Why do they do it ?

[badhabit]

Since manufacturers are well aware of the comb filtering aspects of subwoofers when placed, or spaced apart ( one or more on each side of a stage ), why do they put pole cups in them for the upper cabs and market them to be used that way ?

[dennis a]

There often isn't room to set them up any other way and it is one of those compromises you have to deal with...there are issues with any subwoofer set up and you have to choose the best compromise for your situation. Having a pole mount cup on a sub is more convenient than not having one and there is no down side as far as I know.

[JohnMCA72]

Why does anybody try to sell 2 units of something, instead of just 1? Do you really have to ask?

[twostone]

Time delays and phase reverse are your friends.

[badhabit]

I submit coupling (2) 1 x 18" subs together, both facing forward @ center stage will outperform the same two cabs placed at each side of the stage, regardless of where the uppers are placed. I understand that delay and phase reversal can help with lobing/comb filtering but how many regular bands in clubs actually use that? That would seem to be more of an option for larger concert rigs when multiple stacks and arrays of subs are used. And then, the pole mounts are not part of the equation. I'm using EV's quote of:

 

 

The best solution for lobing problems is to use a single center cluster instead of separate left-right stacks. This works for both horizontal and vertical arrays.

 

 

to suggest that performers using (2) subs would get better performance from their subs by placing them together @ front center of the stage and mount their mid/upper cabs on stands at the sides of the stage, rather than using the subs on each side and mounting the mid/upper cabs on a pole attached to the sub. While that may be more convenient ( sorta of ), IF one has a stage approx. 2' + off the floor, two single 18" subs would not get in the way nor detract visually. One could even use that center sub "platform" for one or two monitor wedges. Anyway, something to consider when setting up the subs at your next gig.

[Bugzie]

Bottom line is that the footprint of a sub is still a lot smaller than that of a speaker stand, and a lot less likely to get knocked over!

[Mogwix]

Since manufacturers are well aware of the comb filtering aspects of subwoofers when placed, or spaced apart ( one or more on each side of a stage ), why do they put pole cups in them for the upper cabs and market them to be used that way ?

Because comb filtering in it's nature isn't necessarily a bad thing. I've built and set up a lot of PA systems and a very small percentage of them feature a center-cluster of subwoofers. There are a lot of cases where a center cluster isn't feasible, such as a low stage, small dance floor, or perhaps a narrow room with the stage on a far end. The power alley created by a spaced set of subwoofers is desirable in many cases, and is the most simple method for controlling low end in the room. Sometimes you only want low end on the dance floor, not off to the sides where people are trying to eat or order drinks at the bar.

 

Having a pair of tops on poles over a pair of subs is the most simple system of getting the most predictable response that is both aesthetically pleasing and space saving, in many small rooms.

 

We can talk all we want about the advantages of having a clear, even coverage of low end around the room with a center-cluster of subs; but how we position them is only one variable. Not every room is perfect, and a lot of times the "solution" creates more problems that are even more difficult to solve.

[monkeyland]

 

Bottom line is that the footprint of a sub is still a lot smaller than that of a speaker stand, and a lot less likely to get knocked over!

 

 

this

 

also at a lot of the places that I play there is really no stage to speak of, and if there is it is very low to the ground. I center cluster if I can but it's the exception rather than the norm. sometimes i'll group both of my subs off to one side, especially if there is a wall right there, but often it's best to just use them as a nice secure base for the tops.

 

I'd rather have the pole mounts than not.

 

What really bothers me is the idea of a pole cup instead of letting the pole go all the way to the bottom of the cabinet. My Peavey SP subs do this and it seems much more stable than many of the other options that I've seen.

[agedhorse]

Why? Because usually it works quite well, and the comb filtering effect is negligable for the most part.

[Coaster]

this has been discussed ad naseum and has been proven that it depends. there can be situations were center cluster sucks balls, especially if done wrong.

 

sometimes i center cluster, sometimes i sidestack. its all based on varying criteria, including visual aspects and room characteristics/audience layout (and experimentation/experience in a room)

[jasps]

 

I submit coupling (2) 1 x 18" subs together, both facing forward @ center stage will outperform the same two cabs placed at each side of the stage, regardless of where the uppers are placed. I understand that delay and phase reversal can help with lobing/comb filtering but how many regular bands in clubs actually use that? That would seem to be more of an option for larger concert rigs when multiple stacks and arrays of subs are used. And then, the pole mounts are not part of the equation.

 

 

If you aren't flying your speakers, it makes sense to stack the tops on your subs. Also, if you have a center cluster of subs, how do you align the crossover between the L and R stacks? Maybe it isn't an issue where you work, but there is more to consider than simple wavelength addition between subs; the acoustic crossover is actually "kind of a big deal." You get 6dB SPL of addition in the sub bandpass...great. What about the patron who doesn't hear the "A" on the bass guitar all night due to crossover deficiencies?

 

Live sound is all about compromises--you've got to know what is important to your customer and how you are going to accomplish satisfying their needs.

 

Also, room nodes can be drastic on subwoofer response...so though you have a point about the coupling of subs together outperforming spaced subs outside, the spaced subs may actually yield better coverage inside some rooms.

 

Best.

[badhabit]

 

Also, if you have a center cluster of subs, how do you align the crossover between the L and R stacks? Maybe it isn't an issue where you work, but there is more to consider than simple wavelength addition between subs; the acoustic crossover is actually "kind of a big deal." You get 6dB SPL of addition in the sub bandpass...great. What about the patron who doesn't hear the "A" on the bass guitar all night due to crossover deficiencies?

 

 

Okay, not sure exactly what you're referring to here. I'm no sound engineer and was simply attempting to understand what EV and other manufacturers say re: lobing and comb filtering of subs. As far as alignment, my FOH is run mono with aux subs. The same crossover point is selected for the uppers and subs: 100 hz. The R & L receive the same signal and in fact, run off the same amp channel. Same with the subs: both run off the same amp channel.

 

And all you other guys, thanks for your most knowledgeable comments. It appears I took too much of EV's statement to heart and over estimated the advantage of center clustered subs. Much obliged.

[jasps]

 

Okay, not sure exactly what you're referring to here. I'm no sound engineer and was simply attempting to understand what EV and other manufacturers say re: lobing and comb filtering of subs. As far as alignment, my FOH is run mono with aux subs. The same crossover point is selected for the uppers and subs: 100 hz. The R & L receive the same signal and in fact, run off the same amp channel. Same with the subs: both run off the same amp channel. And all you other guys, thanks for your most knowledgeable comments. It appears I took too much of EV's statement to heart and over estimated the advantage of center clustered subs. Much obliged.

 

 

What I am getting at is that your electrical 100 Hz crossover may not be the actual acoustic crossover of your system.

 

If you have your subs separated from your stacks, you will have crossover cancellations where the wavelength between LF and subs has more than 120* of difference. The cancellations (and additions) will be determined by the relative distance of the listener between the system as a whole and is influenced by the polarity, level and delay through the various crossover points. The effects of this may not be noticeable if setup well or can be severely detrimental to the LF response.

 

Anytime you add physical distance between bandpass crossovers such as clustering subs, you are making a decision to tradeoff a 6dB increase in LF level for problems elsewhere in your system. Those potential crossover problems may be worth the tradeoff or may not be. That is why it depends. Know your performance goals first, identify problems, identify remedies and the compromises inherent in your solution and move on. Best of luck, use your ears, and have a good day!