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Bill Fitzmaurice Help me with my subs!

kringle77

kringle77

Supporting Member
Jul 30, 2004
8,880
4,290
49
Massena NY
#1
So, on the last few gigs I placed my pair of mackie s410s subs together in one spot. This should have improved low end and clarity with the bands pa. In all 3 clubs, the low end actually vanished. It sounded as though there were no subs at the all. The kick drum sound like a cardboard box. When I moved the subs to either sided of the stage, Presto! our punch was back. I was trying to do the right thing with the subs and it just didn't work at all. Im at a loss for this. I tried moving the crossover point from 150hz to 80hz, slighlty fanning the two subs out, then in. Nothing worked until I moved them apart. It was like they were 80% cancelling themselved out.
 
#3
Not wired out of phase but, if I didn't know better, I would have thought so myself. I just can't explain it. I gave the band guys a lot of flack for not trying to place the subs in the proper spots and when they actually went along with it, and it sucked 3 gigs in a row, it really hurt my credability.
 
#4
Are these subs new to you? I would check them with a 1.5v battery to be sure one isn't wired out of phase internally. Subs placed together 'should' couple and improve performance. I will be very interested to hear the answer.
 
#5
Like I've said, Im sure that they are in phase. I did the battery test. Even if one of the 8 drivers was out of phase, we shouldn't have experienced this kind of crappy performance. I'll have to check the speakon cables. Maybe one of the guys had to re-connect one of the ends when I wasn't around and accidentally reversed the leads on one end. I just thought of that, it could have happened since the guitarist sometimes uses the pa with a different band. hmm....
 
#6
kringle77 said:
So, on the last few gigs I placed my pair of mackie s410s subs together in one spot. This should have improved low end and clarity with the bands pa. In all 3 clubs, the low end actually vanished. It sounded as though there were no subs at the all. The kick drum sound like a cardboard box. When I moved the subs to either sided of the stage, Presto! our punch was back. I was trying to do the right thing with the subs and it just didn't work at all. Im at a loss for this. I tried moving the crossover point from 150hz to 80hz, slighlty fanning the two subs out, then in. Nothing worked until I moved them apart. It was like they were 80% cancelling themselved out.
Click to expand...

I think you're using the right medicine, but for the wrong problem. Putting subs together evens out the dispersion, eliminating hot spots and weak spots. Improved low end occurs when stacking horn-loaded subs, because you are creating a larger mouth area.

Were the subs wall-loaded (and thus twice as loud) when you split them? Try wall-loading both of them on the same side.
 
#7
They were not wall loaded. The subs aren't a horn design, just regular front loaded, front vented subs with four 10" drivers each. There is something going on. It was like the speakers weren't even on when they were next together. When seperated, it was night and day. The exact opposite of what should have happened. I'll have to check all of my speaker cables.
 
#8
every once in a while a poweramp that gets bridged from time to time will get one of the channels stuck in the out of phase position. try reversing the one of the cables on the poweramp or cab (hopefully you are using bannana jacks otherwise this requires rewiring)
 
#10
I use crown xti power amps and speakon cables. Tonight we are going to pull the gear out of the band trailer to battery test every speaker and check the wiring of every speakon plug. I've never heard of a power amp having phasing issues. It's good to learn something new everyday!
 
#11
Hey guys, while Im sorting out my pa issues, lets say that I wanted to set up my subs and tops together on one side of a small club to save space, rather than putting one top on the opposite side of the stage. Should I

A)fan the tops outward for better coverage
b)Face them both forward
c)Point them inward at about 40 degrees to crossfire them

How would this effect cancellation, dispersion, etc? I cross at 150hz.
 
#13
Well, I checked all the cables and speakers. Everything is as it should be. Another thought. I use a crown xti4000 bridged mono into the subs. A cable is run out of each of the two outputs into the subs rather than into one sub and daisey chaining to another. Is this the problem?

Our tops run are each fed with a seperate cable but, the tops amp is run in stereo. The only other thing might be that the xlr cable running from the sub out of the dbx driverack is wired out of phase.
 
#14
Just to be clear, sub clustering improves dispersion, not volume or clarity (unless using horns, which you aren't). Putting any sub against a wall will give you a 6db increase in lows. Corners will give you a 12db increase. Please note that direct radiator subs include a lot of harmonic distortion that fools the ear into thinking they are pumping out lows when they're pumping out mid-distortion (this is good news for people who want small subwoofers.) Ears are not sensitive to low frequencies, so the mids can give a false impression of actual output.

Crossing at 150hz puts directional sound into the subs, which you should avoid if possible. 100hz is the point where sound waves are considered omnidirectional. Putting your tops close together causes comb-filtering and limits dispersion (the purpose of stereo tops anyway). Whew, physics are unrelenting! If you had to put them together, aim them to cross-fire 90 degrees apart. Like an 'L'.

With subs, room interactions are very influential. If you could describe the room, it might give us a clue to the problem.
 
#15
kringle77 said:
Well, I checked all the cables and speakers. Everything is as it should be. Another thought. I use a crown xti4000 bridged mono into the subs. A cable is run out of each of the two outputs into the subs rather than into one sub and daisey chaining to another. Is this the problem?
Click to expand...

Yes, that is the problem.

One of two things is happening.

If you are actually using speakon connectors properly wired for bridged operation you are running cab 1 bridged, and not running cab 2 at all.

If you are using standard wired speakon cables you are actually running the amp in stereo with the polarity on channel 2 flipped.

I'm betting on scenario 2.
 
#16
Otter, thanks for the tip on the tops. As far as bridged amps, when the crown xti's are in bridged mode, I would have thought that I could use either output, I actually get sound out of both cabs but, placed together, they are cancelling each other badly. The speakons all are using +1 and -1 terminals. Thats it.

As I stated earlier, this was tried in 3 very different rooms with the same result. We are going to try running to one sub and then daisy chaining to the next at the upcoming gig on friday.

With the next pa that we are building, we're thinking about using a pair of 15" subs for 40hz-80hz, a second pair stacked on top for 80hz-160hz and then the tops (maybe a 12, 6 and horn) will cover 160hz to 20k. This sounds crazy but, we don't use stage amps and found through experimentation that without a speaker putting out low mids at torso level, we were not getting the punch to the body sensation that we wanted. Im sure that some of you have opinions on this and I'll glady listen to them. I feel that having a 6" in the tops will really make the guitar (with pod) sound much better as well as vocals.
 
#17
kringle77 said:
Otter, thanks for the tip on the tops. As far as bridged amps, when the crown xti's are in bridged mode, I would have thought that I could use either output, I actually get sound out of both cabs but, placed together, they are cancelling each other badly. The speakons all are using +1 and -1 terminals. Thats it.
Click to expand...

Your speaker cables are wired wrong for bridged operation. Bridged on that amp(and every Crown with speakon plugs off the top of my head) uses the 1+ and 2+ pins on the channel 1/2 output. The channel 2 output isn't used at all.

By hooking it up the way you are hooking it up you are effectively running the amp in parallel mono with the polarity flipped on channel 2. Not even effectively running it that way, that is literally, exactly what you are doing.
 
#18
Yup! I just found that out after going over the manual. We have been ruining our sub sound and not even knowing it. It still sounded pretty good actually. After I wire the cables correctly, this thing is going to hurt skinny chicks at the clubs.

So, I'll have to wire the connectors to 1+, 2+ on on the end of both sub cables? Can I then plug into the two outputs or do I have to use only channel 1 output and daisychain the subs? What it the speakon inputs on the subs are internally soldered pins 1+ to 2+ and 1- to 2- like the input plates on avatar cabs?
 
#19
I think that I've got it figured out. I'll have to wire the "amp" end of each sub cable 1+, 2+ and the "cab" end of each cab 1+, 1-. Does this sound right? I could then run parallel mono at 4 ohms, 3200 watts? Or would I still have to run out of channel 1 and daisychain?
 
#20
kringle77 said:
Yup! I just found that out after going over the manual. We have been ruining our sub sound and not even knowing it. It still sounded pretty good actually. After I wire the cables correctly, this thing is going to hurt skinny chicks at the clubs.

So, I'll have to wire the connectors to 1+, 2+ on on the end of both sub cables? Can I then plug into the two outputs or do I have to use only channel 1 output and daisychain the subs? What it the speakon inputs on the subs are internally soldered pins 1+ to 2+ and 1- to 2- like the input plates on avatar cabs?
Click to expand...

This is what you are actually doing: You connect the positive terminals of the speaker boxes to the hot(positive) side of channel 1, and the negative terminals of the speaker boxes to the hot(positive) side of channel 2. Then you send the same signal to both channels with the polarity flipped on channel 2. That's a bridged mono power amp.

With speakon plugs on modern amps you usually get two 4 pin output jacks. The first, which will be labeled 'Channel 1' or 'Channel 1/2' will be wired:

amp channel 1 positive -> pin 1+
amp channel 1 negative -> pin 1-
amp channel 2 positive -> pin 2+
amp channel 2 negative -> pin 2-

This can be used for just channel 1 with a two conductor cable wired 1+/1-, for both channels stereo using a 4 conductor cable, or for both channels bridged using a two conductor cable wired 1+/2+.

The second plug,usually labeled 'Channel 2', will be wired:

amp channel 2 positive -> pin 1+
amp channel 2 negative -> pin 1-

with the other 2 pins not going anywhere. All you can do with this is run channel 2 with a 2 conductor cable.

The other option is the banana plugs. From top to bottom(or left to right) the four terminals correspond to channel 1-/channel 1+/channel 2+/channel 2-. You use the top two terminals for channel 1, the bottom two terminals for channel 2 or the middle 2 terminals for bridged mono. No assembly required.

Anyway, the point is you want to get the positive side of channel 1 to the positive terminals on both speaker boxes, and you want to get the positive side of channel 2 to the negative terminals on both speaker boxes. Wire up whatever cabling solution is convenient. I like banana plugs.
 

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