C7 stacking

[Rob]

I hired a C7 system (2 x sub & 1 x top per side) from a rental house recently, who recommend stacking the subs port to port, ie: one cabinet upside down.

 

I can't find any mention of this in the D&B documentation and I'm interested to know if anyone else does it this way and what the benefits are?

[RichH]

I'm interested to know if anyone else does it this way and what the benefits are?

 

Stacking port to port will create a coherent pressure wave and improve phase correlation.

 

In english , your bass notes will appear to come from once point, if the sources were spaced the sound waves would interfere - try tapping the surface of still water with your fingers a little apart, you will see the ripples interacting.

[benge]

I wouldn't have said you would have to turn upside down as low freq wave are vale big so they will tend to join together.... Its tweeters that really need to be next to each other..... Don't forget that Bass is omnidirectional.

 

 

Ben

[Mr.Si]

I have read many an article in good old L&Si where many system engineers etc have been trying to achieve equal bass/sub bass dispertion etc.

 

If one considers the Speed of sound to be 330m/s, then at 100Hz for instance, the wavelength would be 3.3m long and so depending on the room surfaces, dimensions etc, one can very likely get room modes.

 

Remember, every casestudy is different;

In my experience, one should experiment with different configurations and see which sounds best to you in the room that YOU are using. Walk around and see if you can detect any abnormalities etc.

 

 

Though having said this, it would be difficult to sense any directionality of the Low End because the wavelength is longer than the distance between your ears. (which is why bass/sub bass is "Essentially Omni-directional", along with other factors, which I shan't go into).

 

I Hope this makes sense.

 

Si

[andy_s]

I wouldn't have said you would have to turn upside down as low freq wave are vale big so they will tend to join together....  Its tweeters that really need to be next to each other..... Don't forget that Bass is omnidirectional.

 

 

Ben

<{POST_SNAPBACK}>

 

 

the "omnidirectional" characteristic of low frequency soundwaves is in fact a psychoacoustic effect - bass is just as directional as any other sound, but because the wavelengths are much bigger than the distance between your ears (which is what gives us the ability to distinguish "left" sounds from "right" sounds), we are not as able to distinguish its direction as we are the direction of higher frequencies.

 

In other words, a bass sound only comes from one direction, it's just that we are unable to tell what direction that is...

or so I understand it.

 

oops - didn't read the post above...apologies to the previous poster for nicking his theory....

[Mark Payne]

Ok, Stacking C7

 

First the wave length arguments above are on the money. You are going to get coherent coupling (+6dB) as the subs are well within 1/2 wavelength no matter how you stack them.

 

Please please please make sure they go on the floor and then you will half space couple them and get another load of SPL output for nothing. Often we are temped to pop them on the stage to get the tops higher (very good and very necessary) but if the stage is 1 to 1.5 m high then the floor reflections are probably out of phase with the subs and you will lobe your bass image in the venue (loud and quiet depending where you stand).

 

Sooo... find some other way of getting the tops up.....

 

Anyway IMHO .... Port to port the C7 sub goes more "woomp" (more towards a B2) and driver to driver they go more "donk" (more toward a C4 sub). Donk carries more bass guitar note and "woomp" carries more low end kick energy. Use 8 a side and they go "woomp" and "donk" at the same time and will take your bloody head off (well to be more precise, your head stays still and your body moves off!) ;-)

 

Want to to learn more about acoustics and speaker interaction?

Acoustic Training At Sound Foundation

 

Regards

 

Mark

 

BTW ... bass energy can be made directional. We just need big horns!

[Mark Payne]

Please please please make sure they go on the floor and then you will half space couple them and get another load of SPL output for nothing.

 

But I want to be clear... put the subs on the floor but build vertical stacks. Do not be tempted to put them side by side on the floor. One on top of the other..... OK?

 

Cheers

 

Mark

[Peter F]

BTW ... bass energy can be made directional. We just need big horns!

<{POST_SNAPBACK}>

 

Or the application of wave theory.

 

The Nexo cardioid subs are highly directional. Lots comes out of the front, not a lot from the rear. It's actually quite strange to be on stage with them running.

They are very effective.

 

You can "steer" low frequencies by applying wave theory. I'm not even going to attempt to explain in any detail, I'd tie myself in knots.

 

Put in very simplistic terms, it's all based on what happens when 2 subs interact. It's all about phase relationships.

 

A quick google for subs deploying them in the round, will send you to another place which tries to explain but might make it more confusing. (Warning, it might also lead to lots of messing about with subs, tape measures and trying to put them in inpractical places)

 

All the best,

Peter

(who is now worried about the can of worms he may have just opened)

[Mr.Si]

All the best,

Peter

(who is now worried about the can of worms he may have just opened)

<{POST_SNAPBACK}>

 

So You reckon you've opened a can of worms b talking about Wave theory?

 

As in the differences between Plane Waves and Spherical Waves?

 

Or was it something different?

[Mark Payne]

All the best,

Peter

(who is now worried about the can of worms he may have just opened)

<{POST_SNAPBACK}>

 

So You reckon you've opened a can of worms b talking about Wave theory?

 

As in the differences between Plane Waves and Spherical Waves?

 

Or was it something different?

<{POST_SNAPBACK}>

 

Hi Peter... Cardioid Sub Control... eveyone is doing it. d&b and Meyer for example. Nothing new. Nice and I like it. It uses more boxes (or speakers in the case of Meyer) and amps. Our subs are all too small and they do not control energy out the back ... so we we use more subs firing enery out the back on purpose .. out of phase with the "real" ones. "He swallowed a spider to catch the fly".

 

Hi Si... I think you mean Cylindrical Wavefronts (the pot of gold at the end of the line array rainbow) vs Spherical Wavefronts. Like line arrays, the pot of gold is highly overated and mainly misunderstood. The marketeers would have us believe that all curved rainbows come with the gold as standard but in fact... none of them do.

 

Cheers

 

Mark

[griffter]

Hi Mark,

 

Yes big fan of sub arrays we are starting to use the theory with our Meyer Subs

 

We'll see you at the next go-kart meet!

 

;)

 

 

Griff

 

Sound by Design

[andy_s]

Cardioid Sub Control... eveyone is doing it. d&b and Meyer for example. Nothing new. Nice and I like it.

Cheers

 

Mark

<{POST_SNAPBACK}>

 

 

I was very impressed by the cardioid sub demo at the d&b day at Central a few months ago - 3 stacked Q subs, with the middle one on a turntable so you could get a comparison between cardioid and "standard". v. clever.

Andy

[Brian]

BTW ... bass energy can be made directional. We just need big horns!

<{POST_SNAPBACK}>

Like these.

[Pete McCrea]

The second half of the Meyer Training day did quite a bit (in the second half of the day) regarding directional Sub and techniques that can be used to control the Sub. Very sensible, and to a point obvious stuff if you have a grasp of basic wave theories etc.

[IanG]

This thread on cardiod subs is one of the best forum threads I've read.