Aux fed Powered sub

dezmoduo

Member
Messages
46
Last decade I sold off my triamp system in favor of my age and the smaller country gigs I do.
Our wonderful new lineup (drummer mostly), is asking for some thump.

We run 2 way 12's on stick and 4-16ohm floor monitors, vocs only,daisy'd,
off a Peavey IPR 1600, out of an old Mackie 16 or a new Peavey PV10 (fits in an attache case)

1. Can I simply aux feed (pre) the bass DI and his Kick into a powered sub with out a LPF?
2. There was another question I had but it died of loneliness.

I want to entertain his request but don't want to reinvent my sound gear. (again)
 

MLG Audio

Member
Messages
1,039
Aux fed subs definitely do help with the thump. You definitely want to run them post though. This way when you turn up the kick fader, it adjusts in the subs. Also make sure you get either a crossover to go between the aux out and the sub, or do what I do and use a 31 band graphic to kill everything above 125 going to the sub. This will give you a lot more headroom and allow the sub to really shine. If you want to get even more good sounding, use another 31 band to only send everything above 125 to the mains. This will allow the mains and subs to do their respective jobs more efficiently. You'll actually notice you get more volume and punch with less output from the mixer.

Hope this helps!
 

GCDEF

Silver Supporting Member
Messages
28,166
You can. The real advantage to aux fed subs is that you can control how much of each channel goes to the sub. It's nice, but not really necessary. It may be easier since your mixers don't have a lot of aux sends, just to hook up the subs to your main feed, and low cut the channels you don't want in the sub.
 

dezmoduo

Member
Messages
46
I can do this. I have an Alesis 2 X 31 sitting around.

As I read more, I'm getting a clearer picture of what I can accomplish with the gear I have on hand.



Dez
NYC
 

Crowder

Dang Twangler
Messages
19,072
A powered sub will have a low-pass filter built in. If you like to keep your rig small and light, you can probably skip the extra EQ. IMHO.
 

speakerjones

Member
Messages
2,299
Agreed. Most halfway decent powered subs have a built in crossover that will feed itself LF information and have a HPF out to go to the mains. I don't see much advantage to running aux fed subs in small systems such as this.
 

MLG Audio

Member
Messages
1,039
Agreed. Most halfway decent powered subs have a built in crossover that will feed itself LF information and have a HPF out to go to the mains. I don't see much advantage to running aux fed subs in small systems such as this.
I agree with you that the crossovers built into the powered stuff definitely helps with the signal. However, I have noticed that when I use the graphic eqs on my studiolive, when I cut everything below my crossover point, and only send what I want in the mains, I get a TON more headroom out of my amp. Sure there is a crossover built in, but you are still sending a full range signal to it, so if you are sending the kick drum signal to the amp, that still hits the amp pretty hot even before hitting the crossover. This can lead to clipping the amp at low output volumes.

Same when I cut out all the eq above 125ish going to my qsc powered subs. It gives me much more headroom to push the sub when needed without clipping it. Back when I was sending the full range signal to it, it would start clipping. I would think to myself, I know these subs push harder than that. After trying it out with the sub out using a graphic eq, my system sounded so much tighter and punchier.

On top of that, running the aux as post allows you to not have to play a balancing game with each low instrument channel having two outputs. This way when you turn up the kick drum fader, you are turning it up in the mains and subs. It sound much more natural than just turning up the low end in the subs. Same with the bass guitar, you retain more of the definition when you turn it up, because you are turning up the low end in the subs, and the upper mids in the mains.

Just some food for thought.
 

MLG Audio

Member
Messages
1,039
A powered sub will have a low-pass filter built in. If you like to keep your rig small and light, you can probably skip the extra EQ. IMHO.
If you want to keep it light then I agree with you. I just got lucky and have the 31's built right into my board.
 
Messages
1,013
Granted, it is nice to have a 1/3 octave on your mains for fine tuning and feedback control... but... I'm not sure I would recommend using extreme frequency dumping on a 1/3 octave EQ in place of a x-over... especially since most subs will have a crossover or lo-pass filter AND the IPR1600 has a 100 Hz hi-pass filter mode for your top cabinets. That's a good cutoff number for 12's too... Since your amp is doing double duty, that hi-pass would also serve you well to clean up your vocal monitor mix.

I've heard that extreme cutting or boosting on most graphic EQ's will result in some interaction with other frequencies and cause some phase anomalies. Besides, frequency dividing is the intended purpose of those features on the power amp and powered sub. They will do a better job.

In addition, I have an Alesis MEQ-230(assuming that is the EQ of which you speak). This is not a balanced in/out unit(potentially bad for noise) AND it doesn't seem to deal well with +4 level signals.... the headroom and sound quality are generally inferior for inserting into your FOH signal chain...
 

dezmoduo

Member
Messages
46
Maybe today between unloading the gear, prepping for Tuesday rehearsal, getting my clothes "magically" clean, and oh yes there's some sort of ball game that will require the Smithwicks from the fridge to disappear,
I'm going to make a list of the subs that fit our price/size and weight framework with a closer look at HPF specs.

I saw the 100Hz cutoff on the IPR amp and knew I could use that to power a passive sub. I'm focused on a powered unit (with a HPF out to main) so I can keep the power amp for mains and monitors without having to put the "Boat anchor" amps back into service.

QUESTION: (maybe the one I forgot from the 1st post). Is the ALTO product line something I should avoid? Size, weight, construction, price, fit the bill. It has an 80Hz HPF.

My Yamaha 2 way's are rated to 57 or 60 hz on the low end, so it could work. I'd rather 100hz and give the mains a little breathing room.

Thank you for your thoughtful discussion on the simple and well worn issue.

Dez
NYC


Granted, it is nice to have a 1/3 octave on your mains for fine tuning and feedback control... but... I'm not sure I would recommend using extreme frequency dumping on a 1/3 octave EQ in place of a x-over... especially since most subs will have a crossover or lo-pass filter AND the IPR1600 has a 100 Hz hi-pass filter mode for your top cabinets. That's a good cutoff number for 12's too... Since your amp is doing double duty, that hi-pass would also serve you well to clean up your vocal monitor mix.

I've heard that extreme cutting or boosting on most graphic EQ's will result in some interaction with other frequencies and cause some phase anomalies. Besides, frequency dividing is the intended purpose of those features on the power amp and powered sub. They will do a better job.

In addition, I have an Alesis MEQ-230(assuming that is the EQ of which you speak). This is not a balanced in/out unit(potentially bad for noise) AND it doesn't seem to deal well with +4 level signals.... the headroom and sound quality are generally inferior for inserting into your FOH signal chain...
 

GCDEF

Silver Supporting Member
Messages
28,166
QUESTION: (maybe the one I forgot from the 1st post). Is the ALTO product line something I should avoid? Size, weight, construction, price, fit the bill. It has an 80Hz HPF.
They're about the best you can do in their price range. Most people here seem happy with them, although I think you might find a 12" 300 watt sub underwhelming.
 

speakerjones

Member
Messages
2,299
Having used real subs for so many years, I find most of the consumer grade powered subs pretty lacking. The only ones I haven't detested for the most part are the QSC KW181 and the JBL PRX (XLF). However, you (and your drummer) might find something smaller will fit your needs alright, if all you want is to feel a little thump below the normal range of your tops. I just find those little 12" band pass "subs" to be very underwhelming.
 

MLG Audio

Member
Messages
1,039
The nice thing about the KW181 is that it has casters built right in (and no they don't rattle) and the cover has a hard top that goes over the grille so you can use it as a cart to get whatever else is too heavy to carry. I load my gigs in with each main sitting on each sub, as well as any random bags that might fit. It cuts down your trips out to the van or trailer by a lot.

And it's a killer sub to boot.
 
Messages
1,013
Maybe today between unloading the gear, prepping for Tuesday rehearsal, getting my clothes "magically" clean, and oh yes there's some sort of ball game that will require the Smithwicks from the fridge to disappear,
I'm going to make a list of the subs that fit our price/size and weight framework with a closer look at HPF specs.

I saw the 100Hz cutoff on the IPR amp and knew I could use that to power a passive sub. I'm focused on a powered unit (with a HPF out to main) so I can keep the power amp for mains and monitors without having to put the "Boat anchor" amps back into service.

QUESTION: (maybe the one I forgot from the 1st post). Is the ALTO product line something I should avoid? Size, weight, construction, price, fit the bill. It has an 80Hz HPF.

My Yamaha 2 way's are rated to 57 or 60 hz on the low end, so it could work. I'd rather 100hz and give the mains a little breathing room.

Thank you for your thoughtful discussion on the simple and well worn issue.

Dez
NYC
I understand the powered sub part...but if you go that route, then you have the option of using the 100Hz hi-pass on that power amp to keep the lows out of your tops.... and a vocals only monitor mix would benefit as well...
 

Crowder

Dang Twangler
Messages
19,072
I have a single JBL PRX 618 and it's plenty for our bar-band PA. I've just let the internal crossover handle things, and it's worked great so far. At the same time, the Aux fed sub thing has a ton of adherents so there must be something to it!
 

dezmoduo

Member
Messages
46
I have a single JBL PRX 618 and it's plenty for our bar-band PA. I've just let the internal crossover handle things, and it's worked great so far. At the same time, the Aux fed sub thing has a ton of adherents so there must be something to it!
Oddly enough the drummer has a Sx A 180. Granted it is old and never got much love but its in like new condition. It will never see the light of day though.
 

dporto

Member
Messages
760
"Oddly enough the drummer has a Sx A 180. Granted it is old and never got much love but its in like new condition. It will never see the light of day though."

And why is that?
 

dezmoduo

Member
Messages
46
Too heavy #1, too big #2. He's got a short bed pickup with a cap and his kit and cases & assorted bits fill it up.
I didn't want to pick "that" battle with a great drummer and focused and committed band mate.
He's willing to spend, I'm willing to cart. Considering transplanting the power amp/variable x-over from the sxa 180, into a passive 15 box. 650 watts class D. Haven't broached the subject, he's out of town this week.
 

TheoDog

Silver Supporting Member
Messages
19,922
IMHO, it is always an improvement to run aux fed subs if possible. True that powered subs will have a low pass built in, but that won't do much to clean up the tops with a high pass. So a crossover still makes good sense in this case. You certainly don't want to run the bass only through the sub, kick-maybe.
 

335guy

Member
Messages
5,228
RE: aux feeding subs with a small ( PV 10 ) mixer.

Since most small mixers have only one or two aux sends, why waste those on aux feeding subs? Here's how I approach the concept on mixers with minimal aux sends.

Since in most places, the FOH mix is in mono, there is no need to use stereo outs for the mains. Instead, designate one side ( either R or L ) to be the upper freq. ( highs ). If your crossover point is, say, 100 hz, then have one side of the stereo mixer out be the upper freq. and the other be the sub freq. With a stereo crossover ( like a DBX 223 xs ) run one out for the upper freq and the other out for the sub freq. Set the x-over point the same for both outs into the x-over. Of course, the sub output from the x-over goes to the powered sub or amp powering the sub, and the high ( upper freq ) go the the main FOH powered speakers ( or the amp powering the mains ).

Set up the mixer ( using L as mains and R as subs) and hard pan all the channels you do NOT want subs on to the left ( vocals, guitars, drum overheads, snare, etc. ). Then on the instrument you do want the subs on, start at 12 oclock on your individual channel pan control. At 12 oclock, you are feeding both mains and subs equally. Need more sub and less main on the kick ? Try setting pan control to 2 or 3 oclock. Also, the left and right master will control the global volume of each speaker system ( mains and subs ) allowing one to add more or less of either speaker system.

I use this set-up on the mixer on boards that have few aux sends so as to free up those sends for other uses ( monitoring and effects ). Prior to "aux feeding" the subs, my lows were not as clear and detailed. And some low cost, moderate mixers don't have individual high pass control on the channel strip, making aux feeding the sub/s even more helpful.
 




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