What is the "power-alley" in audio (Physics 1)

A brief look at the physics issue of "power alley" in sound systems.
The bass audio from sound systems become very prominent when the subs (loudspeakers) are placed too far to the left and right. The distance between the FOH speaker and the bass frequency they are producing, will cause a "power alley" of bass frequencies to occur down the middle of the guest area directly in front of the stage.
Please Note: The Power Alley is most prominent in outdoor events (due to no reflective surfaces). Power alley can exist for indoor shows, but may not be as prominent due to reflective surfaces causing interference.
The power alley is a physics issue that should be addressed when setting up a sound system. Minimizing the power alley ensures more guests will feel and hear the bass frequencies.
Conduct internet research on "power alley". Learn to recognize it and how to manage it.

[@randohinn6691]

Do you have a video like this for the cardioid sub method for reducing on-stage lows? I kinda grasp it but not fully...

[@stageleftaudio]

At this time, we do not have a video covering the cardioid setup. We've only needed to use a cardioid setup two times. However, I think there are other videos on KZbin covering how to set one up (setting polarity and delay). This type of video is on our radar to do, but we've been waiting for an event where it's actually needed so we can film an actual setup.

[@fernandobanda8287]

So if I have 4 sub boxed , 2 on each side wouldn't I be able to power thru ? And does it hurt my sub sound if I have 2 different sub cabinets on each side? Do I have to have the same type of cabinets ?

[@stageleftaudio]

Having 2 subs on each side of the stage will yield the same power-alley result. It's best to use the same speakers when combining them (same for subs as for mid/high). Using subs together that are not like each other most always causes issues with sound quality. Using unlike subs together could "hurt" the sound and cause issues when trying to correct the quality of the bass. You don't have to have the same type, but it is highly recommended. If you want to use 2 different sub cabinets, make sure they are all the same type with how they are producing sound. In other words, if you are using front loaded subs, make sure all subs are front-loaded, instead of some being front-loaded and the others "w" bins, or some are vented, and others are tuned-ported.

[@fernandobanda8287]

stageleftaudio ok so I have 1 pv b52 folded forn sub on each side and 1 pv sp 2x18 front mount sub box on each side also. So with the info u just gave me I cannot make that set up work? Cuz I always wondered y I couldn't get my bass to sound good even tho I have alot of power running them. So what do u suggest? I guess I need to purchase 2 more cabinets and get rid of 2 but which do I add or remove from my set up? Or how would I make that set up work?

[@fernandobanda8287]

I use this for DJ mostly but at times for small bands too

[@stageleftaudio]

Yes, to get it to sound right, you should remove either the folded horns or the front-loaded cabinets. The problem with mixing cabinets is that one type may require a different crossover setting (to get full benefit of the cabinet) compared to the other one. Sound quality between the cabinets is probably not equal. Phasing issues are very common when mixing cabinet types. Folded horn subs are ok, but can sometimes (depending on the model/make) sound somewhat narrow... i.e. lacking a good sounding bass. Front-loaded subs usually sound better; I think they acoustically sound better when producing musical peaks compared to folded horn. Something to think about when doubling up on the number of speaker cabinets (subs, or full-range, or mid-high), by adding 2 additional speakers (same type/model), will only get you a +3db of acoustical output. It's not much, but it can add some value to the overall "loudness" of the event.

[@stageleftaudio]

I'm sure the bands appreciate the subs!

[@user-kl4oh2co2y]

Great video, 1 question: Is FOH the place where the engineers sit with the sound tables?

[@isettech]

FOH is short for Front of House. Technically this is the main speakers for the audience to differentiate it from on stage Monitors. FOH mix is often done adjacent to the stage where it is not practical to set the engineer out front.

[@soulvibedisco4372]

What are your thoughts on a cardioid set-up (one on top of the other with one out of phase to the other)? What about two in the centre in this format?

[@stageleftaudio]

If there is room, I think (on a 2 speaker cardiod setup) it usually works best having the "reverse" sub on the floor (with the other sub) directly behind the FOH facing sub (set delay accordingly). A cardiod setup will also work by having one sub on top the other (cardioid on top); this setup will cancel frequencies, but it will not be as efficient as both subs on the ground (mentioned above). If you have a lot of subs and can run them across the front of the stage, then it's common to reverse one sub for every 2 subs facing forward. On this setup, the reverse sub would be placed between 2 forward facing subs (on a vertical sub setup).

[@guitarest3]

With two subs I always couple them on one side of the stage, simply doing that eliminates so many of the issues with bass. Google benefits of coupling your subs

[@fantazykory]

Would 8ft apart be good as well?

[@stageleftaudio]

Yes, that would reduce the power alley and give better coverage out front. Some people will place their subs directly next to each other at the center of the stage. This will completely remove the power alley and provide for an even coverage out front. However, sitting the subs next to each other will reduce the overall SPL out front, due to physics (but will provide for great coverage).

[@isettech]

I'm surprised you didn't cover the speaker pattern and orientation. Simply turning the speakers outward so the area of the power alley gets 1/2 power from each speaker will reduce this peak and as you move off center into the cancellation zones each side of center, you move into the power of one speaker and out of the power of the other resulting in minimal boost in the alley and minimal cancellation in the sides resulting in a wide coverage with few issues. See your speaker manuals for frequency vs power distribution. Use this to decide the orientation so the center of the power alley is at the speaker -3db roll off angle.

[@Mrav79]

I think in practice this would have little effect since bass frequencies are not propagated very directionally, e.g. you would probably have to turn them almost sideways so they would not interfere with each other.

[@stageleftaudio]

Most sub-cabinets are omni-directional in their coverage; basic re-orientation of the cabinets would not produce much difference. However, if the cabinets were more directional, the higher the produced frequency, (more a long the lines of mid to high-bass), moving them "off-axis" would probably yield a -3 db at the center coverage (depending on frequency).

[@Gxldxn95]

So what if I put 2 in the middle & 1 L & R?

[@stageleftaudio]

It depends on how far apart the L/R subs are. Though in general, 2 in the middle (with the L/R sub) would be beneficial for the overall FOH sound and bass coverage. There would be no actual power alley; the sub energy would be covering nearly all of the listening area out front, but also behind the subs. A side effect of that setup would result in bass cancellations on the immediate L and R side of the stage (at the plane of the speakers). This cancellation is usually ok because there's usually no one standing/watching a show from the immediate sides of the stage.