yep the PLX's are great amps, I'd highly recommend them.

Go for it. PLX amps are rock solid.

I also had good luck with the PLX.

She worked HARD for the money! Pushed a sub on one channel and tops on the other, never had a problem.

for a standard gig im gonna use it to power 2 18" macauleys 700w x 2 @ 8ohms

I was reading that in bridge mode it could do 3400w at 4omhs

If i wanted to connect 4 18" macauleys how would i do it? Do i just patch one speaker to the next? Is there a special way i have to connect them especially since i would be dropping the ohms from 8 to 4? I understand from a previous post that the sound quality is better at 8 but i just want to see how 4 would sound

I would also like to know the answer to this one as I have never really grasped how the ohm load changes when daisy chaining.

This is where that Yamaha Sound Reinforcement book would come in handy. Meister, where you at???

if those macauleys are 8ohm cabs...

to run 4 of those from one plx 3402, you can only run the amp in stereo mode, not bridged mono. connect 2 subs per channel. either piggybacking banana plug cables on each side, one cable per speaker....or daisy chain the speakers on each side. again, 2 speakers per channel.

... a simple way to look at it is this way when 'daisy chaining'

If you have 2 speakers that are 4 ohms each;
If connected in SERIES their total impendance would be 8 ohms
If connected in PARALLEL their total impendance will be 2 ohms

SERIES--------R1 + R2 ..... + Rx = Rtotal
PARALLEL-- 1/R1 + 1/R2 .....+ 1/Rx = 1/Rtotal

I own a PLX 3402 and it's SICK!!! Go for it!...

*Supernatural deer in headlights* LOL! Damn... I shouldn't have cut this class.

Im assuming there 8ohm because thats what weve been pushing them at for the past 10+ years

These are the specs of the amp
Stereo
700 @ 8
1100 @ 4
1700 @ 2

Bridged Mono
1400 @ 16
2200 @ 8
3400 @ 4

Would any of those configurations be able to push all 4 at the same time? I was hoping the 3400@4 would do it because i know each speaker can handl 800 each easily

Ok... since I used to teach electronics I'll give this a shot...

I'm not familiar with the speakers but will assume they have a pair of speakon connectors on the back.

When you connect multiple speakers together in parallel you are offering a LOWER total resistance because you have more paths for current flow. This concept is based on Ohm's Law. It's normally show as something called the magic circle but it can be shown as a series of equivilent formulas:

E=IxR
I=E/R
R=E/I

Where E is voltage, I is current, and R is resistance.

A common analogy is for voltage to represent the pressure in a water pipe (lbs/sq in), current to represent the amount of water flowing in the pipe (gal/min) and R to represent the back pressure offered by water driven devices (like electrical turbines).

The resistance laws are fairly basic and are shown a couple different ways and there are some shortcuts if the resistors are all the same value or if there are only two.

In a series circuit, each item in the chain has a voltage drop and gets ALL the current but only part of the voltage. All the water (current) would flow through both , but the pressure in the pipe (voltage) would be less after the first resistor because of the back pressure (resistance) of the first device).

----resistor1-----resistor2-------

To calculate the total resistance you would simply add the resistance of the devices up.

Total resistance=resistance1+resistance2
In a parallel circuit, each item gets all the voltage but only part of the current. (Imagine these tied together on each end). In this circuit both get all the pressure, but only half the water (assuming they offer equal back pressure or resistance). If one offered less back pressure (resistance) then MORE water would flow through that device (just like in electronics).


_|resistor1|____
-|resistor2|

To calculate the resistance above you have to add the reciprocals and then take the reciprocal.

1/Total resistance=1/resistance1 + 1/resistance2

there are some shortcuts though...

When you only have 2 resistors you can use this formula:
Total resistance=(resistance1 x resistance2)/(resistance1 + resistance2)

and if all the resistances are of the same value (no matter how many or how few resistors there are):
Total resistance = Resistance 1 / # of resistors


Ok, so why the electronics lesson?


When you connect resistors (speakers) in parallel you're reducing the resistance significantly. A pair of 8 ohm speakers connected in parallel offer only 4 ohms of resistance.

R=8/2 or 4

As you add speakers, you drop the voltage again...
R=8/3 = 2.67
R=8/4 = 2

So, if you simply take the first sub and connect a second cable to it from the first you create a four ohm load. The amp can handle a four ohm load on EACH channel so hooking up 4 speakers, with 2 on each side, would give you a 4 ohm load per side, w/ 1100 watts per side.

If you simply bridged the amp (and most speakon connectors require a specially wired 4 connector speakon connector on one end of the cable to do this) and connect ALL 4 speakers to one side you'll offer the amp a 2 ohm load, at a whopping smoking of the amp.

You COULD put 8 subs on the amp in STEREO though, 4 subs PER SIDE, offering a 2 ohm load per side with 1700 watts per side.

ALWAYS, ALWAYS, ALWAYS, do the math and check the results before hooking up more than one speaker to your amp - ESPECIALLY if you bridge it.


And if you check the bridged connections for speakon connectors you'll usually find they're wired to the two + connections which requires specially wiring up a speaker cable or making an adapter like I did for Julls. You'd wire up one end for the bridged mode and put a standard wired plug on the other to plug in a 'normal' speaker cable. Last I checked, Julls setup is running great... You can do the same for banana plugs (which are also usually wired to the two +'s for bridged mode.

I hope this electronics lesson helped someone.... and don't hook all the subs together on that amp! Cause if you do you'll wish you hadn't.

If you have more information on the connectors on the subs let me know what they are and if you need more information on how to hook them up.

BTW, I hope the above post is correct. I'm a little rusty since I haven't taught this stuff in a number of years and I didn't look up the formulas, etc.... If I was wrong, chalk it up to lortab and recent dental work!

You said dont hook up all the subs on that amp but earlier in your post you said i could do the 1100x2 @ 4ohms using 2 on each side?

The connectors on my 18's are 1/4" there are 2 connectors on each enclosure, i do have banana to 1/4" adaptors which i was using on my old amp in bridge mode which i plan to use on the PLX since it does have binding posts

Seems like a waste of power if i can only do the 2x700 @ 8ohms

Sorry, I should have clarified. You CAN do all 4 of the subs if you put only 2 on each side and DON'T bridge the amp. You can also bridge the amp and use ONLY 2 resulting in 3400watts for 2 subs.

Whatever you do, DON'T bridge the amp and use all 4 (or even 3) as the amp won't handle a 2 ohm load (or the 2.67 ohm load from using 3).

Basically, if you leave the amp in stereo mode and put a pair of subs on each side you CAN use all the subs.

You'll just need to use the 1/4" speaker wires (not guitar or mic cables, they're no where NEAR heavy enough) to hook the two together. Just come out of one speaker and plug into the second.

At 1100 watts per side, I'd go with a minimum of 14 guage and 12 guage speaker cable if you can find it. Especially if you're making runs of any appreciable length (more than 10'-15').

This means that with your existing equipment, the amp and 4 subs you do the following:

Stereo mode
speaker----amp------speaker
8Ohms per side, 700 watts per side

Stereo Mode
speaker--speaker--amp--speaker--speaker
4 Ohms per side, 1100watts per side

Bridged Mono Mode
speaker---amp
8 Ohms, 2200 watts

speaker---speaker---amp
4 Ohms, 3400 watts

Hope this all makes sense.... a little electronics math and theory goes a LONG way...

Thanks MMeister... I knew you'd come through!

Another warm recommendation for PLX 3402 from here too. My resident place runs their PA through two of those and they work rock solid! It recall they came with version 2 of PLX-series recently?

Yeah i heard that, the sound store here was making a big deal of the plx2 3602 saying sound quality wise its much better, I might just pick that up because its just $500 more, anybody use those?

This is true, but it's also dependant on the speaker's Ohms. If the subs are 8ohms each (like mosts are) you'll get different wattage than if the subs are 4 ohms each like some are.

Correct. I am assuming the subs are 8 Ohms each.

Hopefully you have enough information to compute the proper values if they're 4 Ohm or some other value.

I just installed a 3602 in one place (bridged mono at 4 ohms into a JBL dual 18" sub) and it seems to be working well. Definitely gives more punch than the Crest CA9 that was there before. My one issue so far is that the fan gets loud and makes a noise almost like a sine wave when the amp heats up.

I picked up a used plx today and tried it for 15minutes and so far im very happy with it, i also picked up a brand new crossover so that i could switch my system over from unbalanced to balanced using all XLR cables and it seems to me there was a spike in power with the Highs and lows, i havent tuned everything yet so maybe it just sounds louder because the settings are off. I have noticed that there is no longer a humming noise so thats a plus!

If you have a problem with humming pick up an EbTech Hum Eliminator. Fairly inexpensive and they rock....

anyone using QSC's second generation PLX amps?

Like I posted above, I installed a 3602 a few weeks ago. Aside from the fan being loud when the unit heats up, it's been working fine (driving subs in bridged mono).