Hello All!
I built a small rig to play in a small outdoor area, but Im having a lil trouble with my QSC amplifier clipping out on the subwoofers, and it seems like Im not getting all of the wattage out of the this amp. Everything I bought used from FB, because I cant afford new. I play mostly House, R&B, and Disco. Heres the setup:
Mixer->EQ->Compressor->Crossover-> Each Amp.
Im aware I should put the EQ after the compressor, which might help quell some of the midrange, I still have to try that, but thats another story.
Subs are wired in parallel, I think its possible that the amp doesnt have enough wattage for these subs. It should but it doesnt act like it whether I use it bridged or stereo.
Amp sounds fine, but even after severely compressing/limiting the signal to even out bass peaks, I still get a clipping amp and popping out of one sub, and the output doesnt seem to be 1000 watts, and im testing in my house. (RIP my ears). The bass doesnt seem to have as much pressure as other systems Ive seen. BTW I did reverse polarity on one of the sub to make sure they werent out of phase, theyre not. I did alot of tuning with the compressor settings to get to this point. If I dont use the compressor, of course the amp clips much quicker.
So I said ok, Ill buy a Crown CE-2000. It should be 1950 watts bridged at 4 ohms, this should work right? Nope, its clipping out too at near max volume. I think this amp is one of their lower quality amps.
So now Im thinking I dont have nearly enough real power to drive these subs.
Does anyone have any suggestions as to if Im setting something up wrong, or which old heavy duty quality amp I should buy used to drive these subs?
Im having a hard time being able to figure out the quality used amps from the cheap ones on my own.
Right now, Im looking at pics of the interior of the amplifiers to see which ones are actually heavy duty vs the cheap ones. But Im not an electrician so its ignorant guessing. I know how to tell with Car Audio amps, but not with PA Amps.
I see huge transformers in pics of a Macro-Tech 2400 or Crest Audio CA9 that the MX-1500a or CE-2000 dont have.
I was also looking at a QSC PLX-3400 but Im not sure thats up to snuff either, but I can find it easily online.
What say you guys?
I built a small rig to play in a small outdoor area, but Im having a lil trouble with my QSC amplifier clipping out on the subwoofers, and it seems like Im not getting all of the wattage out of the this amp. Everything I bought used from FB, because I cant afford new. I play mostly House, R&B, and Disco. Heres the setup:
- QSC MX-1500a - used and rebuilt amp by QSC pro, connected to subs with banana plugs, bridged.
- Two homemade bass cabinets with one 18" Soundtown 8ohm sub each, around 450watts RMS, my closest guess is STLF-1804-8. 25 x 25 x 30.
- Two JBL G-734 15" tops
- Crown XLS-402 amp for the JBLs
- Rane EQ (Its flat except for lowered midrange)
- DBX 1066 compressor
- DBX 223XL crossover used in 2 way, crossover at around 120hz
- Mixer is Rane Seventy two
- BBE maximizer is on its way to help sweeten the sound.
Mixer->EQ->Compressor->Crossover-> Each Amp.
Im aware I should put the EQ after the compressor, which might help quell some of the midrange, I still have to try that, but thats another story.
Subs are wired in parallel, I think its possible that the amp doesnt have enough wattage for these subs. It should but it doesnt act like it whether I use it bridged or stereo.
Amp sounds fine, but even after severely compressing/limiting the signal to even out bass peaks, I still get a clipping amp and popping out of one sub, and the output doesnt seem to be 1000 watts, and im testing in my house. (RIP my ears). The bass doesnt seem to have as much pressure as other systems Ive seen. BTW I did reverse polarity on one of the sub to make sure they werent out of phase, theyre not. I did alot of tuning with the compressor settings to get to this point. If I dont use the compressor, of course the amp clips much quicker.
So I said ok, Ill buy a Crown CE-2000. It should be 1950 watts bridged at 4 ohms, this should work right? Nope, its clipping out too at near max volume. I think this amp is one of their lower quality amps.
So now Im thinking I dont have nearly enough real power to drive these subs.
Does anyone have any suggestions as to if Im setting something up wrong, or which old heavy duty quality amp I should buy used to drive these subs?
Im having a hard time being able to figure out the quality used amps from the cheap ones on my own.
Right now, Im looking at pics of the interior of the amplifiers to see which ones are actually heavy duty vs the cheap ones. But Im not an electrician so its ignorant guessing. I know how to tell with Car Audio amps, but not with PA Amps.
I see huge transformers in pics of a Macro-Tech 2400 or Crest Audio CA9 that the MX-1500a or CE-2000 dont have.
I was also looking at a QSC PLX-3400 but Im not sure thats up to snuff either, but I can find it easily online.
What say you guys?
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Yes both subs are connected across the red binding posts.
The amp was indeed plugged into the furman, I just plugged the furman into a separate plug and the QSC with the heavy duty cord into its own outlet. So far it still clips at the same levels but it doesnt pop the sub anymore. (I dont want to clip it harder to make the sub pop)
Link for the subs.
https://www.soundtown.com/products/stlf-1804-8
The amp was indeed plugged into the furman, I just plugged the furman into a separate plug and the QSC with the heavy duty cord into its own outlet. So far it still clips at the same levels but it doesnt pop the sub anymore. (I dont want to clip it harder to make the sub pop)
Link for the subs.
https://www.soundtown.com/products/stlf-1804-8
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are you doing any live sound?
if your simply DJ'ing ditch the comp.
use the crossover's high pass for the sub band.
the loudspeaker spec's are a load of pooh.
is your sub box designed by you or is it a published design?
and why is what seems to be your top cab set at back of the sub, is this an attempt at a mechanical means of time alignment?
don't dis the MX 1500's i used to power some Adamson double 18 subs with those and never had to worry about thump...
for your edification each channel has it's own transformer (so it's two mono blocks) which made it possible for the amp to fit into a two rack space form factor but their depth isn't Gator rack friendly.
lose the "my transformer is bigger than yours" thinking.
if your simply DJ'ing ditch the comp.
use the crossover's high pass for the sub band.
the loudspeaker spec's are a load of pooh.
is your sub box designed by you or is it a published design?
and why is what seems to be your top cab set at back of the sub, is this an attempt at a mechanical means of time alignment?
don't dis the MX 1500's i used to power some Adamson double 18 subs with those and never had to worry about thump...
for your edification each channel has it's own transformer (so it's two mono blocks) which made it possible for the amp to fit into a two rack space form factor but their depth isn't Gator rack friendly.
lose the "my transformer is bigger than yours" thinking.
It’s for djing. Well I have the comp because of the vast range of bass dynamics between the types of music I’m playing. Without the comp the amp peaks out on absolutely everything. It’s really helped a lot in terms of evening out the bass.
The boxes are a LaVoce design I found online.
The top cabinets keep sliding back due to the vibration, I need to put something on the sub to prevent that.
Currently the crossover point works well for the tops because those jbls don’t handle the sub bass too well.
The boxes are a LaVoce design I found online.
The top cabinets keep sliding back due to the vibration, I need to put something on the sub to prevent that.
Currently the crossover point works well for the tops because those jbls don’t handle the sub bass too well.
not to dis your efforts in DIY'ing your subs but there may still be some short comings there.
first thing i would do is find a ratchet strap to stop your tops from moving around, then i would have a play with the phase switches on your crossover.
at 120 hz even with 24 DB/octave filters improper phase can lose you a lot of bass and with improper position it only gets worse...
speaking of phase and position you do realize that even with proper polarity the physical distance between your stacks can create deep acoustic nulls...(i've seen far too many times nice amps being driven to the point of meltdown for this very reason!)
(id still lose or bypass the comp but that's me...)
first thing i would do is find a ratchet strap to stop your tops from moving around, then i would have a play with the phase switches on your crossover.
at 120 hz even with 24 DB/octave filters improper phase can lose you a lot of bass and with improper position it only gets worse...
speaking of phase and position you do realize that even with proper polarity the physical distance between your stacks can create deep acoustic nulls...(i've seen far too many times nice amps being driven to the point of meltdown for this very reason!)
(id still lose or bypass the comp but that's me...)
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I am aware of how the dead spots work between the speakers, I have the two subs setup right next to each other. (Not alot of space in my room to separate them). I was planning to keep them together when I got outside to avoid bass nulls.
Ill have a play with the phase switches on the crossover and bypassing the compressor and report back.
Ill have a play with the phase switches on the crossover and bypassing the compressor and report back.
Not a lot to go on with those specs.. was hoping to see TS parameters, but based on what the driver looks like and the response graphs I'd say don't expect miracles... you may alreay be finding it's mechanical limitations.
The thing with subs is... indoors in small rooms especially.. you're guaranteed to be generating cancellation nodes so it's hard to get a good idea of the actual performance you will see in bigger spaces. And that amp... while generally regarded an an oldie but goodie lacks some basic features that really help when driving subs, those features being clip limiters and a steep high pass filter. Is there a high pass filter on any gear you have? If so engage it because reflex subs are really easy to bottom below tuning... that could be the metallic popping sound you hear. As for the amplifier, an outboard analog limiter isn't really useful in preventing amp clipping... that requires an amp with that built-in, so you may be looking at replacing it with something that does.
Thats pretty much what I figured, the amp isnt built for this kind of duty. All I have separating the two amps is the crossover in the picture above, the sub is cut off at 120hz down to 40hz.
Do you have any suggestions on any older amps that I can buy used that would work for this?
I cant buy new and cant afford decent powered subs, thats why I went this route. As it is, this setup is worlds apart from the cheap amped subs I used to have.
Do you have any suggestions on any older amps that I can buy used that would work for this?
I cant buy new and cant afford decent powered subs, thats why I went this route. As it is, this setup is worlds apart from the cheap amped subs I used to have.
i'm still befuddled with the settings/ gain structure, why are the input gains on the crossover dimed when unity is at the 12 o'clock position?
(and why is there a difference between CH1 and CH2 on the MX)
the comp is set to make just about anything going through it come out like smashed bananas (as in no dynamics) not to mention the peak limiter isn't being utilized correctly
it does appear the 40hz high pass is engaged on that DBX x-over...
i guess my view point on the MX may be tainted by the fact that when i used those i had a BSS FDS 360 for a crossover and the limiters in those where awesome.
hum.. older amps to power subs, and this goes far back in time... i'd take an HH V800 mosfet!!
then an Ashley F2000 or Crest CA18
saying that an MX 1500 isn't built for bass duty is just...well...wrong!
(and why is there a difference between CH1 and CH2 on the MX)
the comp is set to make just about anything going through it come out like smashed bananas (as in no dynamics) not to mention the peak limiter isn't being utilized correctly
it does appear the 40hz high pass is engaged on that DBX x-over...
i guess my view point on the MX may be tainted by the fact that when i used those i had a BSS FDS 360 for a crossover and the limiters in those where awesome.
hum.. older amps to power subs, and this goes far back in time... i'd take an HH V800 mosfet!!
then an Ashley F2000 or Crest CA18
saying that an MX 1500 isn't built for bass duty is just...well...wrong!
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Yes the output was indeed smashed bananas, because the amp clips so often, so I was trying to even out the dynamics some. I hate it. I’ve been tweaking this for some time trying to figure out how to make it work like they have it in the roller rinks near me. They have heavy limiting on their signals to their amps because rink Dj’s are idiots and don’t watch levels. But they have better amps of course that have their own limiters. I figured out how to get the limiter to work, so I backed off the compressor a lot, which help to get me a lil more volume. It evens out the bass dynamics some as well, but not completely.
That’s why I was wondering if I just needed a more powerful amp that can handle the dynamics. Really I have to hear this outside so I can see if it’s good as is, I can’t possibly be hearing it right in my house.
That’s why I was wondering if I just needed a more powerful amp that can handle the dynamics. Really I have to hear this outside so I can see if it’s good as is, I can’t possibly be hearing it right in my house.
The newer QSC RMX series amps have clip limiters and high pass filters built in, look for one of the HD models if you want to run it bridged or one of the larger models to run 1 sub per channel. There are lots more that have these features too you just have to get into models from the '90's-00's.. I think that MX series is from the '80's. The DDT limiting in Peavey's CS series works very well, the Crest CA series are industry workhorses, I have a rack of Yamaha P series2 amps that are well behaved and recently picked up an EV Q1212 that performs very well. Most of these have non defeatable clip limiting, I think manufacturers learned that there really wasn't much point in having an option to turn it off because it just sounds awful when an amp is allowed to clip. To be clear clip limiting does not replace signal limiting, you really need both to get the most out of a system while keeping it alive and maintaining decent sound quality.
In my experience it doesn't matter how much subbage you bring DJs will always push it for all it's worth, you just have to put effective protection in place so they can't damage anything. This is where DSP speaker management excels, the inherent latency of the processing allows for look ahead logic that can actively track the input signal level and accomplish limiting without compressing the signal. Analog limiters always produce more signal compression which can actualy raise the threat of thermal overpowering of subs in particular, it works well enough if there is only occassional overdriving on peaks but DJs often just keep turning it up to where a system is in constant limiting.
In my experience it doesn't matter how much subbage you bring DJs will always push it for all it's worth, you just have to put effective protection in place so they can't damage anything. This is where DSP speaker management excels, the inherent latency of the processing allows for look ahead logic that can actively track the input signal level and accomplish limiting without compressing the signal. Analog limiters always produce more signal compression which can actualy raise the threat of thermal overpowering of subs in particular, it works well enough if there is only occassional overdriving on peaks but DJs often just keep turning it up to where a system is in constant limiting.
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Well I was considering picking up a drive rack pa2 just for the DSP and everything else it does all in one. Btw all this tweaking is just for me, no one else will be using my equipment. I just don’t want to have to keep my eye on the amp while I’m manipulating the bass controls for the different songs.
I’ll take note of all those amps you mentioned and start looking for them.
There is an RMX 2450 I found on FB, but I have to wait for the guy to get back to me. I shall see what else I can find. Thank you!!
I’ll take note of all those amps you mentioned and start looking for them.
There is an RMX 2450 I found on FB, but I have to wait for the guy to get back to me. I shall see what else I can find. Thank you!!
have you had the chance to investigate phase settings?
or looked at your gain structure?
i'm not sure why you want to limit bass dynamics that seems counterintuitive....
after looking at your driver spec's me thinks that your chosen driver needs a bigger box then what it's in.
or looked at your gain structure?
i'm not sure why you want to limit bass dynamics that seems counterintuitive....
after looking at your driver spec's me thinks that your chosen driver needs a bigger box then what it's in.
The MX1500 just isn’t that big an amplifier. And to me it sounds like even THAT is bottoming the driver (As well as clipping all the time). A bigger box will only encourage bottoming - hitting x-mech at lower frequency at lower watts. High pass at 50 or 60 and you might be able to survive with that rig.
Back in the day, we used to run CS800’s in constant clip and it never hurt anything - as long as the woofage was up to snuff. It’s about the same power as that QSC, but made to run at that power indefinitely. A CA18 would have torn the woofers of the day to shreds too. That one probably wouldn’t fare much better without a 60 Hz high pass, which doesn’t help a DJ create energy.
It took a stack of four lab horns, properly powered, to finally get over that “hump” where there really was enough rig to get what was expected, while not having it distorted as all hell and at constant risk of destruction.
Back in the day, we used to run CS800’s in constant clip and it never hurt anything - as long as the woofage was up to snuff. It’s about the same power as that QSC, but made to run at that power indefinitely. A CA18 would have torn the woofers of the day to shreds too. That one probably wouldn’t fare much better without a 60 Hz high pass, which doesn’t help a DJ create energy.
It took a stack of four lab horns, properly powered, to finally get over that “hump” where there really was enough rig to get what was expected, while not having it distorted as all hell and at constant risk of destruction.