GX5 vs. PLX2 1804?

[drenwick]

Just wanted to get some feedback as to the following:

 

Got a QSC PLX2 1804 new in the box from GC for a very low price due to them making good on a foul-up on a previous transaction. It's still in the box and therefore exchangeable and I'm wondering if I'd be better off exchanging for a GX5 and having $300 store credit to put towards other needs.

 

I'll be using it to power my mains (2-JBL MR925s) so either amp appears to have ample power (too much according to some here).

 

I have no need for 2 ohm or bridging capability so the 1804 is fine there but along with the cheaper price, the GX5 seems to have some potentially useful features that the 1804 does not.

 

Is the PLX2 series that much higher quality to warrant the price?

[agedhorse]

Plenty of power, yes too much IMO in case of a accident.

 

Either would work fine, weight is the primary factor for your application.

[drenwick]

Thanks agedhorse. Regarding the power issue, I have read elsewhere (including from QSC and JBL, not just the dude at GC who sells amps) that the recommended power for a particular speaker is roughly it's "program" rating, or roughly twice it's "continuous" or RMS rating.

 

I have read your posts recommending at or slightly above a speaker's RMS rating. Having read a whole bunch of your posts here and finding them to be incredibly informative and well reasoned, I'm trying to rectify the difference of opinion. I tend to weigh your point of view rather heavily as having come from a lot of real world experience, of which I have very little.

 

I also, however, lean toward a higher powered amp with an eye towards upgrading speakers down the road. So that that moment doesn't come too soon , is there a fairly foolproof method of protection?

 

Also anyone else have an opinion GX5 vs. PLX2?

 

Thanks again for the input!

[soul-x]

I doubt you'll find too many folks with any experience with the GX5. It is very new.

[dboomer]

 

I have read elsewhere ... that the recommended power for a particular speaker is roughly it's "program" rating, or roughly twice it's "continuous" or RMS rating. I have read your posts recommending at or slightly above a speaker's RMS rating. Having read a whole bunch of your posts here and finding them to be incredibly informative and well reasoned, I'm trying to rectify the difference of opinion.

 

 

It's just a trade off. There is no single answer. It all depends;)

 

If you are looking for possible optimum performance from your speaker than you should use an amp that is rated roughly 2X the continuous rating of your speaker. This is that it is nearly impossible to ever drive an amp to it's full continuous power level using music as the source. It takes steady state tones (sine waves from a generator or similar to do it). Music will rarely ever drive an amp to much more than 1/3rd power.

 

Lets assume you (really) have a 100W speaker and a 100W amp. You'll probably drive the amp into it's clip limiter at about the time you reach 33W continuous output because music has peaks. If you were to use a 200W amp you'd likely still only reach about 60-70W before the limiter stepped in.

 

Here's where Andy's point comes into play. If you break into feedback (hey.. that's a sine wave), or have a problem in your mixer that spits out a big square wave or other mysterious problems ... in these cases you can develop too much power and burn things out.

 

It's always a trade off between performance quality and reliability that you must decide how to deal with. If you are careful and take reasonable precautions and can accept some risk then use the bigger amp. If not use the smaller amp. You're only talking about a potential of 3 dB output difference (which in the real world will be even smaller because of system losses). On the other hand you might be able to improve your system by a couple of dB by careful speaker placement, proper cabling and reasonable system operation.

 

This may help ... http://www.peavey.com/support/technotes/poweramps/HOW_MUCH_POWER.pdf

 

You also have to CLEARLY understand just what the specs of your equipment do and don't really mean. The same numbers don't mean the same to every manufacturer.

[witesol]

according to my friends at QSC the PLX is a more "professional concert grade amp", even though the power specs are similar. If you tend to work the amp really hard or in difficult situatuons with a lot counting on it, get the PLX or better yet the Powerlite. I own some PLX2 and do plan on getting a couple GX5s. I like how they can biamp right on the amp and that it has 1/4" and speakon combo outputs, which are handy for a lot of things I do year round.

[agedhorse]

There is also the fact that many speakers can't hold up to the mechanical damage caused by operating at such high powers. That's a whole different mechanism, and for example a subwoofer rated at 600 watts RMS can be damaged by driving it below the box tuning frequency with as little as maybe 200 watts, though there would be no thermal stress. All mechanical damage.

[Unalaska]

Tough choice, you have an amp not rated at 2ohms already, looking at an amp with same specs basically. One is made in china, the other in cali. Do you want the smallest house on the nicer street or nicest house on the not as nice street?

 

I'd love to get a pair of GX5's for monitor duty (but I like have everything 2ohm stable even if it doesn't get used). Anyone want to buy some behringer EP1500's?

[witesol]

thought I'd update this thread a little...

 

I went ahead and bought a GX5 amp for monitors to be used at a job I have that happends every Fri and Sat through Halloween. It's my C rig w/4 wedges. I used the GX5 Friday and again on Saturday. The amp will see pretty hard use, often out in the sun and heat of S. Ca all summer. We'll see how things hold up. The PLX2s have done great in that setup, as have the Yamaha P series that do my Mains. Yesterday it was almost 90 degrees.

 

Nice amp. The construction seems robust enough. Attractive and quality front and back panels. I like the different combos of inputs and outputs. It's even got RCA inputs. The outs are combo speakon/1/4". I could see this being a cool amp to have around for whatever pops up, or even for studio control room speaks. It's a bit heavier than the PLX2s obviously, but on par with the P3500 and lighter than the RMX it replaced.