How much does orientation of sub cabinets matter?

L

Loren Jones

Sophomore
Jun 25, 2011
155
0
16
Hampton Roads VA
I am reluctant to post this for fear of exposing my considerable ignorance and inexperience, but here goes anyway.

How much difference should it make if the woofer and port on a direct radiating sub cabinet are pointing 90 degrees off to the side as opposed to firing straight forward. In this situation the subs are sitting in front of a 3.5 ft high solid wall at the front of the stage. Passband is 25hz to 80hz.

The reason I ask is that a musician member of our congregation asked me to try this out with our now groundstacked subs. Some members that sit toward the front of the room had been complaining that the bass impact was too much for them so this musician in the church begged me to try pointing them out to the sides to see if it lessened the impact at the front of the room. Well I humored him and sure enough in the first couple rows there was some noticeable decrease in the bass impact. I don't have good enough gear to reliably measure such a thing so I can only say that it subjectively did take some impact away in the front few rows. It didn't seem to create obvious adverse effects with overall coverage in the room. I wondered if most of the difference may be higher frequency stuff above the passband. The LPF is 24db/oct at 80hz but I am not sure of the topology.

So what disadvantages are there to such an implementation. It seems to me the only time I have heard of subs not pointing directly at the audience it is in the creation of multi-cabinet cardioid arrays etc. Just by way of background the subs have probably about 45 feet between them at their respective corners in front of the stage. The room is about 100 ft square with a 28 ft ceiling and has a couple pie shaped wings out to each side.

I am sure room effects predominate in this kind of a situation but I was just curious if there is any reason to absolutely not do this because it always does (fill in blank with undesireable effect that I am unaware of).

Thanks for always teaching me a ton,
Loren Jones
 
Re: How much does orientation of sub cabinets matter?

Welcome to the problem with subs on the floor-especially in a church setting. This is exactly why I prefer to fly them for these types of room.

Anyway-also consider the following. IF you were to lessen the punch by pointing them away from the audience-then the rest of the audience will ALSO get less punch.

Depending on the physical size (front area) of the cabinet, you may or may not have some directivity, that would change with the orientation of the driver.

But that directivity will be in the upper part of the passband.

Since all you are talking about is "twisting" them 90°, it is pretty easy to test.

I would also suggest doing some measurements (if you have the gear to do so) with a couple of mic positions out in the audience-in both positions.

Also do listening tests and see if they agree with the measured results.

If they do-great. If not, you need to reevaluate one or the other or both.

It is simple enough to try-so give it a go.

And don't forget the placebo effect. If somebody "thinks" it made a difference, then that part of the "problem" may just go away-thinking they have supplied a "solution".
 
Re: How much does orientation of sub cabinets matter?

Ivan Beaver said:
Welcome to the problem with subs on the floor-especially in a church setting. This is exactly why I prefer to fly them for these types of room.

Anyway-also consider the following. IF you were to lessen the punch by pointing them away from the audience-then the rest of the audience will ALSO get less punch.

Depending on the physical size (front area) of the cabinet, you may or may not have some directivity, that would change with the orientation of the driver.

But that directivity will be in the upper part of the passband.

Since all you are talking about is "twisting" them 90°, it is pretty easy to test.

I would also suggest doing some measurements (if you have the gear to do so) with a couple of mic positions out in the audience-in both positions.

Also do listening tests and see if they agree with the measured results.

If they do-great. If not, you need to reevaluate one or the other or both.

It is simple enough to try-so give it a go.

And don't forget the placebo effect. If somebody "thinks" it made a difference, then that part of the "problem" may just go away-thinking they have supplied a "solution".
Click to expand...

When we did the trial the other day I only had a couple minutes to mess around so I couldn't do much more than listen quickly while he changed the position then walk the room.

I will try to measure with what gear I have (iPad with StudioSix Audiotools RTA and SPL meters). I guess any inaccuracies in the mic etc would be equal between the two measurements. The cabinets are around 24" wide. The subs we already had are flown but they don't have much extension compared to these. I guess if these were placed on a steel platform that was flown in place of the old subs we could get the best of both worlds.

Probably need a pro with experience and gear to come help out but we will experiment and try to get the most satisfactory result ourselves. I doubted it would make any difference before we tried it but it did make some difference. I guess if it makes the level more even front to back then it is a net win.

Thanks,
Loren Jones
 
Re: How much does orientation of sub cabinets matter?

What I might recommend in this situation, given how much time I've spent in churches and having to deal with these very issues, is getting ahold of Meyer's MAPP program and working through some different scenarios within the program. Don't know if you have any CAD drawings of your church, but you can import .DXF files into the program and then do some calculations from there. It does a wonderful job of taking data and putting it in to an easy to understand image. Even if you can't set up exactly how your sanctuary looks, or don't use Meyer subs, it'll be able to show you how subs can behave being moved and pointed in different directions, and how they react in those situations. It's a great tool that people use on this site a whole heck of a lot. Just a thought.
 
Re: How much does orientation of sub cabinets matter?

Good idea. I should do that. I just put in my application through the Meyer website and will mess around with it assuming they grant me access to it.

Thanks,
Loren Jones
 
Re: How much does orientation of sub cabinets matter?

It takes about 1 business day. As this is a 3 day holiday in the US, it might be Tuesday before they approve you... but approval is a matter of course, usually.
 
Re: How much does orientation of sub cabinets matter?

I figured that might be the case but it is good to know that you don't' have to be an owner of a bunch of meyer gear or something. Its nice of them to make it available. It should be an interesting tool to play around with as we also work through some real world placement options. Then once we have it nailed down we will get some pockets built under the stage and set them permanently in place.
 
Re: How much does orientation of sub cabinets matter?

Loren Jones said:
Then once we have it nailed down we will get some pockets built under the stage and set them permanently in place.
Click to expand...
If you end up placing them under the stage-BE SURE to build a proper enclosure to put them in!!! Or you will be fighting a whole new set of problems.

Make enclosure just a little bit larger than the actual cabinet (allowing enough room to slide them in and get them out if needed-NOT and extra foot or two.

It is a good idea to plan on and stuff a little bit of foam (open cell is best to keep the vibration from being trasfered to the walls) around the sides and back to keep the cabinet from moving and touching the walls.

Be sure to use DOUBLE layer 5/8" sheet rock and glue and screw them together-no nails. Caulk with acoustical caulk (drywall mud can crack) ALL seams on each layer of sheetrock. Make sure the cormers are done oposite how the meet to help avoid leakage. ie on layer 1 walls go to the very top. Then the edge of the top butts into the wall. On layer 2 the top goes all the way to the side and the walls butt into the top.

Be sure to caulk the cable entrance into the cavity.
 
Re: How much does orientation of sub cabinets matter?

Thanks Ivan. It is an immense resource to get advice from folks like everyone here who have seen the pitfalls and had to fix them. When we get ready to make the final position choice we will follow your recommendations.

Thanks,
Loren Jones
 
Re: How much does orientation of sub cabinets matter?

He mentions screen shots but i'm not clear on where those are posted. Anybody know how to find them?
 
Re: How much does orientation of sub cabinets matter?

Drew, I don't have any images of impulse response alignment (since I basically only use the impulse response to look at rooms), but here is what Bob is talking about with phase alignment of subs. This is not too bad... outdoors at about 100' with center clustered subs. I had full control over both crossover points so I was able to choose phase compatible filters.

Screen shot 2011-09-13 at 4.55.22 PM.png
 
Re: How much does orientation of sub cabinets matter?

Thanks for the graphos. I'm curious that you didn't adjust your timing to view the phase in the crossover region (between subs and the rest of the system) in a more "flat" view? Also, it looks like you have a crossover issue in the other part of the system around 300?

drew
 
Re: How much does orientation of sub cabinets matter?

drew gandy said:
Thanks for the graphos. I'm curious that you didn't adjust your timing to view the phase in the crossover region (between subs and the rest of the system) in a more "flat" view? Also, it looks like you have a crossover issue in the other part of the system around 300?
Click to expand...

Sometimes I do, in this case this was unwrapped enough. If I were trying to do math to figure out how many degrees off one bandpass was from another I would definitely flatten it out. In this case I just added or subtracted a few orders of filter until the slopes were close and then used delay to line them up. The ends do justify the means!

The stuff going on at 300Hz is a ground bounce, I was only worrying about my mains/sub crossover so I didn't bother taking a wide-bandwidth measurement (and often don't).
 
Re: How much does orientation of sub cabinets matter?

Actually, that is a great example of using the data to answer a specific question, and not worrying about what is outside of your area of focus. Just because the display shows it doesn't mean you have to use it. If you were interested in 300 another mic position would probably give better results and make the sub crossover look lousy.


A measurement is meaningless unless it is taken within the context of a particular question. (I was actually talking about other examples of this in class today).
 
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