Musician Gear & Tech Discussion

Ok so nothing is ever what one expects.

I'm getting that.. lol

So I am running 2 S215V's and 2 SV115IV's, ultimately.

The Yamaha S215V are 500/1000/2000 and the SV115IV are
250/500/1000. All pa cabs are 8 ohms impedance.

I'd like to use the S215's as mains and the other 2 sv115's as monitors.

I am drawing a blank as far as a power amp.
I was looking at the Crown that J7 left us a link for and that'd be great if I had 600$. (hehehaw, nope)

What I do have a choice of is;

Peavey PV 2000 or Yamaha P2250

Essentially they are the same price.
I have one guy in my ear saying that although it will not be full power, the Yamaha would be ok.
I have another saying that I need the Peavey PV2000, although that one is claiming that Peavey Power amp are crappy and cheaply made.

HELP, plz. I just use the equipment, I am not a technician, nor do I know much about PA's in general.

Note: both are used.. (big surprise there) lol

Suddenly I feel like Cliffy...

First, double check the rating plate on your S215V cabs. According to Yamaha spec sheet they carry 2-15" woofers and run @ 4 ohms. This is important to know.
http://www.yamahaproaudio.com/global/en ... ations.jsp

Second, running a stereo amp for mains and a mono amp for monitors works fine as long as you don't drop below min rated ohms. My rule of thumb is to run an amp that can carry one step lower load than I will need so I don't fry it.

If I plan to run 4 ohm cabs on both sides of a stereo amp I would get one rated for 2 ohm loads. If I only plan to run an 8 ohm load on each side, a 4 ohm rated amp will do. This way if a channel does go down, I "could" finish the gig with two speakers running on only one working channel. A little built in survivability and backup capacity when things go wrong.

Capt Im pretty sure those 2x15s are 4 ohm, I would lean toward the Yamaha power amp over the peavey just because it will match up with the speakers better.

Lets back up a minute, what mixer do you have? I remember you said it has power, plus you had another power amp?

List what gear you are trying to hook up, and maybe between Johnny and Me we can tell you how to run it.

Im only on here today and wont be back til monday, so If I dont respond its cause Im off line.

I went to the Yamaha site and couldnt find specs on the P 2250 power amp, that would be some good info to find.

I did learn that my 7000 series amp puts out 1100 watts per side at 4 ohms, do thats what we are putting into our S215 tops.

Capt I found a manual online of the P2250 power amp it produces 250 watts at 4 ohms perside.

I think it will work with the cabs you have, it will be a bit underpowered, but it should work.

Your speakers are 4 ohm, so when you hook up the P2250 it will recognize 4 ohms and thats the power it will put out to the speakers.

If you look on the back of the power amp, there should be a switch or you might have to cross some wires to wire the input in bridged mode, this way you can run one wire into input one and you will get a signal out of each side to the speakers.

Like I said put the info about what equip you are planning on hooking up and maybe we can help step you thru wiring it up.

Capt on the back of the power amp is a switch that says stereo or mono, switch it to the right in the mono mode, that way you can plug into channel A which on this amp will be to the right looking at the back panel, you will have output to both speakers at 4 ohm load there

Capt heres a link to the power amp specs

http://www2.yamaha.co.jp/manual/pdf/pa/ ... P2250E.pdf

Capt on the back of the power amp is a switch that says stereo or mono, switch it to the right in the mono mode, that way you can plug into channel A which on this amp will be to the right looking at the back panel, you will have output to both speakers at 4 ohm load there

Good catch on the owners manual JW. Looking at the specs, it will "just" power these speakers in stereo mode with 4 ohm loads per side.

In mono (bridged) mode the minimum rated load is 8 ohms, so trying to power a pair of 4 ohm speakers (4/2) would present a 2 ohm load to the bridged amp. This might be a recipe for power amp BBQ and a brief but spectacular light show back stage. Once you let the smoke out of a power amp it is difficult to put it back in.

Johnny I think Capt mentioned that he was just using the pa for the vocals, which it will probably work, but you mic a kick drum or try to line the bass in there, it probably wont work to well.

But just for vocals, it should do fine.

A 2 ohm load into an 8 ohm minimum bridged amp?? Since it would be Scotty's amp and not mine it would be fun to try it just to see what happens. I like testing and experimenting with gear. Yamaha overload protection is pretty good. It might shut the amp down in time.

LOL, Johnny Ive done some really stupid stuff in regards to gear over the years.

My drummer used to when we were in HS install car stereo speakers, and he would get boxes of those stock Delco speakers after he put in Jenson Tri-Axes, think that was the hot speaker.

Anyway, we had a practice room and one day we were sitting around and this box is sitting there, and he says I wonder what would happen if we hooked your guitar amp to these little speakers, so we did. I hooked up my SUNN MODEL T, which I still have by the way, so we would hook them up and I would play some big chord and the speakers would actually start smoking before they sizzled out. Made for a fun afternoon. I guess Im lucky doing that didnt damage my amp, should have toasted a transformer, but that amp still has the original one in it.

The worst pa mistake I remember is helping a friend with this big pa, he had two power amps, so I suggested we use one for each sub, I had hooked it up, but he in the past had been wiring the two subs together in line, and we made this loop that neither of us saw in time, wasted the amps, the speakers actually worked, but you can imgane a pair of power amps pushing into each other, what a mess.

If I think long enough I could remember all sorts of stories like this.


Last year we were hooking up our pa system, and for the gig we set the drummer out front, we are doing that again this weekend, anyway I took an extra monitor, so on the monitor send Im running 3 8 ohm cabs, well it didnt sound right, like the amp was clipping out, what we did was wire one speaker out of phase with the other two and it actuall was cancelling out each other, I didnt know what was going on, finally I looked at the inputs and switched one wire and it was working fine. Ive run into that recording, but its the first time I noticed it in a live situation.

Anyway live and learn, Im like you I love wiring up different things to see how they work.

Also, our pa, we have a pair of 1x18 subs, we were trying to run both off of a QSC 1450 amp, which just wasnt carrying any punch, I had an extra 1450 amp as a spare. So I bridged the inputs of the two amps together, so I could send one sub signal, then I bridged the speaker out puts from the specs the best I can rememeber we are putting something like 7-900 watts into each sub at 8 ohms. Man it really opened the bottom up, you dont even have to crank the low end but you get that gut punch out of the kick drum.

A 2 ohm load into an 8 ohm minimum bridged amp?? Since it would be Scotty's amp and not mine it would be fun to try it just to see what happens. I like testing and experimenting with gear. Yamaha overload protection is pretty good. It might shut the amp down in time.

Not sure i understand, but if you bridge the inputs you are still only seeing a 4 ohm load, now if you bridge the speaker outs and line the two subs together, you would be getting a 2 ohm load.

I personally wouldnt want to try that, 4ohms is about as low as I like to take a power amp.

A 2 ohm load into an 8 ohm minimum bridged amp?? Since it would be Scotty's amp and not mine it would be fun to try it just to see what happens. I like testing and experimenting with gear. Yamaha overload protection is pretty good. It might shut the amp down in time.

Not sure i understand, but if you bridge the inputs you are still only seeing a 4 ohm load, now if you bridge the speaker outs and line the two subs together, you would be getting a 2 ohm load.

I personally wouldn't want to try that, 4ohms is about as low as I like to take a power amp.

Maybe just a difference in terms John. Summing the inputs to mono doesn't change the output power at all but may result in better bass response due to the phase issues you mentioned. This is often used to run subs because you can't hear a stereo image below 150 hz anyways. The output is still a 2 channel amp at rated specs.

Amplifier bridging is a different technique that ties the output of two amp channels together. This effectively doubles the available voltage expressed in watts and halves the compatible minimum speaker load (typically from 4 to 8 ohms). I use bridging only when I need to get more power to a single 8 ohm sub for massive bottom. Bridging and then sending a signal to two speakers defeats the benefits and puts the amp at serious overload risk. With two speakers you always get better performance with two separate amp channels vs bridging. Getting amp bridging right requires careful math.

More on amps, wattage, ohms and speaker loads:
http://www.rocketroberts.com/techart/amp.htm

Thats it Johnny, on my QSC amps, I bridge the input of each input, then I just daisy chain the two amps together.

You are correct about bridgeing the outputs.

I send the sub signal to channel A of the first amp, then daisy chain the inputs together, then I bridge the output of the first amp and send the power of the whole amp to one speaker, then do the same with amp two.

So basically each amp is a mono amp driving one speaker each.

Does that make sense

It puts the amp at a 4 ohm load, whereas my sub speakers are rated 8 ohm, so out of a 1450 watt amp, I am getting somewhere in the neighborhood of 900 watts at 4 ohms out.

If I linked both speakers together in this configuration, then it would push the amp into a 2 ohm load, and be getting the full output wattage of the amp, around 1450 watts.

Our system works really well the way Ive had it set up, we actually were having to cut the top amp down so they matched up. these days I run the top amp in the 55-65% range and the sub amps in the 75% range and it all balances out.

Now you got my head swimming! LOL!

I worked all of this out on paper, per the amp specs before I did it, and consulted a sound guy I trust with it before I tryed it.

I knew we would get to the bottom of it sooner or later. Now I gotta go clean up to see Miss Bonnie Raitt do her stuff. Great seats!



Scotty, study all this stuff we blathered about carefully. There will be a test on Monday.