Low Cut Filter but I don't know if this will help the clipping situation.

All advice welcome

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?

Sorry for all these questions - ps not alot to spend immediately

Thanks

Vinnie

Has the clipping always been there with this configuration?

From your description, I would say you have a mis-match between the mixing and amp.
What is the output from the mixer (1.2v?) and what is the input of the amp (0.775v?). If the figures in brackets are what you have, then the mixer is overloading the input of the amp - bingo - lots of unwanted crap.
Does the mixer have swithable outputs (0.5v, 0.775v. 1.0v, 1.2v, 1.5v), if so start with the lowest setting.

There is a chance that you may at some point damaged the speakers, nothing like a damaged horn to make the system sound like rubbish.

Also try turning all the mixer levels to zero, put the amp on full, then ease the levels on the mixer up a little bit at a time and see what the does

My 2 watts worth