SOOOO, here is my live sound question, with photos!!!!!

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rockironwebb

senior newbie caveman
My bassist got a hold of a dinosaur power amp and a couple of before Christ speakers.
Photo included. Even though the amp looks like it has seen better days it works well and is sufficient for our practice needs. I have hooked the amp up to a 4x12 cabinet and it runs a signal very well. The speakers the came in the deal completely suck!!! They are old and Sound absolutely muddy and I would rather not waste my electricity even hooking them up. I am the drummer of this outfit and since I have the practice space, I am by default, "The keeper of the Gear". I don't mind this at all.
Question NOW!!!!!
I am now willing to either buy a set of PA speakers that are worth using, or if more cost effective, purchase replacement speakers and stick them in the old boxes.
I have read a little about watts, ohms and such but I am a little confused about what should be used to power what.
The power amp is two channel, 200 Watts RMS per channel.
We would probably use both channels.
Should I look for 400Watt speakers?
should I get 200Watt speakers?
Would I use a different speaker(s) for each channel???????????????
I would appreciate some knowledge.
 

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The Peavey CS series amps might not be new or the best sounding but they were built like the proverbial brick ****house and tend to last forever.

The user manual is available online HERE. It might be of use because it gives the full spec. It also indicates that you can either run in two channel mode or in "bridging" which lets you put all the power into a single speaker. This latter feature might be of use to you because the CS400 isn't all that powerful.

Conventional wisdom is that, to avoid clipping, you actually want your amp to be about 1.5 to 2 times the rated power of the speaker. This might be an issue with the CS400 though because it's only rated at 120 watts RMS per channel into 8 ohms (200 watts into 4 ohms) or 400 watts into 8 ohms in bridge mode into a single speaker.

The trouble with all these numbers is that you have to read your speaker specs really carefully. Some talk about RMS, some about "continuous" which is similar but not identical to RMS...and others talk about "peak".

The other thing you'll find is that there are huge differences in speaker efficiency. Well designed ones can put out vastly more level for the same power than the cheapies. The spec to look at to compare efficiency will be "xx.x dB at 1 watt at 1 metre" or something similar. The higher the number, the more efficient the speaker. You can also extrapolate to the peak SPL levels once you know the maximum you amp can do.

So, to answer your actual questions, you either want a pair of speakers rated at about 100W RMS each or a single speaker rated at 2-300 Watts RMS if you use bridge mode.

Whether to go with one or two depends what you want to do and how much SPL you need.

For example, you might use the amp to drive a couple of small monitor wedges or maybe a single sub. The choice is yours.

Edited to add: I just had another look at your photo and I wonder if that amp has been modified by somebody. I don't recall the amp having those jack sockets on the front panel under the input gain knobs--and the fact that they're rusty makes me wonder if they're a real Peavey part. Either that, or it's an obscure sub model I don't know about. FYI, a theatre in the UK I worked at sometimes had CS800 and CS400 amps in their racks, the CS400s for monitors. My memory matches the manual link I posted.
 
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Bobbsy's spot on. There's nothing wrong with the CS Amps (I still have a CS1200 in my monitor rack) That speaker though is a different matter, it looks homemade and doesn't look loke it would have enough internal volume to suit even a low volume bass rig, I would look for a cheap 1x15 or 4x10 or 2x10 bass speaker you will have more luck. If the Graphic is in the signal chain for the speaker that would't help with the lows boosted like that the speaker wouldn't stand a chance....
 
I like the smiley faces on the graphic!

You ought to be pretty safe with speakers rated at around 100w. It seems a bit counter-intuitive, but amps generally need to be (as Bobbsy notes) up to two times the rated capacity of the speakers.

Interestingly, I drove a pair of 50 watt foldback wedges very successfully and trouble free for many years with a 700 watt amp.
 
Thanx for the help. The articles I have read about watts, ohm, rms, peak and such all got very complicated very fast. Thanx for the manual, big help, I am definately a read the instructions type. This gear was gotten in a trade deal. I on't like to have stuff laying around if I can put it to use.
 
Love the "rack". I'm not sure I've ever seen equipment nailed in before.
 
Just get two speakers rated for about 150W peak (about 75W RMS/program) and you'll be fine. Put one on each channel of the amp.
 
Whatever works. You should see around my house, I've done all kinds of strange shit to make repairs on a zero dollar budget. Drives my wife crazy. I tell her that she will appreciate my resourcefulness when the Apocalypse get here!!!
 
rockironwebb said:
Whatever works. You should see around my house, I've done all kinds of strange shit to make repairs on a zero dollar budget. Drives my wife crazy. I tell her that she will appreciate my resourcefulness when the Apocalypse get here!!!
Click to expand...

LOL, Don't worry, I've also made my own rack out of 2x4s.
 
gecko zzed said:
It seems a bit counter-intuitive, but amps generally need to be (as Bobbsy notes) up to two times the rated capacity of the speakers.
Click to expand...

The reasoning behind that thinking is that nothing is more destructive to a speaker than sending it a dirty, heavily clipping signal, not even more power than it is designed for. Even the way clipping destroys speakers is often more dire than over-powering them, literally tearing them apart. A clipping signal causes your ears to tell you "This sounds horrible, turn it up so we can hear it- maybe it will sound better," whereas an over-powered speaker says "Turn that shit DOWN, this sounds horrible." Don't ask me why your ears and brain react differently to both "horribles," I'm a psychologist, not a neurologist.
 
Except that clipped signals don't matter to speakers or drivers in guitar amps would never last more than a minute. There are two modes of speaker failure, thermal and mechanical. Thermal damage happens from too much power regardless of waveform. Mechanical damage comes from too much peak voltage.

But there is a psychological side to clipping. When you turn it up into clipping you don't hear as much increase in volume as you expect so you are tempted to turn it up more. An amp can easily deliver twice its rated power when clipped, at least until its protection kicks in. But that only happens if the amp is just a little small. If its rated power is a small fraction of the speaker's power rating then you can clip all day and not ever hurt the speaker.
 
Well, it's absolutely true that clipping in itself doesn't destroy speakers so long as the clipped signal is still at a power level the speaker can handle without thermal failure.

However, it can get a bit more complicated than that. Harmonics of clipped waves can mean a lot of extra energy up in the high frequency ranges that typically get sent into a tweeter; so it's fairly common for clipping at high volume to result in way too much power being sent into the tweeter, causing it to burn out.

So, basically, you have to beware of power levels AND clipping when matching amps and speakers!
 
Nice rack! LOL - Oh i remember those days fondly. Tip - Don't set your EQ like that. The smiley face is for your car/home stereo... not your band.

DO however, use your EQ to get rid of feedback. I wish someone would've told me this YEARS ago.

This equipment will barely be enough for you guys to hear the vocals, only because drums get nasty loud in your space. Nothing you can do about this. 'Treat' your room to help remove signals from bouncing around and causing feedback.

Ear plugs.. just sayin

For practice, you might consider a headphone preamp system. I'm thinking about getting one myself and they have one at MusiciansEnemy for about $200, AND it comes with 6 headphones. Granted, it's probably not the greatest, but everyone should be able to hear themselves and you'd save your hearing.
 
How 'bout a link to that headphone thingie, MrStitch?
 
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