QSC PLX Amps

[thumbsup]

wish i was more eletronicly inclined but i'm a Draftmans/Designer/Bass Player/Bass Fisherman and me and wires do not get along and when i try to figure wires out my brain fries!
I depend on club members for advice and i now have some more stupid questions!*#!
 
I am in the process of putting myself together another bi amp bass rig. I have currently discussed this with club members and have decided I definetly want a SF2 pre amp.
I have already desided to get a QSC amp because i have used them in past with no problems. While researcing QSC i found the following specs:
 
Two ways to get PLX2 performance
The 02 models (PLX1802, PLX2502, PLX3102 and PLX3602) are the right choice for users who need to drive up to four loudspeakers from each amplifier channel (2 ohm loading), or when extremely high power bridge mono operation is required. These models feature built-in subwoofer processing, filter switches, and front panel indications of bridge mono status.  
 
The compact 04 models (PLX1104, PLX1804) bring the same performance and technology, plus even greater value, to applications that don't require bridged or 2 ohm operation. Designed to power one or two speakers from each amplifier channel (4 ohm minimum loading), these models offer a simplified feature set while retaining genuine, uncompromised PLX performance and technology. Weighing just 13 pounds (5.9 kg) these plug-and-play amplifiers are perfect for ultra-portable rigs, as well as reference-quality playback.  
 
So now i still do not understand the difference between the 02 & 04. Would i want to use for example a 2402 or 2404 model?
 
Thanks   Steve

[dfung60]

Without being specifically familiar with QCS stuff, the 02 models are more conservatively designed and intended to be more reliable.  The 04 models are lighter and less expensive.
 
When you increase the power output of an amp, it will draw more electrical current from it's power supply and it will dissipate more heat.  You strain the amps much harder when you have a low impedance load, which usually comes from multiple speakers.  When you see descriptions of the amps like these, it implies that the power supply and cooling of the 02 models is superior.  If you're not playing super loud, then the 04 might work out fine.  If you're driving the amp hard, then maybe the 02 is better.  
 
One difference that I noticed on the spec page at QSC is that it looks like when the 02 is being overloaded it goes to a reduced power state before shutting down the output (this lets the amp cool down).  The 04 looks like it will probably shut down entirely when overloaded, then stay off until the amp has cooled sufficiently.
 
David Fung

[edwin]

I used to use a PLX2402 and while it was a big upgrade from my previous Mackie FR1400, it was ultimately disappointing. The final straw was when I put it in my home studio, swapping it out for a McIntosh 2105, thinking that the newer technology and higher power would provide increased fidelity. How wrong I was. It sounded really terrible in that context, very 2 dimensional and sort of cardboardy.
 
Since then I've used a Crest CA9 and then very much more recently (actually, since yesterday) a Crown XTI4000. Both provide an obviously better bass tone than I got from the QSC. The QSC got loud, but it never had the punch that I thought it should have had. I've had people tell me I'm out to lunch on this, but I would seriously listen to and compare other amps before you make a final decision.
 
Best bass power amps I've played through:
1. McIntosh 2105, the downside is a lack of power with reasonably sized cabinets. It weighs a ton.
2. Crest 7001
3. Crest 5001
4. Crest CA9, the downside of all three is that they weigh a ton!
 
I'm pretty happy with the Crown after last night's gig. I think it's a good compromise between weight and tone. It's definitely punchier and deeper than my old PLX. I'm still not sold on the DSP thing, but it's bypassable.

[charles_holmes]

I can't really compare anything to my QSC 2450 since I have not taken the time to do so.
I would really like to hear the Crown XTI40000 though. My 2450's have provided me lots of power and clarity, but I have never used it in a studio setting so I can't comment on the aspect of fidelity/power/clarity.In addition I have never owned the QSC PLX series to compare and contrast either. But it (2450) really works for me as it did for Stanley, but I understand that Stan has forged a deal with Ampeg?.Please correct me if im wrong. I just know that my QSC 2450's really satisfy my aural pallette!! So my advice is to go listen to the power amps you are considering along with whatever you are using (cabinets/bass) and decide for yourself..go with your instincts and good luck!!!!

[bigredbass]

I've never been much good at hearing the difference in power amps, though I'm sure there is some.
 
I'd think the first two questions I'd ask are
 
1) So . . . are you just gonna run two cabs or four?
 
2) How much weight are you willing to drag around?  Power amps these days range from balsa wood weight all the way up to MacIntosh, which can weigh more than a Smart car.
 
There's a big diff between packing
 
1) say, a single 15 cab and a single 10/12/210 and a rack bag, versus . . . .
 
2) A pair of 18's, several 210's, and a flight case rack.
 
Then, I'd feel better pointing you in a direction.
 
J o e y

[thumbsup]

Joey....
Here are the cabs I currently have:
2 single Sound Tec 18s
1 single Dietz 2-15
1 single Mesa 1-15
2 single Mesa 4-10s
 
I plan on bi amping a single Mesa 15 cab and a single Mesa 4-10 cab.
Alternate rig would be bi amping a single Dietz 2-15 cab and a single Mesa 4 - 10 cab.
 
I have in past mostly used a single mono amp with a single Mesa 4-10 cab with the cab raised which worked well in most venues I played including small outdoor gigs.
Since I intend to start playing more I like the abilities of bi amping. Just a little more control of the balance.
 
I have never used the 18s. Pose I could use a single for the low end? The Sound Tec cabs are way lighter the the Mesa or Diets cabs.
 
I use both my 5 string & 6 string Alembic and the low B and high C get hit in almost all tunes.
 
Steve

[charles_holmes]

Hey Steve,
To give you an Idea of what I use which sounds similar to the amount of cabinets you have at your disposal....
Go to Showcase then to Distillate Then Chalie's Distillate..then Scroll to the end to view my newly updated rig Maybe that will help you too, because I usually use 4 cabinets on my gigs (two:18's & two:2x10's). I use two QSC 2450's (one for the 18's and one for the two 2x10's) and two F1X's (one for treble and one for bass).

[bigredbass]

After a quick trip through the QSC website page for PLX's, the -02 amps are passing more current (as many as 4 cabs with a total impedance of 2 ohms) plus built-in 'hard' 100hz subwoofer crossover, defeatable limiters, subsonic (below 33hz) hard filter.  Plus they are full rack depth and obviously heavier and more expensive.
 
The -04's delete the filters, limiter, and will load down to 4 ohms total per side, and evidently they are suggesting no more than two cabinets to get to that 4 ohms, so it's passing less current.
 
My next three questions would be:
 
1) What's the impedance (ohm rating) of the cabinets you listed above?  The answer to this alone may answer your question.  And, WHICH Mesa 410's and single 15?
 
2) Where is your crossover?  The SF-2 can function as a preamp, but there are better choices (F1-X ! !), then running the SF-2 through effects loop or inline.  The SuperFilter is amazing, but it contains no crossover, so you CAN'T biamp thru it alone.
 
3) Why not use a power amp with the Mesa 410s running one to each channel?  An f1x/sf2/QSC rig run like that would be PLENTY clean and loud without hassling with biamping, and you could use the less expensive -04 amps to boot.
 
J o e y

[bigredbass]

PS:
 
I forgot to agree with David Fung, so:  I agree.  The 02's are heavier duty, never a bad thing.
 
And, after living with several biamp rigs, I am NO fan of biamping with bass guitar cabinets, and this is why:
 
In professional touring sound reinforcement, people like EAW or Meyer or JBL design the massive 3- and 4-way systems to work as a whole
system.  You don't see them mixing and matching cabinets at a whim.
 
All of the cabinets you list above (and this could be said of virtually anybody's bass cabs with a few exceptions) are all designed as full range, stand alone cabinets.  So they don't tend to function well as a biamp rig.  The available crossovers are generic, trying to work as well as they can with whatever they're presented with (and I'm sure the f1x would work better than most, considering the ears that designed it).
 
You're suggesting using some single 18 subs from club PA duty (the SoundTecs) or some 15 cabs that were designed as full range bins.  You might get lucky, or it may sound just fine to you, but it really is sonic roulette.
 
One of the few dedicated sub systems I CAN think of for bass guitar are the Bag End ELF rigs (no longer called ELF, but it's too late to remember their new name), but these are VERY specialist rigs, but they certainly work well.
 
Enough rambling . . . .
 
J o e y

[edwin]

Joey, you aren't rambling. I agree with you completely. it's very important to have a system that is designed from top to bottom. I'd love to hear Chalie's rig. I think Bag End does a great job of integrating their systems. I've messed with mismatched rigs for quite some time and sometimes I get lucky but in most cases it never quite matches up to what I expect.
 
These days I'm very happy using the fEARful 15/6/1 cab from Talkbass. It's finally dissuaded me from feeling like I need to biamp. Some people do biamp them but they also sound great full range (the crossover is much more like an extremely heavy duty hifi crossover than a typical bass cabinet).  
 
But at the end of the day, Chalie's advice is the best, listen and decide for yourself!

[thumbsup]

Hum...I mis spoke (wrote) my original post. I had decided to use the F1-X not the SF-2 because of the cross over for bi amping.
However after reviewing the comments I am reconsidering.  
 
I believe I like the ideal of running a seperate channel to each cab. Although I only have one 4-10 cab available because I am using the other 4-10 for my Yamaha EX5 Keys. I can use the 1-15 as an alternate though (right)  I will check impedance on both cabs and get back to you.
So if I do the above..I actually would not have to use a F1-X and could use an F2-B instead(right)?
 
Charles would probably sell me his F2-B for a couple hundred  
Steve
 
(Message edited by thumbsup on January 18, 2011)
 
(Message edited by thumbsup on January 18, 2011)

[bigredbass]

Right, the f2b is a stereo (or dual channel) preamp.  The f1x replaces one channel with a crossover.
 
I'd use the single 15 for the keys, and run a matched set of the 410s, one to each channel of the QSC, but that's me.  I like eliminating all the variables I can.
 
Best of Luck,  
 
J o e y

[5sicks]

Unless you are playing a BIG stage or do not have a FOH sub & top system to go thru, all you need is one full-range source. The single source design is the clearest, most accurate and simplest solution. Using more than one cab will present an acoustic nastiness called comb filtering where the pulses from one cab intersect and distort with the interaction of the pulses from the other cab. Very precise, steep (24db or more) crossover devices (read Expensive) can mitigate this phenomenon but why go thru all the heartburn when a single full-range cab can give you all the clarity you crave. I use a Ciare 800 watt 15 with a Sound Pipe HF compression driver in a Geoffrey cab of my own design. I use a EPX 3000 amp and one of several preamps. I play a poor man's Alembic with active Bartolinis and my rig plays loud enough to keep ahead of a Marshall half-stack and a Line-6 Bogner tube combo for guitars. My sound coming out of my speaker is exactly what I put in. The Eminence drivers used in most 1-15 and 4-10 cabs just don't have the bandwidth or SPL to reproduce low frequencies at high volume levels intelligibly, so we think more cabs is the answer when really all more cabs do is confuse the sound waves and create distortion.

[edwin]

Thomas, there is a lot of truth in what you say. This is one of the concepts behind the fEARful cabinet. The way the drivers are aligned and crossed over is driven by their dispersion characteristics so that the off axis sound is very consistent and is as close to a point source as possible. When doubling up the cabinets, it's designed so that the mids and highs couple together to reduce comb filtering. I've only used one so far, but I'm sold on this concept.  
 
I will say that it's not worth condemning the whole Eminence line. The 3015LF that this cabinet uses has great abilities in xmax and power handling as well as linearity in its desired frequency range. However, you are correct in that drivers of this ability are rarely used in stock cabinets and Eminence makes a lot of drivers where the cost benefit ratio leans more to the cost side.

[charles_holmes]

I sold my SF a few months ago..sorry