So I bought the RMX 2450 ($200!!! What a steal), but Im still coming up with a similar result. I get a lil more volume, but its still clipping early. It has a clip limiter though so it doesnt make the speaker pop. I still should be waiting to see how this sounds outside. I did look at the spec of the sub, and if I calculated it right, it calls for 4 cubic feet. But my box is 9 cubic feet (still doesnt seem right). Also with the rack and the amp plugged into 2 different outlets, once I turn it up the lights on the rig start to dim with the bass hits. So they amp might be a lil starved for power.
I have a smaller set of sub boxes that Im going to switch the subs into and see how they do. The original subs in the smaller boxes are JBL, but they didnt sound like sub subs.
Turk I have tried changing some gain structure, but its still coming out the same. Although this amp handles the bass peaks better when the compressor is on bypass, thats for sure. Phase settings didnt do anything except knock down the dbs of the bass a lil.
WG SKI I havent tried lowering the crossover below 120, so I will try that as well.
I have a smaller set of sub boxes that Im going to switch the subs into and see how they do. The original subs in the smaller boxes are JBL, but they didnt sound like sub subs.
Turk I have tried changing some gain structure, but its still coming out the same. Although this amp handles the bass peaks better when the compressor is on bypass, thats for sure. Phase settings didnt do anything except knock down the dbs of the bass a lil.
WG SKI I havent tried lowering the crossover below 120, so I will try that as well.
ok i was wrong on box size and i was sure that loss of audible bass was a phase issue so go figure...stick with which ever setting gives you the most output... are all cables pinned correctly?
it may be that that driver isn't up to the task.
or as wg ski mentioned multiples of something better!
it may be that that driver isn't up to the task.
or as wg ski mentioned multiples of something better!
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The speaker is definitely not up to the task. If you’re dimming lights with an RMX2450 you are getting a decent amount of power. But as you’re finding out it’s still not enough.
That driver looks like a conventional old school 5 mm x-max woofer. The price is right for that, you can’t expect more. I ran into similar issues back when the best things I could get my hands on were the EVM18B and the predecessors of the Eminence Omega pro. With a stack of 8 of those I realized I was going nowhere, with the bass requirements of the 90’s. With only one or two, the Bingo hall and 50’s/60’s old folks music was about as rough a gig as it would safely do.
That driver looks like a conventional old school 5 mm x-max woofer. The price is right for that, you can’t expect more. I ran into similar issues back when the best things I could get my hands on were the EVM18B and the predecessors of the Eminence Omega pro. With a stack of 8 of those I realized I was going nowhere, with the bass requirements of the 90’s. With only one or two, the Bingo hall and 50’s/60’s old folks music was about as rough a gig as it would safely do.
Well its weird, I have JBL G-718 subs (Dinosaurs) I hooked those up to the amp, and I get the same result from the amp. Except the bass isnt as deep of course.
I guess the soundtowns just are horribly inefficient,but theyre supposed to be 98db in sensitivity? I guess its a lie.
Keep in mind, the sound is clean, but it definitely doesnt seem like Im getting anywhere near 2400 watts in volume. Like, the woofers are 450 rms each, and the amp isnt even threatening to blow them at high volume?
I did turn the compressor back on, and reduced the 63-100hz frequencies on the EQ, that helped to back down the kick thump that was peaking the amp and even out the different genres of bass. But of course I lose alot of useful bass that way.
I have the amp channel to 100% volume, the eq, compressor, and crossover gains all at 70%, my mixer main out and channel 1 is 100%, while channel trim is at 50%. I have been keeping the mixer channels out of the red. I know theres something simple Im missing in the whole setup.
The good news is, I can sell the MX-1500a on ebay (i have a great box that it came with) , sell the soundtown subs, and get better subs on ebay as well (Thank goodness for paypal 4 payment plan), its just a matter of which ones. Im going to hold off on that though until Im sure I need them.
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I havent considered this yet, I will do some wiggling and see if theres an issue. As far as I know all the cables are working correctly because theyre all new, but the components arent. I just remembered I ran into this issue when I got the EQ, where I had to fix the 1/4 input because the female didnt attach all three pins to the male. Maybe Ill switch around some wires and see if Im getting a loss somewhere.
Those speakers may be 98 dB sensitive, but not when putting 450W into one. More like 92. And at the price you can’t be getting much for excursion capability. If you got a hold of a pair of 18TBX100’s your jaw would probably drop to the floor comparing them.
The MX1500 would still be useful for tops or monitors. I’d use ‘em for 2” CDs - it’s about right. The MX2000 is the one that is comparable to the 2450.
The MX1500 would still be useful for tops or monitors. I’d use ‘em for 2” CDs - it’s about right. The MX2000 is the one that is comparable to the 2450.
While throwing around amp brand and model numbers for comparison, you must remember all this old used stuff is capable of underperforming in the old age. Early clipping due to tired high ESR capacitors is common in used equipment of a certain age. You need to make up a test jig to measure what voltage you are getting out, on what speaker impedance. You'll need a dvm to measure speaker resistance. Impedance is typically 1.33 * the dc resistance. Then you need some terminals to gain access to the wires to the speaker without risk of shorting out an amp. I use an analog voltmeter for a measurement. A simpson 266-xlpm. Cheap dvm produce random numbers on the AC scale on music. If you are extremely serious, an oscilloscope will show you exactly when the tops of the waveforms flatten off. Analog voltmeter reads direct, scope the rms is 70% of peak to peak voltage if you are looking at sine waves.
If is not just the rail caps that can cause wattage sag. I had a pair of Allen S-100 produce 2 watts on 4 ohms in itheir 27th year. New rail caps brought them back to 40 watts. It took a new bipolar electrolytic interstage coupler cap, 75 uf, to bring the units back to the 100 watts they were rated for.
P=V^2/Z where Z is impedance.
And don't forget to read the wall voltage while testing amps at maximum wattage. High resistance of the wire nuts in the wall can bring down the wall voltage from nominal 125 or 240 to much less.
If is not just the rail caps that can cause wattage sag. I had a pair of Allen S-100 produce 2 watts on 4 ohms in itheir 27th year. New rail caps brought them back to 40 watts. It took a new bipolar electrolytic interstage coupler cap, 75 uf, to bring the units back to the 100 watts they were rated for.
P=V^2/Z where Z is impedance.
And don't forget to read the wall voltage while testing amps at maximum wattage. High resistance of the wire nuts in the wall can bring down the wall voltage from nominal 125 or 240 to much less.
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The rail caps are what causes wattage sag on QSC’s. They’ve been known to use cheap caps, especially in the olden days of the 80’s. FP cans were often used - and those were about the worst in the world. They got better after the USA series - they had to to compete. Last QSCs I recapped were a pair of USA1310’s. They also have two critical caps on each channel - bypassing the shunt regulators that power the op amp front end. When they go bad (and they do) you will be limited to about +/-13 volts output. Not just ”low” on power - you get about 8 watts. Those caps are what holds the charge to power the op amp and supply base current to the driver/output stage when the “flying rails” aren’t supplying that power. That happens when the output goes above +/-13 volts or so. It’s what actually limits the short circuit current - the base current gets too high, caps drain, and output folds back. Short term overloads are tolerated, but longer term ones cause limiting.
Just my own experience over the past quarter of a century, but QSC amps have consistently been the most unreliable pieces of electronic equipment out of any brand I have ever used, and seemingly impossible to repair reliably.
I would never touch another one even if they were given to me - they would go straight into landfill since I wouldn't even give one to my own worst enemy.
My Behringer amps on the other hand have been absolutely flawless in the same period, not once having let me down.
I would never touch another one even if they were given to me - they would go straight into landfill since I wouldn't even give one to my own worst enemy.
My Behringer amps on the other hand have been absolutely flawless in the same period, not once having let me down.
I was told by the guy that refurbished my MX-1500a that the way these amps fail makes them unrepairable as a one-off. But he was doing them in mass (getting new boards) for AMC Theaters, so he was doing them on the regular, mine was one of the ones they didnt install before AMC closed a bunnch of theaters. Which Behringer do you use?
The cheap and mighty EP2500!
Never had one fail, nor an NU3000 I tested for a while. I dare say that most of Behringer's 'bad' reputation comes from folks who have never used them...
My 2500 kept developing intermittents in the wiring harness. That stupid ribbon cable. It’s the same circuit design as the RMX2450, but a more compact PCB layout and a 60Hz-only transformer to save a couple of pounds. Most of my QSC failures have been dried out caps, but the bias thermistors in both my USA1310’s corroded their way off the boards. They didn’t fail, but they ran hot due to overbias. Might have contributed to the cap fails, but I’ve seen enough dried out ones in older ones that it seems like a pattern. The only bad transistors I’ve ever replaced were mismatched junk that someone else got to first and never should have been in there. My rack of PLXs has been perfect, as well as both 2450’s and the 5050. I’ve got a GX5 that’s never given me any trouble but it’s life has been easy driving Selenium D3300 compression drivers exclusively.
Did you review the manual to make sure you have everything set correctly for bridged operation, the RMX series has some unique setup requirements with the DIP switches and controls
Where are you listening to this system... is it in your living room, a bedroom, a garage? How big is the space?
I've played in 2 churches that had ~20 year old RX-850, working fine. Date on schematic is 2/25/00. I bought a QSC CX302 from ebay last year; it came out of the box working fine. I have not done full power tests on any of them. Of course church PA does not run an amp very hard. I sing on mike at one such church, leaving the Baldwin piano I play acoustic. If I have any objection, the fans on QSC are noisier than equivalent Peavey products. Smaller heat sink too.
I intend to do a re-e-cap of the CX302 before donation if one of the RX-850's fails. 24 years certainly makes any switcher supply due. I've repaired younger Allen & Peavey switcher supplies, where a low voltage e-cap took out the +5 v of the switcher control (CS800s) or a shorted tantalum cap burned a NTC resistor of switcher (Allen). CX302 came apart pretty easily; on fixture for finish next winter. I've hung CX302 board vertically from a wooden frame so I can access both sides for cap replacement without touching the 200 VDC parts. I can power up and test the circuit safely after every 2 caps replaced, even though the swticher has deadly voltages. No need to put the case on for every function check.
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Oh yes. Also the back of the amp has very clear diagrams on how to set the switches. I even had to change the switches to run stereo operation when I tested the amp that way, results were the same. Theyre not complicated.
Space is small, probably 10 x 20 carpeted room that Im testing in.
Am I being punked? I just looked up the Behringer and it looks really similar to the QSC. Especially since the specs are similar.The cheap and mighty EP2500!
Never had one fail, nor an NU3000 I tested for a while. I dare say that most of Behringer's 'bad' reputation comes from folks who have never used them...
OK.. do something for me, while the system is playing go wander around to all the other rooms in the house... is there extreme bass happening anywhere? I suspect you will find there is, the reason behind this phenomena has to do with sound wavelengths at subbbass frequencies which make it difficult to get a real idea of the performance available. There is a complex interference pattern setup with rather large nodes created... areas with either summing or cancellation and if you happen to be listening in a cancellation node you will think the subs are ****, but if you move 10ft one way or the other you could experience the opposite node where all the wavelengths combine for mega bass.