• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Moving PA Sub to the Backline?

EdO.

EdO.

Jan 21, 2016
2,514
4,597
Podunk, Ks just slightly south of KC
#1
First off, apologies if this subject has been covered here before. Searched it but no useful results.

Quick back story - my BL recently purchased this JBL PRX718XLF 18" Powered Extended Low-Frequency Subwoofer Invalid Link Removed to replace two unpowered but similar JBL subs, and to match up with our powered JBL tops (12" with horn, not sure the model but they're fairly recent issue, powered as well). This new sub totally rocks, which it should with 1500 watts of onboard power, and the system as a whole sounds awesome in our practice space. Most of the places we play are small enough that we BELIEVE we can get away with just the one sub. BTW we run EVERYTHING through the PA (2 guitars, bass, 3 vocalists, kick drum and a mike on the hi-hat/snare area).

He did quite a bit of research before purchasing and has suggested that rather than placing one of the tops on a pole from the sub (which he says is a mistake anyway, something about frequency cancelation due to proximity?) and the other by itself opposite side of the stage on a stand, that we should place it on the backline as close to center stage as possible.

Now I'd never seen or heard of anyone doing that but the concept kinda makes sense. Case in point - I have a nice Boston Acoustics surround system in my living room. The sub is shoved back in a corner behind a recliner. With the system running the sub permeates the entire room and you honestly can't tell where it's physically located. So at least in theory this makes some sense to me.

My primary concern is that the sub will be directly behind me just a few feet, likely with my smallish combo amp on top of it (which is just basically a stage monitor for me anyway). Because of the frequency response of the sub (crossover setting 90 hz), the wavelength is long enough that it's gotta get out there a ways before it peaks SP wise so it may (or may not) not be too loud 6 - 8 feet in front of it to be an issue? We use in-ears for monitors too, but...

Basically I'd never heard of this and never heard this rationale for locating a PA sub center stage on the backline. Opinions?
 
#5
I did ad hoc sound for a band that had the sub at the back of the stage by the drums. I was struggling with low end feedback all night from the mics.

Lots of good info on how to configure subs fro FOH sound at ProSoundWeb LAB Lounge forums. I'd hazard a guess that most of them will think your BL is mildly FOS. Look into something called the "power alley".
 
  • Like
Reactions: Remyd, jumbodbassman, yodedude2 and 1 other person
#6
Sounds like your BL is wrong on about most PA related topics you mentioned above. :meh:

Tops have been over subs for decades without issue -even stacked directly on top, without poles.
Assuming appropriate crossover settings, "frequency cancellation to due proximity" is like saying "the hyperdrive is impacted by the orthogonal proximity of the flux capacitor!!" :)
If you want to have uncontrollable feedback all night, putting a sub on the backline - as part of the PA - is a good way to go.
There's a REASON the PA goes in FRONT of instruments, wedges, etc.
I HIGHLY recommend that you IGNORE your BL's recommendations.
If you want use that single 1500w sub, place it like you would normally with the top on a pole above it.. then put the other top on a pole on the other side - with no sub.
I've run my (tri-amp 4200w, with 1500w Yorky sub) PA like that for many, many club/bar gigs without issue.
 
  • Like
Reactions: EdO. and RoadRanger
#7
Thank you all for backing up my thinking on the subject, as I said I'd never heard this line of thought before either. I always thought the system was killer as was before with the passive subs/tops above. We're really going more for ease of setup (everything active), not so much trying to reduce our footprint on stage which really is reasonably small as is. Believe me or not my BL is actually a pretty sharp guy on most things sound related, honestly don't know where he came up with this idea.

Thanks @DirtDog for the info on the ProSoundWeb forum, I'll dig around for some more info to give him (as if I'm not busy enough already...).
 
Last edited:
  • Like
Reactions: DirtDog
#9
DWBass said:
Just a thought......he can stack the subs together. They don't have to be spread out. That's if he HAS to use the old sub. The single sub should be fine though.
Click to expand...

Whenever I use multiple subs I set them together. Exactly where depends on the room shape & orientation of the stage.

Sometimes I'll set 1 or 2 subs in front of the stage, & set a wedge on it/them. It frees up some space on the stage.
 
  • Like
Reactions: G RICH 5
#12
EdO. said:
For the record we're replacing 2 passive subs (and a rack box of power amps) with one powered sub.
Click to expand...
My bad. This is about placement of the new sub (sorry, I didn't read properly). No....I would not put it alongside backline. Put it out front and pole a main on top. Don't try reinventing the wheel. Tell your BL to cut it out!
 
Last edited:
  • Like
Reactions: EdO.
#15
The sub and the top must be in the same vertical plane. The reason they are always in front of the stage is because there is room, and then you set the PA delay 1ms per foot so the PA sound arrival in the house matches the drums or anything else back on the stage. If the sub gets placed at drum position, then just the tops get the delay. If the sub is behind the drums, you're SOL as you can't 'advance' the sub to match the drums.
 
Last edited:
#16
I have not played in that configuration, but I've seen a couple of bands working that way, and they sounded good. It makes some sense to me, I need the definition off of my amp, but not the real low. If I had the sub back by me, I could adjust the "mix" to my taste. Otherwise, I generally find subs to be a pain, I loose my pitch.
 
#17
Wherever you put the sub make sure everything except the bass and the kick drum are high-passed at 140hz or higher.

I recently played a date at a church where my amp was right beside one of the two house subs. The band was bass, drums, and three keyboards. The sub So loud that my amp was getting buried. During sound check I quit playing and even unplugged my bass. When the MD came over to ask me to turn down I told her I wasn't even playing, that the roar she was hearing was coming from the subs.
 
  • Like
Reactions: yodedude2, DirtDog and ashbory
#19
You can do this, but not exactly as described.

The subs should be clustered together and in the case of your bigger one, just use the one, without additional FOH subs (just put your mains on sticks). They should face the wall and ideally be in a corner where the speaker grill and corner form a triangle. This creates a pseudo horn and maximizes boundary reinforcement (the reason we like bass cabs to be sealed, ported, and close to floors and walls).
By facing the wall, there will be less direct radiation into the mics on stage. Depending on the size of the room, that one sub, in this position may be enough for the whole room, because it will probably shake the house :)
 
  • Like
Reactions: Kickass
#20
I'm no sound expert but I've played in a bar where the sub was at the side, near the band, and let me tell you that it totally messed up my sound. It just sounded all blurry, with no definition. I had to cut almost all the bass and cranck my mids up just to listen to what I was playing. The other times that we returned there, we simply unplugged the sub to be able to get a good sound.
That configuration might work in a DJ setting, but with bands, IMHO just forget it. Put the sub in the front with the rest of the P.A.
 
  • Like
Reactions: jumbodbassman

Latest posts

Top Bottom
Back