I recently purchased a 500w powered mixer. The output is 250w @ 4ohms on two channels. I am having the hardest time pairing speakers for this. Some advice I have received is questionable so I am hoping for clarification.
One guy was suggesting a pair of Squires at 300w @ 8ohm. He stated the ohms would have no impact.
Another guy suggested a 60w speaker @ 8ohm with a peak of 120w. He said if I daisy chained them I would get full power out of the amp.
My concern on the first guy is a drop in sound from underpowering the speakers. The second has me worried that I would blow the speakers.

Can anyone please clarify this? Thank you very much.

Also does anyone know of a brand of 250 to 300 w 4 ohm PA speakers?

Hooooo boy. This is a big can of worms, right here...

Firstly: If you still can, take the powered mixer back. You'll thank me for this move later.

Now, we'll address the core issues...

1) The guy who was talking about low-watt speakers was relatively close to correct. The guy who said "Ohms don't matter" is an idiot, and you should keep this in mind whenever he offers sound reinforcement advice.

2) I'm going to attempt to give you an overview education on watts, ohms, and other things you need to know about speakers and amplifiers that will give you at least a clue about what you need to shop for to solve your PA problems. I'm also going to attempt to do it in Cliff's Notes form, which means I'm going to have to leave a lot of stuff out. If you don't understand something, ask.

Here we go....

First of all, when you're shopping for PA gear, you need to start with a pair of speakers, and then match your amp to them.

Why? Because the speakers you buy will tell you exactly what you need in an amp, if you understand their specifications.

Let's talk about watts for a second. Forget them. There, we're done.

The amount of power a speaker can take before blowing up is meaningless. What is meaningful is how much volume that speaker can put out, and that isn't measured in watts, it's measured in Sound Pressure Level - or SPL, expressed as Max SPL = xxx dB (decibels) - and how efficient a speaker is - as in how well it turns the input power into output volume - this is also measured in SPL - expressed as Sensitivity = xx dB/1W/1M - this means how many decibels the speaker produces with one watt of input power from one meter away.

You want to invest in speakers that are rated very high in both these categories. Obviously, the higher the Max SPL, the more volume you'll get out of them. The higher the sensitivity, the less amplifier you'll have to buy to drive them effectively.

For a little perspective, let's talk about the relationship between input power (in watts) and SPL's.

It takes twice as much power to increase output SPL by 3dB - this is a law of physics. It is inescapable. Why do you care?

Because if you're looking at two pairs of speakers, and one pair is 92dB sensitive, and another is 98dB sensitive, that means it's going to take four times as much power to get the same volume out of the first pair versus the second pair.

I don't know about you, but I'd much rather tote around, say, a 200W amp than an 800W amp - just the sheer weight is enough to sell me on that! Never mind the expense!

Now then....

Amp / speaker matching!

First rule of shopping for amplifiers - don't believe the hype!

Every amp manufacturer likes to post the biggest wattage number they can on their amps. Why? Because that's what we've been conditioned to believe is important!.

Here's what's really important: How you're actually going to use the amp!

And this is where we start talking about Ohms - another fun topic.

The Ohm rating of your speakers dictates how your amp will function. Just because you have an amplifier that will put out 1200 watts per channel into 2 ohms, doesn't mean you'll ever get that out of it. Why? Because if the back of the speaker says "8 ohms" and you're using one speaker per channel, your amp is going to function in 8 ohms, stereo. If you "daisy chain" - or run two 8-ohm speakers in parallel, you cut that resistance in half, meaning the amp can now run in 4-ohm mode - but if these are the only two speakers connected to the amp, you have to run in "bridged mono" mode - or you'll blow the amp up for lack of a load on one side.

Moving along to the amplifier:

Forget the "advertised" watt ratings on the amp. They're peak ratings, and usually a sum of 4-ohm or 2-ohm stereo operation.

What you need to know about the amp is its RMS or Program output. These are the numbers that will tell you what the amp is going to put out on a constant basis. You also need to decide up front how you're going to set up your speaker system, because that will dictate which amp number you're after.

In my PA system, I run my mains (two 8 ohm, in parallel for 4-ohm load to the amp) in bridged mono on one amp, my monitors (same) on another, and my subs (each speaker is 4-ohm) on left/right on a third amplifier, which delivers more output power than bridging as a general rule.

If you intend to only use the two speakers, you're going to look at the amplifier's RMS or Program output in bridged mono at 4 Ohms, because that's the load you'll be presenting to it.

Cardinal rule of amps and speakers:

You will destroy a speaker far faster with an underpowered amp than an overpowered amp.

Why? Because you're going to turn the lower powered amp up all the way, which pushes it into distortion. Distortion kills speaker coils - it causes them to heat up. I've seen PA speaker coils catch fire on stage from being fed a distorted signal. Granted, they were cheap PA speakers (subtle hint) but it can happen.

Hope this helps, as a start point. Again, if you don't understand something from the above, ask.

That is a great amount of quality info. I am taking it piece by piece and plan what I am going to do. Thank you very much.

Griffinator has given you a solid layout of the fundamentals. I am not sure I agree with the portion I quote.

In any moderately well tuned system, it is easier to hear the signal flow/amp stressing (clipping/distorting) than it is to hear the transducers (speakers) stressing.

In my...few short years as a "live audio" guy, I cannot remember ever losing drivers to underpowered amps sending square wave (what Grif describes)...but I HAVE damaged a lot of speakers - woofers and horns, by sending either the wrong program material to them, or having them on an amp that was simply too "powerful".

Compressors and hard limiters at certain stages of your audio chain can help to preserve the life of your speakers...but this is what I tell most up and coming audio guys.

1. Mix at a position where you can clearly hear detail from your speakers. How are you going to make that most excellent, crystal clear, well balanced mix, if you can't hear all of the important details? This means that even if folks are screaming, you need to be able to hear your rig.

2. Mix at a volume level where it is comfortable. If you're not covering the target area, resist the temptation to crank it up more, and instead, if time permits, arrange to have more speakers and amplifiers.

...more later.

'Drew

and yes, I've been away for a looooong while.

OH MY GOD!

It's NYC Drew!

Loooooooooooooooooooooooooooooooooooooooong time no see dude!
How you been? Hope all is well with you.

Are you just passing by or will you pop in more often?

Good stuff, and WELCOME BACK, DUDE...

Now, my response:

Yes, you can hear distortion easier than you can hear speakers bottoming out (although most quality speakers have light-up clip limiters built-in so you can see when you're maxing it out)

But an amp that's underpowered to the speaker is going to be a source of constant temptation to turn it up - especially with a newbie's first PA system - because inevitably the instruments will drown out the singer and the singer will complain, and the volume wars commence.

In this situation, it's far more likely to wind up with a dimed amp and a dimed mixer sending squares to the speakers and frying the voice coils (underpowered) than blowing the voice coils apart without ever hitting the clip point (overpowered)

Certainly, the clipping issues can be mitigated with limters and compressors in the chain, but the uninitiated will have trouble managing feedback in those situations too....

Hello Miroslav, Griffinator,

For some reason, I thought the forums went teats up a few years back. Also, I thought (almost SURE) that Harmony Central or somebody took over operations...it did not feel the same, so I picked up my ball and went home.

I'll be around, re-acquainting myself with the place.


And Sir Griff, :), I certainly don't say what you are saying is incorrect...it's just that, in my experience in the backwoods up to now, I have never seen a blown speaker from square waves, FROM an amp that was under the rating for a speaker.

In a former life, I used to recone and recoil speakers...and being from a 3rd world country, pretty much EVERYTHING was driven to distortion, clipped, pegged, had a standing oscillating fan on it, what ever it took.

Check this out - a lot of the "DJs" (the Jamaican equivalent of US "rappers")...well, a lot (by % or actual #) mimic Buju Banton's style, which in itself, is something Buju did to mimic the sound systems of the late 70s and early 80s.

That effect was distortion. Not guitar distortion, but the type we are talking about here, where the voice / instrument sounds like it was mixed with gravel. Buju Banton's "hard core sound" is (was) an attempt to emulate the distorted sound he heard on early sound systems...and a lot of cats followed him.

What does Buju Banton have to do with the question at hand, you query?

To underscore my point that I am somewhat familiar with distortion, and exactly how destructive it can be.

To be totally honest, I HAVE burnt completely up, a bunch of voice coils, simply by having them on an amp, with the coil in the magnetic field, then removing the coil from the field. The coils normally start smoking in less than a minute.

One of the problems with square waves is that it displaces the coil to it's maximum, outside, or close to the outer limits of the magnetic field. Once the coil is out of, or away from the focus of the field, sheat happens.

...then of course there is the possible physical damage that can be done to the loudspeaker assembly with the square waves....

'Drew

So you're essentially saying that most loudspeakers are built to withstand square waves within their power rating.

No. As that statement is too broad to stand the scrutiny of the "tech bench" or court!

I am saying, that under the most usual circumstances, even the most unmotivated of audio guys would be able to hear and realize that their speakers are approaching electrical and mechanical fatigue in time to prevent total wipeout of the driver.

Of course, there are exceptions. Off the top of my head, I see more speakers blown when


1. +20dBv is sent down a line designed to work within ranges of 0dBv (ie, a really bad, full blast of "noise"). I have seen amps and speakers without adequate protection simply just die. But not in a good many years though.

2. The operator(s) of the PA system are too far from the speakers, so they can't HEAR the detail.

3. The amount of PA brought to the gig produces a SPL level BELOW that of ambient noise (audience louder than the PA).

In those instances, SOMETHING is gonna get blown, because people are trying to dance around the laws of Physics.

'Drew

I've been in situation #2 with a patched-together PA system, 20 feet from the speakers...

Hello everybody

I've been looking at buying a system for our band that plays worldmusic. We have some equipment already; a 24 track mixer and I've bought some old passive EV subwoofers (they do not have a crossfilter) from a band I used to play with.
We are trying to get a system together but we cannot spend so much money because we are all rather poor musicians.....

Though I've used systems before I do not know much about amplifiers and speakers.

So by asking friends, I've collected information together.
But a few things still worry me...

We have:
-a 24 track mixer, with a built-in crossover for the subwoofers
-2 passive subwoofers, specs 300 Watts, 8 ohm, 94 db
I'm thinking about buying:
-2 passive full range top speakers of 250 Watt at 8 ohm, 95 db
-am amplifier of 2x525 Watt/4ohm or 350 Watt/8ohm
or
-an amplifier of 2x700 Watt/4ohm or 450 Watt/8 ohm

One of my friends says it will suffise to buy just 1 amplifier to power these four speakers.
This is the way he says it can be done:
Connecting the two subwoofers to each other and one of them to the left output of the amplifier (connecting the amplifier input the the mono-out on the mixer. This mono-out has a low pass filter built-in)
Connecting the two top speakers to each other and one of them to the right output of the amplifier (merging the left and right signals of the main out of the mixer to the right input of the amplifier)
I know this makes everything mono, but it is attractive to us to have to buy just one amplifier instead of two.

I hope you understand my explanation...

My questions are:
1) Which amplifier should I buy? The stronger one or the weaker one? Could the 2x700 watt/4 ohm amplifier damage these tops of 250 Watt/8ohm?
2) Can it do harm to the amplifier to have speakers of different Watts connected to it's left and right output ?
Because the left side would have 2 speakers of 300 Watt/8 ohm attached to it and the side right would have 2 speakers of 250 Watt/8 ohm.

I hope you can help me...

Greetings from Holland

Yolanda

So your net would be 550W/4ohms (speakers are designed to run in parallel when you chain them like that, which halves the resistance). That 700W figure on the amp is likely peak, it's advertising.

Get the 2x700.

Thank you so much for your reply Griffinator!

Just one more question: So it's not dangerous for the amp to have more watts of the left output then on the right?

Thanks

Yolanda

As long as the amp has volume controls on both sides, there's no danger of blowing speakers from excessive power output.

If you run your system within it's capable parameters, unless something goes seriously wrong with your electronics, you will never blow speakers that are underpowered.

Specifically, understand proper gain staging, run your console at proper levels, and your won't drive your amp with square wave and blow up your speakers.

However, do the same thing with overpowered speakers, and you'll be buying replacement drivers a lot.

Hello everybody
I have now bought some top speakers, they are 200 Watt/8 ohm RMS (instead of the speakers of 250 Watts I intended to buy, the 200W speakers sounded much nicer). They are the EV ZX1-90 (200W cont, 400 W prog, 800 W peak).

We are now thinking of buying two amplifiers because the subwoofers (EV SB121) are 300W RMS/8 ohm and the tops 200W RMS/8 ohm. Both speakertypes have 94 SPL (axial sensitivity), if this is the correct way to translate that :-)

We don't want to blow up the speakers too easily or carry too heavy amps, but we also do not want to produce square waves or strain the amp too much.

What specs should we be looking for in the amps? Maybe about 20% overpowered in watts (considering the Ohms off course)? Or are there maybe also other things to keep in mind?

If you want ease of portability and proper power matching, get rid of what you have and get self powered speakers. There are many to choose from, JBL, Mackie, etc., and they all sound quite good. No worries about matching anything, plug the output of a mixer to the input of the boxes, run power to them, and you're done.

3 pieces plus some cables is the entire basic system, that fits easily in even a modest sized vehicle.

Hoping someone can help me here with making a decision....

I have purchased speakers.....I have 2 PR15 that are 400 W Program & 800W Peak @8ohms. I also have two PV118 base bins at the same ratings. I was planning to daisy chain 1 of the PR15's and 1 of the PV118's off of each side of the amp, effectively as I understand, reduce the total of ohms to 4 per speaker / side now? My Program Wattage is obviously 1600 Watts, now from what I understand Wattage doesn't mean much, here is where I am confused..... How large of an amplifier should I pair up with this system?

Any info or help would be greatly appreciated.

Thanks

BJ: 3 things you need to know...

1) You need a crossover. Period. Those bass bins aren't going to do what you want them to if you feed them full program signal.

2) Stereo is useless in a live application unless you have massive towers of wide-dispersion speakers (as in, drivers pointing at -45, 0, and 45) on each side. In a normal club with just one pair of mains, you're robbing half the audience of half your music if you mix stereo.

3) With all that in mind, you can chain up the two bass bins on one side and the two mains on the other side.

Ok to get this straight.....When coming out of the 1 side of the amp with the 2 base bins I need a cross-over to pull the high end of the signal out? I figured that if the frequency was too high, the base bin just wouldn't play it..... The specs on the bass bins say there is an internal crossover. I've heard mixed opinions about using a cross over. Not sure if it makes a difference, but I am playing recorded music, not Live. By pulling the highs & mids out, it will make the bass bin perform that much better?

Should I still be using a cross over if there is one in the speaker cab allready?


Thanks for the advice!

You should be using a crossover because it will make both the bass bins and the mains more efficient. The mains won't have to work as hard trying to deliver low frequencies, and the bass bins won't be wasting amplifier energy in the internal crossovers.

It's an easy step in the chain prior to the amplifier that will make both amp and speakers operate more efficiently.

Thanks Griffinator,

Is there somewhere online I can look up to see how to get all of this connected up?

Thanks for the help!

There's really not much to connect. The output from the mixer will feed into the crossover, which will then feed two channels, one highpass (mains) and one lowpass (subs) and you'll feed those to the respective channels on the amp, which will then feed the mains and the subs.